Parahesiocaeca Uchida, 2019

Hiro, Uchida, omi, Lopéz, Eduardo & Sato, Masanori, 2019, New Hesionidae (Annelida) from Japan: Unavailable Names Introduced by Uchida (2004) Revisited, with Reestablishment of their Availability, Species Diversity 24, pp. 69-95 : 88

Genus Parahesiocaeca Uchida , gen. nov

Parahesiocaeca Uchida, 2004: 76 (nomen nudum, without type species fixation); Ruta et al. 2006: 101.

Diagnosis. Prostomium rectangular, with three antennae, biarticulated palps, and two pairs of eyes; without facial tubercle. Proboscis without jaws but with marginal papillae with ciliated tips. First two segments tentacular, achaetous; bearing four pairs of tentacular cirri with distinct cirrophores. Parapodia sub-biramous. Tentacular and dorsal cirri articulated. Neuropodia with long prechaetal lobe, short postchaetal lobe, and short ventral cirrus; all neurochaetae heterogomph falcigers, with hooked tip and fine serration. Pygidium without anal membrane.

Type species. Parahesiocaeca japonica sp. nov., fixed by original designation.

Gender. Feminine.

Etymology. The genus is named after the genus Hesiocaeca Hartman, 1965 , because of their resemblance.

Remarks. Up to now, four known genera have four pairs of tentacular cirri in the family: Struwela , Heteropodarke , Hesiocaeca , and Bonuania Pillai, 1965 . However, the new genus possesses median antenna and palps, which are lacking in Struwela , and lacks modified claw-shaped chaetae in anterior segments. Heteropodarke species show a variable number of tentacular cirri, which include four pairs as in Parahesiocaeca gen. nov., but the new genus lacks the stout compound chaetae present in all the species of Heteropodarke . Parahesiocaec a gen. nov. differs from Bonuania in the lack of facial tubercle and the presence of lateral antennae. The new genus is very similar to Hesiocaeca because both have three antennae and paired palps; however, Parahesiocaeca gen. nov. lacks facial tubercle, whereas Hesiocaeca bears this structure.

Parahesiocaeca japonica Uchida , sp. nov. [New Japanese name: Yotsu-de-otohime] ( Fig. 16 )

Parahesiocaeca japonica Uchida, 2004: 77–79 , fig. 19 (unavailable specific name, without explicit fixation of name-bearing types).

Type material. Holotype: (NSMT-Pol H-761), Arita, Kushimoto, Kii Peninsula , Wakayama Prefecture (33°28′41″N, 135°44′2″E), lobster gillnet, 30 m depth, coll. K. Ikazaki, 7 February 1979. Two paratypes: (NSMT-Pol P-762), data as for holotype.

Diagnosis. Holotype 1.75 mm long for 20 chaetigers ( Fig. 16A ), body colorless. Lateral antennae as long as prostomium; median antenna half as long as lateral ones; palps biarticulated, as long as lateral antennae; two pairs of orange eyes, anterior ones larger; facial tubercle absent ( Fig. 16B, C ). Proboscis without teeth or jaws, with 18 papillae located on distal margin ( Fig. 16B ). First two segments achaetous, with two pairs of tentacular cirri ( Fig. 16A–C ). Parapodia sub-biramous, long ( Fig. 16E–G ). Dorsal cirri extending beyond chaetal tips ( Fig. 16G ); cirrophores long, without constriction and supported by two slender aciculae ( Fig. 16H ), cirrostyle annulated ( Fig. 16E, G ). Neuropodial lobes with single acicula with rounded tip ( Fig. 16I ) and compound chaetae bearing serrate blades, all similar in shape ( Fig. 16J–L ).

Etymology. Named from Japan, the country where the type specimens were found.

Remarks. The detailed description and drawings of the type materials were presented in Uchida (2004). Parahesiocaeca japonica sp. nov. is unique within Hesionidae because of the combination of having four pairs of tentacular cirri and lacking of claw-shaped chaetae, stout compound chaetae and facial tubercle. Several hesionid species bear only four pairs of tentacular cirri, but they have at least one of the characters which the new species lacks.

Figures

Fig. 16. Parahesiocaeca japonica gen. et sp. nov., holotype (NSMT-Pol H-761) (E–L) and paratypes (NSMT-Pol P-762) (A–D). A, dorsal view of the anterior body. B, dorsal view of the anterior end with everted proboscis (median antenna and left dorsal tentacular cirrus on the second segment lost). C, ventral view of the anterior end with proboscis not everted. D, ventral view of everted proboscis. E, enlarged ventral view of left side of anterior body, showing two pairs of tentacular cirri and chaetigers 1 and 2 (dorsal and ventral tentacular cirri on the second segment lost). F, dorsal view of the posterior body (left anal cirrus lost). G, posterior view of right parapodium 7. H, notopodial aciculae. I, neuropodial acicula. J, supra-acicular chaeta.K, superior sub-acicular chaeta. L, inferior sub-acicular chaeta. Scale bar: 0.5mm for A; 0.2mm for B–D, F; 0.1mm for E, G; 0.02mm for H–L.