Family LEUCOTHOIDAE Dana, 1852

Leucothoe commensalis

© Copyright from Barnard 1974: fig. 55.

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Introduction

The Leucothoidae is a relatively large shallow-water family of six genera and 138 species found throughout the world's oceans. The majority of species are in the genus Leucothoe. As White and Thomas (2009) point out ‘leucothoids are most often found as endocommensals in sessile invertebrates, such as sponges, ascidians, or mantle cavities of bivalve molluscs. They are found less frequently in crevices in coral rubble (Thomas & Klebba 2006, 2007)’. Leucothoids also frequently occur as free-living individuals in benthic samples. Until the work of White and Thomas (2009) on the leucothoids of the Great Barrier Reef, most of the known Australian fauna was temperate (J.L. Barnard 1972; Thomas 1997), but now there are as many tropical as temperate species. Five of the six genera and 33 species are currently known from Australian waters, about 23% of the world fauna. Based on collections in the Australian Museum and other state museums there are still many undescribed species in the Australian fauna.

Diagnosis

Head as long as or longer than deep, anteroventral margin rounded, straight or oblique, shallowly excavate or not excavate; anteroventral corner hooked or absent; rostrum short, moderate or long; eyes round, ovoid or reniform. Body laterally compressed or subcylindrical; smooth. Antenna 1 shorter than, subequal to, or longer than antenna 2; peduncular article 1 shorter than, subequal to, or longer than article 2; article 2 subequal to, or longer than article 3; article 3 shorter than article 1; accessory flagellum present or absent; primary flagellum less than or more than 5-articulate; callynophore present or absent. Antenna 2 short or medium length; flagellum shorter than peduncle; less than or more than 5-articulate. Mouthparts well developed or reduced. Mandible incisor dentate or absent; lacinia mobilis present on both sides; molar absent; palp present. Labium smooth. Maxilla 1 inner plate weakly setose apically or without setae; palp large or reduced, 1- or 2-articulate. Maxilliped inner plates reduced; outer plates small or vestigial. Coxae 1–4 longer than broad, as long as broad or broader than long, overlapping; coxa 1 anteroventrally acuminate or coxae not acuminate; coxae 1–3 with none vestigial or reduced or with coxa 1 vestigial or reduced. Gnathopod 1 not sexually dimorphic; smaller (or weaker) than or subequal to gnathopod 2; carpochelate or parachelate; coxa vestigial, hidden or partially hidden by coxa 2, or smaller than or subequal to coxa 2; carpus shorter or longer than propodus, strongly produced along posterior margin of propodus or not. Gnathopod 2 sexually dimorphic or not; carpochelate or subchelate; coxa larger than coxa 3; ischium short; carpus short, shorter or longer than propodus, strongly produced along posterior margin of propodus. Pereopod 3 coxa longer than broad, as long as broad or broader than long; carpus shorter than propodus, not produced. Pereopod 4 coxa subequal to, or larger than coxa 3, with or without posteroventral lobe; carpus shorter than propodus, not produced. Pereopod 5 shorter than or subequal to pereopod 6; coxa smaller than or subequal to coxa 4, without posterior lobe; basis expanded or slightly expanded, subrectangular or subovate, with or without posteroventral lobe; carpus linear. Pereopod 6 shorter than or subequal to pereopod 7; basis expanded or linear. Pereopod 7 subequal to, or longer than pereopod 5; basis expanded or linear, subovate. Urosomite 1 much longer than urosomite 2. Uropods 1–2 apices of rami with or without robust setae. Uropod 3 biramous; peduncle long; rami lanceolate; outer ramus shorter than peduncle; inner ramus not apically setose. Telson laminar; entire; longer than broad, as long as broad or broader than long; dorsal and apical robust setae absent.

General References

Barnard, J.L. 1972. Gammaridean Amphipoda of Australia, Part I. Smithsonian Contributions to Zoology 103: i-vi 1-333

Barnard, J.L. 1974. Gammaridean Amphipoda of Australia, Part II. Smithsonian Contributions to Zoology 139: i-v 1-148

Barnard, J.L. & Karaman, G.S. 1991. The families and genera of marine gammaridean Amphipoda (except marine gammaroids). Records of the Australian Museum, Supplement 13: 1-866

Dana, J.D. 1852. On the classification of the Crustacea Choristopoda or Tetradecapoda. American Journal of Science and Arts 2 14(41): 297-316

Lowry, J.K., Berents, P.B. & Springthorpe, R.T. 2000. Australian Amphipoda: Ampeliscidae. Version 1: 2 October 2000. http://crustacea.net.

Lowry, J.K. & Stoddart, H.E. 1986. Protandrous hermaphrodites among the lysianassoid Amphipoda. Journal of Crustacean Biology 6(4): 742-748

Thomas, J.D. 1997. Systematics, ecology and phylogeny of the Anamixidae (Crustacea: Amphipoda). Records of the Australian Museum 49: 35-98

Thomas, J.D. & Klebba, K.N. 2006. Studies of commensal Leucothoid Amphipods: Two new sponge-inhabiting species from South Florida and the Western Caribbean. Journal of Crustacean Biology 26(1): 13-22

Thomas, J.D. & Klebba, K.N. 2007. New species and host associations of commensal leucothoid amphipods from coral reefs in Florida and Belize (Crustacea:Amphipoda). Zootaxa 1494: 1-44

White, K.N. & Thomas, J.D. 2009. Leucothoidae. pp. 494-555 in Lowry, J.K. & Myers, A.A. (eds). Benthic Amphipoda (Crustacea: Peracarida) of the Great Barrier Reef, Australia. Zootaxa 2260: 1-930

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