Cassidulus infidus Mortensen, 1948b

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 : 28-29

Cassidulus infidus Mortensen, 1948b

Figure 5 H–I

Cassidulus infidus Mortensen, 1948b: 215 , pl. 2, figs 6–8.― Mortensen, 1948c: 67.― Tommasi & Lima-Verde, 1970:

1.― Mooi, 1990: 75, fig 9b, 80.― Manso et al., 2008: 182, 184, figs 6a–d.― Souto et al., 2011: 39–48, figs 1–7.―Correia

& Sovierzoski, 2013: 680.

Cassidulus infindus Tommasi, 1966a: 21 .

Material examined. Photographic record.

Description (modified from Souto et al. 2011). Test small, wide and low, covered by short primary and secondary spines ( Fig. 5H ). Aboral surface inflated, with greatest height posterior to apical system, on small elevation above periproct. Apical system anterior and monobasal. Petaloid region occupying 1/3 of aboral region ( Fig. 5H ). Petals narrow, short, almost equal in length, and opened distally ( Fig. 5H ). Petal I slightly shorter than petal V. Poriferous zones almost equal in length. Interambulacral plates wide at ambitus and narrowing towards the apical disc. Four types of primary spines cover test. Aboral spines short, thick, distally serrated, with enlarged tip, sometimes club-shaped. Spines at bourrelets thick, serrated, slightly curved and with enlarged tip. Oral spines near ambitus are long, straight, smooth proximally, distally serrated and pointing towards centre line of test, partially covering naked zone. Spines above periproct long and straight, covering whole depression, and proximally serrated. Miliary spines throughout test small, serrated, widening to small crown distally. Tubercles slightly crenulate and perforate. Eight large periproctal plates and four to seven small periproctal plates. Oral surface concave, especially along midline. Phyllodes single-pored, parallel and enlarged near peristome, with 6–8 pores in each row. Peristome slightly wider than long and located in depression on oral region of the test, displaced towards anterior edge ( Fig. 5I ). Buccal spines long, obscuring peristomial opening.

Pedicellariae. Ophicephalous pedicellariae sparsely distributed on the aboral surface, but numerous near the ambitus. Tridentate pedicellariae only around the periproct and on periproctal plates ( Souto et al. 2011).

Colour. Information not available for living specimens. Whitish in ethanol.

Distribution. Endemic to Brazil, known from Bahia and Sergipe (R.B. Moura, personal observation). From depths of 3.5 to 11 m ( Manso et al. 2008; Souto et al. 2011).

Remarks. Four extant Cassidulus species are known, two of which are recorded from Brazil: C. infidus Mortensen, 1948 [from Bahia and Sergipe] and C. mitis Krau, 1954 [endemic to Rio de Janeiro]. Krau (1960) described C. delectus from Baía de Sepetiba (RJ), later synonimzed with C. mitis by Tommasi & Lima-Verde (1970). Mortensen (1948b) described C. infidus on the basis of a single naked test. Mooi (1990) summarized data, and provided a key on living cassiduloids, including both C. mitis and C. infidus . Twenty years later, Souto et al. (2011), redescribed C. infidus , illustrated several morphological characters, and presented a modified identification key for the species of the genus provided by Mooi (1990). Cassidulus infidus is apparently rare. On the other hand, Souto et al. (2011) believed that the difficulty in finding this species may be related to the fact that they are very small, fragile, and live buried in sand.

Ecological notes. This species lives in shallow and warmer waters, buried in medium-grained sand ( Manso et al. 2008; Souto et al. 2011). According to Telford & Mooi (1996), Cassidulus species are not selective deposit feeders and their juveniles inhabit exactly the same sediment as the adults, feeding on the same array of particle sizes. Souto et al. (2011) found sediment and Foraminifera in the gut contents of one specimen of C. infidus . Specimens measuring 10 mm in test length already have completely developed genital pores (Tommasi & Lima- Verde 1970). As in C. caribaearum Lamarck, 1801 and C. mitis , C. infidus broods its young among the spines of its aboral surface ( Tommasi & Lima-Verde 1970; Gladfelter 1978; Souto et al. 2011). According to Souto et al. (2011), C. mitis may have gregarious habits.

Figures

FIGURE 5. Morphological characters of Plesiodiadema antillarum (UFPB/ECH.2293). (A–G) and Cassidulus infidus (H–I). (A) Aboral view; (B) Oral view, arrow showing buccal plate; (C) Lateral view; (D–G) Illustrations of pedicellariae of P. antillarum from Mortensen (1904); (D) Valve of large form ophicephalous pedicellariae; (E) Valve of small form ophicephalous pedicellariae; (F) Valve of triphyllous pedicellariae; (G) Valve of tridentate pedicellariae; (H) Aboral view; (I) Oral view.