Bathyvermilia challengeri Zibrowius, 1973

Kupriyanova, Elena K. & Flaxman, Beth, 2024, Serpulidae (Annelida) of the Australian Indian Ocean Territories, Records of the Australian Museum (Rec. Aust. Mus.) 76 (4), pp. 211-242 : 218-219

Bathyvermilia challengeri Zibrowius, 1973

Fig. 3A–F

Placostegus ornatus (not Sowerby in Mörch, 1863: 420) McIntosh, 1885: 522–524, pl. 55, fig. 5–6, pl. 30A, fig. 25–27.

Bathyvermilia challengeri Zibrowius, 1973: 428–430 , fig. 1a–e; Kupriyanova et al., 2011; Gunton et al., 2021: 214–25, fig. 28A.

Material examined. W.53395, Christmas Island SE (10°33'00"S, 105°42'11"E), depth 1225–1626 m, 06/07/2021 (1 spec. in tube, photo and prepared for SEM) .

Species diagnosis. Very recognisable tubes with characteristic sculpture made of numerous transverse ridges close to each other ( Fig. 3A ). Thoracic membranes rounded, extending to 3 rd thoracic segment ( Fig. 3B ). Operculum conical, covered with simple slightly raised chitinous endplate having distinct rims ( Fig. 3B ). Peduncle smooth cylindrical, constriction obvious ( Fig. 3C ). Collar chaetae simple limbate ( Fig. 3D ). Apomatus chaetae present in thorax ( Fig. 3E ). Thoracic uncini saw-to-rasp shaped, with 12 teeth in lateral view and simple, pointed anterior fang ( Fig. 3F ).

Remarks. This species is easily recognisable by its very characteristic tube with numerous conspicuous transverse ridges (not anteriorly directed peristomes), positioned close to each other, encircling the tube interrupted by a longitudinal groove cutting transverse ridges near the base. The original records of this species came from three HMS “ Challenger ” stations in the North and South Pacific Ocean taken at 4246–5719 m ( Zibrowius, 1973). Most recently a specimen was collected in the Eastern Australian Abyss (Gunton et al., 2021); this specimen was sequenced for the present study because DNA amplification of the B. challengeri specimen from IOT examined here was unsuccessful.

The specimen of B. challengeri from IOT shows at least 12 teeth in lateral view of thoracic uncini, moreover, these uncini are saw-to-rasp shaped ( Fig. 3F ). The original description of B. challengeri ( Zibrowius,1973) states “thoracic uncini saw-shaped with about 7 to 10 teeth”. The generic diagnosis in Kupriyanova and Ippolitov (2015) gives saw-shaped thoracic uncini with 6–10 teeth, while 9–11 teeth were reported for B. gregrousei . Thus, we emended the diagnosis of the genus Bathyvermilia to reflect the observed variability.

The specimen collected off Johnston Atoll near Hawaii at 380 m (Kupriyanova et al., 2011) is currently the shallowest record for this nominal species. Although the specimen from the upper bathyal off Johnston Atoll fits the original description of B. challengeri and is morphologically very similar to the specimens collected from the lower abyssal zone, such a disjunct bathymetric distribution is unusual (reviewed in Capa et al., 2021). Further collecting and additional taxonomic studies of deep-sea serpulids are needed to determine whether B. challengeri does have disjunct or wide bathymetric distribution or whether at least two morphologically similar species are present in the Pacific Ocean.

Distribution. Mid-Pacific Ocean, 4246–5719 m, Johnston Atoll (about 1400 km west of Hawaii), 380 m; South Pacific Ocean off NSW, Australia, 2562–2587 m; South Indian Ocean, off Christmas Island, Australia, 1225–1626 m.

Figures

Figure 3. Bathyvermilia challengeri W.53395.A – tube fragments, B – lateral view of thorax with radioles and operculum, C – close-up view of the operculum (stained), D – SEM of collar chaetae, E – Apomatus chaetae, F – thoracic uncini. Scale: A, B – 1 mm; C – 0.5 mm. D – 50 µm; E, G – 10 µm.