The Starfish of Hong Kong, Part 5

Pentaceraster chinensis (no English common name)

Pentaceraster regulus – a relative of P. chinensis. Image by Bernard Dupont cc-by-4.0

A tropical starfish know from several locations including Hainan.

Luzon Sea Star (Echinaster luzonicus)

Echinaster luzonicus from Pulau Tioman (Malaysia)
Author Ron Yeo, cc-by-nc-sa.

The Luzon sea star is prone to shed its arms, which then regenerate into new individuals. It is normally six-armed but often quite asymmetrical in appearance, because of it has a habit of shedding arms. Its colouring ranges from red to dark brown. It is found in the tropical and sub-tropical western Indo-Pacific region, ranging from Madagascar and the east coast of Africa to Northern Australia, Indonesia and the Philippines. It is found on both reef crests and in the intertidal zone where it feeds on bacterial and algal films that it extracts from the sediment. By shedding its arms for regeneration the species can reproduce asexually. The shed arm regenerates, growing a new disc and further arms.  Up to 65 cm in diameter.

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The Starfish of Hong Kong, Part 1

Crown-of-Thornes (Acanthaster planci)

Crown-of-Thornes starfish

The crown-of-thorns starfish is a large starfish with many arms that preys on hard coral. Its name comes from the venomous thorny spines covering its upper surface – meant to resemble the crown of thorns put on Jesus before his crucifiction. This is one of the largest starfish and has a very wide distribution in the Indian and Pacific Oceans at tropical and subtropical latitudes where coral reefs or hard coral communities occur.

The venom of the starfish contains so-called asterosaponins which have detergent-like properties. The brittle spines can perforate the skin of a predator or unwary diver and tissue containing the venom is lodged into the resulting wound. In humans this immediately causes a sharp, stinging pain lasting several hours, with persistent bleeding aided the venom as well as nausea, tissue swelling lasting for a week or more. Breaking of the spines means they become embedded in the tissue where they require surgically removal.

Peppermint Sea Star (Fromia monilis)

The peppermint sea star can grow to a diameter of about 30 centimetres. Its arm tips and the central disc are bright red, while the other parts are paler, forming large plates. The color, plates and other features can be very variable and identification from photographs can be difficult. It feeds on encrusting spongess, detritus and small invertebrates. Occurs in shallow water in rocky environment, at a depth of 0 – 51 m.