Sperm ultrastructure of three species of ladybirds (Coleoptera, Coccinellidae)

The sperm of three coccinellid species belonging to the subfamilies Chilocorinae, Coccinellinae and Epilachninae were studied under light and transmission electron microscopy. The basic sperm structure of these ladybirds is common to that of the other previously studied species, especially the acrosome in front of the basal body and not the nucleus, with this latter running parallel with the flagellar components. In the Chilocorinae Platynaspis luteorubra (Platynaspidini) the sperm are of the type 1, as in Scymnini and Coccinellini, since they exhibited a cylindrical basal body with 9 + 0 and then 9 + 2, microtubules continuing further in an initial flagellar portion with the only axoneme devoid of accessory structures. The sperm exhibits a thin nucleus and mitochondrial derivatives. Such uniformity of sperm ultrastructure could be indicative of the occurrence of a close relationship between Platynaspidini and Scymnini as also proposed in the previous studies. Conversely, they differ markedly from the sperm of type 3 observed in the Chilocorini Exochomus quadripustulatus. In the Coccinellini Propylea quatuordecimpunctata the sperm are also of the type 1, but they can be easily differentiated from those of the other Coccinellinae studied so far, because of their very short acrosome without the posterior extension, the relatively thicker mitochondrial derivatives and the cylindrical nucleus. Epilachna clandestina sperm resemble those of E. quadripustulatus but differ from them, because they exhibit an elliptical nucleus which is anteriorly very thin, and the asymmetrical mitochondrial derivatives in the anterior extremity, with the greater one starting at the same level of the basal body, rather than at the nucleus level, as it occurs in E. quadripustulatus. Because of the differences observed in the sperm ultrastructure we propose a new sperm type (Type 4) for E. clandestina. This study on ladybird spermatozoon ultrastructure clearly indicates that the current classifications of coccinellids do not reflect the natural history of this well-known insect family.

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.

Sperm morphology of mud dauber Sceliphron fistularium dahlbom (Hymenoptera: Apoidea: Sphecidae), as an indication of bees relation

The morphology of spermatozoon of Sceliphron fistularium is very similar to that described for bees. In particular, the response to E-PTA stains is similar to that observed in corbiculated Apidae, especially Meliponini bees. Spermatozoa measure 285 microm and are composed of 1) a bilayered acrosome (acrosomal vesicle and perforatorium); 2) a homogeneous and compact nucleus; 3) a 9+9+2 axoneme; 4) a rod-shaped centriolar adjunct; 5) two asymmetrical mitochondrial derivatives with paracrystalline material exclusively in the larger one, and 6) two accessory bodies. Only the accessory microtubules of axoneme and the paracrystalline material are E-PTA positive. Comparison of S. fistularium sperm to data on Hymenoptera corroborates their proximity with bees.

Structure and ultrastructure of the spermatozoa of Halictidae (Hymenoptera, Apoidea)

The spermatozoa in Halictidae are sometimes observed in spermatodesmata in the seminal vesicle. They are linear, long, slender and their lengths vary from 213 microm to about 330 pm. The head region consists in the anterior acrosomal complex, formed by a conical acrosomal vesicle that shows an inner paracrystalline perforatorium extending into the nucleus. The nucleus, measuring about 16 microm to 46 microm, is linear and strongly electron-dense, however some electron-lucent lacunae with electron-dense granules homogeneously organized were observed. The nucleus is attached to the flagellum by the centriolar adjunct, which is compact and electron-dense. It begins at the nuclear base and finishes just above the smaller mitochondrial derivative. The flagellum consists of two mitochondrial derivatives, an axoneme and two accessory bodies. Halictidae have an axoneme with 9+9+2 microtubule pattern which gradually disorganizes towards the final region. The mitochondrial derivatives are asymmetric in both length and diameter and only the larger presents the paracrystalline region. The typical pattern for Halictidae spermatozoa here described may provide useful additional information for future phylogenetic analysis of the superfamily Apoidea.

Sperm ultrastructure of the bees Exomalopsis (Exomalopsis) auropilosa Spinola 1853 and Paratetrapedia (Lophopedia) sp. Michener & Moure 1957 (Hymenoptera, Apidae, Apinae)

The spermatozoa of Exomalopsis auropilosa and Paratetrapedia (Lophopedia) sp. are long and slender, measuring about 374 microm and 370 microm in length of which the head region measures approximately 25.8 and 28.3 microm, respectively. The head consists of an acrosome formed by an acrosomal vesicle covering a perforatorium, which presents a paracrystalline organization in Paratetrapedia (Lophopedia) sp. and a nucleus. This latter measures about 24 microm in Exomalopsis auropilosa and 27 microm in Paratetrapedia (Lophopedia) sp., and has compact chromatin. The nucleus is attached to the flagellum by an electron dense material and centriolar adjunct is observed between it and smaller mitochondrial derivative. In this flagellar region only one accessory body is observed, which occurs between the larger mitochondrial derivative and the axoneme. The flagellum consists in a typical axoneme, 9+9+2 microtubules, two mitochondrial derivatives and two accessory bodies. The two mitochondrial derivatives are asymmetric in both length and diameter, and paracrystalline material appears only in the larger mitochondrial derivative. The structure and ultrastructure of the spermatozoa of the bee species here described are similar to the majority of sperm found in the other Hymenoptera and may be a contribution for future phylogenetic analysis of Apidae.

Sperm ultrastructure of the honey bee (Apis mellifera) (L) (Hymenoptera, Apidae) with emphasis on the nucleus-flagellum transition region

The flagellum of Apis mellifera (Hymenoptera, Apidae) consists of two mitochondrial derivatives, an axoneme and two accessory bodies. The mitochondrial derivatives are of unequal size and lie parallel to the axoneme. In the larger derivative four regions can be distinguished while in the smaller, only three. The region occurring only in the larger derivative consists of paracystalline material. The smaller mitochondrial derivative terminates anterior to the larger one. An extremely long centriolar adjunct is observed between the nucleus and the smaller mitochondrial derivative. This adjunct is compact, very electron dense and gradually tapers from base toward apex, finishing at the anterior extremity of the axonemal microtubules. In this flagellar region, there is only one accessory body present between the larger mitochondrial derivative and the axoneme. Anteriorly, the tips of the axonemal microtubules are inserted in a well developed mass of granular appearance. This material surrounds the nuclear base, separating it from the anterior end of the larger mitochondrial derivative. We believe that the structure identified here as a centriolar adjunct is homologous to that observed in Formicidae, Ichneumonoidea and Symphyta. Therefore, very probably, it is common to most Hymenoptera.