Reproductive biology of Río Negro tuco-tuco, Ctenomys rionegrensis (Rodentia: Octodontidae)

Abstract

Reproductive success depends on a precise synchronization of organisms' activities with the environment, determining the evolution of mechanisms controlling reproductive behaviour. In temperate zones mammals exhibit pronounced seasonal reproduction because of thermoregulation costs imposed by low winter temperatures and limited food availability. Even occupying burrows that buffer external ambient conditions, these restrictions also affect subterranean rodents inhabiting these latitudes. Tuco-tucos (genus Ctenomys) are subterranean herbivorous rodents that have a Neotropical distribution between 17 and 541 of latitude S. Ctenomys rionegrensis is one of the three species occurring in Uruguay and generated interest due to chromatic polymorphism in a restricted area (50 Â 60 km). Here we describe the timing of breeding in C. rionegrensis based on the reproductive status of free-living females and the proportion of juveniles in the population, and describe the characteristics of the estrous cycle of the species using cytological techniques. As expected, the data showed a clear seasonality in female breeding and provided evidence of the occurrence of post-partum estrous. The reproductive activity began in late austral autumn and the highest proportion of pregnant females was observed in winter. At the beginning of the austral spring, the prevalence of lactating females increased as a consequence of the first births and remained high until early summer. This pattern of breeding seasonality was clearly correlated with the annual temperature variation. The estrous cycle showed four phases characterized by both different cellular types and the abundance and appearance of mucus, which allows a clear determination of female's reproductive status.

Sexual behavior of Ctenomys pearsoni (Rodentia: Ctenomyidae) in “Carrasco” population (Montevideo - Uruguay)

“…After courting and copulating with the female, the male tends to leave the female's cave before being injured by the female (Bennet & Jarvis, 1988). This type of behavior differs from that observed for C. rionegrensis (Tassino & Passos, 2010), where the animals remain together in contact with one individual leaning on the other.…”

“…The other patterns presented were 10 (twice) and 11 (once). Different types of copulation were observed in C. pearsoni (Solis population) and C. rionegrensis pattern 9 (Altuna et al, 1991;Tassino & Passos, 2010), C. mendocinus patterns 10 in 4 cases and 12 in 14 times (Camin, 1999), and C. talarum patterns 9 in 6 cases and 11 once (Fanjul & Zenuto, 2008a). For the Dewsbury classification, the pattern that characterized C. mendocinus is 12, C. talarum 11, and in our study, C. pearsoni performs the pattern 12.…”

“…From an evolutionary perspective, survival is valuable only as it contributes to reproduction (Barnard, 2004). Achieving such reproductive success requires the correct integration of physiological, behavioral, social, and environmental stimuli (Tassino & Passos, 2010). Reproduction creates a conflict between the members of the couples involved generated by the differences in investment made by each sex from gametes to parental care (Chapman, 2006) because both genders try to maximize their fitness (Krebs & Davies, 1993).…”

“…For this reason, the data available on sexual behavior is limited. Sexual behavior has been studied in different species of genus Ctenomys in C. mendocinus Philippi, 1869 (Camin, 1999), C. talarum Thomas, 1898 (Zenuto et al, 2002;Fanjul & Zenuto, 2008b), C. rionegrensis Langguth & Abella, 1970(Tassino & Passos, 2010 and in Solis population of C. pearsoni (Altuna et al, 1991). This work aims to determine courtship and copulation behavior in the Carrasco population of C. pearsoni through the description of behavioral units and their sequence.…”

Reproduction in the East African root rat (Tachyoryctes splendens; Rodentia: Spalacidae) from Tanzania: the importance of rainfall

“…Because precipitation is a major influence for the re‐sprouting, regeneration and an overall increase in plants succession and subsequently increased vegetation cover (Bennie, ; Barber, ; Pregitzer & King, ), the numbers of pup births in T. splendens over the periods of rainfall might be an ultimate factor. This observation is parallel to reports documented for bathyergids, geomyids, ctenomyids, Middle East spalacids and other arboreal small mammals (Vaughan, ; Andersen, ; Bronson, ; Lovegrove & Jarvis, ; Bennett & Jarvis, ; Ims, ; Bennett et al ., ; Malizia & Busch, ; Bennett & Faulkes, ; Herbst et al ., ; Camin, ; Tassino & Passos, ).…”