THE GENETICS OF ARTEMIA SALINA. I. THE REPRODUCTIVE CYCLE

¹ Department of Biology, San Francisco State College, San Francisco 27, California

1. This paper reports the first analysis of an inherited trait governed by one locus in the brine shrimp, Artemia salina. The autosomal gene, r, for red eyes arose spontaneously in a Utah race. It is recessive to the wild type allele, R, for black eyes. It has complete penetrance in rr shrimp.

2. The standard culture method outlined here has successfully carried the mutant stock through ten generations in a one-year period.

3. Reproduction was studied in two races from California and Utah. Neither paedogenesis nor parthenogenesis was observed in these shrimp which were raised by the standard culture method. This observation conflicts with the reports of Jensen and of Relyea that the Utah race could reproduce parthenogenetically.

4. Matings of RR males to rr females produce only black-eyed progeny. This indicates that when raised by the standard method the Utah shrimp do not normally reproduce by pseudogamy.

5. Studies of the sequence of steps in the female reproductive cycle confirm the observations of Lochhead. Genetic experiments have demonstrated that although the adults may clasp continuously throughout the cycle, copulation is effective only when the eggs are in the oviducts.

6. Females do not store sperm from one reproductive cycle to the next. If an rr female is alternately mated in different cycles to males of RR and rr genotype, all the nauplii in one brood have the same genotype.