Structure and ultrastructure of spermatozoa of Chrysomya megacephala (Diptera: Calliphoridae)

Impact of paternal transmission of gamma radiation on reproduction, oogenesis, and spermatogenesis of the housefly, Musca domestica L. (Diptera: Muscidae)

PURPOSE

This study aimed to investigate the impact of gamma radiation of Musca domestica males (resulted from irradiated pupae) crossed with unirradiated females on fecundity, egg hatchability, adult emergence, sex ratio, sterility, in addition to reproductive development at the level of oogenesis and spermatogenesis compared to unirradiated group.

MATERIAL AND METHODS

The housefly, M. domestica pupae were exposed to three sublethal doses of 5, 10, and 15 Gy.

RESULTS

Fecundity was severely reduced particularly in F2 (11.33 ± 1.528; 7.33 ± 1.115 eggs/♀) and F3 (9.0 ± 1.00; 4.67 ± 1.115 eggs/♀) for doses of 10 and 15 Gy, respectively, compared with (52.0 ± 1.4 eggs/♀) for the control. Data revealed latent dose- and generation-dependent reduction in egg hatchability. Hatchability percentages reduced from 93.59 for the control to 10.07 (F1), 8.09 (F2), and 8.34 (F3) when the highest radiation dose 15 Gy was applied. Irradiation induced paternal deleterious substerility effects. Irradiation with 15 Gy induced substerility that reached about 97.0% in F2 and F3 generations. A significant (P < 0.05) reduction of the mean numbers of adult emergence was remarkably detected in the F1, F2, and F3 generations. Applied gamma doses did not affect the male to female ratio in the Parental or F1 generations. However, the F2 and F3 generations did show changes to the sex ratio with males occurring more frequently than females. This trend became more pronounced as dose increased. Ultrastructural examinations exhibited unusual damage and malformation either for males or female reproductive organs.

CONCLUSION

The obtained results clearly show that gamma radiation of M. domestica irradiated as pupae induced considerably visible impact on tested biological aspects and reproductive potential.

Morphology and ultrastructure of the spermatozoa of Lonchoptera lutea Panzer, 1809 (Diptera: Lonchopteridae)

Lonchoptera lutea males produce giant spermatozoa that are more than 2000 μm long and 1.4 μm wide. Unlike the typical brachyceran spermatozoon, they have a highly asymmetrical cross-section with only a single, albeit very large, mitochondrial derivative and a pair of massive accessory bodies, one of which extends throughout the entire length of the sperm tail. The accessory bodies consist of an electron-dense matrix in which numerous peculiar electron-lucid substructures are embedded. In the mated female, the giant spermatozoa are found inside two tubular spermathecae which are also extremely long, measuring 4000 μm or more.

The uses of Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) in forensic entomology

Chrysomya megacephala (Fabricius, 1794) occurs on every continent and is closely associated with carrion and decaying material in human environments. Its abilities to find dead bodies and carry pathogens give it a prominence in human affairs that may involve prosecution or litigation, and therefore forensic entomologists. The identification, geographical distribution and biology of the species are reviewed to provide a background for approaches that four branches of forensic entomology (urban, stored-product, medico-criminal and environmental) might take to investigations involving this fly.

Giant spermatozoa of Diasemopsis (Diopsidae, Diptera) - Structural, ultrastructural and functional aspects

The spermatozoa of Diasemopsis comoroensis and Diasemopsis meigenii differ from the conventional brachyceran type in several respects. Not only are they very long but they are also extraordinarily wide, especially at the very end of the tail. The latter is effected by two cellular components: oversized mitochondrial derivatives and a prominent central band, which is a peculiar structure not known from any other spermatozoa. Based on its position with respect to the other organelles and its origin during early spermiogenesis, the central band is interpreted as a derivative of the centriolar adjunct material. Like the axoneme, the mitochondrial derivatives and the central band extend through the entire length of the spermatozoon tail. The spermatozoon tail is helical and can be coiled up into a tight cone-shaped spiral with a peculiar corkscrew shaped end portion. The potential adaptive significance of these features and their coevolution with the morphology of the female's multi-chambered ventral receptacle are discussed, as are sperm competition and cryptic female choice.

Do male secondary sexual characters correlate with testis size and sperm length in the small hairy maggot blowfly?

The phenotype-linked fertility hypothesis proposes that secondary sexual characters (SSCs) advertise a male's fertility to prospective mates. However, findings from empirical studies attempting to test this hypothesis are often ambivalent or even contradictory, and few studies have simultaneously evaluated how both morphological and behavioural SSCs relate to ejaculate characteristics. Males of the small hairy maggot blowfly, Chrysomya varipes, possess conspicuous foreleg ornaments and display highly stereotyped courtship behaviour. These traits are favoured by females during pre-copulatory mate choice, but it remains unknown whether they correlate with post-copulatory traits expected to influence male fertility. The aim of this study was to investigate whether male courtship and ornamentation correlate with testis size and sperm length in C. varipes. We found that males investing more in courtship had bigger testes, and males with more extensive foreleg ornamentation released sperm with longer tails. Based on the assumption that larger testes enable males to produce more sperm, and that sperm with longer tails have greater propulsive force, our findings suggest that more vigorous and more ornamented males may be more fertile. These findings lend support to the phenotype-linked fertility hypothesis. However, a complete test of this hypothesis will require evaluating whether testis size and sperm length influence male fertilisation ability, as well as female fecundity and/or fertility.

Ultrastructure of the spermatozoa of Psammotettix striatus (Linnaeus) and Exitianus nanus (Distant) (Hemiptera: Auchenorrhyncha: Cicadellidae: Deltocephalinae)

Previous studies of insect spermatozoa indicate that these specialized cells have undergone significant morphological evolution and exhibit traits useful for reconstructing phylogenetic relationships. Although leafhoppers (Cicadellidae) are among the largest and most economically important insect families, few comparative studies of their spermatozoa have been published. Here, the ultrastructure of mature spermatozoa of two leafhoppers Psammotettix striatus (Linnaeus) and Exitianus nanus (Distant), representing two different tribes of the largest leafhopper subfamily, Deltocephalinae, was examined by light and transmission electron microscopy. The shape and ultrastructure of spermatozoa of the two species are very similar to those of other Cicadellidae as well as other Auchenorrhyncha, comprising a conical acrosome invaginated to form a subacrosomal space, a filiform homogeneously condensed nucleus, a lamellate centriolar adjunct connecting the nucleus with the mid-piece/flagellum, a long flagellum with a 9 + 9 + 2 axoneme pattern and two symmetrical mitochondrial derivatives with an orderly array of peripheral cristae, and two drop-shaped accessory bodies. They may be distinguished by the size of the sperm, and the shape of the nucleus, accessory bodies, and paracrystalline region of mitochondrial derivatives. The fine morphology and ultrastructure of spermatozoon in P. striatus and E. nanus are illustrated, along with a brief discussion of the implications for classification and phylogenetic analyses of the subfamily.

Overview on spermatogenesis and sperm structure of Hexapoda

The main characteristics of the sperm structure of Hexapoda are reported in the review. Data are dealing with the process of spermatogenesis, including the aberrant models giving rise to a reduced number of sperm cells. The sperm heteromorphism and the giant sperm exceeding the usual sperm size for length and width are considered. The characteristics of several components of a typical insect sperm are described: the plasma membrane and its glycocalyx, the nucleus, the centriole region and the centriole adjunct, the accessory bodies, the mitochondrial derivatives and the flagellar axoneme. Finally, a detailed description of the main sperm features of each hexapodan group is given with emphasis on the flagellar components considered to have great importance in phylogenetic considerations. This study may be also useful to those requiring an introduction to hexapod reproduction.

Morphological and cytochemical aspects of spermatozoa in the genus Cochliomyia (Diptera: Calliphoridae)

The objective of this study was to characterize, structurally and ultrastructurally, the spermatozoa of the screwworm flies Cochliomyia hominivorax and Cochliomyia macellaria. To visualize the ultrastructure of microtubules and identify basic proteins, techniques such as the tannic acid fixation and the cytochemical method of ethanolic phosphotungstic acid (EPTA) were used. These methods of fixation are important because they reinforce the evidence of the protofilaments present in the microtubular wall and identify basic proteins, respectively. With the tannic acid fixative it was possible to observe a significant number of microtubules in the cell cytoplasm during spermiogenesis. Microtubules were observed in all regions of spermatids (head, 'overlap' zone and tail). The EPTA technique highlighted the presence of basic proteins on the border of the nucleus and nuclear envelope in the two species analyzed, and in the centriolar adjunct and on the border of mitochondrial derivatives in C. macellaria. The axoneme is of a conventional insect type with a 9 + 9 + 2 microtubular arrangement and the spermatozoa of C. hominivorax and C. macellaria are similar to those described for other Brachycera. The spermatozoa are long and thin in these two species, ∼190 µm in length, of which the head region measures ∼26 µm in C. hominivorax and 29 µm in C. macellaria. A polymorphism was observed in C. hominivorax and C. macellaria. These features are consistent with the structural diversity of the dipteran spermatozoa, constituting an essential tool for understanding the complex variations found in the Diptera order.

Reproductive Organ of Blow Fly, Chrysomya megacephala (Diptera: Calliphoridae): Ultrastructural of Testis

This work presents the ultrastructure of testis of the medically important blow fly, Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) using light microscopy and electron microscopy. Reproductive organ of males was dissected to determine the testis in the pupal stage, 3-day-old flies and 7-day-old flies and observed under scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM displayed a smooth surface which is occasionally penetrated by tracheoles. TEM of the testis in the pupal stage presents the thick testis wall covering underdeveloped cells containing a variable size of an electron-dense globule. For the 3-day-old males, the testicular wall is formed by an external layer, a peritoneal sheath, a muscular layer, a basement membrane, and a follicular epithelium. Follicular epithelium presented developing spermatozoa. Regarding the 7-day-old males, development of spermatozoa is apparent, displaying nucleus, centriolar adjunct, axoneme, and mitochondrial derivatives, with the 9 + 9 + 2 microtubule pattern of axoneme.