. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EXPERIMENTS ON THE DETERMINATION AND DIFFERENTIA- TION OF SEX IN THE BOPYRID STEGOPHRYXUS HYPTIUS THOMPSON 1 EDWARD G. REINHARD The Catholic University of America, Washington, D. C., and the Marine Biological Laboratory, Woods Hole, Mass. One of the great controversies related to the Bopyridae (a family of isopod crustaceans, suborder Epicaridea), and one that has broader biological implications as well, is the question of sex-determination. Is sex already determined in the larval stage, or does the fate of the larva ( w
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EXPERIMENTS ON THE DETERMINATION AND DIFFERENTIA- TION OF SEX IN THE BOPYRID STEGOPHRYXUS HYPTIUS THOMPSON 1 EDWARD G. REINHARD The Catholic University of America, Washington, D. C., and the Marine Biological Laboratory, Woods Hole, Mass. One of the great controversies related to the Bopyridae (a family of isopod crustaceans, suborder Epicaridea), and one that has broader biological implications as well, is the question of sex-determination. Is sex already determined in the larval stage, or does the fate of the larva ( whether it turns into a female or a male) depend on environmental influences? Can such external factors as the position the larva occupies or the nourishment it receives bring about sex reversal in an already sex-determined larva ? The chief views expressed in the past regarding this question are as follows: 1. Giard and Bonnier (1887) maintained that in the Bopyridae all free-swim- ming larvae are males. The first larva, however, that invades a particular host undergoes sex reversal and transforms into a large female without ever having func- tioned as a male. The next to come settles on this female and metamorphoses into an adult dwarf male which fertilizes the former. 2. Smith (1909) and Goldschmidt (1920) stated that all the species of Epi- caridea, Bopyrina as well as Cryptoniscina, are protandric hermaphrodites, each in- dividual being male while in a larval state, and then losing its male organization and becoming female as the parasitic habit is assumed. The females, therefore, result from males that have already functioned as males. 3. Hiraiwa (1936) believed that the free-swimming larvae are not males but are sexually undifferentiated, although the sex is already predetermined. Differ- entiation follows fixation, but is probably not due to environmental factors. 4. Recently, Caullery (1941), impressed by the influence of association on sexu- ality as exhibited in such
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