Osedax ryderi, 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 : 469-471

Osedax ryderi n. sp.

Fig. 8

‘nude-palp-G’, ‘nude palp #20’ ( Higgs et al. 2014; Rouse et al. 2015)

Material examined. Holotype: Female, SIO-BIC 4617 (GenBank COI sequence KP119563 ), fixed in glutaraldehyde-preserved in ethanol, collected from a natural whale fall ( Eschrichtius robustus ) found at 2898 meters depth in Monterey Submarine Canyon , California (36°36.606’N; 122°26.122’W) ROV Doc Ricketts dive number 234, June 3, 2011. Allotype: Male found in tube of holotype, SIO-BIC A4618.

Diagnosis and description. Holotype female preserved partially dissected from bone; trunk contacted 0.6 mm long, 0.3 mm wide; crown of apinnulate palps contracted, 0.7 mm long ( Fig. 8B ). Tube not kept for holotype, but forms a tapering sheath in life, from which palps were not seen emerging ( Fig. 8A ). Oviduct slightly longer than palps visible in holotype ( Fig. 8B ). In life, palps reddish with two blood vessels each ( Fig. 8A ). Trunk with no obvious pigmentation or demarcation into upper and lower trunk. Ovisac represented as lobes on either side of trunk in holotype, extending laterally, or as long lobes in other specimens. Roots of holotype longer that the remaining body, extending in several directions as a single lobate mass ( Fig. 8B ). Male in a tube of holotype a dwarf, 210 µm long by 50 µm wide, with anterior prototroch and sperm squeezed out of head, two posterior expanded segments bearing hooked chaetae ( Figs 8C, D ). Another possible male, also in tube, resembled newlyrecruited Osedax larva ( Fig. 8E ).

Distribution. Known from Monterey Bay, California from 2898 meters depth ( Table 2). It has been found in whale and turtle bones.

Etymology. This species is named (noun in the genitive case) for Ryder Williams, for his generosity in sharing his mom for our research efforts.

Remarks. Osedax ryderi n. sp. is part of Osedax Clade II and is the well-supported sistergroup to Osedax ventana n. sp., another Monterey Bay species with an uncorrected divergence of 12%. Two other COI sequences obtained for specimens from the type locality, for which no voucher material was obtained, differed from the type specimen by less than 1% ( MG262308 from whale bone and MG262309 from turtle bone). There is little to distinguish Osedax ryderi n. sp. from other Clade II species, apart from genetic differences.

Figures

FIGURE 8. Osedax ryderi n. sp., previously Osedax ‘nude-palp-G’, ‘nude palp #20’. A. Live holotype (SIO-BIC A4617) female, with dwarf male allotypes(SIO-BIC A4618) in tube (not visible)before dissection from whale bone at 2898 meters.B. Preserved holotype, with intact ovisac. Trunk is short and the palps contracted to be shorter than oviduct. C. One of two males (SIO-BIC A4618) found in tube of holotype. Male has been squeezed with sperm coming out of head region. Prototroch is visible anteriorly with orange pigmentation. Several hooks are visible in posterior segmented region. D. Posterior segmented regionshowing hookedchaetae inpairs on one side of segments 2 and 3. Other chaetaeare not in plane of focus.E. Developing dwarf male (SIO-BIC A4618), or larval stage that has yet to become mature. No sperm or spermatids are visible in body. Prototroch is visible with prominent orange pigmentation and hookedchaetae are visible posteriorly.