Astropecten polyacanthus subsp. phragmorus

Astropecten polyacanthus phragmorus (Fisher, 1913): 604 [as Astropecten acanthifer phragmorus] Material examined: 10 specimens (material now lost) Largest sampled specimen in this study: R: 58mm, r: 13mm. Description: (Figs. 18–21) Five long arms, quadrangular in cross section, with a relatively small disc (R /r:>4:1). Actinal and abactinal surface flattened; Abactinal paxillae large towards centre of disc and along mid-radial axis of arms with up to 17 granules. Peripheral paxillae much smaller along arm and disc margins, with only up to 6 granules; madreporite clearly visible; body margin defined by supero-marginal plates which all contain a sharp vertical spine on the abactinal surface including the second and third most proximal plates unlike in A. polyacanthus polyacanthus; each infero-marginal plate wih a single, long, sharp primary spine surrounded by numerous spinelets and with up to 5 smaller secondary spines below the primary spine; terminal disc in tube feet absent, feet instead tapering to distinctive point; colour in live specimens usually creamy to yellow or grayish with prominent dark spots on the disc and along arms, more or less symmetrical across the arm axis. Taxonomic notes: The two subspecies of Astropecten polyacanthus in the Persian Gulf [A. polyacanthus polyacnthus and A. polyacanthus phragmorus] occur in the same substrates and are highly morphologically similar. Mortensen (1940: 61) noted specimens of A. polyacanthus and A. phragmorus in the Persian Gulf that appeared to intergrade between what were then two distinct species (Döderlein (1917: 178) having raised the latter species to specific rank). Clark (1974: 433) agreed with this assessment, having also worked on Persian Gulf material and reduced A. phragmorus to the status of a subspecies of A. polyacanthus. It has been treated as such by all subsequent authorities. The only consistent difference between the two subspecies observed in this study is the presence of a spine on all proximal supero-marginal plates in A. polycanthus phragmorus and its absence from the second more proximal supero-marginal plate in A. polyacanthus polyacanthus. Fewer observations were made of A. polycanthus phragmorus than A. polyacanthus polyacanthus, and this subspecies has been far less commonly reported in the literature. However, we recorded both subspecies at several localities and it is possible that A. polycanthus phragmorus is more widely distributed in the Persian Gulf than currently recognised. The high similarity, and potential for integradation, between subspecies may have led to misidentification of some specimens as A. polyacanthus polyacanthus in earlier studies. Observations: Sandy and sandy/rocky intertidal to 2 m; Recorded in the present study at Nayband Bay, Bostaneh, and also at Hormuz, Hengam, Qeshm and Lavan Islands. Previously reported from the Persian Gulf: (Mortensen 1940; Clark & Rowe 1971; Clark 1974; Price 1983; Pourvali 2015; Adeli et al 2022); present study.