Ophioderma africana, Stöhr & Weber & Boissin & Chenuil, 2020

Stöhr, Sabine, Weber, Alexandra Anh-Thu, Boissin, Emilie & Chenuil, Anne, 2020, Resolving the Ophioderma longicauda (Echinodermata: Ophiuroidea) cryptic species complex: five sisters, three of them new, European Journal of Taxonomy 600, pp. 1-37 : 19-22

Ophioderma africana sp. nov.

urn:lsid:zoobank.org:act:64021157-EA56-449B-9BCB-FD02F10CC67F

Figs 7–8 ; Table 1

Diagnosis

Mostly single dorsal arm plates, but several plates on some joints, eight arm spines, eight oral papillae. Colour dark brown dorsally, ventral disc as dark, ventral arms lighter brown, black and white spots along distal edge of dorsal arm plates. Maximum size under 19 mm dd (26 mm dd if non-type material is considered).

Etymology

The species is named for its area of collection, off (West) Africa.

Material examined

Holotype TROPICAL ATLANTIC OCEAN • Senegal, Dakar, Gorée Island, shipwreck Tacoma ; depth 10 m; 28 Aug. 2007; H. Zibrowius leg.; scuba diving, hand collected; under stones; preserved in 95% ethanol; SMNH-Type-7484.

Paratypes

TROPICAL ATLANTIC OCEAN • 22 specimens (6 sampled for both COI and nuclear markers, mitochondrial COI lineage L 5, nuclear cluster C 2); same data as for holotype; SMNH-Type-7485 • 1 specimen, ossicles, 4 remaining arms, 2 SEM stubs with ossicles; same data as for holotype; dried; SMNH-Type-7486 • 11 specimens (including a separate vial with eggs that were spawned during collection); same data as for holotype; initially in formalin, then 80% ethanol; SMNH-Type-7487 • 4 specimens (2 used for both COI and nuclear markers, mitochondrial COI lineage L 5, nuclear cluster C 2); Senegal, Dakar, Cap Manuel ; depth 7 m; 6 Sep. 2007; H. Zibrowius leg.; under stones; scuba diving, hand collected; preserved in 95% ethanol; SMNH-Type-7488 • 4 specimens (2 used for both COI and nuclear markers, mitochondrial COI lineage L 5, nuclear cluster C 2); Senegal, Madelene Islands ; depth 10–12 m; 9 Sep. 2007; H. Zibrowius leg.; among piled up rocks; scuba diving, hand collecting; preserved in 95% ethanol; SMNH-Type-9184 .

Other material

TROPICAL ATLANTIC OCEAN • 6 specimens (labelled as O. longicauda ); Senegal, between Gorée and Tiaroye ; depth 15–20 m; Feb.–Mar. 1952; Thorson leg.; preserved in ethanol; NHMD-225514 • 6 specimens (labelled as O. longicauda ); Senegal, Dakar; Jan. 1928; Sudan exped.; H. Madsen leg.; dried; partial sample; NHMD-225517 • 10 specimens (labelled as O. longicauda ); Dakar ; 6 Jan. 1928; Sudan exped.; H. Madsen & O. Hagerup leg.; preserved in in ethanol; partial sample; NHMD-225523 • 1 specimen (labelled as O. longicauda ); Senegal, Dakar, rocky coast; 3 Jan. 1928; H. Madsen leg.; preserved in ethanol; NHMD-225524 .

Description

Holotype ( Fig. 7 )

Disc diameter 18.7 mm, disc completely covered by small granules dorsally and ventrally ( Fig. 7 A–C), including the radial shields ( Fig. 7B ). Disc scales with granules crowding onto arm base, covering first dorsal arm plate except for a mid-distal portion, second plate also covered by scales and granules laterally ( Fig. 7 D–E). Dorsal arm plates flat, 2.5 times as wide as long, with straight distal edge, contiguous, mostly single, but joints with two plates common (often unequal in size) ( Fig. 7 D–E). Eight arm spines, ventralmost one thicker and slightly longer than others ( Fig. 7F ). Ventral disc covered by granules similar to dorsal disc. Eight conical oral papillae, Lyman’s ossicle and adoral shield spines hardly distinguishable ( Fig. 7G ). Two larger tooth papillae at jaw tips in line with oral papillae, blocklike teeth. Oral shields rounded triangular, slightly wider than long, madreporite slightly wider than other oral shields and with central round depression. Adoral shield long, narrow, extending around the lateral edge of the oral shield, separating it from the arm. Adoral shields covered with granules, similar to disc in size. Proximal genital slits about one joint long, distal slits about three joints long ( Fig. 7C ). Ventral arm plates contiguous, as wide as long, with wide proximal angle, convex distal edge ( Fig. 7F ). Two oval scale-like tentacle scales, superimposed on the ventralmost spine.

Disc dark brown dorsally, with some lighter brown patches. Dorsal arms dark brown, distally lighter and banded. Dorsal arm plates with small light brown and black dots along distal edge. Ventral disc as dark as dorsal, oral frame and ventral arms light orange brown ( Fig. 7A, C ).

Paratypes

Size range 12–18.4 mm dd. The specimens have dark brown to almost black dorsal discs (on some individuals with lighter patches), arms with dark and lighter bands. Ventral discs as dark as dorsal, oral frames and ventral arms lighter brown ( Fig. 7H ). Individuals with small light spots on the disc occur. Most specimens with black dots on the distal edge of the dorsal plates, but some without. Dorsal arm plates are mostly single, but most arms with several joints with two plates.

Skeletal elements ( Fig. 8 )

From specimen of 15.7 mm dd (SMNH-Type-7486) with mostly single dorsal arm plates but some small additional plates on few joints. Seven oral papillae, all similar except Lyman’s ossicle. Up to eight arm spines. Radial shields isosceles triangular with deeply concave abradial edge and abradial distal processes, distal center domed with small pores (the domed part is not covered by scales but with granules in the intact animal, all other areas are covered by scales) ( Fig. 8A, C ). Inner side of radial shield, on the distal articulation surfaces, two larger oval depressions and a smaller round one between these ( Fig. 8B ). Dental plate consists of several pieces with non-perforating sockets for 2–3 tooth papillae and single wide teeth, granule pores not obvious ( Fig. 8D ). Adradial genital plate blade-like flat with bulbous distal end and large pore, distal pit with knob on one side, two distal depressions on other side ( Fig. 8 E–F). Abradial genital plate much smaller and scale-like flat, distally wider than proximally ( Fig. 8G ). Oral plates longer than high, middle part slightly lower than ends, adradially with four oral papilla pores on ventral edge of proximal part, small granule pores at ventral edge ( Fig. 8I ). Adradial distal muscle fossa wide ventrally, tapering dorsalwards, shorter than plate height, articulation area slightly higher than wide ( Fig. 8H ). Suture line diagonally across oral plate mid-line, separated easily during preparation on several jaws. Vertebrae typically zygospondylus, with large dorsal and small ventral muscle flanges, no growth rings obvious ( Fig. 8 J–K). Lateral arm plates compact, weakly curved around the arm, strongly convex distally, concave proximally, with ventral excavation for tube foot opening ( Fig. 8 L–M). Two spurs at proximal external edge and counterparts on internal distal edge of lateral arm plates. Internal lateral arm plate with vertical row of three pores just below the plate centre, fourth pore in tentacle opening edge, bent vertical proximal ridge and small ventral knob, protruding beyond plate edge. Spine articulations inset in the distal plate edge with one thickened lobe, separating muscle and nerve opening.

Other specimens

The specimens from NHMD possess mostly single dorsal arm plates, on few joints there are more than one and some specimens have on the most proximal joints a mosaic of slightly tumid plates. Some specimens have naked radial shields. They have 7–9 oral papillae, among which the adoral shield spine and Lyman’s ossicle are sometimes obvious, differing in shape from the other papillae. They are uniformly dark brown or variegated dark, on both dorsal and ventral sides. They range in size between 19 and 26 mm dd and are assigned to O. africana sp. nov. mostly by colour pattern and exclusion of O. longicauda from off West Africa. The specimen NHMD-225524, which measures only 5.7 mm dd, has a light brown dorsal pattern with faint spots, a cream white ventral surface, and single dorsal arm plates, similar to O. guineense and is reassigned to that species.

Remarks

Ophioderma africana sp. nov. shares the dark colour on both sides of the disc with O. longicauda , its spine numbers fall within the variability of both O. longicauda and O. guineense , it has as few oral papillae as O. longicauda ( Table 1 ). These characters are however variable and small specimens may be difficult to identify. Nuclear and mitochondrial data were distinct from O. longicauda and all other clusters found ( Weber et al. 2019), placing O. africana sp. nov. in cluster C2 and COI lineage L5. Some of the animals started spawning during collecting, which indicates that the species is a broadcast spawner, not a brooder.

Figures

Fig. 7. Ophioderma africana sp. nov., digital images. A–G. Holotype (SMNH-Type-7484). A. Dorsal aspect. B. Dorsal disc. C. Ventral aspect. D–E. Two dorsal arms, note multiple dorsal arm plates on both. F. Ventral arm. G. Mouth. H. Some paratypes (SMNH-Type-7487).

Fig. 8. SEM images of skeletal elements of Ophioderma africana sp. nov., from paratype of 15.7 mm disc diameter (SMNH-Type-7486). A. Radial shield, external aspect. B. Radial shield, internal aspect. C. Scale-free part magnified from Fig. 8A, white arrowheads point to granule sockets and pores, white arrows point to larger peripheral pores. D. Dental plate fragments. E–F. Adradial genital plate, two opposite lateral aspects. G. Abradial genital plate. H. Oral plate, abradial face. I. Oral plate, adradial face, black arrows point to oral papillae sockets and pores. J. Arm vertebra, proximal face. K. Arm vertebra, distal face. L. Lateral arm plate, external face. M. Lateral arm plate, internal face. Abbreviations: dist = distal; dors = dorsal; prox = proximal; Sp = spurs; vent = ventral.