Ototyphlonemertes (parmula) tsukagoshii 1863

Kajihara, Hiroshi, Tamura, Kotaro & Tomioka, Shinri, 2018, Histology-free Descriptions for Seven Species of Interstitial Ribbon Worms in the Genus Ototyphlonemertes (Nemertea: Monostilifera) from Vietnam, Species Diversity 23 (1), pp. 13-37 : 28

Ototyphlonemertes (parmula) tsukagoshii sp. nov.

( Fig. 11 )

Material examined. Two specimens, both from Dam Ngoai; ICHUM 5371 (holotype); ICHUM 5372 (paratype) .

Description. Body length 2.5 mm (paratype) to 4.0 mm (holotype), width 0.1 mm (paratype) to 0.2 mm (holotype) (n =2). Epidermis whitish ( Fig. 11A ); cephalic furrow postcerebrally; tissues around brain (and even in precerebral region in one of two specimens examined) reddish ( Fig. 11B, C ); cirri present in both anterior and posterior ends of body; cephalic cirrus formula (cf. Norenburg 1988b) observed in two specimens: A=2, B=0, C=8, D=?, E=?, tail= 12 in holotype; A=2, B=0, C=5+6, D=6+10, E=3, tail= 10 in paratype. Foregut–intestine junction indistinct. Statolith polygranular ( Fig. 11D, E ), 9.5 µm in diameter (n =2), consisting of 6 granules; statocyst 23.5 µm (holotype) to 28.4 µm (paratype) in diameter (n =2). Proboscis anterior chamber with wart-like papillae ( Fig. 11F ); diaphragm short ( Fig. 11F ); gland secretion ring situated posterior to hind end of basis; accessory-stylet pouches two, each containing 2–3 accessory stylets directing both forward and backward; central stylet (as well as accessory stylets) spiral ( Fig. 11G, H ), 35.0 µm (paratype) to 40.2 µm (holotype) long; basis 37.1 µm (paratype) to 40.2 µm (holotype) long, 8.3 µm (paratype) to 11.2 µm (holotype) wide (n =2), with each ridge twisting 3 times; basis length/width ratio 3.59 (holotype) to 4.47 (paratype); middle chamber bulbous ( Fig. 11F ); posterior chamber opaque, with specialized anterior part ( Fig. 11B, C ). Intestinal diverticula deep. Posterior adhesive plate containing cells with orange contents.

Distribution. So far only recorded from the type locality, Dam Ngoai, Vietnam.

Etymology. The specific name is a noun in the genitive case, after the Japanese ostracode systematist Professor Akira Tsukagoshi at Shizuoka University, Japan, who organized our sampling trip to Phu Quoc.

Remarks. In the phylogenetic tree, Ototyphlonemertes ( parmula ) tsukagoshii sp. nov. was sister to O. ( parmula ) nakaoae sp. nov. ( Fig. 2 ). Ototyphlonemertes ( parmula ) tsukagoshii differs from O. ( parmula ) nakaoae by the smaller body length (2.5–4.0 mm vs. 4.1–6.2 mm), fewer number of statolith granules (6 vs. 7–8), and greater number of styletridge twists (3 vs. 1.5–2). Also, O. ( parmula ) tsukagoshii tends to be more reddish in the external appearance, especially in the brain region, than O. ( parmula ) nakaoae .

Figures

Fig. 11. Ototyphlonemertes (parmula) tsukagoshii sp. nov. A, Entire body; B, C, composite photomicrographs of squeezed specimens; D, E, statoliths; F, partially everted proboscis; G, H, central stylets and bases. A, B, D, F, G, ICHUM 5371 (holotype); C, E, H, ICHUM 5372 (paratype).

Fig. 2. Part of the phylogenetic tree resulting from the maximum-likelihood analysis of COI (ln L=−15264.650301), along with results of three species-delimitation analyses, ABGD, PTP, and TCS, as indicated by vertical bars. Numbers near nodes indicate maximum-likelihood bootstrap support value.