User:Andrewsaillant/Squat lobster

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Fecundity or number of eggs increases with smaller sized eggs and increasing body size of the parent leads to increasing incubation time and therefore increase egg volume.

In the late Oligocene and through the early Miocene, squat lobsters underwent a period of rapid diversification.

Benthic Aggregation
Squat lobster aggregation is theorized to be proportional to the amount of available organic particulate carbon reaching the seafloor. As such, many species of benthic squat lobsters aggregate into groups of very high population density around a number of different types of highly productive areas of the deep sea, like hydrothermal vents, cold seeps, sites of food falls like whale falls or wood falls, and shipwrecks. Squat lobsters seem to aggregate in these areas because they are associated with the fauna that thrives in them, like Bathymodiolus mussels and vestimentiferan tubeworms, but they are also attracted to the three-dimensional structures found in them. Burrows, crevices, or debris from shipwrecks are suggested to serves as shelter against predators, as well as food accumulation sites. A variety of squat lobster called Emmunida picta were found to almost exclusively reside on some type of structure, mostly Lophelia pertusa.

In March 2022 it was reported that a squat lobster, possibly from the genus Munidopsis, had been filmed on the wreck of the Endurance, which sank in 1915 in the Antarctic. This was the first record of a living squat lobster in the Weddell Sea.

Ontogenetic Migrations and Pelagic Aggregation
Pleuroncodes planipes perform vertical migration into the water column from the benthos at different stages in development, an example of ontogenetic migration. Early larval stages are found mostly near the sea surface, but older larval and juvenile stages have a wide vertical distribution through the water column, and adults become almost purely benthic, with only a few vertical migrations in their remaining lifetime. In these migrations, they will form large swarms (up to 200 m vertically, and up to 10 km horizontally) in which they rely the selective tidal stream for feeding.

Munida gregaria form aggregations in warm summer waters of the Pacific Ocean associated with river plume fronts, headland fronts, and shallow internal waves. Density of these aggregations are, on average, 2700 individuals per cubic meter. M. gregaria are able to aggregate in the pelagic region due to a number of unique features as compared to benthic squat lobsters, including fast swimming speeds, reduced density, reduced sinking rates as a result of greater morphological surface area, and optimized aerobic metabolism. M. gregaria also exhibit ontogenetic migration through larvae accumulation in highly productive nearshore waters, which then move toward the mid-continental shelf as they mature, and move completely offshore around full maturation.

Claw Position Behavior
In a resting posture, squat lobsters rest their claws on the substrate in front of them. E. picta were observed most frequently in all conditions with their claws extended into the water column, perpendicular to the substrate. In the case of this study, the behavior was thought to be an avoidance response to the surveillance submersible, hence why this behavior was so often observed. In general, it is thought that this behavior may be a mechanism to increase the perceived size of the squat lobster as an aggressive or perhaps illusory display to ward off predators, as well as an active "fishing" strategy to catch prey.

Aggression and Agonistic Behavior
Squat lobsters are generally unaggressive toward each other, but instances can occur in particular scenarios. Individuals among dense populations will make decisions about whether to hunt for food or engage in deposit feeding on the basis of minimizing aggressive interactions. In general, squat lobsters exhibit no lasting dominance hierarchies, nor do they engage in territorialist behavior. When aggressive displays do occur, as a result of competition for mates or food, the aggressive behavior is ignored 70% of the time, met with submission 20% of the time, and met with reciprocal aggression 10% of the time. A 2001 study examined the effects of serotonergic and octopaminergic systems in Munida quadrispina, and found that injected serotonin elicits aggressive postures and behaviors, including increased likelihood and intensity of aggressive reactions to real or artificial squat lobsters, while injected octopamine reduced instances of aggressive behavior, including increasing the likelihood of escape responses.

Breeding
Squat lobsters, in particular Cervimunida johni and Pleuroncodes monodon, are known to mate during the intermolt period. Squat lobster mating was shown to be unrelated to the female molt period, unlike many other crustacean species; instead, mating occurs when most females are found to be ovigerous and there is no or only minor molting activity, i.e the intermolt period. These species of squat lobster also displayed very short interbrood intervals, or time between mating, generally not longer than a few days.