Deep-sea gigantism

Proposed explanations for this type of gigantism include necessary adaptation to colder temperature, food scarcity, reduced predation pressure and increased dissolved oxygen concentrations in the deep sea.

In marine crustaceans, the trend of increasing size with depth has been observed in mysids, euphausiids, decapods, isopods and amphipods.

Deep-sea gigantism is not generally observed in the meiofauna (organisms that pass through a 1 mm (0.039 in) mesh), which actually exhibit the reverse trend of decreasing size with depth.

[11] Food scarcity at depths greater than 400 m is also thought to be a factor, since larger body size can improve ability to forage for widely scattered resources.

A 1999 study of benthic amphipod crustaceans found that maximum potential organism size directly correlates with increased dissolved oxygen levels of deeper waters.

[17] The proposed theory behind this trend is that deep-sea gigantism could be an adaptive trait to combat asphyxiation in ocean waters.