Ototyphlonemertes (duplex) norenburgi 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 : 22

Ototyphlonemertes (duplex) norenburgi sp. nov.

( Fig. 6 )

Material examined. Two specimens, both from Dam Ngoai; ICHUM 5355 (holotype); ICHUM 5356 (paratype) .

Description. Body length 7.8 mm (paratype) to 9.0 mm (holotype), width 0.2 mm (paratype) to 0.3 mm (holotype) (n =2). Epidermis whitish ( Fig. 6A, B ); cephalic furrow post-cerebrally; tissues around brain reddish ( Fig. 6C ); cirri present in both anterior and posterior ends of body. Foregut-intestine junction not distinct (intestinal caecum possibly present). Statoliths bipartite ( Fig. 6D ), 8.4 µm (paratype) to 9.6 µm (holotype) in diameter (n =2); statocyst 27.9 µm (holotype) to 30.5 µm (paratype) in diameter (n =2). Proboscis diaphragm short ( Fig. 6E ); two accessory stylet pouches, lateral to central-stylet basis, each containing 2–3 accessory stylets (n =2); in holotype, one of two accessorystylet pouch contained three accessory stylets all directing forward; another accessory-stylet pouch contained two accessory stylets each directing forward and backward; paratype had two accessory stylets per pouch both directing forward; middle chamber bulbous; central stylet smooth ( Fig. 6E, F ), 28.3 µm (holotype) to 33.0 µm (paratype) long; basis 26.4 µm (paratype) to 29.1 µm (holotype) long, 7.5 µm (holotype) to 9.3 µm (paratype) wide (n =2); basis length width ratio 2.84 (paratype) to 3.88 (holotype) (n =2); posterior chamber opaque, without specialized anterior portion. Intestinal diverticula shallow. Posterior adhesive plate containing cells with orange contents. Mature oocytes up to 70 µm in diameter, accounting for more than 40% of body width ( Fig. 6C ).

Distribution. Our unpublished sequence data indicate that O. ( duplex ) norenburgi sp. nov. is also distributed in Onnason, Okinawa-jima island, although it was recovered only from Dam Ngoai in the present study.

Etymology. The specific name is a noun in the genitive case, after the eminent nemertean biologist Dr Jon Laurence Norenburg at the Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, USA, in respect of his distinguished achievement and contribution to the ribbon-worm systematics, including that of Ototyphlonemertes , as well as other interstitial animals.

Remarks. In the resulting phylogenetic tree, O. ( duplex ) norenburgi was sister to O. ( duplex ) envalli ( Fig. 2 ). Morphologically, O. ( duplex ) norenburgi may be distinguished from O. ( duplex ) envalli by the larger oocyte size relative to the body width: the oocyte/body-width ratio exceeds 0.4 in O. ( duplex ) norenburgi , while it is around 0.35 in O. ( duplex ) envalli [but see Remarks for O. ( duplex ) envalli above]. From O. ( duplex ) chernyshevi , O. ( duplex ) norenburgi may be distinguished by its thinner stylet basis: the basis length/width ratio was 2.84–3.88 in O. ( duplex ) norenburgi , while it was 2.28–2.80 in O. ( duplex ) chernyshevi .

Figures

Fig. 6. Ototyphlonemertes (duplex) norenburgi sp. nov. A, B, Entire body; C, composite photomicrograph of squeezed specimen; D, statoliths; E, stylet apparatus; F, central stylet and basis; G, posterior end of body. A, C, D, E, ICHUM 5355 (holotype); B, F, G, ICHUM 5356 (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.