Odonata Nymphs Research Articles

The role of amphibian prey in the diet and growth of giant water bug nymphs in Japanese rice fields

AbstractPredatory insects that depend upon particular prey animals are commonly regulated by the prey animal's abundance. Nymphs of the giant water bug Kirkaldyia (=Lethocerus) deyrolli (Heteroptera: Belostomatidae) are predators regarded as specialists in feeding on tadpoles. We studied the ontogenetic diet shift of aquatic nymphs by quantifying instar abundance and by analyzing captured prey and prey relative abundance during the period of rice irrigation in three localities. We also evaluated the contribution of major prey items (tadpoles, frogs, and Odonata nymphs) on specific growth rates of each nymphal stage in a rearing experiment. First to third‐instar nymphs of K. deyrolli fed mainly on tadpoles, regardless of differences in prey availability. Nymphs of subsequent fourth and fifth instar stages shifted from tadpoles to other prey animals within each rice field. A rearing experiment demonstrated that giant water bug nymphs provided with tadpoles had greater specific growth rates at all nymphal stages, except for the final stage, than nymphs fed other prey (frogs and Odonata nymphs). The emergence of young K. deyrolli nymphs seemed to coincide with the period during which tadpoles became abundant in the rice fields. Consumption of tadpoles seems important to allow the nymph to complete its larval development in an unstable temporary habitat.

Raptorial Legs and Claws Are Not Influenced by Food Condition in Nymphal Stages of <I>Lethocerus deyrolli</I> (Heteroptera: Belostomatidae)

Previous studies have suggested that the developmental pattern of insect body parts is influenced by food conditions during the nymphal stages. In this study, we compared the developmental patterns of five body parts (body length, fore-femur length, mid-femur length, hind-femur length, and angle of claw) in the predatory insect Lethocerus deyrolli Vuillefroy fed three diets (tadpoles, Odonata nymphs, and tadpole–Odonata nymph mixture) during the nymphal stages. Significant age by sex interactions were detected in body length, fore-femur length, mid-femur length, and hind-femur length, indicating developmental patterns of these traits varied between sexes. Significant age by food interactions were detected in body length and hind-femur length and were marginally significant in mid-femur length, showing developmental patterns of these traits varied among food types. None of the interactions were significant in angle of the claw. A predation experiment was performed using double-claw nymphs as a control and one-claw nymphs (adult type) as a treatment. Double-claw nymphs successfully caught both large and small tadpoles, whereas one-claw nymphs caught small tadpoles more frequently than large tadpoles. Our results suggest that the claw development, which is very likely related to predatory function, may be less affected by nutritional conditions, and that double claws during nymphal stages may be indispensable to increased predation success.

Experimental Assessment of Age‐0 Largemouth Bass and Juvenile Bluegill Competition in a Small Impoundment in Virginia

AbstractPrevious research has found that early ontogenetic stages of largemouth bass Micropterus salmoides and bluegills Lepomis macrochirus may compete for food resources in small impoundments in northern‐latitudes. We experimentally assessed whether competition also might occur in a southern‐latitude system by stocking fish allopatrically and sympatrically in 1.0‐m3 cages within a small impoundment in Virginia and monitoring fish growth and diets. Although growth was not significantly different between bluegills stocked with and without largemouth bass, largemouth bass grew significantly larger when stocked alone than when stocked with bluegills. Although bluegills maintained similar diets in terms of sizes, numbers, and types of items consumed, largemouth bass stocked alone consumed fewer but larger items than those stocked with bluegills. Further, largemouth bass consumed higher volumetric proportions of Diptera larvae and Odonata nymphs when stocked alone than when stocked with bluegills. Of these two items, only Diptera larvae constituted a large portion of bluegill diets. Competition between largemouth bass and bluegills apparently occurs in both southern‐ and northern‐latitude small impoundments. Competition with bluegills may result in a competitive juvenile bottleneck for largemouth bass in regions where overwinter mortality is size related, which could affect management (i.e., stocking, establishing harvest regulations) of small‐impoundment fisheries.

Natural diet of three species of shrimp in a tropical coastal lagoon

The gut content of 495 specimens of Farfantepenaeus brasiliensis, 131 of F. paulensis (Penaeidae) and 102 of Macrobrachium acanthurus (Palaemonidae) were analyzed to establish the composition of their diets F. brasiliensis had as the most important feeding items in its diet larvae of Chironomidae, Polychaeta and Heleobia australis (Mollusca). For F. paulensis, the most important items were the same as for F. brasiliensis, but the order of importance of H. australis and Polychaeta was inverted. M. acanthurus had detritus as the most important item, followed by Chironomidae larvae, Odonata nymphs, and fragments of the macroalgae Chara. The results showed that the three species were omnivorous, with a varied diet including both components of macrofauna of benthos and associated to the macroalgae Chara and plant fragments and detritus.

The abundance and trophic biology of Clarias albopunctatus Nichols & LaMonte, 1953 (Osteichthyes: Clariidae) in a tropical floodriver basin

The abundance, food and feeding biology of Clarias albopunctatus was studied over a period of 17 months in the lower River Anambra, Nigeria. The catfish was more abundant in late dry season (January–March) and early rainy season (April–June) than in other periods of the year in the small-sized Akwu pond than in other habitats. Feeding intensity was higher at night and at dawn (20.00–05.00 h) than during the day (08.00–17.00 h) in the 151–200 mm TL size class and during the rainy season (April–September). There was no sex-dependent variation in feeding intensity. Insects were the predominant food, followed by crustaceans. Of primary importance were Chironomidae (mainly Chironomus spp. and Tanypus sp.), Odonata nymphs, Dytiscus sp., mosquito larvae and pupae, Gyrinus sp., Daphnia sp., Ostracoda and Tilapia fry. Qualitative food composition and food richness were size, but not sex – or season-dependent. Diet breadth increased with catfish size and during the rainy season. The feeding behaviour of the catfish include foraging, shovelling and surface feeding. Abundant food and ability to switch to more available items enable C. albopunctatus to maintain its abundance in the River Anambra.

Dynamics of manganese, cadmium, and lead in experimental power plant ponds

The purpose of this study was to determine the effect of heated power plant water on the uptake and retention of manganese, cadmium and lead in selected aquatic invertebrates, channel catfish, green sunfish, and aquatic macrophytes and to study the distribution of manganese, cadmium and lead in sediments and water of experimental power plant ponds. The study was accomplished by placing fingerling channel catfish and green sunfish in holding pens in two ponds, one an experimental pond and one a control pond. Whole fish and selected organs of channel catfish and green sunfish were analyzed during the study. The experimental pond received heated power plant water and was maintained 4–6° C above ambient temperature during the study. Sediments, water, Odonata nymphs, tubificid annelids, snails, leeches, fingernail clams and duckweed were also analyzed for the metals. A typical distribution profile for manganese, cadmium and lead in power plant cooling ponds was developed.