Mychophilus hesperius, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 281-283

Mychophilus hesperius sp. nov.

( Fig. 185 )

Type material. Holotype ♀ (MNHN-IU-2014-21590), 1 ♀ paratype (MNHN-IU-2014-21591), and 1 ♀ paratype (dissected, MNHN-IU-2014-21485) from Symplegma brakenhẚelmẚ (Michaelsen, 1904) (MNHN-IT-2008-8440 = MNHN S1 / SYM/12 ); Saint François, côte sud de Grande Terre, Guadeloupe, Stn 18 (dive from quay of fishing port), Monniot coll., 25 December 1980.

Etymology. The name is derived from the Greek hesper (=western), referring to its collection from the West Indies.

Description of female. Body ( Fig. 185A ) vermiform, cylindrical, unsegmented, curved dorsally. Body length 1.80 mm; maximum width 327 μm (at level of leg 4). First to fourth pedigerous somites obscurely defined by weak lateral constrictions. Genital apertures positioned laterally at 70% of body length. Anus positioned dorsally at 60% of body length (between level leg 4 and genital apertures). Region of genitoabdomen gradually narrowing posteriorly. Posterior part of body ( Fig. 185B, C ) lobate, bearing rudimentary caudal rami dorsally; each caudal ramus about 1.8 times longer than wide (9×5 μm), tipped with 1 small, broad seta, 9 μm long.

Rostrum absent. Antennule ( Fig. 185D ) small, 2-segmented; proximal segment unarmed; distal segment slightly shorter and narrower than proximal segment; armed with 5 setae (1 proximal, 2 subdistal, and 2 distal). Antenna ( Fig. 185E ) 2-segmented; proximal segment unarmed, bearing 2 triangular processes at laterodistal corner; distal segment small, claw-like, obscurely articulated from proximal segment.

Labrum ( Fig. 185F ) broad, bearing 4 spinulose processes (medial pair shorter than lateral pair). Mandible absent. Maxillule ( Fig. 185G ) bilobed; longer inner lobe bearing 2 attenuated processes; shorter outer lobe bearing 1 broad, blunt process and 1 shorter, thin, setiform process. Maxilla ( Fig. 185H ) lobate, bearing 2 lobules subdistally, medial lobule tipped with 1 small seta, and ornamented with 2 groups (4 proximal and 3 distal) of spinules on medial margin. Maxilliped absent.

Leg 1 ( Fig. 185I ) consisting of 2-segmented, unarmed protopod and rudimentary rami. Protopod ornamented with scattered spinules on anterior surface. Exopod claw-like, articulated from distal segment of protopod; endopod not articulated at base, fleshy, with blunt tip. Legs 2-4 same as leg 1. Legs 5 and 6 absent.

Male. Unknown.

Remarks. Mychçphẚlus hesperẚus sp. nov. can be differentiated from most of its congeners by the possession of 4 processes on the labrum. The exception is M. fallax, for which the labrum is unknown. However, MK fallax is not confusable with the new species because it carries a simple inner lobe and has 3 setiform elements on the outer lobe of the maxillule, and has an unsegmented maxilla ( Stock, 1967). Mychçphẚlus hesperẚus sp. nov. bears 2 processes on the inner and outer lobes of the maxillule. This is a unique feature of M. hesperẚus sp. nov., which alone serves to characterize the species.

Discussion. Prior to this study, these four families collectively contained a total of 118 valid species classified in 15 recognized genera ( Walter & Boxshall, 2020). Here we have added five new genera and 84 new species, taking the totals to 20 and 202, respectively. In common with previous studies of archinotodelphyid ( Kim & Boxshall, 2020a) and notodelphyid copepods ( Kim & Boxshall, 2020b) from the Monniot collection, this represents a dramatic increase in the documented species richness of the families. All three of these papers serve to emphasise the enormous gaps in our knowledge of the parasites and symbionts of marine invertebrate hosts. In order to better quantify the diversity of marine ecosystems and better understand energy flow through these systems, considerably more effort must be invested in collecting and describing symbiotic species.

Figures

FIG. 185. Mychçphẚlus hesperẚus sp. nov., female. A, habitus, right; B, distal part of body, dorsal; C, distal part of body, right; D, antennule; E, antenna; F, labrum; G, maxillule; H, maxilla; I, leg 1. Scale bars: A, 0.2 mm; B, C, I, 0.02 mm; D-H, 0.01 mm.