Tetranemertes majinbuui, Cherneva & Ellison & Zattara & Norenburg & Schwartz & Junoy & Maslakova, 2023

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

Tetranemertes majinbuui sp. nov.

Fig. 5

Material examined.

Type material is deposited with the Smithsonian Institution's National Museum of Natural History. Holotype CB056_18_01 (USNM 1618677): anterior end preserved for histology, and posterior in 95% ethanol. Paratype 856_080303_3 (USNM 1156478): histological sections of anterior end. See Table 1 for additional specimens, accession numbers, and Table 2 for collecting information .

Diagnosis.

Pink body color distinguishes T. majinbuui sp. nov. from T. bifrost sp. nov., T. rubrolineata , T. unistriata sp. nov., T. ocelata sp. nov., T. pastafariensis sp. nov., and T. paulayi sp. nov. It differs from T. antonina and T. hermaphroditica by having a posteriorly bilobed basis, and spirally sculpted shaft of stylet. It most resembles T. arabica sp. nov. from which it is widely separated geographically. It is currently unknown whether it has separate sexes; if so, then it would distinguish it from T. hermaphroditica , which is a simultaneous hermaphrodite. DNA barcodes characterize this species unambiguously, clearly differentiating it from all other sequenced species of the genus (Table 5 ).

Description.

External appearance of live specimens. Long, thin, thread-like body. Can stretch much more than 10 cm, and is 0.3-0.5 mm wide at the head. Body rounded in cross-section throughout most of its length, but dorso-ventrally compressed in the head region anterior to the brain. The caudal end is bluntly rounded. Body color is uniform intense pink, paler towards the anterior end (Fig. 5A ). As viewed with a microscope most of the pink color is associated with the gut, while the anterior end is pale pink or translucent. The caudal end is paler, and has some dorsal granules of darker color. The anterior part of the head is demarcated from the body by both width and a single transverse ventral furrow (Fig. 5B, C , arrowheads).

When placed in a dish, tangles into a writhing mass. Secretes transparent, sticky mucus when handled. Moves by ciliary gliding, often with the anterior end of the head raised at an angle from the surface, the inflection point coinciding with the lateral indentation of the transverse cephalic furrow. When mechanically perturbed, contracts forming a loose coil. The head region anterior to the cephalic furrow is less contractile, causing an obvious discontinuity in width when the animal is contracted. Regeneration ability not known. Blood is colorless.

Head is shaped like a narrow diamond or spearhead, vaguely reminiscent of a viper’s head. Anterior to the cephalic furrow, the head is dorso-ventrally compressed; posterior to it there is a dorsal bulge corresponding to the cerebral ganglia. The cerebral ganglia are clearly visible, transparent or very pale pink.

A single transverse cephalic furrow is formed by a pair of the cerebral organ furrows, fused mid-ventrally. The furrow starts laterally and continues toward the ventral midline, forming a very shallow forward-pointing “V”, anterior to cerebral ganglia (Fig. 5B, C ). Rhynchostomopore is ventral. Posterior cephalic furrows lacking.

Numerous reddish brown ocelli (~ 24 on each side of head) are arranged in four longitudinal rows (Fig. 5B-D ). The medial rows, which are not visible in ventral view, reach anterior margin of the cerebral ganglia. The lateral rows have fewer eyes, reach slightly posterior to the cephalic furrow and are visible in ventral view. When viewed from dorsal side appear to form two rows, because the two rows on each side of head are almost directly on top of each other. Cerebral organs small and inconspicuous, indiscernible even on squeeze preparations.

Rhynchocoel and proboscis. Rhynchocoel does not exceed 1/3 of body length. The proboscis is translucent, with two distinctive regions separated by a stylet bulb. The anterior region is much shorter than the posterior, and the bulb has a length to width ratio of ~ 1. The proboscis is armed with a single central stylet and a pair of lateral pouches holding two accessory stylets each. The shaft of the stylet is straight, sculpted with spiral grooves (Fig. 5E, F ). The basis is rod-shaped with an approximate ratio of 1:4 width to length, characteristically bilobed posteriorly in larger individuals (Fig. 5E ). Two individuals with much smaller stylets (possibly, due to younger age or regeneration of proboscis) were observed to have a basis posteriorly rounded rather than bilobed (Fig. 5F ). Stylet to basis length ratio is ~ 1:1 (n = 1).

Reproduction. No data.

Habitat.

Free living, benthic marine worms inhabiting coral rubble at shallow depths (1-7 m). Can be found stretching between nooks and crannies of the substratum.

Geographic distribution.

Bocas del Toro, Panamá; Puerto Rico, USA.

Etymology.

The species is named after Majin Buu, a male (as far as we can tell) character in the anime Dragon Ball Z, due to its resemblance in color, presence of black dots at the anterior end, and behavior-dependent variability in body width.

Figures

Figure 5. Tetranemertes majinbuui sp. nov. A external appearance in life of individual CB 056 _ 18 _ 01 B-D Close ups of head of a living individual CBdT 0058, showing eyes and cephalic furrow (arrowheads) in lateral (B) and dorsal (C) view. Note the cephalic furrow is on the ventral side, but shows through due to transparency of the body at the anterior end D Head compressed under a coverglass to show number and distribution of eyes E stylet armature of individual CB 056 _ 18 _ 01 with a typical posteriorly bilobed basis F stylet armature of individual CBdT 0058 with a less typical basis (not bilobed or forked posteriorly). Note helical sculpting of stylet shaft. Abbreviations: cg - cerebral ganglion, co - cerebral organ. Scale bars: 5 mm (A); 1 mm (B-D); 25 μm (E, F).