Coscinasterias tenuispina ( Lamarck, 1816 )

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 : 64-66

Coscinasterias tenuispina ( Lamarck, 1816)

( Fig. 12 )

Reports for the Azores:

Asterias tenuispina Lamarck, 1816 — $ Barrois 1888: 70; $ Koehler 1909: 122; Koehler 1914b: 275; Mortensen 1921: 224;

Coscinasterias tenuispina ( Lamarck, 1816) — Koehler 1921b: 26, fig. 19; $ Nobre 1924: 88; Mortensen 1927a: 138; $ Nobre 1930: 68, 1938: 36–37, figs. 10, 11; $ Marques 1983: 2; A.M. Clark & Downey 1992: 427–428, figs. 63h, i, pl. 101, figs. A, B; Pereira 1997: 335; $ Morton et al. 1998: 120, 169, figs. 6.2O, 8.8S; Pérez-Ruzafa et al. 2002: 280–281; Micael & Costa 2010: 321; Micael et al. 2012: 2, 3–4.

See: Verrill (1915: 19–20, pl. 26, figs. 2, pl. 17, fig. 4); A.M. Clark & Downey (1992).

Occurrence: on tropical-subtropical waters of the Mediterranean Sea and Atlantic Ocean; in the west, from North Carolina south to Brazil (A.M. Clark & Downey (1992) including Bermuda (H.L. Clark 1933), and in the east from the Bay of Biscay ( Koehler 1921b) to Sierra Leone ( Nataf & Cherbonnier 1975), including the Azores ( Koehler 1909), Madeira ( Augier 1985), Selvagens ( Pérez-Ruzafa et al. 2002), Canaries ( Bacallado et al. 1985), Cape Verde ( Pérez-Ruzafa et al. 1999) and Saint Helena ( Mortensen 1933c).

Depth: 0–165 m (A.M. Clark & Downey (1992); AZO: 0–12 m (herein).

Habitat: typical inhabitant of rocky shores; also found on biogenic detritus, sandy to silty sand substrates, under stones and in the meadows of Zostera and Posidonia ( Koukouras et al. 2007) .

Larval stage: probably planktotrophic (inferred from the genus); also reproduces asexually through fission ( Waters & Roy 2003).

Material examined: DBUA-ECH 077 (FRM, AZO, c. 37°16’14”N, 24°46’52”W, 1990.06; 6 spms, R = 32–68 mm, r = 4–7 mm); DBUA-ECH 108 (FRM, AZO, c. 37°16’14”N, 24°46’52”W, 1990.06; 3 spms, R = 30–110 mm, r = 3–10 mm); DBUA-ECH 114 (Lajes, PIX, AZO, c. 38°23’22”N, 28°15’04”W, 2 m; 4 spms, R = 7–25 mm, r = 1–3 mm); DBUA-ECH 122 (S„o Roque, SMG, AZO, c. 37°44’37”N, 25°38’19”W, 2012.11.16, intertidal; 1 spm, R = 3 mm, r = 1 mm); DBUA-ECH 184 (Poços, Capelas, SMG, AZO, c. 37°50’06”N, 25°40’10”W, 1996.07. 18, 12 m; 1 spm, R = 3 mm, r = 1 mm); DBUA-ECH 407 ( Marina, Vila do Porto, SMA, AZO, 36°56’42”N, 25°08’50”W, 2016.07. 5, 1 m; 1 spm, R = 76 mm, r = 8 mm).

Description: disc small, with six to nine arms, rather long and slender, slightly angular and of unequal size, being larger of one side relative to the other. Most specimens with two to three madreporites; exceptionally three specimens exhibited a single madreporite, but also signs of recent self-division (shape of the disc half circumference; smallest arms less than a quarter the size of the remaining arms) (DBUA-ECH 077c, 114c, 184). Abactinal skeleton strong, with three regular longitudinal series of primary plates, each carrying a single aciculate spine encircled by a large wreath of crossed pedicellaria; only one dorsal (carinate) series in the smaller specimens (R <7 mm). Spines in the disc irregularly distributed not forming a pentagon. Superomarginal plates with an irregular patch of fine crystal bodies; alternating plates bear single aciculate spines encircled by large wreath of crossed pedicellaria. Inferomarginals bear two oblique spines somewhat flattened, with similar sizes as superomarginals; marginal spine with crossed pedicellaria surrounding only the outer side; larger specimens (R> 40 mm) occasionally presented a third (interactinal) spine in the proximal area between the inferomarginal and the adambulacral plates, about the same size and shape as the nearest inferomarginal; the presence or position along the arms of this additional spine was not constant between specimens or between arms of the same specimen. Adambulacral plates generally bearing one long flattened spine with no attached pedicellaria (monocanthid); in larger specimens (R> 7 mm), a second spine was occasionally present, though its presence was irregular, normally restricted to the proximal area of the arms; in the largest specimen (DBUA-ECH 108; R = 110 mm) this additional spine was observed to about two thirds from the arm base. Crossed pedicellaria with enlarged terminal teeth larger than the median terminal teeth; lanceolate straight pedicellaria long and scattered throughout surface, particularly numerous between the arms. Colour (alive): dorsal side brown or purplish-blue with darker and lighter specks; crossed pedicellaria and tube feet bright orange; ventrally cream; colour (in ethanol) from uniform whitish to cream. Shells of the marine gastropod Anachis avaroides Nordsieck, 1975 were found in the stomach of the specimen DBUA-ECH 407.

Remarks: among species belonging to the genus Coscinasterias , C. tenuispina closely resembles C. calamaria a species known from South African and Australian waters. These two species differ only by the shape of the pedicellaria, as in C. tenuispina the crossed pedicellaria present an enlarged tooth and the straight pedicellaria present short stubs at the tips. A.M. Clark & Downey (1992) remarked that the separation between the two species should eventually be downgraded to a subspecific level, as C. tenuispina from Brazil seemed to present somewhat intermediary characteristics. More recently, Waters & Roy (2003) conducted a phylogenetic analysis on the genus, and their findings contradicted the previous authors’ hypothesis and pointed to a closer relationship between C. calamaria and C. acutispina , a north Pacific species. On the other hand, Waters & Roy support a subspecific separation of C. tenuispina populations from the Brazil. Nevertheless, these authors cautioned that further studies should be conducted on Brazilian animals since the differences observed by A.M. Clark & Downey were based on juvenile specimens, thus inconclusive from a morphological point of view. In a study on the asteroids from northeastern Brazil, Gondim et al. (2014) appear to support the Waters & Roy’s contention as their own observations fail to support any clear morphological separation. The colour pattern was also present by A.M. Clark & Downey (1992) as a possible source of variation among populations through the geographic range of C. tenuispina . However, the colour in this species is rapidly shed through the preservation process. Specimens housed in the DBUA-ECH collection presented features typical of C. tenuispina , on the appearance of both straight and crossed pedicellaria. Even the appearance of a second adambulacral in a species or genus otherwise known to be monocanthid was already documented by Verrill (1914) as merely individual variations. The observed brown colour pattern was also found in other areas in the Atlantic (e.g., Pérez-Ruzafa et al. 2002; Wirtz & Debelius 2003; Hernández et al. 2013). The blue colour morph observed in one of the specimens ( Fig. 12D ) appears to be also found in Bermuda, NW Atlantic (H.L. Clark 1933).

C. tenuispina can be easily distinguished from the fissiparous Sclerasterias richardi by the distribution of crossed pedicellaria, as in the latter species these pedicellaria are found dispersed on the aboral surface and not organized in wreaths around the spines as in the former. Also, the non-fissiparous sea star Marthasterias glacialis another common inhabitant of the Azorean shallow waters can be easily distinguished from C. tenuispina by having five arms and never more than one madreporite.

Figures

FIGURE 12. Coscinasterias tenuispina (Lamarck, 1816) (DBUA-ECH 357: A–C; DBUA-ECH 407: D). Dorsal view (A); ventral view (B); detail of the arm, ventral view (C); blue colour morph (D).