Characterizing reproductive development in female white shrimp Penaeus setiferus (Decapoda: Dendrobranchiata: Penaeidae) in South Carolina, USA

ABSTRACT Accurate assessments of female reproductive development are an important component to the sustainable management of the fishery of the white shrimp Penaeus setiferus (Linnaeus, 1767) in the southeastern U.S. Reproductive development has been commonly assessed macroscopically based on ovarian color; however, distinguishing females that have never spawned from those that have previously spawned using this approach can be challenging due to their similarity in appearance. Histological approaches allow for higher resolution in quantifying microscopic phases of reproductive development and may reveal evidence of prior spawning events. Our objective was to characterize reproductive development and spawning activity in female P. setiferus through histology by: 1) defining major phases of reproductive development; 2) investigating and distinguishing the characteristics of oocyte atresia; and 3) using a standardized framework to describe the phenology of ovarian development in P. setiferus. Weekly samples of female P. setiferus were collected from March to June 2022 and ovarian tissues from 520 individuals were processed histologically. A detailed framework for distinguishing microscopically-observed ovarian development phases based on defining oocyte characteristics is provided. Oocyte atresia was observed in the ovarian tissue of 51% (N = 264) of individuals examined, with further examination differentiating between non-spawning atresia (N = 205) and post-spawning atresia (N = 59). Individuals with no atresia and non-spawning atresia were present from all sampling events, whereas individuals with post-spawning atresia first appeared on 22 April 2022. Our descriptions of ovarian development and oocyte atresia contribute to a growing framework of standardized microscopic assessments that should be tested more broadly for applicability to other commercially important crustaceans.