Tripneustes ventricosus

Tripneustes ventricosus (Lamarck, 1816)

Figures 8 A–N, 18 E

Echinus ventricosus Lamarck, 1816: 44.

Hipponoë esculenta A. Agassiz, 1872: 135.― Rathbun, 1879: 144.

Tripneustes ventricosus Lamarck, 1816: 44.― Bernasconi, 1956: 119 –121, pl. 1, figs 1–2.― Brito, 1962: 6; 1971: 264, figs 1– 2.― Tommasi, 1966a: 15, fig. 22, pl. 3a; 1972: 27, fig. 55.― Lima-Verde, 1969: 10.― Tommasi & Aron, 1987: 3; 1988: 2.― Alves & Cerqueira, 2000: 547.― Fernandes et al., 2002: 422.― Magalhães et al., 2005: 63.― Ventura et al., 2007a: 252.― Xavier, 2010: 63.― Oliveira et al., 2010: 10.― Miranda et al., 2012: 142, fig. 4e.― Martins et al., 2018: 522, figs 10–11.

Heliechinus gouldii Girard, 1850: 365.

Tripneustes esculentus Bell, 1879: 657 –662.

Tripneustes esculenta Verrill, 1907: 324.

Material examined. Paraíba: 1 spm, Bessa Beach, João Pessoa, 31.V.1985 [UFPB/ECH.1361]; Project Algas—3 spms, 6°39′S 34°49′W, st. 77, 20 m, 28.V.1981 [UFPB/ECH.1630]; 1 spm, 7°31′S 34°31′W, st. 5, 34 m, 22.I.1981 [UFPB/ECH.1635]; 1 spm, 7°34′S 34°45′W, st. 1, 11 m, 21.I.1981 [UFPB/ECH.1637]; 1 spm, 7°28′S 34°40′W, st. 10, 14 m, 5.V.1981 [UFPB/ECH.1641]; 3 spms, 6°29′S 34°51′W, st. 88, 22 m, 5.VI.1981 [UFPB/ECH.1724]. Alagoas: 1 spm, Francês Beach, Marechal Deodoro, 29.I.1983 [UFPB/ECH.1725]; 1 spm, Francês Beach, Marechal Deodoro, 09.II.2011 [UFPB/ECH.1916]. Bahia: 2 spms, Itaparica Island, 22.XII.1985 [UFPB/ ECH.1722]; 1 spm, Itapuã Beach, 21.XII.1984 [UFPB/ECH.1723]; 1 spm, Arembepe Beach, Camaçari, 16.IX.1982 [UFPB/ECH.1726].

Description. Test hemispheric or approaching pentagonal, with oral side flat (TD = 8 to 95.3 mm; TH = 5.6 to 57 mm) (Fig. 8A, B, J, K). Apical system hemicyclic (Fig. 8J, L). Plates of apical system bearing many small tubercles (Fig. 8J, L). Ambulacra and interambulacra approximately same width (Fig. 8J, K). Ambulacral plates trigeminate, with pores arranged in three vertical series (Fig. 8M). Interambulacral plate with three to four primary tubercles (Fig. 8N). Primary tubercles forming three to four vertical series on the ambulacra and four or five horizontal series on each plate of ambitus (Fig. 8J, K, M, N). Primary spines small, whitish, with several longitudinal striae. Secondary spines similar to primary spines, but smaller. Tubercles non-crenulate and imperforate (Fig. 8J, K, M, N). Peristomial membrane with few plates, numerous ophicephalous pedicellariae surrounding mouth (close to buccal feet), and few, sparsely distributed triphyllous and tridentate pedicellariae (Fig. 8B, K). Buccal plates with many ophicephalous pedicellariae (Fig. 8B). Tube feet with C-shaped spicules (Fig. 8H).

Pedicellariae: Globiferous pedicellariae small and lacking a neck, abundant especially on the apical system and in interambulacra. There are three glands on the stalk and three associated with the valves. Valves long, proximal region broad, blade narrow with a long end tooth (Fig. 8C, D). C-shaped and dumbbell-shaped spicules found on all pedicellariae, being more numerous on the glands and in the areas close to the end tooth. Ophicephalous pedicellariae with short stalk, long neck (twice as long as stalk), and dumbbell-shaped spicules. Valves elongated, with broad areas for insertion of adductor muscle, and denticulate and serrate margin (Fig. 8E). Triphyllous pedicellariae with a long neck (almost as long as stalk) and short head, dumbbell-shaped spicules within entire pedicellaria. Valves short, proximal region short and narrower than distal portion, which is broader and longer (Fig. 8G). Tridentate pedicellariae with neck and stalk of about same size, bearing dumbbell-shaped spicules. Valves short, with base and lamina of the same size, blade serrate and denticulate at the tip (Fig. 8F).

Colour. Test appears uniformly dark brown, including the basal muscles of primary spines (Fig. 8A, B). Short primary and secondary spines white to dirty white (Hendler et al. 1995) (Fig. 8A, B). Naked test completely white (Fig. 8J, K).

Distribution. Gulf of Mexico, Mexico, Belize, Guatemala, Honduras, Cuba, Haiti, Dominican Republic, Puerto Rico, Nicaragua, Costa Rica, Panama, Colombia, Venezuela, and Brazil (Alvarado 2011; del Valle García et al. 2008; Kroh & Mooi 2016). In Brazil from RN, PE, AL, BA, SP, RJ, and SC, including Fernando de Noronha and Trindade Islands and Abrolhos Archipelago (Rathbun 1879; Bernasconi 1956; Tommasi 1966a; Lima-Verde 1969; Brito 1971; Tommasi & Aron 1988; Hendler et al. 1995; Fernandes et al. 2002; Magalhães et al. 2005; Lima & Fernandes 2009; Xavier 2010; Martins et al. 2018). In this study, we record T. ventricosus for the State of Paraíba. From 0 to 55 m depth (Hendler et al. 1995).

Remarks. Tripneustes contains four extant species (Bronstein et al. 2017), of which only T. ventricosus is recorded from the Brazilian littoral. Tripneustes ventricosus differs from its congener T. depressus A. Agassiz, 1863 by having a purple test, only two types of pedicellariae (ophicephalous and tridentate) and less numerous primary spines. Caso (1974a, b) provided important contributions on the morphology of T. ventricosus and distinguishing characters with regards to T. depressus. According to Hendler et al. (1995), T. ventricosus may reach a TD of 150 mm. In the present study, both young and adult specimens were analysed, but we failed to observe morphological variations, except for, apical system, which was dicyclic in young individuals and hemicyclic in adults. Tripneustes ventricosus is sexually dimorphic, with a long and tubular genital papilla in males, and short and conical genital papilla in females (Turner et al. 2010).

Ecological notes. This species lives in areas on sandy substrates with seagrass, and in cracks or in gravel in reef environments (Hendler et al. 1995). In Cuba, it was found in high densities near reefs, or in reef lagoons with or without marine phanerogams (mainly Thalassia testudinum and Syringodium sp.) (del Valle García et al. 2005). It feeds mainly on algae and detritus (Ventura et al. 2007a). Tripneustes ventricosus, like L. variegatus, displays a “covering behaviour” with shell fragments, gravel, and algae (Hendler et al. 1995). Along the littoral of northeastern Brazil, the species is usually not numerous, although population outbreaks have been recorded for some localities, such as the beaches of the Fernando de Noronha Archipelago (State of Pernambuco, Brazil). At Francês Beach (State of Alagoas), the species occurs in protected areas and in crevices and caves, sharing space with crinoids, hydroids, and sponges.