Ophiothrix tommasii, 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 : 64-67

Ophiothrix tommasii n. sp.

( Figs. 10 , 11 )

urn:lsid:zoobank.org:act:BE2B77B4-3034-4375-9412-74CF7CE61CC1

? Ophiothrix angulata: Alitto et al. 2019: 17–18 . [São Paulo and Paraná, Brazil]

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

Holotype: UFSITAB 00741 , Maranhão, Brazil, 02º30’S, 44º01’W, 1 m, coll. III/2015 by J. Prata, R. Amorim and J. Araújo . Paratypes: UFBA 01833 (01 specimen) , UFBA 01834 (01 specimen) , UFBA 01835 (01 specimen), Maranhão, Brazil, 02º30’S, 44º01’W, 1 m, coll . III /2015 by J. Prata, R. Amorim and J. Araújo . Additional specimens: UFSITAB 00056 (01 specimen) , UFSITAB 00287 (01 specimen) , UFSITAB 00055 (01 specimen), Maceió , Alagoas, 09°34’– 09º53’S, 35º36’– 35º49’W, coll. 1966 ; UFBA 01413 (01 specimen), Salvador, Bahia, Brazil, 12º57’S, 38º21’W, 0 m, coll. VII/2006 by W. Magalhães; UFSITAB 00134 (01 specimen), Bacia de Campos , Rio de Janeiro, Brazil, 21°00’– 22º50’S, 40°00’– 41º58’W, 0–16 m, coll. 1957–2010 .

Type locality. São José de Ribamar, Maranhão, Brazil.

Etymology. Named in recognition of the contribution of Luiz Roberto Tommasi (1955–2010) to zoology.

Diagnosis. Disc (interradial regions) and radial shields covered by spines with 2–6 thorns at the tip, short spines on the first dorsal arm plate and ventral arm plates rectangular.

Holotype description. A specimen with 7.45 mm of disc diameter. Five arms, 4–5 times times as long as the disc diameter. Disc circular; interradial regions covered by small, rounded and imbricated scales that support spines shorter than 1 mm, with 2–6 thorns at the tip. Central radial primary plates not visible ( Fig. 10 A–C). Radial shields flat, scalene triangular, covered by short bifid and trifid spines, longer than wide, with proximal edge tapered and distally rounded, separated by 1–2 elongated scales, in contact distally, with sparsely distributed short spines ( Fig. 10D ). Ventral interradius covered by imbricated scales similar to the dorsal scales. Genital plates at the base of arms. Oral shields lozenge-shaped, with proximal edge tapered and distal and lateral edges rounded. Madreporite inflated but with a similar shape of other oral shields. Adoral shields with rounded edges, tapered proximal to oral shields. Cluster of dental papillae on the apex of the jaw and covering at least half the height of the dental plate. Infradental papilla and oral papillae absent ( Fig. 10E ). Oral tentacle pore visible. Arms dorsoventrally compressed, tapering gradually toward arm tip. Arms dorsoventrally compressed, tapering gradually toward arm tip. Dorsal arm plate diamond-shaped, wider than long, obtuse proximal angle and wide distal angle with central projection, projecting onto the proximal edge of the following plate; with short spines on the first plate ( Figs. 10D, F, H ); white or yellow stripes bordered by black stripes. Ventral arm plates rectangular, wider than long. The plates are contiguous along the entire arm; distal margin slightly concave. Lateral arm plates occupying part of the dorsal surface of arms; supporting 8–10 vitreous arm spines proximally and 6–8 distally, the third upper spine is the longest ( Fig. 10J ). Arm spines glassy, with marginal spines and a crown of spines at the tip ( Fig. 11E ); sometimes the lower spine modified in a hook. One spiniform tentacular scale ( Figs. 10G, I ). 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 pair of zygocondyles ( Figs. 11 A–D).

Variations. The ventral arm plates vary from rectangular to square in some arm segments.

Color patterns. The external coloration is generally purple, but can be orange. The dorsal arm plates are purple with longitudinal black and white stripes along the arms.

Remarks. At least four Ophiothrix species with interradial regions of the disc and radial shields covered by spines are reported from the Western Atlantic— viz. O. angulata , O. cimar Hendler, 2005 , O. oerstedi Lütken, 1856 and O. trindadensis . Ophiothrix tommasii n. sp. is readily distinguished from these congeners in having spines with 2–5 thorns at the tip and by the presence of short spines on the dorsal arm plate. Beside these characters, O. tommasii n. sp. most closely resembles O. angulata and O. trindadensis that also have the lower arm spine modified into a hook (absent in O. cimar and O. oerstedi ), but is distinct in the shape of the disc (circular in O. tommasii n. sp., pentagonal in O. angulata and O. trindadensis ), and ventral arm plates (cordiform in O. angulata and O. trindadensis , rectangular in O. tommasii n. sp.).

Alitto et al. (2019) assigned specimens from Paraná and São Paulo, south and southeast Brazil, to O. angulata . These specimens were not fully described and few taxonomic comments were provided. However, one figure was provided (see fig. 6 from Alitto et al. 2019) and at least the short spines on the first dorsal arm plate, only known in specimens of O. tommasii n. sp., are visible. Additionally, Alitto et al. (2019) refereed that they used the same specimens as Alitto et al. (2018). Alitto et al. (2018) provided a full description and detailed images of these specimens that show several differences between it and O. angulata , including the shape of the ventral (rectangular in specimens from Alitto et al. (2018, 2019) and cordiform in O. angulata ) and dorsal arm plates (diamond-shaped in specimens from Alitto et al. (2018, 2019) and fan-shaped in O. angulata ). Thus, here we assign O. angulata from Alitto et al. (2018, 2019) to O. tommasii n. sp.

Distribution. Western Atlantic: Brazil (Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Bahia, Espírito Santo, Rio de Janeiro, São Paulo, Paraná and Santa Catarina).

Figures

FIGURE 10. Ophiothrix tommasii n. sp.: A, Dorsal view of the disc; B–C, SEM detail of spines on the disc; D, detail of radial shields coverage; E, oral frame; F, dorsal arm plates; G, detail of spines on the first dorsal arm plate; H, ventral arm plates; I, SEM image of dorsal; J, SEM image of ventral arm plate (UFSITAB 00741, holotype, Maranhão, Brazil). Scale bars: A, D–H = 1 mm; B–C = 500 μm; I–J = 100 μm.

FIGURE 11. SEM photographs of vertebrae and arm spines of Ophiothrix tommasii n. sp.: A, proximal surface; B, distal surface; C, dorsal surface; D, ventral surface; E, lateral arm plate; F, arm spine (UFSITAB 00741). Scale bars: A–B, D = 200 μm; C = 100 μm; E = 500 μm.