Digestive physiology of wild capybara

The capybara (Hydrochaeris hydrochaeris) is a hindgut fermenter whose digestive efficiency is comparable to that of ruminants on similar diets. It is an interesting case for study because it is the largest caecum fermenter and uses coprophagy as part of its digestive strategy. It practices coprophagy in the early morning and forages and defaecates in the evening. Its anatomy is well known but the limited information available about its digestive physiology has been obtained from captive animals. In this work we studied the capybara's digestive physiology, using microbial and chemical information from samples taken from wild capybaras in the early wet season in the morning (0600–0700 hours), noon (1200–1300 hours) and evening (1800–1900 hours), key points in the digestive cycle. Bacteria (cellulolytic and non-cellulolytic) and protozoa were present in high concentrations in the caecum and colon. There were no significant differences in nitrogen concentrations between digestive tract compartments in the coprophagy period (0600 hours), but in the other two periods nitrogen concentrations were significantly higher in the caecum than in the stomach and colon. This is suggestive of selective retention of microbial cells with fluid digesta in the caecum and of cecotrophy (the production of two distinctly different kinds of faeces — one kind called cecotrophes formed from caecal contents and ingested). The capybara hindgut (caecum and colon) with its content, was heavier during the dry season (period of poor diet quality) than in the wet season, but there were no significant seasonal differences between the stomach or small intestine and their contents. This suggests changes in the capacity of the hindgut, the site of microbial fermentation, related to seasonal variation in resource quality.Abbreviations NDF neutral-detergent fibre - SCFA Short-chain fatty acid(s)     

Digestive tract morphology and digestion in the wombats (Marsupialia: Vombatidae)

Summary Wombats consume grasses and sedges which are often highly fibrous. The morphology of the digestive tract and the sequence of digestion were studied in two species of wombats from contrasting habitats: Vombatus ursinus from mesic habitats and Lasiorhinus latifrons from xeric regions. Studies were performed on wild wombats consuming their natural winter diets, and on captive wombats fed a high-fibre pelleted straw diet. Vombatus had a shorter digestive tract (9.2 vs 12.5 times body length) of greater capacity (wet contents 17.9 vs 13.7% body weight) than Lasiorhinus. The most capacious region of the digestive tract was the proximal colon (62–79% of contents). The proportional length and surface area of the proximal colon were greater in Vombatus, but those of the distal colon were greater in Lasiorhinus. These digestive morphologies may reflect adaptations for greater capacity and longer retention of digesta in Vombatus, but greater absorption and lower faecal water loss in Lasiorhinus. Apparent digestion along the digestive tract was estimated by reference to lignin. The proximal colon was the principal site of fibre and dry matter digestion, whereas nitrogen was mainly digested in the small intestine. Depot fats in captive wombats were highly unsaturated and reflected those in the diet. Therefore, lipids, proteins and soluble carbohydrates in the plant cell contents were digested and absorbed in the stomach and small intestine. Conversely, dietary fibre was probably retained and digested by microbial fermentation along the proximal colon.Abbreviations ADF acid detergent fibre - DM dry matter - NDF neutral detergent fibre - SD standard deviation     

Dietary assimilation and the digestive strategy of the omnivorous anomuran land crab<Emphasis Type="Italic"> Birgus latro</Emphasis> (Coenobitidae)

On Christmas Island, Indian Ocean, the diet of robber crabs, Birgus latro (Linnaeus) was generally high in fat, storage polysaccharides or protein and largely comprised fruits, seeds, nuts and animal material. The plant items also contained significant amounts of hemicellulose and cellulose. In laboratory feeding trials, crabs had similar intakes of dry matter when fed artificial diets high in either fat or storage polysaccharide, but intake was lower on a high protein diet. Assimilation coefficients of dry matter (69–74%), carbon (72–81%), nitrogen (76–100%), lipid (71–96%) and storage polysaccharide (89–99%) were high on all three diets. B. latro also assimilated significant amounts of the chitin ingested in the high protein diet ( 93%) and hemicellulose (49.6–65%) and cellulose (16–53%) from the high carbohydrate and high fat diets. This is consistent with the presence of chitinase, hemicellulase and cellulase enzymes in the digestive tract of B. latro. The mean retention time (27.2 h) for a dietary particle marker (⁵⁷Co-labelled microspheres) was longer than measured in leaf-eating land crabs. The feeding strategy of B. latro involves the selection of highly digestible and nutrient-rich plant and animal material and retention of the digesta for a period long enough to allow extensive exploitation of storage carbohydrates, lipids, protein and significant amounts of structural carbohydrates (hemicellulose, cellulose and chitin).Communicated by I.D. Hume     

Utilization of grass carp faeces by the IsopodAsellus aquaticus (L.) in the laboratory

Grass carp (Ctenopharyngodon idella Val) faecal pellets derived fromElodea nutallii consumption were efficiently utilized by the detritivoreAsellus. Immature and adult individuals of 2.1–3.2 mm and 4.9–6.0 mm respectively, exhibited a high mean specific growth (9.03%/day and 3.33%/day) when offered faecal pellets as food during two weeks experimental trials. Individuals of the same groups, when fed onElodea which had been mechanically fragmented to simulate the macerating action of the grass carp pharyngeal teeth, grew at rates (9.57%/day and 4.06%/day) not significantly different from those fed on faecal pellets. However, the growth rates of animals fed on freshElodea (6.40%/day and 2.23%/day) were significantly lower than in the above trials, indicating that the morphological destruction of the plant tissue could be responsible for the higher observed growth. The control trials, including unfed animals, showed negative growth (– 0.49%/day and – 0.48%/day).Grass carp herbivory makes a new food resource available to benthic invertebrates by converting fresh plant material to small plant fragments.     

Selective ingestion of phytoplankton by the bivalvesMytilus edulis L. andCerastoderma edule (L.)

Blue mussles (Mytilus edulis) and cockles (Cerastoderma edule) were collected in the Oosterschelde estuary (SW Netherlands) and exposed to diets consisting of the diatomPhaeodactylum tricornutum and silt. Algal concentrations were kept constant (20.10³ cells.ml^–1), and silt concentrations were varied between 3–80 mg.l^–1 (mussel experiments) and 20–120 mg.l^–1 (cockle experiments). Chlorophyll-a concentrations in the pseudofaeces were reduced compared to the diets, indicating selective ingestion of the algae. It was estimated that the mussels increase the ingestion of chlorophyll-a 2.0 times, and the cockles increase the chlorophyll-a ingestion 2.8 times, compared to the ingestion rate without selection. The selection coefficients were not affected by the SPM concentrations used. Phaeophytin-a concentrations in the faeces showed an increase as a consequence of the digestion of the ingested algae. Digestive efficiencies of chlorophyll-a varied between 36–92% The digestive efficiencies decreased with increasing SPM concentrations.Communication no. 541 of the Delta Institute for Hydrobiological Research.     

Disappearance of immunoreactive glycinin and 𝛃-conglycinin in the digestive tract of piglets

Soybean allergy represents a health threat to human and animals. Glycinin and β-conglycinin, the main storage proteins in soybean, have been identified as major food/feed allergens. The present study was conducted to investigate the disappearance of immunoreactive glycinin and β-conglycinin in the digestive processes of piglets. Twelve crossbred piglets, weaned at 21 days of age, were allocated to three dietary treatments in a complete block design, each treatment with four replicates (female/male = 1:1). From day 22–28, the control group was fed diets without leguminous products, while the two treatment groups received diets containing 2.2% purified glycinin or β-conglycinin. All piglets were slaughtered at 29 days of age and digesta was sampled from stomach, middle jejunum, caecum and colon. Results indicated that immunoreactive glycinin and β-conglycinin decreased as the digesta descended down the digestive tract to 0.12% and 0.47%, respectively. Little immunoreactive glycinin was found in the digesta of caecum and colon, while immunoreactive β-conglycinin was detected in the colon. Along the whole digestive tract the disappearance of immunoreactive glycinin was significantly higher than β-conglycinin (p < 0.05).     

Digestive strategy of the asian colobine genusTrachypithecus

The Asian colobines,Trachypithecus obscurus andT. cirstantus, eat plant-based diets containing 55–80% leaves. The structural polysaccharides in leaves and other plant parts require microbial fermentation before they can be used as an energy source by the monkeys. The major compartments of the gastro-intestinal tract ofTrachypithecus are a voluminous haustrated stomach, a long small itnestine and capacious haustrated hindgut, all of which contribute to the digestive strategy of these two species. Results of digesta marker passage studies indicate there is prolonged retention of digesta for fermentation in both the stomach and haustrated colon. The digestive strategy of these colobines is defined as gastro-colic fermentation, unlike that of other forestomach fermenters in which the hindgut fermentation is of secondary importance.     

Digestive performance and selective digesta retention in the long-nosed bandicoot,Perameles nasuta,a small omnivorous marsupial

Bandicoots are opportunistic omnivores that feed on invertebrates, fungi and both epigeal and hypogeal plant parts. We examined the performance of the digestive tract of the long-nosed bandicoot (Perameles nasuta) in terms of intake and total digestibility, patterns of excretion of inert digesta markers, and likely sites of digesta retention, on two diets designed to mimic part of their natural plant and insect diets. On the insect diet (mealworm larvae), bandicoots virtually maintained body mass at a digestible energy intake of 511 kJ · kg^-0.75 · day^-1 and were in strongly positive nitrogen balance. In contrast, on the plant diet (shredded sweet potato), bandicoots ate only one-third as much digestible energy, lost 7% body mass, and were in negative nitrogen balance. Mean retention times of two particle markers on the plant diet (27.5 and 27.0 h) were more than double those on the insect diet (12.4 and 11.2 h), and on both diets the mean retention time of the fluid digesta marker was greater than those of the particle markers, indicating consistent selective retention of fluid digesta in the gut. It was seen radiographically than in mealwormfed bandicoots major sites of digesta retention were the distal colon and rectum, whereas in the sweet potato-fed animals the caecum and proximal colon were principal sites. It was concluded that retention of plant material in the caecum and proximal colon (the main sites of microbial digestion) and the preferential retention of fluid digesta (together with bacteria and small feed particles) in the caecum were important factors in the ability of bandicoots to switch between insect and plant foods, depending on relative availabilities, and thus to exploit nutritionally unpredictable environments.Abbreviations ADF acid-detergent fibre - bm body mass - Co-ED-TA cobalt-ethylenediaminetetra-acetic acid - CWC cell wall constituents - DE digestable energy - dm dry matter - EUN endogenous urinary nitrogen - ICP inductively-coupled plasma atomic emission spectroscopy - MFN metabolic faecal nitrogen - MRT mean retention time - NDF neutral-detergent fibre - ww wet weight     

Disappearance of immunoreactive glycinin and beta-conglycinin in the digestive tract of piglets

Soybean allergy represents a health threat to human and animals. Glycinin and beta-conglycinin, the main storage proteins in soybean, have been identified as major food/ feed allergens. The present study was conducted to investigate the disappearance of immunoreactive glycinin and beta-conglycinin in the digestive processes of piglets. Twelve crossbred piglets, weaned at 21 days of age, were allocated to three dietary treatments in a complete block design, each treatment with four replicates (female/male = 1:1). From day 22-28, the control group was fed diets without leguminous products, while the two treatment groups received diets containing 2.2% purified glycinin or beta-conglycinin. All piglets were slaughtered at 29 days of age and digesta was sampled from stomach, middle jejunum, caecum and colon. Results indicated that immunoreactive glycinin and beta-conglycinin decreased as the digesta descended down the digestive tract to 0.12% and 0.47%, respectively. Little immunoreactive glycinin was found in the digesta of caecum and colon, while immunoreactive beta-conglycinin was detected in the colon. Along the whole digestive tract the disappearance of immunoreactive glycinin was significantly higher than beta-conglycinin (p < 0.05).     

Digesta retention in the gastro-intestinal tract of the orang utan (Pongo pygmaeus)

The diet of the orang utanPongo pygmaeus consists of fruit, leaves, communal insects, and bark, and contains appreciable amounts of non-starch polysaccharides. These complex carbohydrates require microbial fermentation before they can be used as an energy source by the orang utans. The gastrointestinal tract ofP. pygmaeus consists of a simple or unipartite stomach, a relatively long small intestine, and a complex haustrated caecum and colon. This morphology suggests that the capacious proximal colon is the principal site of digesta retention and fermentation of non-starch polysaccharides. We measured several parameters of digesta retention by giving three captive adultP. pygmaeus a pulse dose of inert markers specific for the solute and particulate phases of the digesta and collected their faeces at regular intervals over 192–338 hours. Transit times (times of first appearance of the markers in the faeces) and mean retention times (MRT) were long, consistent with a large complex gastro-intestinal tract. MRTs for the particulate marker were longer (p=0.032) than for the solute marker, indicative of selective retention of large particulate digesta. These results are consistent with the patterns of marker excretion in other mammals that use the digestive strategy of colon fermentation.     

Hindgut fermentation in the wombats: two marsupial grazers

Summary The wombats Vombatus ursinus and Lasiorhinus latifrons have a capacious proximal colon with only a vestigial caecum. The pattern of microbial fermentation in the hindgut of both species was studied in captive animals fed a pelleted straw diet and in wild wombats feeding on their natural winter diets. Digesta pH was low in the stomach but near neutrality along the hindgut, indicating effective absorption and/or buffering of the colonic contents. Initial proportions and production rates of short chain fatty acids in vitro reflected the fermentation of plant cell walls. Proportions of isobutyrate, isovalerate and n-valerate increased towards the distal colon indicating proteolysis and subsequent fermentation of amino acids. The low ammonia content of digesta fluid suggested that ammonia released from these amino acids was absorbed and utilized by the wombats and their gut microbes. Wild wombats had higher concentrations and production rates of short chain fatty acids than captive animals, which was consistent with the higher apparent digestibility of their natural diet. The energy from short chain fatty acids in captive animals was 30–33% of digestible intake. Energy intakes were low and similar to resting metabolic rates estimated for marsupials. Actual resting metabolic rates of the wombats are probably lower than these estimates, and the proportion of energy derived from fermentation substantially higher than the 53–61% estimated in wild wombats. The energy from fermentation clearly enables wombats to utilize diets high in fibre.Abbreviations DEI digestible energy intake - DM dry matter - NDF neutral detergent fibre - SCFA short chain fatty acids - SD standard deviation - SMR standard metabolic rate     

Biosorption of reactive dyes by the mycelium pellets of a new isolate of Penicillium oxalicum

Three reactive dyes were rapidly adsorbed by the mycelium pellets of Penicillium oxalicum. Dye removal of Reactive Blue 19 was up to 60% in 10 min and 91% in 80 min. Dye adsorption isotherms fitted Langmuir model well and the maximum adsorption capacities at 20 °C were calculated to be 160 mg g^–1 for Reactive Blue 19, 122 mg g^–1 for Reactive Red 241 and 137 mg g^–1 for Reactive Yellow 145, respectively. The pellets exhibited a high dye adsorption capacity (80–180 mg g^–1) for all of the 3 dyes over a wide pH range (pH 2–10), and the maximum adsorption was obtained at pH 2. The adsorption capacity was mildly increased by increasing salinity.     

Diet spectrum of great cormorants (<Emphasis Type="Italic">Phalacrocorax carbo sinensis</Emphasis> L.) at the Donji Miholjac carp fishponds in eastern Croatia

This paper reports the results of a diet analysis from the digestive tracts of 203 great cormorants shot at the Donji Miholjac fishponds in eastern Croatia, in the period 2000–2002. Eight fish species were determined. The dominant species was common carp (Cyprinus carpio) with a relative frequency of 73.4%, followed by grass carp (Ctenopharingodon idella) (11.6%), bighead carp (Aristichthys nobilis) (7.2%), pikeperch (Sander lucioperca) (2.0%), wels catfish (Silurus glanis) (1.7%), pike (Esox lucius) (1.5%), topmouth gudgeon (Pseudorasbora parva) (1.5%) and Prussian carp (Carassius auratus gibelio) (1.1%). The diet spectrum of the great cormorants from the Donji Miholjac fishponds was in accordance with the structure of the fish population in the fishponds. The average stomach weight per bird was 244 g. When birds shot with an empty stomach were excluded, the average stomach weight increased to 286 g. The length of consumed fish ranged from 40–335 mm, with 47% of the fish belonging to the length category 100–149 mm. The study revealed no significant relationship between the weight of the consumed fish and the body weight of male and female cormorants.     

Trade-off between digestion and respiration in two airbreathing callichthyid catfishes Holposternum littorale (Hancock) and Corydoras aeneus (Gill)

In callichthyid catfishes, the posterior intestine is modified to function as an air breathing organ by being air-filled, thin-walled and highly vascularized. These modifications make it unsuitable for digestive functions and digesta has to be transported quickly through this region to minimize disruption of vital respiratory functions. However, the weak muscles of the wall of the respiratory intestine make this problematic. It is hypothesized that the unidirectional ventilatory air current within the respiratory intestine is responsible for the quick transport of digesta through the respiratory intestine. To verify this, movement of digesta through the alimentary tract was examined in Hoplosternum littorale and Corydoras aeneus that were either allowed to breathe air or prevented from air breathing. When air breathing was prevented, digesta was not transported to the rectum in H. littorale and there was a 94% reduction in the amount of digesta in the rectum of C. aeneus. This study suggests that the anterior digestive intestine facilitates the passage of air although it is filled with digesta. The anterior digestive intestine packages digesta into a string of slightly compressed boluses, creating an air channel in the digestive intestine thus allowing air to pass unimpeded.     

Entomogenous Fungi as Promising Biopesticides for Tick Control

When ticks were sealed in nylon tetrapacks and infected with the entomogenous fungi, Beauveria bassiana and Metarizium anisopliae and maintained in potted grass in the field, the fungal oil formulations (10⁹ conidia per ml) induced 100% mortality in larvae of Rhipicephalus appendiculatus and Amblyomma variegatum, whereas mortalities in nymphs varied between 80–100% and in adults 80–90%. The aqueous formulations (10⁹ conidia per ml) induced mortalities of 40–50% and reductions in egg hatchability of 68% (B. bassiana) and 48% (M. anisopliae) when sprayed on Boophilus decoloratus engorging on cattle. The strains of B. bassiana and M. anisopliae isolated from naturally infected ticks were also found to induce high mortalities in both R. appendiculatus and A.variegatum in tetrapacks placed in potted grass. Both aqueous and oil-based formulations were found to be effective, although the latter induced higher mortalities. These fungal strains in aqueous formulation (10⁸ conidia per ml) suppressed on-host populations of adult R. appendiculatus by 80% (B. bassiana) and 92% (M. anisopliae) when sprayed on tick-infested grass once per month for a period of 6 months. The feasibility of using entomogenous fungi for tick control in the field is discussed.     

Digestive performance and digesta passage in the omnivorous greater bilby, Macrotis lagotis (Marsupialia: Peramelidae)

Omnivores such as the greater bilby (Macrotis lagotis) consume a variety of dietary items and often are faced with large changes in the nutrient composition of their food. This paper explores the basis for the dietary flexibility of the bilby by comparing digestive performance and digesta retention patterns of captive bilbies fed either an insect diet (mealworm larvae) or a plant diet (mixed seeds). Mean retention times (MRTs) of particle and solute markers in the gastrointestinal tract did not differ significantly between the two diets, but MRT of the particle marker was significantly longer than that of the solute marker on both the mealworm (particle: 23.5 h; solute: 17.9 h) and mixed seed (particle 33.0 h; solute: 30.2 h) diets. Lack of selective retention of solutes and small particles in the bilby gastrointestinal tract probably restricts them to relatively low-fibre diets, such as those based on seeds rather than leaves and stems of plants. It was observed radiographically that the major sites of digesta retention were the caecum, proximal colon and distal colon, and thus the hindgut is probably the principal site of microbial fermentation. The mealworms were more digestible than the mixed seeds, but digestible energy intake (mealworm: 939 kJ · kg^−0.75 · d⁻¹; mixed seed: 629 kJ · kg^−0.75 · d⁻¹) was high enough for maintenance of body mass and positive nitrogen balance on both diets. Thus, although bilbies may be limited in their ability to utilize high-fibre diets by a lack of selective retention of solutes and small particles in their hindgut, their digestive strategy is flexible enough to accommodate at least some diets of both animal and plant origin. Such a strategy should benefit an animal inhabiting environments in which food resources are unpredictable in their relative abundance. Accepted: 26 May 2000     

Flexibility of digestive responses in two generalist herbivores,the tortoises Geochelone carbonaria and Geochelone denticulata

Summary To test the prediction that digestive responses digestibility, intake and passage time-of generalist herbivores vary with different diets, feeding trials were conducted in Venezuela with two sympatric tortoise species, Geochelone carbonaria and G. denticulata. Three single-species diets (two fruit, one foliage) were fed to both species. For a given diet, digestibility, mass-specific intake and passage time did not differ between the two tortoise species, nor did they vary by sex or body mass within each species. However, the digestive parameters varied for tortoises feeding on the different diets. The responses ranged from nearly abandoning cell wall fermentation and depending entirely on extraction of cell contents to relying heavily on cell wall fermentation. Therefore, these generalist herbivores have flexible digestive responses that are influenced by diet, not fixed digestive responses that limit the diet, as previously observed in other generalist herbivores. A three-part classification of herbivores (specialist, specialized mixed feeder and opportunistic mixed feeder) is suggested as an approach to understanding flexible and inflexible digestive strategies in herbivores.     

Hindgut microbes, fermentation and their seasonal variations in Hokkaido native horses compared to light horses

Fecal bacteria and protozoa of Hokkaido native horses and light horses were enumerated to compare seasonal variation in hindgut microbes and fermentation between the two breeds. Fecal samples were collected in winter and summer from eight horses (four for each breed) that had been reared together under the same conditions after birth (on woodland pasture in winter and on grassland pasture for the rest of the year). Total fecal bacteria counts for both breeds showed temporal variation, with the highest levels occurring in summer (P<0.05). For both breeds, Gram-negative rods were the major constituents (58–69%) and showed higher counts in winter (P<0.05) than in summer. Total protozoa counts in both breeds were lower in winter than in summer (P<0.05). The proportion of large cellulolytic protozoa such as Cochliatoxum periachtum was increased (P<0.05) in winter, and this tended to be more pronounced in native horses. Although total volatile fatty acids (VFA) in feces were lower in winter (P<0.05), the reduction was smaller in native horses (P<0.05). Fecal VFA pattern showed a shift toward more acetate and less propionate production in winter regardless of the horse breed. Evaluation of digestive tract organs in 12 animals showed that the relative weight of the colon in body weight or total digestive tract weight is larger in native horses than in light horses (P<0.05). The present results suggest that hindgut microbial adaptation to winter diets occurs to a greater extent in native horses, as partly characterized by advantages in anatomy.     

Effects of different forms of Acacia saligna leaves inclusion on feed intake, digestibility and body weight gain in lambs fed grass hay basal diet

The study was undertaken to determine the effects of different forms of Acacia saligna leaves inclusion on feed intake, digestibility and body weight gain in lambs fed grass hay basal diet. Twenty local ‘Farta’ yearling male lambs weighing 17.4 ± 0.10 kg (mean ± SD) were randomly allocated to four dietary treatments consisting of daily feeding of lambs in T1 with 700 g grass hay (dry matter basis), and daily free choice feeding of lambs in T2, T3, and T4 with 700 g grass hay + 700 g fresh, wilted, and dried A. saligna leaves, respectively. Inclusion of different forms of A. saligna leaves improved (P<0.01) the daily intake of total DM by 8–9% and that of OM and CP by 7 and 38%, respectively compared to the control. The daily intake of NDFom was lower (P<0.01) by 1–2.3%, whereas that of the ADFom intake declined (P<0.01) by 1.3–3.4% for lambs on wilted and dried forms of A. saligna leaves. Inclusion of A. saligna leaves replaced the intake of the grass hay by 26–27% of the total diet and reduced (P<0.05) apparent digestibility coefficient of the total DM by 9, 7, and 4%, OM by 7, 6 and 4%, and CP by 12, 12, and 9%, but improved (P<0.05) apparent digestibility coefficient of NDFom by 3–4% compared to the control diet. Dried A. saligna leaves improved (P<0.05) apparent digestibility of DM, OM and CP compared to fresh A. saligna leaves. Lambs fed on hay alone lost (P<0.05) body weight, while the lambs supplemented with A. saligna leaves gained (P<0.05) weight. The results of this study revealed that A. saligna leaves could be best included in the grass hay based feeding in dried form at the rate of 265 g/kg DM for improved nutrient utilization and growth performance of yearling lambs.     

Experimental formulations ofBacillus sphaericus for the control of anopheline and culicine larvae

Summary Four experimental formulations ofBacillus sphaericus Neide (2362 isolate) were evaluated for larvicidal activity against culicine and anopheline larvae in several natural and artificial habitats. A granular formulation (5% primary powder) was tested against natural populations of mosquitoes in two simulated habitats in Florida and in maturing and reflooded rice fields in Louisiana. Larvae ofCulex quinquefasciatus Say were reduced by 97 and 99% after application of the granules at the rate of 10 kg/ha to polluted tanks and 2.5 kg/ha to sod-lined potholes, respectively. Anopheline andPsorophora columbiae (Dyar and Knab) larvae were reduced by 68 and 92–100%, respectively, after application of 5 kg granules/ha to rice fields. A flowable concentrate (12.8% primary powder) applied to unpolluted and organically enriched habitats in Florida at 0.25 kg/ha reduced populations ofCulex spp. by 93–100% and 99%, respectively. Sustained-release briquets (5% primary powder) applied at the rate of one half briquet/1.8 m² sod-lined potholes reduced larval populations ofCx. quinquefasciatus by 88–95% for up to 2 weeks in open sunlight. Sustained-release pellets (30% primary powder) applied to small woodland pools in Memphis, TN at the rate of four pellets/pool virtually eliminated larval populations ofCx. restuans Theobald for over 8 days. Variable persistance of larvicidal activity was noted for the other treatments depending on the formulation, target species and habitat.