Echinocardium cordatum ( Pennant, 1777 )

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 : 49-52

Echinocardium cordatum ( Pennant, 1777)

Echinus cordatus Pennant, 1777: 69 , pl. 34, fig. 75.

Spatangulus pusillus Leske, 1778: 230 , pl. 38, fig. 5.

Spatangus arcuarius Lamarck, 1816: 32 .

Echinocardium sebae Gray, 1825: 430 .

Echinocardium pusillus Gray, 1825: 430 .

Echinocardium australe Gray, 1851: 131 .

Echinocardium zealandicum Gray, 1851: 152 –157.

Amphidetus kürtzii Girard, 1852: 213 –214.

Amphidetus novaezelandiae Perrier, 1869: 176 .

Echinocardium cordatum Mortensen, 1951: 152 –156, pl. 28, figs 6–7.― Tommasi, 1966a: 18, figs 35–39.― Magalhães et al., 2005: 63.

Material examined. No specimens from Brazil were obtained for analysis. Complementary material: 1 spm, Gulf of Naples, Italy [EqMN315]

Description (modified from Chesher 1966 and Manso 2004). Test cordiform, rather thin, truncated, swollen at the posterior region, covered by short, slender, and vitreous spines. Apical system ethmolytic, with four gonopores. Ambulacrum III strongly sunken, with ambulacral pores arranged irregularly, becoming bigger from apical system towards oral surface. Spines from the margin of ambulacrum III larger than remaining aboral spines. Anterior petals longer than posterior petals. Subanal fasciole and inner fasciole well-developed. Three pairs of pore-bearing plates inside subanal fasciole. Peristome ventral, kidney-shaped, wider than long. Labrum short, bordered by two pairs of ambulacral plates. Amphisternous plastron swollen, covered by long, curved spines, with tips spatulate. Periproct oval on vertical truncate face, covered by plates that diminish in size from margin to center.

Pedicellariae. Ophicephalous pedicellariae more abundant around the periproct and tridentate pedicellariae distributed over entire test. Fistulate pedicellariae short, lacking a neck, with a crown of spines of variable sizes at the base of the stalk. Valves (shape similar to an Erlenmeyer flask) with proximal base long (corresponding to about a little over half the length of the valve) and broad, blade short and narrow, ending in a small oval foramen with a denticulate margin, and a large area of muscle insertion. Tridentate pedicellariae with stalk and neck short (both equal in length) and head long. Valves with proximal region short and blade long, with margin serrate.

Colour. Brown, yellowish or pinkish. Naked test white.

Distribution. Cosmopolitan ( Baker & Rowe 1990). In Tropical West Atlantic E. cordatum is only found in Brazil ( Solís-Marín et al. 2013). In Brazil from BA ( Tommasi 1966a; Magalhães et al. 2005). From depths of 0 to 230 m ( Solís-Marín et al. 2013), with densest populations occurring at depths of 40 m ( Duineveld & Jenness 1984).

Remarks. Presently 12 extant species of Echinocardium are known, only three of which occur in the West Atlantic Ocean ( E. cordatum , E. laevigaster A. Agassiz, 1869 and E. mortenseni Thiéry, 1909 ). Echinocardium cordatum differs from E. mortenseni (Gulf of Mexico and Mediterranean), in the latter having an oval to circular, short inner fasciole and subanal fasciole absent. It differs from E. laevigaster (Florida and Gulf of Mexico) mainly by having a narrow, shallow ambulacrum III. The taxonomic status of E. cordatum has been the focus of heated discussion. Some authors detect strong resemblances with E. fenauxi Péquignat, 1963 ( Chenuil & Féral 2003) from the Mediterranean Sea. Furthermore, recent studies indicate that E. cordatum is a cryptic species complex ( Egea et al. 2016). Despite several attempts, both morphological and genetic, to resolve the taxonomy of this species (e.g. Higgins 1974; Chenuil & Féral 2003; Féral et al. 1995; Laurin et al. 1994), its status remains confused. Féral et al. (1998) analysed specimens of E. cordatum from the Atlantic and the Mediterranean and did not detect genetic differentiation. Gordon (1927) and Duineveld & Jenness (1984) provide an excellent account of the ontogenetic development of E. cordatum .

Ecological notes. This species lives buried in the sediment, mostly in fine to muddy sand and mud in depths from 10 to 20 cm ( Tommasi 1966a; Chenuil & Féral 2003). It feeds on decomposing material ( Nichols 1959). According to Rolet et al. (2012), E. cordatum is the best-studied spatangoid regarding ecology and physiology, especially in New Zealand, Japan, and the Mediterranean Sea. In Brazil, the species is apparently rare, having been recorded only in estuarine habitats (Baía de Todos os Santos and Baía de Aratú) ( Magalhães et al. 2005).