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The neonatal southern white rhinoceros ovary contains oogonia in germ cell nests.

ABSTRACT: The northern white rhinoceros is functionally extinct with only two females left. Establishing methods to culture ovarian tissues, follicles, and oocytes to generate eggs will support conservation efforts using in vitro embryo production. To the best of our knowledge, this is the first description of the structure and molecular signature of any rhinoceros, more specifically, we describe the neonatal and adult southern white rhinoceros (Ceratotherium simum simum) ovary; the closest relation of the northern white rhinoceros. Interestingly, all ovaries contain follicles despite advanced age. Analysis of the neonate reveals a population of cells molecularly characterised as mitotically active, pluripotent with germ cell properties. These results indicate that unusually, the neonatal ovary still contains oogonia in germ cell nests at birth, providing an opportunity for fertility preservation. Therefore, utilising ovaries from stillborn and adult rhinoceros can provide cells for advanced assisted reproductive technologies and investigating the neonatal ovaries of other endangered species is crucial for conservation.

SUBMITTER: Appeltant R

PROVIDER: S-EPMC10582104 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature

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The neonatal southern white rhinoceros ovary contains oogonia in germ cell nests.

Appeltant Ruth R Hermes Robert R Holtze Susanne S Modina Silvia Clotilde SC Galli Cesare C Bjarkadottir Briet D BD Adeniran Babatomisin V BV Wei Xi X Swegen Aleona A Hildebrandt Thomas Bernd TB Williams Suzannah A SA

Communications biology 20231017 1

The northern white rhinoceros is functionally extinct with only two females left. Establishing methods to culture ovarian tissues, follicles, and oocytes to generate eggs will support conservation efforts using in vitro embryo production. To the best of our knowledge, this is the first description of the structure and molecular signature of any rhinoceros, more specifically, we describe the neonatal and adult southern white rhinoceros (Ceratotherium simum simum) ovary; the closest relation of th ...[more]

PMID: 37848538

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Project description:With recent poaching of southern white rhinoceros (SWR [Ceratotherium simum simum]) reaching record levels, the need for a robust assurance population is urgent. However, the global captive SWR population is not currently self-sustaining due to the reproductive failure of captive-born females. Dietary phytoestrogens have been proposed to play a role in this phenomenon, and recent work has demonstrated a negative relationship between diet estrogenicity and fertility of captive-born female SWR. To further examine this relationship, we compared gut microbial communities, fecal phytoestrogens, and fertility of SWR to those of another rhinoceros species-the greater one-horned rhinoceros (GOHR [Rhinoceros unicornis]), which consumes a similar diet but exhibits high levels of fertility in captivity. Using 16S rRNA amplicon sequencing and mass spectrometry, we identified a species-specific fecal microbiota and three dominant fecal phytoestrogen profiles. These profiles exhibited various levels of estrogenicity when tested in an in vitro estrogen receptor activation assay for both rhinoceros species, with profiles dominated by the microbial metabolite equol stimulating the highest levels of receptor activation. Finally, we found that SWR fertility varies significantly not only with respect to phytoestrogen profile, but also with respect to the abundance of several bacterial taxa and microbially derived phytoestrogen metabolites. Taken together, these data suggest that in addition to species differences in estrogen receptor sensitivity to phytoestrogens, reproductive outcomes may be driven by the gut microbiota's transformation of dietary phytoestrogens in captive SWR females.IMPORTANCE Southern white rhinoceros (SWR) poaching has reached record levels, and captive infertility has rendered SWR assurance populations no longer self-sustaining. Previous work has identified dietary phytoestrogens as a likely cause of this problem. Here, we investigate the role of gut microbiota in this phenomenon by comparing two rhinoceros species to provide the first characterizations of gut microbiomes for any rhinoceros species. To our knowledge, our approach, combining parallel sequencing, mass spectrometry, and estrogen receptor activation assays, provides insight into the relationship between microbially mediated phytoestrogen metabolism and fertility that is novel for any vertebrate species. With this information, we plan to direct future work aimed at developing strategies to improve captive reproduction in the hope of alleviating their threat of extinction.

Project description:All species in the extant Rhinocerotidae family are experiencing increased threats in the wild, making captive populations essential genetic reservoirs for species survival. However, managed species face distinct challenges in captivity, resulting in populations that are not self-sustaining. Captive southern white rhinoceros (Ceratotherium simum simum) have low reproductive rates and presumed acyclicity is common among females. Although many females fail to ovulate, follicle growth may occur and ovulation can be hormonally induced. Female southern white rhino (n = 6), housed as a bachelorette group, were determined to be ovulatory (n = 1) or anovulatory (n = 5) by serial ultrasound and fecal progestagen analysis. When follicles reached pre-ovulatory size (~35 mm), females (n = 4) were induced to ovulate in 11 trials with a GnRH analog (4.5 mg, SucroMate™) via single intramuscular injection. Nine trials resulted in ovulation (81.8%), all between 36 and 48 hours post-treatment. Ovulations were confirmed by progestagen elevation above baseline coincident with visualization of a corpus luteum (CL). Luteal phases were characterized as short (<50 days) or long (≥50 days). Between short and long cycles, only the number of days of progestagen above baseline was significantly different (P < 0.05), while days with visible luteal structures was not significant (P = 0.11). Both cycle types were observed following both spontaneous and induced ovulations. Furthermore, we showed that longer cycle lengths do not necessarily indicate early pregnancy loss as none of the females were bred or inseminated during the study. While anovulation is common in the southern white rhino captive population, ovulation induction can be achieved efficiently and predictably for use in conjunction with artificial insemination or to facilitate natural breeding. This information will lead to more efficient use of assisted reproductive technologies to overcome reproductive challenges in this species and to generate genetically healthy captive populations as a hedge against extinction.

Project description:Gut microbiota are essential to nutrient metabolism and the maintenance of hindgut health. The characterization of faecal bacterial communities from healthy individuals is important for the establishment of baseline data that can be compared to periods of gut dysbiosis. Diet is a key determinant of the faecal microbial community structure and generation of volatile fatty acids, a main energy source for the host. While rhinoceroses are herbivores, black rhinoceroses are browsers and white rhinoceroses are grazers. The objective of our study was to characterize and compare diets, faecal bacterial communities, nutrients and metabolites between and amongst Southern white rhinoceroses and Southern black rhinoceroses (n = 3 rhinos/species) managed at Disney's Animal Kingdom® . Faecal bacterial communities were similar between individual white rhinos and dissimilar between species and individual black rhinos. Faecal butyrate and propionate molar proportions and concentrations were greater in black rhinos than white rhinos, whereas lactate was greater in white rhinos. The Shannon diversity, total operational taxonomic units, and relative abundance of Firmicutes were greater in white than black rhinos. The relative abundance of Proteobacteria in faeces from black rhinos was 3-fold greater than from white rhinos. One black rhino had a greater relative abundance of Verrucomicrobia (7.45 ± 1.31%) than all other individual rhinos (0.01-1.37%). White rhinoceroses demonstrated similar abundances of bacterial phyla and communities between one another and by individual, while black rhinoceroses were more dissimilar by individual. The dissimilarities between black rhinos were suspected to be due to total diet consumption variability, including browse diversity, and lack of direct contact. In contrast, the white rhinos commingled (i.e. nose-to-nose contact) and consumed similar amounts of hay, pellets and training items. These results suggest that species-specific diets and the individual contribute to differences in faecal bacterial communities, nutrients and metabolites between black and white rhinos housed at the same institution.

Dataset Information

The neonatal southern white rhinoceros ovary contains oogonia in germ cell nests.

Publications

The neonatal southern white rhinoceros ovary contains oogonia in germ cell nests.

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