The in vitro effect of temperature on motility and antioxidant response of common carp Cyprinus carpio spermatozoa

Effects of captan, mancozeb and azoxystrobin fungicides on motility, oxidative stress and fatty acid profiles in rainbow trout (Oncorhynchus mykiss) spermatozoa

An in vitro study using rainbow trout spermatozoa was designed to evaluate the toxic effects of different concentrations of captan (CPT), mancozeb (MCZ), and azoxystrobin (AZX) fungicides on motility parameters, lipid peroxidation, SOD activity, total antioxidant capacity (TAC), and DPPH inhibition. Moreover, changes in fatty acids profiles caused by the fungicides were determined for the first time. The results revealed that motility parameters, SOD activities, TAC values, and DPPH inhibitions decreased significantly while lipid peroxidation increased after ≥2 µg/L of CPT, ≥1 µg/L of MCZ, and ≥5 µg/L of AZX incubations for 2 h at 4 °C. Additionally, 10 µg/L CPT, 5 µg/L MCZ, and 200 µg/L AZX reduced motility to the 50 % level. Our results clearly demonstrated significant changes in the fatty acids profiles of spermatozoa exposed to these concentrations of the fungicides. The highest lipid peroxidation and the lowest monounsaturated and polyunsaturated saturated fatty acids (MUFA and PUFA, respectively) were detected in AZX. Even though the susceptibility of spermatozoa to oxidative damage is generally attributed to PUFA contents, the results of this study have represented that MUFA content could play a part in this tendency. Moreover, the lower concentration of MCZ reduced motility to the % 50 level while it deteriorated the fatty acids profile less than did AZX. Overall, the present study demonstrated that the detrimental effects of the fungicides on mitochondrial respiration and related enzymes have more priority than oxidative stress in terms of their toxicities on spermatozoa. It has also been suggested that fish spermatozoa are a good model for determining changes in the fatty acid profiles by fungicides, probably, by other pesticides and environmental contaminants as well.

In vivo exposure to high temperature compromises quality of the sperm in Colossoma macropomum

Increases in temperature can affect the reproduction of fish by decreasing the quality of gametes for fertilization. Therefore, this study aimed to evaluate the in vivo effect of temperature on the production and sperm quality of Colossoma macropomum, which is an economically relevant species for Brazil, and other countries. Broodstock were exposed for 10 days at temperatures of 29 °C (n = 4) and 35 °C (n = 4). After exposure, semen was collected and sperm quality was evaluated for kinetic, biochemical, morphological parameters, membrane integrity, and oxygen consumption. The sperm quality of males of specimens of C. macropomum exposed in vivo to the higher temperature was compromised and showed a difference in all the analyses (P < 0.05). Sperm showed decreased motility (51.9 ± 11.6 s) compared to the control (61.3 ± 5.5 s); curvilinear (CLV), straight line (SLV), and average path (APV) velocities decreased, and straightness (STR) and beat cross frequency (BCF) increased; oxygen consumption decreased (32.8 ± 3.4 pmol. (s.ml)-1, picomol per second per ml) compared to the control (46.6 ± 3.5 pmol. (s.ml)-1); and the activity of catalase (CAT) and glutathione S-transferase (GST) enzymes increased and decreased, respectively, in sperm from fish exposed to high temperatures. Furthermore, an increase in non-viable sperm with damaged membranes and sperm with altered morphology was observed. The observed alterations indicate that C. macropomum confined in environments with high temperatures possibly produces more sperm that are unviable for the fertilization process.

Pre-fertilization gamete thermal environment influences reproductive success, unmasking opposing sex-specific responses in Atlantic salmon (Salmo salar)

The environment gametes perform in just before fertilization is increasingly recognized to affect offspring fitness, yet the contributions of male and female gametes and their adaptive significance remain largely unexplored. Here, we investigated gametic thermal plasticity and its effects on hatching success and embryo performance in Atlantic salmon (Salmo salar). Eggs and sperm were incubated overnight at 2°C or 8°C, temperatures within the optimal thermal range of this species. Crosses between warm- and cold-incubated gametes were compared using a full-factorial design, with half of each clutch reared in cold temperatures and the other in warm temperatures. This allowed disentangling single-sex interaction effects when pre-fertilization temperature of gametes mismatched embryonic conditions. Pre-fertilization temperature influenced hatch timing and synchrony, and matching sperm and embryo temperatures resulted in earlier hatching. Warm incubation benefited eggs but harmed sperm, reducing the hatching success and, overall, gametic thermal plasticity did not enhance offspring fitness, indicating vulnerability to thermal changes. We highlight the sensitivity of male gametes to higher temperatures, and that gamete acclimation may not effectively buffer against deleterious effects of thermal fluctuations. From an applied angle, we propose the differential storage of male and female gametes as a tool to enhance sustainability within the hatcheries.

Deleterious effect of gestagens from wastewater effluent on fish reproduction in aquatic environment: A review

Gestagens are common pollutants accumulated in the aquatic ecosystem. Gestagens are comprised of natural gestagens (i.e. progesterone) and synthetic gestagens (i.e. progestins). The major contributors of gestagens in the environment are paper plant mill effluent, wastewater treatment plants, discharge from pharmaceutical manufacturing, and livestock farming. Gestagens present in the aquatic environment interact with progesterone receptors and other steroid hormone receptors, negatively influencing fish reproduction, development, and behavior. In fish, the gonadotropin induces 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) production, an important steroid hormone involved in gametogenesis. DHP interacts with the membrane progestin receptor (mPR), which regulates sperm motility and oocyte maturation. Gestagens also interfere with the hypothalamic-pituitary-gonadal (HPG) axis, which results in altered hormone levels in fish. Moreover, recent studies showed that even at low concentrations exposure to gestagens can have detrimental effects on fish reproduction, including reduced egg production, masculinization, feminization in males, and altered sex ratio, raising concerns about their impact on the fish population. This review highlights the hormonal regulation of sperm motility, oocyte maturation, the concentration of environmental gestagens in the aquatic environment, and their detrimental effects on fish reproduction. However, the long-term and combined impacts of multiple gestagens, including their interactions with other pollutants on fish populations and ecosystems are not well understood. The lack of standardized regulations and monitoring protocols for gestagens pollution in wastewater effluent hampers effective control and management. Nonetheless, advancements in analytical techniques and biomonitoring methods provide potential solutions by enabling better detection and quantification of gestagens in aquatic ecosystems.

Frequency-dependent viscosity of salmon ovarian fluid has biophysical implications for sperm-egg interactions

Gamete-level sexual selection of externally fertilising species is usually achieved by modifying sperm behaviour with mechanisms that alter the chemical environment in which gametes perform. In fish, this can be accomplished through the ovarian fluid, a substance released with the eggs at spawning. While the biochemical effects of ovarian fluid in relation to sperm energetics have been investigated, the influence of the physical environment in which sperm compete remains poorly explored. Our objective was therefore to gain insights on the physical structure of this fluid and potential impacts on reproduction. Using soft-matter physics approaches of steady-state and oscillatory viscosity measurements, we subjected wild Atlantic salmon ovarian fluids to variable shear stresses and frequencies resembling those exerted by sperm swimming through the fluid near eggs. We show that this fluid, which in its relaxed state is a gel-like substance, displays a non-Newtonian viscoelastic and shear-thinning profile, where the viscosity decreases with increasing shear rates. We concurrently find that this fluid obeys the Cox-Merz rule below 7.6 Hz and infringes it above this level, thus indicating a shear-thickening phase where viscosity increases provided it is probed gently enough. This suggests the presence of a unique frequency-dependent structural network with relevant implications for sperm energetics and fertilisation dynamics. This article has an associated ECR Spotlight interview with Marco Graziano.

Sperm maturation, migration, and localization before and after copulation in black rockfish (Sebastes schlegelii)

Sebastes schlegelii is a typical viviparous teleost with six months sperm storage duration from November to April. In this study, spermatozoa morphological and physiological characteristics and sperm location in the female ovary were investigated by electron microscopy, computer-assisted sperm analyzer and histologic analysis, respectively. During copulation, we observed that spermatozoa in the testis had mature structure with rod-shaped head, a short midpiece, and a long flagellum. And further verified sperm swam freely at a high speed in the ovary fluid. After copulation, we only found swimming sperm in the ovary fluid at the early storage stage (November to December) and the majority of sperm were scattered randomly in the ovary cavity and partially concentrated in the crypt between the oocyte and stalk of follicle. Thereafter, the ovarian epithelium around the oocytes proliferated rapidly and wrapping spermatozoa outside of the follicular layer and formed a lot of crypts outside of the follicular layer which served as the sperm storage site until fertilization. The present findings would be useful for further understanding the mechanism of long-term sperm storage in viviparous teleost.

Sperm antioxidant system in ocellate river stingray Potamotrygon motoro at transition from seminal vesicle to cloaca

The importance of reactive oxygen species and the antioxidant system in sperm biology has been recognized for different bony fishes but nothing is known in this regard for chondrichthyans. For the first time for cartilaginous fishes, the enzymatic antioxidant system was shown herein to be present in both fractions of sperm (spermatozoa and seminal fluid) collected from two different places (seminal vesicle and cloaca). In internally fertilizing freshwater ocellate river stingray, Potamotrygon motoro, the activity of superoxide dismutase and glutathione peroxidase was not changed upon sperm transition from the seminal vesicle to the cloaca. The activity of catalase was significantly increased for both sperm fractions at transition from the seminal vesicle to the cloaca (1.6 times for spermatozoa and 1.9 times for seminal fluid). The role of the sperm antioxidant system for different aspects of internal fertilization is discussed. The presented results are the initiatory step in uncovering the biochemical events of internal reproduction in Chondrichthyes.

High Temperature, pH, and Hypoxia Cause Oxidative Stress and Impair the Spermatic Performance of the Amazon Fish Colossoma macropomum

The control of abiotic parameters is fundamental for fish survival, growth and reproduction. These factors have a direct effect on sperm quality. Thus, this study evaluated the effect of different temperatures (29, 31, 33, and 35°C), pHs (4 and 8), and hypoxia (1 mgO₂ L⁻¹) on sperm motility of Colossoma macropomum (tambaqui). The results indicated a longer duration of sperm motility at 29°C (50.1 ± 2.70 s) that progressively decreased when exposed to 35°C (31.2 ± 1.31 s) and hypoxia at pH 4 (27.4 ± 1.42 s) and pH 8 (30.44 ± 1.66 s; p < 0.05), respectively. Sperm oxygen consumption increased in hypoxia at both pH (pH 4 = 61.22; pH 8 = 54.74 pmol s⁻¹). There was an increase in the activity of glutathione-S-transferase (GST) and superoxide dismutase (SOD), as well as in lipid peroxidation levels (LPO) and DNA damage in sperm exposed to higher temperatures and hypoxia. The pH 4 and pH 8 under normoxia did not affect the quality of C. macropomum sperm. These results suggest that water warming and acidification, consequences of climate changes, significantly affect the reproduction of C. macropomum, reducing the quality of spermatozoids during fertilization.

In vitro antioxidant enzyme activity and sperm motility at different temperatures in sterlet Acipenser ruthenus and rainbow trout Oncorhynchus mykiss

Influence of in vitro temperature on sperm antioxidant enzyme activity, thiobarbituric acid-reactive substance (TBARS) content and motility parameters was evaluated in sterlet Acipenser ruthenus and rainbow trout Oncorhynchus mykiss. Sperm activation was conducted at 4, 14 and 24 °C in both species. Duration of motility was significantly longer at 4 °C than at 14 and 24 °C in both species. At 60 s post-activation, the velocity of sterlet spermatozoa was highest at 24 °C. This trend continued to 420 s post-activation. In rainbow trout, at 10 s post-activation, the highest velocity was observed at 14 °C. Significantly higher catalase activity was seen at 4 °C in both species. No significant difference in spermatozoon superoxide dismutase activity among temperatures was observed. In sterlet, TBARS content was significantly higher at 24 °C compared to other temperatures, but, in rainbow trout, it was highest at 4 °C. The results presume species-specific level of antioxidant enzyme activity and TBARS content at studied temperatures.

Effects of temperature on sperm motility of burbot Lota lota: spontaneous activation and calcium dependency

Several factors regulating activation of spermatozoon motility in Eurasian burbot, Lota lota, including osmolality, calcium (Ca²⁺ ) ions, and temperature were investigated. Spermatozoon motility in Eurasian burbot, Lota lota was assessed at 4 and 30°C in seminal fluid, isotonic media (with and without Ca²⁺ ) and hypotonic media (with and without Ca²⁺ ). Spermatozoa were spontaneously activated in seminal fluid at 20°C and the maximum motility was recorded at 30°C, which is out of the spawning temperature range, indicating that no risk of activation occurs during routine semen handling in artificial insemination. Initiation of spermatozoon motility in L. lota is mediated by Ca²⁺ and sensitivity to Ca²⁺ is dependent on temperature.

Sperm motility in fish: technical applications and perspectives through CASA-Mot systems

Although a relatively high number of sperm quality biomarkers have been reported over the years in several fish species, sperm motility is nowadays considered the best biomarker for fish spermatozoa. The first scientific reports focusing on fish sperm motility date from a century ago, but the objective assessment allowed by computer-aided sperm analysis (CASA-Mot) systems was not applied to fish species until the mid-1980s. Since then, a high number of sperm kinetic parameters from more than 170 fish species have been reported in more than 700 scientific articles, covering a wide range of topics, such as sperm physiology, sperm storage, broodstock management, the phenomenon of sperm competition, ecotoxicology and understanding the life cycle of the species. The sperm kinetic parameters provided by CASA-Mot systems can serve as powerful and useful tools for aquaculture and ecological purposes, and this review provides an overview of the major research areas in which fish sperm motility assessment by a CASA-Mot system has been used successfully.

Fish sperm biology in relation to urogenital system structure

Morphology of the urogenital system has evolved during fish speciation. Chondrostei (sturgeons and paddlefishes) possess an excretory system which is called "primitive" in that the sperm ducts enter the kidneys and share the excretory ducts where sperm is mixed with urine before it is released into the spawning environment. Further, in this group of fishes there are also physiological characteristics which are associated with these anatomical features where the mixing of sperm and urine is a prerequisite for the final sperm maturation rather than contamination. In the Holostei (gars and bowfins) which are closely related to the Chondrostei, sperm also naturally mixed with urine, but the physiological role of such mixing for sperm biology has not been described. In contrast, urinary and sperm ducts in the more evolved Teleostei are completely separate, and sperm and urine are not mixed before being released during spawning. Thus, urine constitutes an inappropriate environment which can be a source of problems when sperm is collected during fisheries practices. In this review, the consequences of such divergent conditions in the urogenital anatomy will be considered in relation to general features of fish sperm biology and in relation to aquaculture and fisheries practices.

Sperm motility of the Nile tilapia (Oreochromis niloticus): Effects of temperature on the swimming characteristics

Results of previous studies with different fish species, mostly from temperate- or cold-water habitats, indicate a species-specific diversity regarding the relationship between environmental temperature and values for sperm motility variables. In the current study, there was appraisal of environmental temperature effects on sperm motility of tilapia Oreochromis niloticus, a tropical fish species selected because of its aquaculture importance and capacity to reproduce in a broad range of water temperatures. Effects of environmental temperature on the spermatozoa motility characteristics were studied by temperature-controlled video-microscopy and CASA analysis at temperature range from 5 to 50 °C. It appeared that the Nile tilapia spermatozoa exhibit an unexpected capacity to express very different velocity characteristics over this temperature range. In the lower temperature range (5-10 °C), the percentage of motile cells was markedly variable among males. An abrupt increase in the linearity index was observed between 15 and 20 °C suggesting a physiological threshold in sperm movement at about 20 °C which is the minimum temperature for reproduction in the Nile tilapia. With faster spermatozoa velocity, there was a reduction of the motility duration at the greater temperatures. Initially, there is an increase in sperm velocity as the temperature increased until the maximal velocity occurred at 40 to 50 °C which is a temperature beyond that which occurs in natural spawning conditions. Results of the present study clearly indicate the importance of considering ambient temperature when charactering sperm motility and in determining optimal temperature conditions for fertilization in fish.

Analysis of common carp Cyprinus carpio sperm motility and lipid composition using different in vitro temperatures

In fish, sperm quality is frequently associated with sperm motility variables. The response of sperm motility to different temperatures varies among species and plasma membrane lipid composition may contribute to variations in findings in previous research. In the present study, sperm motility and lipid composition were analysed between motile or immotile carp Cyprinus carpio sperm at different in vitro temperatures (4, 14 and 24°C). The duration of the period over which sperm motility is sustained was longer at 4°C compared with 14 and 24°C; while sperm velocity was greatest at 24°C. Motile sperm had lesser proportions of 18:3 (n-3) and 22:6 (n-3) fatty acids at 24°C relative to immotile sperm. There was no difference in fatty acid composition of motile and immotile sperm at 4 and 14°C. The total phospholipid content was less in motile than in immotile sperm at 24°C. At 24°C, phosphatidylcholine and phosphatidylserine proportions were less in motile than immotile sperm. It is concluded that lipid composition of motile carp sperm is affected by temperature, with greater temperatures associated with reduced lipid content, elevation of sperm curvilinear velocity and a decreased duration of the period over which motility is sustained.