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Research Article
New Macrocheles species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America
expand article infoWayne Knee
‡ Agriculture and Agri-Food Canada, Ottawa, Canada
Open Access

Abstract

Burying beetles (Silphidae, Nicrophorus) are hosts to a broad diversity of mites (Acari), including several species of Macrocheles Latreille, 1829 (Mesostigmata, Macrochelidae). The macrochelid fauna associated with silphids primarily in North America was surveyed; in total, 1659 macrochelids representing seven species were collected from 112 Nicrophorus beetles representing nine host species. Three new species of Macrocheles were discovered during the survey and described as Macrocheles willowae sp. n., M. pratum sp. n., and M. kaiju sp. n. The barcode region of cytochrome oxidase subunit I (COI) was amplified from the three new described species, as well as M. nataliae and M. praedafimetorum, and analysed in a small phylogeny.

Keywords

Acari , carrion-feeding, COI, ecology, mite, phoresy

Introduction

Carrion-feeding beetles (Silphidae) are associated with a diverse assemblage of mites, nematodes, and fungi. Nicrophorus (Silphidae) species are large-bodied beetles, that breed and feed on decaying organic matter, most often vertebrate carcasses (Anderson and Peck 1985). There are at least 60 extant species of Nicrophorus worldwide, 22 of which occur in the New World (Sikes et al. 2008, Sikes et al. 2016). Nicrophorus beetles are unique amongst insects because most species provide biparental care and they bury small vertebrate carcasses in subterranean crypts (see Anderson and Peck (1985) for a summary of their life cycle). Nicrophorus beetles are associated with a broad diversity of mites that can occur at high prevalences and abundances, with at least 14 species of mites representing four families collected off 95% of beetles in a given population (Wilson and Knollenberg 1987). The symbiotic relationship between silphids and their associated mites are poorly understood; however, the relationship may be a blend of commensalism and mutualism, as some mite species actively prey on eggs of carrion-feeding flies that compete with Nicrophorus (Wilson and Knollenberg 1987).

The Macrochelidae (Mesostigmata) are a cosmopolitan family of predaceous mites with at least 480 described species from 20 genera, occurring in a wide variety of organic substrates where they feed on nematodes and other microinvertebrates (Krantz 1998, Lindquist et al. 2009, Emberson 2010). There are about 320 described species of Macrocheles Latreille, 1829 (Macrochelidae) worldwide (Emberson 2010), many of which are phoretic as adult females on insects, including nine species which are associated with silphids (M. agilis, M. glaber, M. kurosai, M. lisae, M. merdarius, M. muscaedomesticae, M. nataliae, M. praedafimetorum, M. vespillo) (Halliday 2000, Mašán 2003, Niogret et al. 2007, Perotti and Braig 2009). Macrocheles associated with silphids attach with their chelicerae to beetles dispersing to and from carcasses, and they generally feed on nematodes, insect eggs and larvae, and other invertebrates on carrion (Wilson and Knollenberg 1987, Schwarz et al. 1998). Macrochelids phoretic on burying beetles are often overlooked and unstudied, resulting in a scarcity of information about their life history and novel species that remain to be described. A recent survey of tortoise mites (Uropodina, Uroobovella) on Nicrophorus beetles (Knee et al. 2012) also uncovered three new species of Macrocheles associated with burying beetles. Herein, I propose and describe Macrocheles willowae sp. n., M. pratum sp. n., and M. kaiju sp. n., include a small phylogeny based on the barcode region of COI, and describe the diversity, abundance and host range of Macrocheles species found on Nicrophorus throughout this survey.

Methods

Biological collections

Silphids were collected by various researchers across eight countries and 21 provinces or states (see acknowledgments). In Canada, most silphids were collected as bycatch from xylophagous beetle trapping by W.K. Specimens from other countries were collected primarily in pitfall traps, and others were hand-collected. Beetle specimens preserved in ethanol were shipped to Carleton University, and upon receipt specimens were placed in 95% ethanol and stored at -20°C. Using a dissecting microscope, silphids were identified to species using keys from Anderson and Peck (1985). The presence, abundance, and attachment location of mesostigmatic mites was recorded. All mesostigmatic mites were removed and placed in a 0.5 ml microfuge tube with 95% ethanol and stored at -20°C for later identification and/or molecular analysis. Mites were slide-mounted in polyvinyl alcohol medium (6371A, BioQuip Products, Rancho Dominguez, California, United States of America (USA)) and cured on a slide warmer at 40°C for 3–4 days. Slide-mounted specimens were examined using a compound microscope (Leica DM 2500) with differential interference contrast illumination (DIC), and identified to species using the primary literature. Initial drawings of mites were made with pencil on paper using a camera lucida. Illustrations were later merged in Adobe Photoshop CS5 and redrawn in Adobe Illustrator CS5 using an Intuos 3 Graphics Tablet from WACOM Co., Ltd. (Saitama, Japan). Leg chaetotaxy is based on the system proposed by Evans (1963) and Evans and Till (1965). Idiosomal chaetotaxy follows the system of Lindquist and Evans (1965) as applied to macrochelids by Hyatt and Emberson (1988). Notation for glandular openings and poroids (proprioreceptors or lyrifissures) follows the system developed by Athias-Henriot (1969, 1971, 1975) and Johnston and Moraza (1991), as reviewed by Kazemi et al. (2014). Measurements were made from at least eight female specimens, all measurements are in micrometres (µm), and lengths presented with mean followed by the range in parenthesis. Type specimens are deposited in the Canadian National Collection of Insects, Arachnids, and Nematodes (CNC), at Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada, and the Smithsonian Institution National Museum of Natural History.

Molecular methods

Genomic DNA was extracted from whole specimens for 24 hours using a DNeasy Tissue kit (Qiagen, Inc., Santa Clara, California, USA). Following extraction, mites were removed from the extraction buffer, vouchers were-slide mounted, and genomic DNA was purified following the DNeasy Tissue kit protocol. PCR amplifications were performed in a total volume of 25 µl, with 14.7 µl ddH2O, 2.5 µl 10× ExTaq buffer, 0.65 µl 25 mM MgCl2, 1.0 µl of each 10 µM primer, 2.0 µl 10 mM dNTPs, 0.15 µl ExTaq DNA polymerase, and 3 µl genomic DNA template. Primer pairs LCO1490 + HCO2198 (Folmer et al. 1994) were used to amplify a 689 bp fragment of the 5’–end of COI. PCR amplification was performed on an Eppendorf ep Gradient S Mastercycler (Eppendorf AG, Hamburg, Germany), using the following protocol: initial denaturation cycle at 94 °C for 3 min, followed by 45 cycles of 94 °C for 45 s, primer annealing at 45 °C for 45 s, 72 °C for 1 min, and a final extension at 72 °C for 5 min. Amplified products and negative controls were visualized on 1% agarose electrophoresis gels, and purified using pre-cast E-Gel CloneWell 0.8% SYBR Safe agarose gels (Invitrogen, Carlsbad, California, USA). Sequencing reactions followed the protocol of Knee et al. (2012), and sequencing was performed at the Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre Core Sequencing Facility (Ottawa, Ontario, Canada).

Sequence chromatograms were edited and contiguous sequences were assembled using Sequencher v5.3 (Gene Codes Corp., Ann Arbor, Michigan, USA). COI sequences were aligned manually in Mesquite v3.10 (Maddison and Maddison, 2016) according to the translated amino acid sequence. COI sequences from Macrocheles subbadius (MBIOE1677-13, MBIOE1699-13) generated by the Barcode of Life Data Systems (BOLD) were included in the phylogeny. COI sequences on GenBank from two Macronyssidae (Mesostigmata) species, Ornithonyssus bacoti and O. sylviarum (FM179677, KR103486), were used as outgroup sequences. Sequences generated during this study have been submitted to GenBank (Table 1).

Table 1.

Collection information, host species records and mite abundance of Macrocheles (Macro.) mites collected from Nicrophorus (Nicro.) beetles, with GenBank accession numbers for COI.

Beetle number Beetle species Collection location Coordinates Collection date Macrocheles species Mite abundance GenBank number
N002 Nicro. defodiens CAN, ON, Algonquin P.P. 2 45.895, -78.071 16.vi.08 Macro. willowae sp. n. 1
N003 Nicro. defodiens CAN, ON, Algonquin P.P. 2 45.895, -78.071 16.vi.08 Macro. willowae sp. n. 1
N005 Nicro. orbicollis CAN, ON, Frontenac 44.447, -76.577 17.vi.08 Macro. willowae sp. n. 4
N006 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 17.vi.08 Macro. willowae sp. n. 4
N007 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 17.vi.08 Macro. willowae sp. n. 1
N008 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 17.vi.08 Macro. willowae sp. n. 1
N011 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 2
N012 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 2
N013 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 5
N014 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 7
N015 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 5
N017 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 1
N018 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 2
N019 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 2
N020 Nicro. orbicollis CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 4
N021 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 1
N022 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 3
N023 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 2
N024 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 16.vi.08 Macro. willowae sp. n. 3
N026 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 01.vii.08 Macro. willowae sp. n. 5
N028 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 3
N029 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 4
N031 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 2
N036 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 1
N037 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 3
N039 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 1
N040 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 8
N042 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 3
N043 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 3
N044 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 3
N046 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 1
N047 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 17
N048 Nicro. orbicollis CAN, ON, Algonquin P.P. 1 45.902, -77.605 30.vi.08 Macro. willowae sp. n. 5
N051 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 15.vii.08 Macro. willowae sp. n. 2
N052 Nicro. orbicollis CAN, ON, Frontenac 44.447, -76.577 30.vii.08 Macro. willowae sp. n. 1
N055 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 30.vii.08 Macro. willowae sp. n. 3
N057 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 29.vii.08 Macro. willowae sp. n. 1
N058 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 29.vii.08 Macro. willowae sp. n. 2
N060 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 29.vii.08 Macro. willowae sp. n. 2
N061 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 29.vii.08 Macro. willowae sp. n. 5
N062 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 29.vii.08 Macro. willowae sp. n. 3
N068 Nicro. defodiens CAN, ON, Algonquin P.P. 1 45.902, -77.605 29.vii.08 Macro. willowae sp. n. 9
N069 Nicro. orbicollis CAN, ON, Charleston Lake 44.500, -76.072 12.viii.08 Macro. willowae sp. n. 1
N075 Nicro. orbicollis CAN, ON, Frontenac 44.447, -76.577 26.viii.08 Macro. willowae sp. n. 1
N081 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. kaiju sp. n. 4 MF192750
N081 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. willowae sp. n. 9 MF192743
N086 Nicro. orbicollis CAN, ON, Windsor, Elgin St. 42.261, -83.057 18.vi.2009 Macro. willowae sp. n. 1
N088 Nicro. orbicollis CAN, ON, Hwy 132, Dacre 45.369, -76.988 25.vi.2009 Macro. willowae sp. n. 10
N089 Nicro. orbicollis CAN, ON, Carbine Rd. 45.33, -76.371 25.vi.2009 Macro. willowae sp. n. 9
N104 Nicro. defodiens CAN, BC, Prince George, nr. UNBC 53.904, -122.783 12.vi.2009 Macro. willowae sp. n. 1
N110 Nicro. defodiens CAN, BC, Prince George, nr. UNBC 53.904, -122.783 12.vi.2009 Macro. willowae sp. n. 1
N113 Nicro. defodiens CAN, BC, Prince George, nr. UNBC 53.904, -122.783 12.vi.2009 Macro. willowae sp. n. 4 MF192748
N114 Nicro. orbicollis CAN, PEI, Wellington, Route 2 46.452, -63.949 06.vii.2009 Macro. willowae sp. n. 8
N115 Nicro. orbicollis CAN, PEI, Wellington, Route 2 46.452, -63.949 06.vii.2009 Macro. willowae sp. n. 7
N116 Nicro. orbicollis CAN, PEI, Wellington, Route 2 46.452, -63.949 06.vii.2009 Macro. praedafimetorum 1 MF192754
N116 Nicro. orbicollis CAN, PEI, Wellington, Route 2 46.452, -63.949 06.vii.2009 Macro. willowae sp. n. 9 MF192747
N136 Nicro. defodiens CAN, BC, Prince George, nr. UNBC 53.904, -122.783 12.vi.2009 Macro. willowae sp. n. 1 MF192749
N139 Nicro. orbicollis CAN, ON, Carbine Rd. 45.33, -76.371 10.vii.2009 Macro. willowae sp. n. 12
N143 Nicro. orbicollis CAN, ON, Hamilton, Site 4-7 07.vii.2009 Macro. willowae sp. n. 100 MF192744
N145 Nicro. orbicollis CAN, ON, Hamilton, Site 4-7 07.vii.2009 Macro. willowae sp. n. 8
N147 Nicro. orbicollis CAN, ON, Hamilton, Site 4-7 07.vii.2009 Macro. willowae sp. n. 10
N153 Nicro. orbicollis CAN, NS, Dartmouth, Wright’s Cove Rd. 44.694, -63.611 09.vii.2009 Macro. willowae sp. n. 4
N160 Nicro. orbicollis CAN, ON, Waterloo 43.54, -80.211 07.vii.2009 Macro. willowae sp. n. 2
N161 Nicro. orbicollis CAN, ON, Waterloo 43.54, -80.211 07.vii.2009 Macro. willowae sp. n. 8
N165 Nicro. orbicollis CAN, ON, Carbine Rd. 45.33, -76.371 23.vii.2009 Macro. willowae sp. n. 17
N166 Nicro. orbicollis CAN, ON, Carbine Rd. 45.33, -76.371 23.vii.2009 Macro. willowae sp. n. 8
N167 Nicro. orbicollis CAN, NS, Glenmont, Black Hole Rd. 45.111, -64.296 17.vii.2009 Macro. willowae sp. n. 9
N168 Nicro. orbicollis CAN, NS, Cold Brook, Hwy 101 45.079, -64.592 13.vii.2009 Macro. willowae sp. n. 10 MF192745
N169 Nicro. orbicollis CAN, NS, Chipman 46.174, -65.899 08.vii.2009 Macro. willowae sp. n. 7
N174 Nicro. orbicollis CAN, NS, Hantsport 45.099, -64.184 21.vii.2009 Macro. willowae sp. n. 6
N178 Nicro. orbicollis CAN, NS, East River off Hwy 329 44.583, -64.164 10.viii.2009 Macro. willowae sp. n. 4
N180 Nicro. defodiens CAN, NS, Debert, Industrial Park 45.428, -63.429 05.viii.2009 Macro. willowae sp. n. 3
N181 Nicro. orbicollis CAN, ON, Carbine Rd. 45.33, -76.371 06.viii.2009 Macro. willowae sp. n. 8 MF192746
N185 Nicro. vespillo GER, Mooswald Forest, nr. Freiburg 48.0, 7.85 vi.2009 Macro. nataliae 4
N186 Nicro. vespillo GER, Mooswald Forest, nr. Freiburg 48.0, 7.85 vi.2009 Macro. nataliae 7 MF192752
N187 Nicro. vespillo GER, Mooswald Forest, nr. Freiburg 48.0, 7.85 vi.2009 Macro. nataliae 1
N188 Nicro. vespillo GER, Mooswald Forest, nr. Freiburg 48.0, 7.85 vi.2009 Macro. nataliae 5 MF192753
N191 Nicro. orbicollis USA, CT, Bethany 41.462, -72.961 16.vii.2009 Macro. willowae sp. n. 1
N192 Nicro. orbicollis USA, CT, Bethany 41.462, -72.961 14.viii.2009 Macro. willowae sp. n. 5
N216 Nicro. orbicollis USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 215
N218 Nicro. orbicollis USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 135
N222 Nicro. defodiens USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 30
N226 Nicro. orbicollis USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 30
N228 Nicro. orbicollis USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 97
N234 Nicro. marginatus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 10
N235 Nicro. guttula CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 7
N235x Nicro. marginatus CAN, AB, Onefour 49.121, -110.47 04.vii.2002 Macro. pratum sp. n. 3
N236 Nicro. obscurus CAN, AB, Onefour 49.121, -110.47 04.vii.2002 Macro. pratum sp. n. 5
N237 Nicro. marginatus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 13
N238 Nicro. obscurus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 5
N239 Nicro. obscurus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 11
N240 Nicro. marginatus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 13
N242 Nicro. hybridus CAN, AB, Onefour 49.121, -110.47 18.vii.2002 Macro. pratum sp. n. 7 MF192751
N243 Nicro. guttula CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 7
N244 Nicro. guttula CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 7
N246 Nicro. hybridus CAN, AB, Onefour 49.121, -110.47 18.vii.2002 Macro. pratum sp. n. 10
N274 Nicro. marginatus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. glaber 8
N275 Nicro. obscurus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. glaber 1
N295 Nicro. carolinus USA, NE, Kearney Co. 05.vi.2009 Macro. kaiju sp. n. 1
N295 Nicro. carolinus USA, NE, Kearney Co. 05.vi.2009 Macro. sp. 4
N298 Nicro. carolinus USA, NE, Kearney Co. 05.vi.2009 Macro. kaiju sp. n. 2
N298 Nicro. carolinus USA, NE, Kearney Co. 05.vi.2009 Macro. sp. 3
N303 Nicro. pustulatus USA, NE, Kearney Co. 13.vii.2009 Macro. pratum sp. n. 3
N308 Nicro. marginatus CAN, AB, Onefour 49.121, -110.47 17.vi.2003 Macro. pratum sp. n. 86
N329 Nicro. orbicollis USA, NH 2009 Macro. willowae sp. n. 41
N330 Nicro. orbicollis USA, NH 2009 Macro. willowae sp. n. 91
N331 Nicro. orbicollis USA, CT, Bethany 41.462, -72.961 2009 Macro. willowae sp. n. 13
N332 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. kaiju sp. n. 11
N333 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. kaiju sp. n. 74
N334 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. willowae sp. n. 1
N334 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. kaiju sp. n. 26
N334 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. sp. 1
N335 Nicro. carolinus USA, FL, Highlands Co, Lake Placid 27.181, -81.352 10.iii.2009 Macro. kaiju sp. n. 45
N336 Nicro. marginatus USA, NE, Kearney Co. vi.2009 Macro. pratum sp. n. 9
N338 Nicro. defodiens USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 8
N339 Nicro. defodiens USA, NH, Durham 43.134, -70.926 07.vi.2009 Macro. willowae sp. n. 163
N346 Nicro. orbicollis CAN, ON, Hwy 132, Dacre 45.369, -76.988 06.viii.2009 Macro. willowae sp. n. 6
N347 Nicro. orbicollis CAN, ON, Carbine Rd. 45.33, -76.371 06.viii.2009 Macro. willowae sp. n. 16

Pairwise distances were calculated using neighbour-joining (NJ) analyses with the Kimura-2-parameter (K2P) model in PAUP* v4.0b10 (Swofford 2003). Phylogenetic reconstructions of the COI dataset was performed using Bayesian inference (BI) in MrBayes v3.2.6 (Huelsenbeck and Ronquist 2001; Ronquist and Huelsenbeck 2003). Each specimen in the phylogeny is labeled with the mite species and the beetle number, followed by the host species and abbreviated state, province or country (Fig. 14).

MrModeltest v2.3 (Nylander 2004) was used to determine the best-fit model of molecular evolution for each molecular marker, which was determined to be GTR+I+G. Bayesian analysis was performed in MrBayes using the Markov Chain Monte Carlo (MCMC) method, two independent runs, with nucmodel = 4by4, Nst = 6, rates = invgamma, samplefreq = 1000, four chains = one cold and three heated. The COI dataset ran for 10 million generations, producing 19502 trees after a burn-in of 250 trees. The remaining trees in Mesquite, excluding the burn-in, were used to generate a majority-rule consensus tree displaying the posterior probability supports for each node. Bayesian analyses were performed using the on-line Computational Biology Service Unit at Cornell University, and at the Cyberinfrastructure for Phylogenetic Research (CIPRES) portal (Miller et al. 2010).

Results and discussion

Family Macrochelidae Vitzthum, 1930

Subfamily Macrochelinae

Macrocheles Latreille, 1829

Type species

Acarus marginatus Hermann, 1804 (= Acarus muscae domesticae Scopoli, 1772), by original designation.

Macrocheles willowae sp. n.

Figs 1, 2, 3, 4, 13A

Material examined

Type material. Holotype: female (CNC829414) on Nicrophorus orbicollis (N088, female) collected near Dacre, Ontario, Canada (45.369, -76.988), 25.vi.2009, coll: W. Knee.

Paratypes (26): Nine females (CNC829415–829423) with the same collection information as the holotype; 15 females (CNC829424–829438) on N. defodiens (N222, female), Durham, New Hampshire, USA (43.134, -70.926), 07.vi.2009, coll: W. Knee & M. Scott; female (CNC829439) on N. defodiens (N136, female), Prince George, near University of Northern British Columbia campus, British Columbia, Canada (53.904, -122.783), 12.vi.2009, coll: W. Knee & R. Dawson; female (CNC829440) on N. orbicollis (N143, male), Hamilton, Ontario, Canada, 7.vii.2009, coll: W. Knee.

Other material. 1241 mites examined from British Columbia, Nova Scotia, Ontario, Prince Edward Island, Connecticut, Florida, and New Hampshire on N. carolinus, N. defodiens, and N. orbicollis (Table 1).

Diagnosis female

As for Macrocheles (see Hyatt and Emberson 1988). All dorsal and ventral setae smooth and spinose, except J5 barbed and slightly shorter than Z5. Seta j1 simple with rounded tip, j1 slightly longer than z1. Dorsal hexagonal setae (j5, z5, j6) nearly as long as marginal and submarginal setae (R and UR). Dorsal shield with moderate reticulations throughout, except smooth in dorsal hexagonal area and between j4 setae, without well-defined procurved line, sigillary rami absent. Sternal shield more than twice as wide as long, punctures small, posterior margin concave. Well defined linea media transversa (l.m.t.) and linea oblique anteriores (l.o.a.), l.o.a. contacts l.m.t. Linea arcuata (l.arc.) well defined and contacts l.o.a. Linea angulata (l.ang.) and linea oblique posteriore (l.o.p.) well defined laterally but faint medially. Area punctata laterale (a.p.l.) well defined, but area punctata posteriore (a.p.p.) not well defined. Ventrianal shield longer than wide (ratio 1.3). Arthrodial brush as long as movable digit. Genu IV with six setae. Femur IV setae ad2, pd1 prominent spikes with flattened forked tip.

Description female

Dorsal idiosoma (Fig. 1). Dorsal shield 548 (526–572) long and 357 (344–372) (n=8) wide (level with r3), with 28 pairs of setae, all setae simple and spinose except J5 is barbed. Seta J5 16 (15–18) shorter than Z5 24 (22–27). Seta j1 simple with rounded tip, j1 18 (16–20) slightly longer than z1 16 (12–19). Marginal and submarginal setae simple, slightly longer 24 (23–25) than dorsal hexagonal setae 20 (15–22). Dorsal shield with moderate reticulations throughout, except smooth in dorsal hexagonal area and between j4 setae, shield without well-defined procurved line, sigillary rami absent, and posterolateral margins narrowed slightly. Shield with 22 pairs of pore-like structures, of which six are secretory glands and 16 are non-secretory poroids.

Figure 1. 

Female Macrocheles willowae sp. n. A dorsal idiosoma B seta J5.

Ventral idiosoma (Figs 2, 13A). Sternal shield more than twice as wide as long, medial length 91 (88–96), maximum width 213 (192–221) level with a.p.l., and minimum width 117 (115–124) posterior of st1. Sternal shield punctures small, posterior margin concave. Setae st1–3 38 (33–43) simple and spinose, and two pairs of lyrifissures (iv1, iv2) on sternal shield. Pear-shaped metasternal shields well separated from sternal shield margin bearing lyrifissure iv3 anteriorly and spinose seta st4 33 (30–35) posteriorly. Well defined l.m.t. and l.o.a., l.o.a. contacts l.m.t. Well defined l.arc. contacts l.o.a., l.ang. and l.o.p. well defined laterally but faint medially. Well defined a.p.l., a.p.p. not well defined. Genital shield length 149 (141–161), width 113 (104–120) level with st5. Genital shield truncate posteriorly and hyaline margin rounded anteriorly, spinose seta st5 32 (30–34) on shield, pair of lyrifissures iv5 off shield near posterior margin. Transverse line on genital shield well defined laterally and faint medially, small punctures along transverse line. Peritrematal shield narrow, fused to dorsal shield near r3, peritreme extends beyond posterior margin of coxa I, two poroids (id3, id7) and one gland (gd3) on the shield. Ventrianal shield longer than wide (ratio 1.3); length 198 (187–204), width 153 (144–168) level with JV2. Ventrianal shield bearing several faint transverse lines, three pairs of simple spinose preanal setae JV1–JV3 26 (21–30), spinose paranal (pan) 27 (25–30) and postanal (pon) 18 (16–20) setae, narrow cribrum and a pair of glands (gv3) on shield margin posterior of the anal opening. Ventral opisthosomal setae in soft integument simple and spinose, ZV1 21 (17–29), ZV2 26 (22–29) as long or nearly as long as Jv setae. Two pairs of glands (gv2 and unknown paired-pore) and four pairs of poroids (ivo, ivp) in opisthosomal soft integument.

Figure 2. 

Female Macrocheles willowae sp. n. ventral idiosoma including coxae.

Gnathosoma (Fig. 3). Basis capitulum medial length excluding internal malae 114 (106–122), width 150 (143–157) posterior to pc. Subcapitular setae simple: h1 38 (28–48), h2 16 (13–19), h3 53 (44–67), and pc 19 (16–21). Palp chaetotaxy normal for genus (2–5–6–14–15), palp apotele three-tined, al setae on trochanter, femur and genu slightly spatulate. Corniculi pointed, length along lateral margin 42 (37–51), internal malae slender and smooth. Epistome tripartite with bifid central element bearing small fringe medially, lateral elements broad and flag-like distally, epistomatic margin finely serrate. Subcapitulum with seven rows, six of which have deutosternal denticles; the anterior most row with few (four) denticles laterally, and the second anterior most row with paired ridges without any denticles. Chelicerae robust, length of second cheliceral segment including fixed digit 140 (134–146), and movable digit 54 (52–58). Fixed digit bidentate with one large and one small tooth, moveable digit with bidentate tooth. Pilus dentilis and dorsal seta on fixed digit simple spikes, fixed digit with lyrifissure on each paraxial and antiaxial faces. Movable digit with narrow fringed arthrodial corona, and plumose arthrodial brush (50) almost as long as movable digit.

Figure 3. 

Female Macrocheles willowae sp. n. A subcapitulum and palp, ventral aspect B chelicera, antiaxial aspect C epistome D tritosternum.

Legs (Fig. 4). Excluding ambulacra, lengths of leg I 420 (409–430), leg II 383 (357–402), leg III 338 (315–349), and leg IV 482 (469–489). As in all Macrocheles, ambulacra only present on legs II–IV, claws II–IV well developed. Pair of glands (gc) on coxa I. Setation of legs I–IV normal for Macrochelidae: coxae 2–2–2–1; trochanters 5–5–5–5; femora I (2–3/1,2/3–2) (as al–ad/av, pd/pv–pl), II (2–3/1,2/2–1), III (1–2/0,1/1–1), IV (1–2/1,1/0–1); genua I, II (2–3/1,2/1–2), III (1–2/1,2/0–1), IV (1–2/1,2/0–0); tibiae I (2–3/2,2/1–2), II (2–2/1,2/1–2), III, IV (1–1/1,2/1–1); tarsus I 20 setae plus numerous tapered setae distally, tarsi II–IV 18. Most leg setae simple, setiform, femur II ad1, III pd1, IV ad2, pd1, and genu II ad3 prominent spike setae with flattened forked tip with two to four tines that can appear as a single tapered point viewed laterally. Tarsus II with four large distal spike setae with thickened conical base and rounded tip. Tarsi III, IV with four and three, respectively, distal setae with wide base and flexible filamentous tip. Genu and tibia IV with paired slight ridge anterolateral and posterolateral.

Figure 4. 

Female Macrocheles willowae sp. n. legs I–IV, coxae omitted; leg I anterolateral, II posterolateral, III dorsal, IV anterolateral.

Male and immatures

Unknown.

Etymology

This species is named after my daughter Willow Knee. May it inspire her to notice the little creatures as well as the big.

Remarks

Macrocheles willowae sp. n. is most similar to M. merdarius (Berlese), M. nemerdarius Krantz and Whitaker, and M. pratum sp. n. Macrocheles merdarius is frequently found in litter, manure and compost worldwide, feeding on nematodes and eggs of insects (Krantz and Whitaker 1988). Macrocheles merdarius has been reported from small mammals, and female mites are often phoretic associates of dung beetles (Filipponi and Pegazzano 1963, Krantz and Whitaker 1988). Female M. willowae sp. n. differs from that of M. merdarius in the shape of the ventrianal shield, shape of the sternal shield, and length of the arthrodial brush. The anterior margin of the ventrianal shield is more truncated, and the widest part of the shield near JV2 is more angular for M. merdarius than it is for M. willowae sp. n. The posterior margin of the sternal shield is more concave for M. willowae sp. n. The arthrodial brush is almost as long as the movable digit for M. willowae sp. n., and for M. merdarius the brush is approximately half as long as the movable digit. Comparisons were made using the species description for M. merdarius and slide mounted material deposited in the CNC.

Macrocheles nemerdarius was described from the nest of a mouse, Peromyscus in Maryland and the nest of the eastern woodrat Neotoma floridana in Florida, USA, and this species is also phoretic on coprophilous beetles (Krantz and Whitaker 1988). Female M. willowae sp. n. differs from that of M. nemerdarius in having marginal or submarginal setae slightly longer than dorsal hexagonal setae, posterior margin of sternal shield more concave, pon seta smooth not weakly pilose, j1 only slightly longer than z1 not 1.5 times as long, and J5 slightly shorter than Z5 not half as long as Z5. Comparisons were made using the species description for M. nemerdarius and examination of the holotype specimen loaned from the National Museum of Natural History, Smithsonian Institution.

Female M. willowae sp. n. differs from that of M. pratum sp. n. in having marginal and submarginal setae slightly longer than dorsal hexagonal setae. Genu and tibia IV with slight ridge on anterolateral and posterolateral surfaces in M. willowae sp. n., while M. pratum sp. n. only has a ridge on the posterolateral surface. Seta J5 is slightly shorter than Z5 and more spinose in M. willowae sp. n., J5 is less than half as long as Z5 in M. pratum sp. n. Punctures on the sternal shield are smaller and less prominent in M. willowae sp. n. than in M. pratum sp. n. The ventrianal shield is longer than wide for both species, but the shield is slightly narrower in M. pratum sp. n., ratio of 1.4 compared to 1.3 for M. willowae sp. n.

In Krantz and Whitaker (1988), Dr. W. Yoder provided a short diagnosis and partial illustrations of the female and male of an undescribed and unnamed Macrocheles species collected from Nicrophorus beetles and three mammal species (Tamiasciurus hudsonius, American red squirrel in Michigan; Tamias striatus, eastern chipmunk in Maryland; and Zapus hudsonius, meadow jumping mouse in Prince Edward Island). This undescribed species was a common associate of Nicrophorus beetles, but it was also found frequently enough on live rodents to suggest an association with small mammals (Krantz and Whitaker 1988). Dr. W. Yoder reportedly intended to formally describe and illustrate this new species of Macrocheles; however, to date this species has not been described. Macrocheles willowae sp. n. is likely the same species that Dr. W. Yoder was intending to describe. Over several years, repeated attempts were made to contact Dr. W. Yoder about the status of the description, but contact was unsuccessful.

Macrocheles pratum sp. n.

Figs 5, 6, 7, 8, 13B

Material examined

Type material. Holotype: female (CNC829441) on Nicrophorus marginatus (N336, female) collected in Kearney Co., Nebraska, USA, vi.2009, coll: W. Knee & W. Hoback.

Paratypes (11): eight females (CNC829442–829449) with the same collection information as the holotype; two females (CNC829450, 829451) on N. hybridus (N242, female), Onefour, Alberta, Canada, 18.vii.2002, coll: W. Knee & D. Johnson; female (CNC829452) on N. guttula (N235, female), Onefour, Alberta, 17.vi.2003, coll: W. Knee & D. Johnson.

Other material. 184 mites examined from Alberta and Nebraska on Nicrophorus guttula, N. hybridus, N. marginatus, N. obscurus, and N. pustulatus (Table 1).

Diagnosis female

All dorsal and ventral setae smooth and spinose, except J5 barbed and much shorter than Z5. Seta j1 simple with rounded tip, j1 slightly longer than z1. Dorsal hexagonal setae slightly longer than marginal and submarginal setae. Dorsal shield with moderate reticulations throughout, except smooth in dorsal hexagonal area and between j4 setae, without well-defined procurved line, sigillary rami absent. Sternal shield more than twice as wide as long, punctures moderate size, posterior margin concave. Well defined l.m.t. and l.o.a.; l.o.a. contacts l.m.t. Well defined l.arc. contacts l.o.a., l.ang. and l.o.p. well defined laterally but faint medially. Well defined a.p.l., but a.p.p. not well defined. Ventrianal shield longer than wide (ratio 1.4). Arthrodial brush as long as movable digit. Genu IV with six setae. Femur IV setae ad2, pd1 prominent spikes with flattened forked tip.

Description female

Dorsal idiosoma (Fig. 5). Dorsal shield 520 (469–547) long and 358 (323–379) (n=8) wide (level with r3), with 28 pairs of setae, all setae simple and spinose except J5 barbed. Seta J5 9 (8–10) half as long as Z5 22 (18–23). Seta j1 simple with rounded tip, j1 20 (19–21) longer than z1 16 (13–18). Marginal and submarginal setae simple, shorter (19) than dorsal hexagonal setae 25 (24–28). Dorsal shield with moderate reticulations throughout, except smooth in dorsal hexagonal area and between j4 setae, shield without well-defined procurved line, sigillary rami absent, and posterolateral margins narrowed slightly. Shield with 22 pairs of pore-like structures, of which six are secretory glands and 16 are non-secretory poroids.

Figure 5. 

Female Macrocheles pratum sp. n. A dorsal idiosoma B seta J5.

Ventral idiosoma (Figs 6, 13B). Sternal shield more than twice as wide as long, medial length 92 (86–99), maximum width 217 (196–224) level with a.p.l., and minimum width 114 (110–119) posterior of st1. Sternal shield punctures moderate size, posterior margin concave. Setae st1–3 40 (35–45) simple and spinose, and two pairs of lyrifissures (iv1, iv2) on sternal shield. Pear-shaped metasternal shields well separated from sternal shield margin bearing lyrifissure iv3 anteriorly and spinose seta st4 35 (33–39) posteriorly. Well defined l.m.t. and l.o.a., l.o.a. contacts l.m.t. Well defined l.arc. contacts l.o.a., l.ang. and l.o.p. well defined laterally but faint medially. Well defined a.p.l., a.p.p. not well defined. Genital shield length 151 (138–158), width 112 (99–122) level with st5. Genital shield truncate posteriorly and hyaline margin rounded anteriorly, spinose seta st5 32 (30–34) on shield, pair of lyrifissures iv5 off shield near posterior margin. Transverse line on genital shield well defined laterally and faint medially, small punctures along transverse line. Peritrematal shield narrow, fused to dorsal shield near r3, peritreme extends beyond posterior margin of coxa I, two poroids (id3, id7) and one gland (gd3) on the shield. Ventrianal shield longer than wide (ratio 1.4); length 186 (168–194), width 135 (122–146) level with JV2. Ventrianal shield bearing several faint transverse lines, three pairs of simple spinose preanal setae JV1–JV3 26 (21–29), spinose pan 25 (22–28) and pon 18 (15–19), narrow cribrum and a pair of glands (gv3) on shield margin posterior of the anal opening. Ventral opisthosomal setae in soft integument simple and spinose, ZV1 17 (13–23), ZV2 25 (21–27) as long or nearly as long as Jv setae. Two pairs of glands (gv2 and unknown paired-pore) and four pairs of poroids (ivo, ivp) in opisthosomal soft integument.

Figure 6. 

Female Macrocheles pratum sp. n. ventral idiosoma including coxae.

Gnathosoma (Fig. 7). Basis capitulum medial length excluding internal malae 115 (113–116), width 139 (134–143) posterior to pc. Subcapitular setae simple: h1 44 (41–48), h2 16 (13–18), h3 57 (51–62), and pc 20 (19–23). Palp chaetotaxy normal for genus (2–5–6–14–15), palp apotele three-tined, al setae on trochanter, femur and genu slightly spatulate. Corniculi pointed, maximum length 39 (35–45), internal malae slender and smooth. Epistome tripartite with bifid central element bearing small fringe medially, lateral elements broad and flag-like distally, epistomatic margin finely serrate. Subcapitulum with seven rows: six rows have deutosternal denticles, the anterior most, and two posterior most rows with few (four) denticles laterally; the second anterior most row with paired ridges without any denticles. Chelicerae robust, length of second cheliceral segment including fixed digit 135 (122–141), and movable digit 49 (45–52). Fixed digit bidentate with one large and one small tooth, movable digit with a bidentate tooth flanked by a small tooth distally. Pilus dentilis and dorsal seta on fixed digit simple spikes, fixed digit with lyrifissure on each paraxial and antiaxial faces. Movable digit with narrow fringed arthrodial corona, and plumose arthrodial brush (47) almost as long as movable digit.

Figure 7. 

Female Macrocheles pratum sp. n. A subcapitulum and palp, ventral aspect B chelicera, antiaxial aspect C epistome D tritosternum.

Legs (Fig. 8). Excluding ambulacra, lengths of leg I 418 (409–432), leg II 390 (362–438), leg III 340 (319–358), and leg IV 474 (463–490). As in all Macrocheles ambulacra only present on legs II–IV, claws II–IV well developed. Pair of glands (gc) on coxa I. Setation of legs I–IV normal for Macrochelidae: coxae 2–2–2–1; trochanters 5–5–5–5; femora I (2–3/1,2/3–2), II (2–3/1,2/2–1), III (1–2/0,1/1–1), IV (1–2/1,1/0–1); genua I, II (2–3/1,2/1–2), III (1–2/1,2/0–1), IV (1–2/1,2/0–0); tibiae I (2–3/2,2/1–2), II (2–2/1,2/1–2), III, IV (1–1/1,2/1–1); tarsus I 20 setae plus numerous tapered setae dorsoterminally, tarsi II–IV 18. Most leg setae simple, setiform, femur II ad1, III pd1, IV ad2, pd1, and genu II ad3 prominent spike setae with flattened forked tip with two to four tines that can appear as a single tapered point viewed laterally. Tarsus II with four large distal, and one ventral, spike setae with thickened conical base and rounded tip. Tarsi III, IV with four distal spike setae with wide base and flexible filamentous tip. Genu and tibia IV with slight ridge posterolateral.

Figure 8. 

Female Macrocheles pratum sp. n. legs I–IV, coxae omitted; leg I anterolateral, II posterolateral, III posterolateral, IV femur dorsal, genu, tibia, tarsus anterolateral.

Male and immatures

Unknown.

Etymology

Pratum (Latin neuter noun) means “meadow”. This species was only collected in Kearney County, Nebraska and Onefour, Alberta, which are in the prairies.

Remarks

The female of Macrocheles pratum sp. n. is most similar to those of M. willowae sp. n., M. nemerdarius, M. spinipes Berlese, and M. grossipes Berlese. Macrocheles pratum sp. n. differs from M. willowae sp. n. as outlined in the M. willowae sp. n. description.

Female M. pratum sp. n. differs from that of M. nemerdarius in having larger more prominent punctures on the sternal shield, the posterior margin of the sternal shield is more concave, pon seta is smooth not weakly pilose, j1 is only slightly longer than z1 not 1.5 times as long, J5 is shorter and broader for M. pratum sp. n. (9) than for M. nemerdarius (13), and the ventrianal shield is narrower, length to width ratio of 1.4 for M. pratum sp. n. and 1.2 for M. nemerdarius. Measurements were made examining M. nemerdarius holotype specimen loaned from the National Museum of Natural History, Smithsonian Institution.

Macrocheles spinipes and M. grossipes are associated with coprophilous beetles (Krantz 1988). Female M. pratum sp. n. differs from those of M. spinipes and M. grossipes in having larger more prominent punctures and transverse lines on the sternal shield, the posterior margin of the sternal shield more concave, arthrodial brush nearly as long as movable digit and not half or three quarters as long as movable digit, setae ad2 and pd1 on femur IV are large spike-like setae with flattened forked tips with two to four tines, ventrianal shield tapers relatively more towards posterior starting anterior of pan setae, and ventrianal shield is narrower, length to width ratio of 1.4 for M. pratum sp. n. and 1.2 for M. spinipes and M. grossipes. Measurements were made examining M. spinipes and M. grossipes voucher material from the Oregon State University Arthropod Collection.

Macrocheles kaiju sp. n.

Figs 9, 10, 11, 12, 13C

Material examined

Type material. Holotype: female (CNC829453) on Nicrophorus carolinus (N333, male) collected Highlands Co. Lake Placid, Florida, USA (27.181, -81.352), 10.iii.2009, coll: W. Knee & S. Peck.

Paratypes (28): 14 females (CNC CNC829454–829467) with the same collection information as the holotype; 13 females (CNC829468–829480) on N. carolinus (N334, female), Highlands Co. Lake Placid, Florida, USA (27.181, -81.352), 10.iii.2009, coll: W. Knee & S. Peck; female (CNC829481) on N. carolinus (N081), Highlands Co. Lake Placid, Florida, USA (27.181, -81.352), 10.iii.2009, coll: W. Knee & S. Peck.

Other material. 134 mites examined from Florida and Nebraska on N. carolinus (Table 1).

Diagnosis female

Dorsal setae smooth and spinose, except r3, r4, s6, z6, S1S5, Z1–Z5, J2 barbed distally, J5 barbed, marginal and submarginal setae barbed distally. Seta j1 smooth, spike, tapered distally with rounded tip, slightly longer than z1. Seta J5 much shorter than Z5. Dorsal hexagonal setae as long as marginal and submarginal setae. Dorsal shield smooth medially with faint reticulations near shield margins, shield tapers from humeral region to posterior margin. Dorsal shield without well-defined procurved line, sigillary rami absent. Setae on sternal, genital and ventrianal shields, and ZV1 smooth and spinose, other ventral setae in soft integument barbed distally. Sternal shield wider than long, punctures small, posterior margin slightly concave. Well defined l.m.t. and l.o.a.; l.o.a. contacts l.m.t. Well defined l.arc. contacts l.o.a., l.ang. and l.o.p. well defined laterally but faint medially. Well defined a.p.l., but a.p.p. not well defined. Ventrianal shield longer than wide (ratio 1.5), pon longer than pan, pon slightly spatulate. Arthrodial brush nearly as long as movable digit. Genu IV with six setae.

Description female

Dorsal idiosoma (Fig. 9). Dorsal shield 736 (647–812) long and 484 (421–547) (n=8) wide (level with r3), with 28 pairs of setae. Dorsal setae smooth and spinose, except r3, r4, s6, z6, S1S5, Z1–Z5, J2 barbed distally, J5 barbed, marginal and submarginal setae barbed distally. Seta J5 22 (19–24) less than half as long as Z5 75 (65–83). Seta j1 29 (25–34) smooth, spike, tapered distally with rounded tip, slightly longer than z1 24 (20–32). Dorsal hexagonal setae 61 (50–71) smooth and spinose, as long as distally barbed marginal and submarginal setae (61). Dorsal shield smooth medially with faint reticulations near shield margins, shield tapers from humeral region to posterior margin. Dorsal shield without well-defined procurved line, sigillary rami absent. Dorsal shield fused to peritrematal shield near r3 and anterior margin of shield wraps around onto ventral surface, j1 on slight projection and typically on the venter, and z1 occasionally expressed ventrally. Shield with 22 pairs of pore-like structures, of which six are secretory glands and 16 are non-secretory poroids.

Figure 9. 

Female Macrocheles kaiju sp. n. A dorsal idiosoma B seta J5.

Ventral idiosoma (Figs 10, 13C). Sternal shield wider than long, medial length 155 (145–163), maximum width 260 (224–288) level with a.p.l., and minimum width 115 (103–121) posterior of st1. Sternal shield punctures small, posterior margin slightly concave. Setae st1–3 75 (61–92) simple and spinose, and two pairs of lyrifissures (iv1, iv2) on sternal shield. Pear-shaped metasternal shields well separated from sternal shield margin bearing lyrifissure iv3 anteriorly and spinose seta st4 80 (73–89) posteriorly. Well defined l.m.t. and l.o.a.; l.o.a. contacts l.m.t. Well defined l.arc. contacts l.o.a., l.ang. and l.o.p. well defined laterally but faint medially. Well defined a.p.l., a.p.p. not well defined. Genital shield length 196 (172–226), width 123 (109–141) level with st5. Genital shield truncate posteriorly and hyaline margin rounded anteriorly, spinose seta st5 70 (65–74) on shield, pair of lyrifissures iv5 off shield near posterior margin. Transverse line on genital shield well defined, and without punctures. Peritrematal shield narrow, fused to dorsal shield near r3, peritreme extends beyond posterior margin of coxa I, two poroids (id3, id7) and one gland (gd3) on the shield. Ventrianal shield longer than wide (ratio 1.5); length 230 (202–250), width 149 (135–160) anterior to JV2. Ventrianal shield bearing several faint transverse lines, three pairs of simple spinose preanal setae JV1–JV3 65 (64–75), spinose pan 37 (26–43) shorter than slightly spatulate pon 47 (40–54), narrow cribrum and a pair of glands (gv3) on shield margin posterior of the anal opening. Seta ZV1 55 (48–60) is simple, all other ventral opisthosomal setae in soft integument barbed distally, ZV1 and ZV2 67 (58–75) as long or nearly as long as Jv setae. Two pairs of glands (gv2 and unknown paired-pore) and four pairs of poroids (ivo, ivp) in opisthosomal soft integument.

Figure 10. 

Female Macrocheles kaiju sp. n. ventral idiosoma including coxae.

Gnathosoma (Fig. 11). Basis capitulum medial length excluding internal malae 159 (152–169), width 158 (153–170) posterior to pc. Subcapitular setae simple: h1 66 (61–70), h2 19 (17–21), h3 92 (85–98), and pc 25 (24–28). Palp chaetotaxy normal for genus (2–5–6–14–15), palp apotele three-tined, al setae on trochanter, femur and genu slightly spatulate. Corniculi pointed, maximum length 50 (45–60), internal malae thick and bristled. Epistome tripartite with bifid central element bearing small fringe medially, lateral elements broad and flag-like distally with irregular barbs, epistomatic margin finely serrate. Subcapitulum with seven rows, six of which have deutosternal denticles; the anterior most row with few (four) denticles laterally, and the second anterior most row with paired ridges without any denticles. Chelicerae robust, length of second cheliceral segment including fixed digit 184 (173–198), and movable digit 64 (60–67). Fixed digit bidentate with one large and one small tooth, movable digit with a bidentate tooth flanked by a small tooth distally. Pilus dentilis and dorsal seta on fixed digit simple spike, fixed digit with lyrifissure on each paraxial and antiaxial faces. Movable digit with narrow fringed arthrodial corona, and plumose arthrodial brush (57) almost as long as movable digit.

Figure 11. 

Female Macrocheles kaiju sp. n. A subcapitulum and palp, ventral aspect B chelicera, antiaxial aspect C epistome D tritosternum.

Legs (Fig. 12). Excluding ambulacra, lengths of leg I 512 (488–527), leg II 576 (525–622), leg III 482 (436–528), and leg IV 690 (628–737). Ambulacra only present on legs II–IV, claws II–IV well developed. Slight ridge on femur II anterolateral, not always easily visible. Slight ridge on femur IV dorsal, genu and tibia IV posterolateral. Pair of glands (gc) on coxa I. Setation of legs I–IV normal for Macrochelidae: coxae 2–2–2–1; trochanters 5–5–5–5; femora I (2–3/1,2/3–2), II (2–3/1,2/2–1), III (1–2/0,1/1–1), IV (1–2/1,1/0–1); genua I, II (2–3/1,2/1–2), III (1–2/1,2/0–1), IV (1–2/1,2/0–0); tibiae I (2–3/2,2/1–2), II (2–2/1,2/1–2), III, IV (1–1/1,2/1–1); tarsus I 20 setae plus numerous tapered setae dorsoterminally, tarsi II–IV 18. Setae on leg I are setiform and simple, setae on legs II–IV variable, most are setiform, others are variously modified. Femur II ad1, genu II ad3, and trochanter III with a prominent spike setae with flattened forked tip with two to four tines that can appear as a single tapered point viewed laterally. Tarsus II with 13 thick conical spike setae with either a rounded or filamentous tip; filamentous tip fragile and easily broken. Tarsi III, IV with four distal spike setae with wide base and flexible filamentous tip, tip easily broken. Long setae with small spatulate tip with or without barbs on femur IV ad1, ad2, pd1, genu IV al, ad1, pd1, pd2, tibia IV al, pl, and three on tarsus IV. Setae with small spatulate tip appear pointed when viewed laterally.

Figure 12. 

Female Macrocheles kaiju sp. n. legs I–IV, coxae omitted; leg I anterolateral, II posterolateral, III and IV dorsal.

Male and immatures

. Unknown.

Etymology

Kaiju, 怪獣, from Japanese means strange beast, and refers to giant monsters such as Godzilla or Mothra. Female M. kaiju sp. n. is relatively unique morphologically when compared to other Macrocheles species associated with beetles, it is relatively large, has a unique dorsal shield shape, and bears numerous setae with distinct forms.

Remarks

Female M. kaiju sp. n. is different from that of any other described Macrocheles species; however, it does fit the Macrocheles generic description (see Hyatt and Emberson 1988). Female M. kaiju sp. n. has two character states that are irregular for Macrocheles but somewhat similar to Holostaspella (Macrochelidae) species: the anterior margin of the dorsal shield wraps around onto the ventral surface such that j1 is on a slight projection on the venter; and a slight ridge is present on femur II. Holostaspella species are characterised in part by females having a spur on femur II, and j1 being on a tuberculate anterior extension of the dorsal shield but not wrapped around onto the venter. Macrocheles kaiju sp. n. differs from that of Holostaspella species in having weak ornamentation on the dorsal shield, its lateral regions without a series of depressions; j1 is smooth and not pectinate, j1 is on a slight projection and not a prominent tuberculate extension; sternal shield weakly ornamented and without strong median ridge; and metasternal shields small and always free of endopodal shields.

Figure 13. 

Sternal shield A Macrocheles willowae sp. n. B M. pratum sp. n. C M. kaiju sp. n.

Phylogenetics

COI was amplified from 14 Macrocheles specimens representing six species, with 689 characters in total, 430 constant, 39 parsimony-uninformative, 220 parsimony-informative. NJ analysis (K2P) was performed on 14 ingroup Macrocheles specimens. Average intraspecific pairwise distance was low (1.2% ±1.4), and the maximum intraspecific divergence observed was for M. willowae sp. n. (2.8%). The higher than average intraspecific divergence for M. willowae sp. n. was due to the divergence between mites from different host species. Pairwise distance between M. willowae sp. n. mites from N. defodiens and those from N. orbicollis and N. carolinus was higher than average (5.2% ±0.1), while divergence among mites from N. defodiens and mites from N. orbicollis and N. carolinus was low, 0.1 and 0.6% respectively. Mean interspecific divergence was high (20% ±2.8), and the maximum divergence observed was between M. nataliae and M. subbadius (25%). The range of intra- (0.3–2.8%) and interspecific (15–25%) pairwise divergence did not overlap.

The majority rule consensus tree from the BI analysis of COI was well supported, with all nodes having high posterior probabilities, and eight nodes with 100% support (Fig. 14). Macrocheles willowae sp. n. was divided into two well supported clades, one with mites from N. defodiens and the other with mites from N. orbicollis and N. carolinus. Macrocheles willowae sp. n. did not appear to diverge based on geographic location (Fig. 14). Macrocheles willowae sp. n. mites from N. defodiens and those from N. orbicollis and N. carolinus were morphologically indistinguishable, despite the higher than average intraspecific divergence between these two well supported clades. The phylogenetic relationships between Macrocheles species, and the genetic structure of these newly described species, requires further analysis with better taxon sampling, specimens from more host species and localities, and additional molecular markers.

Figure 14. 

Majority rule consensus tree of 19502 trees generated by Bayesian MCMC analysis (10 million generations) of 689bp fragment of COI from 14 ingroup specimens representing six Macrocheles species, and two outgroup specimens representing two species, posterior probabilities >50% shown above branches.

Distribution and biology

Seven species of macrochelids were collected from 112 Nicrophorus beetles representing nine species from three countries (Canada, USA, Germany) and 10 provinces or states (Table 1). Nicrophorus carolinus was associated with the most Macrocheles species (3), three host species had only two macrochelid species, and five had only one macrochelid species. Mites were usually found under the elytra, either clasping onto the integument near the prospiracle (68%) or on the ventral surface of the elytra (22%), and sometimes they were on the coxae (10%). Mites attached to the outer surface of the beetle could have been dislodged into the preservative.

A total of 1659 Macrocheles mites were collected from 112 beetles, M. willowae sp. n. (1268 mites on 86 beetles) was the most abundant, second most abundant was M. pratum sp. n. (196 mites on 15 beetles), M. kaiju sp. n. (163 mites on 7 beetles) was the third most abundant, and the four other species of Macrocheles collected were at low abundances (32 mites total on 10 beetles) (Table 1). Macrocheles pratum sp. n. was collected from five host species and had the greatest host range of all species collected. Macrocheles willowae sp. n. collected from three host species had the second broadest host range. Macrocheles nataliae, M. praedafimetorum, and M. kaiju sp. n. were each collected from a single host species.

The species with the greatest geographic range was M. willowae sp. n., collected from 22 sites, across seven provinces/states in Canada and USA. Macrocheles pratum sp. n. was collected from a single site in Alberta (Canada) and from another site in Nebraska (USA). Macrocheles kaiju sp. n. was collected from one site in Florida and another site in Nebraska, USA. The four other macrochelid species collected were each found in a single locale (Table 1).

COI sequences generated in this study were compared against those on GenBank and BOLD, and M. willowae sp. n. was the only species to have high level (100%) matches on BOLD. These matching sequences belonged to generic level identified specimens from Alberta, Ontario, Saskatchewan, Nova Scotia, and Florida. The species briefly diagnosed by Dr. W. Yoder was collected from three species of rodents in Maryland, Michigan and Prince Edward Island. Combined together, results from this study, BOLD and Dr. W. Yoder’s findings, the geographic distribution of M. willowae sp. n. may cover 11 provinces or states in Canada and USA.

Acknowledgements

I am grateful to D. Johnson, D. Sikes, J. Müller, J. Sweeney, M. Nishikawa, M. Schilthuizen, M. Scott, P. Smiseth, R. Dawson, S. Peck, S. Suzuki, S. Trumbo, M. Locke, W. Hoback, and W. Hunting for providing numerous beetle specimens from around the world. I also thank T. Hartzenberg for her assistance in the field and the lab, as well as the private land owners who permitted sampling on their property. I thank G.W. Krantz and E.E. Lindquist for their comments on an earlier draft of this manuscript, and F. Beaulieu for his input on the figures, and pores and poroids. I also thank the National Museum of Natural History, Smithsonian Institution, and Oregon State University Arthropod Collection for lending type material and vouchers for examination. I thank the Bavarian State Collection of Zoology (Staatliche Naturwissenschaftliche Sammlungen Bayerns – SNSB), Barcoding Fauna Bavarica (BFB) and the German Barcode of Life (GBOL) for sharing Holostaspella subornata sequence data. This research was conducted with a permit to collect in Provincial Parks issued by Ontario Parks and coordinated by B. Steinberg. This study was funded in part by an NSERC Discovery Grant to M.R. Forbes.

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