Echinoneus cyclostomus Leske, 1778

Figure 9 A–D

Echinoconus ovalis Breynius, 1732: 57 .

Echinoneus cylostomus Leske, 1778: 109, pl. 37, figs 4–5.― H.L. Clark, 1925: 177.― Tommasi, 1972: 29.― Magalhães et al., 2005: 63.

Echinoneus minor Leske, 1778: 174 .

Echinoneus semilunaris Gmelin, 1778: 3183 .

Echinoneus gibbosus Lamarck, 1816: 19 .

Galerites echinonea Des Moulins, 1837: 92 –93.

Echinoneus conformis Desor, 1842: 48 –49, pl. 6, figs 17–21.

Echinoneus cruciatus L. Agassiz in Desor, 1842: 46 –47, pl. 6, figs 1–3.

Echinoneus elegans Desor, 1842: 47, pl. 6, figs 7–9.

Echinoneus serialis Desor, 1842: 48, pl. 6, figs 10–12.

Echinoneus crassus L. Agassiz in L. Agassiz & Desor, 1847: 143.

Echinoneus orbicularis Desor in L. Agassiz & Desor, 1847: 144.

Echinoneus ventricosus L. Agassiz in L. Agassiz & Desor, 1847: 144.

Echinoneus abruptus H.L. Clark, 1925: 177 .

Material examined. Ceará: 2 spms, Canopos Bank [UFPB.Ech.1973]. Bahia: 2 spms, 12°57′28″S 38°21′22″W, Itapuã Beach, Salvador, 1 m, 19.II.2007 [UFBA00493]; 1 spm, Busca Vida Beach, Guarajuba, Camaçari, 21 m, VIII.2010 [UFBA01190]; 1 spm, Busca Vida Beach, 23 m, VII.2010 [UFBA01191]; 1 spm, Busca Vida Beach, 23 m, VII.2010 [UFBA01192].

Description. Test elliptical or oval (TL = 3.3 to 21.9 mm; TH = 2.9 to 9.4 mm), low, with rounded ends (Fig. 9A, C, D) and densely covered by slender, glassy and short spines. Peristome and periproct on oral surface (Fig. 9C). Apical system tetrabasal with four genital pores (Fig. 9A, B). Ambulacra narrow, ambulacra II, III and IV slightly narrower than ambulacra I and V (Fig. 9A, D). Petals undeveloped, pores double throughout and arranged uniserially. Interambulacra large, 1, 4 and 5 larger than 2 and 3 (Fig. 9A). Ambulacral plate trigeminate. Tubercles imperforate, smooth and non-crenulate (Fig. 9A, C, D). Pedicellariae present over whole test. Oral surface flat, except peristome, which is slightly concave (Fig. 9C). Periproct oval, close to the peristome, about twice the size of peristome (Fig. 9C). Peristomial plates diminishing in size from margin towards center. Peristome central or slightly anterior, oblique, and depressed (Fig. 9C). Periproctal plates imbricate, decreasing in size from margin to center.

Pedicellariae. According to Westergren (1911), ophicephalous pedicellariae are the most numerous, especially on the aboral side. Tridentate pedicellariae scarce and found only on the oral side of the test, near or a short distance from the peristome and periproct. Globiferous pedicellariae found only near the ambitus, and rarely on the apical system. Triphyllous pedicellariae found only rarely; when present, they occur mostly in the ambulacra.

Colour. From pale brownish cream to deep red, generally light red, with red tube feet (H.L. Clark 1921). According to Hendler et al. (1995), the tube feet vary from conspicuously brown to light brown and the spines are whitish to light brown. Naked test white or yellowish (Fig. 9 A–D).

Distribution. Circumtropical (Pawson et al. 2009). In the Western Atlantic from Mexico, Florida, Bahamas, Bermudas, Cuba, Jamaica, Puerto Rico, Haiti, Dominican Republic, Belize, Honduras, Bonaire, Costa Rica, Panama, Colombia, Aruba, Venezuela, and Brazil (Engel 1939; H.L. Clark 1925; Bravo-Tzompatzi et al. 1999; Borrero-Pérez et al. 2002; Alvarado 2011; Rodríguez-Barreras et al. 2012; Solís-Marín et al. 2013). In Brazil, from Bahia (Magalhães et al. 2005). In this study, we provide the first record for the State of Ceará. From 1.5 to 570 m (del Valle García et al. 2005), but most commonly occurs at shallow depths (Hendler et al. 1995).

Remarks. Echinoneus cyclostomus is the only extant species known in the genus. In the present study, both young and adult specimens were observed. Only small variations were recorded. In young individuals, the peristome is three to four times larger than the periproct. In adults this proportion is inverted. Young specimens have proportionally large tubercles relative to the corona. In adults, these tubercles are short. Westergren (1911) presented a broad morphological study for E. cyclostomus, illustrating in detail external and internal morphological characters and comparing specimens of different sizes from regions in the Pacific and Caribbean.

Ecological notes. This small urchin is usually found under rock slabs or fragments of coral rubble, sandy bottoms, seagrass beds, and muddy substrates (Hendler et al. 1995; Solís-Marín et al. 2013), or on coral reefs and isolated rocks over sandy substrates with abundant vegetation, mainly Thalassia testudinum (del Valle García et al. 2005). Echinoneus cyclostomus is a detritus-feeder, selecting food with the tube feet and spines, primarily ingesting Foraminifera and algal fragments (Rose 1976; De Ridder & Lawrence 1982). Echinoneus cyclostomus also ingests organic material that adheres to coarse sand and shell fragments (Hendler et al. 1995).