Alvinonemertes claudiae gen. et sp. nov.

urn:lsid:zoobank.org:act: 1BA9AE85-AB72-4736-9132-79796011C259

Figs 8G, 10H–N

Diagnosis

Alvinonemertes claudiae gen. et sp. nov. can be attributed to the genus Alvinonemertes gen. nov. based on molecular data. It differs from all other species in the genus by its very translucent body that is pale yellowish. It can be differentiated from A. dariae gen. et sp. nov. by the characteristics given in the diagnosis of A. dariae .

Etymology

For Claudia Müller, lab technician at the Institute of Evolutionary Biology, University of Bonn. Acknowledging her support in the immunohistology lab over many years and also in recognition of her devotion to the care of our live annelid and nemertean worm cultures.

Material examined

Holotype

NORTHEASTERN PACIFIC OCEAN • ♂ (fixed in formaldehyde and prepared as 15 slides with transverse sections, see cybertype); hydrothermal vents at South Cleft, Juan de Fuca Ridge; 44.659° N, 130.364° W; depth ca 2250 m; 31 Jul. 2016; Greg Rouse leg.; collected by ROV Doc Ricketts, Dive 875; SIO-BIC N283 (ex SIO-BIC N231).

Paratypes

NORTHEASTERN PACIFIC OCEAN • 1 spec. (fixed in formaldehyde); same collection data as for holotype; SIO-BIC N284 (ex SIO-BIC N231) • 3 specs (ethanol); same collection data as for holotype; GenBank: ON036050, ON021868; SIO-BIC N231 .

Cybertype Images of serial sections of holotype: https://doi.org/10.5281/zenodo.5346520.

Description

Specimens 6 mm long and 0.7 mm in diameter. Body cylindrical. One pair of cephalic furrows, forming the shape of an anteriorly open V. Head not demarcated from rest of body, rounded. Body translucent. Internal organs, such as gut and gonads, well visible through body wall (Fig. 8G).

Epidermis in foregut region 10 µm thick. Body wall composed of two muscle layers (outer circular, inner longitudinal). Esophagus opening subterminal, ventral; stomach without pouches; pylorus longer than stomach; intestinal cecum with ventral unpaired anterior pouch under stomach and one pair of lateral pouches (Fig. 10K); intestine with lateral diverticula. Precerebral septum closed. Rhynchocoel wall with very thin outer circular and inner longitudinal muscle layers, rhynchocoel almost extending to posterior end of body. Proboscis with outer circular, middle longitudinal, and inner circular muscle layers. Proboscis with 10 proboscis nerves; central stylet and two accessory stylet pouches present, four to five accessory stylets per pouch (Fig. 10M–N). Stylet basis circular in cross section. Proboscis pore subterminal, ventral (Fig. 10H). Nervous system with thin outer neurilemma, without neurochord cells (Fig. 10J); dorsal commissure short, ventral commissure broad. Lateral nerve cords without accessory nerve (Fig. 10K). Cerebral ganglia and lateral nerves in longitudinal muscle layer (Fig. 10J–K). Eyes absent. Cerebral organs less than half the size of brain lobes, close in front of brain. Paired cerebral canal simple, unforked, opens ventro-laterally into cephalic furrows (Fig. 10I). Apical organ present, unpaired; cephalic gland extending to brain (Fig. 10H, J). Circulatory system consisting of cephalic loop, mid-dorsal vessel not forming vascular plug ((Fig. 10L). Testes sac like, alternating with intestinal diverticula, situated ventrally.

Ecology

Associated with hydrothermal vents, alongside other vent fauna such as the annelids Branchinotogluma tunnicliffeae (Pettibone, 1988) (e.g., SIO-BIC A7716), Paralvinella sulfincola Desbruyères & Laubier, 1993 (e.g., SIO-BIC A7724) and Ridgeia piscesae Jones, 1985 (e.g., SIO-BIC A7719).

Remarks

The new species is attributed to the genus Alvinonemertes gen. nov. based on the executed phylogenetic analyses. In the concatenated analysis, A. claudiae gen. et sp. nov. is sister to A. christianeae gen. et sp. nov. (Fig. 7).