Investigating the Utility of Measuring 11α‐Ketotestosterone and Vitellogenin in Surface Mucus as an Alternative to Plasma Samples in Assessments of the Reproductive Axis of White Bass

Abstract

Sex steroids and vitellogenin measured in plasma have been used in a variety of fish species to investigate the reproductive system. Surface mucus has been shown to be an effective substitute for plasma in several species of fish. The goal of this study was to investigate the utility of mucus sampling as an approach to investigating the hypothalamic–pituitary–gonadal (HPG) axis in White Bass Morone chrysops. We measured 11α‐ketotestosterone and vitellogenin in both surface mucus and plasma samples from White Bass collected from a wild population during their annual spawning migration. Mucus and plasma samples were collected from male and female White Bass that were treated to stimulate the HPG axis (carp pituitary extract, 10 mg/kg; estradiol, 10 mg/kg) or treated with saline injections. Mucus and plasma concentrations of both vitellogenin and 11α‐ketotestosterone were positively correlated with one another. Treatments with estradiol led to higher amounts of vitellogenin in both plasma and mucus in both male and female fish. Assessments of 11α‐ketotestosterone in mucus correctly identified the sex of 90% of spawning White Bass, as did vitellogenin in 94%. These data demonstrate the potential utility of mucus sampling as a tool to less invasively assess the annual reproductive cycle, identify stimulation of the HPG axis, and identify fish sex in hatchery populations of White Bass.

Mucus phosphoproteins as an indirect measure of endocrine disruption in native small-bodied freshwater fish, exposed to wastewater treatment plant and pulp and paper mill effluents

“…Rainbow trout exhibited a signifi cant correlation between measurements of VTG levels in the plasma and mucus. The same signifi cant correlation between plasma and mucus VTG concentrations have been described in goldfi sh C. auratus (Wang et al 2015), white bass Morone chrysops Rafi nesque 1820 (Barkowski & Haukenes 2014), copper redhorse Moxostoma hubbsi Legendre, 1952, andshorthead redhorse Moxostoma macrolepidotum (Lesueur, 1817;Maltais & Roy 2009). Therefore, fi sh mucus is supported as a viable, non-lethal matrix for quantifying VTG levels, one of the most common endocrine disruption indicators.…”

Comparative study on accuracy of mucosal estradiol‐17β, testosterone and 11‐ketotestosterone, for maturity, and cutaneous vitellogenin gene expression in goldfish (Carassius auratus)

“…To optimize aquaculture and fisheries management, knowledge of sex identification and reproduction outputs is still required for discussion. In dealing with the sex ratios of hermaphrodite species, or managing the maturity stages of commercial and endangered species, all aspects of properties must be considered (Barkowski & Haukenes, 2014; Budd et al ., 2015; Chen et al ., 2020). In any case, finding low‐invasive tool could become a promising way to determine reproduction contents.…”

“…In recent years, mucus has attracted increasing attention because of providing information about fish immunity system (Abolfathi et al ., 2020; Roosta et al ., 2014; Sanahuja et al ., 2019; Subramanian et al ., 2008), the effects of environmental pollutants on fish physiology (Bulloch et al ., 2020; Fernández‐Alacid et al ., 2018; Meucci & Arukwe, 2005), as well as increasing our knowledge in reproduction status (Barkowski & Haukenes, 2014). Furthermore, mucus might be a preferred sampling method to blood, as it prevents fish sacrificing, minimizes the physiological stress and can be collected at different sampling points if required (Schultz et al ., 2005; Ekman et al ., 2015; Dzul‐Caamal et al ., 2016; Oliveira et al ., 2018).…”

“…Furthermore, mucus might be a preferred sampling method to blood, as it prevents fish sacrificing, minimizes the physiological stress and can be collected at different sampling points if required (Schultz et al ., 2005; Ekman et al ., 2015; Dzul‐Caamal et al ., 2016; Oliveira et al ., 2018). Skin mucosal tissue indeed contains a lower concentration of reproduction substances comprising 11‐KT (Barkowski & Haukenes, 2014; Schultz et al ., ) and VTG (Moncaut et al ., 2003; Pottinger et al ., 2005; Kohn et al ., 2013; Barkowski & Haukenes, 2014) rather than blood plasma. Their contents, therefore, may be less effective to identify the sex ratio or maturity stages (Kohn et al ., 2013).…”

Exploring sample cross‐contamination in fish epidermal mucus

“…functions in osmoregulation, excretion, immune defence and respiration, epidermal mucus serves as a repository for the elemental and molecular components of these processes, such as corticosteroids, sex steroids and stable isotopes (Barkowski & Haukenes, 2014;Church et al, 2009;Guardiola et al, 2016;Shephard, 1994). In addition, because it is continuously secreted and replaced, the composition of a fish's epidermal mucus can provide information on the fish's physiological condition (Subramanian et al, 2007).…”