User:Mtimmons2/sandbox

Habitat/Hunting Behaviors:

Cherax, also commonly known as Cherax dispar or yabbies, are a species of crayfish endemic to freshwater inland waterways of south-eastern Australia. As a result of aquaculture, feral populations have become established outside normal range in recent years. Numerous translocated populations have been recorded in coastal drainages in New South Wales, where a large diversity of endemic coastal crayfishes occur. Cherax pose a great threat to the indigenous species in these waterways due to competition and predation, as well as pathogenic concerns and other impacts on the ecosystem (Coughran, 2012). Cherax are prohibited from the United States, they are not allowed to be personally possessed or used for commercial activities due to the danger they pose to the current ecosystem being an invasive species, especially harming other crayfish species in the area. They are opportunistic and omnivorous feeders. They will eat just about anything that crosses their paths if they are hungry enough. Their diet consists of, but is not limited to, plants, algae, macrophytes, snails, insects, and tadpoles. Cherax grip live food in their large front claws and when the prey is no longer moving, they pass it along to their smaller claws that sit right below their mouths and pick apart small pieces to place in their mouths (Beatty, 2005).

Reproduction:

Mating season for Cherax is during early spring. After fertilization, eggs develop inside the mother’s body for 4 to 6 weeks(Crayfish, n.d.). After that period, the eggs transition to the outside of the mothers body and rest on the female’s tail (Crayfish, n.d.). Then the eggs continue to develop and hatch in spring (Crayfish, n.d.). Both sexes of Cherax are selective with copulation partners. Females tend to choose male with a larger central mass (abdomen and tail) and chelipod (Aquiloni & Gherardi, 2008). Males tend to select copulation partners who have larger body sizes and are virgins. Opposed to females who were more dominant or had symmetrical chelipods (Aquiloni & Gherardi, 2008). As part of a mating/copulation ritual males and females fight each other. This allows the female to test the strength of the male to determine if they will produce profitable offspring (Berry & Breithaupt, 2010). During the fight both release urine. The female’s release of urine triggers a sexual response from the male (Berry & Breithaupt, 2010). The males release of urine is an aggressive response towards the fight with the female. When the male smells the female's urine it will stop releasing its own, hoping the female will allow them to copulate. Once the female has allowed the male to deposit its sperm. The male will position itself on its back and deposit its sperm (Barki & Karplus, 1999). Unlike other crayfish species the Cherax dispar does not use its chelipod to cage females during copulation. It is mainly used during mating when the males and females fight.

Animal Behaviors: The slender crayfish (Cherax dispar) are one of many animals that resolve conflicts with displays of strength without the need to participate in physical combat allowing them the opportunity to benefit from dishonest signaling regarding strength. Both sexes of Cherax dispar (C. dispar) utilize their chelae when intimidating or engaging in agonistic encounters with rivals (Seebacher, n.d.). C. dispar uses either dishonest or honest signaling depending upon whether they are male or female. Studies have found that male C. dispar use dishonest signaling of strength through their enlarged front claws, termed chelae, which they use in threatening displays to their competitors (Wilson et al., 2007). Males engage in chelae displays to indicate dominance prior to engaging in violent contact and such displays are capable of completely deescalating an altercation over 80% of the time (Seebacher, n.d.). In males, larger chelae result in greater dominance; however, the actual strength of one’s chelae does not influence an individual’s dominance as a result of dishonest signaling (Seebacher, n.d.). In instances when displaying males have chelae of a similar size, they will engage in combat and those with the greater chelae closing force will win (Bywater et al., 2008). Female C. dispar use honest signaling of strength meaning the size of their chelae is a good indication to other C. dispar about that individual's strength (Bywater et al., 2008). Individuals possessing larger chelae engage in more agonistic encounters and are also more likely to win (Bywater et al., 2008). In a study of female C. dispar chelae strength, they found that chelae size also indirectly indicated the dominance of the female because of its honest indication of strength (Bywater et al., 2008). In a study of functional trade-offs of chelae size, experimenters found that enlarged chelae negatively correlated to escape swimming performance in males but not in female C. dispar (Wilson et al., 2009). Therefore, indicating that large chelae in males could act as a handicap if they needed escape from a competitor or predator(Wilson et al., 2009). The chelae muscles of male slender crayfish produce only half of the force that female chelae muscles are capable of producing, indicating that males invest more resources into developing larger chelae for intimidation purposes than they do for producing functioning chelae muscle (Seebacher, n.d.). Between unfamiliar opponents, chelae closing force determines the winner of agonistic encounters; however, the recognition of individuals and their fighting abilities amongst slender crayfish that previously engaged in fights will influence who wins in future encounters (Seebacher & Wilson, 2007). This mechanism reduces the number of physical encounters a single individual will have to engage in (Seebacher & Wilson, 2007). Male C. dispar have a clear cost-benefit relationship as a result of using dishonest signaling. The costs include decreased escape, increased predation and increased need for resources in order to grow the enlarged chelae. While the male C. dispar benefits from its ability to win more conflicts without having to expend excess energy by engaging in a physical conflict.