Browsing by Subject "courtship"
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(2020)Anthropogenic activity has enhanced global warming at alarming rates, causing temperatures to increase and heat waves to occur more frequently. The effects of global warming are prominent in aquatic ecosystems, particularly in the Baltic Sea. Temperature increases and fluctuations in the Baltic Sea create a changing environment and this can affect inhabiting species’ behaviors, specifically behaviors during reproduction. Reproductive behavior influences both the number and quality of offspring born into a population therefore making behavior changes during reproduction important to study. The three-spined stickleback (Gasterosteus aculeatus), an ectothermic animal, inhabits the Baltic Sea and is an ideal species to study reproductive behavioral changes. Although previous studies have researched three-spined sticklebacks in changing environments, none had specifically looked into the effects of rising temperatures and temperature fluctuations on male three-spined stickleback reproductive behavior. The three-spined stickleback is of particular interest because it reproduces in shallow waters which tend to be more affected by temperature changes. In this study, I aimed to investigate behavioral responses of stickleback males to higher temperatures and to temperature fluctuations during reproduction, as well as the consequences the responses have for reproductive success and the viability of offspring. In order to see how this species would cope with rising temperatures and heat waves during reproduction, a comparative climate chamber experiment was executed in Southern Finland at Tvärminne Zoological Station. Males were housed in either 19°C or 14°C for two breeding cycles, and for the second breeding cycle eight males switched temperatures to experience a temperature fluctuation. Results show that during reproduction, three-spined sticklebacks respond to higher temperatures with increased courtship activity, increased parental activity, quicker breeding cycles, and more weight lost. Parental care activity in constant high temperature decreases from the first to the second breeding cycle, while parental activity in constant low temperature increases. During temperature fluctuations, males experiencing a rise in temperature increase their parental care activity, while males experiencing a drop in temperature demonstrate the opposite. However, no significant consequences of temperature and temperature changes for reproductive success and the viability of offspring were detected during the two breeding cycles. Overall, the results of this study would indicate that the three-spined stickleback will prove to be a resilient species, and maintain population growth in the face of increased temperatures and temperature fluctuations in the Baltic Sea.
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(2014)Sexual signals, that are part of animal signalling systems, are important in attracting and competing for mates. Costly sexual signals can vary in honesty. Honest sexual signals convey truthful information about the signaller's condition and quality, reflecting reliably the direct and/or indirect benefits. Eutrophication of the Baltic Sea, which arises from an increased input of nutrients into an ecosystem by human, alters the water turbidity, especially in coastal areas, which affects visual sexual signalling in the three-spined stickleback (Gasterosteus aculeatus). Boosted algal growth increases water turbidity and decreases the amount of light that penetrates the water column, and thus reduces visibility. This change in visibility can affect the honesty of sexual signals. My aim was to study if the three-spined stickleback sexual signals honestly reflect a direct benefit of mate choice, male parenting ability, when the environment changes due to increased water turbidity and if the maintenance of honesty depends on the social setting in the presence of competing males. I studied the maintenance of signal honesty by having two experimental treatments; turbid water treatment and clear water treatment. I had two males interacting in a same experimental aquarium. I showed the males a female and recorded courtship activity twice for 15 minutes. The female was then released and the male followed as well as the time it took to follow the male to the nest were recorded. I photographed the males in days one, two, three and six of the experiment to be able to observe the change in the nuptial colouration. The males were let to spawn and the egg mass was weighted for the eggs received and the eggs hatched. I found that the courtship activity tended to be reduced in turbid water. Increased water turbidity relaxed the association between female mate choice and courtship activity. Increased water turbidity had no significant effect on male red nuptial colouration or on female preference for redness but it reduced the difference between the two males in redness during courtship. Hatching success was found to be higher in clear water. The difference between the chosen and the not chosen male in hatching success tended to be reduced in turbid water. According to my results the honesty of courtship seemed to be maintained by adjusting courtship activity to reflect the lowered hatching success. On the other hand nuptial colouration was not adjusted and was not honest. The hierarchy between males was also weakened in turbid water which gave males an advantage to cheat. I showed that, as in many other species, such as in different bird and whale species, environmental change influences three-spined stickleback signalling and reproduction outcome. It remains to be seen whether sticklebacks will adopt an alternative signalling method, such as size or olfaction, or adjust the present visual signalling system to turbid conditions. Future will show if the changed signalling system can maintain sexual selection of good parental ability. More research is needed to understand the effect of turbidity on reproduction and population viability and uncover the broader influence of changes in the stickleback ecology to the Baltic Sea habitats.
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