Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species Author Kim, Il-Hoi m@gwnu Author Boxshall, Geoff A. m@gwnu text Zootaxa 2021 1 1 286 journal article 10.11646/zootaxa.4978.1.1 1175-5326 4820443 9C7C1723-73EB-4FBE-A47A-54627DEB8F93 Haplostoma rectangulatum sp. nov. ( Fig. 91 ) Type material. Holotype ♀ (MNHN-IU-2009-5230) and 1 ♀ paratype (dissected, MNHN-IU-2014-17382) from mçlysyncratçn sp.; off Libanona , Sud Madagascar , ATIMO VATAE Expedition, Stn TR 01 ( 25°00.25´S , 46°59.4´E ), depth 9 m , MNHN coll., 28 April 2010 . Additional material. 1 ♀ (MNHN-IU-2009-5232) in mçlysyncratçn sp., Port Dauphin , Madagascar , ATIMO VATAE expedition, Stn TR 03 ( 25°0.08´S , 47°0.01´E ), depth 21 m , 29 April 2010 . Etymology. The name of the new species refers to its rectangular abdomen. Description of female. Body ( Fig. 91A, B ) eruciform, cylindrical, slightly curved dorsally, consisting cephalosome, indistinctly 5-segmented metasome, and small 2-segmented genitoabdomen. Body length 940 μm; maximum width 290 μm across fourth pedigerous somite. Cephalosome 175×210 μm, narrower than first pedigerous somite; second to fourth pedigerous somites nearly equal in width, each wider than first. Fourth and fifth pedigerous somites demarcated from each other by dorsal and ventral constrictions. Genitoabdomen ( Fig. 91C ) small, 105×120 μm, occupying only 11% of body length, consisting of triangular anterior somite bearing genital apertures dorsally, and narrow, rectangular free abdomen (posterior somite); free abdomen clearly defined from anterior somite due to abrupt narrowing, longer than wide (39×27 μm). Caudal rami absent, but 1 caudal seta may be present on postero- lateral corner of free abdomen ( Fig. 91D ). Rostrum absent. Antennule ( Fig. 91E ) as small, unsegmented lobe, 24×17 μm, bearing patch of small spinules (or setae?) on apex. Antenna ( Fig. 91F ) stout, 3-segmented; first segment broad but very short and unarmed; second segment longest, unarmed; terminal segment slightly longer than wide, armed with 4 bifurcate spines; spines becoming gradually larger from proximal to distal. Labrum ( Fig. 91G ) simple, unornamented, with broad distal lobe. Mandible ( Fig. 91G ) vestigial, represented by pair of weak unarmed tubercles, located lateral to labrum. Maxillule and maxilla absent. Maxilliped ( Fig. 91H ) stout, very small, 4-segmented; all segments wider than long; proximal 3 segments unarmed; distal segment bearing unequally bifurcate terminal claw. Legs 1-4 consisting of protopod and exopod; endopod not discernible; exopods armed only with spines (lacking seta), incompletely articulated from protopod. Exopod of leg 1 ( Fig. 91I ) armed with 5 bifurcate spines and ornamented with spinules near base of each spine. Leg 4 ( Fig. 91J ) slightly larger than leg 1, armed with 4 bifurcate spines and ornamented as in leg 1. Legs 2 and 3 same as leg 4 in shape and armature. Leg 5 ( Fig. 91K ) as conical fleshy process on fifth pedigerous somite, directed posterodorsally, bearing 2 small setae (1 dorsal and 1 distal). Leg 6 ( Fig. 91L ) represented by 1 small spine and 1 spiniform process on genital operculum. Four dentiform elements present near leg 6. Male . Unknown. Remarks. Ooishi (2009b) recognized seven species of eaplçstçma as “subgroup 2”. In one member of this group, e . bẚspẚnçsum Ooishi, 2009, the exopods of legs 1-4 are armed with 5, 4, 5, and 5 spines (5-4-5-5 pattern), respectively. The other six species of this group all display a 5-4-4-4 pattern for legs 1-4, in common with e . rectangulatum sp. nov. However, only one of these six species, e . dudleyae Ooishi, 1998 , is comparable with the new species in having a single caudal seta and a vestigial mandible lacking any setal elements. Ooishi (1998) described eK dudleyae on the basis of material from Florida , USA and it has a leg 5 represented only by a pair of setae. In contrast, leg 5 of e . rectangulatum sp. nov. is well-developed, being represented by a distinct fleshy process bearing 2 setae. eaplçstçma dudleyae also has caudal rami, although they are small and lobate, while e . rectangulatum sp. nov. lacks defined caudal rami. The latter feature of the new species is unique within the genus. Collectively these differences justify the establishment of the new species.