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Two Species of Lytechinus (Toxopneustidae: Echinoidea: Echinodermata) Are Completely Cross-fertile

Cameron, R. Andrew (1984) Two Species of Lytechinus (Toxopneustidae: Echinoidea: Echinodermata) Are Completely Cross-fertile. Bulletin of the Southern California Academy of Sciences, 83 (3). pp. 154-157. ISSN 0038-3872.

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The sympatric sea urchins, Lytechinus anamesus Clark 1912 and L. pictus (Verrill, 1867) are found in different microhabitats. L. anamesus primarily resides in open coast areas, while L. pictus is found in bays and lagoons (Ricketts and Calvin 1968; T. A. Ebert, S. Schroeter and others, pers comm.). Although Mortensen (1943) considered the two forms to be valid species, Mayr (1954) omitted L. pictus from his zoogeographical discussion of the genus because he thought it was possibly a synonym of L. anamesus. A key to the species of the genus distinguishes between the two forms on the morphology of the spicules found in the stalk of the globiferous pedicellariae (Chesher 1968). Word and Charwat (1975) separate the two species in their key on the basis of spine morphology and color. Furthermore, the two forms are readily cross-fertilizable and embryonic cells will reaggregate to produce viable early embryos (Vacquier, quoted in Durham et al. 1980). The observations above could be accounted for by one of at least two hypotheses. The two forms could be ecotypic variants within a single species or truly isolated populations between which no genetic exchange occurs. In order to exclude the isolation hypothesis, it must be shown that: (1) the hybrids can successfully develop and survive to the adult form and (2) exchange of gametes or larvae can occur in nature. The tests for development and survival can be easily accomplished since techniques for larval rearing are readily available (Hinegardner 1969; Cameron and Hinegardner 1974).

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Cameron, R. Andrew0000-0003-3947-6041
Additional Information:© 1984 Southern California Academy of Sciences. Accepted for publication 20 June 1982.
Issue or Number:3
Record Number:CaltechAUTHORS:20121030-150356518
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35187
Deposited By: Aucoeur Ngo
Deposited On:30 Oct 2012 23:08
Last Modified:03 Oct 2019 04:26

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