A new species of Leucothoid Amphipod, Anamixis bananarama, sp. n., from Shallow Coral Reefs in French Polynesia (Crustacea, Amphipoda, Leucothoidae)

Abstract Both leucomorph and anamorph developmental stages of Anamixis bananarama sp. n., are illustrated and described from shallow back reef environments of Moorea, French Polynesia. Distinguished by vestigial first gnathopods that persist in post-transformational adult males, this is the second species in the genus to exhibit this unusual character. In other features such as coxae and second gnathopods Anamixis bananarama sp. n. resembles other Pacific Plate endemics of Anamixis known from the region. Specific host association is not documented but suspected to be small calcareous asconoid sponges associated with coral rubble.


Introduction
Leucothoid amphipods are of interest for their unusual ecology as commensal inhabitants of sessile invertebrates such as sponges, sea squirts, and bivalves. Obligate commensal species have evolved highly characteristic and unusual morphologies and feeding strategies as a consequence of their way of life, including eusocial structure, a condition once thought limited to insects and naked mole rats. Duff y (1996,2003) fi rst documented eusocial behavior in marine sponge-inhabiting snapping shrimp. Th omas (1983Th omas ( , 1997 documented eusociality and communal living in highly derived tropical leucothoids in the genus Anamixis. Th iel (1999) reported on nest guarding in Leucothoe spinicarpa from Florida, USA. Because of their cryptic lifestyle and need for specialized collecting methods, leucothoid diversity has been vastly underrepresented in museum collections. Specialized in-situ underwater collecting techniques pioneered by the fi rst author are beginning to reveal the extent of leucothoid diversity (Th omas, 1997, Th omas and Klebba, 2006, 2007White and Th omas, 2010). Th e 22 species in genus Anamixis Stebbing, 1897, are primarily tropical -warm temperate in distribution. Th eir greatest diversity is in the Pacifi c with 14 species, followed by the Indian Ocean with fi ve species, and the Caribbean Sea and Western Atlantic with four species. Further specialized collecting of host and symbiont will undoubtedly signifi cantly expand the addition of new taxa in the Leucothoidae.

Methods
Specimens were collected by snorkeling and SCUBA. Rubble and other shallow algal substrates were isolated in-situ and processed by elutriation. In the lab juvenile (leucomorph) and adult males (anamorphs) were separated and photographed using AutoMontage © . Specimens were fi xed in 100% ETOH for molecular analysis and in 2% buff ered formalin for dissection and illustration. Type material is deposited in the collections of the Florida Museum of Natural History in Gainesville, Florida with the prefi x "UF" for museum numbers. Diagnosis. Terminal anamorph males: Eyes with 7 scattered ommatidia; gnathopod 1 greatly reduced, shriveled, persisting in post-transformational stages. Gnathopod 2, basis greatly elongated, narrow; carpus elongate, apically blunt, with reduced setal tufts on medial margin; propodus with sparse mediofacial setal row. Telson elongate for genus, 1.72 times longer than wide.
Etymology. Th is species is named for the long recurved carpal lobe on the second gnathopod that resembles the shape of a banana.
Relationships. Anamixis bananarama shares it closest affi nity with A. jebbi from the Madang Lagoon, Papua New Guinea, (Th omas, 1997), with both species having 7 ommatidial facets in both leucomorph and anamorph stages, and a reduced, vestigial fi rst gnathopod in the post transformational anamorph stage. Th e second gnathopod of A. bananarama diff ers from A. jebbi in the elongate basis, the more blunt and less setose carpus, and reduced mediofacial setal row (7 in A. bananarama; 14 in A. jebbi). A. bananarama exhibits an elongated telson typical of ratios found in Nepanamixis (Th omas, 1997). Both A. jebbi and A. bananarama show transitional characters placing them in a clade by themselves with the elongate telson of A. bananarama placing it nearer to Nepanamixis in this regard. Th e telson of A. bananarama at 1.70 times longer than wide exceeds that of A. jebbi at 1.32 and approaches the telson ratios typical of the genus Nepanamixis at 1.8-2.0 times longer than wide.
Remarks. Color in life and in freshly collected and preserved material of both leucomorph and anamorph stages are pale translucent pink. Th ere is faint thin reddish banding on posterior thoracic and abdominal segments. Eyes are red. Ovigerous females contain an average of 7-10 yellow eggs in the marsupium.
Th e vestigial fi rst gnathopods found in A. bananarama and A. jebbi are persistent morphologies in post transformational anamorphs in both taxa. A number of specimens were examined by the fi rst author to ensure these were not transitional transformational features as reported by Th omas (1997) in Paranamixis clarkae from the Seychelles Islands. In P. clarkae, transformational anamorphs exhibit small shrunken vestiges of gnathopod 1 which are lost in subsequent molts. Ren (2006) described P. vestigium from the South China Sea, illustrating similar reduced fi rst gnathopods. In all other aspects P. vestigium resembles P. misakiensis described by Th omas (1997) from Japan and examination of a series of anamorph specimens of P. vestigium is needed to resolve whether these vestigial fi rst gnathopods persist in post-transformational molts.
Habitat. Specifi c habitat/host undocumented but assumed to be small asconoid calcareous sponges in protected rubble habitats in backreef environments.