34
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Sperm structure and motility in the eusocial naked mole-rat, Heterocephalus glaber: a case of degenerative orthogenesis in the absence of sperm competition?

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Background

          We have studied sperm structure and motility in a eusocial rodent where reproduction is typically restricted to a single male and behaviourally dominant queen. Males rarely compete for access to the queen during her estrus cycle, suggesting little or no role for sperm competition.

          Results

          Our results revealed an atypical mammalian sperm structure with spermatozoa from breeding, subordinate and disperser males being degenerate and almost completely lacking a "mammalian phylogenetic stamp". Sperm structure is characterized by extreme polymorphism with most spermatozoa classified as abnormal. Sperm head shapes include round, oval, elongated, lobed, asymmetrical and amorphous. At the ultrastructural level, the sperm head contains condensed to granular chromatin with large open spaces between the chromatin. Nuclear chromatin seems disorganized since chromatin condensation is irregular and extremely inconsistent. The acrosome forms a cap (ca 35%) over the anterior part of the head. A well defined nuclear fossa and neck with five minor sets of banded protein structures are present. The midpiece is poorly organized and contains only 5 to 7 round to oval mitochondria. The flagellar pattern is 9+9+2. A distinct degenerative feature of the tail principal piece is the absence of the fibrous sheath. Only 7% motile spermatozoa were observed which had exceptionally slow swimming speeds.

          Conclusion

          In this species, sperm form has simplified and degenerated in many aspects and represents a specialised form of degenerative orthogenesis at the cellular level.

          Related collections

          Most cited references45

          • Record: found
          • Abstract: found
          • Article: not found

          SPERM COMPETITION AND ITS EVOLUTIONARY CONSEQUENCES IN THE INSECTS

          Biological Reviews, 45(4), 525-567
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Sperm in competition: not playing by the numbers.

            The outcome of sperm competition is mediated largely by the relative numbers of sperm from competing males. However, substantial variation in features of sperm morphology and behaviour, such as length, longevity and motility, exists and researchers have suggested that this variation functions in postcopulatory sexual selection. Recent studies have determined the effect of these sperm-quality traits on fertilization success and a synthesis of this literature reveals that they are important in both sperm competition and cryptic female choice. To understand how postcopulatory sexual selection influences sperm traits, future research should determine sex-specific interactions that influence paternity, identify genetic correlations between ejaculate characters, quantify the relative costs of producing different sperm traits, and test assumptions of models of sperm quality evolution. Such research will shed light on what evolutionary pressures are responsible for the diversity in sperm morphometry and behaviour.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Spermatozoal traits and sperm competition in Atlantic salmon: relative sperm velocity is the primary determinant of fertilization success.

              Sperm competition occurs when sperm from more than one male compete for fertilizations. This form of post-copulatory sexual selection is recognized as a significant and widespread force in the evolution of male reproductive biology and as a key determinant of differential male reproductive success. Despite its importance, however, detailed mechanisms of sperm competition at the gamete level remain poorly understood. Here, we use natural variation in spermatozoal traits among wild Atlantic salmon (Salmo salar), a species naturally adapted to sperm competition, to examine how the relative influences of sperm (i) number, (ii) velocity, (iii) longevity, and (iv) total length determine sperm competition success. Atlantic salmon fertilize externally, and we were therefore able to conduct controlled in vitro fertilization competitions while concurrently measuring spermatozoal traits within the aqueous micro-environment to which salmon gametes are naturally adapted. Microsatellite DNA fingerprinting revealed that a male's relative sperm velocity was the primary determinant of sperm competition success. There was no significant relationship between fertilization success and either relative sperm number or total length; sperm longevity showed an inverse relationship with competition success. These relationships were consistent for two experimental repeats of the in vitro fertilization competitions. Our results therefore show, under the natural microenvironment for salmon gametes, that relative sperm velocity is a key spermatozoal component for sperm competition success. Atlantic salmon sperm can be considered to enter a competition analogous to a race in which the fastest sperm have the highest probability of success.
                Bookmark

                Author and article information

                Journal
                BMC Evol Biol
                BMC Evolutionary Biology
                BioMed Central
                1471-2148
                2011
                5 December 2011
                : 11
                : 351
                Affiliations
                [1 ]Department of Medical Bioscience, University of the Western Cape, Bellville, South Africa
                [2 ]Division of Anatomy and Histology, Department of Biomedical Sciences, Stellenbosch University, Parow, South Africa
                [3 ]Department of Zoology, University of Cape Town, Cape Town, South Africa
                Article
                1471-2148-11-351
                10.1186/1471-2148-11-351
                3247228
                22142177
                c718d0a6-5ec3-494f-bb16-81b0fadd5bff
                Copyright ©2011 van der Horst et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 29 September 2011
                : 5 December 2011
                Categories
                Research Article

                Evolutionary Biology
                Evolutionary Biology

                Comments

                Comment on this article