Sphaerechinus granularis

Sphaerechinus granularis (Lamarck, 1816)

(Fig. 26)

Echinus brevispinosus Risso, 1826 — $ Drouët 1861: 210; Barrois 1888: 31;

Sphaerechinus granularis (Lamarck, 1816) — $ Agassiz 1863: 23, 1872: 159–160, 452–453, pl. 5a, fig. 7, pl. 6, figs. 16–17; p.p. $ Agassiz 1881: 106–107; $ Barrois 1888: 109–110; $ Simroth 1888: 231, 233; John 1889: 285; $ Koehler 1895a: 225, 1898: 23; Jackson 1912: 162; $ Nobre 1924: 89, 1930: 69; $ H.L. Clark 1925: 140–141; Mortensen 1927a: 309–312, figs. 178–180; $ Cadenat 1938: 367–368; Nobre 1938: 119–120, figs. 48, 49, 66; Mortensen 1943b: 515–526, figs. 242c, 309– 314, pl. 39, figs. 1–4, pl. 40, figs. 1–5, pl. 41, figs. 1–7, pl. 56, figs. 1, 8, 10, pl. 25, fig. 13; $ Chapman 1955: 399; Harvey 1956: 51, 66; $ Tortonese 1965: 323–327, figs. 151–154; $ Marques 1983: 5; Pereira 1997: 334; $ Maciel & Gonçalves 1998: 182; $ Morton et al. 1998: 150–151, figs. 3–3L1, 8–1L; Pérez-Ruzafa et al. 2002: 285; $ Wirtz & Debelius 2003: 258; $ Cardigos et al. 2005: 159; García-Diez et al. 2005: 50; Mironov 2006: 112; Schultz 2006: 266–267, figs. 509–513; Haddad & Barreiros 2008: 9, fig. 3d; Micael & Costa 2010: 323; $ Micael et al. 2010: 329; Madeira et al. 2011: 250, figs. 5B, 6B; Micael et al. 2012: 4.

See: Mortensen (1943b); Schultz (2006).

Occurrence: Mediterranean Sea and northeast Atlantic; from Channel Islands to the Gulf of Guinea (Mortensen 1943b), including the Azores (Marques 1983), Madeira (Alves et al. 2001), Selvagens (Pérez-Ruzafa et al. 2002), Canaries (Mortensen 1927b), Cape Verde (Agassiz 1881) and Gorringe and Dacia seamounts (Mironov 2006).

Depth: 0–120 m (Chapman 1955, Koukouras et al. 2007); AZO: 0–60 m (Chapman 1955, Marques 1983).

Habitat: generally found on hard substrates (AZO), but also on Posidonia and Zostera meadows, silty sand or maërl bottoms (Mortensen 1943b, Koukouras et al. 2007).

Larval stage: planktotrophic (Emlet 1995).

Fossil fauna: remains of this species, spines and test fragments were found in Pleistocene sediments at Santa Maria Island (Madeira et al. 2011).

Commercial value: edible (Tortonese 1965).

Material examined: DBUA-ECH 025 (S„o Roque Islet, SMG, AZO, c. 37°44’37”N, 25°38’19”W, 2006.11.07, 3 m; 1 bt, D = 54 mm); DBUA-ECH 026 (S„o Roque Islet, SMG, AZO, c. 37°44’37”N, 25°38’19”W, 2006.11.07, 3–5 m; 1 bt, D = 85 mm); DBUA-ECH 027 (S„o Roque Islet, SMG, AZO, c. 37°44’37”N, 25°38’19”W, 2006.11.07, 3–5 m; 1 bt, D = 82 mm); DBUA-ECH 028 (S„o Roque Islet, SMG, AZO, c. 37°44’37”N, 25°38’19”W, 2006.11.07, 3–5 m; 1 bt, D = 63 mm); DBUA-ECH 030 (Banco D. Jo„o de Castro, AZO, c. 38°13’18”N, 26°36’12”W, 2006; 1 spm, D = 70 mm); DBUA-ECH 031 (Banco D. Jo„o de Castro, AZO, c. 38°13’18”N, 26°36’12”W, 1996.07.02, 30 m; 5 spms, D = 81–87 mm); DBUA-ECH 032 (Cerco, Caloura, SMG, AZO, c. 37°42’26”N, 25°30’37”W, 20 m; bt, D = 21 mm); DBUA-ECH 054 (Santa Cruz, GRA, AZO, c. 39°05’16”N, 28°00’25”W, 2010.08.02, intertidal; 1 spm, D = 11 mm); DBUA-ECH 140 (Poças de Santa Cruz, GRA, AZO, c. 39°05’16”N, 28°00’25”W, 2010.08.07, intertidal; 4 spms, D = 37–54 mm); DBUA-ECH 158 (FRM, AZO, c. 37°16’14”N, 24°46’52”W, 1990.06, 45 m; 2 spms, D = 6–11 mm); MB-NMHN 410–20786 (Baixinha, GRA, AZO, c. 39°05’13”N, 27°59’09”W, 1979; 2 spms, D = 92–100 mm); MB-NMHN 285–18681 [Pópulo (Praia Grande), SMG, AZO, c. 37°45’00”N, 25°37’24”W, 1980; 1 spm, D = 55 mm]; MB-NMHN 368–20744 (Horta harbour, FAY, AZO, c. 38°31’51”N, 28°37’23”W, 1979; 2 spms, D = 12–18 mm).

Description: test circular, flattened orally, height reaching about 55–65%D, the peristome area is at most only slightly depressed. Apical disc hemicyclic, with Oc. I and V insert, though in the smaller specimens the latter can be exsert (D <11 mm). Periproct nearly ellipsoid, enclosing numerous periproctal plates of various sizes, many of which bear a slender spine; in smaller individuals periproct bearing one larger anal plate. Gonopores closed in the smallest specimens (D = 6 mm; DBUA-ECH 158). Ambulacra with irregular arcs of four or five pore pairs per plate in smaller specimens (D ± 30 mm) up to six pore pairs per plate in larger animals; in smaller specimens the number of pore pairs drop to five (D ± 30 mm) or four (D ± 11 mm). Number of ambulacral primary tubercles at the ambitus from one in small specimens (D ± 11 mm) up to two or three in larger animals; free space of both adradial and perradial zones filled with small secondary tubercles and miliary granulation. The number of primary tubercles in the interambulacra at the ambitus from two in small specimens (D ± 18 mm) up to six in large specimens (D Ξ 80 mm); adradial and interradial spaces filled by smaller secondary tubercles of various sizes. Peristome from 50–57%D in small specimens (D ± 11 mm) decreasing in relative size in larger specimens to about 22–25%D; buccal membrane with small embedded plates and devoid of spines. Gill slits well developed particularly in larger specimens, giving an overall almost pentagonal shape to the peristome. Presence of large globiferous pedicellaria (= 3 mm in larger specimens). Primary spines relative short and stout, with blunt tips. Colour: naked test purple or light brown; spines white, brown or bright violet with or without whitish tips; smaller specimens (D ± 11 mm) with green, orange or brown tests and primary spines white, bright pink, orange, reddish-brown or brown with or without whitish tips.

Remarks: Mortensen (1943b) reviewed the intraspecific variation in S. granularis, which included some of the Azorean specimens’ particularities, i. e. the higher number of pore pairs in the ambulacral plates. He rejected the hypothesis of specimens with six pore pairs per plate as belonging to a different species or a variety. Our results suggest that specimens with different number of pore pairs coexist in the same area. Furthermore, a higher number of pore pairs on the ambulacra is not exclusive for the Azores population. Agassiz (1872) reported specimens with six pore pairs from a batch from the Mediterranean Sea or Canaries (which location he did not specified), dismissing it as an ontological variation. Our observations, in contrast, agree with Mortensen (1943b) who showed that such differences are not dependent on the size of the animal. In spite of the intraspecific variation being overall constant throughout the species geographic range, we could not help notice the colour morph presented as ‘typical’ by several authors for the Mediterranean Sea is the purple/violet colour (e.g., Koehler 1921b; Mortensen 1927a; Tortonese 1965; Schultz 2006). In contrast, in the Azores, the brown colour morph appears very common if not the most common. Nonetheless, the presence of both colour morphs in the same area, or even clutching together to the same rock is not uncommon in the Azorean subtidal (personal observation).

The red colour morph of Genocidaris maculata, a species also native to the archipelago, have historically been confused with juveniles of S. granularis (Figs. 26 J-L; Koehler 1921b; Mortensen 1943b). For example, Agassiz (1881) recorded S. granularis from the Azores (H.M.S. Challenger, sta 75: 38°37’N, 28°30’W). On re-examination of this material, later authors (e.g., H.L. Clark 1925; Mortensen 1943b) realized that Agassiz failed to notice the presence of a reddish colour morph of Genocidaris maculata among the batch (see remarks under Genocidaris maculata).