Sperm adaptation in relation to salinity in three goby species

Abstract

In externally fertilizing species, the gametes of both males and females are exposed to the influences of the environment into which they are released. Sperm are sensitive to abiotic factors such as salinity, but they are also affected by biotic factors such as sperm competition. In this study, the authors compared the performance of sperm of three goby species, the painted goby, Pomatoschistus pictus, the two-spotted goby, Pomatoschistus flavescens, and the sand goby, Pomatoschistus minutus. These species differ in their distributions, with painted goby having the narrowest salinity range and sand goby the widest. Moreover, data from paternity show that the two-spotted goby experiences the least sperm competition, whereas in the sand goby sperm competition is ubiquitous. The authors took sperm samples from dissected males and exposed them to high salinity water (31 PSU) representing the North Sea and low salinity water (6 PSU) representing the brackish Baltic Sea Proper. They then used computer-assisted sperm analysis to measure the proportion of motile sperm and sperm swimming speed 10 min and 20 h after sperm activation. The authors found that sperm performance depended on salinity, but there seemed to be no relationship to the species' geographical distribution in relation to salinity range. The species differed in the proportion of motile sperm, but there was no significant decrease in sperm motility during 20 h. The sand goby was the only species with motile sperm after 72 h.

Molecular, behavioural and morphological comparisons of sperm adaptations in a fish with alternative reproductive tactics

“…There was no difference in sperm longevity between the two male morphs, and both morphs showed very long‐lived sperm. This result is in line with previous findings from sand gobies and a few other goby species (Green & Kvarnemo, 2019 ; Lindström et al, 2021 ; Nakanishi & Takegaki, 2019 ). Here, we found that all but two males had motile sperm after 22 h, and some had motile sperm even after 48 h. Comparing sperm movement after 5 min and 22 h, we found no decrease in sperm motility over time and only a slight and nonsignificant decline in velocity in 2012.…”

“…Sperm of many externally fertilising fishes have a very short lifespan after activation, on the timescale of seconds to minutes (Cosson, 2004 ; Dzyuba & Cosson, 2014 ). However, in the Family Gobiidae, multiple species show sperm lifespans that exceed hours, and even days (Green & Kvarnemo, 2019 ; Lindström et al, 2021 ; Locatello et al, 2007 ; Nakanishi & Takegaki, 2019 ; Scaggiante et al, 1999 ). In the same Family, males also have accessory glands (referred to as sperm‐duct glands) that produce a protein‐rich, mucus‐based substance that has an important impact on the micro‐environment around the gametes (Fishelson, 1991 ; Young & Fox, 1937 ).…”

“…We used motility after 22 h to provide measures of sperm longevity. Twenty‐two hours was chosen based on a previous study that found sperm to be motile for ≥22 h in the sand goby and two congeners (Lindström et al, 2021 ). In a second experiment, we measured the same sperm performance traits in the presence or absence of the fluid from the sperm‐duct gland.…”

Evidence of prezygotic isolation, but not assortative mating, between locally adapted populations ofFundulus heteroclitusacross a salinity gradient

“…For instance, sand goby, Pomatoschistus minutus , and Atlantic herring, Clupea harengus , both show divergence in sperm motility between populations locally adapted to different salinities (Berg et al ., 2019; Leder et al ., 2021). Further, salinity specific sperm motility is common between closely related species that occupy different osmotic environments (Elofsson et al ., 2003; Lindström et al ., 2021). Our results support these previous studies and show that low salinity drives a small reduction in fertilization success for BW-native♀ (Fig.…”

Ten years of marine evolutionary biology—Challenges and achievements of a multidisciplinary research initiative

“…Since the sand goby is an externally fertilizing fish, local adaptation of gamete function in relation to salinity is particularly interesting. De novo sequencing of the sand goby genome together with common‐garden experiments with sperm assays and cross‐population matings in different salinities, allowed a team of CeMEB researchers to explore the importance of local adaptation of gametes along the species’ geographical distribution (Leder et al, 2021 ; Lindström et al, 2021 ; Svensson et al, 2017 ). This research also resulted in a new concept, ‘immigrant reproductive dysfunction’, as an important mechanism for reduced gene flow, local adaptation and speciation (Svensson et al, 2017 ).…”