Research Article |
Corresponding author: James Darwin Thomas ( anamixis@hotmail.com ) Academic editor: Alan Myers
© 2015 James Darwin Thomas.
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:
Thomas JD (2015) Leucothoe eltoni sp. n., a new species of commensal leucothoid amphipod from coral reefs in Raja Ampat, Indonesia (Crustacea, Amphipoda). ZooKeys 518: 51-66. https://doi.org/10.3897/zookeys.518.9340
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A new species of leucothoid amphipod, Leucothoe eltoni sp. n., is described from coral reefs in Raja Ampat, Indonesia where it inhabits the branchial chambers of solitary tunicates. With an inflated first gnathopod superficially resembling the genus Paraleucothoe, this new species has a two-articulate maxilla 1 palp characteristic of the genus Leucothoe. While described from coral reef environments in tropical Indonesia and the Philippines, it is an established invasive species in the Hawaiian Islands. The most likely mode of introduction was a US Navy dry dock transported to Pearl Harbor in 1992 from Subic Bay, Philippines.
Amphipods, coral reefs, ascidians, sponges, invasive species, model organisms, taxonomy
While leucothoid amphipods are frequently encountered in marine faunal surveys and inventories information about their invertebrate hosts is rarely known and infrequently documented. The Leucothoidae, once thought to be a cosmopolitan and widespread taxon are now known to be a highly habitat-specific species complex. Taxonomic clarity within the group has been hampered by widespread and incorrect records of Leucothoe spinicarpa (Abildgaard, 1789). Upon further analysis many of these records are now proving to be discrete species, thus diminishing the cosmopolitan concept within the group (
Because leucothoids lack a dispersive larval stage and frequently inhabit internal chambers of sessile invertebrate hosts they are potentially informative proxies for evolutionary diversity. Recent developments within the taxonomy of the Leucothoidae include: (1) availability of an electronic taxonomic database (
With their distinct morphology and common occurrence in shallow coastal marine environments, leucothoid amphipods drew the attention of early naturalists, resulting in some of the earliest recorded amphipod descriptions. While important taxonomic records, these early descriptions were often inadequately illustrated and described contributing to subsequent taxonomic confusion in the group. With increasing concerns about global climate change and loss of marine biodiversity, leucothoid amphipods are sensitive model organisms highly susceptible to a variety of toxicants and pollutants (Reish and Barnard 1969) and capable of providing a comparative diversity framework and serving as measures of change in marine ecosystems (
Currently the revised Leucothoidae (sensu stricto) comprises 176 species in five genera. This includes 42 former anamixid species in Anamixis Stebbing, 1897 (23 spp.); Nepanamixis Thomas, 1997 (4 spp.); and Paranamixis Schellenberg, 1938 (15 spp.); and 134 leucothoid species comprised of Leucothoe Leach (132 spp.), and Paraleucothoe Stebbing, 1899 (2 spp.). Species in the former anamixid genera differ from other leucothoids in exhibiting radical sexual dimorphism, eusocial and harem guarding population structure, and tropic to warm temperate distributions. Species in Leucothoe and Paraleucothoe exhibit minor to moderate sexual dimorphism, and have tropic to polar distributions. Recent 18S rDNA sequence data by
Using SCUBA and specialized underwater collecting techniques amphipods were sampled in-situ from ascidians, sponges, and bivalves throughout Raja Ampat, Indonesia. Specimens were captured in-situ directly from their host either with a modified squirt bottle or by isolating hosts and substrata underwater in plastic bags and later coercing the amphipods from the host using a small amount of freshwater or formalin in the lab.
Specimens were either fixed in 2% buffered formalin or 70% ethanol. Prior to observation, specimens were gently cleaned with small sable hair brushes, and transferred to glycerin for dissection, illustration, and analysis. For SEM analysis, specimens were rehydrated to distilled water (three fluid changes for 10 minutes each), soaked in a dilute surfactant for 15 minutes (two drops of Tween 80 in 100 ml of water), briefly sonicated (10 seconds) to remove accumulated surface debris, and re-rinsed in distilled water (three fluid changes for 10 minutes each). This preparation protocol was modified from
Figure Legend – Capital letters in figures refer to the following appendages: A = antennae, Cx = coxae, E = epimera, Hd = head, LL = lower lip, Md = mandible, N = gnathopod, P = pereopod, T = telson, U = uropod, UL = upper lip, X = maxillae.
Capital letters to the right of each caption refer to the following: L = left, R = right. Lower case letters to the left of capital letters refer to the following adjectives: l = lateral, m = medial, x = magnified. Numbers to the right of capital letters refer to specific structures. “LW” in text refers to length/width ratios. Sexes are indicated by ♂ and ♀ symbols.
Material is deposited at the National Museum of Natural History, Leiden (RMNH) and at the Zoological Museum of Bogor (MZB) Indonesian Institute of Sciences (LIPI). Additional material examined from the Bernice P. Bishop Museum (BPBM), Oahu, Hawaii, and the California Academy of Science, San Francisco, California (CASIZ).
Paraleucothoe flindersi Stebbing, 1888,
Reef slope, Yenweres Bay, Raja Ampat, Indonesia, 00° 29.216’S; 130° 40.394’E, coral reef slope, 20m.
Holotype. Male A, 8.10mm; MZB Cru Amp 003, 10 December 2007, Yenweres Bay, Raja Ampat, Indonesia, 00°29.216’S; 130°40.394’E, JDT-RajAM-46, 20m, collected in-situ from branchial baskets of Herdmania sp. tunicates, James Thomas, collector.
Paratypes. Female B, 7.35mm; male C, 7.40mm; and six additional specimens. RMNH.Crus.A.5055, 10 December 2007, Station number JDT-RajAM-46, 20m, collected in-situ from branchial baskets of Herdmania sp. tunicates, James Thomas, collector.
Male and female specimens, RMNH.Crus.A.5056, 4 December 2004, Bunaken, Sulawesi, Indonesia, 1°37.063’ N; 124°46.966’ E. Station Indo04-01c, 8.5 m, from Herdmania sp. tunicates, reef wall in front of Living Colors Dive Resort. J. Thomas, K. White collectors. BPBM S11292-293, Pearl Harbor, Oahu, Hawaii, Station 6, 16 April 1996, from the sponge Mycale grandis, USN drydock “Machinist”. CASIZ 204559, Philippines, Batangas Province, Maricaban Island, Cemetery Beach, 13°41.063N; 120°49.813E, coral rubble, 5 m., from Polycarpa tunicate, J. Thomas, collector.
The specific epithet, eltoni, in honor of the rock musician Sir Elton John. Specifically, in reference to the large shoe-like first gnathopod of this species and the oversize boots Elton John wore as the local pinball champion in the movie “Tommy” (1975).
Male holotype A. Antenna 1 and 2 short, less than 0.10 body length; maxilliped, inner margin of outer plate crenulate, palp 2-articulate; gnathopod 1, carpus and propodus greatly enlarged; carpus setose posteriorly; distal margin of propodus tumid, inflated; gnathopod 2, palm oblique with 3 concavities separated by truncate projections; pereopods 5-7, article 4 extending beyond 0.5× of article 5.
Ratios of antenna 1 and 2, 0.10 and 0.09 body length; relative lengths of antenna 1 and 2, 1.00:0.89, flagellae 8 and 6-segmented. Anterior margin of head broadly truncate; mid-ventral keel produced, anterior margin produced dorsally as small knob, tapering posteriorly, ventral margin straight.
Coxae. Coxae 1-4 width ratios, 1.00:1.87:1.37:1.40, coxa 4 posterior margin widest mid posteriorly, tapering proximally, coxa 5-6 bilobed; coxa 7 reduced, ovate.
Upper lip. Asymmetrically lobate, anterior margin setose.
Mandibles. Both lacking molars; palp 3-articulate, ratio of articles 1-3 1.00:2.50:2.60; incisors moderately dentate. Left mandible, palp articles 2-3 with 2 anterior and 2 apical setae; lacinia mobilis large, strongly toothed; 13 raker spines, two distal raker spines enlarged and modified. Right mandible, palp articles 2-3 with 13 anterior and 2 apical setae; lacinia mobilis an elongated flake; 15 raker spines.
Maxillae. 1, palp 2-articulate with four apical setae, and two rows nine and eleven facial setae; outer plate with seven apical setae and nine facial setae; inner plate small, ovate, with single apical seta. Maxilla 2: inner plate, distal margin with 6 apical setae and 6 submarginal setae, 20+ facial setae; outer plate with 5 marginal medial setae and 19 facial setae.
Maxilliped. Inner and outer plates reduced; inner plates fused, with three stout apical setae and numerous fine facial setae; outer plate, anterior one third of medial margin tuberculate; palp article 1 with several apicodistal setae on medial dorsal margin and numerous marginal setae on ventral margin; article 4 with dense row of oblique and marginal setae on both dorsal and ventral margins; article 3 apical margin and dactyl with dense covering of pubescent setae.
Gnathopod 1. Coxa lobate, LW 1.25; basis linear, LW 3.66, anterior margin serrate with 22 long setae and single posterodistal apical seta; carpus expanded, basally stout, recurved distally with sharp apex; posterior margin with approximately 49 long recurved setae along 0.18-0.94 of carpal margin and 12 short, submarginal mediofacial setae; propodus, anterior margin greatly inflated, circular, LW 1.50, posterior margin expanded, with approximately 10 short posterior setae; dactyl reduced, straight, closing medially in groove on propodus.
Gnathopod 2. Coxa oval, expanded distally, distal margin smooth, LW 0.87; article 2 linear, LW 4.00, with tuft of six long posterodistal setae; carpal lobe slender, reaching 0.32 along propodus, distal margin expanded and subtruncate, lateral margin serrate, anterior margin oblique, with 15 rows of 6-15 medial setae; propodus, palm oblique, LW 4.25 with three major and two minor projections and two major and two minor concavities, primary mediofacial setal row extending 0.76 of propodus, secondary setal row extending along posterior margin, thicker proximally; dactyl smooth, gently curved, reaching 0.70 of propodus.
Pereopods 3-4. Pereopod 3, coxa elongate ventrally, LW 1.47; basis elongate, anterodistal margin slightly produced, posterior margin with 6 submarginal setae, LW measured at midpoint 6.61; Pereopod 4, coxa distal margin rounded, ventral and posterior margins slightly excavate, posterior margin serrate with 9 small submarginal setae, LW 1.13.
Pereopods 5-7. Coxae of 5-6 bilobed; coxa 7 small, ventrally convex; pereopods 5-7 bases moderately expanded, LW 1.42:1.20:1.09, posterior margin 5-6 smooth, 7 serrate; pereopods 5-7 article four with extended posteroventral lobe reaching 0.92:0.75:0.66 of article 4.
Epimera 1-3. Ventral setae 8:4:3, posterior margins round.
Uropods 1-3. Relative uropod lengths, 1.00: 0.75: 0.77; relative lengths of peduncles 1-3, 1.00:0.84: 0.85; uropod 1, peduncle 1.07 rami length, with 11 medial and 4 lateral setae; outer ramus subequal to inner ramus, with 12 lateral and 0 medial setae, margins minutely crenulate; inner ramus with 4 medial and 5 lateral setae, margins of rami minutely crenulate; uropod 2 peduncle 0.81 rami, with 0 medial and 2 lateral setae; outer ramus 1.30 inner ramus, with 0 medial and 4 lateral marginal setae; outer ramus with 2 medial and 4 lateral marginal setae; margins of rami minutely crenulate; uropod 3, peduncle 0.93 rami, with 1 lateral apical and 5 medial setae; outer ramus 1.34 inner ramus; with 2 medial and 3 lateral marginal setae; outer ramus with 0 medial and 4 lateral marginal setae, margins of rami minutely crenulate.
Telson. LW 1.95, apical margin minutely tridentate, with 2 apical and two pairs of 2 facial setae.
7.35 mm. Similar to males except for gnathopods 1 and 2. Gnathopod 1, carpus and propodus not greatly inflated, propodus slightly swollen distally. Gnathopod 2, palm of propodus lacking distinct tuberculation and concavities found in males.
Leucothoe eltoni sp. n. most closely resembles L. tumida of
Both L. tumida and L. eltoni superficially resemble members of the genus Paraleucothoe in the large inflated gnathopod 1 of terminal males. However, Paraleucothoe differs from all species of Leucothoe in having the outer plate of the maxilliped extended distally beyond palp article 1. Paraleucothoe novaehollandiae (Haswell, 1879) also has a uniarticulate maxilla 1 palp but this feature is no longer unique to the genus as a number of recently described Leucothoe species have this feature. Paraleucothoe novaehollandiae is reported from the branchial chambers of the stalked tunicates Pyura spinifera and P. praeputialis (formerly P. stolonifera) in southern Australia waters (
Coral reefs, coral rubble, found primarily in branchial baskets of solitary tunicates such as Herdmania and Polycarpa sp., rarely in bivalve mollusks (winged pearl oyster Pteria penguin), and branched yellow rope sponges Callyspongia (species undetermined).
Indonesia: Celebes Sea, Sulawesi, Kri Island, Halmera Sea, Raja Ampat Islands. Philippines: Cape Verde Passage, Mabini Tingloy. Hawaiian Islands (invasive): Ohau to Molokai, 2–20m.
While the native range of L. eltoni sp. n. encompasses shallow coral reef habitats in Indonesian and the Philippines, it is also an established invasive in Hawaiian waters (
The author wishes to thank Dr. Bert W. Hoeksema (Naturalis Biodiversity Center) and Mrs. Yosephine Tuti (RCO-LIPI) who jointly organized the Raja Ampat (2007) expedition. The Indonesian Institute of Sciences (LIPI) granted the research permit. The research was accommodated by Papua Diving at Kri Island, Raja Ampat. Additional funding was provided to the author by a Temminck Fellowship from Naturalis Biodiversity Center, Leiden, the Netherlands, and by the Reef Foundation, Inc., USA. The author also wishes to thank Ken Longenecker and Steve Coles of the Bishop Museum, Hawaii, for first calling his attention to the presence of this species in Hawaiian waters and making museum collections available for study.
The author also thanks Terry Gosliner from the California Academy of Sciences for field support in the Philippines. Additionally, the author wishes to recognize the Philippines Department of Agriculture Bureau of Fisheries and Aquatic Resources (DA-BFAR), and the Philippines National Fisheries Research and Development Institute (NFDRI) for their regulatory and administrative support for the Verde Island Passage (VIP) project. This research was also supported by a grant from National Science Foundation DEB 12576304 PEET grant to Terrence Gosliner, Richard Mooi, Luis Rocha and Gary Williams to inventory the biodiversity of the Verde Island Passage.