Sperm morphology of the eurasian beaver,Castor fiber: An example of a species of rodent with highly derived and pleiomorphic sperm populations

Dependence of the frequency of sperm defects and dimensions on sperm motility in ejaculates of Polish Landrace boars

An attempt was made to determine the dependence of the frequency of sperm defects and dimensions on sperm motility in ejaculates of Polish Landrace boars. The study was conducted on 393 ejaculates collected from 33 Polish Landrace boars. Ejaculates were grouped according to the percentage of sperm with progressive motility, distinguishing ejaculates in which the percentage of motile sperm was 70% and 80%. In each ejaculate, the frequency of morphological changes in the sperm was determined and morphometric measurements of the sperm were made. Ejaculates with a higher proportion of sperm with progressive motility were found to contain more sperm. The ejaculate volume and sperm concentration in the ejaculate were not found to be directly associated with sperm motility. The frequency of primary defects was linked to sperm motility. Ejaculates with higher sperm motility contained fewer sperm with primary defects. The frequency of minor morphological changes, however, shows no significant dependence on sperm motility in the ejaculate. The primary morphological sperm defects most often found in ejaculates are a proximal droplet and the Dag defect. Both of these morphological forms are more common in ejaculates with lower sperm motility. The most common secondary sperm defects include sperm with a simple bent tail, sperm with a free normal head, and sperm with a distal droplet. These defects were not found to depend on sperm motility in the ejaculate. Sperm cells in ejaculates with greater sperm motility had slightly larger dimensions than sperm in ejaculates with lower sperm motility. Ejaculates with higher sperm motility are preferable for use in practice, not only because more insemination portions can be prepared from them, but also due to the lower frequency of primary defects.

Exogenous melatonin influences distribution of French Alpine buck spermatozoa in morphometrically distinct subpopulations during the non-breeding season

The aim of this study was to establish subpopulations of spermatozoa in bucks using the principal component (PC) and cluster analysis according to morphometric head and tail variables, and to determine differences in proportions of subpopulations between exogenous melatonin-treated and control bucks. The bucks (n = 12) were assigned to two groups comprising six bucks each. By the end of March, four melatonin implants were inserted in the bucks in the experimental group. Semen was collected weekly using an artificial vagina from March to May (the non-breeding season). Analyses were performed in stained smears by SFORM computer-assisted program for eight head and five tail variables. The PC analysis revealed four components with the most important value for each (head outline, head ellipticity, mid-piece length and width). Cluster analysis indicated there were three subpopulations (average-sized spermatozoa- C_1; small and less-elliptic - C_2; big and elliptic - C_3). Melatonin-treated bucks had a greater proportion of C_1 spermatozoa and a lesser proportion of C_2 spermatozoa during May (P < 0.05). To the best of our knowledge, this is the first study where PC and cluster analyses were performed on buck semen with head and tail variables analyzed together, in the same analysis, to evaluate spermatozoa population. Also, this is the first analysis of morphometric variables for assessing the influence of melatonin on spermatozoa subpopulations. The positive effect of melatonin on the proportions of spermatozoa in subpopulations could have been a consequence of the decreasing the proportion of the subpopulation with the least head and tail sizes and ellipticity.

Morphological and neuroanatomical study of the mammary gland in the immature and mature European beaver (Castor fiber)

This study investigated general morphology and immunohistochemical properties of nerve fibres supplying the mammary gland (MG) in the European beaver. The microscopic analysis of the beaver mammary gland revealed the presence of morphological structures which are characteristic for mammals. There were no distinct differences in the morphological features of the mammary gland between the juvenile and non-pregnant mature beaver. The nerve fibres were visualized using antibodies against protein gene product 9.5 (PGP) and biologically active substances including β-hydroxylase tyrosine (DβH), neuropeptide Y (NPY), calcitonine gene-related peptide (CGRP) and substance P (SP). The study has revealed that the MG in the juvenile and mature beaver is richly supplied with PGP-immunoreactive (PGP-IR) nerve fibres. The most abundant innervation was observed in the nipple and less numerous nerve terminals supplied the glandular tissue. Double-labelling immunohistochemistry disclosed that the majority of PGP-IR nerve fibres associated with blood vessels and smooth muscle cells in both the nipple and glandular tissue were also DßH-IR. However, these nerve terminals were less numerous in the glandular tissue than in the nipple. Most of the DßH-IR axons associated with arteries and smooth muscle cells in the entire gland also stained for NPY. Small number of DßH/NPY-IR fibres supplied veins. CGRP-IR fibres were more abundant than those expressing SP. No distinct differences in the distribution and immunohistochemical characteristic of nerve fibres were observed between the juvenile and adult animals. The distribution and immunohistochemical properties of nerve fibres supplying the gland in the beaver remind those previously described in other mammalian species.

Morphological diversity and evolution of the spermatozoon in the mouse-related clade of rodents

Most species in the three highly speciose families of the mouse-related clade of rodents, the Muridae, Cricetidae, and Nesomyidae (superfamily Muroidea), have a highly complex sperm head in which there is an apical hook but there are few data available for the other related families of these rodents. In the current study, using light and electron microscopies, we investigated the structure of the spermatozoon in representative species of four other families within the mouse-related clade, the Dipodidae, Spalacidae, Pedetidae, and Heteromyidae, that diverged at or near the base of the muroid lineage. Our results indicate that a diverse array of sperm head shapes and tail lengths occurs but none of the species in the families Spalacidae, Dipodidae, or Pedetidae has a sperm head with an apical hook. By contrast, a rostrally extending apical hook is present in spermatozoa of members of the Family Heteromyidae which also invariably have comparatively long sperm tails. These findings suggest that the hook-shaped sperm head in the murid, cricetid, and nesomyid rodents evolved after divergence of this lineage from its common ancestor with the other families of the mouse-related clade, and that separate, and independent, convergent evolution of a similar sperm head form, and long sperm tail, occurred in the Heteromyidae.

[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.

The morphology of the squirrel spermatozoon: a highly complex male gamete with a massive acrosome

This study describes the morphology of the spermatozoon from the cauda epididymidis of representative members of two squirrel subfamilies, the Sciurinae and Callosciurinae, as determined by fluorescent, scanning, and transmission electron microscopy. All species examined possess a massive apical segment of the sperm acrosome. It varied markedly in the extent of its caudal flexion but was always much larger, and more complex, than that of the spermatozoon of most other rodents so far documented, although somewhat similar to that of some hystricomorph species. Because this sperm form appears to be present within at least two of the three major living clades of Rodentia, it is possible that it is the ancestral condition within this mammalian order.

Morphometrical characteristics of spermatozoa in Polish Landrace boars with regard to the number of spermatozoa in an ejaculate

Ejaculates (n=344) were collected from 35 Polish Landrace boars. The ejaculates were assigned to one of four groups according to the total number of spermatozoa in an ejaculate. Morphometrical measurements of spermatozoa with proper morphology were performed. Spermatozoa with smaller head length and head area were found in ejaculates with the greatest total sperm number (more than 120 x 10(9) spermatozoa) than in ejaculates with total number of spermatozoa of 70-90 x 10(9). The results of the present study suggest that the number of spermatozoa in an ejaculate influences morphometrical characteristics of the spermatozoa in Polish Landrace boars.