Osedax randyi, Rouse & Goffredi & Johnson & Vrijenhoek, 2018

Rouse, Greg W., Goffredi, Shana K., Johnson, Shannon B. & Vrijenhoek, Robert C., 2018, An inordinate fondness for Osedax (Siboglinidae: Annelida): Fourteen new species of bone worms from California, Zootaxa 4377 (4), pp. 451-489 : 481-483

Osedax randyi n. sp.

Figure 17

‘white collar’ ( Rouse et al. 2015; Vrijenhoek et al. 2009)

‘Sagami-7’ (GenBank COI sequence FM998108 -9; Pradillon et al. unpublished)

Material examined. Holotype: Female, fixed in formalin preserved in ethanol, SIO-BIC A 7845 (GenBank COI sequence FJ347615 ), collected from a whale carcass ( Balaenoptera musculus ) deployed at 1018 meters depth in Monterey Submarine Canyon , California (36°46.308’N; 122° 4.981’W), ROV Tiburon dive number 1049, Oct. 25, 2006. Paratypes: Female, fixed in formalin preserved in ethanol SIO-BIC A1648, SIO-BIC A7846 (GenBank COI sequence FJ347612 , FJ347613 ), same locality and date as holotype; Female and dwarf males (allotypes), fixed in formalin, female sectioned, males preserved in ethanol SIO-BIC A7847 (female GenBank COI sequence FJ347614 ), same locality and date as holotype.

Diagnosis and description. Holotype female, in life trunk 5 mm long, 0.8 mm wide; crown of palps somewhat contracted, 4.5 mm long ( Fig. 17A ). Pinnules of all palps oriented dorsally and the oviduct lying between the dorsalmost pair of palps ( Figs 17A, B, D ). Oviduct extends from trunk into crown for 1-2 mm ( Figs 17A, B ). In life, palps reddish with pigmented white outer margins ( Fig. 17A ). Trunk with white ring around anterior margin; ring broken mid-dorsally by oviduct and mid-ventrally by and oval unpigmented patch ( Figs 17A, B ). Clear demarcation of upper and lower trunk ( Fig. 17A ). Internally trunk shows extensive musculature and glands with prominent dorsal and ventral blood vessels ( Fig. 17E ). Ovisac in holotype, damaged, an ellipsoidal mass; similar shape in paratypes. Roots incomplete, simple lobes where present in all specimens. Males dwarfs, with spermatids and sperm, chaetal-bearing segments inflated ( Fig. 17C ), found in tube lumen of females.

Distribution. Known from Monterey Bay, California from 1018 meters depth, and from Sagami Bay, Japan ( Table 2). It has been found in whale and cow bones.

Etymology. This species is named (noun in the genitive case) in honor of Randy Prickett, Senior ROV pilot for MBARI, who collected many bones and Osedax over the years.

Remarks. Osedax randyi n. sp. is part of Osedax Clade IV and closest relative to the undescribed Osedax species from California known as O. ‘MB16’ ( Fig. 1 ) with a minimum uncorrected COI- distance of ~6-7% ( Table 4). As previously noted, this is among the smaller interspecific distances among Osedax species. Two COI sequences, referred to Osedax sp. Sagami-7 (Pradillon et al., GenBank unpublished, Table 3) are much less than 1% divergent from the six California Osedax randyi n. sp. sequences (example distance in Table 4). Thus, it is reasonable to propose that Osedax randyi n. sp. is also found in Japan. The most distinguishing features of Osedax randyi n. sp. are the white ring around the anterior part of the trunk and white pigment on the palps of females ( Fig. 17A, B ), though a similar whitish ring is found on females of O. bryani n. sp. ( Fig. 18A, B ) and O. frankpressi ( Rouse et al. 2004) , with the latter species also showing white pigmentation on the palps. DNA sequencing is most likely the best way to distinguish Osedax randyi n. sp. from these species.

Figures

FIGURE 1. Osedax phylogenetic analyses. Osedax multi-gene phylogeny with Monilifera as outgroup.Maximum likelihood tree topology based on a partitioned dataset of five gene segments (MAFFT-aligned) for data shown in Table 2. The Bayesian analyses gave the same topology. Bootstrap support % (BS) is at each node, followed by posterior probability (PP) from the MrBayes analyses. * indicates values were ± 95% (BS) and 0.95 (PP). Missing values indicate BS <50% and PP <0.7. Six major Osedax clades are distinguished, following Vrijenhoek et al. (2009), Rouse et al. (2015) and Taboada et al. (2015). The various forms of palps (or absence thereof in the case of O. jabba n. sp.) are indicated for the major clades but these are not intended to indicate apomorphic states.

FIGURE 17. Osedax randyi n. sp., previously Osedax ‘white collar’. A. Micrograph of live holotype (SIO-BIC A7845), female in lateral view, removed from its tube and showing crown, trunk and part of ovisac. Note midventral gap in white pigment ring. B. Dorsal view of live specimen (paratype SIO-BIC A7847) showing white pigmented ring anteriorly with a dorsal gap where oviduct runs through it. Note pinnules of all palps oriented dorsally and oviduct lying between dorsalmost pair of palps. C. Differential interference micrograph of a solitary male dissected from tube of paratype (SIO-BIC A7847). Some hooks are visible in expanded posterior region. A large mass of mature sperm is visible in mid-body and extending into head, though there are a few obvious spermatids. D. Transverse section (7 µm) of paratype (SIO-BIC A7847), through crown showing pinnules of all palps oriented dorsally and oviduct lying between dorsalmost pair of palps. E. Transverse section (7 µm) through the trunk of paratype (SIO-BIC A7847) showing extensive musculature and glands. Prominent dorsal and ventral blood vessels are also visible.

FIGURE 18. Osedax bryani n. sp., previously Osedax ‘MB17’. A. Micrograph of live holotype (SIO-BIC A4619), female in dorsal view,removed from its tubeand showing crown, trunk and part of ovisac.Oviductlies between dorsalmostpair of palps. Little apparent pigmentation around anterior trunk B. Ventral view of live holotype (SIO-BIC A4619) showing white pigmentation anteriorly with midventral gap. Pinnules of all palps oriented dorsally. Arrow indicates oval unpigmented patch. C. Differential interference micrograph (from a stack series) of a solitary male (or larval stage?) dissected from tube of holotype (SIO-BIC A4619). Some hooks are visible in expanded posterior region. No mature sperm is visible though there are several bundles of spermatids.