Stream‐dwelling copepods: Their life history and ecological significance1

Abstract

The stream-dwelling harpacticoid copepod Bryocamptus zschokkei was reared in the laboratory at 3.5", lo", 15", 18", and 20°C with naturally conditioned leaf disks as a food source. Egg and naupliar development rates were fastest at 18°C.A complete life table experiment was conducted at 18°C. Females were longer-lived than other copepods and produced eggs continuously until death. The intrinsic rate of natural increase (r) and the net reproductive rate (R,) were found to be lower than those of most copepods. Reproduction is probably continuous throughout the year in the stream, since animals reproduced in the laboratory at the extreme temperatures experienced by the natural population. Since most copepods reproduce seasonally, the annual intrinsic rate of increase of B. zschokkei may be comparable to those of other copepods.

Meiofaunal communities associated with bryophytes and gravels in shaded and unshaded alpine streams in New Zealand

“…Similarly, Rundle & Hildrew (1990) found mean annual temperature explained the between-site distribution of separate microinvertebrate groups and species. Contrary to the present study, however, harpacticoid copepods were usually restricted to warmer waters in their study, and indeed development times for harpacticoids decrease with increasing temperature (Sarvala 1979;O'Doherty 1985) suggesting a greater population turn-over at the warmer, shaded site. The enhanced copepod densities at the colder site reflected its open catchment and higher periphyton biomass accrual (Suren 1990), which these animals presumably use as food (Chapman & Lewis 1976).…”

“…Unlike most insects which leave the stream upon emergence, meiofaunal taxa such as copepods and nematodes have no emergent stages and consequently most carbon assimilated and not respired by these animals will remain in the stream. This has been illustrated in studies on secondary production of the harpactacoid copepod Bryocamptus zschokkei in a second-order North Carolina (U.S.A.) stream where 396 mg m^yr 1 was measured (O'Doherty 1985). This value is not much less than that of a dominant shredding plecoptera, Peltoperla maria (500 mg m" 2 yr 1 :0 'Hop et al 1984).…”

“…Although lotic meiofauna have been considered only occasionally, both their reported high densities (e.g., Williams & Hynes 1974;Zullini 1976;Shiozawa 1986) and high production values (O'Doherty 1985) imply that these animals contribute significantly to energy dynamics in streams. Unlike most insects which leave the stream upon emergence, meiofaunal taxa such as copepods and nematodes have no emergent stages and consequently most carbon assimilated and not respired by these animals will remain in the stream.…”

“…Overseas investigations of bryofauna have also concentrated on macroinvertebrates (e.g., Percival & Whitehead 1929, 1930Hynes 1961;Thorup & Lindegaard 1977;Maurer & Brusven 1983;Brusven et al 1990), but an overlooked aspect in these communities, however, is the occurrence of the meiofauna (O'Doherty 1985;Meyer et al 1988;Rundle & Hildrew 1990). Although lotic meiofaunal communities have occasionally been examined (e.g., Williams & Hynes 1974;Jones 1986;Shiozawa 1986;Williams 1989;Rundle & Hildrew 1990), only Cox (1988) has investigated the occurrence of meiofauna within aquatic bryophytes.…”

“…Although their importance to lentic ecosystems is well-known (e.g., Hutchinson 1967; Anderson & DeHenau 1980;Strayer & Likens 1986), their contribution to stream ecosystems is less understood. Most studies have concentrated on those animals in bare gravels (Rundle 1990;Rundle & Hildrew 1990), the hyporheic zone (e.g., Williams & Hynes 1974;Shiozawa 1986;Williams 1989), or leaf packs (O'Doherty 1985). Little work has been conducted on meiofauna in New Zealand where research has been restricted primarily to taxonomic and ecological investigations of lake faunas (e.g., Chapman & Lewis 1976;Forsyth & Lewis 1987).…”