Sperm ultrastructure of the European hornet Vespa crabro (Linnaeus, 1758) (Hymenoptera: Vespidae)

Sperm ultrastructure of Pochazia shantungensis (Chou & Lu) and Ricania speculum (Walker) (Hemiptera, Ricaniidae) with phylogenetic implications

The sperm ultrastructure of two ricaniid species, Pochaziashantungensis (Chou & Lu) and Ricaniaspeculum (Walker), was investigated using light and transmission electron microscopy. Both species have monoflagellate sperm, the shape and ultrastructure of the mature spermatozoon of these two species are similar in morphology, and 128 spermatozoa are organized into sperm bundles with their heads embedded in a homogenous matrix forming the spermatodesmata. The individual sperm is filiform and includes the head, neck and flagellum. The head is needle-like, with a bilayer acrosome and an inferior elongated nucleus which is formed of homogeneously compact and electron-dense chromatin. The neck region is indistinct and is comprised of the centriole and centriole adjunct with a homogeneous dense substance. The long flagellum has the typical 9 + 9 + 2 axoneme microtubule pattern and two symmetrical mitochondrial derivatives with an orderly array of cristae flanking both sides, and a pair of well-developed fishhook-shaped accessory bodies. Current evidence shows that ricaniid species have D-shaped mitochondrial derivatives in cross-section and a serrated electron-dense region. The phylogenetic relationship of Fulgoroidea with other superfamilies in Auchenorrhyncha is briefly discussed.

Sperm morphology of Elasmus polistis Burks, 1971 (Hymenoptera: Chalcidoidea: Eulophidae)

The sperm morphology of the parasitoid Elasmus polistis (Eulophidae) has been investigated with light and transmission electron microscopy. The sperm were filiform and spiraled, with 165.6 (± 4.6) μm in length, and showed a distinctive head, formed by a one-layered small acrosome and a nucleus, and a flagellar region. An extracellular sheath from which many long filaments radiated out covered the acrosome and part of the nucleus. The spiral nucleus, with 24.1 (± 1.3) μm in length, was filled with homogeneously compact chromatin. In the nucleus-flagellum transition, the centriole adjunct extended posteriorly from the nuclear base in a spiral around the basal body, which has two central microtubules, and axoneme for approximately 1.1 μm. The two mitochondrial derivatives began roughly at the same level and at the base of the centriole adjunct. In cross-section, they were symmetrical, with a slightly oval shape and a smaller diameter in comparison to the axoneme. The latter, also spiraled, consisted of 9 + 9 + 2 microtubules that was formed from the basal body situated just below and aligned with the nucleus. The E. polistis sperm showed the same basic structures and morphological characteristics as observed in other Chalcidoidea. However, it was possible to distinguish the sperm of this species from those of other Eulophidae by (i) the long length of the centriole adjunct on the flagellum, and (ii) the presence of two central microtubules within the basal body. The sperm characteristics suggest that Eulophidae is closely related to Trichogrammatidae and both families are more similar to Eurytomidae, Pteromalidae, and Torymidae than Agaonidae.

Comparison of reproductive traits of foundresses in a native and an invasive hornet in Europe

The population dynamics of annual social hymenoptera such as vespids depend largely on the fertility of the foundresses, which, in turn, is a key factor in the context of biological invasions. The native European hornet Vespa crabro (Vc) and the invasive Asian hornet Vespa velutina (Vv) have generally similar ecological traits, e.g. nesting and feeding habits, although they differ in colony size, which is higher in Vv. Furthermore, in contrast to Vc, Vv is more specialized in its predatory habits, intensively hunting honey bees at the hive. Comparing the morphological and reproductive traits of two closely related species occupying the same ecological niche, one of which is a native species and the other an alien, can help us to gain an understanding of the invasion process. To this end, we here compare reproductive (ovarian size and maturation, fat level, spermatheca size and sperm stock, fecundity) and morphological traits (head size, weight) of the foundresses of these two hornet species. We observed that ovarian maturation began approximately one month earlier in Vv than in Vc, and that the fat level in the former was lower. We found twice the number of sperm in the mated foundresses of Vv than in those of Vc (more than 100 × 10³ and less than 50 × 10³ sperm, respectively), in a 16% smaller spermatheca in Vc. Furthermore, the sperm of Vv was found to be 65% shorter than that of Vc. The precocity and higher potential fecundity of Vv queens may have favoured this species over Vc in terms of predatory behaviour, and thereby contributed to its invasiveness.

Sperm morphology of Muscidifurax uniraptor (Hymenoptera: Chalcidoidea: Pteromalidae)

Sperm morphology of the parasitoid Muscidifurax uniraptor was investigated under light and transmission electron microscopy. M. uniraptor sperm are filiform, spiraled, approximately 150 μm in length, with a distinctive head, hooded by an extracellular sheath and a flagellum. This extracellular layer, from which many filaments radiate, measures approximately 90 nm in thickness and covers a small acrosome and the anterior nuclear region. The acrosome is composed of an acrosomal vesicle and a perforatorium with its base inserted in the nuclear tip. The nucleus is filled with homogeneously compacted chromatin. The centriolar adjunct extends towards the anterior portion in a spiral around the nucleus for 3.5 μm in length. The two mitochondrial derivatives begin exactly at the centriole adjunct base and, in cross-section, have a circular shape with equal areas that are smaller than the axoneme diameter. It is coiled, with 9 + 9 + 2 microtubules and begins from the centriole, just below the nuclear base. The axoneme is connected to the mitochondrial derivatives by two small irregularly shaped masses. Between the derivatives and the axoneme, the 'center-flagellar material' is observed. Overall, these characteristics are recognized in other Chalcidoidea, especially in the eurytomids, but together they form a set of species-specific data.

Ultrastructural features of spermatozoa and their phylogenetic application in Zaprionus (Diptera, Drosophilidae)

The genus Zaprionus consists of approximately 60 species of drosophilids that are native to the Afrotropical region. The phylogenetic position of Zaprionus within the Drosophilidae family is still unresolved. In the present study, ultrastructural features of spermatozoa of 6 species of Zaprionus as well as the species Drosophila willistoni and Scaptodrosophila latifasciaeformis were analyzed. The ultrastructure revealed that the species have the same flagellar ultrastructure. Two mitochondrial derivatives, one larger than the other, close to the axoneme were present, primarily in D. willistoni (subgenus Sophophora). Except for Z. davidi and Z. tuberculatus, the analyzed species had paracrystalline material in both mitochondrial derivatives. Moreover, the testes showed 64 spermatozoa per bundle in all of the species. In the cluster analysis, 6 Zaprionus species were grouped closely, but there were some incongruent positions in the cladogram. The results indicated that sperm ultrastructure is an important tool for elucidating the phylogeny and taxonomy of insects.

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.

Sperm Bundles in the Seminal Vesicle of the Crematogaster victima (Smith) Adult Males (Hymenoptera: Formicidae)

This study establishes the presence of spermatodesm in the seminal vesicles of sexually mature males of Crematogaster victima (Smith). In this species, the spermatozoa are maintained together by an extracellular matrix in which the acrosomal regions are embedded. This characteristic has not yet been observed in any other Aculeata. However, the sperm morphology in this species is similar to that described for other ants. The spermatozoa measure on average 100 μm in length, and the number of sperm per bundle is up to 256. They are composed of a head formed by the acrosome and nucleus; this is followed by the flagellum, which is formed by the centriolar adjunct, an axoneme with a 9 + 9 + 2 microtubule pattern, two mitochondrial derivatives, and two accessory bodies. The acrosome is formed by the acrosomal vesicle and perforatorium. The nucleus is filled with compact chromatin with many areas of thick and non-compacted filaments. Both mitochondrial derivatives have the same shape and diameters. The presence of sperm bundles in sexually mature males differentiates C. victima from other ants; however, the similarities in the sperm ultrastructure support the monophyly of this insect group.

[Morphological characteristics and cryodamage of Chinese tree shrew (Tupaia belangeri chinensis) sperm]

The tree shrew (Tupaia belangeri chinensis) is a small non-rodent mammal, which is a relatively new experimental animal in medicine due to its close evolutionary relationship to primates and its rapid propagation. Sperm characteristics and cryopreservation in the tree shrew were the main contents of our spermatological research. Epididymal sperm were surgically harvested from male tree shrews captured from the Kunming area. The rate of testis weight to body weight was (1.05±0.07)%, volume of both testis was (1.12 ± 0.10) mL, total sperm from epididymis and vas deferens were 2.2-8.8×10(7), and sperm motility and acrosome integrity were (68.8 ± 3.9)% and (90.0 ± 2.1)%, respectively. Sperm ultrastructure of the tree shrew was examined by scanning electron microscopy and transmission electron microscopy. Tree shrew sperm had a round or oval shaped head of approximately 6.65×5.82 μm, and midpiece, principal piece, tail, and total sperm lengths were 13.39, 52.35, 65.74, and 73.05 μm, respectively. The mitochondria in the midpiece consisted of approximately 48 gyres and had a 9+9+2 axonemal pattern. After freezing and thawing, sperm showed partly intact acrosomes and plasma membrane defects, and sperm breakages, twists, and swellings were found. The tree shrew had similar ultrastructure with other mammalians except for the mitochondria number and the sperm size. Ultrastructural alteration is still the main cause resulting in poor sperm after cryopreservation.

Ultrastructure of spermatozoa in two solitary bee species with an emphasis on synapomorphic traits shared in the family apidae

Morphology of spermatozoa in bees has provided promising results for phylogenetic analyses. In this work, the structure and ultrastructure of spermatozoa from Thygater (Thygater) analis and Melitoma segmentaria were characterized and the synapomorphies shared in the family Apidae are discussed. In these species, spermatozoa bundles which are undone in the seminal vesicle possess, on average, 50 cells. Spermatozoa consist of a head and a flagellar region. The head includes an acrosome containing the perforatorium, covered by the acrosomal vesicle and a nucleus. The flagellum is formed by two mitochondrial derivatives, which are asymmetric in diameter and length, with one centriolar adjunct, one axoneme (9 + 9 + 2), and two accessory bodies. In cross section the centriolar adjunct is asymmetric and the accessory bodies are triangular in shape. In the distal region of the flagellum, the derivative terminates before the axoneme and the small derivative terminates first. The axoneme is gradually disorganized and the accessories microtubules are the last to terminate. In these two species, spermatozoa share diverse synapomorphies with those of other bee species previously described in the literature, which allows for the establishment of a morphological pattern for spermatozoa of the family Apidae.

The descriptions of new microanatomical structures of the male reproductive system and sperm of Myschocyttarus cassununga (Hymenoptera: Vespidae)

The male reproductive system of Mischocyttarus cassununga consists of two testes, each one with three follicles, as occurs in most Vespidae. The seminal vesicle is divided in two chambers, separated by a constriction, so that the anterior locus is a little larger. In the testicular follicles, the spermatozoa are organized in cysts, with approximately 128 per cyst, where the nuclei are oriented toward the follicle center. The spermatozoa of M. cassununga is about 97 μm in length, which makes them the shortest sperm described for Vespidae. Sperm ultrastructure of M. cassununga is very similar of the others Vespidae. But, despite these similarities, the bilobated mitochondrial derivative represents an autapomorphy for M. cassununga. The subdivision of the seminal vesicle has never been observed in any other Vespidae. Thus, this study supports the validity of insect sperm morphology as a tool for phylogenetic analysis within Hymenoptera.