Sex Of Larvae Research Articles

Toxicity of insecticides to Plutella xylostella (L.) as influenced by the sex of larvae

Toxicity of insecticides to Plutella xylostella (L.) as influenced by the sex of larvae

Photogenic Flies—A review of Chyb and Gompel's Atlas of Drosophila Morphology: Wild-type and Classical Mutants

Photogenic Flies—A review of Chyb and Gompel's Atlas of Drosophila Morphology: Wild-type and Classical Mutants

Larval sex identification in the paper wasp Polistes dominulus (Vespidae, Hymenoptera)

Identifying the sex of larvae is important in social Hymenoptera. Until now for Polistes wasps it has been necessary to genotype larvae at microsatellite loci, and assign their sex based on homozygosity at these loci. In our study on the paper wasp Polistes dominulus we have found morphological differences between larval sexes that can be used for larvae from the 3rd instar on to easily and cheaply identify larval sex: the external gonopore and the shape and size of larval gonads. The robustness of these indicators was supported by genotype data at four microsatellite loci. Using gonopore and gonad features for sex assignment will assign diploid males as males, unlike techniques based on genetic loci or chromosomes.

No evidence of androgenic hormone from the testes of the glowworm, Lampyris noctiluca

The widely accepted concept, stating that insects have no true sex hormones, and that primary as well as secondary sex characteristics are controlled by the genetic inventory of each single cell, is challenged by the report of Naisse, J. [1966a. Contrôle endocrinien de la différenciation sexuelle chez l’Insecte Lampyris noctiluca (Coléoptère Malacoderme Lampyride). I. Rôle androgène des testicules, Arch. Biol. Liège, 77, 139–201] on the discovery of an androgenic hormone in the glowworm, Lampyris noctiluca. This case is of special interest, since it may point to an ancestral mode of sex differentiation in arthropods, considering that androgenic hormones have been discovered and characterized in crustaceans. With the intention to further characterize the androgenic hormone in the glowworm, and to establish a bioassay, we tried to repeat Naisses’s transplantation experiments, according to which, androgen producing testes implanted into female larvae should masculinize the female’s gonads and all other female features of the sexually strongly dimorphic pupae and beetles. We found, however, that larval development of the glowworm proceeded differently than reported by Naisse, and that sexing of larvae was not possible. Therefore, “blind” transplantations had to be performed. The results of our experiments showed, however, unequivocally, that an androgenic hormone, alledgedly synthesized by the apical tissue of larval testes, was not involved in sex differentiation. We found, that in transplants, where testes and ovaries were even located closely to each other, both matured and formed spermatozoa in the testes and vitellogenic oocytes in the ovaries. Masculinization of ovaries was never observed, and the sex of the recipient was always in accordance with the sex of its own gonads. We therefore conclude that Lampyris noctiluca does not synthesize an androgenic hormone in the larval testes, and that sex differentiation is probably regulated as in other insect species. (The apical testis tissue of the glowworm was previously shown to represent progenitors of spermatogonial cyst cells [Balles, S., Maas, U., Sehn, E., Dorn, A., 2002. Testis differentiation in the glowworm, Lampyris noctiluca, with special reference to the apical tissue. J. Morphol. 251, 22–37].)

Analysis of Trophic Indices in Gypsy Moth ( Lymantria dispar L.) Larvae from Two Geographic Populations

Specific features of larval feeding in two geographic populations of the gypsy moth are considered. It is shown that in larvae reared on an artificial diet, trophic indices depend on several factors, including the age and sex of larvae and the food plant on which the parental generation developed in nature. It is shown that larval micropopulations belonging to the same geographic population but feeding in nature on different plant species differ from each other to a greater extent than those of different geographic populations feeding on the same species.

Absence of sex-differential brood raising by workers in Diacamma sp. from Japan

To optimally allocate resources between workers, reproductive females, and males, ant workers have to be able to identify the sex of larvae and raise them differently. The ability of workers to discriminate between the sexes in the brood was tested in colonies of queenless ponerine ants, Diacamma sp., from Japan. The ratio of male eggs in the egg pile was increased experimentally. This manipulation resulted in a corresponding increase in the ratio of adult males, suggesting that Diacamma workers do not raise the sexes differently.

Daily changes in the cold sensitivity ofGalleria mellonellalarvae

Abstract Cold sensitivity of last instar Galleria mellonella larvae was investigated by measuring (1) the number of extra‐larval molts, (2) the number of larvae retaining ability to secrete silk, and (3) the number of larvae showing arrested development, after 2 h exposure to 0°C. Daily changes refer to the production of extra‐larval molts only, which are not generated by photoperiod. These variations result from (a) the time of day at which larvae molt from the penultimate into the last larval instar, (b) the sex of larvae, (c) the age of larvae at cooling, and (d) the time of day at which cooling stress was given. The time of molting into the last larval instar determines the sex ratio in the group of molting insects. Because females show higher sensitivity to cooling than males, the general sensitivity of an examined group of larvae is influenced by the time of molting, and sensitivity is increased when females are in majority. The course of the daily changes in the sensitivity to cooling results, in t...

Strongyloides ransomi: Factors Influencing the In vitro Development of the Free-Living Generation

Among the progeny of parasitic females of Strongyloides ransomi, ransomi, males did not appear in significant numbers until the 7th week of infection in cases of simple infection, and until the 3rd week of infection in cases of multiple infection. The appearance of males was attributed to the effect of host immunity, the physiological ageing of the parasitic females, or both. Type of culture substrate and other cultural conditions did not influence the percent of larvae developing into males. Sex of larvae was determined prior to hatching, probably during oogenesis or embryogenesis. Culture conditions influenced the direction of development of female larvae. An initial pH below 5.9 or above 7.2 favored differentiation of larvae into infective larvae, whereas, intermediate initial pH levels favored development of free-living females. Baby pig substrate, autoclaved substrate, and substrate washed free of soluble chemicals (adverse cultural conditions) promoted differentiation toward infective larvae. Adult pig substrate, nonautoclaved substrate and unwashed substrate promoted differentiation toward free-living females. In general, adverse conditions inside the host and favor an indirect life cycle.

The Development and Life History of the False Root-Knot Nematode, Nacobbus Serendipiticus

The development and life history of Nacobbus serendipiticus was studied from the egg to maturity and the early stages recorded by cinematography. There are four moults, the first in the egg. The four larval stages are described and their behaviour in relation to tomato roots. The sex of larvae can be determined at the end of the third stage by the development of the gonads. Damage to the host roots caused by the larvae feeding and invading is followed by necrosis of cortical cells. Galls occur only in association with adult females; they contain a spindle-shaped mass of small cells in which starch grains were found. Of 25 plant species tested for susceptibility, mature females were recovered from eight. The nematodes can survive the winter in England but are probably not indigenous.

Morphogenesis of Testes and Ovaries in the Boll Weevil, Anthonomus grandis (Coleoptera: Curculionidae)1

The testes of Anthonomus grandis Boheman develop during larval stages from imaginal discs of primordial germ cells located in lobes of adipose tissue at about the 5th–7th abdominal segment. They are large enough to be seen through the integument during the second instar. Ovarial growth is somewhat slower, but the ovaries can be seen easily in third-instar larvae. The sex of larvae can be determined visually. Mitotic division of spermatogonia and oogonia occurs during larval development, and the male germ cells prepare for meiotic divisions during the prepupal stage. The divisions were detected immediately after pupation. The change from larval growth to metamorphosis into adult structures was thus correlated with a change in the testes from mitotic multiplication to meiotic maturation.