EVIDENCE FOR THE EXISTENCE OF HOMOZYGOUS CLONES IN THE SELF-FERTILIZING HERMAPHRODITIC TELEOST RIVULUS MARMORATUS (POEY)

¹ Genetics Laboratory, New York Aquarium, New York Zoological Society, American Museum of Natural History, New York 24, N. Y.
² Entomological Research Center, Florida State Board of Health, Vero Beach, Florida

1. Since self-fertilization constitutes the ultimate basis of inbreeding, a species or race of self-fertilizing hermaphrodites should consist of clones, all members of which possess identical genotypes and are homozygous. This prediction has been tested on a recently discovered population of Rivulus marmoratus from the east coast of Florida. All wild-caught specimens of this population tested so far have proved to be hermaphrodites. Those kept in isolation in aquaria, and their her maphrodite descendants kept in isolation ab ovo, have reproduced by self-fertilization.

2. The transplantation test has been used to determine whether fish that had descended from the same wild-caught progenitor possess identical genotypes. Fins spleens and hearts were transplanted in 36 different host-donor combinations involving six different lines (sib to sib, parent to offspring, offspring to parent). Only two transplants failed to survive, but their loss may have been due to mechanical reasons. These results are in accordance with the theoretical prediction that these fish are largely homozygous.

3. Transplants were performed in seven different inter-line combinations. Of these only a single graft survived, indicating that the fish collected on different days in different places belonged to the same clone.