FNZ 31 - Talitridae (Crustacea: Amphipoda) - Introduction
Duncan, KW 1994. Talitridae (Crustacea: Amphipoda). Fauna of New Zealand 31, 128 pages.
( ISSN 0111-5383 (print), ; no. 31. ISBN 0-478-04533-6 (print), ). Published 07 Oct 1994
The terrestrial Talitridae ('talitrids' or 'landhoppers') are members of the cryptozoa (nocturnally active, terrestrial invertebrates) of grasslands, scrubland, and forests in New Zealand and other remnants of Gondwana with the exception of South America. However, they are invading other places, including South America, Europe, and North America, and there is one introduced species in New Zealand.
Within New Zealand their distribution is interesting in that genera are usually sympatric whereas species within genera are allopatric. Furthermore, most species show a very limited latitudinal range spanning only a few degrees.
Amplexis, the carrying of the female by the male during copulation, which is such a notable feature of talitrids, is not seen in most New Zealand species. Instead the female lies prone during copulation, and the male mounts her (or males, since multiple copulation has been observed). The eggs are relatively large, and there are only a small number per brood. The mother broods the clutch under her thorax; the eggs are held in this marsupium by broodplates. In this position the eggs are immersed in the fluid that surrounds the external gills. While brooding, the mother exhibits maternal care: she turns the eggs in the brood, and rejects any that are unfertilised or addled.
Hatchlings closely resemble the adults except for their lack of secondary sexual characteristics and their simpler spination. Development is direct. During juvenile and adult life individuals undergo a number of ecdyses, increasing their body size and the complexity of their spination with each moult. Breeding in New Zealand conditions seems to cease in winter, and occurs continuously throughout the rest of the year. In some species, however, there are breeding peaks in early spring and late summer.
Landhoppers live in litter, under logs and rocks, in unlined burrows in the soil that they construct themselves, or in the burrows of other species. They feed on dead plant material at night, especially when conditions are warm and humid, and they may climb tree trunks or grass stems to reach the canopy in order to browse. They are so abundant in forests that they are probably one of the major agents for the comminution of dead plant material. Other than this, they have no economic importance. They seem to thrive in cooler climates, though most species have a relatively narrow latitudinal range. Their lifespan seems to be annual. They live in all kinds of native terrestrial plant communities, but some species are restricted to soils of high conductivity, such as occur under coastal pohutukawa (Metrosideros excelsa) forest. Some species occur in rough pasture and waste grassland, while others have successfully invaded exotic pine plantations, although in much lower numbers than in native forests.