Ophiothrix rathbuni Ludwig, 1882

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 : 52-55

Ophiothrix rathbuni Ludwig, 1882

( Figs. 1 , 2 )

Ophiothrix rathbuni Ludwig, 1882: 1–26 . [São Paulo, Brazil]

Ophiothrix (Ophiothrix) rathbuni: Tommasi 1970: 60–61 , figs. 56–57. [Rio de Janeiro, São Paulo and Santa Catarina, Brazil] Ophiothrix rathbuni: Tommasi, 1971: 7–9 , figs. 21–23. [São Paulo, Brazil]

Ophiothrix (Ophiothrix) rathbuni: Albuquerque 1986: 178 , fig. 28a–c. [Amapá, Brazil]

? Ophiothrix rathbuni: Guille & Albuquerque 1987: 147 . [Abrolhos Archipelago, Bahia, Brazil]

Ophiothrix rathbuni: Borges 2001: 112 , figs. 1.58–1.60. [São Paulo, Brazil]

Ophiothrix rathbuni: Borges et al. 2002: 63 , figs. 35c–f, 36a–g, 37a–d. [São Paulo, Brazil]

Ophiothrix rathbuni: Borges et al. 2005: 67–67 . [São Paulo, Brazil]

Ophiothrix rathbuni: Borges et al. 2015: 376–377 (in part), figs. 34–36. [São Paulo, Brazil]

Material examined. MZUSP 01508 (04 specimens), UFBA 01888, UFBA 01242 (04 specimens), Ubatuba, São

Paulo, Brazil, 25º11’S, 44º57’W, 168 m, coll. I/1998 by A.C.Z. Amaral; ZUEC 01291 (05 specimens) , ZUEC 01784 (02 specimens), Ubatuba , São Paulo, Brazil, 23º34’S, 44º43’W, 48 m, coll. VII/1986 by A.M.S.P. Vanim; ZUEC 00238 (56 specimens) , ZUEC 00394 (01 specimen) , ZUEC 00395 (05 specimens) , ZUEC 00396 (01 specimen) , ZUEC 00859 (145 specimens), Caraguatatuba , São Paulo, Brazil, 23º44’– 24º26’S, 44º07’– 45º52’W, 40–500 m, coll. 1998–2001 ; ZUEC 00397 (01 specimen) , ZUEC 00932 (01 specimen), São Sebastião , São Paulo, Brazil, 23º46’– 23º58’S, 45º22’– 45º29’W, 28–45 m, coll. 1987–2001 ; MZUSP 01501 (01 specimen) , ZUEC 00396 (01 specimen) , ZUEC 00857 (12 specimens), São Paulo, Brazil, 24º33’– 25º37’S, 44º57’– 47º00’W, 0–168 m, coll. 1991–1998 ; MZUSP 01502 (02 specimens), Paraná, Brazil, 25º37’S, 45º11’W, 153 m, coll. I/1998 by Revizee / Score Sul .

Type locality. São Paulo, Brazil .

Diagnosis. Disc (interradial regions) covered by short bifid and trifid spines; radial shields triangular and naked; ventral arm plates wider than long, with proximal edge straight and concave distally.

Description. A specimen with 7.43 mm of disc diameter. Five arms, 2–3 times longer than the disc diameter. Disc circular, inflated, 3.23 mm high, interradial regions covered by small, rounded and imbricated scales that support short (less than 1 mm of length) and hyaline spines with bifid and trifid tips. Central primary plates and radial primary plates not visible ( Figs. 1 A–C). Radial shields flat, naked, scalene triangular, longer than wide, proximally tapered, separated by 1-2 scales and distally rounded, in contact ( Fig. 1D ). Ventral interradius covered by imbricated scales with short spines with bifid and trifid tips. Genital plates at the base of arms. Oral shields lozenge-shaped, as wide as long, proximally tapered and with a slight projection at the distal edge. Madreporite with a similar shape but wider and more inflated than other oral shields. Adoral shields triangular, tapered above oral shields and extended distally. 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. Oral tentacle pore visible ( Fig. 1E ). Arms dorsoventrally compressed, tapering gradually toward arm tip. Dorsal arm plates fan-shaped, longer than wide, elongated proximally and strongly convex distally ( Figs. 1F and 1H ). Ventral arm plates wider than long, with proximal edge straight and laterally and distally concave ( Figs. 1G and 1H ). Lateral arm plates covering part of the dorsal arm surface, bearing 7–9 arm spines, which are vitreous, 2.5 mm long, with marginal thorns and an apical crown of thorns, the second of third are the biggest and the lower spine can be modified into a hook ( Figs. 2E and 2F ). Arm spine articulation vertical, with two ridges slightly curved and open at both ends, surrounding two openings circular 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 zygocondiles ( Figs. 2 A–D).

Variations. The analyzed specimens have disc varying in shape from circular to pentagonal. The oral shields are generally lozenge-shaped, but the proximal and distal edges can become rounded. The adoral shields can be more or less connected proximally to the oral shields.

Color pattern. Varying from pink ( Tommasi 1970) to purple in color (present study). Some specimens have a white spot in center of the disc. The dorsal arm plates bear black and white stripes along its extension.

Remarks. Ophiothrix rathbuni was described by Ludwig (1882) based on specimens from São Paulo State, Brazil. No type material was designated by Ludwig (1882) and no information regarding the specimen repository Collection or Institution was given. However, since there is no doubt regarding the taxonomic status of O. rathbuni , the designation of a neotype is not needed, in accordance with Article 75.3 of the International Code for Zoological Nomenclature ( ICZN 1999).

Since the original description, O. rathbuni has been recorded from different localities at the Brazilian coast, including Amapá, Bahia, Rio de Janeiro and Santa Catarina States ( Tommasi 1970, 1971; Albuquerque 1986; Guille & Albuquerque 1987; Borges 2001; Borges et al. 2002, 2015). We analyzed specimens from all these localities, except Bahia. The record of O. rathbuni in Bahia was reported by Guille & Albuquerque (1987). Specimens studied in 1987 were reviewed by Albuquerque & Guille (1991), but the occurrence of O. rathbuni at Abrolhos Archipelago (Bahia State) was not confirmed. Here we present the first record of O. rathbuni from Maranhão and Espírito Santo States.

Tommasi (1970) differentiated O. rathbuni from other Ophiothrix from Brazil, based on the presence of a dark brown line on the dorsal arm plates. The pigmentation patterns of Ophiothrix species are highly variable and not consistent in delimiting species boundaries ( Hendler et al. 1995). Also, Tommasi (1970) stated that O. rathbuni has a disc covered solely by trifid spines, probably because of the limited accuracy of the microscope used at that time. Other descriptions of O. rathbuni from Brazil ( Borges 2001; Borges et al. 2005, 2015) noticed the presence of both bifid and trifid spines.

Among Ophiothrix species from the Western Atlantic, O. rathbuni resembles Ophiothrix troscheli n. sp. (see below), O. lineata Lyman, 1860 and O. suensoni by having naked radial shields. The main difference between O. rathbuni and these species is the type of coverage of the interradial regions of the disc (covered by short bifid and trifid spines in O. rathbuni ; with conical long spines in Ophiothrix troscheli n. sp.; covered by granules in O. lineata ; and with needle-shaped spines in O. suensoni ).

Distribution. Western Atlantic: Brazil (Amapá, Maranhão, Espírito Santo, Rio de Janeiro, São Paulo, Paraná, Santa Catarina and Rio Grande do Sul) ( Tommasi 1970, 1971; Albuquerque 1986; Borges 2001; Borges et al. 2002, 2015; present study).

Figures

FIGURE 1. Ophiothrix rathbuni: A, Dorsal view of the disc; B, SEM detail of bifid disc spines; C, SEM detail of trifid disc spines; D, naked radial shields; E, oral frame; F, dorsal arm plates; G, ventral arm plates; H, SEM of dorsal arm plate; I, SEM of ventral arm plate (UFBA 01242). Scale bars: A–G, F = 1 mm; H–I = 100 μm.

FIGURE 2. SEM photographs of vertebrae, lateral arm plates and arm spines of Ophiothrix rathbuni: A, proximal surface; B, distal surface; C, dorsal surface; D, ventral surface; E, lateral arm plate; f, arm spine (UFBA 01242) Scale bars: A–D = 200 μm; E–F = 100 μm.