Analysis of changes in the morphological structures of sperm during preservation of liquid boar semen in two different seasons of the year

Animal fertility is the result of a combination of genetic, physiological and environmental factors. Assessment of semen quality plays a key role in determining the reproductive performance of boars. The aim of the study was to determine the effect of two seasons of the year on the morphology, morphometry, cell membrane integrity and mitochondrial activity of sperm during storage of liquid boar semen at 17 °C. The study was carried out using 20 boars. Four ejaculates were collected from each boar in each of two seasons of the year. All tests were carried out five times: at 1, 24, 48, 96 and 168 h during storage. The results showed that sperm in ejaculates collected in summer are more sensitive to storage conditions than those from ejaculates obtained in winter. The percentage of sperm with morphological defects was shown to increase with the storage time of the diluted ejaculates, particularly between 96 and 168 h of preservation. In summer, the percentage of sperm with an intact cell membrane and the percentage with high mitochondrial membrane potential are much lower than in winter, at every hour of semen preservation. In the case of boars used for artificial insemination, it is worth taking into account the season when the semen is collected, especially if it is to be stored in liquid form. Assessment of sperm cell structures during storage of liquid semen should be implemented at insemination stations and should be carried out more often in summer.

Estimation of sperm concentration limits to produce intrauterine insemination doses in swine

This study evaluated the effect of sperm concentration of boar semen doses, for intrauterine artificial insemination (IUAI), on semen quality and established concentration limits for their production. Twenty ejaculates from four crossbred mature PIC® boars were collected to produce 50 mL-semen doses in a split-sample, reaching the following sperm concentrations: ~ 20; 30; 60 and 100 × 10⁶ cells/mL. Doses were produced using Androstar Plus®, stored at 17 °C, and evaluated until 120 h of storage. There was a linear decrease in sperm motility as the sperm concentration increased (P linear < 0.01). The concentration which no longer affected the total and progressive motility was 59 and 55 × 10⁶ cells/mL, respectively (corresponding to 71 and 62%, respectively). The pH linearly decreased as the sperm concentration increased (P < 0.01); however, at 72 and 120 h the parameter dramatically reduced in boar semen doses with 60 and 100 × 10⁶ cells/mL. The percentage of cells with intact plasma and acrosomal membranes or with high mitochondrial membrane potential was not influenced by the sperm concentration (P ≥ 0.15) In conclusion, sperm motility was negatively affected in highly (60 and 100 × 10⁶ cells/mL) concentrated doses. To achieve suitable sperm motility, boar semen doses may not surpass the sperm concentration of 55 × 10⁶ cells/mL. The effect of low-concentrated boar semen doses on sperm quality still needs to be better evaluated, mainly considering the influence of extender type and thermo-resistance conditions.

Sperm morphology of predatory pirate bugs Amphiareus constrictus and Blaptostethus pallescens (Heteroptera: Anthocoridae) with phylogenetic inferences

The sperm morphology of two predatory bugs Amphiareus constrictus and Blaptostethus pallescens, representing the tribes Dufouriellini and Blasptostethini, respectively, was described using light and transmission electron microscopy. The spermatozoa of Amphiareus constrictus and Blaptostethus pallescens are fine and long, each measuring 216.6μm and 181.0μm in length, of which 37.0μm and 11.6μm, respectively, comprise the nuclei. When stained with DAPI (for DNA), the posterior half of the nucleus in B. pallescens exhibited low fluorescence, while in A. constrictus this feature was observed only in the last 6μm. In both species, as in Heteroptera in general, the spermatozoa have, in the head region, an acrosome and nucleus, and in the flagellar region, an axoneme with 9 accessory tubules, 9 peripheral doublets and 2 central microtubules (9+9+2 microtubules), 2 mitochondrial derivatives (MDs), and a centriolar adjunct in the nucleus-flagellum transition. However, unlike most Heteroptera, in these species, the MDs are asymmetric, and the centriolar adjunct is quite long and encompasses completely the posterior nuclear end and the anterior tips of the MDs. These features are considered as derived, thus supporting the condition derived of Anthocoridae within Cimicomorpha. In addition, several traits of the spermatozoa of these two species easily distinguish one species (and probably a tribe) from the other; for example, the difference of formats in the MDs, and the long anterior projection of the centriolar adjunct parallel to the nucleus in B. pallescens.

Comparative sperm ultrastructure of twelve leptodactylid frog species with insights into their phylogenetic relationships

The spermatozoa of representatives of three Neotropical frog subfamilies, Leiuperinae, Leptodactylinae and Paratelmatobiinae, were observed using Transmission Electron Microscopy, with the aim of identifying ultrastructural traits that provide insights into the phylogenetic relationships among these anurans, which are currently unclear. In the leiuperines, spermatozoa of Physalaemus albifrons, P. cicada, P. deimaticus and P. feioi were characterized by an acrosomal vesicle covering the subacrosomal cone that was not observed in the spermatozoa of Physalaemus centralis and P. cuvieri. The tail of the spermatozoa of P. albifrons, P. centralis, P. cicada, P. cuvieri, P. deimaticus, and P. feioi presented a long undulating membrane, whereas Engystomops petersi and E. freibergi, which form a sister clade to Physalaemus, had an axial fiber, which were absent in Physalaemus. Other leiuperine, E. puyango had an abaxonemal bulb-like swelling distally to the paraxonemal rod, which were also absent in Physalaemus. These differences support the revalidation of Engystomops as a true taxon, distinct from Physalaemus. The tail of the spermatozoa of E. petersi and E. freibergi was similar to that of Paratelmatobius poecilogaster (Paratelmatobiinae). The spermatozoa of Leptodactylus natalenis (Leptodactylinae) had undulating membrane and axial fiber, in contrast with Adenomera marmorata, which lacked these structures. Morphological differences between A. marmorata and L. natalensis sperm cells appeared to validate the allocation of A. marmorata into a genus distinct from Leptodactylus. Overall, dissimilarities in the spermatozoa of the leptodactylids provided an important phylogenetic signal for the understanding of their taxonomic relationships.

The sperm ultrastructure and spermiogenesis of Tribolium castaneum (Coleoptera: Tenebrionidae) with evidence of cyst degeneration

Previous studies on the spermatogenesis of tenebrionid beetles showed the unusual formation of two antiparallel sperm bundles per cyst. In this work we reported this feature also in Tribolium castaneum using light and transmission electron microscopy. The sperm structure of T. castaneum, similar to other tenebrionids, consists of a three-layered acrosome, an elongated nucleus and a flagellum with a 9+9+2 axoneme, two accessory bodies and two asymmetric mitochondrial derivatives. The presence of two antiparallel sperm bundles per cyst also in Meloidae and Rhipiphoridae suggests that it is a strong trait synapomorphic for Tenebrionoidea. The huge degeneration of whole sperm cells in several cysts of testes during spermiogenesis is also described.

The sperm ultrastructure of Stictoleptura cordigera (Füssli, 1775) (Insecta, Coleoptera, Cerambycidae)

The spermatozoa of the longhorn beetles Stictoleptura cordigera were ultrastructurally described in this paper. They have an apical bilayered acrosome, an elongated nucleus, a centriole with star-shape links, two asymmetric mitochondrial derivatives partially crystallized and a 9+9+2 flagellar axoneme with accessory tubules provided with 16 protofilaments in their wall. A centriole adjunct is present and gives rise to two thick laminae as accessory bodies, also asymmetrical, to which two relatively small puff-like structures of different size are connected. These features were previously found in the sperm of the cerambycid Morimus asper. The strict similarity of the cerambycid sperm characters with those of curculionoids indicates a clear phylogenetic relationship between Chrysomeloidea and Curculionoidea.