Is hogfish Lachnolaimus maximus (Labridae) a diandric species?
Hogfish Lachnolaimus maximus (Walbaum, 1792) is the largest labrid in the Atlantic and a commercially important fish. In previous research, this fish has been defined as a monandric protogynous hermaphrodite, although characterization of hermaphroditism is particularly challenging in labrids. Examination of testicle structure is not always a wholly trustworthy method for distinguishing between diandric species (those with primary and secondary males) and monandric species (only secondary males). In some diandric species, morphological differences in the testes do not occur between primary and secondary males despite functional diandry. The presence of individuals with inactive bisexual gonads and/or of inactive males smaller than the minimum size of sexual maturation is a more dependable criterion for identifying diandry. A histological analysis of the gonads of 1,975 L. maximus specimens (10.3-47.4 cm fork length, FL) from the southern Gulf of Mexico was done. Some individuals were identified that were larger than the size at first maturity (N = 20; 24.8-33.5 cm FL) and had ovotestes atypical of a monandric species. These ovotestes had an internal morphology like ovaries, consisting mostly of inactive ovary tissue in lamellar structure, as well as limited development of active testicular tissue in crypts inside the gonad wall and/or in lobules beneath the gonad wall. Considered to be “bisexual” gonads, their origin and function were evaluated based on published data. Lachnolaimus maximus could be defined as a diandric species if males can differentiate indirectly by sexual inversion of functional females (postmaturational secondary males) or by direct development from the “bisexual” stage (prematurational secondary males). However, no inactive bisexual individuals or inactive males smaller than the size at first maturity were observed. In addition, population structure and overall sex ratio were typical of a monandric protogynous species. The possibility that L. maximus could exhibit diandric hermaphroditism therefore remains hypothetical.