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Testis Mass (testis + mass)
Selected AbstractsModerate Seasonality in Testis Function of Domestic CatREPRODUCTION IN DOMESTIC ANIMALS, Issue 5 2007S Blottner Contents Adult male domestic cats are known to produce sperm throughout the year, although sexual activity is influenced by geographical location. In the northern hemisphere, feral domestic cats reproduce usually between January and July. Thus, seasonality in testicular activity might be suggested. The aim of the present study was to investigate gametogene and endocrine activity of cat testis throughout the entire year. Testes and epididymides (n = 10,12 per month) were collected after castration. Spermatogenesis was quantified by assessment of testicular sperm per testis and by flow cytometric analysis of the cells with different DNA content. Sperm from cauda epididymis were evaluated according to motility and morphological integrity. Testicular testosterone concentration was determined by enzyme immunoassay. Testis mass and sperm production varied moderately throughout the year. Significant seasonal variations were observed in the proportion of cells in the G2/M phase of cell cycle (p = 0.004) and the meiotic transformation (ratio of haploid : tetraploid cells; p = 0.021). Changes in testicular testosterone concentration were more pronounced and showed periods with high (spring) and significantly reduced testosterone levels (autumn). A marked seasonal alteration (p < 0.001) with a peak in March was assessed in the percentage of progressively motile sperm. The proportion of morphological intact sperm was also significantly higher in spring compared with winter time (p < 0.001). In conclusion, the study suggests moderate seasonal changes in quantity of sperm, more pronounced annual variation in hormone production and a distinct seasonal influence on functional sperm parameters in domestic cat. [source] Comparative studies of brain evolution: a critical insight from the ChiropteraBIOLOGICAL REVIEWS, Issue 1 2009Dina K. N Dechmann Abstract Comparative studies of brain size have a long history and contributed much to our understanding of the evolution and function of the brain and its parts. Recently, bats have been used increasingly as model organisms for such studies because of their large number of species, high diversity of life-history strategies, and a comparatively detailed knowledge of their neuroanatomy. Here, we draw attention to inherent problems of comparative brain size studies, highlighting limitations but also suggesting alternative approaches. We argue that the complexity and diversity of neurological tasks that the brain and its functional regions (subdivisions) must solve cannot be explained by a single or few variables representing selective pressures. Using an example we show that by adding a single relevant variable, morphological adaptation to foraging strategy, to a previous analysis a correlation between brain and testes mass disappears completely and changes entirely the interpretation of the study. Future studies should not only look for novel determinants of brain size but also include known correlates in order to add to our current knowledge. We believe that comparisons at more detailed anatomical, taxonomic, and geographical levels will continue to contribute to our understanding of the function and evolution of mammalian brains. [source] EXPERIMENTAL MANIPULATION OF SEXUAL SELECTION PROMOTES GREATER MALE MATING CAPACITY BUT DOES NOT ALTER SPERM INVESTMENTEVOLUTION, Issue 4 2009Helen S. Crudgington Sexual selection theory makes clear predictions regarding male spermatogenic investment. To test these predictions we used experimental sexual selection in Drosophila pseudoobscura, a sperm heteromorphic species in which males produce both fertile and sterile sperm, the latter of which may function in postmating competition. Specifically, we determined whether the number and size of both sperm types, as well as relative testis mass and accessory gland size, increased with increased sperm competition risk and whether any fitness benefits could accrue from such changes. We found no effect of sexual selection history on either the number or size of either sperm morph, or on relative testis mass. However, males experiencing a greater opportunity for sexual selection evolved the largest accessory glands, had the greatest mating capacity, and sired the most progeny. These findings suggest that sterile sperm are not direct targets of sexual selection and that accessory gland size, rather than testis mass, appears to be an important determinant of male reproductive success. We briefly review the data from experimental sexual selection studies and find that testis mass may not be a frequent target of postcopulatory sexual selection and, even when it is, the resulting changes do not always improve fitness. [source] ADAPTATION TO EXPERIMENTAL ALTERATIONS OF THE OPERATIONAL SEX RATIO IN POPULATIONS OF DROSOPHILA MELANOGASTEREVOLUTION, Issue 2 2008Max Reuter Theory predicts that males adapt to sperm competition by increasing their investment in testis mass to transfer larger ejaculates. Experimental and comparative data support this prediction. Nevertheless, the relative importance of sperm competition in testis size evolution remains elusive, because experiments vary only sperm competition whereas comparative approaches confound it with other variables, in particular male mating rate. We addressed the relative importance of sperm competition and male mating rate by taking an experimental evolution approach. We subjected populations of Drosophila melanogaster to sex ratios of 1:1, 4:1, and 10:1 (female:male). Female bias decreased sperm competition but increased male mating rate and sperm depletion. After 28 generations of evolution, males from the 10:1 treatment had larger testes than males from other treatments. Thus, testis size evolved in response to mating rate and sperm depletion, not sperm competition. Furthermore, our experiment demonstrated that drift associated with sex ratio distortion limits adaptation; testis size only evolved in populations in which the effect of sex ratio bias on the effective population size had been compensated by increasing the numerical size. We discuss these results with respect to reproductive evolution, genetic drift in natural and experimental populations, and consequences of natural sex ratio distortion. [source] Social group size, potential sperm competition and reproductive investment in a hermaphroditic leech, Helobdella papillornata (Euhirudinea: Glossiphoniidae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2004G. N. Tan Abstract Social group size may affect the potential for sperm competition, and this in turn may favour ontogenetic adjustments in testicular mass according to the likely requirements for sperm and spermatophore production. In a number of comparative analyses of testis mass among vertebrate species that differ in mating system or social organization, increasing potential for sperm competition is associated with larger testis size. Intraspecific phenotypic plasticity should be able to produce the same pattern if social group size is heterogenous and reflects differing degrees of average sperm competition, but this intraspecific effect is less well studied. We tested the effect of social groups on both male and female investment in the simultaneously hermaphroditic leech, Helobdella papillornata. Leeches were placed in groups of one, two, four or eight. Sexual investment at the onset of reproductive maturity was quantified as the total testisac volume for male function and total egg volume for female function. We found that testisac volume (statistically adjusted for body size) showed a significant increase with increasing group size. Total egg volume (also adjusted for body size) was unaffected by group size. Our findings indicate adaptive developmental plasticity in male gonad investment in response to the potential for sperm competition. [source] | ||||||||||