Moira atropos ( Lamarck, 1816 )

Gondim, Anne Isabelley, Moura, Rafael Bendayan De, Christoffersen, Martin Lindsey & Dias, Thelma Lúcia Pereira, 2018, Taxonomic guide and historical review of echinoids (Echinodermata: Echinoidea) from northeastern Brazil, Zootaxa 4529 (1), pp. 1-72 : 42-43

Moira atropos ( Lamarck, 1816)

Figure 15 A–J

Spatangus atropos Lamarck, 1816: 32 .

Echinocardium atropos Gray, 1825: 8 .

Schizaster atropos L. Agassiz & Desor, 1846: 22 .

Schizaster lachesis Girard, 1850: 368 .

Moera atropos A. Agassiz, 1863: 278 .

Moira atropos A. Agassiz, 1872: 146 , pl. 23.― Tommasi, 1958a: 5 –6, pl. 1, fig. 3.― Brito, 1962: 6; 1968: 30, pl. 15, figs 5– 6.― Bernasconi, 1955: 65 –67, pl. 4, figs 1–2.― Oliveira et al., 2010: 11, fig. 4h.

Moira atropus H.L. Clark, 1933: 89 .― Tommasi, 1966a: 19, figs 40, 80, pl. 5a.

Moira (Moira) atropos Mortensen, 1951: 329 .― Devaney, 1974: 127, 158.

Material examined. Sergipe: 2 spms, Atalaia Beach, Aracaju [UFSITAB-118]. Complementary material: 1 spm, São Sebastião Beach, São Paulo, X.1955 [ MZUSP, without voucher]; 1 spm, 22°30′S 41°23′W , Rio de Janeiro, 25.X.1963 [EqMN333] .

Description. Test subspherical or elliptical, covered with short, glassy and often curved spines (TL = 25 to 36.4 mm; TH = 19.3 to 31 mm; TW = 21 to 25.3 mm) ( Fig. 15 A–C). Apical system ethmolytic. Two gonopores. Anterior ambulacra (II, III and IV) narrower and longer than posterior ambulacra (I and V) ( Fig. 15A, D ). Ambulacrum III deeply sunken and broader than the others ( Fig. 15A, D ). Other ambulacra also deeply sunken, forming slit-like depressions on aboral surface ( Fig. 15A, D ). Peripetalous fasciole well-developed, bordering margin of petals ( Fig. 15A, D ). Lateroanal fasciole well-developed, often appearing as black line ( Fig. 15F ). Posterior region of test truncate ( Fig. 15 A–F). Periproct oval and longitudinal ( Fig. 15G ). Peristome kidney-shaped ( Fig. 15B, E ), covered by six or seven large plates. Labrum expanded, almost covering peristome ( Fig. 15E ). Amphisternous plastron covered by long and spatula-shaped spines ( Fig. 15B ). Crenulate and perforate tubercles ( Fig. 15 D–G).

Pedicellariae. Pedicellariae not observed, as only naked tests were available. The following descriptions were obtained from the literature. Globiferous pedicellariae with long and slender valves, curving abruptly at the tip. Foramen surrounded by six small teeth. Tridentate pedicellariae with curved and slender valves ( Tommasi 1958a). Chesher (1963) provided excellent illustrations of this character ( Fig. 15 H–J).

Colour. Light brown or yellowish to white ( Hendler et al. 1995). The spines, where more thickly clustered, are brownish ( A. Agassiz 1869). Fasciole often dark red-brown, horseshoe-shaped, and partially encircling apical system ( Hendler et al. 1995). Naked test white ( Fig. 15 D–G).

Distribution. North Carolina, South Carolina, Gulf of Mexico, Florida, Belize, Bermuda, Cuba, Jamaica, Puerto Rico, Dominican Republic, Guadalupe, Haiti, Honduras, Panama, Colombia, Venezuela, and Brazil ( H.L. Clark 1925; Borrero-Pérez et al. 2002, 2012; Alvarado et al. 2008; Smithsonian Database). In Brazil from SE, RJ and SP ( Tommasi 1958a; Oliveira et al. 2010). From depths of 0 to 445 m, more common in less than 50 m depth ( Serafy 1979; Laguarda-Figueras et al. 2005b).

Remarks. Five extant species of Moira are known, of which only M. atropos occurs in the Atlantic Ocean. According to Chesher (1963), adults may reach a maximum TL of 60 mm. In the present study, only adults were observed, lacking variations. Moira atropos is a very characteristic and easily identifiable species due to the strongly sunken petals.

Ecological notes. This species lives buried up to 15 cm in mud or mud-sand bottoms (del Valle García et al. 2005; Chesher 1963). It is a detritus feeder, extending the tubefeet of ambulacrum III in the direction of the surface through a tunnel constructed with sediment ( Chesher 1963). Moira atropos is frequently recorded together with Schizaster spp. and Brissopsis elongata Mortensen, 1907 . Among its main predators are the asteroid Luidia clathrata ( Say, 1825) and the margate fish Haemulon album Cuvier ( Hendler et al. 1995). The species is rarely collected, probably due to its burrowing habit. According to Brito (1962), this is a relative common species in São Sebastião, Santos, and Cananéia (São Paulo). However, in northeastern Brazil it is apparently rare. According to Chesher (1963), M. atropos lacks a mechanism to carry genital products from the neighbourhood of the genital pores to the water overlying the burrow. Therefore, this heart urchin likely ascends to the surface at fairly frequent intervals and there releases any available ripe sperm or eggs ( Moore & Lopez 1966). Moore & Lopez (1966) reported a significant correlation between spawning of M. atropos and lunar phases, with peak spawning occurring immediately after a full moon. According to Tommasi (1958a) the genital pores only appear in specimens larger than 57 mm TL. However, we observed specimens of 24.76 mm with open genital pores.

Figures

FIGURE 15. Morphological characters of Moira atropos (MZUSP00280). (A) Aboral view; (B) Oral view; (C) Lateral view; (D) Aboral view of naked test; (E) Oral view of naked test; (F) Lateral view of naked test; (G) Posterior view; (H–J) Illustrations of pedicellariae of M. atropos provided by Chesher (1963); (H) Valve of pedicellaria from floor of ambulacrum; (I–J) Valves of pedicellariae from aboral region. ab: aboral surface; or: oral surface.