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Biomedical subjects

M S Mulla

Publications and source records attributed to M S Mulla.

At least 55 records · Page 3Linked to original sources
PubMed1991

Biological control of Culex mosquitoes (Diptera: Culicidae) by the tadpole shrimp, Triops longicaudatus (Notostraca: Triopsidae).

Laboratory oviposition choice tests and behavioral observations indicated that the activity of tadpole shrimp, Triops longicaudatus (LeConte), near the water surface deterred gravid Culex quinquefasciatus Say from ovipositing. In the cities of Oasis and Riverside, Calif., tadpole shrimp significantly reduced the abundance of immature mosquitoes (Cx. tarsalis Coquillett and Cx. quinquefasciatus) probably due to lowered oviposition rates, as well as tadpole shrimp predation. Generally, mosquito oviposition rates in field ponds with tadpole shrimp were lower than that of controls, except when tadpole shrimp were very young (4 d after flooding) or when their abundance had declined late in the flooding period. When analyzed by pond, tadpole shrimp size was correlated inversely with abundance; however, differences in size or abundance did not affect their capacity to reduce mosquito populations.

Animals↗
PubMed1991

Delayed mortality and morphogenetic anomalies induced in Culex quinquefasciatus by the microbial control agent Bacillus sphaericus.

Two preparations of Bacillus sphaericus 2362 were studied for their biological activity, delayed mortality and the induction of morphogenetic aberrations in larvae, pupae and adults of Culex quinquefasciatus. Longevity and fecundity of adult mosquitoes were also assessed. A dosage response line for B. sphaericus was established against 4th-instar larvae and sublethal concentrations (48 h LC50 and lower) were used against these larvae. Sublethal concentrations of B. sphaericus induced delayed mortality in larvae, pupae and adults. The magnitude of mortality increased in succeeding cohorts and developmental stages resulting from the surviving larvae. Only 10 and 25% overall emergence of viable adults occurred in the sublethal treatments (LC25) of 2 B. sphaericus preparations. The range of successful adult emergence was over 94% in the controls. A wide range of external morphogenetic aberrations in dead larvae, pupae and adults were noted. These aberrations and gross morphological features were quite similar to those reported for certain insect growth regulators. Sublethal concentrations had no marked effect on longevity of adults, egg deposition and hatch.

Abnormalities, Multiple↗
PubMed1991

Delayed mortality and morphogenetic anomalies induced by the microbial control agent Bacillus thuringiensis ser. (H-14) in Culex quinquefasciatus.

Sublethal concentrations of Bacillus thuringiensis ser. H-14 were applied to early 4th-instar larvae of Culex quinquefasciatus to assess mortality and morphogenetic aberrations in larvae, pupae and adults. At the 24 h LC10, LC25, LC50 and LC80, additional mortality occurred in surviving larvae beyond a 24 h exposure period. The cumulative mortalities increased daily and the overall mortality of larvae up to 7 days posttreatment were 12, 73, 82 and 96% at the indicated concentrations, respectively. Delayed mortality also occurred in the pupal and adult stages. Morphogenetic aberrations were noted in dead larvae and pupae but were rare in the adults. These aberrations are categorized and described. There was little or no delayed effect on the survivorship or fecundity of adults, but in all the treatments the number of emerging males was higher than females. The sex ratio in check adults was 1:1.

Animals↗
PubMed1991

Microbial larvicides for the control of nuisance aquatic midges (Diptera: Chironomidae) inhabiting mesocosms and man-made lakes in California.

Bacillus thuringiensis var. israelensis (B.t.i.) and B. sphaericus were evaluated for chironomid larvicidal activity in freshwater mesocosms. Of two B.t.i. formulations, the technical powder ABG-6164 provided excellent control of chironomines (94%) at the rate of 11.2 kg/ha whereas the liquid concentrate, Vectobac 6 AS, achieved only moderate control (57%) at the rate of 22.4 kg/ha. In contrast, similar rates of B. sphaericus products, ABG-6184 technical powder and BSP-2 flowable concentrate, produced no significant reduction. Lake studies were initiated to determine which B.t.i. formulations were practical and effective in large-scale situations. Two sinking granular corn grit formulations worked with varying degrees of success but were deemed too bulky for extensive applications. B.t.i. technical powder preparations with high potency ratings of 5,000 and 12,430 ITU/mg gave excellent control of Chironomus spp. (100% and 87%) when used at the rates of 6.7 and 2.8 kg/ha, respectively. None of the treatments reduced larval populations of the tanypodines, Procladius and Tanypus.

Animals↗
PubMed1990

Ecology of Culex tarsalis (Diptera: Culicidae): factors influencing larval abundance in mesocosms in southern California.

Colonization and succession of mosquitoes and macroinvertebrate predators were studied in 30-m2 ponds (mesocosms) during summer and fall 1987. Larval abundance of Cx. tarsalis Coquillette was lower during the hot, summer months than during the fall. In all studies, larval populations declined markedly 2-3 wk after habitat flooding. Although predator abundances differed in these studies, sometimes by an order of magnitude, the common predators colonized mesocosms in the following order: Triops, hydrophilid beetle larvae, dytiscid beetle larvae, mesoveliids, dragonfly and damselfly naiads, and notonectids. The similarity of the colonization phenologies probably resulted from the vagility of the adult insects and species-specific developmental rates. Stepwise multiple regression was used to identify factors potentially affecting larval mosquito populations. For most studies, coleopteran larvae were related inversely to per capita change in the entire larval population and the third- and fourth-instar subpopulation (i.e., large coleopteran larval populations were associated with large declines in the Cx. trasalis larval population). Maximum water temperatures and pond age (days after flooding) also were identified as significant factors affecting larval abundance and per capita change of mosquitoes. Potentially lethal water temperatures (greater than or equal to 35 degrees C) occurred during the summer; however, the declines in larval abundance of Cx. tarsalis were not restricted to (or obviously associated with) periods of high water temperature. Our results indicated that predation by coleopteran larvae and factor(s) associated with pond age, such as mosquito ovipositional preferences, significantly affected Cx. tarsalis larval populations.

Animals↗
PubMed1990

Comparative functional morphology of the mouth brushes of mosquito larvae (Diptera: Culicidae).

Structural and morphological features of the feeding brushes of fourth instars of four species of mosquitoes were studied using light and scanning electron microscopes. The fine structure of the elements of the lateral palatal brushes, anteromedian palatal brushes, mandibular brushes and combs, and maxillary brushes of each species was investigated and related to feeding behavior. The movement of the mouth brushes in living larvae was observed by stereomicroscopy under laboratory conditions. Mouth brush function and morphology varied among the species studied. The brushes of Culex quinquefasciatus Say, Cx. tarsalis Coquillett, and Aedes aegypti L. were more complex than those of Anopheles albimanus Wiedemann. The main role of the filaments of the lateral palatal brushes (LPB) was to generate and maintain water and particle flow around the larval head. In Ae. aegypti, most of the LPB filaments were provided with stout pointed teeth at the tips which were useful in the brushing of food material. In An. albimanus, the LPB filaments were simple and very closely packed and were used to stir the water surface film to direct the floating materials into the area of the mouth opening. The filaments of the anteromedian palatal brush (APBr) in the Culex species were branched. In Ae. aegypti, the APBr contained long bladelike filaments and short teethlike elements, whereas in An. albimanus, the APBr filaments were all long and bladelike. The morphological structure of the spicules and setae of the mandibular brushes and combs and the maxillary brushes are described. The main function of these brushes is to direct and concentrate particle flow.

Aedes↗
PubMed1990

Studies on the bioecological aspects of adult mosquitoes in the Prado Basin of southern California.

Studies on the bionomics of adult mosquitoes were carried out in the Prado Basin of southern California during 1985-86. The faunal composition of mosquitoes caught by species was (in descending order) Culex quinquefasciatus, Cx. tarsalis, Cx. erythrothorax, Cx. stigmatosoma (formerly Culex peus) followed by Anopheles freeborni, Culiseta particeps, Cs. inornata and Cs. incidens. The number of mosquitoes per trap night was the lowest during December through February, and the highest during August through October. Depending on both intrinsic and extrinsic factors, adult mosquitoes were active at dusk and dawn. In spatial distribution studies, both adult and larval collections showed that Cx. quinquefasciatus and Cx. stigmatosoma were associated with dairy lagoons and Cx. erythrothorax with duck ponds and a nearby wooded area. Culex tarsalis was found in greater number at all habitats. Anopheles freeborni and Culiseta spp. were found around the wooded area. In vertical distribution studies, more mosquitoes were captured at the highest (6 m) level than at lower (0.6 and 3 m) levels which was probably due to the large percentage of parous females present at this site.

Animals↗
PubMed1990

Fate and persistence of Bacillus sphaericus used as a mosquito larvicide in dairy wastewater lagoons.

The fate and persistence of the mosquitocidal bacterium, Bacillus sphaericus, in dairy wastewater lagoons was evaluated in conjunction with trials of its larvicidal efficacy against Culex stigmatosoma. Two commercial formulations, BSP-2 (at 4.48 kg/ha) and ABG-6184 (at 2.24 kg/ha) gave about 90% reduction for up to 4 weeks, although surface water lost its insecticidal activity by 3 days posttreatment. Spores settled to the bottom within 3 days of treatment, but could be recovered in surface water after reflooding. Spore concentrations in bottom water varied widely, yet insecticidal activity remained high for from 3 days (BSP-2 at 4.48 kg/ha) to 2 weeks (ABG-6184 at 2.24 kg/ha). Spores persisted in the mud throughout the study period. These results indicate the extended control obtained was due primarily to the ingestion of spores from bottom water and mud by larvae, which routinely inhabit the shallow areas toward the edge of the pond and browse at the pond bottom.

Animals↗
PubMed1990

Distribution of Culex tarsalis larvae in a freshwater marsh in Orange County, California.

The distribution and abundance of mosquito larvae in a freshwater marsh were determined during a low water period in the late summer. Culex tarsalis larval abundance was significantly associated with the percent cover by Typha spp. root masses and Typha spp. stem density in 1-m2 quadrants. Larval mosquito abundance was not significantly related to bulrush (Scirpus californicus) stem density, position in the marsh (transect compass direction), position in the inundated vegetation on each transect or several physicochemical factors. As water levels decline seasonally, mosquito developmental sites in San Joaquin Marsh change from mats of decaying vegetation to cattail root masses.

Animals↗
PubMed1990

Influence of tadpole shrimp, Triops longicaudatus (Notostraca:Triopsidae), stocking rate on Culex tarsalis development in experimental field microcosms.

The effectiveness of 5 tadpole shrimp (TPS) stocking rates to reduce cohorts of Culex tarsalis was studied in field microcosms (0.81-m2). Larval/pupal abundance in microcosms containing greater than 5 TPS/m2 was significantly (P less than 0.05) lower than that of controls lacking tadpole shrimp due to predation. Adult mosquito abundances captured in emergence units above the microcosms stocked with tadpole shrimp were significantly (P less than 0.05) lower than that of controls at rates greater than or equal to 10 TPS/m2. Tadpole shrimp growth during 17 days of this study was inversely proportional to their stocking rate, and a linear relationship between size and stocking rate was plotted. Tadpole shrimp stocking rates also influenced rate of mosquito development, causing significantly (P less than 0.05) shorter periods for 50% emergence where shrimp were present when compared with that of controls. Adult male Cx. tarsalis emerged significantly earlier then females in microcosms stocked at 5 TPS/m2, while no significant (P greater than 0.05) differences were detected between the sexes at the remaining predator stocking rates.

Animals↗
PubMed1989

Ingestion, dissolution, and proteolysis of the Bacillus sphaericus toxin by mosquito larvae.

Larvae of Culex quinquefasciatus are much more susceptible to the toxin of Bacillus sphaericus than are larvae of Aedes aegypti. In the present study, the rate of ingestion, dissolution, and the cleavage by midgut proteases of the B. sphaericus toxin were compared in larvae of these species to determine whether these factors account for the differences in susceptibility. During filter feeding, larvae of both species removed significant quantities of B. sphaericus toxin from suspensions. Filtration rates for 1 hr, the time at which C. quinquefasciatus exhibited marked intoxication, were higher for A. aegypti (576-713 microliters/larva/hr) than for C. quinquefasciatus (446-544 microliters/larva/hr). Within 24 hr of exposure, A. aegypti larvae ingested 97-99% of the toxin particulates and suffered not more than 10% mortality in suspensions which induced complete mortality in C. quinquefasciatus within 2 hr of exposure. Quantification of the particulate toxin present in larvae after exposure to B. sphaericus suspensions revealed that larvae of both species contained only minor amounts of the toxin, suggesting the larvae had been able to solubilize the toxin after ingestion. Proteases recovered from the feces of larvae cleaved at 43-kDa protein isolated from B. sphaericus toxin extract to 40 kDa in both species. Thus, differences in susceptibility to the B. sphaericus toxin between A. aegypti and C. quinquefasciatus are not due to differences in rates of ingestion, dissolution, or the specificity of proteases.

Aedes↗
PubMed1989

Factors influencing ingestion of particulate materials by mosquito larvae (Diptera: Culicidae).

Relative ingestion rates of mosquito larvae, as indicated by the number of substrate-filled gut segments per unit time, were determined for Culex tarsalis Coquillett, Aedes aetypti L., and Anopheles albimanus Wiedemann. Among the three species, Ae. aegypti larvae were the most rapid feeders. F50 (median time for complete repletion of 50% of the larvae) was 61, 42, and 100 min for the three species feeding on a wheat flour suspension, respectively. Food particles with nutritive values (dried yeast, wheat flour, fishmeal, or dried blood) were ingested faster than inert particles (kaolin, talc, chalk, or charcoal). The addition of aqueous yeast extracts containing phagostimulants accelerated the ingestion of inert particles. Increasing the concentration of inert particles did not increase ingestion rates. Larval age, water temperature, and starvation, but not larval density, influenced rates of ingestion. Younger instars were more rapid feeders than older instars. First instars of the three species filled their guts with wheat flour approximately two times faster than fourth instars. Increasing water temperature from 18 to 31 degrees C accelerated wheat flour ingestion by fourth instars of Cx. tarsalis, Ae. aegypti, and An. albimanus by factors of 1.9, 1.5, and 1.7, respectively. After starvation for 12 h, fourth instars of Cx. tarsalis and Ae. aegypti increased ingestion of wheat flour about 1.6 and 1.8 times, respectively. In contrast, starvation of An. albimanus larvae for the same period resulted in decreased wheat flour ingestion by 2.2 times when compared with unstarved larvae. These results indicare that, in addition to the chemical factors associated with the food substances, the physiological and environmatal conditions of the larvae play an important role in regulating the ingestion rate of suspended particles by mosquito larvae.

Aedes↗
PubMed1989

Impact of new insect growth regulators and their formulations on mosquito larval development in impoundment and floodwater habitats.

Four insect growth regulators were evaluated in the laboratory and field. In the laboratory, AC-291898 showed excellent activity, inducing 90% mortality in Culex quinquefasciatus and Aedes aegypti at 0.5-0.7 ppb. The EC formulation of XRD-473 was slightly more active than the technical material with an LC90 of 0.84 ppb and 0.92 ppb against Ae. aegypti and Cx. quinquefasciatus, respectively. In the field, AC-291898 at the rates of 0.005 and 0.01 lb AI/acre caused 85 and 100% inhibition of adult emergence of Cx. tarsalis 2 days after treatment. Activity, however, declined at the low rate, while the high rate remained active for more than 7 days. In the same species, XRD-473 induced complete inhibition of adult emergence 2 days after treatment at the rates of 0.01, 0.025 and 0.05 lb AI/acre. At the low rate (0.01 lb AI/acre), activity declined markedly, while the 2 higher rates remained active for one week. In Cx. peus larvae, AC-291898 at the rates of 0.005, 0.01 and 0.025 lb AI/acre produced complete inhibition of adult emergence 2 days after treatment, but activity declined at the 2 lower rates 7 days after treatment, while the high rate (0.025 lb AI/acre) remained active for more than one week. Methoprene (4%) pellets were effective against Cx. tarsalis for 7 days at the rates of 0.25 lb AI/acre whereas 0.5 lb AI/acre was required to obtain similar results against Cx. peus larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Prey-size selection by Triops longicaudatus (Notostraca: Triopsidae) feeding on immature stages of Culex quinquefasciatus.

The tadpole shrimp, Triops longicaudatus, was found to be a size-dependent predator of Culex quinquefasciatus larvae in the laboratory. However, changes in tadpole shrimp size were accompanied by changes in prey-size preference: larger-sized predators consumed an increasing proportion of larger prey items. Very large tadpole shrimp may be nonselective predators of this mosquito species. Quantified behavioral observations indicated that while second instar mosquito larvae were encountered significantly less frequently than were fourth instar larvae or pupae, they were captured at significantly greater rates and with shorter handling times. It is hypothesized that prey vulnerability has an important influence on tadpole shrimp prey size "preferences."

Animals↗
PubMed1988

Efficacy and longevity of Bacillus sphaericus 2362 formulations for control of mosquito larvae in dairy wastewater lagoons.

Bacillus sphaericus strain 2362 was evaluated for the control of Culex larvae in dairy wastewater lagoons. Both initial and long-term efficacy were studied. Two primary powder preparations of ABG-6184 yielded mediocre and short-term control at the rates of 0.25 and 0.5 lb/acre (0.26 and 0.56 kg/ha), while level of control and persistence greatly increased as the dosages were increased to 1.0, 2.0 and 4.0 lb/acre (1.12, 2.24 and 4.48 kg/ha). The 1.0 and 2.0 lb/acre rates yielded almost 100% control for 4 weeks and the 4.0 lb/acre rate yielded control (99%) for 49 days or longer. A flowable concentrate preparation (BSP-2) yielded complete initial and persistent control of larvae for 14-21 days at 2.0, 4.0 and 5.0 lb/acre (2.24, 4.49 and 5.6 kg/ha). Granular formulations of B. sphaericus 2362 (ABG-6185) were also evaluated at 2.5, 5.0, 7.5, 10.0 and 20.0 lb/acre (2.8, 5.6, 8.4, 11.2 and 22.4 kg/ha) of the granules. Some of the formulations were more active than the others, yielding excellent initial and persistent control (80% +) for 14-21 days with one treatment.

Animals↗