Ophionereis reticulata ( Say, 1825 ), 2002

da Silva, Jailma Ferreira, Prata, Jéssica & Christoffersen, Martin Lindsey, 2023, Intraspecific variations in species of Ophiuroidea (Echinodermata) from the Tropical Southwest Atlantic, Northeast Brazil, Organisms Diversity & Evolution (New York, N. Y.) 23 (3), pp. 577-602 : 580-584

Ophionereis reticulata ( Say, 1825)

Material examined: 19 specimens. Carapibus Beach, Conde, PB: 7°18′03.0″S 34°47′53.0″W, 1 spec., UFPB / ECH-2430 ; 3 spec., UFPB /ECH-2435 ; 2 spec., UFPB / ECH-2437; 7°17′59.0″S 34°47′54.0″W , 1 spec., UFPB / ECH-2431 ; 3 spec., UFPB /ECH-2434. Barra de Mamanguape reefs, Rio Tinto, PB: 6°45′54.0″S 34°55′04.0″W , 1 spec., UFPB /ECH-2432. Bessa Beach , João Pessoa, PB: 7°04′33.0″S 34°49′30.0″W , 1 spec., UFPB /ECH-2433. Formosa Beach , Cabedelo, PB: 6°58′38.8″S 34°48′57.4″W , 2 spec., UFPB /ECH-2436. Cabo Branco Beach , João Pessoa, PB: 7°08′41.1″S 34°47′43.9″W , 5 spec., UFPB /ECH-2438 .

Specimens selected for description Young early stage: individual UFPB /ECH-2433, Bessa Beach, João Pessoa, PB; Young Intermediate Stage: individual UFPB /ECH-2434, Carapibus Beach, Conde, PB; Adult: individual UFPB /ECH-2438, Cabo Branco Beach, João Pessoa, PB.

Dorsal disc The young specimen in the early stage (DD = 2.96 mm) presents a circular disc, with indentations in the interradii, and dorsally covered by medium and imbricated scales. Visible primary scales highlight the central primary scale (cpp) that is circular and is surrounded by approximately five other larger, semicircular scales. The primary scales that cover the disc decrease in size up to the interradii portion, except for those close to the radial shields ( Fig. 1a ).

The disc from young intermediate specimens (DD = 9.31 mm) is pentagonal, the primary scales becoming more widespread and smaller until they are no longer visible ( Fig. 1e ). On the other hand, adult specimens (DD = 12.11 mm) have a circular disc, dorsally covered by small, imbricated scales, of which the largest are close to the radial shields and surrounding the disk ( Fig. 1i ).

The radial shields are initially arranged close to the arm, separate, small, wider than long, and with tapered proximal edges ( Fig. 1b ). With growth, they become larger, more separated, and slightly longer than in the previous stage ( Fig. 1f–j ).

Ventral disc In the young early stage, the ventral interradial regions have smaller scales than the dorsal regions, are without reticulations, have wide bursal slits, and extend to the third ventral arm plate, having some scales and visible genital papillae ( Fig. 1c ). In the intermediary stage, the bursal slits extend to the fifth ventral arm plate, and in the adult, the bursal slits extend to the seventh ventral arm plate, with genital papillae on its edges and large genital scales; both stages present scales of the interradii region similar to those of the dorsal region and have reticulations ( Fig. 1g –k ).

In individuals at the young early stage, the oral shields are robust, octagonal, as long as wide, with the proximal and distal edges slightly tapered; adoral shields scalene triangle-shaped, with proximal edges not touching, with robust madreporite similar to an arrowhead, with rounded distal edge, and some visible pores. Each half jaw with Lyman ossicle (LyOs) small, longer than wide, elongated proximal edge, first adoral shield spine (AdShSp), large, flattened, spatulate, wider than long, second adoral shield spine (2nd AdShSp) longer than wide, and two infradental papillae (Ip) ( Fig. 1d ).

In a young intermediate, the oral shields are more robust. In adults, the proximal edge is rounded and slightly tapered in the distal region; the adoral shields and the spines of each half jaw (LyOs, AdShSp, 2nd AdShSp) do not diverge from the young early stage ( Fig. 1h–l ). However, the adult has a madreporite with a small whitish circular depression in the middle portion and visible pores at the distal edge, and none, one or two Ip ( Fig. 1l ).

Arms In all stages, the number of five arms is maintained ( Fig. 1c, g, k ). Initially the dorsal arm plates are square, the distal edge straight and the proximal edge slightly rounded with an indentation ( Fig. 2a, c ); small accessory plates sickle-shaped (rectangle triangle) ( Fig. 2a, e ); rectangular ventral arm plates, tapered in proximal edge, and the lateral arm plates with circular indentation, providing the fitting of the tentacular scale ( Fig. 2b, d ); first ventral arm plate (1st vap) small, elongate, without lateral indentations ( Fig. 1d ); one large and spatulate tentacular scale present ( Fig. 2b ); lateral arm plates with proximal region curved, external part with three buttons “c”-shaped, very curved, parallel and separate, with articulation of the middle spine of the greater arm; articular tubercles of the dorsal spines (sa) more robust ( Fig. 3a, c ); internal part of the lateral plate with one single large perforation ( Fig. 3b ); wider arm spine in the proximal region ( Fig. 2f ).

In an intermediate specimen, the dorsal arm plates are trapezoid, slightly longer than wide, with distal edge straight and smaller than in young early stage ( Fig. 2g, i ); accessory plates bigger than previous stage ( Fig. 2g, k ); ventral arm AdShSp, adoral shield spine; 2nd AdShSp, second adoral shield spine; bs, bursal slits; cpp, central primary scale; Ip, infradental papillae; LyOs, Lyman ossicle; os, oral shields; rs, radial shields; 1st vap, first ventral arm plate

Adult specimen: m dorsal arm; n ventral arm; o dorsal arm plate; p ventral arm plate; q accessory plate; r arm spine. Abbreviations: ap, accessory plate; as, arm spine; dap, dorsal arm plate; ts, tentacular scale; vap, ventral arm plate plates wide, with deep lateral indentation ( Fig. 2h, j ); 1st vap ( Fig. 1h ) and tentacular scale ( Fig. 2h ) do not seem to differ from early stage. Lateral arm plate with proximal region more elongate ( Fig. 3f, h ), internal part with a single large perforation ( Fig. 3g ). Arm spine more elongate in distal region ( Fig. 2l ).

The adult presents dorsal arm plates wider than in previous stages, proximal plates with distal edge rounded and distal plates with distal edge straight, with slight indentation in proximal part ( Fig. 2m, o ); accessory plates robust, semicircular, occupying the entire side of the dorsal arm plate ( Fig. 2m, q ); ventral arm plates square, as long as wide, with a small indentation in the distal edge, while the lateral indentations become softer ( Fig. 2n, p ); 1st vap with proximal edge rounded ( Fig. 1l ); single tentacular scale large and spatulate, exceeding more than half of the ventral arm plate length ( Fig. 2n ). Lateral arm plates with three medium spines ( Fig. 3k–m ), with proximal region “c”- shaped, although more elongate and less curved than in young intermediate stage, the ventral region is narrower and more elongate ( Fig. 3k, m ), internal portion of the plate with a large perforation in ventral region ( Fig. 3l ). Arm spines more elongate, narrower and with slightly flattened apex, the middle one larger ( Fig. 2r ).

Color The young specimen has a whitish color, without reticulations in dorsal disc, only a few dark spots in the primary scales and in the radial shields; dorsal arms with dark and light transversal bands intercalated by four to three plates ( Figs. 1a and 2a ). Intermediate specimen is also whitish, without reticulations on the disc, with some lines near radial shields and, as the specimens grow, these lines become reticulations towards the center of the disk, becoming thicker and more abundant until they fill the entire surface of the disk, forming irregular circles ( Fig. 1e ). The adult presents a light brown color, with disc covered by fine dark brown reticulations that form non-uniform circles ( Fig. 1i ), arms with transverse bands that alternate between four to six lighter plates and one or more dark ones ( Fig. 2m ).

Microstructures The specimen in young early stage of growth presents microstructures with stereo more porous ( Figs. 2 , 3 , and 4). Oral plate longer than wide, external portion with a brief surface of the abradial musculature (Abmaa) ( Fig. 3d ), internal portion with abradial articulation area (Abaa) poorly defined, without stretch marks in the muscle attachment area, first and second oral tentacle compartment (1cot) robust, plateau of the oral spine with elongated perforations ( Fig. 3e ).

The specimen in young intermediate stage has microstructures slightly less porous than the initial stage ( Figs. 2 , 3 and 4 ). Oral plate as long as wide, external portion with Abmaa more defined and bigger ( Fig. 3i ), internal portion with Abaa defined, wider in the dorsal region, the striations of the muscular attachment are not yet formed, 1cot and 2cot robust, well demarcated ( Fig. 3j ).

The adult specimen with microstructures with low porosity and more delimited than in the young intermediate stage ( Figs. 2 , 3 , and 4). Oral plate wider than long, external portion with an Abmaa well delimited and bigger, radial canal (Rc) smaller than the previous stage ( Fig. 3n ), internal portion with Abaa narrower in the ventral portion, elongated in the region of the muscular insertion striations, which are positioned parallel or perpendicular, 1cot and 2cot robust ( Fig. 3o ).

Youngest specimen with elongated dental plate, external portion with two dental alveoli (td), where the proximal is bigger and semicircular, separated by thick buttons (pk); internal portion with two dental cavities divided into four small oval td separated by a narrow septum (sp) ( Fig. 4a ). In the young intermediate stage, the dental plate is wider in the proximal region, with external portion with two td, the most proximal bigger than the previous stage, the distal bigger and triangular; internal portion with two dental cavities divided by four td separated by a sp narrower than in the early stage ( Fig. 4e ). Adult presents proximal region with straight edge and rounded distal, external portion with two td and with more pk than the intermediate stage; internal portion with two dental cavities divided into four td separated by a robust sp ( Fig. 4j ).

Zygospondylic vertebrae. The young early stage with the vertebrae as long as wide in dorsal and ventral view, the medial portion of the dorsal vertebra is “v” shaped, with elongate end process (ep) and sulcus of the dorsal-distal muscular fossae (ddmf) narrow and deep ( Fig. 4b ); ventral view of the vertebrae shows an elongate and deep groove, with the junction of vg quite evident, especially in the zygosphene portions (zp) that are fused with the zygocondyle pair (zd), and projecting beyond the ventral edge of zd ( Fig. 4c ); vertebrae distal view wider than long, with dorsal muscular area (dma) bigger than the ventral (vma) ( Fig. 4d ).

In the intermediate specimen the vertebrae, in distal ( Fig. 4h ) and proximal view ( Fig. 4i ) with bigger dma and vma than in early stage. The other vertebrae do not show variations in comparison with the previous stage ( Fig. 4f, g ). The adult in dorsal view presents vertebrae with the medial portion “v” shaped, more robust ( Fig. 4k ), vertebrae in ventral view with elongate and deeper vg in the medial region, with the vg junction no more evident than in the early young and intermediate stages. In addition, the vertebra has four well-defined cavities, the proximal deeper, the distal shallow and rounded ( Fig. 4l ); vertebrae in distal and proximal view with dma much bigger than the vma ( Fig. 4m, n ).

cle attachment area; 1st cot, 1 compartment of the oral tentacle; 2nd cot, 2nd compartment of the oral tentacle; osp, oral spine plateau; pe, perforation; Rc, Radial channel; sa, spine articular tubercle mal. Abbreviations: ddmf, dorso-distal muscular fossae; dma, dorsal muscle area; ep, end processes; pk, protruding knobs; sp, septum; td, tooth sockets; vma, ventral muscle area; Vs, ventral groove; zd, zygocondyle; zp, zygosphene

Figures

Fig. 1 Ophionereis reticulata (Say, 1825). Early stage: a dorsal disc; b radial shield; c ventral disc; d jaw. Intermediate stage: e dorsal disc; f radial shield; g ventral disc; h jaw. Adult specimen: i dorsal disc; j radial shield; k ventral disc; l jaw. Abbreviations: ads, adoral shields;

Fig. 2 Ophionereis reticulata (Say, 1825). Early stage: a dorsal arm; b ventral arm; c dorsal arm plate; d ventral arm plate; e accessory plate; f arm spine. Intermediate stage: g dorsal arm; h ventral arm; i dorsal arm plate; j ventral arm plate; k accessory plate; l arm spine.

Fig. 3 Ophionereis reticulata (Say, 1825). Early stage: a–c lateral arm plates; d–e oral plate. Intermediate stage: f–h lateral arm plates; i–j oral plate. Adult specimen: k–m lateral arm plates; n–o oral plate. Abbreviations: abaa, abradial articulation area; abmaa, abradial mus-

Fig.4 Ophionereis reticulata (Say, 1825). Early stage: a dental plate; b vertebrae dorsal; c vertebrae ventral; d vertebrae distal. Intermediate stage: e dental plate; f vertebrae dorsal; g vertebrae ventral; h vertebrae distal; i vertebrae proximal. Adult specimen: j dental plate; k vertebrae dorsal; l vertebrae ventral; m vertebrae distal; n vertebrae proxi-