Tetranemertes Chernyshev, 1992

Cherneva, Irina, Ellison, Christina I., Zattara, Eduardo E., Norenburg, Jon L., Schwartz, Megan L., Junoy, Juan & Maslakova, Svetlana A., 2023, Seven new species of Tetranemertes Chernyshev, 1992 (Monostilifera, Hoplonemertea, Nemertea) from the Caribbean Sea, western Pacific, and Arabian Sea, and revision of the genus, ZooKeys 1181, pp. 167-200 : 167

Genus Tetranemertes Chernyshev, 1992

Type species.

Tetranemertes antonina (Quatrefages, 1846), by monotypy.

Diagnosis.

Body long and thin, thread-like; head not demarcated from body; numerous ocelli arranged in four longitudinal rows (two on each side of head, the two rows almost on top of one another); cerebral organs small, located far in front of brain; a pair of shallow oblique or transverse cerebral organ furrows restricted to ventral and lateral surfaces, fused mid-ventrally forming a single furrow; cerebral commissures unusually short and wide; lateral nerve cords with a single fibrous core; longitudinal musculature anteriorly divided by a layer of connective tissue, only the inner layer contributes to proboscis insertion, i.e. precerebral septum lacking; rhynchocoel between 1/5 and 1/3 of body length; proboscis short and thin, with a neural sheath rather than distinct proboscis nerves; anterior proboscis very short, stylets located very close to head, often within a few millimeters of cerebral ganglia. The seven new species described below, as well as Tetranemertes rubrolineata , possess an unusual character of having the central stylet’s basis posteriorly slightly bilobed to deeply forked in fully grown individuals.

Composition.

The genus includes ten described species: Tetranemertes antonina (Quatrefages, 1846), T. rubrolineata (Kirsteuer, 1965), T. hermaphroditica (Gibson, 1982), T. bifrost sp. nov., T. majinbuui sp. nov., T. pastafariensis sp. nov., T. unistriata sp. nov., T. ocelata sp. nov., T. paulayi sp. nov., T. arabica sp. nov., and one undescribed species ( Tetranemertes sp. ETP001). Ommatoplea ophiocephala Schmarda, 1859 from South Africa, previously synonymized with T. antonina by Friedrich (1955), is almost certainly a distinct species, most likely not related to Tetranemertes (see Discussion).

Geographic distribution.

Mediterranean Sea (Banyuls, Trieste, Sicily, Naples, Alborán Island, Almería, Strait of Gibraltar), Caribbean Sea (Bocas del Toro, Panamá; Carrie Bow Cay, Belize; Puerto Rico, USA), western Indian Ocean (Madagascar), Arabian Sea (Dhofar Governorate, Oman), Western Pacific (Heron Island, Australia and Honshu Island, Japan), Eastern Tropical Pacific ( Panamá).

Etymology.

The name refers to the number of times the genus Nemertes was re-defined: Nemertes Cuvier, 1817, Nemertes Johnston, 1837, Nemertes Friedrich, 1955, and Nemertes Kirsteuer, 1974.