Asexual reproduction in starfish

All the individuals were fairly small, with arm lengths not exceeding 18 mm (0.71 in), but no juveniles were found, suggesting that there had been no recent larval recruitment and that this species may be obligately fissiparous.

It is unclear why fission starts in any particular part of the disc rather than any other, but the origin seemed to bear some relation to the position of the madreporites and the longest arm.

[5] In Brazil, only male individuals have been found and fission takes place all the year round, though primarily in the winter.

Fission seems to be correlated with certain stress factors such as particularly low tides, when many starfish may be exposed to the air.

Many larger individuals provide evidence from the varying lengths of their arms that they have divided by fission on several occasions.

In another sample of juvenile Scierasterias heteropau, the arms were similarly arranged in groups of three and there were 4 madreporites, 2 on the original and 2 on the regenerated section.

[1] Writing in 1872, Lutken suggested that in certain members of the Ophiuroidea, "a radiary division occurs in which cast off arms formed new rays and a disk".

[9] In the same year, Monks showed experimentally that the "comets" developing from the severed arms of Linckia columbiae could indeed grow into new individuals.

Most fractures took place about 2.5 cm (1 in) from the disk and started with a small crack appearing on the lower surface of the arm.

The mortality rate of newly severed arms was high, many succumbing to bacterial infection while the wounds were fresh.

This process lasts for some time, and about 10 months after separation, the comet has a half disc and 4 arms about 1 cm (0.4 in) long.