Histopathologic Prevalence and Severity of Testicular Oocytes in Smallmouth Bass from Two Archival Collections

Abstract

During recent decades, survey studies have documented the widespread presence of oocytes in the testes of male Smallmouth Bass Micropterus dolomieu collected from surface waters throughout the United States. There are few published reports of testicular oocytes (TO) in Smallmouth Bass before the 1990s, so it is difficult to know how long this has been occurring. Consequently, this study was conducted to evaluate the prevalence and severity of TO occurrence in whole fish specimens from two archival collections—the Smithsonian Institution's National Museum of Natural History in Suitland, Maryland, and Cornell University's Museum of Vertebrates in Ithaca, New York. Gonads were excised from 167 preserved male Smallmouth Bass that were originally collected between 1875 and 2004, and routine histologic sections were prepared and examined. The severity of TO was determined using a semiquantitative scoring system. Overall, 52.1% of male Smallmouth Bass were found to have TO. Affected fish had been collected in 11 of the 18 represented states, and TO were found in specimens harvested during decades as early as the 1880s and 1900s. Unfortunately, the small number of samples acquired at the earliest time periods precluded analyses of prevalence and severity trends over time. The results of this study demonstrated that the phenomenon of TO in male Smallmouth Bass is at least a century old and confirmed the widespread nature of this finding throughout the species’ historic range. Further research efforts should focus on determining the baseline prevalence of TO in laboratory‐reared male Smallmouth Bass that have not been exposed to endocrine active substances or the effects of experimental estrogen exposure on such fish.

Adverse Outcome Pathway on Androgen receptor agonism leading to male-biased sex ratio

“…In these instances classification of individuals as male versus female may not be possible, requiring a third category related to an intersex condition. There are seemingly multiple underlying causes of intersex, one of which appears to be exposure to estrogenic chemicals during gonad differentiation (Jobling et al 1998;Norris et al 2018;Grim et al 2020).…”

Adverse Outcome Pathway on Aromatase inhibition leading to male-biased sex ratio via impacts on gonad differentiation

“…requiring a third category related to an intersex condition. There are seemingly multiple underlying causes of intersex, one of which appears to be exposure to estrogenic chemicals during gonad differentiation (Jobling et al 1998;Norris et al 2018;Grim et al 2020).…”

Endocrine Disruption Is Reduced but Still Widespread in Wild Roach (Rutilus rutilus) Living in English Rivers

“…Endocrine disruption in fish arising from exposure to chemicals emanating from wastewater treatment works (WwTW) effluents has been under investigation since the 1990s. The original study in the United Kingdom identified elevated concentrations of a female egg yolk precursor, vitellogenin (VTG), in the plasma of caged male rainbow trout exposed to WwTW effluent, and the studies that followed showed the tissue level effects in fish living downstream of WwTW outfalls or in fish experimentally exposed to WwTW effluents. − In those studies, normally gonochoristic fish species displayed intersex phenotypes whereby the gonadal tissue contains both developing eggs and sperm, and/or the fish had reproductive duct abnormalities, i.e., oviducts present simultaneously with sperm ducts. , The intersex condition and elevated VTG plasma concentrations/gene expression in male fish have now been reported in wild fish populations globally. − Furthermore, fish with high levels of intersex have been shown to be adversely impacted, with altered gamete maturation and reduced reproductive success. ,− …”