(Subject matter of experiments and observations of water animals in school aquarium IX. (Nektonic water bugs)
Abstract
Rearing of water bugs in school aquaria is described in this contribution. The following families are presented:
1) Notonectidae are commonly called backswimmers because they swim upside down. They are predators and paddle with their long, hair-fringed hind legs and attack prey such as insect water larvae, tadpoles and small fish. They can inflict a painful "bite" on a human being. They inhabit still freshwater, e.g., lakes, ponds, marshes, and are sometimes found in garden ponds and even swimming pools. They can fly well and so can disperse easily to new habitats. The common backswimmer, Notonecta glauca, up to 16 mm long, is widespread in our waters.
2) Pleidae, the pygmy backswimmers, are only 2-3 mm long, and like backswimmers they are in an upside-down position when swimming. Both sexes are able to stridulate. Pygmy backswimmers inhabit lacustrine ecosystems, They are predatory, hunting other tiny invertebrates e.g. mosquito larvae. Similar to the true backswimmers, pygmy backswimmers carry an air reserve to them which is periodically replenished by a dash on the water's surface. This air is contained in a felt-like cushion on the underside. Thus (similar to backswimers), the belly has a higher buoyancy, resulting in the animal turning upside down as soon as it lets loose from the substrate.
3) Naucoridae, known as the creeping water bugs and saucer bugs, inhabit a wide range of freshwater habitats, ranging from still waters like ponds, to flowing rivers and even torrential streams. Predaceous saucer bug Ilyocoris cimicoides, up to 15 mm long, is a common species. It swim in normal position, i.e., right side up.
4) Corixidae or water boatmen have a long flattened body ranging from
2.5 to 15 mm long. Corixidae dwell in slow rivers and ponds, as well as some household pools. They swim right side up. Corixidae are mostly non-predatory, feeding on aquatic plants and algae. Corixids are able to leap out of the water into the air and take flight.
5) The river bug Aphelocheirus aestivalis belongs to the family Aphelocheiridae. Its flattened body is circular up to 10 mm long. This bentic aquatic insect relies totally on an incompressible physical gill to exchange respiratory gases with water. The gill is called a 'plastron'. It consists of a stationary layer of air held in place on the body surface by millions of tiny hairs that support a permanent air-water interface, so that the insect never has to renew the gas at the water's surface. Members of above-mentioned families are suitable to rearing in cold-water school aquaria, and their breeding is simple. Some experiments and observations in an aquarium, inspired by cited literature sources, are presented in this contribution.