Duration of Spermatogenesis and Spermatogenic Efficiency in 2 Large Neotropical Rodent Species: The Agouti (Dasyprocta leporina) and Paca (Agouti paca)

Abstract

The agouti (Dasyprocta leporina) and paca (Agouti paca) are among the largest extant rodent species. Although these species have considerable economic potential, there are few reports in the literature concerning male reproductive biology in sexually mature agoutis and pacas. The objectives of the present study were to perform detailed stereologic and histologic analyses of the testis and estimate spermatogenic cycle length in these 2 Neotropical rodent species as well as to compare the data with those from other well-studied rodent members of the Hystricomorpha and Myomorpha suborders. Eight adult agoutis and 6 adult pacas were used. The spermatogenic cycle in agoutis and pacas lasted 9.5 6 0.03 and 11.5 6 0.16 days, respectively, whereas the total duration of spermatogenesis for these 2 species was 42.8 6 0.16 and 51.6 6 0.7 days, respectively. Most of the parameters investigated were similar to those obtained for the other members of the Hystricomorpha suborder. As a result of the combination of high values of seminiferous tubule volume density, number of Sertoli cells per gram of testis, Sertoli cell efficiency, and a relatively short duration of spermatogenesis, the spermatogenic efficiency found in agoutis (52 6 2 6 10 6 ) and pacas (39 6 2 6 10 6 ) was particularly high when compared with that of previously investigated mammalian species. The data presented in this investigation would be useful for studies related to animal production as well as improvement and conservation programs involving these 2 large Neotropical rodent species.

Germ cells and the seminiferous epithelium cycle in the wild rodent Oxymycterus rufus (Rodentia: Cricetidae)

“…The duration of the SEC in O. rufus was remarkably low, even when compared to the lowest values registered so far, for the rodents D. leporina [21] and Cleterionomys glareolus [31]. Also, the data shown for O. rufus was lower than other Myomorpha and Hystricomorpha [17,18,24], which would be explained by the mating strategy. Promiscuous animals, such as O. rufus, show shorter cycles with fast sperm production, reflecting an adaptation to competition between males for fertilization [32].…”

“…In addition, it has been observed that the largest allocation and high energy expenditure in testicular mass were found in small animals, as well as in O. rufus. Despite higher than the observed in larger rodents of the suborder Hystricomorpha [17,18], the GSI found for O. rufus was lower than the obtained for other subjects from the suborder Myomorpha [19]. Different GSI values between suborders takes place due to the system of reproduction, since the testicles size is also related to the reproductive behavior, when monogamous or polygynous species show lower GSI than promiscuous species [10].…”

“…The average frequency of each stage of the SEC is considered a constant variable in individuals of the same species [7]. The most frequent stage in O. rufus was stage 1, as well as previous observations in wild rodents [18].…”

Morfologia e dinâmica testicular em cutias - Dasyprocta prymnolopha ) adultas

“…Relativo à caracterização histológica dos testículos de cutia, no que diz respeito ao comportamento do epitélio seminífero nos diferentes estádios do CES, foram identificadas oito organizações celulares, ou seja, oito estádios do CES, seguindo o que foi descrito para cutia da espécie Dasyprocta leporina, bem como para a paca (Agouti paca) (Costa et al, 2010). Foram constatadas diferenças em relação a esses achados em suínos Piau (França, 1991) e em esquilos-cinzentos (Taiti e Johnson, 1982) no que se refere às gerações de espermatogônias do tipo B e intermediárias, assim como em caititus (Cardoso,, 2009) Costa et al (2004) em catetos, diferindo apenas em relação às maiores; este observou maior frequência no estádio 6 e os demais maior frequência no estádio 1.…”

“…Em preás, Santos et al (2011) observaram também oito estádios, apresentando, igualmente, o estádio 1 com maior frequência. Quando comparada com os resultados obtidos por Costa et al (2010), a maior frequência encontrada na cutia da espécie D. leporina foi no estádio 8, e a menor em 7; em pacas (Agouti paca), a maior frequência foi do estádio 1, e a menor em 7, diferindo dos resultados para cutia da espécie D. prymnolopha.…”