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Asexual reproduction in starfish takes place by fission or through autotomy of arms. In fission, the central disc breaks into two pieces and each portion then regenerates the missing parts. In autotomy, an arm is shed with part of the central disc attached, which continues to live independently as a "comet", eventually growing a new set of arms.
In some species, disk independent bidirectional regeneration is utilized to produce new starfish. Several species also produce larvae that are capable of asexual reproduction prior to adulthood through autotomy and budding. [36] A less commonly used form of asexual reproduction is fissiparity, reproduction via the division of the disk. [37]
The larvae of several species of starfish can reproduce asexually before they reach maturity. [50] They do this by autotomising some parts of their bodies or by budding . [ 51 ] When such a larva senses that food is plentiful, it takes the path of asexual reproduction rather than normal development. [ 52 ]
In certain other asterozoans, adults reproduce asexually until they mature, then reproduce sexually. In most of these species, asexual reproduction is by transverse fission with the disc splitting in two. Both the lost disc area and the missing arms regrow, so an individual may have arms of varying lengths.
Females of species have the ability to reproduce asexually, without sperm from a male. The process is called parthenogenesis, from the Greek words for “virgin” and “birth.”
Above the genetic level, regeneration is fundamentally regulated by asexual cellular processes. [9] Regeneration is different from reproduction. For example, hydra perform regeneration but reproduce by the method of budding. The regenerative process occurs in two multi-step phases: the preparation phase and the redevelopment phase.
Reproduction is also regulated by planktonic food supply. A. stellifera can reproduce asexually by breaking apart into smaller parts and regrowing the missing limb. This explains why Asterina can be found living with less than five arms. Asterian sea stars also reproduce through dispersal of eggs.
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