Amplexus ✝

Amplexus (Latin "embrace") is a type of mating behavior exhibited by some externally fertilizing species (chiefly amphibians and horseshoe crabs) in which a male grasps a female with his front legs as part of the mating process, and at the same time or with some time delay, he fertilizes the eggs as they are released from the female's body. In amphibians, females may be grasped by the head, waist, or armpits, and the type of amplexus is characteristic of some taxonomic groups. Amplexus involves direct contact between male and female, distinguished from other forms of external fertilization such as broadcast spawning, where sperm and eggs are freely shed into water without direct contact by individuals. In order for amplexus to be initiated, male frogs must first find a mate by attracting one through calls, typically in the evening. Once a male has successfully attracted a mate the process of amplexus begins while the unsuccessful males are forced to continue their search for a mate through further calls. The competition for a female to mate with among males is considered intense as it is not uncommon for a male amphibian to attack an already-amplexed pair of amphibians. When a male amphibian attacks an already-amplexed pair of amphibians he is trying to force the other male to release its grasp of the female so he can then mate with her. Male amphibians are also known to show mate-guarding behaviour, which is shown after amplexus and it is the males attempt to prevent the female amphibian from mating with other males. The duration of amplexus has been found to vary across different species as in some species it has been found to last for many days but in other species, it has been found to last a few hours. Despite the variation in the duration of amplexus across different species, typically all the species that exhibit this behaviour have to use their forelimb muscles for the whole duration of amplexus. Studies have found that this reproductive behaviour of amplexus can come with different fitness costs due to the fact that amplexus can occur for prolonged periods of time. For instance, a study found that when a male amphibian is grasping and holding onto a female amphibian, this can lead to the impairment of the female's ability to move or to feed. After conducting experiments, researchers confirmed that amplexus does decrease a female's locomotor performance (e.g. swimming, walking) as well as decrease the feeding rates of females engaged in amplexus. With regards to the cost of a male engaged in amplexus, male amphibians have been found to not feed at all during amplexus.