Thromidia catalai
One of the largest and heaviest starfishes in the world.
Thromidia catalai, commonly known as the heavy starfish, belongs to the family Mithrodiidae within the order Valvatida. This Indo-Pacific species ranks among the world's largest and heaviest starfish, with documented weights reaching 6 kg (13 lb) and diameters of 60 to 65 cm (24 to 26 in). Australian biologists E. C. Pope and F. W. E. Rowe first described it in 1977, based on specimens from New Caledonia.
This starfish has five arms and can reach a diameter of up to 70 cm (28 in). Its surface is covered in low tubercles, creating a granular texture. The arms are thick and cylindrical, with little taper and rounded ends. The central disc is small, and both the disc and arms are pinkish-beige, except for the arm tips, which are dark orange-brown. Unlike other Thromidia species, the arm tips bear small, widely spaced tubercles. The only similar species is Thromidia gigas, which has paler arm tips and is restricted to the southern Indian Ocean near Madagascar, Réunion, and South Africa.
Thromidia catalai lives throughout the tropical Indo-Pacific, from Indonesia to Hawaii and from southern Japan to New Caledonia and northern Australia. It typically inhabits areas within and between reefs where detritus accumulates, at depths of 15 to 130 m (50 to 430 ft), though it is usually found deeper than 30 m (100 ft) on the continental shelf. Its rarity in sightings likely reflects its deep habitat rather than actual scarcity.
Little is known about its feeding, but related species are carnivorous, preying mainly on molluscs and echinoderms. Like other starfish, it everts its stomach over prey, secreting enzymes to digest it externally. The sexes are separate, and fertilization occurs externally after eggs and sperm are released into the water.
Quick Facts
- Genus
- Thromidia
- Species
- catalai
Facts from the source article.
Lore & Background
Thromidia catalai was first described by the Australian biologists E. C. Pope and F. W. E. Rowe in 1977, with the type locality being New Caledonia. It is a large starfish with five arms and a diameter of up to 70 cm (28 in), weighing up to 6 kg (13 lb). The surface is covered with low tubercles, giving it a granular appearance. The arms are robust and cylindrical, not tapering much and having rounded tips. The disc is small, and both disc and arms are a pinkish-beige colour, apart from the tips of the arms, which are a dark orange-brown. In contrast to other members of the genus Thromidia, the tips of the arms have small, widely spaced tubercles. The only other starfish with which this species could be confused is the closely related Thromidia gigas, but that species, though a similar size, has paler arm tips and is only found in the southern Indian Ocean, around Madagascar, Réunion and South Africa.
Reader's Guide
Thromidia catalai is notable as one of the largest and heaviest starfishes in the world, with a reported weight of up to 6 kg and a diameter of 60 to 65 cm. Its distribution spans the tropical Indo-Pacific, from Indonesia to Hawaii and from southern Japan to New Caledonia and northern Australia. It is found typically in and between reefs where detritus settles, at depths between about 15 and 130 m, but usually deeper than 30 m on the continental shelf. Although seldom encountered, this may be because of the considerable depth at which it lives rather than its rarity. Little is known of its feeding habits, but related species are carnivorous, mainly eating molluscs and echinoderms, and it everts its stomach to digest prey. As with other starfishes, the sexes are separate and fertilization occurs in the water column. Its first description in 1977 by Pope and Rowe established it as a distinct species within the genus Thromidia, differentiated from Thromidia gigas by darker arm tips and a different geographic range.
Did You Know?
- Thromidia catalai is sometimes called the heavy starfish.
- It can weigh as much as 6 kg (13 lb) and have a diameter of 60 to 65 cm (24 to 26 in).
- Its arm tips are a dark orange-brown, unlike the paler tips of the related Thromidia gigas.
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