Phillip John. Suter

Ecology of Temporary Streams—an Australian Perspective

Limnologists in Australia are well positioned to make significant contributions to temporary-stream ecology, a field that has received little attention worldwide. The great variation in physical and chemical conditions does not appear to depress macroinvertebrate species richness in some Australian temporary streams, and there is a considerable species overlap between permanent and temporary streams. The coincidence of zero flow with peak allochthonous organic input has important repercussions on transport of dissolved and particulate organic matter when flow resumes, and much is yet to be learnt about the biotic processing of this ‘pulse’ of material.

Deformities in chironomid larvae as indicators of pollution (pesticide) stress

Chironomid larvae (Chironomus spp.,Dicrotendipes conjunctus andProcladius paludicola) collected from Cox Creek and Aldgate Creek, South Australia, showed morphological abnormalities similar to those reported in other studies elsewhere in the world. The sediment of Cox Creek contained high concentrations of pesticides and there was a significant correlation between the occurrence of mouthpart and antennal deformities in larvae and the concentration of DDT and the herbicide, Dacthal®.Laboratory experiments were conducted using a culture ofChironomus sp. to determine whether or not a causal relationship existed between exposure to pesticides and the occurrence of deformities in larvae. Results showed a positive relationship between the concentration of DDT and the percentage of deformed mouthparts (menta). The results for the effect of DDT on antennae and those for the effect of Dachthal® were less clear, but generally showed a higher incidence of deformity for treatments compared with controls.To compare these results to a natural population (i.e. from an unpolluted area) the incidence of deformities was measured for larvae collected from Deep Creek Conservation Park, an area virtually free of pollution. The significance of this work is discussed with regard to its wider application as a useful environmental monitoring technique for freshwater systems.

Adult and larval associations of the alpine stonefly genus Riekoperla McLellan (Plecoptera : Gripopterygidae) using mitochondrial DNA

The current taxonomic understanding of the genus Riekoperla McLellan, 1971 (Gripopterygidae) is poor, with 15 of the 28 species and subspecies having unknown or uncertain larval associations. Sequences of a 657 bp fragment from the mitochondrial gene cytochrome c oxidase subunit 1 (CO1) were obtained from 122 specimens of 13 species collected throughout the alpine areas of New South Wales and Victoria, Australia. Of these, sequence data associated adults and larvae for the following 10 species: R. alpina McLellan, 1971, R. cf. intermedia, R. compressa Theischinger, 1985, R. hynesorum Theischinger, 1985, R. karki McLellan, 1971, R. montana Theischinger, 1985, R. reticulata (Kimmins, 1951), R. rugosa (Kimmins, 1951), R. trapeza Theischinger, 1985, and R. tuberculata McLellan, 1971. Adults of R. intermedia Theischinger, 1985, R. triloba triloba McLellan, 1971 and R. williamsi McLellan, 1971 were sequenced but no larvae were associated with them. The 13 species were reciprocally monophyletic and had minimum interspecific sequence divergences ranging from 7.2–19.5%, higher than the maximum intraspecific sequence divergences (0.6–5.8%). The combination of morphology and molecular data enabled rapid life stage association for alpine Riekoperla species and this method should be used more frequently for other environmentally significant aquatic insects.

The Effect of Mesh Size on the Interpretation of the Life History of Two Mayflies from South Australia

Using a Surber-type benthic sampler with a double net collecting system, the efficiency of nets having aperture sizes of 480 μm and 110 μm was assessed over a twelve month period in two streams in South Australia. Efficiency was defined as the percentage increase in yield (numbers) of animals obtained by use of 110 μm mesh instead of 480 μm mesh. The average annual increase in sampling efficiency of the fine net as compared with the coarse for mayfly nymphs was 412% and 235% for Spring Creek and Deep Creek respectively. The life cycles of two species of mayfly Tasmanocoenis tillyardi (Lestage) and Baetis soror Ulmer from Deep Creek are presented and the effect of the two mesh sizes on the interpretation of the life histories is discussed. Interpreted from the coarse mesh only, the life cycle of both species is bivoltine, each having one winter generation and one summer generation. Combining both fine and coarse net collections, the life cycle interpretation is distinctly different, illustrating the difficulties in drawing conclusions from coarse mesh samples. Not only is the number of generations misinterpreted in B. soror, but conclusions on the duration of the egg stage and length of each generation are also inaccurate for both species.

Post-Oviposition Development of Eggs of South Australian Mayflies

Eggs of Atalophlebia australis, Nousia inconspicua, N. fuscula and Baetis soror from South Australia were incubated under constant temperature conditions in the laboratory (Range 4–24°C). For each species the relationship between length of incubation period (Y) and incubation temperature (T) for the initial hatch (Hi) and mean egg hatch (Hx) was given by the equation Y = aT-b. The rate of development (V) was given by the equation V = bT + a. Photoperiod length had no effect on the incubation period.

A New Species of Caenidae from Australia: Tasmanocoenis arcuata sp.n. (Insecta, Ephemeroptera)

The nymphs, adults and eggs of a new species of the genus Tasmanocoenis Lestage (1930) from South Australia are described and illustrated, and a key to the adults and nymphs of known Tasmanocoenis species is provided.

Effects of a total solar eclipse on stream drift

Stream drift was recorded in the Acheron River, Victoria, on 23 October 1976. A total solar eclipse occurred at 1640-1643 h (Eastern Standard Time). No noticeable effect on the number or types of animals drifting was observed.

Decomposition of native leaf litter by aquatic hyphomycetes in an alpine stream

Despite the recognised significance of hyphomycetes in the degradation of leaf litter in streams, few studies have been carried out in alpine environments and none in Australian alpine streams. We hypothesised that the fungal communities responsible for leaf decomposition would change over immersion time, and would respond differently at different sites and on different types of vegetation. Leaf bags containing Epacris glacialis (F. Muell.), Eucalyptus pauciflora (Sieber ex. Spreng) and Eucalyptus delegatensis (R.T. Baker) were deployed at different sites in a stream in the Victorian Alpine National Park, south-eastern Australia. Leaf colonisation was delayed for 2 weeks and decay constants for E. pauciflora and E. delegatensis were 0.004–0.005 and 0.006 respectively. Maximum fungal biomass on leaves was similar to that in previous published studies, whereas sporulation rates were two or three orders of magnitude lower, indicating a reduced reproductive effort. Sporulation and DNA-based studies combined showed that fungal communities on the decomposing leaf material changed over time and exhibited significant preferences for leaf type and study site. We have shown that aquatic hyphomycetes can degrade physically tough leaves of Australian alpine plant species, potentially contributing to pathways for particulate carbon to enter alpine-stream food webs.

Platybaetis Gagadjuensis, a New Species from Northern Australia (Ephemeroptera : Baetidae)

A new species of Platybaetis is described from nymphal and subimago material collected from Kakadu National Park, Northern Territory. These dorso-ventrally flattened mayfly nymphs are very small and lack a number of characters expressed by the four described species from south east Asia. A subimago was reared and verified Miueller-Liebenau’s recognition that Platybaetis was closely related to a “Pseudocloeon” type adult.

Stoneflies (Plecoptera) of South Australia

Eight species of stoneflies were recorded from South Australian streams. All species have been previously described, but the first descriptions of the nymphs of Dinotoperla evansi and Riekoperla naso are given. Keys for the identification of male, female and nymphs of all species are given and some ecological information is also included.