Anatomical Indicators for Assessing Age of Mosquitoes:1 Changes in Ovarian Follicles

A study of the age-dependent changes in the ovarioles and the age structure of a population of adult females of Anopheles gambiae in the Amani hills of north-eastern Tanzania was undertaken using the ovarian oil injection technique. The greatest difficulties encountered in accurately determining the age of members of this species are due to small size and the low parity diagnostic index of the ovary, which decreased in successive gonotrophic cycles and could drop to zero even in the first cycles. Additional information can be obtained from basal bodies, groups of six to eight cells in the calyx wall enclosed by the end of the ovariolar sheath. The possibility exists of their use for age grading of mosquitoes. The mean age of the population during the study, which was carried out in the rainy season, was rather low. The oldest were individuals that had completed four ovipositions. Among the mosquitoes infected with sporozoites were females that had completed between > 2 and > 4 ovipositions.

Section: Discussionmentioning

confidence: 99%

The ovariole structure of Anopheles gambiae (Diptera: Culicidae) and its use in determining physiological age

Hoc

Wilkes

1995

“…Ovarioles of Culex annulirostris Skuse were stained with Giemsa, which made dilatations more visible; they were then carefully teased apart with fine-tipped needles and/or forceps or electrolytically sharpened tungsten wire needles (Kay, 1979); the ovariole wall was carefully removed to expose the intima in the region between the most developed follicle and the calyx. Dilatations can be counted under a binocular microscope (with x 12-48 magnification) (Rosay, 19696) when the intima has contracted after oviposition but before the next developed egg has grown to full size, i.e. when the egg is between Christophers' (1911) and Mer's (1936) stages II and IV.…”

Section: Criteria Used For Age-gradingmentioning

confidence: 99%

Age-grading methods in adult insects: a review

Tyndale-Biscoe

1984

101

The literature on age-grading techniques of adult insects, published since 1968, is reviewed. The techniques described include those which deal with changes in the reproductive system, as well as somatic changes which take place with age. They also include techniques based on changes induced by wear and tear. Follicular relics found in different orders of insects are described, and their origin, fate and relative usefulness in age-grading studies are discussed. Attention is drawn to the formation of anomalous, or aberrant dilatations, particularly ones formed as a result of follicle resorption. The suitability of the various techniques to the study of different insect species is compared, and the advantages of using more than one type of age-grading method in the study of one species are discussed. Enough detail of each technique is given to permit field workers to choose and apply the technique most suitable for the study of the insect of their choice, and for the degree of accuracy required by them. Lists of species which have been studied by particular age-grading techniques, or combinations of them, are given. Finally, examples are cited of the types of problems entomologists have sought to solve, often successfully, using age-grading methods.

“…The pioneering work on age determination in mosquitoes is reviewed by Detinova (1962). Subsequent studies on age determination in female Diptera include tsetse flies (Saunders, 1962), mosquitoes (Giglioli, 1965;Rosay, 1969), Fannia canicularis (L.) and other Cyclorrhaphous Diptera (Anderson, 1964), the housefly (Smith, 1968), face fly (Miller & Treece, 1968), bushfly (Tyndale-Biscoe & Hughes, 1969) and the sheep blowfly (Clift & McDonald, in press). In each of these studies, changes in the female reproductive system were used as a basis for ageing.…”

Section: Introductionmentioning

confidence: 99%

A method of age determination in Lucilia cuprina (Wied.) (Diptera, Calliphoridae) using cyclic changes in the female reproductive system

Vogt

Woodburn

Tyndale-Biscoe

1974

The stage of egg formation and density of follicular relics enable Lucilia cuprina (Wied.) females to be sorted into 16 ovarian stages, covering the period from emergence to the beginning of the fourth ovarian cycle. The correspondence between the actual age of a fly and its stage of ovarian development was determined at constant temperatures. Where developmental delays were absent, " reproductive age" gave reliable estimates of actual age under both constant and fluctuating temperature regimes. In the field protein shortages and lack of oviposition sites may prolong the time required to complete each ovarian cycle, and flies will be older than their ovaries would indicate. In practice the ovarian stages described provide estimates of minimum age for L. cuprina females.