Seasonally different reproductive investment in a medium-sized rodent (Cavia aperea).

Pronounced seasonal variations in day length, temperature, and resource availability characterize the temperate regions and strongly influence the animals living in these environments. To survive and reproduce successfully, animals must allocate resources among competing physiological systems, and they usually adjust their time of breeding to the most adequate season. Here, we examined whether reproductive investment in the wild guinea pig (Cavia aperea) differs across seasons. We kept animals in combined indoor-outdoor enclosures under natural light and temperature year-round. We measured littering probability, litter size, and birth weight, as well as maternal weight loss during lactation. In addition, we measured ovulation rate as a parameter to adjust reproductive investment prenatally. Our data reveal strong seasonal variations in reproductive traits despite the fact that the animals reproduced year-round. The results show a reduced reproductive investment in winter, indicated by a lower litter size and birth weight of pups, whereas investment was highest in warm seasons (summer and autumn) with higher litter size and birth weight. Maternal weight loss in lactation was highest in cold seasons even if the litter size was lower. Furthermore, we found the regulation on the proximate level of the reproductive investment, the ovulation rate, to differ significantly between the seasons.

Influence of culture medium composition on relative mRNA abundances in domestic cat embryos.

Different culture conditions have been used to produce domestic cat embryos. As part of the in vitro procedures, the medium composition significantly affects the quality of the embryo development also. Quality assessments based on cleavage kinetics and blastomere symmetry are useful, but embryos also can differ in their relative gene expression patterns despite similar morphological characteristics. The aim of this study was to compare cat embryos produced with two different in vitro culture systems routinely used in two different laboratories [Smithsonian Conservation Biology Institute, Washington D.C., USA (SCBI) and Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany (IZW)]. Specifically, relative mRNA expression patterns of critical genes for pre-implantation embryo development were assessed in both conditions. Embryos were produced in parallel in both culture systems by IVF using frozen-thawed ejaculated semen in the United States and fresh epididymal sperm in Germany. Success of embryo development in vitro was recorded as well as relative mRNA abundances [DNA methyltransferases 1 and 3A (DNMT1, DNMT3A), gap junction protein alpha 1 (GJA1), octamer-binding transcription factor 4 [OCT4], insulin-like growth factors 1 and 2 receptors (IGF1R, IGF2R), beta-actin (ACTB)] in pools of days 4-5 morulae by semi-quantitative RT-PCR assay. Percentages of cleaved embryos were similar (p > 0.05) between both culture systems, regardless of the location. OCT4 mRNA abundance was higher (p < 0.05) in embryos derived in the SCBI culture system compared with those from the IZW system when epididymal sperm was used for IVF. No clear correlation between the expression pattern and the culture system could be found for all other genes. It is suggested that OCT4 expression might be affected by the media composition in some conditions and can be the indicator of a better embryo quality.

Capabilities and challenges of examination of gene expression for quality assessment of domestic cat embryos.

Early embryos are characterized by an accurately controlled gene expression pattern that might be deregulated during in vitro culture (IVC). The expression pattern of the developmental genes may serve as markers for embryo quality. Here, we examined the temporal pattern of relative mRNA abundance of genes important for early embryonic development in embryos produced by different fertilization methods [in vitro fertilization (IVF) vs intracytoplasmic sperm cell injection (ICSI)] and sperm sources (fresh vs frozen-thawed) applying reverse transcriptase (RT) PCR. The temporal pattern of gene expression was found to be gene specific and similar in all four examined groups in a semi-quantitative assay. In morulae, higher relative mRNA levels were found in embryos generated with fresh sperm, whereas in blastocysts, mRNA abundance tended to be higher in embryos produced with cryopreserved sperm cells. This indicates an influence of sperm cryopreservation on the temporal gene expression pattern in early cat embryos. We also examined relative mRNA abundances by real-time quantitative RT-PCR in blastocysts. In this context, blastocysts produced with fresh semen tended to have lower DNA methyltransferase 3A (DNMT3A) but higher gap junction protein alpha 1 (GJA1) and octamer-binding transcription factor 4 (OCT4) mRNA levels compared with those derived with frozen-thawed semen. We conclude that assessing embryo quality by measuring gene expression pattern in early embryos is challenging because of a high variability between individual embryos.

Preservation of primordial follicles from lions by slow freezing and xenotransplantation of ovarian cortex into an immunodeficient mouse.

Assisted reproductive technology (ART) is considered an important tool in the conservation of endangered species, but often the most limiting factor of ART is the availability of mature oocytes. The aim of the present study was to investigate the feasibility of preserving female germ cells from ovaries of female lions (Panthera leo). Good quality cumulus-oocyte complexes (COCs) were isolated and subjected to in vitro maturation (IVM). In addition, ovarian cortex was obtained and cut into pieces for culture and cryopreservation by slow freezing. The survival of ovarian follicles was assessed by histology. Frozen-thawed samples of ovarian cortex samples were xenotransplanted under the skin of ovariectomized immunodeficient mouse for 28 days. Overall, 178 intact COCs were obtained from 13 lions, but only 28.1% were matured in vitro indicating insufficient IVM conditions. In contrast, almost all follicles within the ovarian cortex survived culture when the original sample was from a young healthy lion collected immediately after euthanasia. Within the xenotransplants, the number of primordial follicles decreased after 28 days by 20%, but the relation between primordial and growing follicles changed in favour of follicular growth. Female gamete rescue from valuable felids may be performed by slow freeze cryopreservation of ovarian cortex. Although the IVM protocol for lions is not yet optimized, mature oocytes may be obtained after long-term xenotransplantation and IVM and could potentially represent one way of salvage of endangered felid species in the future.