Ophiothrix troscheli, 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 : 67-69

Ophiothrix troscheli n. sp.

( Figs. 12 , 13 )

urn:lsid:zoobank.org:act:0CC39674-E8B0-4565-87CE-CBE7CB2556D0

Ophiothrix rathbuni: Borges et al. 2002: 63 , fig. 35a–b. [São Paulo, Brazil]

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

Not Ophiothrix rathbuni Ludwig, 1882: 1–26 . [São Paulo, Brazil]

Holotype: ZUEC 03062 (01 specimens), São Paulo, Brazil, 25º11’S; 44º57’W, 168 m, coll. 2000 by A.C.Z. Amaral . Paratypes: ZUEC 03063 (08 specimens) , UFBA 01990 (01 specimen) , MZUSP 02708 (01 specimen) , MZUSP 01521 (01 specimen), São Paulo, Brazil, 25º11’S; 44º57’W, 168 m, coll. 2000 by A.C.Z. Amaral . Additional specimens: MZUSP (01 specimen) 02975, Ilha Trindade , Espírito Santo, Brazil, 20°30’S, 29°18’W, coll. L . R. Tommasi ; MZUSP 01544 (01 specimen) , MZUSP 02976 (01 specimen), Cabo Frio , Rio de Janeiro, Brazil, 22º49’S, 41º58’W, coll. 1955–1957 ; MZUSP uncatalogued (01 specimen), Brazil, São Paulo (24º18’S, 44º50’W, 110 m, coll. 19/ VI /1962 by L. R. Tommasi ; MZUSP 01545 (01 specimen), Santa Catarina, Brazil, 27º43’S, 48º38’W, coll. 30.X.1959.

Type locality. Cananéia, São Paulo, Brazil

Etymology. Named in recognition of the contribution of Franz Herrmann Troschel (1801–1858) to zoology.

Diagnosis. Disc (interradial regions) covered by conical long spines; radial shields naked and triangular; ventral arm plate with angulated latero-distal edges.

Holotype description. A specimen with 12.22 mm of disc diameter. Five arms, 5 times as long as the disc diameter. Disc circular, inflated, 3.88 mm high; covered by elongated and imbricated scales supporting conical spines longer than 1 mm in length, with truncated apex. Central and radial primary plates not visible ( Figs. 12A, B ). Radial shields flat, scalene triangular, naked, longer than wide, proximally tapered, and distally rounded, separated by 1-2 scales, distally barely in contact ( Fig. 12C ). Ventral interradius covered by imbricated and elongated scales. Genital plates at the base of arms. Oral shields lozenge-shaped, wider than long, with proximal obtuse angle and distal and lateral edges rounded. Madreporite wider than long, lanceolate in shape. Adoral shields scalene triangular with rounded edges, tapered above the 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. 12D ). Oral tentacle pore visible. Arms dorsoventrally compressed, tapering gradually toward arm tip. Dorsal arm plates lozenge-shaped, longer than wide, with elongated proximal edge and rounded distal edge ( Fig. 12C ). Ventral arm plates with straight internal edge, concave laterally and distally, corners angulated ( Figs. 12E, F ). Lateral arm plates occupying part of the dorsal surface of the arms; supporting 8–10 vitreous arm spines proximally and 5–8 distally ( Fig. 12H ), the second or third upper spine is the longest ( Figs. 13E, F ). 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 zygocondiles ( Figs 13 A–D).

Variations. Sometimes, few short and smooth spines are among the long spines of the disc. The ventral arm plates can vary from square to rectangular in shape along the arm.

Color patterns. Ophiothrix troscheli n. sp. is pale-colored with brown or black spots placed at the corners of the radial shields and interradial regions of disc. The dorsal arm plates have the same pale coloration of the disc or have longitudinal black and white stripes.

Remarks. Among Ophiothrix species recorded from the Western Atlantic Ocean, Ophiothrix troscheli n. sp. most closely resembles O. lineata , O. rathbuni and O. suensoni in having naked radial shields. Ophiothrix troscheli n. sp. is differs from O. lineata , however, in having interradial regions of the disc covered by spines (in O. lineata the coverage is granules). Differences between O. troscheli n. sp. and O. rathbuni include de coverage of the interradial regions of the disc (with long distally truncated spines in O. troscheli n. sp. and with short bifid and trifid spines in O. rathbuni ) and the shape of the ventral arm plates (with angulated lateral distal edges in O. troscheli n. sp. and hexagonal or octagonal in O. rathbuni ). Ophiothrix troscheli n. sp. can be distinguished from O. suensoni by the shape of the disc spines (distally truncated in O. troscheli n. sp. and needle-shaped in O. suensoni ) and ventral arm plates (with angulated lateral distal edges in O. troscheli n. sp. and square in O. suensoni ).

Most species of Ophiothrix from the Western Atlantic including O. angulata , O. spiculata Le Conte, 1851 , O. fragilis (Abildgaard in O.F. Müller, 1789), O. stri Hendler, 2005 , O. oerstedi Lütken, 1856 , O. pallida Ljungman, 1872 , O. rudis Lyman, 1874 and O. roseocoerulans Grube, 1868 are distinguished from Ophiothrix troscheli n. sp. in having radial shields covered by spines. Additionally, O. cimar Hendler, 2005 , O. synoecina Schoppe, 1996 , O. hartfordi H. L. Clark, 1939 , O. brachyactis , and O. lineata Lyman, 1860 have the disc covered by granules. In this way, all these species are readily distinguished from Ophiothrix troscheli n. sp. that has naked radial shields.

Distribution. Western Atlantic: Brazil (Rio de Janeiro, São Paulo and Santa Catarina).

Figures

FIGURE 12. Ophiothrix troscheli n. sp.: A, Dorsal view of the disc; B, SEM detail of disc spines; C, detail of naked radial shields and dorsal arm plates; D, oral frame; E, ventral arm plates; F, SEM detail of ventral arm plate (ZUEC 00857, holotype, São Paulo, Brazil). Scale bars: A, C–E = 1 mm; F = 100 μm.

FIGURE 13. SEM photographs of vertebrae and arm spines of Ophiothrix troscheli n. sp.: A, proximal surface; B, distal surface; C, dorsal surface; D, ventral surface; E, lateral arm plate; f, arm spine (ZUEC 00857, holotype, São Paulo, Brazil). Scale bars: A–F = 200 μm.