Tetranemertes sp.

Abato, Jamael C., Hookabe, Natsumi & Kajihara, Hiroshi, 2025, Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan, Species Diversity 30 (1), pp. 71-83 : 79-80

Tetranemertes sp. AHK-2024-2

( Fig. 8 )

Emplectonema kandai : Kajihara 2017: 435, fig. 6.4n –p.

Material examined. One specimen, collected intertidally from a tidal flat near the mouth of Aburatsubo Cove , Misaki, Kanagawa, Japan, by Dr . Yuji Ise on 18 May 2007.

Sequence. GenBank accession number PQ564664, COI (538 bp).

Description. Body 50 cm in length, 1 mm in width; anterior end yellowish white, intestinal region red to reddish brown ( Fig. 8A ). Ocelli arranged in four rows, with two rows above the other two, each consisting of ~10–13 eyes ( Fig. 8B ). Central stylet—albeit deformed after fixation—approximately 60 µm in length; basis 150 µm in length, posteriorly bilobed ( Fig. 8C ); stylet/basis ratio 0.4.

Remarks. Kajihara (2017) misidentified the specimen from Misaki as E. kandai (now T. kandai ) without examining the central stylet and basis. In this study, the stylet/ basis ratio in this Misaki specimen (0.4) is shown to be quite different from that of T. kandai (1.45). This species should be fully described when more complete information is obtained. In terms of COI p -distance, this species is closest to T. rubrolineata (9.9%) among other congeners ( Table 2). Tetranemertes sp. AHK-2024-2 forms a clade with T. pastafariensis and with another undescribed congener Monostilifera sp. 2 from Argentina.

Figures

Fig. 8. Tetranemertes sp. AHK-2024-2. A, Entire specimen; B, magnification of head, dorsal view; C, central stylet (outlined in white) and basis (outlined in black) (deformed after fixation), cleared in xylene, taken from Bouin-fixed specimen. Scale bar: C, 50µm.