ABSTRACT
Aim: To determine species distribution of mosquitoes in coastal brackish wetlands and in paddy field area of Kerala along with the effect of increased salinity on the development and survival of major Japanese encephalitis vectors. Methodology: Mosquito survey was carried out in different sites of coastal brackish water as well as in paddy fields of Alappuzha district. First instar larvae were reared until adult emergence at different constant saline water. Each individual was monitored daily for mortality. Larvae were placed in a plastic container with 200 ml distilled water, which served as controls. Counts of larvae, pupae and adults were recorded every 24 hr up to adult emergence. Results: The collected mosquitoes were Culex tritaeniorhynchus, Cx. gelidus, Cx. sitiens, Cx. quinquefasciatus, Cx. bitaeniorhynchus and Anopheles vagus. During summer season, Cx. sitiens (92.85%) was the predominant species followed by Cx. tritaeniorhynchus (2.97%) and Cx. gelidus (2.25%). In saline tolerant study, the maximum adult emergence occurred at 5 parts per thousand. The number of larvae surviving till adult stage decreased progressively with increased salinity. The wing size decreased significantly with increasing salinities, except those reared in 5ppt. Interpretation: The present study demonstrates that these three mosquitoes have the ability to oviposit and breed in brackish water. The study also reveals the health risks associated with vector mosquitoes developing and their frequency of abundance in brackish water, particularly in the context of rising sea levels due to global warming.
ABSTRACT
The ovary of Haemaphysalis bispinosa was of panoistic type with asynchronous development of oocytes. The wall of the ovary was composed of a layer of epithelial cells to which the oocytes were attached by means of pedicel cells with elongated nucleus. The oocytes were classified into stages I to V based on morphologic characteristics like size and shape, presence / absence of germ vesicle, cytoplasmic appearance, presence or absence of yolk granules and presence of chorion. Day wise changes were in the form of occurrence of oogonia from partially fed upto day zero of engorgement, presence of all stages of oocytes on day one and two after engorgement and onset of degenerative changes in oocytes from day three onwards. Degeneration was complete on day eight with the appearance of polymorphism, vacuolation, cytoplasmic blebbing and autophagic activity in oocytes.