SIZE DIFFERENCES BETWEEN SEXES (INCLUDING MASCULINIZED FEMALES) IN STROMBUS-PUGILIS (MESOGASTROPODA, STROMBIDAE)

The discovery of masculinized female Strombus pugilis provided a third morph which allowed sexual dimorphism in size to be studied in more d etail. Masculinized females were found to be larger in overall size th an normal females which were in tum larger than males. The difference in size among morphs was not due to differences in shape but only to g rowth to a larger average size. Lip thickness did not differ among the morphs indicating that masculinized females grow to a larger size tha n normal females which grow larger than males in the same amount of ti me. The apparent cause is a genetically-based sex determination system , operating in this species.