Antibiotics and oxygen availability affect the short-term storage of spermatozoa from the critically endangered booroolong frog, Litoria booroolongensis

The Effect of Gentamicin on the Motility of Hormonally Induced Spermatozoa of Toad Bufo bufo during Storage at 4°C

We studied the effect of antibiotic gentamicin at concentrations of 0.05, 0.1, 0.2, 0.4, and 1 mg/ml on the maintenance of sperm motility of the common toad Bufo bufo during cold storage of spermic urine samples at 4°C. Parameters of sperm motility during storage of samples with gentamicin at concentrations of 0.05-0.4 mg/ml did not differ significantly, but were higher (p<0.0001) than in the control (storage without antibiotic). Gentamicin at a concentration of 1 mg/ml had a negative effect on sperm motility. After 2 weeks of storage of toad spermic urine samples with gentamicin, the largest number of sperm was preserved when using antibiotic at a concentration of 0.4 mg/ml.

Refrigerated storage and cryopreservation of hormonally induced sperm in the threatened frog, Litoria aurea

As sperm cryopreservation and other assisted reproductive technologies (ARTs) advance in common amphibian species, focus on applying non-lethal sperm collection methods to the conservation and genetic management of threatened species is imperative. The goal of this study was to examine the application of logistically practical ART protocols in a threatened frog (Litoria aurea). First, we tested the efficacy of various concentrations of human chorionic gonadotropin (hCG) (20, 40 IU/g bodyweight) and Gonadotropin releasing hormone antagonist (0.25 µg/g and 0.5 µg/g body weight GnRH-a) on the induction of spermatozoa. Using the samples obtained from the previous trials, we tested the effect of cold storage and cryopreservation protocols on long-term refrigerated storage and post-thaw sperm recovery. Our major findings include: (1) high quality sperm were induced with 20 and 40 IU/g bodyweight of (hCG); (2) proportions of live, motile sperm post-thaw, were recovered at higher levels than previously reported for L. aurea (>50%) when preserved with 15% v/v DMSO and 1% w/v sucrose; and (3) spermic urine stored at 5 °C retained motility for up to 14 days. Our findings demonstrate that the protocols developed in this study allowed for successful induction and recovery of high-quality spermatozoa from a threatened Australian anuran, L. aurea, providing a prime example of how ARTs can contribute to the conservation of rare and threatened species.

Cryopreservation Cooling Rate Impacts Post-Thaw Sperm Motility and Survival in Litoria booroolongensis

The cryopreservation and storage of gametes (biobanking) can provide a long-term, low-cost option for the preservation of population genetic diversity and is particularly impactful when applied to manage selective breeding within conservation breeding programs (CBPs). This study aimed to develop a sperm cryopreservation protocol for the critically endangered Booroolong frog (Litoria booroolongensis) to capture founder genetics within the recently established (est. 2019) CBP for this species. Hormone-induced sperm release was achieved using established protocols, and spermic urine samples were collected over a 6-h period. Pooled spermic urine samples (n = 3 males) were divided equally between two cryoprotectant (CPA) treatments and diluted by 1:5 (sperm:CPA) with either 15% (v/v) dimethyl sulfoxide + 1% (w/v) sucrose in simplified amphibian Ringer's (SAR; CPAA) or 10% (v/v) dimethylformamide + 10% (w/v) trehalose dihydrate in SAR (CPAB). The samples were cryopreserved in 0.25 mL straws using either a programmable freezer (FrA) or an adapted dry shipper method (FrB). The thawed samples were activated via dilution in water and assessed for viability and motility using both manual assessment and computer-assisted sperm analysis (CASA; 0 h, 0.5 h post-thaw). Upon activation, the survival and recovery of motility (total motility, forward progression and velocity) of cryopreserved sperm suspensions were higher for sperm preserved using FrB than FrA, regardless of CPA composition. This work supports our long-term goal to pioneer the integration of biobanked cryopreserved sperm with population genetic management to maximize restoration program outcomes for Australian amphibian species.

The Increasing Role of Short-Term Sperm Storage and Cryopreservation in Conserving Threatened Amphibian Species

Multidisciplinary approaches to conserve threatened species are required to curb biodiversity loss. Globally, amphibians are facing the most severe declines of any vertebrate class. In response, conservation breeding programs have been established in a growing number of amphibian species as a safeguard against further extinction. One of the main challenges to the long-term success of conservation breeding programs is the maintenance of genetic diversity, which, if lost, poses threats to the viability and adaptive potential of at-risk populations. Integrating reproductive technologies into conservation breeding programs can greatly assist genetic management and facilitate genetic exchange between captive and wild populations, as well as reinvigorate genetic diversity from expired genotypes. The generation of offspring produced via assisted fertilisation using frozen-thawed sperm has been achieved in a small but growing number of amphibian species and is poised to be a valuable tool for the genetic management of many more threatened species globally. This review discusses the role of sperm storage in amphibian conservation, presents the state of current technologies for the short-term cold storage and cryopreservation of amphibian sperm, and discusses the generation of cryo-derived offspring.

Impact of oestrus synchronization devices on ewes vaginal microbiota and artificial insemination outcome

Introduction

The low pregnancy rate by artificial insemination in sheep represents a fundamental challenge for breeding programs. In this species, oestrus synchronization is carried out by manipulating hormonal regimens through the insertion of progestogen intravaginal devices. This reproductive strategy may alter the vaginal microbiota affecting the artificial insemination outcome.

Methods

In this study, we analyzed the vaginal microbiome of 94 vaginal swabs collected from 47 ewes with alternative treatments applied to the progesterone-releasing intravaginal devices (probiotic, maltodextrin, antibiotic and control), in two sample periods (before placing and after removing the devices). To our knowledge, this is the first study using nanopore-based metagenome sequencing for vaginal microbiome characterization in livestock.

Results

Our results revealed a significant lower abundance of the genera Oenococcus (Firmicutes) and Neisseria (Proteobacteria) in pregnant compared to non-pregnant ewes. We also detected a significant lower abundance of Campylobacter in the group of samples treated with the probiotic.

Discussion

Although the use of probiotics represents a promising practice to improve insemination results, the election of the suitable species and concentration requires further investigation. In addition, the use of progestogen in the synchronization devices seemed to increase the alpha-diversity and decrease the abundance of harmful microorganisms belonging to Gammaproteobacteria and Fusobacteriia classes, suggesting a beneficial effect of their use.

The impact of time and environmental factors on the mitochondrial vesicle and subsequent motility of amphibian sperm

For amphibian species that display external fertilization in an aquatic environment, hypoosmotic shock to sperm cells can quickly result in damage to cellular structure and function. This study sought to determine how fertilization media osmolality, temperature, and time impact the stability of the mitochondrial vesicle's association with the sperm head and thus motility and quality of forward progression. The presence of the mitochondrial vesicle and its relationship with sperm motility and quality of forward progression were analyzed in sperm samples from the Fowler's toad (Anaxyrus fowleri) (n = 10) when held for six hours under two temperatures and four osmolalities. Results indicated that the presence of the mitochondrial vesicle is needed for sperm motility over time (p < 0.001), where higher osmolalities (p < 0.001) and lower temperatures (p < 0.001) correlated with maintaining the vesicle attachment to the spermatozoa. The higher osmolality of spermic urine was the most important factor for maintaining higher quality of forward progressive motility (p < 0.01) of spermatozoa. Sperm samples held at 4 °C and 40 mOsm/kg had the longest half-life for motility (540 min) and quality of forward progression (276 min), whereas sperm held at 22 °C and 2.5 mOsm/kg had the shortest half-life for motility (7 min) and quality of forward progression (18 min). Special attention should be given to the osmolality and temperature of fertilization solutions, or breeding tank water, when developing cold storage protocols for toad sperm or reproducing animals to ensure the retention of the mitochondrial vesicle for maximum fertilization capability.

The Use of Probiotics for Management and Improvement of Reproductive Eubiosis and Function

Reproductive tract dysbiosis, due to the action of pathogens and/or unhealthy lifestyle, has been related to many reproductive diseases and disorders in mammalian species. Classically, such a problem has been confronted by the administration of antibiotics. Despite their effectiveness for controlling disease, treatments with antibiotics may negatively affect the fertility of males and females and, mainly, may induce antibiotic resistance. Accordingly, safer alternatives for maintaining reproductive system eubiosis, such as probiotics, are required. The present review summarizes the current knowledge on the biodiversity of the microbiota at the reproductive tract, possible changes in the case of dysbiosis, and their relationships with adequate reproductive health and functioning in both females and males. Afterwards, mechanisms of action and benefits of different probiotics are weighed since the biological activities of probiotics may provide a promising alternative to antibiotics for maintaining and restoring reproductive eubiosis and function. However, at present, it is still necessary for further research to focus on: (a) identifying mechanisms by which probiotics can affect reproductive processes; (b) the safety of probiotics to the host, specifically when consumed during sensitive reproductive windows such as pregnancy; and (c) the hazards instructions and regulatory rules required for marketing these biological-based therapies with sufficient safety. Thus, in this review, to draw a comprehensive overview with a relatively low number of clinical studies in this field, we showed the findings of studies performed either on human or animal models. This review strategy may help provide concrete facts on the eligible probiotic strains, probiotics colonization and transfer route, and prophylactic and/or therapeutic effects of different probiotic strains.

Fertilization potential of cold-stored Fowler's toad (Anaxyrus fowleri) spermatozoa: temporal changes in sperm motility based on temperature and osmolality

Asynchrony of gamete release is problematic in amphibian captive breeding programs but can be overcome by short-term storage of spermatozoa. Hormonally induced sperm from the model species Anaxyrus fowleri were used to determine storage conditions for optimal fertilisation capacity. Sperm motility was measured over time, as a function of storage temperature (4°C or 22°C) and solution osmolality (7-40mOsm/kg). Sperm at 40mOsm/kg (spermic urine) stored at 4°C exhibited higher motility compared to 22°C. Also, sperm stored at 40mOsm/kg retained higher motility compared to sperm stored below 15mOsm/kg at both temperatures. Under optimal storage conditions (40mOsm and 4°C) a 30% decrease in sperm motility occurred within 24h, however, subsequent loss of sperm motility was lower (<10%/day) for days2-8 thereafter. Sperm samples stored for 1-8days under optimal conditions were tested for fertilising capacity by conducting in vitro fertilisation trials. Sperm stored for 8days yielded 48% neurula development, similar to sperm stored for 1day, which produced 60% neurula development. Overall, sperm stored for up to 8days at 4°C as spermic urine retained fertilising capacity and thus can be used to circumvent asynchronous gamete release in assisted breeding efforts for amphibians.

Determining the effects of sperm activation in anuran cloaca on motility and DNA integrity in Epidalea calamita (Bufonidae)

The effect of time inside the animal's cloaca on sperm quality after hormone-induced spermiation is unknown. However, this knowledge is critical for the development of assisted reproductive biotechnologies in amphibians. Out-of-season spermatozoa were collected from Epidalea calamita for 4h after injection of 10IU g-1 human chorionic gonadotrophin either hourly (Group I (n=10); four samples per male) or every 2h (Group II (n=9); two samples per male). Sperm samples were assessed for motility and DNA integrity using the sperm chromatin dispersion (SCD) test and the sperm chromatin structure assay (SCSA). The collection strategy affected total motility (mean (±s.e.m.) 84.4±9.9% vs 73.6±16.7% in Group I and II respectively; P=0.014) and the sperm motility index (67.6±17.7% vs 57.6±16.3% in Group I and II respectively; P=0.034). There was a significant effect of the male in Group II, but not in Group I. In Group I, the quality of the first samples collected was lower than that of samples collected thereafter (P ≤ 0.032). No significant correlations were found between the results of the SCD test and SCSA, showing that these techniques provide different information in this species. In conclusion, collecting spermatozoa every hour resulted in better sperm quality and may be more efficient. However, the between-male differences were considerable and collection of spermatozoa at just 1h after hormone treatment produced lower-quality spermatozoa.

Efficacy of hormone stimulation on sperm production in an alpine amphibian (Anaxyrus boreas boreas) and the impact of short-term storage on sperm quality

The Southern Rocky Mountain boreal toad (Anaxyrus boreas boreas) has disappeared from much of its range in the alpine regions of Central and Western North America, and restoration efforts are compromised by limited knowledge of this species' reproductive biology. This study aimed to establish whether assisted reproductive techniques could be used to improve breeding output in captive boreal toads by determining the most effective concentration of human chorionic gonadotropin (hCG) for induction of spermiation and viability of sperm during cold storage. Male toads (n = 21) were treated with a Low (3 IU g^-1), Medium (10 IU g^-1), or High (15 IU g^-1) concentration of hCG and spermic urine samples were collected over 24 hrs. Treatment effectiveness was evaluated by measuring the response rate, Total Motility (TM), Forward Progressive Motility (FPM), Quality of FPM (QFPM), and concentration. For short-term cold storage, spermic urine samples (n = 13) were stored at 4 °C for 14 days and sperm TM and FPM monitored daily. All treatments induced spermiation; however, a greater number of toads produced sperm in the Medium and High treatments compared to the Low. Overall, TM, FPM, QFPM and sperm concentration were similar across all three treatments, but variation existed in the timing and duration of peak sperm production. Sperm motility was maintained for up to 14 days in cold storage, although the quality slowly decreased over time. An effective reproduction strategy for the boreal toad will provide a means to improve captive breeding efforts and increase our understanding of the reproductive physiology of alpine Bufonids.

Short-term storage of tiger salamander (Ambystoma tigrinum) spermatozoa: The effect of collection type, temperature and time

The aims of this project were to characterize tiger salamander (Ambystoma tigrinum) spermatozoa motility over time, when excreted as either milt or spermic urine prior to packaging into a spermatophore, and to determine the effect of temperature on sperm motility. A split-plot design was utilized to assess the motility of the two pre-spermatophore sample types at two temperatures, 0°C and 20°C (n = 10 for each treatment). Spermiation was induced through exogenous hormone treatment of luteinizing hormone releasing hormone analog in order to collect both milt and spermic urine, which were evaluated for motility, divided into two separate aliquots, and subsequently stored in either an ice-bath (0°C) or on the benchtop (20°C). The decay rate of sperm motility was assessed by reevaluating subsamples at 0.5, 1, 2, 3, 5, 7, and 24 hours following the initial assessment. Results showed that sperm stored at 0°C had significantly higher progressive, non-progressive, and total motility for both sperm collection types over time. An interaction was found between collection type and time, with milt exhibiting lower initial motility that was more sustainable over time, compared to spermic urine. For both milt and spermic urine, motility decreased rapidly with storage duration, indicating samples should be used as soon as possible to maximize motility for in-vitro fertilization and cryopreservation. This is the first study to describe the differences in sperm motility between milt and spermic urine from an internally fertilizing caudate and demonstrates the benefits of near freezing temperatures on sperm longevity.

Sperm collection and storage for the sustainable management of amphibian biodiversity

Current rates of biodiversity loss pose an unprecedented challenge to the conservation community, particularly with amphibians and freshwater fish as the most threatened vertebrates. An increasing number of environmental challenges, including habitat loss, pathogens, and global warming, demand a global response toward the sustainable management of ecosystems and their biodiversity. Conservation Breeding Programs (CBPs) are needed for the sustainable management of amphibian species threatened with extinction. CBPs support species survival while increasing public awareness and political influence. Current CBPs only cater for 10% of the almost 500 amphibian species in need. However, the use of sperm storage to increase efficiency and reliability, along with an increased number of CBPs, offer the potential to significantly reduce species loss. The establishment and refinement of techniques over the last two decades, for the collection and storage of amphibian spermatozoa, gives confidence for their use in CBPs and other biotechnical applications. Cryopreserved spermatozoa has produced breeding pairs of frogs and salamanders and the stage is set for Lifecycle Proof of Concept Programs that use cryopreserved sperm in CBPs along with repopulation, supplementation, and translocation programs. The application of cryopreserved sperm in CBPs, is complimentary to but separate from archival gene banking and general cell and tissue storage. However, where appropriate amphibian sperm banking should be integrated into other global biobanking projects, especially those for fish, and those that include the use of cryopreserved material for genomics and other research. Research over a broader range of amphibian species, and more uniformity in experimental methodology, is needed to inform both theory and application. Genomics is revolutionising our understanding of biological processes and increasingly guiding species conservation through the identification of evolutionary significant units as the conservation focus, and through revealing the intimate relationship between evolutionary history and sperm physiology that ultimately affects the amenability of sperm to refrigerated or frozen storage. In the present review we provide a nascent phylogenetic framework for integration with other research lines to further the potential of amphibian sperm banking.

Hormonal induction of spermiation in a Eurasian bufonid (Epidalea calamita)

BACKGROUND

Amphibian diversity is declining at an alarming rate due to habitat loss, invasive species, climate change and diseases. Captive assurance colonies have been established for some species at risk; however, many species do not breed well in captivity and the development of assisted reproductive technologies (ART) is critical to help sustain genetic diversity. To date, the majority of the work has been accomplished in species from the American continent and Australia, and there is a need to address similar breeding challenges in Eurasian and African species of amphibians.

METHODS

The aim of this study was to develop a hormone protocol for stimulation of spermiation in Epidalea calamita as a model for Eurasian bufonids. Hence, the effect on sperm production and quality of three doses of chorionic gonadotropin hormone (5, 10 and 15 IU hCG/g) over time (1 to 24 h) was evaluated. In addition, cold storage (at 5 °C) of sperm for 24 and 48 h and three frequencies for hormonal treatment (weekly, biweekly and monthly) were examined.

RESULTS

Hormone concentrations of 10 or 15 IU of hCG induced spermiation in 100% of males and produced sperm of comparable quality, while 5 IU hCG stimulated spermiation in only 40% of males. Total motility peaked between 1 to 4 h post-treatment with 10 IU hCG, whereas treatment with 15 IU hCG peaked between 2 to 6 h. After 24 h of cold storage total motility dropped by 20% and forward motility dropped by 10% for both the 10 and 15 IU treatments. Weekly hormone administration resulted in higher variation between trials in all motility parameters and a lower overall Total Motility and Forward Movement. Furthermore, the effect of exogenous hormone treatment overlapped between the last two trials in the weekly frequency. Sperm concentration was higher in the first trial for all frequencies but showed no differences among other trials.

CONCLUSIONS

Overall, these results show that hormone concentration, time after treatment, frequency of hormone treatment and cold storage should be borne in mind when developing a hormone stimulation protocol for Eurasian amphibian species.

Hormone-induced spawning of the critically endangered northern corroboree frog Pseudophryne pengilleyi

Fundamental knowledge of the optimal hormone concentrations required to stimulate amplexus and spawning in breeding pairs of amphibians is currently lacking, hindering our understanding of the proximate mechanisms underpinning mating behaviour. The present study investigated the effects of: (1) the dose of a gonadotropin-releasing hormone analogue (GnRH-a) administered; (2) male-female hormone administration interval; and (3) topical application of GnRH-a, on spawning success in the northern corroboree frog. Administration of GnRH-a at doses of 0.5, 1.0 and 2.0μgg-1 were highly successful, with a significantly greater proportion of hormone-treated pairs ovipositing (89-100%) compared with the 0μgg-1 treatment (22%). Of the hormone-treated pairs, those receiving 0.5μgg-1 GnRH-a exhibited the highest fertilisation success (61%). Administration of GnRH-a to males and females simultaneously (0h) was more effective than injecting males either 48 or 24h before the injection of females. Overall, administration of GnRH-a was highly successful at inducing spawning in northern corroboree frogs. For the first time, we also effectively induced spawning following the topical application of GnRH-a to the ventral pelvic region. Topical application of GnRH-a eliminates the need for specialised training in amphibian injection, and will allow assisted reproductive technologies to be adopted by a greater number of captive facilities globally.

Hormone-induced sperm-release in the critically endangered Booroolong frog (Litoria booroolongensis): effects of gonadotropin-releasing hormone and human chorionic gonadotropin

Research into the development of reproductive technologies for amphibians has increased in recent years due to the rapid decline of amphibian species globally. Reproductive technologies have great potential to overcome captive breeding failure and improve the propagation and genetic management of threatened species. However, the incorporation of these technologies into conservation breeding programs has been protracted, primarily as a result of trial-and-error approaches to the refinement of hormone therapies. The present study investigated the effects of: (1) GnRH-a dose (0, 0.5, 1, 2, 4, 8 or 16 μg g-1), and (2) hCG dose (0, 2.5, 5, 10, 20 or 40 IU g-1), on the sperm-release response of the critically endangered Booroolong frog. Administration of GnRH-a at a dose of 0.5 μg g-1 resulted in the greatest number of sperm released (mean total sperm = 3.5 ×106, n = 11). Overall, hCG was more effective at eliciting spermiation in Booroolong frogs, with peak sperm release (mean total sperm = 25.1 ×106, n = 10) occurring in response to a dose of 40 IU g-1. Sperm output in response to 40 IU g-1 hCG was greatest between 1 and 6 h and steadily declined between 8 and 24 h post-hormone administration. Percent sperm motility peaked between 4 and 10 h (58.1-62.7%), and sperm velocity between 4 and 12 h (24.3-27.2 μm s-1). Booroolong frogs join a small, but growing number of amphibian species that exhibit improved spermiation in response to hCG. Further research is required to identify optimal hormone-induction protocols for threatened amphibians and expedite the incorporation of reproductive technologies into CBPs.

The Role of Reproductive Technologies in Amphibian Conservation Breeding Programs

Anthropogenic environmental change has led to unprecedented rates of species extinction, presenting a major threat to global biodiversity. Among vertebrates, amphibians have been most severely impacted, with an estimated 41% of species now threatened with extinction. In response to this biodiversity crisis, a moral and ethical obligation exists to implement proactive interventionist conservation actions to assist species recovery and decelerate declines. Conservation breeding programs have been successfully established for several threatened amphibian species globally, aiming to prevent species' extinction by maintaining genetically representative assurance colonies ex situ while providing individuals for population augmentation, translocation, and reestablishment in situ. Reproductive technologies have enormous potential to enhance the propagation and genetic management of threatened species. In this review, we discuss the role of reproductive technologies in amphibian conservation breeding programs and summarize technological advancements in amphibian hormone therapies, gamete storage, and artificial fertilization.

Effect of long-term dietary beta-carotene supplementation on sperm concentration and motility in an endangered amphibian

Dietary carotenoids have a high antioxidant capacity, so it has been hypothesised that carotenoid supplimentation will improve sperm production and quality by protecting sperm from oxidative damage. The effects of carotenoids on sperm have only been assessed in three vertebrate species, and evidence for improved sperm concentration and motility remains equivocal. One reason for this might be that in most studies there has not been an assessment of the effects of single carotenoid compounds over a range of doses. Applied research focused on developing ways to improve sperm quality could benefit the captive breeding and conservation of threatened species. The aim of the present study was to assess a dose-dependent effect of beta-carotene supplementation on sperm concentration and motility in the endangered booroolong frog (Litoria booroolongensis). Individuals were supplemented with one of four beta-carotene doses (0, 0.1, 1 and 10 mg/g) from hatching until sexual maturity (53 weeks). Sperm concentration was determined prior to activation, and percent sperm motility and sperm velocity were measured at 0, 3 and 6 h post-activation using computer-assisted sperm analysis. Unexpectedly, beta-carotene had no significant effect on sperm concentration, percent motility or velocity at any time point, providing no evidence for beneficial effects. Findings of the present study indicate there are likely to be species-specific differences in sperm production and motility that influence the risk of oxidative damage to sperm and dependence on dietary antioxidants to inhibit these detrimental effects.

Seminal fluid metabolome and epididymal changes after antibiotic treatment in mice

Paternal environment can induce detrimental developmental origins of health and disease (DOHaD) effects in resulting offspring and even future descendants. Such paternal-induced DOHaD effects might originate from alterations in a possible seminal fluid microbiome (SFM) and composite metabolome. Seminal vesicles secrete a slightly basic product enriched with fructose and other carbohydrates, providing an ideal habitat for microorganisms. Past studies confirm the existence of a SFM that is influenced by genetic and nutritional status. Herein, we sought to determine whether treatment of male mice with a combination of antibiotics designed to target SFM induces metabolic alterations in seminal vesicle gland secretions (seminal fluid) and histopathological changes in testes and epididymides. Adult (10- to 12-week-old) National Institutes of Health (NIH) Swiss males (n = 10 per group) were treated with Clindamycin 0.06 mg/kg day, Unasyn (ampicillin/sulbactam) 40 mg/kg day and Baytril (enrofloxacin) 50 mg/kg day designed to target the primary bacteria within the SFM or saline vehicle alone. Fourteen-day antibiotic treatment of males induced metabolomic changes in seminal vesicles with inosine, xanthine and l-glutamic acid decreased but d-fructose increased in glandular secretions. While spermatogenesis was not affected in treated males, increased number of epididymal tubules showed cribriform growth in this group (7 antibiotic-treated males: 3 saline control males; P = 0.01). Antibiotic-treated males showed more severe cribriform cysts. Current findings suggest antibiotic treatment of male mice results in seminal fluid metabolome and epididymal histopathological alterations. It remains to be determined whether such changes compromise male reproductive function or lead to DOHaD effects in resulting offspring.

The effect of antioxidants on sperm motility activation in the Booroolong frog

Motile sperm can generate high levels of reactive oxygen species (ROS) post activation, and ROS can quickly accumulate to levels that impair motility and fertilising ability. The addition of antioxidants to sperm suspensions has been suggested as a means of reducing oxidative stress and enhancing sperm motility during and after sperm storage. Despite this, very few studies have attempted to experimentally test the effects of antioxidants on sperm motility activation in animals that use an external mode of fertilisation, espcially in amphibians. The present study aimed to investigate the effect of vitamin C and vitamin E on sperm motility activation in the Booroolong frog. Spermatozoa were activated in media containing either vitamin C (0, 0.05, 0.10, 0.15, 0.20, 0.25μgμL^-1) or vitamin E (0, 0.25, 0.50, 0.75, 1.0, 1.25 1.50, 1.75μgμL^-1). Sperm performance parameters (percent motility and velocity) were assessed using CASA at 0, 1, 2, 3, 4, 5 and 6h post-activation. Contrary to expectations, vitamin C supplementation was detrimental to sperm motility across all tested concentrations, while vitamin E had no effect. Further investigation on the endogenous antioxidant system of anuran sperm is required to ascertain whether alternative antioxidants may be more suitable at reducing ROS produced during sperm activation and improving sperm motility activation in vitro.

The effect of gentamicin on sperm motility and bacterial abundance during chilled sperm storage in the Booroolong frog

Antibiotics can inhibit bacterial contamination and extend sperm longevity during storage; a primary goal of captive facilities conducting biobanking and artificial fertilisation (AF). This study evaluated the effects of gentamicin on the short-term storage of Booroolong frog sperm. Sperm suspensions were obtained via either testis maceration, or as spermic urine, following hormonal induction of sperm-release. The effect of 0, 1, 2, 3 or 4mgmL^-1 gentamicin on bacterial abundance (CFUmL^-1) was determined and sperm motility assessed. In both testis macerate samples and spermic urine samples, gentamicin administered at intermediate-to-high doses (2, 3 & 4mgmL^-1) eliminated, or significantly reduced, bacterial abundance. Sperm samples obtained via testis maceration exhibited significantly lower sperm motility at the highest doses (3 & 4mgmL^-1). All remaining treatments (0, 1 & 2mgmL^-1) were statistically similar and maintained sperm motility >55%. Sperm samples obtained as spermic urine exhibited no difference in sperm motility or velocity when treated with gentamicin at any dose. While antibiotic treatment did not improve sperm longevity as predicted, this is the first study to demonstrate that antibiotic treatment can reduce bacterial abundance without compromising sperm motility in an anuran amphibian. Antibiotic supplementation may be an important tool for reducing pathogen transmission where sperm samples are transferred between captive institutions for biobanking and AF.

Cryopreservation and other assisted reproductive technologies for the conservation of threatened amphibians and reptiles: bringing the ARTs up to speed

Amphibians and reptiles are experiencing serious declines, with the number of threatened species and extinctions growing rapidly as the modern biodiversity crisis unfolds. For amphibians, the panzootic of chytridiomycosis is a major driver. For reptiles, habitat loss and harvesting from the wild are key threats. Cryopreservation and other assisted reproductive technologies (ARTs) could play a role in slowing the loss of amphibian and reptile biodiversity and managing threatened populations through genome storage and the production of live animals from stored material. These vertebrate classes are at different stages of development in cryopreservation and other ARTs, and each class faces different technical challenges arising from the separate evolutionary end-points of their reproductive biology. For amphibians, the generation of live offspring from cryopreserved spermatozoa has been achieved, but the cryopreservation of oocytes and embryos remains elusive. With reptiles, spermatozoa have been cryopreserved in a few species, but no offspring from cryopreserved spermatozoa have been reported, and the generation of live young from AI has only occurred in a small number of species. Cryopreservation and ARTs are more developed and advanced for amphibians than reptiles. Future work on both groups needs to concentrate on achieving proof of concept examples that demonstrate the use of genome storage and ARTs in successfully recovering threatened species to increase awareness and support for this approach to conservation.