Osedax jabba, 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 : 471-476

Osedax jabba n. sp.

Figures 9-13

‘spiral’, ( Braby et al. 2007; Katz & Rouse 2013; Rouse et al. 2015; Vrijenhoek et al. 2009; Worsaae & Rouse 2010) ‘sp.1 SBJ-2006’ (GenBank COI sequence DQ996622 - DQ996624 )

Material examined. Holotype: SIO-BIC A 7832 , Female (GenBank COI sequence FJ347638 ), fixed in glutaraldehyde preserved in formalin, 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’N) ROV Tiburon dive number 1069, Oct. 1, 2007. Allotypes, male in the tube of holotype, same catalogue number . Paratypes: Females, fixed in formalin or glutaraldehyde; preserved in formalin, glutaraldehyde or ethanol: SIO-BIC A7833 (GenBank COI sequence DQ996622 ), same locality as holotype, ROV Tiburon dive number 769, Nov. 11, 2004; SIO-BIC A1639 (GenBank COI sequence DQ996624 ), same locality as holotype, ROV Tiburon dive number 777, Jan. 6, 2005; SIO-BIC A7834, A7835 (GenBank COI sequence FJ347636 , FJ347637 ), same locality as holotype, ROV Tiburon dive number 777, Jan. 6, 2005; SIO-BIC A7838 (no GenBank COI sequence), same locality as holotype, ROV Tiburon dive number 917, Nov. 6, 2005; SIO-BIC A7836, A7837 (no GenBank COI sequences), same locality as holotype, ROV Doc Ricketts dive number 98, Nov. 19, 2009. Dwarf males (allotypes), fixed in formalin, preserved in formalin: SIO-BIC A7839 (no GenBank COI sequence), still in tube of female, same locality as holotype, ROV Tiburon dive number 932, Jan. 5, 2006.

Diagnosis and description. Holotype female ( Fig. 11E ), partially dissected from tightly surrounding tube; trunk demarcated into two regions, main part 5.6 cm long, 3.8 mm wide at base of main trunk, tapering to 2.3 mm at rounded tip of trunk ( Fig. 11E ). Lower trunk widens, greenish in life, and transitions into ovisac ( Figs 10D , 12B ). Trunk ‘deflated’ in width, but not contracted in length ( Fig. 11E ), when compared to images of living individuals in situ and some collected samples ( Figs 9 A-D, 10A-E 11A, B). Crown absent, no palps or emergent oviduct ( Figs 9 A-D, 10A-E 11A, B). Trunk and ovisac enclosed in tube in life ( Figs 9 A-D, 10A, 11A); preserved holotype has trunk occupying entire tube. Other specimens with trunk contracted to varying degrees within tube ( Figs 10A, E , 11A, B ). Oviduct ( Figs 11 C-E) runs dorsally along length of trunk from lower trunk/ovisac to trunk tip ( Figs 10 A- C, 11E). Main trunk color pink in live ‘contracted’ individuals ( Figs 10 A-D, 11E). In ‘inflated’ individuals, trunk is translucent ( Figs 10E , 11B ). Trunk in cross section shows extensive outer musculature and glands. Prominent dorsal and ventral blood vessels present as well as smaller vessels. Otherwise trunk is largely ‘empty’ with a few oocytes present and may filled (and inflatable) with coelomic fluid. ( Figs 12G, H ). A single large ganglion ventrolaterally in the mid-trunk region ( Figs 11B, F ). Lower trunk, demarcated by emergence of oviduct ( Fig.

12B), transitions to white cylindrical ovisac, wider than trunk, encased in the base of tube and extending posteriorly into sediment ( Figs 10D , 11A, E , 12B ). Ovisac wall translucent with ovaries visible inside ( Figs 10D , 12B ). Ovisac wall tissue extends posteriorly, becomes sediment encrusted and branches out forming a large root mass extending and branching in all directions ( Figs 11A , 12 A-F). Ends of the roots are attached to various bone fragments. Roots largely covered in sediment, either light brown or orange. Fine ends of roots branching over and attached to surfaces of bone fragments ( Figs 12 A-F). Numerous males in tube of holotype and paratypes, lying in tube lumen near oviduct at base of trunk Figs (10E, F). All dwarfs, ~200 µm long by 50 µm, with anterior prototroch and sperm with spiral nuclei in head region, two posteriorly expanded segments bearing hooked chaetae ( Figs 13 A-F).

Distribution. Known only from Monterey Bay, California from 2898 meters depth ( Table 2). Osedax jabba n. sp. was only found in sediment surrounding the natural whale fall at this depth ( Figs 9 A-D). Most specimens were at the head end of the whale, near a mass of baleen ( Fig. 9A ). All had bone fragments attached to the root mass buried in the sediment.

Etymology. The trunk of the new species is reminiscent of the tail of the mythical creature Jabba the Hutt from the Star Wars franchise ( Sansweet 1998). We name the new species (noun in apposition) in its honor.

Remarks. Osedax jabba n. sp. is the only member of Osedax Clade III and is the well-supported sistergroup to Osedax Clade IV, all of which have females that have four pinnulate palps. While the males of Osedax jabba n. sp. are similar ( Fig. 13 ) to the dwarfs found in other Osedax species ( Worsaae & Rouse 2010), the anatomy of the females is unique among Osedax species and they show what appear to be striking adaptations to exploit bone fragments that have become buried in the sediment. Further study on the roots of Osedax jabba n. sp. are underway (Rouse & Goffredi in prep.). The exploitation of buried bone fragments by Osedax jabba n. sp. does not explain the absence of palps in this species. Based on the phylogeny of Osedax , ( Fig. 1 ) this absence would appear to be a character loss. The presence of dwarf males towards the base of the tube is also unusual, as in other species the dwarfs tend to be found in the middle to anterior regions of the female tube ( Rouse et al. 2004; Rouse et al. 2008; Vrijenhoek et al. 2008) and it is not clear how larvae would be caught from the plankton and brought into the tube, as is surmised for other Osedax species ( Vrijenhoek et al. 2008).

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 9. Osedax jabba n. sp., previously Osedax ‘spiral’, sp.1 SBJ-2006. A. Anterior end of whale fall ‘Ruby’ at 2898 meters in September 2004. Baleen is prominent on surface of sediment in foreground with tubes (white arrows) of large chaetopterid annelidPhyllochaetopterus gigas(see Nishi &Rouse 2014).Littlebone obvious on sedimentsurface.Background has a cluster of more than10 Osedax jabban. sp. (blackarrow) with their tubes coming directly outof the sediment.B. Cluster of more the 10 (black arrows) Osedax jabba n. sp. at 2898 meters in November 2004. No obvious bone on the sediment surface. C. Two specimens of Osedax jabba n. sp. at 2898 meters in November 2005. Two prominent red blood vessels are visiblethroughthe tube ofeach specimen and theseindicate the trunk is occupyingwholeof tube and iscoiled anteriorly.Trunk does not appear to emerge from tube. D. Lateral view of an Osedax jabba n. sp. specimen emerging from sediment surface, though adjacent to a piece of bone, at 2898 meters in January 2006.Blood vessels are visible, indicating trunk is filling tube.

FIGURE 10. Osedax jabba n. sp., previously Osedax ‘spiral’, sp.1 SBJ-2006. A. Preserved paratype (SIO-BIC A1639) female, highly contracted and still in tube collectedat 2898 meters, Nov. 2004.Note absence of palps. B. Lateral view of trunk of preserved paratype (SIO-BIC A1639), showing oviduct running dorsally along trunk and terminating at anterior end of trunk. C. Dorsal view of posterior region of trunk of preserved paratype (SIO-BIC A1639) showing oviduct emerging from lowertrunk region.D. Lower trunk and ovisacof preserved paratype (SIO-BIC A1639).E. Photomontage lateral view of living paratype (SIO-BIC A7836) collected at 2898 meters, November 2009. Tube has been partly peeled away to reveal inflated trunk.Distal (anterior) part of tubeis intact and contains anterior part of the trunk that is not inflated (arrow).Oviduct is visible dorsally(left)and does not containany oocytes.Cluster of more than20 dwarf malesis present at thebase of the trunk.F. Close up of base of trunk of living paratype (SIO-BIC A7836) in 10E, showing scattered dwarf males lying on its surface. Oviduct is the white line in left of the image.Blood vessel inside transparent trunk is also visible.

FIGURE 11. Osedax jabba n. sp., previously Osedax ‘spiral’; sp.1 SBJ-2006. A. Image of live paratype (SIO-BIC A7837) female, still in tube, collected at 2898 meters in November 2009.Much of trunk is still relatively expanded, but anterior end is contracted(arrow pointsto tip of trunk) and trunk haspulled back along the tube.Mass of fine rootsis attached toseveral small pieces of bone. B. Ventral view of same specimen (SIO-BIC A7837) with sediment-covered part of the tube peeled away to show the transparenttrunk (arrow points to tip of trunk). Large ganglion is visible inventrolateral region of the trunk.C. Close up of dorsal mid-trunk of paratype (SIO-BIC A7837) female,showing oviduct filled with oocytes and an adjacent blood vessel. D. Another close-up of oviduct, more posteriorly near base of trunk, showing some dwarf males in vicinity of oviduct.Oocytes ellipsoidal, 150 µm by 120 µm. E. Living holotype (SIO-BIC A7832) collected October 2007 at 2898 meters with tube dissected open to show main trunk, which has largely ‘deflated’. Oviduct can be seen running along the trunk. Tube also contains lower trunk and ovisac region. Arrow points toposition of where 10 dwarf males were found in lumen of tube against body of the female.F. Close-up of large ganglion in trunk of paratype (SIO-BIC A7837) female, seen in Figure 11B.

FIGURE 12. Osedax jabba n. sp., previously Osedax ‘spiral’; sp.1 SBJ-2006. A. Lower trunk and roots and attached bone fragments of live paratype (SIO-BIC A7837) female. Two obvious roots forms; those emerging from ovisac are thick and covered in grey sediment and not directly in contact with bone. These branch into thinner roots that are covered in yellowish sediment. These thinner roots branch as well and cover the pieces of bone. B. Lower trunk and roots and attached bone fragments of preserved paratype (SIO-BIC A7838) collected June 2006 at2898 meters.Large mainroots can be seen emerging from posterior end of ovisac. C–F. Various view of finer roots of paratype (SIO-BIC A7838), showing how they branch and also are in contact with fragments of bone of various sizes. Root surfaces not in contact with the bone are covered in sediment. G. Transverse section (7 µm) of paratype (SIO-BIC A7835), near base of trunk where oviduct has emerged to the outer dorsal surface. As with other Osedax, there is an outer epidermis, circular and longitudinal muscles and glands, as well as two major bloodvessels. However, the majorityof thetrunk interior hasno obvious tissue, except for some minor blood vessels and a few oocytes. This interior space is interpreted here as the coelom. H. Another transverse section (7 µm) of paratype (SIO-BIC A7835) towards the distal (anterior) end of the trunk.The same basic structure as seen in G is also apparent here.

FIGURE 13. Osedax jabba n. sp., previously Osedax ‘spiral’; sp.1 SBJ-2006. A. Cluster of males lying between in tube lumen,in contact with the trunk of a female paratype 4 (SIO-BIC A7836).B. Photomicrographmontage ofmale allotype (SIO- BIC A7839), from tube of paratype 6 (SIO-BIC A7838). Prototroch is visible anteriorly, as is a mass of mature sperm. Some hooks are visible in expanded posterior region. C. Closeup of head showing prototroch and mass of mature sperm. D. Mature sperm squeezed out the head of male.E. Mature sperm.F. Close up of posterior segmented region showing hooked chaetae in pairs on one side of segments 2 and 3. Other chaetae are not in plane of focus.