Osedax estcourti, Berman & Hiley & Read & Rouse, 2024

Berman, Gabriella H., Hiley, Avery S., Read, Geoffrey B. & Rouse, Greg W., 2024, New Species of Osedax (Siboglinidae: Annelida) from New Zealand and the Gulf of Mexico, Zootaxa 5443 (3), pp. 337-352 : 346

Osedax estcourti n. sp.

Fig. 7A, B , 8A

Material examined. Holotype: NIWA 159436 female (GenBank COI sequence ON211943, 18S = ON220129, 28S = ON220739, H3 = ON254809), collected from a whale skull (most likely a southern minke whale Balaenoptera bonaerensis Burmeister, 1867 at 390–393 m depth on the Pukaki Rise SE of New Zealand (49.121° S; 172.136° E) . Scientific trawl TAN1614, Station 9, R / V Tangaroa , December 1, 2016. Fixed and preserved in 95% ethanol.

Diagnosis and description. Live animals red, in transparent tubes on whale skull ( Fig. 7A ). Fixed roots and palps desiccated ( Fig. 7B ). Trunk not visible ( Fig. 7B ). Apinnulate palps are brown, approximately 3 mm long and 1 mm wide ( Fig. 7B ). Four palps contained inside translucent tube ( Fig. 7B ). Roots approximately 3 mm long, 1.5 mm wide, brown, still partially embedded in white bone ( Fig. 7B ). No dwarf males observed. The rDNC diagnosis for Osedax estcourti n. sp. was recovered as: ‘C’ at site 348, ‘G’ at site 579, and ‘G’ at site 606 of mitochondrial COI.

Distribution. Osedax estcourti n. sp. was recovered from a whale fall on the Pukaki Rise off SE New Zealand at 390– 393 m.

Etymology. Osedax estcourti n. sp. is named in remembrance of Dr. Ivan Neil Estcourt (1938–1981), benthic ecologist and the first polychaetologist researcher at the former New Zealand Oceanographic Institute (now NIWA).

Remarks. Osedax estcourti n. sp. belongs to Clade II, an apinnulate clade. Osedax estcourti n. sp. was recovered as the sister species to Osedax ventana , known from 2,898 m in Monterey Bay (California, USA), though the relationship was not well supported, with poor bootstrap support ( Fig. 2 ). The minimum interspecific distance between O. estcourti and O. ventana was 14.6% ( Table 3 ), thus providing ample molecular evidence for it to be a new species. Two other specimens were destroyed for sequencing (ON211941, ON211942). The new species had a 1.5% maximum intraspecific pairwise distance among the three available sequences, though all three sequences showed the rDNC diagnostic bases. The haplotype network for Osedax estcourti n. sp. showed three distinct haplotypes, one for each sequence with a maximum of 10 nucleotide substitutions ( Fig. 8A ). Specimens were not observed alive, however images of the whale skull at the time it was collected show red Osedax coating the surface ( Fig. 7A ), suggesting that living Osedax estcourti n. sp. may have red palps.

Figures

FIGURE 2. Maximum likelihood Osedax phylogenetic tree generated with data from five genetic markers as listed in Table 2. Bootstrap support values are on each node; those below 50% not shown. Presence or absence of pinnules is noted for each clade.

FIGURE 7. A. Whale skull trawled from ~390 m on the Pukaki Rise off New Zealand with an inset close-up of the Osedax. Arrows and inset point at Osedax patches. B. Osedax estcourti n. sp. holotype (NIWA 159436), desiccated, with four apinnulate palps (indicated by numbers 1–4) in tube and the ovisac/root region still in bone. C. Osedax traceyae n. sp. holotype (NIWA 159436) comprising desiccated apinnulate palps (indicated by numbers 1–4) in tube.

FIGURE 8. Haplotype networks using COI. Circles are haplotypes, blue circles and crosshatches are single nucleotide substitutions. * indicates the haplotype of the holotype. A. Network for three specimens of Osedax estcourti n. sp. GenBank accession numbers: ON211941, ON211942, ON211943 (Holotype). B. Network for 11 specimens of Osedax traceyae n. sp. GenBank accession numbers: ON211983, ON211984, ON211985, ON211986, ON211987, ON211988, ON211989, ON211990 (Holotype), ON211991, ON211992, ON211993.