Ophiothela, Verrill, 1867

Alitto, Renata A. S., Bueno, Maristela L., Guilherme, Pablo D. B., Domenico, Maikon Di, Christensen, Ana Beardsley & Borges, Michela, 2018, Shallow-water brittle stars (Echinodermata: Ophiuroidea) from Araçá Bay (Southeastern Brazil), with spatial distribution considerations, Zootaxa 4405 (1), pp. 1-66 : 18-19

Ophiothela sp.

( Fig. 5 )

Material examined. 27 specimens (dd: 0.9–2.2 mm) from subtidal: ZUEC OPH 2189, St. IX, 1 spm; ZUEC OPH 2190, St. XI, 1 spm; ZUEC OPH 2193, St. XI, 1 spm; ZUEC OPH 2278, St. XXVI, 13 spms; ZUEC OPH 2298, St. 136, 10 spms; ZUEC OPH 2332, St. XXXIV, 1 spm.

Description. Disc: (dd: 2 mm) star-shaped, with interradial recesses, rounded granules scattered over the entire dorsal surface, larger between radial shields. Radial shields triangular, large (two-thirds of dd), united distally and separated proximally by one scale. Radial shield pairs separated by a narrow row of plates bearing granules. Central area depressed, radial shields elevated ( Fig. 5A ). Ventral surface covered by skin, translucent in dry specimens ( Fig. 5B ). Oral shields slightly broadened proximally. Adoral shields broadened distally and united proximally. Depression between two oral plates. A cluster of dental papillae on the dental plate and without lateral oral papilla ( Fig. 5C ). Oral tentacle pore large and opening at the mouth angle.

Arms: six arms, dorsoventrally coiled ( Fig. 5A ) and covered with scattered granules, dorsal arm plates not visible ( Fig. 5D ). Ventral arm plates three times as long as wide, distal region wider than the proximal, notch in distal edge, the first three plates contiguous, the others separated by lateral arm plates ( Fig. 5E,G ). Three to four arm spines, ventral shortest and bearing sharp teeth ( Fig. 5F ).

Lateral arm plates ( Fig. 5H,I ): general outline: ventral portion projecting ventro-proximalwards; ventro-distal tip not projecting ventralwards. Outer surface ornamentation: trabecular intersections protruding to form knobs larger than stereom pores on most of outer surface. Outer proximal edge: surface without discernible band of different stereom structure; without spurs; central part protruding; surface without horizontal striation. Spine articulations: on same level as remaining outer surface; dorsalwards increasing in size; distance between spine articulations equidistant. Lobes simply separated, equal-sized; lobes parallel, straight, oriented nearly horizontal; stereom massive; sigmoidal fold absent. Inner side, ridges and knobs: inner side apparently without knob and ridge; without additional dorsal structure on inner side; single large perforation on inner side.

Vertebrae: zygospondylous of aberrant type and keeled. Large groove on proximal side of vertebrae dorsally corresponding to distalwards projecting dorso-distal muscular fossae of distal side ( Fig. 5J ). Zygocondyles dorsalwards converging (they appear to be reduced and are difficult to observe) and zygosphene present and fused with pair of zygocondyles ( Fig. 5K ). Dorso-distal muscular fossae transformed distalwards clearly projecting beyond zygocondyles (true keel) ( Fig. 5L ). Zygosphene not projecting beyond ventral edge of zygocondyles ( Fig. 5M ).

Taxonomic comments. Ophiothela sp. was identified based on descriptions of the most comprehensive studies ( Verrill 1867; Clark 1976a; Cherbonnier & Guille 1978). The specimens were not identified to species level because the delineation of Ophiothela species is unclear with many overlapping features. Therefore, we emphasize the necessity of a taxonomic revision of this genus. The shape of the dorsal arm plate was not described due to the presence of granules, making it difficult to observe the edges of the plates. We also assume that the dorsal arm plates are very tiny as they were not observed under the stereomicroscope. The vertebrae were classified as an aberrant type because the zygocondyles and zygosphene were apparently absent or reduced, similar to findings of Viana (2010). This difference may allow it to flex its arms vertically ( Litvinova 1994). The number of arm spines ranged from three to four, with the ventral shortest and bearing sharp teeth in all our specimens. Presumably, the sharp teeth serve as hooks for adhesion ( Verrill 1867).

Remarks. 90% of specimens differed in the size of arms and disc due to their high degree of fission and regeneration. Ophiothela has a great variety of colors ( Clark 1976a). Orange and purple were observed in living specimens and reddish purple, cream, or white for those fixed in alcohol. Although this genus is commonly found on biological substrates, particularly gorgonians, it was collected on the soft bottom by dredge (99% of spms) and corer.

Distribution. Central Indo-Pacific (realm), Tropical Southwestern Pacific (province): Fiji Islands ( Verrill 1867). Western Indo-Pacific (realm), Western Indian Ocean (province): Madagascar ( Cherbonnier & Guille 1978), East African Coral Coast and Bight of Sofala/Swamp Coast ( Clark & Rowe 1971). Temperate Southern Africa (realm), Benguela (province): Namaqua; Agulhas (province): Agulhas Bank ( Clark 1974). Temperate Australasia ( Rowe & Gates 1995). Tropical Atlantic (realm), North Brazil Shelf (province): Guianan ( Hendler & Brugneaux 2013); Tropical Southwestern Atlantic (province): Northeastern and Eastern Brazil ( Hendler et al. 2012). Temperate South America (realm), Warm Temperate Southwestern Atlantic (province): Southeastern Brazil ( Hendler et al. 2012; Bumbeer & Rocha 2016; Mantelatto et al. 2016).

From intertidal up to 80 m depth ( Rowe & Gates 1995). The present study samples occurred at depths ranging from 2 and 21.5 m.

Figures

FIGURE 5. Ophiothela sp. ZUEC OPH 2193 (2 mm dd). (A) Dorsal view. (B) Ventral view. (C) Detail of the oral view. (D) Detail of dorsal arm. (E) Detail of ventral arm. (F) Detail of ventral-most arm spine. (G) Ventral arm plate. (H-I) Lateral arm plate. (J) Vertebra—proximal surface. (K) Vertebra—distal surface. (L) Vertebra—dorsal surface. (M) Vertebra—ventral surface. Abbreviations:ads: adoral shields; as: arm spine; cdp: cluster of dental papillae; d: dorsal; ddi: dorso-distal; dk: distal keel; ddmf: dorso-distal muscular fossae; di: distal; dp: dorso-proximal; gr: granule; jd: jaw depression; lg: large groove; os: oral shields; otp: oral tentacle pore; p: proximal; rs: radial shields; v: ventral; vap: ventral arm plate; vdi: ventro-distal; vp: ventro-proximal;zd:zygocondyle; zp: zygosphene.Stereomicroscope photos:(A)–(E), scalebar equal to 0.5mm.SEM photos: (F)–(M), scale bar equal to 100 µm.