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Bison are an ecologically and culturally important species on the European and North American continents. Their near extirpation was met with conservation efforts that prevented their extinction but left few animals or highly fragmented populations. Contemporary conservation efforts are focused on building ecologically and genetically sustainable bison herds for long-term conservation of the species. Assisted reproductive technologies (ARTs) can play a key role in building these herds by facilitating the movement of genetics in the form of gametes and embryos, while protecting animal well-being and ensuring biosecurity of existing bison herds. In addition, ARTs such as gamete and embryo cryopreservation can be used to protect against future losses of genetic diversity through biobanking. In this review, a brief summary of basic bison reproductive physiology is presented followed by an overview of the current state of ART in Bison bison (American bison) and Bison bonasus (European bison or wisent). Research on ART ranging from artificial insemination to in vitro embryo transfer and cloning is discussed with particular regard to the application of ART for conservation purposes. While significant progress has been made in ART for bison, there are still many opportunities to improve these technologies and expand their impact for bison conservation., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Mosquito-borne diseases are responsible for millions of human deaths every year, posing a massive burden on global public health. Mosquitoes transmit a variety of bacteria, parasites and viruses. Mosquito control efforts such as insecticide spraying can reduce mosquito populations, but they must be sustained in order to have long term impacts, can result in the evolution of insecticide resistance, are costly, and can have adverse human and environmental effects. Technological advances have allowed genetic manipulation of mosquitoes, including generation of those that are still susceptible to insecticides, which has greatly increased the number of mosquito strains and lines available to the scientific research community. This generates an associated challenge, because rearing and maintaining unique mosquito lines requires time, money and facilities, and long-term maintenance can lead to adaptation to specific laboratory conditions, resulting in mosquito lines that are distinct from their wild-type counterparts. Additionally, continuous rearing of transgenic lines can lead to loss of genetic markers, genes and/or phenotypes. Cryopreservation of valuable mosquito lines could help circumvent these limitations and allow researchers to reduce the cost of rearing multiple lines simultaneously, maintain low passage number transgenic mosquitoes, and bank lines not currently being used. Additionally, mosquito cryopreservation could allow researchers to access the same mosquito lines, limiting the impact of unique laboratory or field conditions. Successful cryopreservation of mosquitoes would expand the field of mosquito research and could ultimately lead to advances that would reduce the burden of mosquito-borne diseases, possibly through rear-and-release strategies to overcome mosquito insecticide resistance. Cryopreservation techniques have been developed for some insect groups, including but not limited to fruit flies, silkworms and other moth species, and honeybees. Recent advances within the cryopreservation field, along with success with other insects suggest that cryopreservation of mosquitoes may be a feasible method for preserving valuable scientific and public health resources. In this review, we will provide an overview of basic mosquito biology, the current state of and advances within insect cryopreservation, and a proposed approach toward cryopreservation of Anopheles stephensi mosquitoes., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Bison from Yellowstone National Park (YNP) have an important genetic history. As one of the few wild herds of bison with no evidence of cattle DNA introgression and a large enough population to maintain genetic diversity, they are considered a conservation priority for the species. Unfortunately, there is a high prevalence of the zoonotic disease brucellosis in the herd. Part of the management strategy for controlling the disease and herd size in YNP is to remove bison from the population during the winter migration out of the park. This interagency management cull provides an opportunity to collect a large number of oocytes from a wild bison population for genetic banking and research purposes. During the winters of 2014-2018, which is the nonbreeding season for bison, oocytes were collected post mortem and used to determine the effects of donor reproductive maturity and pregnancy status on oocyte quality and in vitro fertilization (IVF) outcomes, and to demonstrate the feasibility of producing healthy offspring. Cumulus oocyte complexes (COCs) were placed into an in vitro embryo production (IVP) system, and on days 7, 7.5, and 8 of in vitro culture (Day 0 = day of in vitro fertilization) embryos were assessed for developmental stage and quality prior to vitrification. Embryos were then stored in liquid nitrogen until the breeding season when a subset were warmed, cultured for 6 h, evaluated for survival, and transferred to healthy bison recipients. There were no significant differences in the ability of recovered COCs to support blastocyst development based on female reproductive maturity or pregnancy status (juvenile 79/959 (8.2%) vs sexually mature 547/6544 (8.4%); non-pregnant 188/2302 (8.2%) vs pregnant 556/6122 (9.1%)). Following the transfer of 15 embryos to 10 recipients, one healthy female calf was born. This work demonstrates that live offspring can be generated from COCs collected from YNP bison post mortem in the non-breeding season, and that gamete recovery can be a valuable tool for conservation of valuable genetics for this species while mitigating diseases like brucellosis., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

This study was conducted to optimize the cryopreservation of epididymal bison sperm harvested in the field. In the first experiment, epididymal bison sperm were treated with or without seminal plasma (n = 6) and cooled to 5 °C over 2 hours. In a separate experiment, glycerol was added at different times and sperm was held at 5 °C for different periods of time before cryopreservation (n = 11). In addition, epididymal sperm frozen with and without seminal plasma (n = 6) and after 4, 24, and 48 hours (n = 5) of equilibration at 5 °C, were evaluated for their in vitro fertilizing ability. Post-thaw motility of bison epididymal sperm was similar when cryopreserved with or without seminal plasma or when glycerol was added at either 0, 4, 24, or 48 hours before freezing (P > 0.05). However, sperm incubated at 5 °C for 24 hours before freezing exhibited higher percentages of motile sperm (44% vs. 35% for 4 hours or 48 hours, P < 0.05). Fertilization rates of bison oocytes were not different for any treatments. Chilling the whole epididymis for 24 or 48 hours resulted in complete loss of sperm viability. In conclusion, bison epididymal sperm can be chilled outside of the epididymis for at least 48 hours before cryopreservation without compromising post-thaw sperm motility providing flexibility for technicians performing field collections., (Copyright © 2016 Elsevier Inc. All rights reserved.)

In a time of accelerated extinction rates and biodiversity loss, it may seem illogical to be concerned with methods limiting the reproduction of wild populations; however, there is an urgent need to inhibit the proliferation of a wide variety of species. The range of animals for which fertility control is desired makes the development of a single method impossible. The various reproductive strategies used by individual species, the desired outcome of contraceptive programs (reversible or irreversible; male or female directed) and our ignorance of the reproductive biology of many endangered species necessitate thorough species-specific investigations. As fertility control in humans is a reality and research into methods of fertility control is more advanced, humans serve as a model for developing contraceptive approaches for wild species. Population control by traditional methods (indirect or direct intervention by culling, poisoning, translocation, etc.) is increasingly unacceptable to the public, making human studies even more valuable for finding solutions to overabundant wild populations. This review compares and contrasts the range of contraceptive methods used in both wildlife and humans.