Osedax packardorum, 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 : 479-481

Osedax packardorum n. sp.

Figure 16

‘orange collar’ ( Braby et al. 2007; Rouse et al. 2009; Rouse et al. 2015; Tresguerres et al. 2013; Vrijenhoek et al. 2009) ‘sp.4 SBJ-2006’ (GenBank COI sequence DQ996639 , DQ996641 -2)

Material examined. Holotype: Female, fixed in formalin preserved in ethanol, SIO-BIC A 1641 (GenBank COI sequence EU223341 ), collected from 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 and dwarf males (allotypes), fixed in formalin preserved in ethanol SIO-BIC A7840, A7842 (female GenBank COI sequences EU223339 , EU223343 ), same locality and date as holotype; Female, fixed in formalin preserved in ethanol, SIO-BIC A7841(GenBank COI sequence EU223340 ), same locality and date as holotype; Female, sectioned for histology, same locality and date as holotype, SIO-BIC A7843 (GenBank COI sequence EU223342 ); Female, fixed in formalin preserved in ethanol, SIO-BIC A7844 (GenBank COI sequence FJ431200 ), collected from whale fall ( Eschrichtius robustus ) at 663 meters depth in Monterey Submarine Canyon, California (36°48.178’N; 121°59.677’W) ROV Tiburon dive number 1160, Dec. 18, 2007.

Diagnosis and description. Holotype female, in life trunk 11 mm long, 0.6 mm wide; crown of palps contracted, curled, 2 mm long (image not shown as the trunk is damaged). Palps up to 12 mm long when extended in other specimens ( Figs 16A, B ). Pinnules of all palps oriented dorsally and the oviduct lying between the dorsalmost pair of palps ( Figs 16B, D, E ). Oviduct extends from trunk into crown for 3 mm ( Fig. 16B ). In life, palps reddish with two major blood vessels in each ( Figs 16A, B ). Tube a gelatinous loose mass around trunk ( Figs 16A, B ). Trunk with pale to dark orange ring around anterior margin; ring broken mid-dorsally by oviduct and midventrally by and oval unpigmented patch ( Figs 16A, B, E ). Internally trunk shows extensive musculature and glands with prominent dorsal and ventral blood vessels ( Fig. 16G ). Ovisac in holotype an ellipsoidal mass (not shown); extending laterally as lobes in other specimens ( Fig. 16C ). Roots of holotype extend from ovisac on one side as one mass; in other specimens, roots as long branching masses. Males dwarfs, with spermatids and sperm ( Figs 16F, G ), chaetal-bearing segments not inflated ( Fig. 16H ); found in tube lumen of females.

Distribution. Known from Monterey Bay, California at 349, 633, and 1018 meters depths ( Table 2). Found in whale and cow bones.

Etymology. This species is named (noun in the genitive case) in honor of the Packard family whose foundation supports MBARI and enabled the discovery of all of the Osedax species in California.

Remarks. Osedax packardorum n. sp. is part of Osedax Clade IV and closest relative to Osedax lehmani n. sp., ( Fig. 1 ), from which it has a minimum uncorrected distance for COI of 8-9% ( Table 4). As pointed out above, this is one of the smaller interspecific distances among Osedax species and the two species are morphologically very similar. All 27 available COI sequences for Osedax packardorum n. sp. ( Table 3) comprise less than 1% sequence divergence. The most distinguishing feature of Osedax packardorum n. sp. is the orange ring around the anterior part of the trunk. ( Fig. 16 A-C, E).

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 16. Osedax packardorum n. sp., previously Osedax ‘orange collar’. A. Ventral view of the trunk and crown of adult female on bone of a gray whale calf (Eschrichtius robustus) deployed at 385 meters in Monterey Canyon.Bone was recovered and brought to laboratory. Note distinctive dark orange ring around anterior end of trunk two blood vessels in each palp and numerous pinnules. Also note midventral gap in orange pigment ring. B. Another female from same bone in an aquarium. Female is spawning oocytes into water via oviduct that extends from trunk into crown of palps. Arrowhead indicates tip of oviduct. C. Micrograph of live paratype (SIO-BIC A7843) with ovisac and roots still largely in bone. D. Transverse section (7 µm) of paratype (SIO-BIC A7843) through crown showing pinnules of all palps oriented dorsally and oviduct lying slightly to side of the dorsalmost palps. E. Ventral view of trunk of paratype (SIO-BIC A7844). Pigmented ring is less orange in this specimen, but shows midventral gap. Pinnules of all palps are oriented dorsally. F. Mature sperm in head of a male dissected from the tube of paratype (SIO-BIC A7842). G. Transverse section (7 µm) through trunk of paratype (SIO-BIC A7843) showing extensive musculature and glands. Prominent dorsal and ventral blood vessels are also visible. H. Differential interference micrograph of male in the tube of paratype (SIO-BIC A7842). Prototroch is visible anteriorly as is a mass of mature sperm. Spermatid bundles (very squeezed) fill majority of body. Hooked chaetae are visible in expanded posterior region.