Janstockia dasicephala, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 616-619

Janstockia dasicephala sp. nov.

( Figs. 417 , 418 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21442 ) from Eudistoma murrayi (Kott, 1957) (MNHN-IT-2008-4123 = MNHN A3/EUD/162), CRRFOCDN 3757-S, Pemba, Tanzania (5°23.45’S, 39°37.86’E), depth 18 m, 29 January 1996.

Etymology. The specific name is derived from the Greek das (=hairy) and cephala (=head), alluding to the dense hair-like ornamentation covering the cephalosome of the new species.

Descriptionoffemale. Body ( Fig. 417A ) vermiform, cylindrical, consistingof cephalosome, metasome, and small abdomen. Bodylength 4.36 mm. Cephalosome ( Fig. 417B, C ) 509×655 μm, demarcated from trunk by constriction; surface of anterior half setulose, posterior half of cephalosome laterally expanded and densely ornamented with broad band of setules. Metasome maximum width 0.51 mm, entire metasome forming brood pouch, strongly recurved dorsally; surface sparsely setulose except anteriorly where more dense setules present at level of leg 1 ( Fig. 417B ). Pair of tubercles present on ventral surface of metasome just anterior to base of first legs ( Fig. 417C ). Legs 1–4 separated from one another by intervals of 0.32, 0.77, and 1.40 mm; distance from leg 4 to posterior margin of abdomen 1.50 mm. Posterior end of metasome incorporating genital somite, narrow, with copulatory pore on ventral surface ( Fig. 417F ). Abdomen ( Fig. 417E, F ) small, unsegmented, widerthan long(102×186μm)demarcatedfrom metasome by furrow dorsally ( Fig. 417E ) and by 2 or 3 indistinct folds ventrally ( Fig. 417F ). Posterior margin of abdomen weakly bilobed with median anal slit, caudal rami not delimited, represented by 6 minute caudal setae on each posteriormargin lobe ( Fig. 417G ).

Rostrum ( Fig. 417C, D ) longerthanwide, tapering towards rounded apex. Antennule ( Fig. 418A ) 2- segmented, consisting of expanded first segment (79×74 μm) bearing 23 setae +1 aesthetasc, and smallsecond segment (22×22 μ) armedwith 10 setae + 2 aesthetascs; setae crowded, small and naked. Antenna ( Fig. 418B ) extremely stout, 3-segmented; coxa and basis unarmed; unsegmentedendopod about 1.6 timeslongerthan wide (44×28 μm), with trace of articulation in middle; armed with 3 small setae distally plus short, stout terminal claw, articulated from endopod.

Labrum ( Fig. 417D ) small and tapering. Mandible ( Fig. 418C ), maxillule ( Fig. 418D ), maxilliped (third pair of mouthparts; Fig. 418E ) each represented by small lobe, bearing 4 setae, 5 setae (1 small, 4 large), and 1 seta, respectively. Small bimerous tubercle ( Fig. 418F ) present in ventral midline posterior to mouthparts ( Fig. 417D ).

Leg 1 ( Fig. 418G ) biramous with indistinctly 2- segmented protopod and 3-segmented rami, although articulation between first and second segments of both rami indistinct. Coxa ornamented with spinules on ventral surface; basis bearing outer seta. First endopodal segment broadened, with 1 smallseta at innerdistal corner. Third segment of both rami much narrower than proximal segments. First and second exopodal segments and second endopodal segment unarmed. Third segment of exopod and endopod armedwith 7 and 5 (or 6) small setae, respectively. Second exopodal segment and first and second endopodal segments ornamented with patches of spinules.

Leg 2 ( Fig. 418H ) consistingof unsegmented protopod, unsegmented exopod, and small, indistinctly 2-segmented endopod. Protopod with outer seta. Exopod indistinctly demarcated from protopod, tapering, with sclerotized, claw-like process and 3 setae. Endopod with 1 inner seta on first segment and 5 distal setae on second; all setae on rami minute. Leg 3 shaped as leg 2, but with only 4 setae on second endopodal segment. Leg 4 also shaped as leg 2, but with 6 setae on second endopodal segment. Leg 5 absent.

Male. Unknown.

Remarks. In the absence of anterolateral wings on the metasome, the lack of the inner distal seta on the basis of leg 1, and of any globularly expanded setae on the maxillule, Janstockia dasicephala sp. nov. is more similarto J. clavelinae sp. nov. than to J. phallusiella and J. truncata . However, J. dasicephala sp. nov. can be differentiated from J. clavelinae sp. nov. and other congeners by five outstanding features, as follows: (1) the posterior half of the cephalosome is expanded and its surfaceis denselycoveredwith setules, (2) the antennuleis distinctly 2-segmented and consists of a swollen first and small second segment, (3) the maxilliped is represented by a small lobe tipped with a seta, (4) a single, bimerous tubercle is present on the ventral midline posterior to the mouthparts, and (5) leg 1 lacks any claw-like process on the exopod. These differences are sufficient to justify the establishment of the new species.

Figures

FIGURE 417. Janstockia dasicephala sp. nov., female. A, habitus, right; B, cephalosome, dorsal; C, cephalosome and leg 1, ventral; D, antennal and oral region, ventral; E, urosome, dorsal; F, urosome, ventral; G, distal margin of urosome, showing caudal setae. Scale bars: A, 0.5 mm; B–F, 0.1 mm; G, 0.01 mm.

FIGURE 418. Janstockia dasicephala sp. nov., female. A, antennule; B, antenna; C, mandible; D, maxillule; E, third mouthpart; F, post–oral protuberance; G, leg 1; H, leg 2. Scale bars: A, B, D–H, 0.02 mm; C, 0.01 mm.