Effects Of Different Mating Histories Of Misumenops Tricuspidatus (Fabricius) On Mating Behavior And Fitness

Ethology focuses on the study of animal behavior under natural conditions, which involves a variety of behavior changes both under the external environment and internal environment. Mating and reproductive behavior has been one of the hot spots of ethology. There often exist competitions for mating and reproductive paternity between animals who have multiple mating behavior, which generally showing that their mating behavior all or partially support Coolidge effect and male reproductive investment. Spider mating patterns can be divided into single mating and multiple mating. Spider multiple matings not only have complex effects on the spider’s reproductive investment, but also have a variety of effects on offspring fitness. The male and female spiders of Misumenops tricuspidatus (Fabricius) have multiple mating behavior. Therefore, it appears to be an excellent model system to study parental investment of spiders with different mating history and its influence on offspring fitness. Here, we selected the crab spiders Misumenops tricuspidatus as the model system to shed some light on parental investment of spiders with different mating history and its effects on the offspring fitness.The male and female of Misumenops tricuspidatus can multiply mate in their lifetime. Males are able to distinguish female’s gender and locate its position by the silk of the female. Males can detect the reaction of a female by using the first and second pairs of walking legs to touch the back of the female to determine whether the female spider was ready to mate. During mating, a male will repeatedly insert the palpal organ into the genital operculum of the female, inputting semen until one of the couple terminates mating. There exists obvious fighting behavior among males, it terminates as one male in the competition for mating rights was paralytic or dead. Females produce the first egg sac about7days after their first mating, and the spiderlings will hatch from egg sac in11days. Females can lay multiple egg capsules, but only parts of them could hatch.In order to verify the effects of different mating history of Misumenops tricuspidatus on the mating behavior, we first compared the time of mating latency, mating duration and mating rounds of male Misumenops tricuspidatus mated with the mate with different mating history. The result showed that the male Misumenops tricuspidatus has the ability to distinguish the mating history of female. Male Misumenops tricuspidatus increased its reproductive investment to obtain higher genetic benefits by extending mating duration when mated with female which had mated with another male. When a male mated with two virgin female, a significantly shorter mating duration was detected in the second mating. It meant that the male Misumenops tricuspidatus could strategically adjust its reproductive investment in accordance with female mating histories. The results conform with the sperm competition risk model, partially in line with the sperm competition intensity mode, and partially supported Coolidge effect. When the male Misumenops tricuspidatus mated with females which had mated with another male, the male spider would invest more time to prepare mating. It was probably because the male spider needed more time to use palpal organ for inhaling more sperm or the male needed more time to distinguish the female which had mated with another male. No difference was detected in mating rounds of Misumenops tricuspidatus mated with their mates which had different mating history.We compared if there exists differences in the number of eggs and spiderlings hatched from the females with different mating combinations, verifying the effect of Misumenops tricuspidatus multiple copulations on female fitness. A significantly lower number of spiderlings from the females which mated with two virgin males than the females which mated once was detected. It showed that female multiple copulations decreased the fertilization rate of the eggs. That could be the results of conflict between sperm replace ability and sperm defense ability of the males. There was a negative correlation between the number of eggs produced by the female and mating frequencies of female, it could be because female would take higher cost, consequently decreased the reproductive investment.To verify the effect of multiple copulations of Misumenops tricuspidatus on offspring fitness, we compared the differences in the survival days under different temperatures and the carapace width of the spiderlings hatched from the females with different mating patterns. The results showed a significant difference in survival days at30℃and at15℃, while there was no difference at25℃. The survival days of offsprings at15℃and30℃from females which mated with different males is significantly higher than females which mated twice with the same male and the females which mated only once. It seems likely that females may obtain genetic benefits by mating with multiple males, increasing the tolerance of offspring at low and high temperature.Meanwhile, we investigated Misumenops tricuspidatus mate choices when spiders facing mates with different mating history to shed some light on mate choice mechanism. No preference was detected in female mate choice, showing that female couldn’t dominate mating. When one male gives chooses between females which had mated with another male and virgin female, the male preferred to mate with virgin female. This showed that male dominate mating behavior. When a male encountered females with different mating history, the male could distinguish the female mating history and preferentially choose virgin female as a mate. This result partially supported Coolidge effect.