Astropecten hermatophilus Sladen, 1883

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 : 73-75

Astropecten hermatophilus Sladen, 1883

( Fig. 15 )

Reports for the Azores:

Astropecten hermatophilus $ Sladen, 1883: 257–259, 1889: 207–208 , pl. 33, figs. 5–6, pl. 37, figs. 7–9; $ D̂derlein 1917: 91–92, 172, pl. 3, figs. 8,9, 9a; Mortensen 1927a: 57; $ A.M. Clark & Downey 1992: 36, figs. 11h–j, pl. 8, figs. D, E; Pereira 1997: 335; Micael & Costa 2010: 322; Micael et al. 2012: 5; non Astropecten pentacanthus ( Philippi, 1837) — $ Simroth 1888: 231 [misidentification]; non Astropecten pentacanthus ( Delle Chiaje, 1827) — Ludwig 1897: 39–47, pl. 2, fig. 5, pl. 6, fig. 8: 231 [based on Simroth 1888]; non Astropecten irregularis pentacanthus ( Delle Chiaje, 1827) — Koehler 1914b: 273 [based on Simroth 1888]; Madsen 1950:

169–170 [based on Ludwig 1897].

Type locality: Azores (38°38’00”N, 28°28’30”W).

See: Sladen (1883, 1889); A.M. Clark & Downey (1992).

Occurrence: Northeast Atlantic; known from the Azores ( Sladen 1883), Canaries ( Moreno-Batet & Bacallado 1980) and Gulf of Guinea (A.M. Clark & Downey 1992).

Depth: 10–165(?823) m ( AZO; Sladen 1883, herein).

Habitat: buried in soft substrates, mud or sand, feeding on small infaunal fauna, e.g., bivalve Ervilia castanea ( Montagu, 1803) ( Sladen 1889, Moreno-Batet & Bacallado 1980, herein).

Material examined: DBUA-ECH 056 (Horta harbour, FAY, AZO, c. 38°31’51”N, 28°37’23”W, 2009.12.03, 10 m; 2 dry spms, R = 16–24 mm, r = 5–7 mm); DBUA-ECH 057 [Cerco, Caloura (buried in sand), SMG, AZO, c. 37°42’26”N, 25°30’37”W, 2010.08. 13, 20 m; 1 dry spm; R = 7, r = 3 mm]; DBUA-ECH 059 ( SMG, AZO; 2 spms, R = 20–27 mm, r = 6–8 mm); DBUA-ECH 060 ( SMG, AZO; 2 spms, R = 19–20 mm, r = 7); DBUA-ECH 061 (Vila Franca do Campo, SMG, AZO, c. 37°42’50”N, 25°25’58”W, 3 spms, R = 6–8 mm, r = 3 mm); DBUA-ECH 062 (Água d’Alto, SMG, AZO, c. 37°42’55”N, 25°28’27”W, 1993.07.29; 7 spms, R = 7–10 mm, r = 3–4 mm); DBUA-ECH 098 (Horta, FAY, AZO, c. 38°31’51”N, 28°37’23”W, 2010.6. 25, 15 m; 1 spm, R = 20 mm, r = 7 mm); DBUA-ECH 099 ( SMG, AZO; 1 spm, R = 15 mm, r = 6 mm); DBUA-ECH 101 ( SMG, AZO; 2 spm, R = 20–27 mm, r = 7–9 mm); DBUA-ECH 102 ( SMG, AZO; 1 spm, R = 19 mm, r = 6 mm); DBUA-ECH 116 (Horta harbour, FAY, AZO, c. 38°31’51”N, 28°37’23”W, 2011.07, 20 m; 1 spm, R = 4 mm, r = 2 mm); DBUA-ECH 167 ( SMG, AZO; 3 spms, R = 5–6 mm, r = 2–3 mm).

Description: body pentagonal, flattened dorsoventrally, with five broadly triangular arms. R/ r ratio between 2.2–2.3 in the smaller specimens (R <7 mm) to 3.2–3.4 in the larger (R> 16 mm); paxillar area much broader than the marginal one, densely covered by paxillae, particularly in the area of the epiproctal cone, which is especially prominent in smaller individuals (R <10 mm). Paxillar spinelets with swollen rounded blunt tips giving an overall granulose aspect to the paxillar area; maximum number of paxillar spinelets present variable, from less than six marginal spinelets with no central spinelet in the smaller specimens (R <7 mm) to ten to eleven spinelets surrounding up to six central spinelets in the larger specimens (R = 27 mm); central spinelets shorter and more rounded (blunt) than the marginal ones. Madreporite oval. Superomarginal plates small, narrow, tumid, vertical and granulose with a stubby spine or larger tubercle on some or all plates; occasionally a second spine is also present in one or two of the innermost plates on each side of the median interradial line. Number of superomarginal plates (SM) varies proportionally with size, from about 0,5–0,7 SM/R in smaller specimens (R <6 mm) up to 1,0–1,2 SM/R in larger specimens (R> 19 mm). In smaller specimens (R <10 mm), each inferomarginal plate has a compressed, lanceolate spine followed by a similar spine, which is about two-thirds shorter. Both spines are aligned slightly oblique to the median line of the plate and become progressively slender towards the tip of the arm. In larger specimens, a third spine is generally present, though its maximum size is less than half the size of the adjacent spine and it tends to disappear distally. On the inferomarginal plates towards the tip of the arm, in larger specimens (R> 15 mm), a third spine is sometimes present next to the largest spine, though very short (a third or less the size of the largest spine) and very slender, having thus the appearance of a supplementary spinelet. Three adambulacral furrow spines truncate or rounded. Subambulacral spines in two rows, broadly truncate, larger than furrow spines; on few of the innermost plates of the larger specimens (> 20 mm) one or two supplementary spinelets may be present; no pedicellaria; dorsal paxillar area whitish-yellow to brown with supermaginals and ventral surface white. Shells of the marine bivalve Ervilia castanae were found in the stomachs of the many of the specimens.

Remarks: Astropecten with over 150 described species worldwide ( Zulliger & Lessios 2010) is one of the most difficult shallow-water asteroid genera, encompassing highly polymorphic species with several described subspecies, local varieties and intermediate forms among sympatric species. Thorough the years several authors attempted to revise this genus (e.g., D̂derlein 1917; A.M. Clark & Downey 1992; Zulliger & Lessios 2010) though the matter still remains far from resolved. The history of the echinoderm faunal studies in the Azores is a good example of how difficult this genus is. Of a total of five species of Astropecten reported at one time to the archipelago, two were dismissed as erroneous since they proved to have been based on misidentifications [ A. irregularis pentacanthus ( Delle Chiaje, 1827) ] or on invalid synonymy [ A. bispinosus ( Otto, 1823) ]; another two were considered as dubious due to substantiated concerns on the validity of the identifications or on the provenance of the reported specimens [ A. aranciacus ( Linnaeus, 1758) and A. platyacanthus ( Philippi, 1837) ]. Ultimately, the only astropectinid known with certainty from the Azores is A. hermatophilus . This species was described by Sladen (1883, 1889) based on a specimen collected by H.M.S. Challenger in the Azores (sta 75: 38°38’N, 28°28’30”W, 823 m). In 1888, Simroth included the Mediterranean A. pentacanthus among the species collected by him in the Azores. Later, D̂derlein (1917) re-identified Simroth material as A. hermatophilus . Almost one hundred years later, A. hermatophilus was also reported from the Canaries ( Moreno-Batet & Bacallado 1980) and the Gulf of Guinea (A.M. Clark & Downey 1992). The latter species is only known from small animals; the type specimen as described by Sladen (1889) is one of the largest specimens known (R = 25 mm) (see also D̂derlein 1917, Moreno-Batet & Bacallado 1980, A.M. Clark & Downey 1992). This feature led some authors to question the validity of the species (e.g., A.M. Clark & Downey 1992; Zulliger & Lessios 2010). Regardless, on comparing our largest specimen (R = 27 mm) we could clearly recognize the original description and illustrations by Sladen (1889). As our sample included specimens covering a relatively large size spectrum, it was possible to conclude that deviations from the type were sizedependent (e.g., number of paxillar spinelets, number of inferomarginal fringe spines). Additionally, some of the specimens observed herein had shells of the bivalve Ervilia castanae in their stomachs and in many instances the shells of this little bivalve were almost as big as the sea star disc.

The depth range of Astropecten hermatophilus seems quite remarkable. Sladen (1883, 1889) described this species on the basis of an animal collected by H.M.S. Challenger, between Faial and S„o Jorge islands at a reported depth of 823 m (450 ftms). Interestingly, at the same station he identified as well Ophidiaster ophidianus ( Lamarck, 1816) and Hacelia attenuata Gray, 1840 (= Ophidiaster attenuatus ), both strictly littoral species. Sladen also reported Chaetaster longipes ( Bruzelius, 1805) for the same station; though not littoral this species tends to occur at much shallower waters than 820 m. At first instance, it seems that the depth data presented for station 75 should be much shallower than the one presented by Sladen. In contrast, Agassiz (1881) working with the H.M.S. Challenger echinoids indicated two sets of depth values of 92–165 m (50–90 ftms) and 823 m (450 ftms) for station 75, though the species identified by the author among the material from station 75 have a wider known bathymetrical range than the species mentioned above (e.g., Genocidaris maculata Agassiz, 1869 ). Thus, the echinoderms altogether found at this station indicate problems relating to the depth data, and Agassiz’s (1881) shallower depth values appear more realistic. One has to keep in mind that HMS Challenger dredged three times at station 75, which is in an area of high bottom relief and thus delivered material from different depths (namely 50, 90, and 450 fathoms according to the ship log ( Thomson & Murray 1885). Apparently, all the material resulting from these three dredges was attributed to station 75, thus causing the confusion mentioned above.

Figures

FIGURE 15. Astropecten hermatophilus Sladen, 1883 (DBUA-ECH 059). Dorsal view (A); ventral view (B); detail of the arm dorsal view (C); detail of the oral area and arm (D).