Research Article |
Corresponding author: Eduardo Suárez-Morales ( esuarez@ecosur.mx ) Academic editor: Danielle Defaye
© 2017 Aurélie Delaforge, Eduardo Suárez-Morales, Wojciech Walkusz, Karley Campbell, C. J. Mundy.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Delaforge A, Suárez-Morales E, Walkusz W, Campbell K, Mundy CJ (2017) A new species of Monstrillopsis (Crustacea, Copepoda, Monstrilloida) from the lower Northwest Passage of the Canadian Arctic. ZooKeys 709: 1-16. https://doi.org/10.3897/zookeys.709.20181
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A new species of monstrilloid copepod, Monstrillopsis planifrons sp. n., is described from an adult female that was collected beneath snow-covered sea ice during the 2014 Ice Covered Ecosystem – CAMbridge bay Process Study (ICE-CAMPS) in Dease Strait of the Canadian Arctic Archipelago. Currently, up to six species of this order are known to occur in polar latitudes. The new species described herein shares similarities with Monstrillopsis dubia (Scott, 1904) but differs in its body proportions and cephalothorax ornamentation; the cephalothorax is covered by minute scattered papillae on dorsal and ventral surfaces; this species has a reduced fifth leg endopod, fifth leg exopod armed with three setae, antennule with fused segments 3–4, and the genital double-somite bears unique posterolateral processes. This is the second species of this genus recorded in the Arctic, after Monstrillopsis ferrarii (Suárez-Morales & Ivanenko, 2004), described from the White Sea, and is the first record of Monstrillopsis in Canadian waters. With the addition of this new species and the recognition of Monstrillopsis bernardensis comb. nov. as a member of this genus, the number of nominal species is now 15. Overall, this genus has a tendency to be distributed in temperate and cold waters, while only three species have been found in tropical and subtropical latitudes.
copepods, zooplankton, taxonomy, under-ice community, Canadian Arctic Archipelago
Members of the marine copepod order Monstrilloida (Sars, 1901) are rarely obtained during plankton surveys as the first naupliar developmental stage and the non-feeding adults are free-living forms that are only briefly present in the water column and can be caught during plankton samplings in coastal areas (
The biology and diversity of the planktonic fauna living beneath sea ice are still being studied in the Arctic regions. There have been surveys on the dynamics and composition of planktonic copepods (
As part of the 2014 Ice Covered Ecosystem – CAMbridge bay Process Study (ICE-CAMPS) in Dease Strait, Canadian Arctic, zooplankton samples were collected between March and June. Amongst these samples, adult female individuals of the monstrilloid copepod genus were collected. Taxonomic examination of one of these specimen revealed that it represented a previously undescribed species of Monstrillopsis (sensu Sars, 1921). The purpose of this study is to describe this species, to compare it with its closest congeners, and provide insight on the diversity and distribution of the genus Monstrillopsis in Dease Strait, NU, Canada.
The specimen observed here was obtained during the 2014 ICE-CAMPS campaign in Dease Strait, lower Northwest Passage of the Canadian Arctic (Fig.
Adult female holotype from Dease Strait (69°1.5'N; 105°20.2'W), partially dissected. Selected appendages (legs 1–4) and cephalothorax and urosome on semi-permanent slides, mounted on glycerine. Date of collection: 02 June 2014. Plankton sampled underneath ice-covered water column. Slides deposited in the Collection of Zooplankton at El Colegio de la Frontera Sur (ECOSUR), in Chetumal, Mexico (ECO-CH-Z-09535).
Female. Body length of holotype specimen measured from anterior end of cephalosome to posterior margin of anal somite = 1.92 mm. Cephalothorax (incorporating first pedigerous somite) approximately 1.1 mm long, representing 58% of total body length (Fig.
Monstrillopsis planifrons sp. n., adult female holotype from the Canadian Arctic. A cephalic region, dorsal view B habitus, dorsal view, arrow shows three paired dorso-medial papilla-like processes on second pedigerous somite C urosome, ventral view, showing fifth legs, ovigerous spines not shown, only its insertion area D urosome, dorsal view E insertion of ovigerous spine on ventral surface of genital double-somite F terminal section of ovigerous spines G eggs along ovigerous spines. Scale bars: A, C, D 100 µm, B 500 µm, E–G 25 µm.
Urosome slender, consisting of fifth pedigerous somite, genital double-somite, and preanal and anal somites, together measuring 0.31 mm and representing 16% of total body length. Relative lengths of fifth pedigerous somite, genital double-somite, preanal and anal urosomites as: 31:38.2:14.1:16.7= 100, respectively (Fig.
Antennules relatively long, slender, not straight but clearly divergent (Fig.
Monstrillopsis planifrons sp. n., adult female holotype from the Canadian Arctic. A right antennule showing armature following nomenclature by Grygier & Ohtsuka (1995), dorsal view B cephalic area showing forehead and perioral ornamentation, lateral view C cephalic area, showing cuticular processes and ornamentation, ventral view, arrow shows supernumerary spiniform element on first segment of left antennule D detail of first and second antennulary segments of left antennule showing supernumerary spiniform element on first segment (*) E fifth leg, ventral view showing small lobe-like processes on inner margin of exopodal (outer) lobes (arrowed) F urosome, showing fifth legs and ovigerous spines, lateral view. Scale bars: A 200 µm, B–F 100 µm, D–E 50 µm.
Incorporated first pedigerous somite and succeeding three free pedigerous somites each bearing a pair of biramous legs. Legs 1–4 slightly increasing in size posteriorly, leg 1 being shortest. Intercoxal sclerites of legs 1–4 subrectangular, widest transversely, with rounded margins, with surface and posterior margins smooth; sclerites with decreasing size, that of leg 1 being largest (Fig. 4AE–H). Basis of legs articulating with large, rectangular coxa along diagonal line. Basis of legs 1–4 with hair-like lateral seta (Fig.
Armature formula of legs 1-4 as:
basis | endopod | exopod | |
leg 1 | 1-0 | 0-1;0-1;1,2,2 | I-1;0-1;I,2,2 |
legs 2–4 | 1-0 | 0-1;0-1;1,2,2 | I-1;0-1;I,1,2,2 |
Fifth legs medially conjoined, indistinctly bilobed, inner (endopodal) lobe incospicuous, represented by small inner protuberance (arrows in Fig.
The specific epithet, derived from the Latin adjective planus (flat) and the noun frons (forehead), makes reference to the flat, protuberant frontal margin on the cephalic area, which is distinctive of this species.
The Arctic species described herein is assigned to the genus Monstrillopsis owing to its possession of the combination of characters noted by
Monstrillopsis planifrons sp. n. differs in several respects from its known congeners. Most species of Monstrillopsis of which females are known, like M. dubioides Suárez-Morales, 2004, M. ferrarii Suárez-Morales & Ivanenko, 2004, and M. chilensis, have affinities with M. dubia. This group of species share a relatively short cephalothorax (ca. 50–56% of total body length), four caudal setae, a well-defined digitiform inner lobe on the female fifth leg, an outer lobe armed with three long setae, antennule relatively short (30–35% of cephalothorax length) distinctly 4-segmented, and a relatively long genital double-somite (ca. 30% of urosome) with an expanded proximal half (
Monstrillopsis planifrons sp. n. differs from this group of species in having relatively longer antennules (53% of total body length), which is one of the most striking characters of this species; this pattern is similar to that depicted by
The antennule structure and armature are also a source of distinctive apomorphies of this new species. In several species of the genus the female antennulary segments 3–4 are clearly separate, as in M. dubia (
Monstrillopsis planifrons sp. n. has a distinctive genital double-somite, with a pair of large lateral protuberances on the posterior half of the somite, visible on dorsal and ventral views (Fig.
Another distinctive character of the new species is its produced, flat corrugate forehead; this character is absent from all its known congeners, which have a simple, rounded forehead as in M. dubia (Scott, 1904, pl. XII, fig. 14), M. dubioides (
Additional differences of the new species with respect to its congeners include a weakly developed fifth leg inner lobe, which is remarkably reduced to a small rounded inner protuberance (arrowed in Fig.
In the new species the anal somite is about as long as the preceding urosomite; it shares this character with M. ferrarii (
Finally, the new species has the cephalothorax covered by small papilla-like structures; this kind of ornamentation has not been described in other species of the genus but it is known in several species of Monstrilla (i.e., M. wandelii Stephensen, 1913; M. elongata Suárez-Morales, 2001; M. pustulata Suárez-Morales & Dias, 2001). In light of these many differences, the erection of a new species for the specimen from the Canadian Arctic seems to be well justified.
The oceanography of the lower Northwest Passage is distinctive due to its relatively lower salinity, resulting from the four large rivers draining into the waterway (
Several authors have questioned the validity of the genus Monstrillopsis Sars (
This is the fourth record of a monstrilloid species and the second of Monstrillopsis in Arctic waters.
The most recent revision of Monstrillopsis (
Worldwide distribution of species of Monstrillopsis (
Observing this adult female specimen in early June brings important new information on the distribution of monstrilloid copepods in Arctic waters as well as on their dynamics and life cycle. It also brings new information concerning the marine ecosystem of the lower Northwest Passage of the Canadian Arctic. In addition, three more observations of adult females monstrilloids were recorded during the same 2014 ICE-CAMPS campaign in Dease Strait. The specimens were collected on 07 and 29 May 2014, thus confirming that this group of copepod is consistently present in this region of the Canadian Arctic. Future work should aim to taxonomically study these three other adult females and determine if they are conspecific with M. planifrons to expand the knowledge of this species in the region or to determine if multiple species are present in the Dease Strait area.
Authors gratefully acknowledge the support by the University of Manitoba Graduate Enhancement Of Tri-Council stipends and the Natural Sciences and Engineering Research Council of Canada (NSERC) (grants to Dr. C.J. Mundy) as well as logistical support from the Canadian High Arctic Research Station (CHARS), part of Polar Knowledge Canada. This work represents a contribution to the research programs of ArcticNet, the Arctic Science Partnership (ASP), the Canada Excellence Research Chair (CERC) unit at the Centre for Earth Observation Science (CEOS) at the University of Manitoba and MEOPAR. Rosa María Hernández-Flores provided the ECO-CHZ catalog number. The comments by two anonymous reviewers were useful to improve this manuscript and are very much appreciated. We thank Dr. Danielle Defaye for the thorough and efficient editorial revision and processing of this manuscript.