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Abstract: In Rarotonga, Linckia multifora (Lamarck) exists in two forms: a blue gray type that is found on the reef intertidally and a red form that is found subtidally. Both types reproduce asexually by regeneration of autotomized arms, as well as sexually, but the relative potential for sexual reproduction varies greatly between these different sites. In the laboratory, reciprocal crosses of the blue gray intertidal form and the red subtidal form developed as successfully as the controls and were indistinguishable in morphology. In addition, both the blue gray intertidal form and the red subtidal form contain two different classes of haplotypes of the mitochondrial gene cytochrome oxidase subunit I (COI), which exhibit 12 fixed differences. These results suggest that L. multifora of Rarotonga has a dual origin and that the two different forms seen in the two environments belong to a single interbreeding population and may represent ecophenotypes.
LINCKIA MULTIFORA (LAMARCK) is a small sea star, a member of the Ophidiasteridae, that is found on coral reefs throughout the Indo-Pacific Ocean (Clark and Rowe 1971). It generally has arms of uneven lengths because it reproduces asexually by autotomizing arms, which can then regenerate into whole starfish (Edmondson 1935). It is identified by the arrangement of spines along the ambulacral grooves, the presence of two madreporites, the arrangement of papular openings, the granularity of the epidermis, and the general shape of the arms (Clark and Rowe 1971).
On the island of Rarotonga, Cook Islands, South Pacific, there appear to be two different types of L. multifora: a red-spotted form that is found in the subtidal zone and a gray blue form that is found on the top of the reef in the intertidal zone. To confirm that these are both L. multifora and to explore the relationship between them we have sequenced a mitochondria gene, cytochrome oxidase subunit I (COI).
To understand aspects of the ecology and evolutionary biology of an organism, it is important to understand its mechanism(s) of reproduction (Hart 2002). Linckia multifora is generally considered to reproduce primarily by asexual means (Rideout 1978), and it has been referred to in the literature as an asexual organism (Ebert 1996). However, it produces eggs and sperm (Mortensen 1938, Rideout 1978), and viable cultures of...