Siboglinidae Caullery, 1914

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 : 459

Siboglinidae Caullery, 1914

Osedax Rouse, Goffredi & Vrijenhoek 2004

Diagnosis. Siboglinids with females having a contractile trunk, bulbous ovisac, and branching ‘roots’. A crown of palps usually present, with or without pinnules. Trunk lies within transparent tube emergent from bone surface. Mostly males are dwarfs resembling larvae, exceptionally having a crown, contractile trunk, bulbous testis sac, and branching ‘roots’, as in O. priapus . Crown in females, when present, comprised of cylindrical oviduct plus four palps. Osedax priapus , the only species known to produce adult bone-eating males, has crown with only two palps. No mouth or obvious gut. Cylindrical trunk comprised mostly of longitudinal muscles and glands, with large dorsal and ventral blood vessels present. Oviduct or sperm duct runs dorsally along trunk surface into posterior ovisac, or testis sac. Ovisac or testis sac enclosed by epidermis and trophosome with bacteriocytes, which also extends outwards as vascularized ‘roots’. No chaetae or segmentation apparent in females or bone-eating males. In most species, paedomorphic dwarf males cluster around oviduct in gelatinous tube surrounding trunk of female. The dwarf males possess anterior prototroch and posterior hooked chaetae arranged on two segments. Hooks, lacking rostrum, comprise capitium with curved teeth over subrostral process. Internally, males contain spermatids and sperm anteriorly.

Remarks. This diagnosis is revised from that in Rouse et al. (2004) to accommodate the diversity of Osedax forms. These include Osedax jabba n. sp. where the females lack palps entirely and Osedax priapus where the males are not paedomorphic dwarfs, but also consume bone and have similar anatomy to females. Many Osedax species have palps that lack obvious pinnules. The dorsal placement of the oviduct reflects the reorientation of Osedax as reported in Huusgaard et al. (2012) and Worsaae et al. (2016).