• R S Prasad

      Articles written in Proceedings – Animal Sciences

    • Behavioural analysis of feeding and reproduction in haematophagous insects

      R S Prasad

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      The only common factor the haematophagous arthropods share among themselves is the blood sucking habit. This habit which ties them down to an unnatural assemblage, confers on them certain parallelism even in their natural diversities. Behavioural activities of haematophagous arthropods, like those of many other animals, centre around 3 major aspects: searching for a suitable host and feeding on it; meeting of the sexes and finding a suitable place for oviposition.

      Behaviour of blood sucking insects assume importance because these insects act as vectors of many blood-borne infections of man and animals. In this article, feeding and reproductive behaviours of haematophagous insects are analysed on certain hierarchy of events like: motivation; search and consummation.

    • Seasonal prevalence and host visitation ofMansonia mosquitoes in Trivandrum city with a note on mite infestation

      B Ayyachamy Daniel Cheriyan Thomas K Kalyanaraman R S Prasad

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      A study relating to seasonal prevalence and host visitation ofMansonia mosquitoes in Trivandrum city was carried out between August 1984 and July 1985. The area chosen was the one which is a perennial breeding source forMansonia mosquitoes. OnlyMansonia uniformis andMansonia annulifera were prevalent in this area of which the former was found to be the predominant species. Decrease in the number ofMansonia annulifera from the survey conducted during the previous year may be due to the disappearance ofPistia stratiotes and its replacement bySalvinia auriculata. Rainfall and temperature are the two important environmental factors which influence the number ofMansonia mosquitoes visiting the host. The maximum number of adults ofMansonia uniformis was collected during February to June 1985. No swarm ofMansonia uniformis was encountered during the present study, however, males were found to wait and mate with the resting as well as blood fed females in the vicinity of the host. Both sexes ofMansonia mosquitoes were parasitized byArrenurus and limnesiid species of water mites. Maximum parasitization was seen during July 1985.

    • Influence of certain physico-chemical factors upon the larval population ofMansonia mosquitoes (Culicidae: Diptera) in Trivandrum city, India

      P S Sasikumar Prema Suryanarayanan Cheriyan Thomas K Kalyanaraman R S Prasad

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      A year round study was conducted in Trivandrum city during the period of March 1984 to February 1985 to elucidate the relation between certain physico-chemical factors and seasonal density ofMansonia larvae (Culicidae: Diptera).Mansonia uniformis was found to be the predominant species during this period, whereasMansonia annulifera was less than 10% of the totalMansonia collected. The period of high prevalence was found to be January–March. Out of the 6 physico-chemical factors studied Na+, K+, and pH showed statistically significant correlation with the larval density, while Ca++, Mg++ and rainfall showed no significant relation.

    • Nutrition and reproduction in haematophagous arthropods

      R S Prasad

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      Hosts of haematophagous arthropods range from amphibians to mammals. Blood meal is essential for egg production. Quantity and quality of ingested blood are important in realization of optimum reproductive potentials. In terms of egg production, the lowest nutritive value is for human blood. This inequality is probably based on differences in proteins and their constituent amino acids. Carbohydrates in the diet have no direct contribution to reproduction. Very little is known about sterol, lipid, vitamin and salt requirements for reproduction. In the mosquitoAedes aegypti some substance from the blood meal is thought to initiate vitellogenesis and is sustained by a complex hormonal mechanism in which median neurosecretory cells, corpus allatum, fat body and ovary participate. Mechanical stimuli from gut distension also has a role in hormone induction.

      Autogenous egg production seen in many dipterans is controlled both by the nutrition of the immature stages and genetic mechanisms.

      Quantity and the rate of utilization of the ingested blood decide the frequency of host visitation and feeding. Vertebrate blood sera contain substances which stimulate (secretogogue) as well as inhibit digestion. Nutrition plays some role in male maturation in insects, though not in spermatogenesis. In many ticks even spermatogenesis is influenced by adult blood meal.

    • Host dependency among haematophagous insects: A case study on flea-host association

      R S Prasad

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      Obligatory haematophagy is the end result of long standing interspecific associations. Present day specificities to host, blood meal and physiological stage of the host are all offshoots of the primitive interspecific associations. The cause/effect relationship of these dependencies and specificities are probably based on the route through which haematophagy evolved in different groups of insects.

      In the present analysis, flea-host association is taken into consideration. It is possible to find an array of host relationships ranging from promiscuous and catholic host associations to strict ones. In general 3 categories may be recognized. In fleas likeXenopsylla cheopis a utilizable protein in an optimum concentration gives the necessary stimuli for maturation (Cheopis-type), while in a second group the stimuli is provided by certain circulating hormones of the host (Cuniculi-type) as seen in rabbit fleaSpitopsyllus cunicuti and in a third grnup (Monositus-type) a priming period characterized by tissue fluid feeding and neosomy is necessary before whole blood diet can stimulate maturation as exemplified byTunga spp.

      It appears that vertebrate associations of Siphonaptera initiated as adaptations to the nest microhabitat and haematophagy and adaptations to physical/chemical factors of epidermal habitat being subsequent developments.

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