Enterocola sedentarius, 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 : 227

Enterocola sedentarius sp. nov.

( Figs. 148 , 149 )

Type material. Holotype ♀ (MNHN-IU-2014-21558) and 1 ♀ paratype (dissected, MNHN-IU-2014-21475) from eypçdẚstçma deerratum (Sluiter, 1895); Papua New Guinea, CRRF coll.

Etymology. The name of the new species reflects its sedentary body form.

Description of female. Body ( Fig. 148 A-C) small, curved dorsally, appearing posteriorly truncated sedentary in lateral view ( Fig. 148C ). Body length 522 μm; maximum width 230 μm (across second pedigerous somite). Cephalic shield distinct from first pedigerous somite, 133×161 μm. Trunk obscurely segmented ( Fig. 148C ), but somites distinctly defined by deep lateral constrictions. First to fourth pedigerous somites each with well-developed tergite dorsally; tergite of first pedigerous somite simple, but those of second to fourth pedigerous somites forming paired posterolateral tergal folds ( Fig. 148A ). First to fourth pedigerous somites each with single mid-ventral interpodal protrusion ( Fig. 148B ). Genitoabdomen ( Fig. 148D ) unsegmented, much wider than long in lateral view; anal prominence large ( Fig. 148D ). Caudal rami ( Fig. 148E ) originating close to each other, directed ventrally, arising on ventral margin of genitoabdomen ( Fig. 148D ) but not articulated at base, about 1.8 times longer than wide (25×14 μm); armed with 2 or 3 minute setae. Egg sac containing 5 or 6 eggs; each egg 145 μm in diameter.

Rostrum absent. Antennule ( Fig. 148G ) 40×25 μm, unsegmented, but distinctly divisible into broad proximal part and short, narrow distal part; proximal part armed with 4 setae distally and 1 small tubercle subdistally; distal part occupying 20% length of antennule, armed with 3 setae on distal margin. Antenna ( Fig. 148H ) incompletely 2- segmented, about 2.1 times longer than wide; proximal segment unarmed; distal segment armed with 6 large setae, lengths of setae I-VI (medial to lateral) increasing 19, 32, 34, 36, 48, and 61 μm, respectively; setae IV-VI longer than width of segment at tip.

Labrum ( Fig. 148I ) broad with convex lateral margins, ornamented with patches of minute spinules on ventral surface; palp spinulose, curved laterally, with narrow proximal quarter and moderately expanded distal three-quarters. Mandible spinulose, narrower than labral palp. Precoxa ( Fig. 148J ) of maxillule with bifurcate apex, and endite bearing slender, spinulose spine and more than 10 thin spinules; palp ( Fig. 148K ) armed with 6 subequal spinulose spines along convex distal margin. Maxilla ( Fig. 148L ) 2-segmented; proximal segment bearing 1 smooth tubercle proximally on medial margin and mediodistal endite tipped with spinulose element; distal segment smooth, tapering, with 1 tubercle on anterior surface and 1 seta on posterior surface. Maxilliped absent.

Legs 1-4 each consisting of 2-segmented protopod (coxa and basis) and unsegmented rami ( Fig. 149A, B ); basis with outer seta. Exopods with proximal patch of spinules on lateral margin. Endopods less than twice as long as wide, 31×21, 31×20, 31×18, and 25×15 μm, respectively, in legs 1-4. Distal setae on endopods distinctly longer than endopodal segments. Laterodistal and mediodistal setae 67 and 59, 71 and 56, 42 and 42, and 40 and 33 μm, respectively, in legs 1-4. Laterodistal setae distinctly longer than mediodistal setae in legs 1, 2, and 4, but equal in length in leg 3.

Leg 5 ( Fig. 149C ) more than twice as wide as long (63×150 μm); armed with 2 minute setae on distal margin; separated by distance of 87 μm.

Male. Unknown.

Remarks. The posteriorly-truncated body, with its ventrally directed abdomen, is an extraordinary body form for the genus bnterçcçla, and serves to characterize bK sedentarẚus sp. nov. In addition, about half of known congeneric species have a laterodistal seta on the endopod of leg 1 that is as long as or longer than the endopodal segment, but in none of these is the laterodistal seta more than twice as long as the endopodal segment as in b. sedentarẚus sp. nov.

The caudal rami of b. sedentarẚus sp. nov. are armed with 2 or 3 setae. Although the setae are minute, this feature is remarkable because caudal rami of bnterçcçla species that are known to be setiferous, i.e. b. ẚanthẚnus, b. latẚceps, and b. setẚcaudus sp. nov., only ever have a single caudal seta. The antennules of b. sedentarẚus sp. nov. are armed with 7 setae ( Table 6 ). This setation is shared with three known species, b. sydnẚẚ, b. setẚcaudus sp. nov., and b. australẚs sp. nov. but none of these species shares the ventrally-directed abdomen that is diagnostic for b. sedentarẚus sp. nov.

Figures

FIG. 148. bnterçcçla sedentarẚus sp. nov., female. A, habitus, dorsal; B, habitus, ventral; C, habitus, left; D, genitoabdomen, left; E, caudal rami; F, egg sac; G, antennule; H, antenna; I, labrum; J, precoxa of maxillule; K, palp of maxillule; L, maxilla. Scale bars: A-C, F, 0.1 mm; D, H, L, 0.02 mm; E, G, I-K, 0.01 mm.

FIG. 149. bnterçcçla sedentarẚus sp. nov., female.A, leg 1; B, leg 3; C, leg 5. Scale bars: A, B, 0.02 mm; C, 0.05 mm.