Centrostephanus longispinus ( Philippi, 1845 )

Madeira, Patrícia, Kroh, Andreas, Cordeiro, Ricardo, De, António M., Martins, Frias & Ávila, Sérgio P., 2019, The Echinoderm Fauna of the Azores (NE Atlantic Ocean), Zootaxa 4639 (1), pp. 1-231 : 100-102

Centrostephanus longispinus ( Philippi, 1845)

( Fig. 21 )

Reports for the Azores:

Centrostephanus longispinus ( Peters, 1855) — $ Barrois 1888: 74; Koehler 1909: 220, pl. 31, fig. 20, 1921b: 113, fig. 74;

Centrostephanus longispinus ( Philippi, 1845) — Koehler 1914b: 277; Mortensen 1927a: 277, 1940a: 300–307, figs. 95c, 154– 156, pl. 34, figs. 1–11, pl. 35, figs. 11–12, pl. 75, figs. 5–24; $ Chapman 1955: 399; Harvey 1956: 63; Tortonese 1965: 311–312, figs. 143–145; $ Marques 1983: 4, fig. 5; Pawson & Miller 1983: 4, fig. 1; $ Wirtz & Martins 1993: 59; $ Morton et al. 1998: 76, fig. 4.2H; Pereira 1997: 333; $ Wirtz & Debelius 2003: 257; $ Micael et al. 2006: 5; $ Mironov 2006: 104–106; Schultz 2006: 91–93, figs. 164–168; Haddad & Barreiros 2008: 9; Micael & Costa 2010: 323, 2012: 4.

Type locality: Sicily, Mediterranean Sea.

See: Mortensen (1940a; 1951a: 296–297); Pawson & Miller (1983); Mironov (2006); Schultz (2006).

Occurrence: Mediterranean Sea and Atlantic, in the East Atlantic from Morocco south to Angola ( Cherbonnier 1959, Tortonese 1965), including the Azores ( Marques 1983), Madeira ( Augier 1985), Canary ( Bacallado et al. 1985) and Cape Verde archipelagos ( Mortensen 1927b) and Ampere, Gorringe, Josephine, Seine, Great Meteor, Dacia and Conception seamounts ( Mironov 2006); in the western Atlantic, reported from the Gulf of Mexico and the Caribbean to Brazil, including the Brazilian island of Trindade ( Pawson & Miller 1983; belonging to the Trindade and Martin Vaz Archipelago, not to be confused with the Caribbean island Trinidad).

Depth: 12–360 m ( Mironov 2006); AZO: 6–468 m (herein).

Habitat: detritic and rocky substrates ( Pawson & Miller 1983); feeds on bottom detritic material and algae ( Mortensen 1940a).

Larval stage: probably planktotrophic (inferred from the genus; see Emlet 1995).

Material examined: DBUA-ECH 001 (Piscina da Lagoa, SMG, AZO, c. 37°44’29”N, 25°34’27”W, 1996.07. 25, 15 m; 2 spms, D = 59 mm); DOP 5467 (Condor Seamount, AZO, 38°32’13”N, 28°59’06”W, 2010.08.06, 468 m; 1 spm, D = 10 mm); EMEPC-LUSO L09D9B03S01 (Gorringe Bank, NE Atlantic, 36°42’49”N, 11°09’54”W, 2009.09. 13, 130 m; 1 spm, D = 25 mm); MB-NMHN 382–20758 (Caloura, SMG, AZO, c. 37°42’46”N, 25°29’44”W, 1977, 8 m; 1 spm, D = 53 mm); MB-NMHN 388–20764 [Varadouro (submarine cave), FAY, AZO, c. 38°33’49”N, 28°46’28”W, 1979.08.02, 6 m; 1 spm, D = 30 mm]; MB-NMHN 422–20798 (Ponta da Galera, SMG, AZO, c. 37°42’20”N, 25°30’33”W, 1979, 18 m; 1 spm, D = 57 mm); MB-NMHN 435–20811 (Ponta Delgada harbour, SMG, AZO, c. 37°44’13”N, 25°39’26”W, 1982; 1 spm, D = 6 mm).

Description: test circular, flattened above and below, height about 50%D, though in most of larger specimens the test tends to be somewhat inflated adapically, reaching as much as 72%D. Ambulacra tuberculation typically composed of a single primary tubercle about the same size as the primary tubercles in the corresponding interambulacra (absent in the area above the ambitus), and one conspicuous smaller secondary tubercle located in the perradial median zone; pore pairs in a straight line adapically, changing to arcs of three closer to the ambitus and crowded at the peristomial edge; ambulacral area about 65 to 75% of the interambulacral area at the ambitus. In interambulacra, large primary tubercle occupying most of the plate; the small interradial space occupied by small secondary tubercles; the adradial area occupied by a larger secondary tubercle reaching a considerable size at the ambitus of larger specimens. Apical disc about 33 to 40%D; in larger specimens the ocular plates are insert; in the smallest specimen (MB-NMHN 435–20811, D = 6 mm) some of the plates are still exsert and no periproctal scales exist. In the second smallest specimen (DOP–5467, D = 10 mm) some plates are already present in the periproctal membrane and ocular plates I, IV, and V are insert; ocular plates naked or with one spine in the smallest specimens to up to two spines in the largest specimens; genital plates (madreporite inflated) bear up to three spines, with the exception of the smallest specimens in which the plates are naked or bear a single spine; the periproct is covered with small naked scales in the two smaller specimens; all other specimens have scales with spines, especially in the area surrounding the anal opening; gonopores not open in the two smallest individuals (± 10 mm D). Peristome larger in the smaller individuals, about 50%D diminishing proportionally in larger specimens to about 37%D; buccal membrane with plates particularly numerous in the ambulacral areas; paired buccal plates bear pedicellariae. Most of the spines were broken in all specimens, particularly in the ambital area; primary spines hollow, verticilate, and very fragile; spines on the oral side terminate in a crown shaped tip; on the apical side, the uppermost spines small club-shaped (claviform spines) with bright purple to pink tips (with the exception of the smallest specimen in which such spines are not yet present). Larger specimens black to dark brown or light brown in the case of the dry specimens from Museu Bocage; specimens of intermediate sizes (DOP–5467, EMEPC-LUSO L09D9B03) with the same pattern as the larger specimens, with the exception of the presence of a white line in the median area of both ambulacra and interambulacra; the smallest specimen (MB-NMHN 435–20811) almost white coloured, with the primary tubercles and the apical plating of a darker pinkish colour; spine colouration highly variable; the largest individuals (DBUA-ECH 001) with conspicuous dark coloured spines, though some of the spines presented a weak lighter red banding; spines of the largest dry specimens (MB-NMHN 422–20798 and MB-NMHN 382–20758) of a light brown colour at the basis, progressively changing to a more purplish tone or interchanging distally between the two colours, forming a banded pattern in many spines; all specimens of intermediate to smaller sizes with conspicuous yellow and purple to pinkish banded spines.

Remarks: until recently, the occasional reports of Diadema antillarum from the Azores were most likely a result of confusions with Centrostephanus longispinus . As was one time noted by Wirtz & Martins (1993: 59), ‘at least those along the coasts of Faial seen by us are a black colour morph of Centrostephanus longispinus and not Diadema antillarum ’. Nevertheless, and aside from morphological similarity between the two species, another possible source for such misidentifications is the unusual depth at which C. longispinus can occur in the Azores, as low as 5 m in sheltered areas such as ports or underwater cave-like habitats ( Chapman 1955; Wirtz & Martins 1993; Morton et al. 1998; Micael et al. 2006, personal observation).

The unusual black colour shown by some of the Azorean individuals in opposition to the typical lighter colours, as described for the type specimens from the Mediterranean Sea [ Philippi 1845, as Cidaris (Diadema) longispina ] is another reason for confusion. H.L. Clark (1921b) described a closely resembling species, C. rubricingulus , from the Caribbean, which according to Mortensen (1940a) could only be distinguished from C. longispinus by the interambulacral tuberculation, spine structure and pedicellaria morphology. The later author considered the colour pattern in C. longispinus far too variable to be considered as a diagnostic character. However, H.L. Clark’s and Mortensen’s descriptions were based on very few specimens available at the time. Later, Pawson & Miller (1983) based on new material agreed with Fell (1975) to treat the East Atlantic species as a subspecies of C. longispinus since they could not support any of the diagnostic characters pointed out by Mortensen (1940a). In addition, they concluded that the colour of the spines is a diagnostic character that can distinguish the western solid dark colour spines from the lighter banded colour spines of the eastern subspecies. Nevertheless, Pawson & Miller (1983) alerted that the absence of banding could only be expected in individuals larger than 25 mm in total diameter.

In the Azores, C. longispinus can adopt a large spectrum of colours from purplish with whitish-banded spines to solid black colour pattern, with no conspicuous banding of spines (see Marques 1983; Wirtz & Debelius 2003). Unfortunately, due to the very fragile nature of the spines in this species, the specimens herein examined were lacking most of the spines. Nevertheless, it was possible to confirm the presence of banding pattern in the spines of all but one specimen (DBUA-ECH 001, D = 59 mm). However, understanding that in larger specimens banding is not a constant trait of all spines in one individual and that frequently banding is present in the distal part of the spine only, it was impossible to determine whether this specimen could have any banded pattern present if all its spines had survived intact. The colour in the eastern form of C. longispinus is known to change under exposure to different light conditions, and the activity of black chromatophores is well studied in this species (e.g., Dambach 1969; Weber & Dambach 1974; Gras & Weber 1977). Additionally, Pawson & Miller (1983) mentioned that bleaching spines (i. e. removal of black pigment) from western Atlantic C. longispinus specimens uncover the presence of a banding pattern, in otherwise solid dark individuals. The material herein examined reveals yet another source of colour variation, the method of preservation. Marques (1983) described the specimens collected at the Azores during a 1979’s expedition as solid black with no banding pattern. On figure 5 presented by Marques one can clearly recognize specimen MB-NMHN 422–20798, the same specimen that now can be characterized by spines possessing a clear banding pattern ( Fig. 21F ). Thus, methods of preservation such as dehydration seems to mimic the effects of bleaching, possible due to the shrinkage or destruction of the black pigment chromatophores and tissue degradation, turning once black specimen into a ‘banded’ animal. Mironov (2006) studied the variation of reported diagnostic characters reported by Mortensen (1940a) and Pawson & Miller (1983) in specimens of C. longispinus throughout its geographical range. Although he did find some indication for a geographical gradient from east to west in the primary spines colouration of adult specimens, he regarded it as far too inconsistent to retain the subspecies. Our results agree with Mironov and we thus refrain from assigning the Azorean specimens to either subspecies. In contrast to Mironov (2006) who noted that the minimum total diameter at which the genital pores were developed was of 9 mm, the specimen of 10 mm D examined by us had no gonopores yet.

C. longispinus can be easily distinguished from other sea-urchin species inhabiting the Azorean coastal waters by its very long spines and the presence of conspicuous bright purple to pink claviform spines around the apical disc ( Fig. 21D ).

Figures

FIGURE 21. Centrostephanus longispinus (Philippi, 1845) (DBUA-ECH 001: A–D; DOP 5467: E; MB-NMHN 422–20798: F). Aboral view (A); oral view (B); lateral view (C); detail of the apical area showing claviform spines (D); aboral view of a juvenile (E); aboral view of a dry specimen (F).