Fertilization strategies for winter flounder: effects of spermatozoa density and the duration of gamete receptivity

Abstract

Winter flounder is one of the most commonly used models for studying fish biology in North America; however little is known about their reproductive ecology, especially during the spawning event. The objectives of this research were to determine the optimal number of spermato zoa required to fertilize eggs and to explore how long spermatozoa (30 to 240 s post-activation) and eggs (30 to 7680 s post-activation) are receptive to fertilization after exposure to seawater. We conducted experiments using gametes from wild-caught fish and measured fertilization success by examining eggs at 5 to 6 d post-fertilization. On average 34 038 sperm cells per egg were required to fertilize 81.3% of the eggs. Duration after spermatozoa activation had an effect on the proportion of eggs fertilized (F 3, 6.69 = 338.38; p < 0.0001; mixed-model ANOVA). At 30 s post-spermatozoa activation, 98% of the eggs were fertilized. After 60 s, a significant decrease in fertilization success was detected. Duration after egg exposure to seawater had an effect on the proportion of eggs fertilized (F 8,16 = 19.89; p < 0.0001;. For all trials (30 to 1920 s), the percentage of eggs fertilized ranged from 61 to 90%. A significant decrease to 11% occurred at 3840 s after egg exposure. This area of research has particular importance for our understanding of reproductive strategies, evolutionary challenges, reproductive potential and recruitment. In addition, examining sperm-egg interactions provides information important to management of living and frozen-thawed gene banks. KEY WORDS: Marine fish · Reproduction · Sperm · Egg · Fisheries · Aquaculture · Segmented regressionResale or republication not permitted without written consent of the publisher Aquat Biol 16: 115-124, 2012 gian coastal origin starts in August and continues for about 6 months and the number of pre-spawning spermatogonia present in the testes essentially determines the numbers produced each season (Almeida et al. 2008). In addition, since most fishes are external fertilizers and the medium in which the spermatozoa is released can be turbulent, i.e. oceans and rivers (Trippel 2003, Faria et al. 2006), there may not be an 'unlimited' number of spermatozoa available to fertilize eggs released by females in these environments.Spermatozoa longevity and egg receptivity -the length of time an egg is receptive to be fertilized by a sperm cell -also impact the success of a fertilization event (Kjørsvik & Lønning 1983, Trippel & Morgan 1994, Butts et al. 2009). For instance, if female mate choice is important, then eggs may be receptive for a short period of time to reduce the chance of fertilization by non-desirable males. In contrast, if eggs are receptive for longer periods of time then the probability of fertilization by multiple males should in crease; this may be important in situations when the probability of spermatozoa to egg encounters are low (Trippel 2003). If spermatozoa are viable for longer periods of time, then the potential of contacting and fertilizing an egg ...

Sperm traits of masculinized fish relative to wild‐type males: a systematic review and meta‐analyses

“…Between study variation in the ratio of sperm to eggs used in trials of reproductive success could also drive heterogeneity; optimal egg to sperm ratios have been investigated in only a handful of species (Butts et al . ).…”

“…Between female differences in quality could thus potentially drive some of the heterogeneity that we observed in the reproductive success data set. Between study variation in the ratio of sperm to eggs used in trials of reproductive success could also drive heterogeneity; optimal egg to sperm ratios have been investigated in only a handful of species (Butts et al 2012).…”

Fertilization strategies for Sea Bass Dicentrarchus labrax (Linnaeus, 1758): effects of pre-incubation and duration of egg receptivity in seawater

“…On the other hand, when longevity of sperm is very short, than egg receptivity may be necessary to increase fertility, since longer periods of egg receptivity are predicted to increase the probability of a successful fertilization event (Trippel ). Therefore, duration of egg receptivity provides valuable insights on reproductive behaviour for any fish species (Butts, Roustaian & Litvak ).…”

Evaluation of Methods to Determine Sperm Density for the European eel, Anguilla anguilla

“…As such, research has focused on how to optimize fertilization strategies for a given species (Butts et al. , ). Standardizing the sperm to egg ratio is one such technique that has been used to improve fertilization rates (Suquet et al ; Bart and Dunham ; Christopher et al ).…”

“…For several species of marine finfish, it is challenging to produce high-quality gametes for fertilization (Bobe and Labb e 2010). As such, research has focused on how to optimize fertilization strategies for a given species (Butts et al 2009(Butts et al , 2012. Standardizing the sperm to egg ratio is one such technique that has been used to improve fertilization rates (Suquet et al 1995;Bart and Dunham 1996;Christopher et al 2010).…”