Ophidiaster granifer
The only starfish known to reproduce exclusively by parthenogenesis.
The grained seastar (*Ophidiaster granifer*) is a starfish belonging to the family Ophidiasteridae. It lives in the Red Sea and the Indo-Pacific, and is the only starfish known to reproduce solely through parthenogenesis.
This small starfish has five arms, a mottled brown pattern that helps it blend in, and a rough, granular texture. It reaches about 10 cm (4 in) across, with a small central disc and medium-length, fairly broad arms that end in rounded tips.
No male of this species has ever been found; all known adults are female. During a synchronized spawning event, eggs are released into the sea without being fertilized. The mother attaches some of these large eggs (0.6 mm in diameter) to the underside of boulders, where they develop until they become juvenile starfish. Other eggs drift as plankton with the currents. In both cases, the larvae are lecithotrophic, feeding on the yolk of their own egg. This reproductive method may be linked to the starfish’s low number of offspring and its sparse population density.
The grained seastar inhabits shallow coral reefs in the Red Sea and Indo-Pacific, including the South China Sea, Japan, Tonga, Fiji, Samoa, northern and western Australia, the Great Barrier Reef, New Guinea, Indonesia, the East Indies, and the Philippines. It typically hides under boulders and is found on outer reef flats, patch reefs in lagoons, among broken coral rubble, and in the dead bases of tangled coral thickets.
Quick Facts
- Genus
- Ophidiaster
- Species
- granifer
Facts from the source article.
Lore & Background
Ophidiaster granifer is a small five-armed starfish with a cryptic mottled brown colouration and a rough, granular appearance. It grows to a diameter of about 10 cm (4 in), with a small disc and medium-length, fairly broad arms with rounded tips. No male has ever been identified, and all known adults are female. As far as is known, it is the only member of the phylum Echinodermata to reproduce exclusively by parthenogenesis. Eggs are liberated into the sea in a synchronous spawning event without fertilization. The eggs are large, 0.6 mm in diameter, and the mother attaches some to the underside of boulders, where they develop until metamorphosis into juvenile starfish. Other eggs are planktonic and drift with currents. In both cases, larvae are lecithotrophic, feeding off the yolks of their eggs. This reproductive strategy may be linked to the starfish's low fecundity rate and low population density.
Reader's Guide
Ophidiaster granifer holds a unique place in echinoderm biology as the only known starfish to reproduce exclusively by parthenogenesis. The absence of any identified male individuals and the reliance on unfertilized eggs for reproduction distinguish it from all other starfish species. Its reproductive strategy involves synchronous spawning, with eggs either attached to boulders or drifting planktonically, and larvae that feed on yolk reserves. This approach may be an adaptation to its low fecundity and low population density. The species is found across a wide Indo-Pacific range, from the Red Sea to Japan, Australia, and Pacific islands, typically hiding under boulders on coral reefs. Its cryptic mottled brown coloration and granular texture aid in camouflage. The article notes that no other echinoderm is known to reproduce exclusively by parthenogenesis, making Ophidiaster granifer a subject of particular interest for studies of asexual reproduction in marine invertebrates.
Did You Know?
- No male Ophidiaster granifer has ever been identified; all known adults are female.
- Some eggs are attached to the underside of boulders, while others are planktonic.
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