Encope emarginata ( Leske, 1778 )

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 : 40-42

Encope emarginata ( Leske, 1778)

Figures 14 A–I, 18 H, 19 E

Echinodiscus emarginatus Leske, 1778: 136, figs 5–6.

Scutella quadrifora Lamarck, 1816: 9 .

Scutella quinqueloba Eschscholtz, 1831: 18 –19, pl. 20: fig. 1.

Scutella cassidulina Des Moulins, 1837: 78 .

Encope emarginata L. Agassiz, 1841: 47 , pls. 7–8 (as E. valensii ), pl. 10.― Rathbun, 1879: 145.― Krau, 1950: 358.― Bernasconi, 1955: 64 –65, pl. 3, figs 1–2.― Tommasi, 1957: 21, 34, pl. 3, figs 1–2; 1959: 602, 603; 1964: 91–92; 1966a: 26, figs 54–55, pl. 7a; 1972: 32.― Brito, 1960a: 6; 1962: 6; 1968: 26–27, pl. 13, fig. 1–2.― Lima-Verde, 1969: 10.― Tommasi et al., 1988b: 2.― Manso, 1989: 357.― Fernandes et al., 2002: 422. – Ventura et al., 2007b: 279, tab. 11.2, 290, anexo 11.1; 2014: 65.― Manso et al., 2008: 183, figs 5d–f.― Oliveira et al., 2010: 10, fig. 4f. ― Miranda et al., 2012: 142, fig. 4f. ― Gondim et al., 2013b: 515.– Guilherme et al., 2015: 209 –220.– Alitto et al., 2016: 10.

Encope oblonga L. Agassiz, 1841: 53 –54, pl. 9, figs 1–7.

Encope subclausa L. Agassiz, 1841: 56 –57, pl. 5.

Encope valenciennesii L. Agassiz, 1841: 54 –56, pl. 7–8.

Mellita lobata L. Agassiz, 1841: 44 , pl. 4a, fig. 13, pl. 16, figs 4–7.

Moulinia cassidulina L. Agassiz, 1841:139 , pl. 22, figs 1–6.

Echinoglycus frondosus Gray, 1855b: 24 –25.

Encope ghiesbrechtii Belval, 1863: 419 –424.

Encope (Echinodesma) emarginata Phelan, 1972: 127 , 128.― Tommasi et al., 1988a: 5.― Magalhães et al., 2005: 63.― Lima & Fernandes, 2009: 57.

Material examined. Rio Grande do Norte: 1 spm, Diogo Lopes, Macau, 11.XI.2007 [UFPB/ECH.1299]; 2 spms, Ponta do Tubarão, Macau, 02.II.2011 [UFPB/ECH.1908]. Paraíba: 3 spms, Ponta de Campina, Cabedelo, 20.XI.1983 [UFPB/ECH.615]; 2 spms, 7°8′12,182″S 34°48′11,817″W, Project SEMAN, 04.X.2007 [UFPB/ ECH.865]; 1 spm, Areia Vermelha Reef, Cabedelo, 06.IV.2008 [UFPB/ECH.1214]; 2 smps, 6°56,139′S 34°49,391′W, Project Porto, Cabedelo, 09.II.2004 [UFPB/ECH.1298]; 1 spm, Ponta de Campina, Cabedelo, 20.XI.1983 [UFPB/ECH.1303]; 3 spms, Lucena Beach, Lucena, 07.X.2007 [UFPB/ECH.1305]; 18 spms, Ponta de Campina, Cabedelo, 20.XI.1983 [UFPB/ECH.1308]; 1 spm, Cabo Branco Beach, João Pessoa, 23.XII.2007 [UFPB/ECH.1309]; 5 spms, Costinha Beach, Lucena, 07.X.2007 [UFPB/ECH.1312]; 3 spms, receife em frente a Ponta de Campina, Cabedelo, 28.II.2010 [UFPB/ECH.1907]; 15 spms, Barra de Mamanguape, Rio Tinto, 13.I.2017 [UFPB/ECH.2286]. Pernambuco: 3 spms, Barra de Catuama, Goiana, 0 1.03.2008 [UFPB/ECH.1304]; 7 spms, Barra de Catuama, Goiana, 01.III.2008 [UFPB/ECH.1311]; 2 spms, Cayana, Goiana, 31.X.1982 [UFPB/ ECH.1313]. Alagoas: 3 spms, Pontal do Peba, Piaçabuçu, 27.I.1983 [UFPB/ECH.1291]; 1 spm, Paripoeira Beach, Maceió, 01.II.1983 [UFPB/ECH.1300]; 1 spm, Pontal do Peba, Piaçabuçu, 27.I.1983 [UFPB/ECH.1306]; 1 spm, Ipioca Beach, Maceió, 30.VI.2007 [UFSITAB-121]; 6 spms, Ipioca Beach, Maceió, 30.VI.2007 [UFSITAB-127]. Bahia: 5 spms, Ponta da Coroa Vermelha, Santa Cruz da Cabrália, 14.X.1982 [UFPB/ECH.1301]; 3 spms, Coroa Vermelha, Santa Cruz da Cabrália, 29.XII.1984 [UFPB/ECH.1310]; 1 spm, Coroa Vermelha, Santa Cruz da Cabrália, 29.XII.1984 [UFPB/ECH.1360].

Description. Test oval, domed centrally, with moderately thickened margin (TL = 119.2 mm; TW = 120.1 mm) ( Fig. 14 A–D). Apical system monobasal, with five gonopores ( Fig. 14I ). Petaloid large ( Fig. 14A, C ). Petals bowed and distally open ( Fig. 14C ). Posterior petals slightly longer than anterior ones ( Fig. 14C ). Six short, broad and drop-shaped lunules, larger in the anterior portion of the body ( Fig. 14 A–D). Anal lunule extends between posterior petals ( Fig. 14 A–D). Aboral primary spines short and club-shaped, uniformly covering test. Miliary spines with sac-like structure on tip, densely scattered among primary spines. Lunules with two types of spines; long spines, narrow at base and with broad tip (like swim fins) on aboral margins, and long, uniformly thin spines internally. Oral surface flat ( Fig. 14B, D ), with long and thin locomotory spines that are slightly curved at base, and short and slightly curved secondary spines. Peristome pentagonal, slightly anterior ( Fig. 14B, D ). Periproct oval and anterior to anal lunule ( Fig. 14B, D ), not in contact with basicoronal. Periproctal membrane covered by plates of variable shapes and sizes, largest occurring on distal margin of periproct. Basicoronal plate small. Five food grooves bifurcating at edge of basicoronal plates, each branch surrounding the lunules ( Fig. 14D ).

Pedicellariae. Pedicellariae over entire test, but more abundant on oral surface and near the lunules, peristome, and periproct. Bidentate pedicellariae with long neck and short head. Valves short, with narrow and slightly curved bases, median region enlarged with serrated margins and one end tooth, which crosses terminal tooth of opposing valve ( Fig. 14 E–H).

Colour. Brown or greenish ( Fig. 14A, B , 18H ). Naked test white ( Fig. 14C, D ).

Distribution. Florida, Belize, Guatemala, Panama, Caribbean Sea, Colombia, Venezuela, Brazil, and Argentina (mouth of La Plata River) ( H.L. Clark 1925; Tommasi 1966a; Francisco & Pauls 2008; Alvarado 2011; Kroh & Mooi 2016). In Brazil from AP, MA, PI, CE, PB, PE, AL, BA, RJ, SP, PR, SC and RS ( Bernasconi 1955; Brito 1962; Tommasi 1964, 1972; Lima-Verde 1969; Reichholf 1981; Manso 1989; Fernandes et al. 2002; Magalhães et al. 2005; Manso et al. 2008; Lima & Fernandes 2009; Gondim & Giacometti 2010; Oliveira et al. 2010; Gondim et al. 2011, 2013b; Lopes 2011). In this study, we provide the first record of this species for Rio Grande do Norte. From depths of 0 to 50 m ( Tommasi 1966a).

Remarks. The neotropical genus Encope contains seven extant species, of which only E. emarginata occurs along the Brazilian littoral. Encope emarginata differs from E. michelini L. Agassiz, 1841 , from the Gulf of Mexico, as the latter species has open lunules (notches). Young specimens of E. emarginata may be mistaken for E. michelini due to the presence of open lunules in the former when it is young ( Francisco & Pauls 2008). In the present study, only adult individuals were examined, and no morphological variations were observed. Ventura et al. (2010) analyzed the presence of morphological variations among seven populations from northeastern and southeastern Brazil and found that the thickness and shape of the test and the position of the lunule relative to the madreporite vary among five of the populations. According to these authors, these variants may be related to different environmental conditions to which the populations are subject to. Tommasi (1964) discussed differences between young and adult individuals. Recently, Coppard & Lessios (2017) conducted a phylogeographic study of Encope , finding that the phylogeny of the genus is characterized by four notable features, among which we highlight extreme morphological plasticity in the widespread species that does not show geographic structure, and an unusually slow rate of molecular evolution. These authors also corroborate that E. oblonga L. Agassiz, 1841 , E. subclausa L. Agassiz, 1841 , and E. valenciennesii L. Agassiz, 1841 are synonyms of E. emarginata .

Ecological notes. This species lives in sandy areas, mainly in the surf zone ( Fernandes et al. 2002). According to Brito (1962), E. emarginata is very common in Porto Seguro (BA). It is relatively common along the entire northeastern coast. In the present study, the species was observed to be more numerous in areas of hypersaline mangroves (Rio Grande do Norte), where it occurred together with M. aff. quinquiesperforata and L. sexiesperforata . As for these accompanying species, one or two small crabs, possibly belonging to the genus Dissodactylus , were found associated with the oral surface of E. emarginata ( Fig. 19E ). According to Tommasi (1964), young and adult specimens of E. emarginata live segregated into different depths, and the young tend to develop in shallow waters. As they grow, they migrate to deeper waters. Telford (1981) studied the morphology of sand dollars and its relation to hydrodynamic factors. He concluded that E. emarginata is a typically intertidal species with a body shape particularly adapted to its habitat.

Figures

FIGURE 14. Morphological characters of Encope emarginata (UFPB/ECH.1907). (A) Aboral view; (B) Oral view; (C) Aboral view of naked test; (D) Oral view of naked test; (E) Bidentate pedicellariae; (F–H) Valve of bidentate pedicellariae; (I) Apical system.

FIGURE 18. Some common echinoids from northeastern Brazil in their natural habitat. (A) Eucidaris tribuloides on coral reef; (B) Diadema ascensionis on barrier reef; (C) Echinometra lucunter on rhodolith bed; (D) Lytechinus variegatus near seagrass; (E) Tripneustes ventricosus on coral patch; (F-H) Mellita aff. quinquiesperforata, Leodia sexiesperforata and Encope emarginata, respectively, on muddy bottom of sandy beach near hypersaline mangroves.

FIGURE 19. Ecological aspects of some echinoids from northeastern Brazil. (A) Eucidaris tribuloides parasitized by eulimid gastropod (arrow); (B) Partial view of coastal reef eroded by Echinometra lucunter; (C) Lytechinus variegatus on coral reef exhibiting covering behaviour at night; (D) Dead specimen of Lytechinus variegatus recently preyed upon (arrow) by juvenile Cassis tuberosa; (E) Dissodactylus crab associated with oral surface of sand dollar Encope emarginata on sandy beach; (F) Diseased specimen of Mellita aff. quinquiesperforata; (G) Dead sand dollars (M. aff. quinquiesperforata) on sandy beach after disease outbreak.