Salenocidaris varispina Agassiz 1869

Salenocidaris varispina Agassiz, 1869

(Fig. 22)

Salenia varispina (Agassiz, 1869) — $ Agassiz 1881: 55–56, pl. 4, figs. 1–2;

p.p. Salenia hastigera Agassiz, 1879 — $ Koehler 1895b: 228, 1909: 219–220;

Salenocidaris varispina Agassiz, 1869 — Mortensen 1927a: 289; $ Mortensen 1935: 350–354, fig. 193a, pl. 66, fig. 9, pl. 84, fig. 4, pl. 85, figs. 3–4, 8, 16–17, 37; $ Mironov 2006: 106; Mironov 2014: 122–123.

Type locality: Off Double Head Shot Key, Cuba.

See: Agassiz (1869: 254–256); Mortensen (1935); Mironov (2006).

Occurrence: cosmopolitan, known from the Atlantic and Pacific Oceans (Mironov 2006); in the west Atlantic from south of Cape Cod to Brazil (Agassiz 1881, Serafy & Fell 1985), and in the east Atlantic from Bay of Biscay to off Ascension Island (Agassiz 1881, Mortensen 1935), including the archipelago of the Azores, and the Atlantis, Tropic and Antialtair seamounts (Mironov 2006).

Depth: (?290) 610– 2,600 m (Mironov 2006); AZO: (?718) 1,165 –1,830 m (Agassiz 1881, Koehler 1909).

Habitat: typically found on fine-grained sediments (Agassiz 1881); feeds on bottom material, including foraminifera (Mortensen 1935).

Larval stage: planktonic (Mortensen 1935).

Material examined: EMEPC-LUSO L09D22S1 (D. Jo„o de Castro Bank, AZO, c. 38°14'02"N, 26°33'37"W, 2009.10.09, 718–825 m; 1 bt, D = 2 mm); EMEPC-LUSO L09D25ARB21 (between S„o Jorge and Pico Island, c. 38°36'19"N, 28°06'47"W, 2009.10.21, 1,179 m; 1 spm, D = 3 mm).

Description: test small, low and hemispherical with a flattened oral side. Apical disc dicyclic, relatively large (about 80%D), occupying much of the aboral side. Plates of the apical disc densely ornamented with rough papillae arranged somewhat concentrically. Periproct off centre and angular, larger than the suranal plate. No genital pores open. Ambulacral plating simple except for plates adjacent to the peristome, which are bigeminate. Pores small; pore areas slightly widened at the peristome. One primary tubercle per ambulacral plate, slightly smaller than the corresponding one in the interambulacra. A pair of sphaeridia at the peristomial edge of each ambulacrum. Interambulacral plates each with a single, large, crenulated and non-perforated primary tubercle. Primary spines long, slender and verticillated, more than twice the size of the test (broken off at the tips); milled ring prominent; thorns developed primarily on upper (aboral spines) or lateral sides (oral spines). Secondary spines spatulated and rather broad. Periproctal spines short, thick and club-shaped to almost globular. Tridentate pedicellariae could not be found. Triphyllous and ophicephalus pedicellariae common, including the distal area of the apical disc. Colour (in ethanol): periproct deep purple; apical disc, peristome and secondary spines purple; tube feet cream white; primary spines uniform white with a purple base.

Remarks: as with other Salenocidaris recorded from the archipelago, S. varispina was frequently misidentified, confused with the close resembling species, S. profundi and S. hastigera. For example, Mortensen (1935) reexamined a small specimen from Princesse Alice collected in Azorean waters (sta 578: 38°26’00”N, 26°30’45”W, 1,732 m) previously identified by Koehler (1909) as S. hastigera, and reassigned it to S. varispina. Nevertheless, more recently, Mironov (2006) found four specimens of S. varispina collected north of S„o Miguel Island by the Jean Charcot (Biacores cruise, sta 179: 38°05’30”N, 25°46’30”W, 1,590 –1,665 m), further substantiating the presence of this species in the archipelago.

The main diagnostic character of S. varispina is the relative short and wider valves of its tridentate pedicellariae (Mironov 2006). Other characters are also used to distinguish this species from S. profundi or S. hastigera are: broader interambulacral areas, broader secondary spines, thick and short periproctal spines and shorter and less thorny spines with the thorns only well developed in the adapical side (Mortensen 1935; Mironov 2006). In spite of the colour variability presented by S. varispina the presence of a dark purple periproct is also considered characteristic of this species (Mortensen 1935; Mironov 2006). The specimens herein examined were small (D <3 mm) and not fully developed. Also, both lack important diagnostic characters as no tridentate pedicellaria were present. However, we feel confident that they belong to S. varispina. The complete specimen (EMEPC-LUSO L09D25ARB21) presented many of the typical features of S. varispina, particularly the deep-purple periproct. The ornament of the primary spines varied slightly from typical S. varispina. This deviation could be dismissed as age dependent based on previous observations by Mortensen (1935). The identification of the naked test (EMEPC-LUSO L09D22S1) was less safe as most of diagnostic characters in this genus rely on external appendages, none of which were present. However, comparing the test of both specimens they are nearly identical with comparable arrangement and ornamentation of the apical disc and the plating and tuberculation of the ambulacral and interambulacral areas. The known depth ranges of S. hastigera (370– 2,605 m) and S. varispina are similar (650– 2,600 m), though the former is also known from shallower depths outside the Atlantic (Mironov 2014). Reports in the Azores appear to follow the same general pattern, though S. varispina (1,165 –1,830 m) is known locally from a narrower depth range than S. hastigera (793– 2,440 m). The naked test herein reported (EMEPC-LUSO L09D22S1) was collected at shallower depth (718–825 m) than previous records of this species from the archipelago. Regardless, Mironov (2014) concluded that in the Northeast Atlantic S. varispina typically occurs in depths shallower than 2,000 m, whereas S. hastigera usually occurs deeper (> 1,900 m).