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

Tetranemertes sp. AHK-2024-1

( Fig. 7 )

Material examined. One specimen, collected by Hiroshi Kajihara on 27 May 2001 from between the base of a sponge and its attaching rock, obtained by beam-trawling from a depth of 288 m at 28°08.95′N, 129°6.85′E, approximately 6–7 km west of Kakeromajima island in the Amami Islands , which is part of the Ryukyu Islands , in the East China Sea, during the 3rd research cruise in F .Y. 2001 of the TR/ V Toyoshio-maru.

Sequence. GenBank accession number PQ564663, COI (658 bp).

Description. Body 40 cm in length and 1.3mm in width, transparent and colorless; rhynchocoel extending for 1 cm from anterior end; intestine reddish orange; eyes orange in color, ~ 67 in total number, arranged in four lines ( Fig. 7 ); brain whitish; pair of ventral cephalic furrows meeting medially, forming Λ-shape with apex pointing anteriorly.

Remarks. Due to the lack of certain morphological data, especially those of the stylet apparatus, the material is left undescribed despite being morphologically and molecularly distinct from the named Tetranemertes . This undescribed species differs from other congeners by colorless and transparent body. In terms of COI p -distance, this species is closest to T. antonina (10.2%) among other congeners ( Table 2). Tetranemertes sp. AHK-2024-1 forms a clade with T. antonina and T. paulayi and is sister to the former ( Fig. 4 ).

The specimen of Tetranemertes sp. AHK-2024-1, preserved in 99% ethanol, had been left at room temperature for 23 years before DNA extraction. The DNA has likely been fragmented, as PCR amplification using the LCO1490/ HCO2198 primer pair, expected to yield a 685-bp fragment, failed. To obtain the COI sequence from this specimen, we designed the specific primers TkaCOF/TkaCOR based on aligned sequences from the congeners. In combination with the LCO1490/HCO2198 primers, we obtained 339-bp and 434-bp fragments of the Folmer region. This suggests that the application of so-called next-generation sequencing (such as Illumina MiSeq) would retrieve a greater amount of sequence information even from ethanol-preserved specimens kept at room temperature for ~20 years.

Figures

Fig. 7. Tetranemertes sp. AHK-2024-1, anterior end of body, dorsal view.

Fig. 4. Rooted Bayesian phylogenetic tree showing the position of Tetranemertes aurantia sp. nov. within the genus Tetranemertes based on concatenated sequences of five gene markers (16S, 18S, 28S, COI, and H3). Numbers represent branch support—Bayesian posterior probability (PP)/IQ-Tree maximum-likelihood ultrafast bootstrap value (UFBoot)/RAxML maximum-likelihood bootstrap value (BS). Thickened branch indicates full support (1.00 PP/100% UFBoot/100% BS).