Aquatic Insect Larvae Research Articles

Mass Occurrence of Penetrative Trace Fossils in Triassic Lake Deposits (Kyrgyzstan, Central Asia)

Bioturbation and the breakdown of organic detritus by burrowing macro-invertebrates are key factors for the energy flow in recent freshwater ecosystems due to the acceleration of nutrient cycling. According to the current state of knowledge, food webs similar to those of modern lakes were not operating until the Late Mesozoic, when a well-established freshwater infauna evolved. Here we describe laterally extended networks of irregularly branched burrows that constitute the most common ichnofossils in lacustrine deposits of the Middle to Late Triassic Madygen Formation, SW Kyrgyzstan. The shallow penetrative trace fossils give evidence that exploitation of lake-bottom sediments by benthic invertebrates was already in place in the Early Mesozoic. Architecture and size of the fossil burrows indicate deposit-feeding, worm-like trace makers of similar morphology and behavior to extant oligochaetes or aquatic insect larvae. Maximum intensity of bioturbation is recorded in mudstones of the transitional sublittoral to profundal lake zone, which usually represent the thermocline/chemocline level in modern stratified lakes. Taking into account the low-oxygen tolerance of many recent oligochaetes and insect larvae, we propose that ecospace utilization of deep-water lacustrine settings was originally impelled by two factors: the exploitation of additional food resources and the avoidance of predation by carnivorous animals from well-aerated lake zones. Spatial restriction of the described fossil traces could offer a basic approach to subdivide the Mermia ichnofacies.

Food spectra of the farm juveniles of the Chum Salmon Oncorhynchus keta (Salmoniformes, Salmonidae) in the Ryazanovka River (Southern Primor’e)

Qualitative data are presented on the diet of juvenile chum salmon Oncorhynchus keta released from the Ryazanovka experimental fish hatchery farm situated in the south of Primor’e Territory. The stomach fullness, frequency of occurrence of food items, their average weight value, and selectivity are estimated. Food spectra of chum salmon juveniles during downstream migration comprised representatives of 51 taxa of bottom freshwater invertebrates and terrestrial insects. The bulk of the diet consisted of larvae of aquatic insects—chironomids, other Diptera, and mayflies. Their diversity increased with the growth of fry. Fry of chum salmon had a wide spectrum of feeding preference, favorite food items were larvae and pupae of chironomids.

Short time-scale impacts of hydropeaking on benthic invertebrates in an Alpine stream (Trentino, Italy)

The impact of a single hydropeaking event was studied in the Alpine stream Noce Bianco. Four stations were selected, one upstream and three, respectively, at 0.25, 6, and 8 km downstream from a hydropower plant. We collected drifting invertebrates during a planned water release that increased the discharge 7-fold. At the onset of the hydropeaking wave the number of invertebrates lost from the riverbed per minute to the drift increased 9-fold at the first downstream station and the same effects propagated 8 km downstream. The drift was composed mainly of aquatic insect larvae (Chironomidae, Plecoptera, Ephemeroptera Baetidae, and Psychodidae, with Chironomidae as the most abundant taxon at all stations) and partly by larval and adult riparian insects, and by Oligochaeta, which were particularly abundant at the station 6 km downstream. We monitored drift for 30 min from the start of the water release: peaks in drifting invertebrates occurred within 5–10 min of the beginning of the hydropeaking wave, and most of the invertebrates were washed out within the first 15 min of the water release. The different timeframes were possibly due to habitat preferences (most of the taxa that increased in the drift at the arrival of the wave were associated with algae and organic debris, which were washed off quickly by the increase in discharge) and/or behavioral adaptations (other taxa initially resisted the shear stress and began to drift with a delay of 5–10 min). The temporal pattern and drift composition corresponded well with those reported in literature, and indicate that repeated high-flow events of similar magnitude cause considerable losses from benthic populations to drift.

Your worst enemy could be your best friend: predator contributions to invasion resistance and persistence of natives

Native predators are postulated to have an important role in biotic resistance of communities to invasion and community resilience. Effects of predators can be complex, and mechanisms by which predators affect invasion success and impact are understood for only a few well-studied communities. We tested experimentally whether a native predator limits an invasive species' success and impact on a native competitor for a community of aquatic insect larvae in water-filled containers. The native mosquito Aedes triseriatus alone had no significant effect on abundance of the invasive mosquito Aedes albopictus. The native predatory midge Corethrella appendiculata, at low or high density, significantly reduced A. albopictus abundance. This effect was not caused by trait-mediated oviposition avoidance of containers with predators, but instead was a density-mediated effect caused by predator-induced mortality. The presence of this predator significantly reduced survivorship of the native species, but high predator density also significantly increased development rate of the native species when the invader was present, consistent with predator-mediated release from interspecific competition with the invader. Thus, a native predator can indirectly benefit its native prey when a superior competitor invades. This shows the importance of native predators as a component of biodiversity for both biotic resistance to invasion and resilience of a community perturbed by successful invasion.

Mercury Bioaccumulation in a Stream Network

Mercury (Hg) contamination is common in stream and river ecosystems, but factors mediating Hg cycling in the flowing waters are much less understood than inthe lakes and wetlands. In this study, we examined the spatial patterns of methylmercury (MeHg) concentrations in the dominant groups of aquatic insect larvae across a network of streams (drainage area ranging from 0.5 to 150 km2) in northern California during summer baseflow conditions. We found that, with the exception of water striders, all invertebrate groups showed significant (p < 0.05) increases in MeHg concentrations with drainage area. The largest stream in our study watershed, the South Fork Eel River, had the highest aqueous MeHg concentration (unfiltered: 0.13-0.17 ng L(-1)) while most of the upstream tributaries had aqueous MeHg concentrations close to or below the established detection limits (0.02 ng L(-1)). A filamentous alga abundant in South Fork Eel River (Cladophora glomerata) had an exceptionally high fraction of total-Hg as MeHg (i.e., %MeHg from 50-100%). Since other potential hotspots of in-stream Hg methylation (e.g., surface sediment and deep pools) had %MeHg lower than or similar to surface water (approximately 14%), we hypothesize that Cladophora and possibly other autotrophs may serve as hotspots of in-stream MeHg production in this bedrock-dominated stream. Recent studies in other regions concluded that wetland abundance in the watershed is the predominant factor in governing Hg concentrations of stream biota. However, our results show that in the absence of wetlands, substantial spatial variation of Hg bioaccumulation can arise in stream networks due to the influence of in-stream processes.

Analysis of the diet of the tadpole shrimp, Triops sinensis, in paddy fields of Shouchang River watershed

The tadpole shrimp, Triops sinensis, was discovered in the paddy fields of the Shouchang River watershed. The gut contents of the shrimp from these field populations were analyzed in order to quantify their dietary patterns. Some species of tadpole shrimps were found to prey on mosquito larvae as well as uproot weeds. Mosquito larvae and weeds were seldom found in the paddy fields which the tadpole shrimp inhabited in the Shouchang River watershed. The results further showed that the larvae of these tadpole shrimp mainly feed on algae and rice lamina. The tadpole shrimp could feed on animal food including protozoa, nematodes, rotifers, crustaceans, and aquatic insect larvae, though the animal food was subsidiary.

Fear and loathing in the benthos: Responses of aquatic insect larvae to the pesticide imidacloprid in the presence of chemical signals of predation risk

The influence of interactions between pesticide exposure and perceived predation risk on the lethal and sub-lethal responses of two aquatic insects was investigated using the pesticide imidacloprid, and a combination of predator-release kairomones from trout and alarm substances from conspecifics. Laboratory experiments examined feeding and respiration rates of the caddisfly Sericostoma vittatum as well as the growth, emergence and respiration rates of the midge Chironomus riparius, exposed to sub-lethal concentrations of imidacloprid. The effects of the two stressors on burrowing behaviour of both species were also assessed. The results show significant effects of environmentally relevant concentrations of imidacloprid on all endpoints studied. Perceived predation risk also elicited sub-lethal effects in C. riparius and S. vittatum, the latter species being less responsive to predation cues. The effects of simultaneous exposure to both types of stressors were assessed using two different approaches: analysis of variance and conceptual models [concentration addition (CA) and independent action (IA)] normally used for the evaluation of contaminant mixture exposure. Both statistical approaches showed no significant interactions on responses in simultaneous exposures in the majority of parameters assessed with only a signification deviation from the reference CA and IA models being found for C. riparius respiration data contrary to the ANOVA results. Exposure to imidacloprid also compromised antipredator behavioural responses of both insect species, with potential negative consequences in terms of mortality from predation in the field. The results obtained demonstrate that natural and anthropogenic stressors can be treated within the same framework providing compatible data for modelling. For an improved interpretation of ecological effects it will be important to expand the mechanistic study of effects of combined exposure to pesticides and perceived predation risk by measuring different endpoints over a wider range of pesticide concentrations.

Elemental concentrations of aquatic insect larvae and attached algae on stone surfaces in an uncontaminated stream

Elemental concentrations of aquatic insect larvae and attached algae in an uncontaminated river were analyzed by instrumental neutron activation analysis (INAA) via the k0-standardization method. The aquatic insect larvae found were all intolerant species. No significant difference was observed in the elemental concentrations of aquatic insect larvae and attached algae along the river. Similar elemental concentrations were observed in the aquatic insect larvae collected at a fixed sampling point for two years. An analysis by the ratio-matching technique indicated a higher generic relationship between aquatic insect larvae and attached algae than river water.

Threatened fishes of the world: Procypris rabaudi (Tchang, 1930) (Cyprinidae)

Common name: Rock Carp. Local name: Yanli, Yanyuanba, Daili, Heili, Moli, (all in Chinese). Conservation status: Vulnerable (China red data book) (Yue and Chen 1998). Not evaluated yet on IUCN redlist. Identification: D. vi/19–21, A. iii/5–6, P. i/16, V. ii/8. Lateral scales 43–46. Body elongate, laterally compressed. Snout length smaller than postorbital length. Outer edge of dorsal fin truncated. Barbels 2 pairs (Chen 1998). Distribution: Endemic to the upper reaches of the Changjiang (Yangtze) River System (Chen 1998). Abundance: Population declined greatly since the 1970s (Probst et al. 2006). Close to extinction according to Cai et al. (2003). Habitat and ecology: Inhabits slow-flowing, deep-water streams and rivers with rocky substrata. Feeds on aquatic insect larvae, aquatic mollusks, small fishes and shrimp. Reproduction: Matures in 4 years; spawning occurs mainly between February and April, and also in autumn; 25,000 to 150,000 eggs per female; eggs adhesive (Cai et al. 2003; Probst et al. 2006). Threats: Overexploitation. Dams (e.g. Three Gorges Dam) have changed habitat. Wild larvae are harvested for aquaculture. Hybrids between P. rabaudi and other carps may escape or be released into the wild. Water pollution. Illegal fishing using electric shocking devices, explosives or poison. Conservation actions: Conservation reserves were established. Artificial propagation and rearing of larvae was successful at small scales (Probst et al. 2006). Some artificially propagated larvae have been released into the wild. An annual fishing ban (April to June) is in effect in the whole Changjiang River System since 2002. Conservation recommendations: Manage fishing activities strictly. Improve, standardize and promote the techniques for large-scale artificial propagation and larval rearing. Using pure lineages from different populations in captive propagation and releasing programs. Actions should be taken to improve water quality. Annual fishing ban should continue and the time should be extended. Environ Biol Fish (2009) 84:275–276 DOI 10.1007/s10641-008-9417-8

Are altitudinal limits of equatorial stream insects reflected in their respiratory performance?

Summary1. We measured respiration of the larvae of aquatic insects from streams in the Ecuadorian Andes in relation to oxygen saturation at 5, 8, 11, 14 and 17 °C. Polycentropus (Polycentropodidae), Lachlania (Oligoneuriidae), Anchytarsus (Ptilodactylidae) and Anacroneuria (Perlidae) represented genera absent from the highest altitudes, reaching 2720, 2930, 3120, 3450 m a.s.l., respectively, while Claudioperla (Gripopterygidae) and Anomalocosmoecus (Limnephilidae) occurred only above 2900 m a.s.l. Our purpose was to determine whether natural altitudinal limits were reflected in physiological critical points on respiration versus oxygen curves and by the effect of temperature on the ability to oxy‐regulate.2. For all six genera, respiration was affected by oxygen saturation and temperature. Respiration (mg O2 g−1 AFDM h−1) at 70% oxygen saturation (Michaelis–Menten fitted) varied from 2.6 to 7.6 between genera at 17 °C, and from 1.3 to 2.5 at 5 °C. Q10 values for this temperature interval ranged 1.5–2.9 (mean 2.3). The two “high‐altitude” genera had higher respiration rates at low temperature and oxygen saturation, and their respiration rate saturated at lower temperatures, than three of the four “low‐altitude” genera.3. The oxy‐regulatory capacity (critical points and initial decrease in respiration versus oxygen regressions) varied among genera and was affected by temperature. Lachlania, Claudioperla and Anomalocosmoecus had a higher ability to oxy‐regulate at low than at high temperatures, Anacroneuria was not clearly affected by temperature, while Polycentropus and Anchytarsus had a greater oxy‐regulatory capacity at high than at low temperature. These results indicate that the ability to oxy‐regulate is related to the temperature (altitude) at which species naturally occur.4. Upper altitudinal limits of the six genera were not reflected in their respiratory performance, because all genera had critical minima of temperature and oxygen saturation much lower than those occurring at the limits of their natural distribution. So, the altitudinal limit could not be attributed to absolute short‐term physiological tolerance of low temperature and oxygen concentration.5. Multiple regressions (based on respiration experiments and previously obtained relationships between water temperature, oxygen saturation and altitude) were used to predict how respiration rates should vary with altitude. At the upper limit of the four “low‐altitude” genera, respiration rates were 50–68% of those predicted at the centre of the range. With an arbitrary increase of 400 m above the actual limit, the effect of temperature would be a 13% decrease, and that of oxygen a 2% decrease, in respiration rate of Polycentropus, Lachlania and Anacroneuria, while respiration in Anchytarsus would be reduced by 5% by both factors.6. It seems that, while the immediate decrease in respiration with increased altitude is caused mainly by a decrease in temperature, the long‐term survival of a species at given altitudes might be more affected by oxygen saturation. Further quantitative and long‐term studies on survival and recruitment in populations and communities are needed to determine the importance of temperature and oxygen for altitudinal limits of aquatic insects.

Aspectos da história natural de Astyanax scabripinnis Jenyns (Teleostei, Characidae) em um riacho de floresta com araucária no sul do Brasil

Neste trabalho é descrita a estrutura populacional, os hábitos alimentares e a reprodução de Astyanax scabripinnis Jenyns, 1842, baseado em coletas realizadas mensalmente entre outubro de 1998 e setembro de 1999, em um riacho das cabeceiras do rio Iguaçu. A distribuição de freqüência por classe de comprimento revelou valores diferentes entre machos (5,4-6,7 cm) e fêmeas (6,1-8,1 cm). Foram encontradas diferenças significativas para os valores do fator de condição entre os sexos, o que pode implicar em diferentes taxas de crescimento. O período reprodutivo ocorreu entre outubro e março, como já descrito para outros caracídeos da mesma região. Fragmentos de insetos terrestres, restos de vegetais superiores e larvas de insetos aquáticos foram os principais itens consumidos, indicando uma pronunciada dependência da alimentação com os itens alóctones importados da vegetação ripária. Possíveis implicações das variações sazonais dos parâmetros físicos, químicos e hidrológicos sobre a história natural de A. scabripinnis são discutidas.

Hydraulic habitat use with respect to body size of aquatic insect larvae: Case of six species from a French Mediterranean type stream

Macroinvertebrates play a key role in lotic ecosystems, as fish prey and processors of organic material. Therefore, their hydraulic preferences have to be integrated in instream habitat models for ecological stream management. This study characterized physical habitat use in terms of shear velocity for the larvae of three Ephemeropteran ( Ephoron virgo, Oligoneuriella rhenana, and Serratella ignita), two Trichopteran ( Cheumatopsyche lepida and Hydropsyche exocellata) and one Dipteran species ( Blepharicera fasciata) in a Mediterranean stream at a relatively low water discharge. O. rhenana, C. lepida, H. exocellata, and B. fasciata larvae were mainly found in high shear velocity conditions, whereas E. virgo and S. ignita larvae were found in low shear velocity conditions. Knowing that habitat preferences should vary during ontogenesis (with respect to changes in biological requirements and/or morphological abilities to withstand high flow, for example), our second objective was to characterize differences in the hydraulic habitat use (in terms of shear velocity) for different size classes of these six species. Larvae of H. exocellata and B. fasciata mainly colonized high shear velocity conditions and numerous individuals of these species also used medium shear velocity conditions, independent of size class. The use of high shear velocity conditions increased with larval size for C. lepida and O. rhenana, whilst the use of low shear velocity conditions increased for larger larvae of E. virgo and S. ignita. Various hypotheses are proposed to explain these different strategies of habitat use during ontogenesis. We point out the lack of knowledge about physical habitat shifts during the larval growth of freshwater invertebrates. These results highlight the interest to consider the respective habitat requirements of different size classes of invertebrates in instream habitat models. Population bottlenecks should be overcome if hydraulic conditions are kept suitable for all size classes by stream managers.

Metal concentrations in Japanese medaka, mosquitofish and insect larvae living in uncontaminated rivers in Kumamoto, Japan

Elemental concentrations in Japanese medaka and mosquitofish collected from uncontaminated rivers in Kumamoto, Japan were analyzed by instrumental neutron activation analysis with k0 standardization method to know the background levels. A statistical analysis indicated the difference in metal concentrations among rivers and species. Background levels of elemental concentrations in some aquatic insect larvae were analyzed and metal concentrations were different among species, though they were collected at the same point. Enrichment factors of heavy metals in insect larvae were in the order of 103−104 suggesting effectiveness of insect larvae as bioindicator.

The occurrence of the trematodePlagiorchis murisin the wood mouseApodemus sylvaticusin North Yorkshire, UK

Wood mice Apodemus sylvaticus were trapped each September over a 13-year period, from 1993 to 2005, in a wooded area adjacent to Malham Tarn, Yorkshire, UK. Plagiorchis muris was found to be the dominant intestinal trematode and occurred in every year of sampling, with an overall prevalence of 16.9%. This appears to be the first record of P. muris in A. sylvaticus within the UK. The mean worm burden was 2.03 and the distribution of the parasite within mice was typically overdispersed. No difference in prevalence relative to host sex was evident although there was a higher prevalence of 21.9% in larger older mice compared with 9.1% in juveniles, which probably relates to a greater foraging activity in older mice. Annual prevalence values of P. muris infections varied significantly over the study period with higher prevalences being associated with years with a high spring/summer rainfall. The second intermediate hosts for P. muris include a variety of aquatic insect larvae and it is likely that the higher rainfall may result in the occurrence of temporary water bodies suitable for the development of insect larvae.

Trichomycetes from China and the description of three new Smittium species

Trichomycetes were recovered from the guts of aquatic insect larvae collected from a stream in the Qinling Mountains in western China. These collections included Smittium hecatei, known only from Spain, as well as Smittium simulii and Stachylina penetralis, which appear to be more widely distributed. Caudomyces japonicus, previously recorded only from Japan, also is reported from crane fly larvae (Antocha sp.) from China. We describe three new species, Smittium chinliense from a tipulid host, as well as Smittium naiadis and Smittium nodifixum, both from chironomid larvae. A probable new species of Gauthieromyces was collected in mayfly nymphs and is illustrated but not described here.

Trichomycetes from China and the description of three new Smittium species

Trichomycetes were recovered from the guts of aquatic insect larvae collected from a stream in the Qinling Mountains in western China. These collections included Smittium hecatei, known only from Spain, as well as Smittium simulii and Stachylina penetralis, which appear to be more widely distributed. Caudomyces japonicus, previously recorded only from Japan, also is reported from crane fly larvae (Antocha sp.) from China. We describe three new species, Smittium chinliense from a tipulid host, as well as Smittium naiadis and Smittium nodifixum, both from chironomid larvae. A probable new species of Gauthieromyces was collected in mayfly nymphs and is illustrated but not described here.

Trichomycete insect symbionts in Great Smoky Mountains National Park and vicinity

Collections of trichomycete symbionts of larval aquatic insects in Great Smoky Mountains National Park and vicinity in the southern Appalachian region of the USA resulted in finding many taxa of Harpellales, including an unusual new monotypic genus, Barbatospora ambicaudata in Simuliidae, and five new species in Thaumaleidae or Chironomidae, Harpellomyces montanus, Smittium lentaquaticum, Sm. minutisporum, Stachylina gravicaudata and St. stenospora. In addition a new species of Amoebidium (Amoebidiales), A. appalachense, attached to the anal tubules of bloodworms (Chironomidae) is described. Axenic cultures of three of the new taxa were obtained, plus Sm. culisetae. Fourteen identified species representing 13 genera of previously known Harpellales are recorded from Plecoptera, Ephemeroptera and Diptera, as well as a new Dipteran host record for an unidentified harpellid that was found in a Blephariceridae. Also identified were Paramoebidium corpulentum and many undetermined species of Paramoebidium (Amoebidiales) from four orders of aquatic insect larvae. The occurrence of an Enterobryus species in Diplopoda and another Eccrinales from an aquatic beetle is noted.

The predominance of polyunsaturated fatty acids in the butterfly Morpho peleides before and after metamorphosis

We hypothesized that the polyunsaturated fatty acids of the butterfly were probably derived from the diet and that there might be a great loss of body fat during metamorphosis. To substantiate these hypotheses, we analyzed the fatty acid composition and content of the diet, the larva, and the butterfly Morpho peleides. Both the diet and the tissues of the larva and butterfly had a high concentration of polyunsaturated fatty acids. In the diet, linolenic acid accounted for 19% and linoleic acid for 8% of total fatty acids. In the larva, almost 60% of the total fatty acids were polyunsaturated: linolenic acid predominated at 42% of total fatty acids, and linoleic acid was at 17%. In the butterfly, linolenic acid represented 36% and linoleic acid represented 11% of total fatty acids. The larva had a much higher total fatty acid content than the butterfly (20.2 vs. 6.9 mg). Our data indicate that the transformation from larva to butterfly during metamorphosis drastically decreased the total fatty acid content. There was bioenhancement of polyunsaturated fatty acids from the diet to the larva and butterfly. This polyunsaturation of membranes may have functional importance in providing membrane fluidity useful in flight.

Trichomycete insect symbionts in Great Smoky Mountains National Park and vicinity

Collections of trichomycete symbionts of larval aquatic insects in Great Smoky Mountains National Park and vicinity in the southern Appalachian region of the USA resulted in finding many taxa of Harpellales, including an unusual new monotypic genus, Barbatospora ambicaudata in Simuliidae, and five new species in Thaumaleidae or Chironomidae, Harpellomyces montanus, Smittium lentaquaticum, Sm. minutisporum, Stachylina gravicaudata and St. stenospora. In addition a new species of Amoebidium (Amoebidiales), A. appalachense, attached to the anal tubules of bloodworms (Chironomidae) is described. Axenic cultures of three of the new taxa were obtained, plus Sm. culisetae. Fourteen identified species representing 13 genera of previously known Harpellales are recorded from Plecoptera, Ephemeroptera and Diptera, as well as a new Dipteran host record for an unidentified harpellid that was found in a Blephariceridae. Also identified were Paramoebidium corpulentum and many undetermined species of Paramoebidium (Amoebidiales) from four orders of aquatic insect larvae. The occurrence of an Enterobryus species in Diplopoda and another Eccrinales from an aquatic beetle is noted. Amoebidiales,

Secondary production and trophic basis of sinopotamon teritisum in Heizhuchong Stream, Hanjiang Catchment

Macrozoobenthos community plays an important role in material cycle and energy flow in riverine ecosystem. During the period of June, 2003 to June 2004, an investigation on the life cycle and production of the dominant species of macrozoobenthos community in a second-order river of Hanjiang River Basin was carried out. From the upper to the lower reach of Heizhuchong stream, we chose six types of habitats to collect quantitative samples. Station 1 (S1) lied in the middle of the stream with big round rocks in the upper reach, station 2 (S2) was in the inner part of a weir with cobble substratum, station 3 (S3) in the middle of a peacefully flowing section with gravel-sand bottom, station 4 (S4) at the side of the riparian with aquatic macrophytes and snags, station 5 (S5) in the middle of the riffle, station 6 (S6) at the lower reach with a sewage outlet ca 100 meters uppstream. At each station, four quantitative samples were taken with a 167μm D-frame kick net or a Surber net, and the samples were sieved with a 167μm net, sorted in a porcelain dish with naked eye. The specimens were kept in 10% formalin for later processing. The life cycle of the S. teritisum Dai et al. population was analysed by the monthly size-class frequency distribution, the cohort and annual production were estimated by size frequency method. The results showed that S. teritisum completed one generation for nearly 4 years, the reproduction mainly occurred in from middle August to middle October, and most of the senescent individuals died in February. The abundance of the population varied greatly during the year, probably due to the relatively smaller sampling area compared with the strong activity of motion of S. teritisum. Whereas, the variation of the biomass followed the same pattern of the abundance. The a-bundance attained its peak in September with 35 ind/m2, and biomass reached its highest level in June at 41. 7 g/ m2. The estimated cohort production and cohort P/B ratio by size-frequency method were 605.2g/(m2·a) (wet wt) and 5. 5, respectively; the annual production and P/B ratio were 151. 3g/(m2·a) ( wet wt) and 1.4. The reason why the annual production of the animal in Heizhuchong Stream was the relatively higher was because of its high density. By analyzing its stomach content, the proportions of amorphous detritus, caridina, aquatic insect larvae, gastropods and vascular tissues were 45.4% , 10.9% , 35.6% , 5.7% , 8. 1% . Therefore, the contribution rates of the above types of food to production were 10.84% , 18.21% , 59.49% , 9.52% , and 1.94% , respectively.