PERACARIDA CALMAN, 1904

Jaume, Damià, Boxshall, Geoff A. & Bamber, Roger N., 2006, A new genus from the continental slope off Brazil and the discovery of the first males in the Hirsutiidae (Crustacea: Peracarida: Bochusacea), Zoological Journal of the Linnean Society 148 (2), pp. 169-208 : 171

SUPERORDER PERACARIDA CALMAN, 1904 ORDER BOCHUSACEA GUTU & ILIFFE, 1998

Emended diagnosis

Body comprising cephalothorax incorporating only first thoracomere (bearing maxillipeds), pereon composed of seven somites, pleon of five somites, and pleotelson comprising sixth pleonite plus telson. Anus opening terminally on pleotelson. Dorsal cephalothoracic shield with post-mandibular area of lateral margin produced ventrally on each side into paired rounded lappets covering bases of maxillules through maxillipeds; lappets apparently articulating with cephalothoracic shield; mandibular gnathobase completely exposed. Posterior carapace fold lacking. Eyes and eyestalks lacking.

Antennule with three-segmented peduncle and two flagella. Antenna located on well-defined pedestal, biramous, with two-segmented protopod, foursegmented endopod with terminal segment annulated forming flagellum, and marginally setose exopodal scale on second protopodal segment (basis). Lacinia mobilis present on left mandible only. Paragnaths drawn out distally into long, filiform extension. Maxillule bilobate, with lobes representing coxa and basis; rami lacking. Maxilla retaining vestige of endopod as non-articulated process carrying long seta; maxillary gland present, opening posterolaterally on basal pedestal of maxilla. Maxilliped lacking both coxal endite and epipodite.

Pereopods all with monocondylic articulation between coxa–basis, and with basis–endopodal intersegmental articulations all dicondylic with hinge lines perpendicular to limb plane except articulation between merus and carpus, which lies parallel to it. Distal endopodal segments lacking annulations. Pereopods 1–6 biramous, with plumose, locomotory exopods originating anterolaterally on proximal part of basis. Pereopod 1 unspecialized, non-chelate, probably assisting in manipulation of food. Pereopod 2 stouter than rest, apparently fossorial. Oostegites on female pereopods 2–6, located posteromedially on coxa, fringed with long plumose setae; oostegites apparently permanent once developed. Male penes paired, tubular.

Pleopods vestigial in female; well developed, locomotory in male, comprising protopod and onesegmented stenopodial rami except modified pleopod 2, with two-segmented exopod and inflated, one-segmented endopod. Uropods biramous, with undivided protopod and stenopodial, non-foliaceous rami; exopod two-segmented, endopod annulated, apparently five-segmented, but lack of intrinsic musculature suggesting one-segmented condition.

Life cycle including manca stage. Reproductive strategy involving non-feeding terminal males.

Composition

The order comprises three genera from two very different habitats: the oceanic bathyal floor, and marine and anchialine caves. Hirsutia , with two species, is a bathyal form reported from the South Pacific off Australia and the western Atlantic off Guayana. Thetispelecaris , with also two species, is known only from caves in the Bahamas and the Cayman Islands. Montucaris gen. nov. lives in the northern South Atlantic on the continental slope, off Brazil.

Remarks

Gutu (2001) emended his original diagnosis of the Bochusacea after noticing that Thetispelecaris remex has the second thoracomere incorporated into the cephalothorax. We have confirmed this in the three adult female and one juvenile paratypes deposited in the National Museum of Natural History (Smithsonian Institution, Washington; Reg. No. USNM 291178). Nevertheless, we interpret this feature as an autapomorphy of the species as this somite is completely separated from the cephalothorax in T. yurikago and in all members of the other genera.

All previous descriptions of hirsutiid species have reported the presence of a free telson. Just & Poore (1988) showed what appears to be a well-defined ventral articulation between the sixth pleonite and telson, but other authors figured only a faint line in the homologous position. Ohtsuka et al. (2002: fig. 6a–d) and Gutu (2001: fig. 2a,b) show scanning electron micrographs of that part of the body, but these photographs are inconclusive and do not confirm the presence of a ventral articulation. The new taxon described herein possesses a pleotelson: there is no suture line marking the plane of articulation between sixth pleonite and telson on the ventral body surface and there is no indication of an articulation reflected in the ventral longitudinal trunk musculature. In addition the mid-dorsal suture line separating the sixth pleonite from the telson is non-functional, lacking any arthrodial membrane. A similar situation has been described for some anthurid isopods, which have traditionally been considered to be the exception within the Isopoda with regard to the presence of a pleotelson ( Brusca & Wilson, 1991).