Enterocola parvus, 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 : 216-219

Enterocola parvus sp. nov.

( Figs. 140 , 141 )

Type material. Holotype ♀ (MNHN-IU-2014-21552), 2 ♀♀ paratypes (MNHN-IU-2014-21553), and 1 ♀ paratype (dissected, MNHN-IU-2014-21483) from aẚdemnum psammatçdes (Sluiter, 1895); Iles Mesha, Djibouti, intertidal, Monniot coll., 13 October 1996.

Etymology. The specific name is derived from the Latin parv (=small), alluding to the small body size of the new species.

Description of female. Body ( Fig. 140 A-C) small, unsegmented, curved dorsally; body length 560 μm; maxi- mum width 200 μm (across cephalosome). Cephalosome partly covered by cephalic shield, wider than trunk, with semicircular median tubercle posterodorsally. First to fourth pedigerous somites each with well-developed dorsolateral tergal folds ( Fig. 140A ) and single, broad mid-ventral interpodal protrusion between left and right legs ( Fig. 140B ). First pedigerous somite with large median tubercle dorsally between left and right tergal folds ( Fig. 140A ), as on cephalosome but larger. Genitoabdomen ( Fig. 140D ) short, dorsally unsegmented, but ventrally 3-segmented; anal prominence distinct. Caudal rami unarmed, incompletely articulated from abdomen, originating close to each other; each ramus ( Fig. 140E ) fusiform, widest in middle, about 2.1 times longer than wide (42×20 μm), with rounded distal margin.

Rostrum absent. Antennule ( Fig. 140F ) bulbous, 1.2 times longer than wide (34×28 μm), with narrow proximal part and strongly convex posterior margin; armed with 3 small setae distally. Antenna ( Fig. 140G ) about twice as long as wide, unsegmented, but with rudimentary partial suture line in middle of lateral margin; ornamented with minute spinules on distal half of concave surface; armed with 6 small setae, at most as long as half width of segment; lengths of setae I-VI (medial to lateral) 15, 11, 11, 13, 12, and 22 μm, respectively; setae II and III, and setae IV and V close to each other.

Labrum ( Fig. 140H ) with distally expanded, bulbous palps. Mandible ( Fig. 140H ) tapering, narrower than labral palp. Maxillule consisting of precoxa and palm-shaped palp: precoxa ( Fig. 140I ) with blunt, sclerotized distal part, 1 tubercle subdistally, and endite near middle; endite tipped with 1 spinulose spine and more than 10 long, stiff setules: palp ( Fig. 140J ) with 5 spinulose spines on distal margin (medial spine shortest), and 1 naked seta on lateral margin. Maxilla ( Fig. 140K ) massive, 2-segmented; proximal segment with 1 spinulose tubercle proximally on medial margin and 1 large mediodistal, spinulose process; distal segment bluntly tipped, with subdistal spinulose process, 1 transverse row of minute spinules in middle of anterior surface, and 1 small seta proximally on posterior surface. Maxilliped absent.

Legs 1-4 each with 2-segmented protopod and unsegmented rami ( Fig. 141 A-C); protopods unarmed. Exopods of legs 1, 2, and 4 shorter than endopods, tipped with small cusp; exopod of leg 3 as long as endopod ( Fig. 141B ), acutely attenuated distally. Endopods 36×18, 36×21, 51×23, and 39×21 μm, respectively, in legs 1-4. Laterodistal and mediodistal setae on endopods distinctly shorter than endopodal segments, 27 and 24, 25 and 20, 29 and 23, and 28 and 20 μm, respectively, in legs 1-4. Length ratios of laterodistal to mediodistal setae, 1.13, 1.71, 1.26, and 1.40, respectively, in legs 1-4.

Leg 5 ( Fig. 140L ) unarmed, wider than long (82×132 μm).

Male. Unknown.

Remarks. In b. parvus sp. nov. the antennule is unsegmented and armed with relatively few setae (less than 5), the antenna is armed with 6 setae, and the distal setae on the endopods of legs 1-4 are distinctly shorter than endopodal segments. This combination of features is shared only with three other species: b. dẚcaudatus, b. mammẚferus, and b. rçbustus sp. nov. These three congeners can be readily distinguished from b. parvus sp. nov. by distinctive character states. In b. dẚcaudatus the antenna is elongate (with its setae positioned subterminally), the genitoabdomen bears a large ventral process, the cephalic shield carries a posterodorsal process, and the distal setae on the endopods of legs 1-3 are very small (less than one-third of the length of the endopods) ( Marchenkov & Boxshall, 2005). In b. mammẚferus the caudal rami are short (wider than long), the antennule is tapering, the 6 setae on the antenna are subequal in length, and the first to fourth pedigerous somites each bear a pair of ventral interpodal protrusions ( Ooishi, 2010b). In b. rçbustus sp. nov. the body is robust, the caudal rami are 3 times longer than wide, setae IV and V of the antenna are separated from each other, and the mediodistal process on the proximal segment of the maxilla is slender.

The presence of the two dorsal tubercles each on the cephalosome and on the first pedigerous somite is a characteristic feature of b. parvus sp. nov. Similar tubercles are present in b. quadrẚseta sp. nov., but in this species the tubercles are located on the second and third pedigerous somites.

Figures

FIG. 140. bnterçcçla parvus sp. nov., female.A, habitus dorsal; B, habitus, ventral; C, habitus, right; D, genitoabdomen, right; E, caudal ramus; F, antennule; G, antenna; H, labrum and mandibles; I, precoxa of maxillule; J, palp of maxillule; K, maxilla; L, leg 5. Scale bars: A-C, 0.1 mm; D, E, G, K, 0.02 mm; F, H-J, 0.01 mm; L, 0.05 mm.

FIG. 141. bnterçcçla parvus sp. nov., female. A, leg 1 and interpodal protrusion; B, leg 3 and interpodal protrusion; C, leg 4 and interpodal protrusion. Scale bars: 0.02 mm.