Benthic Insects Research Articles

Feeding of Reportedly Parasitic Catfishes (Trichomycteridae and Cetopsidae) in the Rio Portuguesa Basin, Venezuela

The stomach contents of several Trichomycteridae and Cetopsidae were examined from wet-season collections in the Portuguesa River basin, Venezuela. Collections were from piedmont, high llanos, and low llanos habitats. Based on these and other published and unpublished observations the species were classified according to feeding habits. Among the trichomycterids, Trichomycterus kneri and T. meridae feed only on benthic insects, Vandellia feeds only on blood of fishes and other vertebrates, and Stegophilinae (Stegophilus, Homod'iaetus, and Ochmacanthus) are tentatively classified as scale eaters. The only cetopsid species taken contained terrestrial-winged insects. Cetopsids are also schooling piscivores, but none are confirmed to be parasites. Both cetopsids and trichomycterids bear the common name candiru or carnero, but their feeding habits do not indicate close phylogenetic relationship. Three parasitic species were found in the piedmont and four in the high Ilanos, but in the low llanos. where the greatest variety of fishes was found, only Ochmacanthus occurred. OF THE 13 FAMILIES AND ESTIMATED OVER 2500 SPECIES of South American freshwater catfishes, only Trichomycteridae and Cetopsidae are reported to include parasitic species (Gudger 1930, Eigenmann and Allen 1942, Kelley and Atz 1964, Roberts 1972), knowni collectively as candiru, or carnero. The two families were once considered to be closely related primarily because of this similar reputation, but recent taxonomic work has shown that the Trichomycteridae are more closely related to the Loricariidae and Callichthyidae (the armored catfishes) rather than to the Cetopsidae (Baskin 1972, Chardon 1968). The older literature contains many references to the habits of the candiru, but the actual species in question is often obscure, and the exact feeding habits of these catfish families have not been determined by systematic stomach-content analysis. The Trichomycteridae consists of about 30 genera and 136 species, divided into six subfamilies (Baskin 1972). Most are small, worm-like catfishes, characterized as having teeth on the external edges of the opercular bones, and lacking the pectoral and dorsal fin spines found in more typical catfishes. The Trichomycterinae are not considered to be parasitic, and are not included among the candiru; e.g. Eigenmann and Allen (1942) report Trichomycterus dispar feeding on molluscs, crustaceans, and fishes. The Vandelliinae and Stegophilinae contain the reported

Growth and Diets of Trout from Contrasting Environments in a Geothermally Heated Stream: The Firehole River of Yellowstone National Park

Differences in seasonal patterns of growth, length at age, and diet were evident between brown trout (Salmo trutta) residing in geothermally heated and unheated sections of the Firehole River. Maximum temperatures at the warmest station exceeded 28 C and averaged about 10.5 C higher than the unheated station throughout the year. Scale characteristics indicated that brown trout from the heated stations had two annual growth periods while those from the unheated station had one, relatively short, annual growth period. Brown trout from the heated stations were significantly longer at any particular age than those from the unheated station. Caddis flies were the numerically dominant food in the unheated water while trout at the heated station fed most extensively on dipterans, molluscs, and mayflies. Additionally, trout in the unheated water fed almost entirely on immature benthic insects while those at the heated station fed heavily on emerging insects and exhibited considerably greater numbers of organisms per stomach. Rainbow trout (Salmo gairdneri), numerous only at the heated station, had seasonal growth pattern, length at age, and diet similar to those of brown trout at this station.

Insecticides, polychlorinated biphenyls and metals in african lake ecosystems. II. Lake Mcllwaine, Rhodesia

In an effort to examine biological accumulation of pollutants in an African lake ecosystem samples of water, bottom sediment, oligochaetes, benthic insects, three species of fish, and a fish eating bird were analysed for several insecticides, PCB's, and metals. Actual concentrations as well as the expected increase in the food chain are discussed.

Insecticides, polychlorinated biphenyls and metals in african lake ecosystems. III. Lake Nakuru, Kenya

In an effort to examine biological accumulation of pollutants in an African lake ecosystem samples of water, bottom sediment, oligochaetes, benthic insects, three species of fish, and a fish eating bird were analysed for several insecticides, PCB's, and metals. Actual concentrations as well as the expected increase in the food chain are discussed.

Some little-known Benthic Insect Taxa from a Northern New Zealand River and its Tributaries

Figures and notes on occurrence are given for 17 taxa from 12 families of iare or little-known insects collected from the \Vaitakere River and Cascade Stream, in the Il1aitakere Ranges, northern New Zealand. These include Odonata (Corduliidae), Hemiptera (Mesoveliidae) , Coleoptera (Staphylinidae, Dytiscidae, Hydraenidae, Helodidae, Ptilodactylidae, Elmidae) , Diptera (Tipulidae : Limoniini and Hexatomini, Ceratopogonidae, Sciomyzidae) , and Trichoptera (Psychomiidae : Ecnominae) . In addition, a list is presented of all species collected during the study.

Age, Growth, Maturity, and Seasonal Food Habits of Round Whitefish, Prosopium cylindraceum, in Lake Michigan near Ludington, Michigan

Round whitefish were studied in 1972 and 1974 as a portion of a broad ecological study of a near-shore area of eastern Lake Michigan near Ludington, Michigan. Of 690 fish taken by gill nets, Age III fish were predominant in 1972 and Age IV in 1974. Male and female fish were taken in approximately equal numbers. About 50% of Age II and 90% of Age III fish were mature. Comparative growth and length-weight data indicated that the round whitefish were larger at any given age than those from previously reported populations. On a seasonal basis, benthic insect larvae and small mollusks were the organisms most frequently ingested.

Trophic Relations of Acroneuria (Calineuria) californica (plecoptera: Perlidae) in a Sierra Foothill Stream 1

Feeding by Acroneuria (Calineuria) californica Banks was studied from May 1973 through April 1974 in a single riffle of Squirrel Creek, Nevada Co., CA. The stonefly nymphs contained an avg. 5.18 prey items each, with monthly means ranging from 1.66–19.19 prey/stonefiy. Gut content diversity was correlated significantly with benthic diversity. The most important food items were members of the Diptera, Trichoptera, and Ephemeroptera, generally accounting for more than 70% of the stonefly gut contents. Consumption by the A. californica population increased from May through October. Population consumption, decreased in November with decimation of the benthic community by washouts, remained low through April. Consumption of benthic insects by A. californica nymphs has a significant impact on the dynamics of its benthic prey. It is suggested that large populations of A. californica nymphs can reduce trout production in the field as well as in the laboratory.

Factors Restricting the Range of Glyptotendipes paripes Edwards (Diptera: Chironomidae) in a Bog Lake

Glyptotendipes paripes Edwards, a midge that often occurs in sufficiently high densities to be a nuisance during emergence periods, has (perhaps largely for this reason) attracted an unusual amount of attention. Accounts, concerned largely with control measures, include the work of Nielsen (1962), Patterson (1964), von Windeguth (1964) and Crossman (1966). From this work it is clear that G. paripes often occurs in lakes with a peaty bottom. There are also indications that within the lake mud distribution of the larvae may be influenced by substrate particle size (Provost & Branch 1959) as is often the case in freshwater lakes and streams (Cummins & Lauff 1969; McLachlan 1969). In some cases, at least, G.paripes larvae prefer the larger substrate particles (Marks & Henderson 1970). A small humic lake on Sphagnum moor in England provided a field situation which appeared to be particularly suitable for the study of factors influencing the distribution of mud-dwelling animals. Some of the important characteristics of this lake, including aspects of the distribution of Glyptotendipes paripes and other benthic insect larvae, are considered by McLachlan & McLachlan (1975). They demonstrated that a strong correlation exists between the number of G. paripes larvae and the proportion of coarse fragments in the sediment layer (illustrated in Fig. l(A),a). This correlation results in the fauna being restricted to one shore of the lake (Fig. 1(B)) where particle size sorting has deposited the heavier (larger) fragments following their erosion from the exposed coast. This distribution is striking in view of the small size of the lake (about 0-5 km2), its relatively uniform water depth (about 1 m throughout) and the fact that the lake bottom is composed entirely of peat (Fig 1(A),b). In order to investigate further this relationship between G. paripes and the substrate, a more detailed mud sampling programme was carried out within the area occupied by the larvae. This work was coupled with complementary field and laboratory experiments designed to reveal causal relationships between factors in the environment and the chironomid population.

The Distributional Ecology and Diversity of Benthic Insects in Cement Creek, Colorado

A bstract. Distributional patterns and species diversity of benthic insects in an alpine stream in Gunnison County, Colorado, USA were investigated on several levels of spatial scale, from faunal replacement over 1,000 vertical m to microdistribuLtion within the stony substratum. Ecotones including zonation in terrestrial vegetation and in trout distribution did not appear to affect faunal replacement. Competition among congeners accounted for 7-30% of the cases, while in the majority of species, faunal replacement appeared to be associated with gradual changes in the physical gradient. Trout zonation may affect total numbers of insects, however, as the trotut-free headwaters had two to six times higher insect densities. Microdistribution was investigated by measures of species and substratunm patterning in a series of microhabitats (0.093 mi) at a series of sites (separated by 75-150 vertical m), and by field colonization experiments with various substratum choices. I hypothesize that increased suibstratum complexity leads to greater species richness based on several lines of evidence: (I ) different species showed different substratum preferences, (2) colonization of mixed stubstrata generally resulted in greater mean species richness than did colonization of a single substr-atum type, and (3 ) both species diversity and substratum complexity were greatest at the within-microhabitat level. However, substratum composition showed little variation along the elevational gradient and did not appear to be a cause of faunal replacement. The several scales of investigation were complementary, as congeners exhibiting sharp mutuLal exclusion in vertical distribution had similar microhabitat preferences, while othercongeners showed less exclusion and differed in microhabitat preferences. Most of species diversity as measured by H' was found within habitats rather than between habitats while species richness depended equally upon within-habitat variation (owing to rare species) and between-habitat variation (owing to faunal replacement).

A community Analysis of the Benthic Insect Fauna of an Abandoned Beaver Pond

Over the past decade the importance of allochthonous organic matter as an energy source in aquatic system has received increasing attention. Data are available for streams (Nelson & Scott 1962; Minshall 1967; Kaushik & Hynes 1971), lakes (Wetzel et al. 1972) and rivers (Berrie 1972), but ponds have received little attention. Allochthonous detritus type (Woodall & Wallace 1972), distribution (Egglishaw 1964) and possibly particle size (Cummins & Lauff 1969) have been shown to influence the distribution and hence faunal composition of stream insect communities. Beaver ponds are a characteristic feature of the forested foothill areas of the Rocky Mountains of North America. They are formed by the damming of streams, and at time of formation there is an input of allochthonous material into the pond equal to the standing crop of vegetation plus leaf litter on the flooded area. Furthermore, after being abandoned by beavers, seral succession proceeds and hydrophytes such as Salix sp. colonize the pond margins and ensure a continued input of plant detritus. The objectives of this study were to examine the feeding biology, distribution relative to substrate type and adult phenology of the benthic insect communities associated with a shallow abandoned beaver pond and to assess the importance of allochthonous detritus as a food source for these insects. The insect fauna of such ponds (Appendix 1) differs markedly from that of streams, rivers and lakes (see Hynes 1970), larvae of the Diptera, especially Tipulidae, are the major faunal component: the Chironomidae are poorly represented. Unfortunately, the larval systematics of the Diptera are poorly known and this creates problems.

Recovery of the mud substrate and its associated fauna following a dry phase in a tropical lake1

Lake Chilwa was dry for over a year. Following heavy rains, refilling was complete within 5 months, and, after 6 weeks, benthic insect populations of up to 3,500 mg m−2 were recorded. This pioneer population, mainly larvae of Chironomus transvaalensis Kieffer, disappeared 12 weeks later leaving a scanty benthic fauna resembling that of the drying phase.Isolated populations of C. transvaalensis persisted in some peripheral sites. The disappearance of fauna followed precipitation of fine grained material derived from erosion at the advancing shoreline during filling, which lowered the resistance of the larvae to major salinity variations and subsequent seasonal events. Persistence of larvae at the periphery was associated with plant debris which seemed to counteract the effects of the change in the mud.

Lake Opeongo: Effects of Exploitation and Introductions on the Salmonid Community

Lake Opeongo, a 58.6 km2 lake in the highlands of Algonquin Park, Ontario, has been under study since 1936. Due to little human development of the area, environmental conditions have been stable but because of its geological setting and location the lake waters are relatively unproductive.The smallmouth bass introduced in 1928 has had no apparent major impact on the salmonid community but has served to buffer fishing pressure on the lake trout. The cisco introduction in 1948 resulted in faster growing, better conditioned, and more fecund lake trout but has also contributed to their later maturity. Weight production of trout increased and in recent years stronger classes have apparently resulted from the improvement in fecundity. Declines in the perch and benthic insects and a decrease in growth rate of certain fishes since the mid-1950s are apparently related to the cisco introduction.Harvest of lake trout by the sport fishery has varied from 630 to 2700 fish/year representing a long term yield of 0.33 kilos/ha. Mean total mortality rate is 50%/year and exploitation has served to double the mortality rate after the trout have entered the fishery. Year-class production is correlated with spawning escapement and exploitation has limited recruitment to the trout population.

Benthic Insect Communities of Streams in Stora Sjöfallet National Park, Swedish Lapland

AbstractBenthic animal communities in streams with varying environmental conditions in a national park in northern Swedish Lapland were analysed. Dominant taxa were Ephemeroptera, Plecoptera, Trichoptera and Diptera Simuliidae. Northeasterly or very widely spread species make up the fauna. Intrariverine distribution patterns were found to differ between taxa, and great variations of standing crop values between adjacent sampling sites were the rule. Day-to-day fluctuations of drift rate were unsynchronized between taxa. Some ecological properties of Brachyptera risi (Plec.) are discussed. Some lake shores and streams affected by hydroelectric exploitation appeared virtually devoid of macroscopic animals.

Feeding of Rainbow Trout (Salmo gairdneri) in Relation to Abundance of Drifting Invertebrates in a Mountain Stream

Hatchery-reared rainbow trout, deprived of food for 48 or 96 hr and released in a mountain stream for 5- or 10-hr periods, consumed aerial invertebrates in numbers loosely associated with their seasonal and hourly abundance in the drift. The same was generally true for benthic insects, except that on several days feeding was much poorer relative to drift from 3:00 AM to 8:00 AM than at other times of day.In September and October tests, aerial forms were abundant during daylight, and benthic forms abundant at night, enabling trout to feed 24 hr a day. Day and night feeding in September were roughly equal in importance, but in October more food was taken during the day. Aerial invertebrates were so rare in December that benthic insects were the most important prey day and night. However, even benthics were not numerous enough to provide good feeding.

Oxygen requirements of benthic insects as determined by manometric and polarographic techniques

Determinations of oxygen consumption at or near 20°C were made on immature, aquatic insects belonging to the orders Diptera, Ephemeroptera, Odonata, Plecoptera, and Trichoptera by manometric and electrochemical methods. The plecopteran Pteronarcys pictetii and the dipteran Tipula abdominalis had the lowest respiratory rates; all the Ephemeroptera had high rates. Trichopteran Pycnopsyche guttifer and Macronemum zebratum, odonatan Hetaerina sp. and Calopteryx sp., dipteran Atherix variegata, and plecopteran Paragnetina media had intermediate rates. The respiratory rates generally agree with the usual index-organism classification of these insects. Those with high rates have been found in clean water zones, while those with moderate and low rates, in recovery zones. The correlation was 0.8920 when the same 30 insects were examined by the Warburg and electrochemical, flow-through methods. The latter method is described.

Phyco-Periphyton in an Oligotrophic Lake

Much limnological literature over the last century has been concerned with problems of primary productivity. In lentic waters large enough in size to promote a harvestable standing crop of fish, there exists numerous biocoenoses which have not been sufficiently considered. All possible productive biocoenoses should be investigated to determine their effect on the entire lentic community. An appraisal of the lentic biopotential which may prove of major importance in the problem of fish population dynamics is considered in this research. Of major interest was the quantitative analyses of the nutrients and the algal components in the littoral zone periphyton. The study was based upon the hypothesis that most lakes throughout the world are greatly influenced by the littoral area where fish spawn and where the largest standing crop of benthic insects is found. Two terms used should be defined for clarification. First, phyco-periphyton is the assemblage of algae growing on or in close proximity to submerged plant materials. Second, productivity is the primary production of phyco-periphyton developed in a space-time continuum, and is recorded in numbers of cells per liter as washed from a substratum which can be converted to the number per em.2 of leaf surface or stated as air-dry weight. The majority of studies on phyco-periphyton has been floristic in nature concerned with descriptive terminology and some with ecology. Only a few have attempted to quantify the data. Fassett (1951) stressed the importance of higher aquatic plants in supporting algae and small animals which are direct or indirect nourishment for fish. Yet he made only broad generalizations with few quantitative data on the pure dynamics of the littoral zone and the algal biocoenosis to support his conclusions. Fritch (1931) noted the importance of the littoral production of periphyton but did not demonstrate it quantitatively. In 1939 Roll attempted to clarify periphyton terminology and to establish consistency in its use. The term periphyton described the assemblage of organisms growing on all living and nonliving matter in the water. He included a complete citation of all previous studies concerned with phytosociology and described the limnological terminology used in Germany. He did not quantify littoral production of the algae. The best basic source of periphyton information was published by Young (1945) in which he commented about the possible transference of algae from the periphyton to the plankton. Roll (1939) reported Hentschell in 1917 to be the first to use glass slides for collection of periphyton in a qualitative manner and this technique has been used frequently since. Castenholz (1960), Grezenda and Bremmer (1960), Anita et al. (1963), and Sladecek and Sladeckova (1963) have advanced quantitative work using artificial barren surfaces varying from a small glass slide to a large volume plastic sphere. The artificial barren surface had been used by Patrick (1954), Whitford and Schumacher (1963), and Hohn and Hellerman (1963) to collect diatoms primarily for taxonomic and ecological purposes.