Asterias rubens? Linnaeus, 1758

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 : 63-64

Asterias rubens? Linnaeus, 1758

Reports for the Azores:

non Asterias polaris , Gray— $ Perrier 1896a: 38 [juveniles of A. rubens ]; non Leptasterias polaris ( M̹ller & Troschel, 1842)— Pereira 1997: 336 [based on Perrier 1896a]; Micael & Costa 2010: 321 [based on Perrier 1896a]; non Ctenodiscus crispatus ( Bruzelius, 1805) — García-Diez et al. 2005: 47 [inaccurate synonymy]; Micael & Costa 2010: 322 [inaccurate synonymy]; Micael et al. 2012: 5 [inaccurate synonymy]; Asterias rubens Linnaeus, 1758 — $ Koehler 1924: 10.

See: A.M. Clark & Downey (1992: 422–423, fig. 67c, pl. 100, figs. C–D).

Occurrence: North Atlantic, in the west from Labrador south to Carolinas (occasionally also Florida); and in the east White Sea and Iceland south to southern Portugal ( Mortensen 1927a, A.M. Clark & Downey 1992) and? Azores ( Koehler 1924).

Depth: 0–900 m (A.M. Clark & Downey 1992);? AZO: intertidal ( Perrier 1896a).

Habitat: all sorts of substrates ( Wirtz & Debelius 2003).

Larval stage: planktotrophic ( McEdwards & Miner 2001).

Remarks: Perrier (1896a) reported a species ‘ Asterias polaris Gray’ (family Asteriidae , order Forcipulata) from the Azorean rocky intertidal (Hirondelle, sta 104, Bay of Porto Pim, Horta, Faial Island). The name as this author listed it is not present in Gray (1840, 1866). Fisher’s review (1923, 1930) listed Asterias polaris under the synonymy of two (very different) Arctic species: the paxillosid Ctenodiscus crispatus ( Bruzelius, 1805) (= Asterias polaris Sabine, 1824 ) and the forcipulatid Leptasterias polaris ( M̹ller & Troschel, 1842) (= Asteracanthion polaris M̹ller & Troschel, 1842) (see also A.M. Clark & Downey 1992). In Azorean faunal lists one or both of these species are mentioned, however, none of the authors explained their choice, nor commented on the unusual presence of an Arctic species in the Azores. García-Diez et al. (2005) and Micael et al. (2012) selected the first species, Ctenodiscus crispatus . Pereira (1997) chose the latter species, Leptasterias polaris and Micael & Costa (2010) listed both. Notwithstanding, Perrier (1875) acknowledged Sabine’s Asterias polaris as a junior synonym of Ctenodiscus corniculatus (= ‘ Astropecten polaris Gray’) now accepted as C. crispatus . In contrast, Perrier (1896a) grouped the Azorean A. polaris together with A. rubens (the genus’ type species), as both members of the order Forcipulatida . Previously, Norman (1965) had disagreed with the replacement of the Linnaean genus Asterias by M̹ller & Troschel (1840b) not realising that with the suppression of Asteracanthion , two species would arise with the same name. The problematic taxonomical position of M̹ller & Troschel (1840b) species’ was only resolved much later by Fisher (1923, 1930). Thus, it is apparent that Perrier was referring to L. polaris as described by M̹ller & Troschel (1842). Regardless, Koehler (1924: 102–103) stated in a small footnote that the two small specimens identified by Perrier (1896a) as L. polaris were in reality six-armed individuals of A. rubens . In contrast with arctic L. polaris , the geographical range of A. rubens extends to the southern latitudes of South Carolina (or Florida) and Portugal (A.M. Clark & Downey 1992), making it a more likely inhabitant of the Azores warmer waters. The unusual number of arms observed in the material from the Azores could be the reason for Perrier’s misidentification. Unlike the six-armed L. polaris , A. rubens is characterized by having typically five arms. Occasionally, abnormal animals may have as many as eight arms ( Koehler 1924, Mortensen 1927a).

The material of A. rubens was collected in the rocky intertidal waters of Porto Pim Bay (c. 38°31'29"N, 28°37'38"W). The only other sea star species collected at this Hirondelle station was Marthasterias glacialis , making other common inhabitants of Azores conspicuously absent. Among these, Coscinasterias tenuispina ( Lamarck, 1816) and Luidia ciliaris ( Philippi, 1837) are the only non-pentamerous species. In view of this, it is possible that both Perrier and Koehler may have misidentified Hirondelle specimens with juveniles of the closely related C. tenuispina (see text below). However, this seems unlikely as Koehler was familiarized with these species. Nonetheless, Porto Pim Bay is located in Horta city, near the old installations of Department of Oceanography and Fisheries. This area of easy access is one of the most survey waters in the Azores. However, no new material belonging to A. rubens has ever been collected since Hirondelle cruise. These two small specimens of A. rubens may represent the arrival of this species in the Azores, but for some reason failed to settle in the archipelago. For the above reasons, we have considered the presence of this species in the archipelago shallow waters as doubtful.