Ophiothrix spiniformis, Santana & Manso & Almeida & Alves, 2020

Santana, Alisson, Manso, Cynthia L. C., Almeida, Ana C. S. & Alves, Orane F. S., 2020, Taxonomic review of Ophiothrix Müller & Troschel, 1840 (Echinodermata Ophiuroidea) from Brazil, with the description of four new species, Zootaxa 4808 (1), pp. 51-78 : 62-64

Ophiothrix spiniformis n. sp.

( Figs. 8 , 9 )

urn:lsid:zoobank.org:act:0025BE2D-EFC5-4C8A-8261-8D6B1A6BF655

Ophiothrix cf. angulata: Alitto et al. 2019: 18–20 . [Paraná, Brazil]

Not Ophiura angulata Say, 1825: 145–146 . [South Carolina, United States]

Holotype: ZUEC 3060 (01 specimen), Paranaguá , Paraná, Brazil, 23º49’S, 45º24’W, 1 m, coll. 20/XII/2014 by M. Bueno . Paratypes: ZUEC 3061 (06 specimens), UFBA 01991 (02 specimens), MZUSP 02709 (01 specimen), 23º49’S, 45º24’W, 1 m, coll. XII/2014 by M. Bueno. Additional specimens: UFBA 01860 (01 specimen), Paraná, Brazil, 25º11’S, 44º57’W, 168 m, coll . III/2014 by M. Bueno.

Type locality. Paranaguá, Paraná, Brazil.

Etymology. The specific name alludes to the characteristic disc coverage of the species.

Diagnosis. Disc (interradial regions) covered by long spines with denticules over their entire length and spinelets at the apex; radial shields covered by short bifid and trifid spines; ventral arm plates with straight proximal edge.

Holotype description. A specimen with 5.33 mm of disc diameter. Five arms, 3–4 times as long as the disc diameter. Disc circular, 1.67 mm high; interradial regions covered by small, rounded and imbricated scales that support long spines, more than 1.5 mm high, with thorns over their entire length and crown of thorns at the apex. Central and radial primary plates not visible ( Figs. 8A, B ). Radial shields flat, scalene triangular, longer than wide, proximal edge tapered and distally rounded, covered by small bifid and trifid spines, separated by 1–2 elongated scales ( Fig. 8C ). Ventral interradius covered by imbricated scales with small bifid and trifid spines. Genital plates at the base of the arms. Oral shields spear-shaped, wider than long, sharp proximally and with the distal edge almost straight. Madreporite circular, inflated, longer than wide. Adoral shields in the shape of an equilateral triangle, tapered in all corners. Cluster of dental papillae on the apex of jaw and covering at least half the height of the dental plate. Infradental papilla and oral papillae absent ( Fig. 8D ). Oral tentacle pore visible. Arms dorsoventrally compressed, tapering gradually toward arm tip. Dorsal arm plates diamond-fan-shaped, longer than wide, with longitudinal black and white stripes ( Figs. 8E, G ). Ventral arm plates wider than long, with straight proximal edge, concave distally e expanded laterally in edge lateral-distal ( Figs. 8F, H ). Lateral arm plates occupying part of the dorsal surface of the arms; supporting proximally 7–9 vitreous arm spines and 4–6 distally, the second or third upper spine is the longest ( Figs. 9E, F ). Arm spines glassy, with marginal spines and a crown of spines at the tip ( Fig. 9E ); sometimes the lower spine modified into a hook. Arm spine articulation vertical, with two ridges slightly curved and opening at both ends, surrounding two circular openings with similar size. One spiniform tentacle scale. Arm vertebrae with zygospondylus articulation, with a dorsal keel extending distalwards into a large groove on the proximal face of the following vertebra. Zygocondyles dorsalwards converging and zygosphene fused with a pair of zygocondiles ( Figs. 9 A–D).

Variations. The disc varies from circular to pentagonal. The dorsal arm plates are diamond- to fan-shaped. The adoral shields may be more or less proximally separated from oral shields.

Color patterns. Ophiothrix spiniformis n. sp. is externally purple in color. The dorsal arm plates have longitudinal black and white stripes.

Remarks. As O. brasiliensis n. sp., specimens of Ophiothrix spiniformis n. sp. have previously been misidentified as O. angulata . Ophiothrix angulata is a species traditionally considered to have a high morphological variation but that, in fact, is diagnosed by having interradial regions of the disc and radial shields covered by bifid and trifid short spines (less than 1 mm long) and cordiform ventral arm plates with concave distal edge ( Santana et al. 2017). The spines of the interradial regions of O. spiniformis n. sp. are long, more than 1.5 mm high, and the ventral arm plates have a straight proximal edge, thus differing from O. angulata . Recently, Alitto et al. (2019) assigned some Brazilian specimens from São Paulo and Paraná to Ophiothrix cf. angulata . However, the description and figures provided by Alitto et al. (2019) show that the specimens analyzed by them differ from O. angulata in all previously mentioned characters, including the coverage of the disc and radial shields, the morphology of the spines (see morphological description and fig. 9A from Alitto et al. 2019) and arm plates (see morphological description and figs. 9F–G from Alitto et al. 2019). Thus, here we reassigned Ophiothrix cf. angulata studied by Alitto et al. (2019) to O. spiniformis n. sp.

Among the Western Atlantic species of Ophiothrix , O. spiniformis n. sp. most closely resembles O. suensoni and O. troscheli n. sp. by having long spines covering the interradial regions of the disc. The main difference between O. spiniformis n. sp., O. suensoni and O. troscheli n. sp. is the presence of short spines covering the radial shields of O. spiniformis n. sp., whereas the radial shields of both O. suensoni and Ophiothrix troscheli n. sp. are naked.

Other species of Ophiothrix from the Western Atlantic are distinct from O. spiniformis n. sp. by having a naked disc ( O. oerstedi ) or a disc covered by stumps ( O. spiculata , O. fragilis , O. stri , O. pallida , O. rudis , O. roseocoerulans , O. cimar , O. synoencina , O. hartfordi , O. brachyactis and O. lineata ), whereas the disc of O. spiniformis n. sp. is covered by spines.

Distribution. Western Atlantic: Brazil (Paraná).

Figures

FIGURE 8. Ophiothrix spiniformis n. sp.: A, Dorsal view of the disc; B, SEM of the disc spine; C, detail of radial shields covered by short spines; D, oral frame; E, dorsal arm plates; F, ventral arm plates; G, SEM image of dorsal arm plate; H, SEM image of ventral arm plate (ZUEC 02374, holotype, Paraná, Brazil). Scale bars: A, C–F = 1 mm; B = 500 μm; G–H = 100 μm.

FIGURE 9. SEM photographs of vertebrae and arm spines of Ophiothrix spiniformis n. sp.: A, proximal surface; B, distal surface; C, dorsal surface; D, ventral surface; E, lateral arm plate; F, arm spine (ZUEC 02374, holotype, Paraná, Brazil). Scale bars: A–D = 200 μm.