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.

Prospective, randomized, double blind comparison of suture materials with and without triclosan in dogs undergoing tibial plateau leveling osteotomy

Objectives

To determine if triclosan-impregnated suture decreases surgical site infection rates after tibial plateau leveling osteotomy (TPLO) in dogs.

Sample population

There were 116 dogs with naturally occurring cranial cruciate ligament disease presenting for treatment with TPLO.

Procedures

Written consent was obtained by all clients in order to be included in this study. Dogs were randomly assigned a suture type immediately before the start of anesthesia. Infection rates were compared between the suture groups, as were the gender, duration of anesthesia, duration of surgery, age of dog, weight, length of incision, and stifle side. Direct examination by a veterinarian was conducted at 24 h, 10 to 14 d, and 8 to 12 wk after surgery. If the dogs did not return for direct examination, owners were contacted by a veterinarian and phone interviews were conducted.

Results

Overall, 12.9% of the incisions were diagnosed with a surgical site infection (SSI). The SSI rate for dogs that received the triclosan suture was 5.35% (3/56), and the rate for dogs that received the regular suture was 19.64% (11/56), with P = 0.016. The duration of anesthesia, duration of surgery, age, weight, length of incision, and right versus left stifle did not show a significant difference in infection rates. The suture type did have a significant effect, and triclosan-impregnated suture had a decreased infection rate when compared to regular suture. Gender also had a significant effect, with P = 0.032.

Conclusion

Triclosan-impregnated suture decreased SSI when used for closure in dogs undergoing TPLO. Triclosan-impregnated suture may be considered a material of choice to close surgical wounds at risk of SSI when implants are used.

Captive diet does not influence exploration behavior upon reintroduction to the wild in a critically endangered amphibian

Exploration behavior can have profound effects on individual fitness. Consequently, knowledge of the proximate mechanisms underpinning exploration behavior may inform conservation breeding programs (CBPs) for threatened species. However, the environmental factors that influence exploration behavior in captivity and during the reintroduction process remain poorly understood. Dietary micronutrients, such as carotenoids, are known to affect the expression of energetically costly behavioral traits, and theoretically may also influence the degree of exploration behavior in various contexts. Here, we investigate whether dietary β-carotene supplementation in captivity influences exploration behavior upon reintroduction to the wild in the critically endangered southern corroboree frog, Pseudophryne corroboree. We conducted a manipulative dietary experiment where captive bred P. corroboree were supplemented with different doses of β-carotene for 40 weeks prior to release. Frogs (n = 115) were reintroduced to the wild using a soft-release approach, where they were released into field enclosures specifically designed for this species. Upon reintroduction, the frogs’ initial exploration behavior was measured using a standardized behavioral assay. There was no effect of diet treatment on any measure of exploration behavior (mean latency to leave the initial refuge, time spent mobile within the release apparatus and latency to disperse into the field enclosure). However, there was a significant relationship between individual body size and latency to leave the refuge, whereby smaller individuals left the refuge more rapidly. While these findings provide no evidence that β-carotene at the dosages tested influences P. corroboree exploration behavior in a reintroduction context, the effect of body size draws attention to the potential for bodily state to influence exploration behavior. We discuss the need for ongoing research investigating the influence of captive diet on post release behavior, and highlight how knowledge concerning state-dependent behavior might help to inform and direct reintroduction programs.

Phylogenetic investigation of skin sloughing rates in frogs: relationships with skin characteristics and disease-driven declines

Amphibian skin is highly variable in structure and function across anurans, and plays an important role in physiological homeostasis and immune defence. For example, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis ( Bd), but interspecific variation in sloughing frequency is largely unknown. Using phylogenetic linear mixed models, we assessed the relationship between skin turnover rate, skin morphology, ecological traits and overall evidence of Bd-driven declines. We examined skin sloughing rates in 21 frog species from three continents, as well as structural skin characteristics measured from preserved specimens. We found that sloughing rate varies significantly with phylogenetic group, but was not associated with evidence of Bd-driven declines, or other skin characteristics examined. This is the first comparison of sloughing rate across a wide range of amphibian species, and creates the first database of amphibian sloughing behaviour. Given the strong phylogenetic signal observed in sloughing rate, approximate sloughing rates of related species may be predicted based on phylogenetic position. While not related to available evidence of declines, understanding variation in sloughing rate may help explain differences in the severity of infection in genera with relatively slow skin turnover rates (e.g. Atelopus).

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.

Dose and life stage-dependent effects of dietary beta-carotene supplementation on the growth and development of the Booroolong frog

Carotenoids are known for their antioxidant capacity and are considered to play an important role in vertebrate growth and development. However, evidence for their beneficial effects remains limited, possibly because very few studies have tested for dose effects across different life stages. The present study investigated the effect of various doses of dietary beta-carotene supplements on the growth and development of larval and post-metamorphic Booroolong frogs (Litoria booroolongensis). Larval and post-metamorphic basal diets (containing 0.015 and 0.005 mg g-1 total carotenoids, respectively) were supplemented with beta-carotene at one of four concentrations: 0 mg g-1, 0.1 mg g-1, 1 mg g-1 and 10 mg g-1. Each treatment included 72 replicate individuals, and individuals remained on the same diet treatment over both life stages (spanning 53 experimental weeks). Our results show that larvae receiving an intermediate (1 mg g-1) beta-carotene supplement dose grew faster than unsupplemented larvae (0 mg g-1), and metamorphosed earlier. After metamorphosis, there was no effect of the lowest supplement dose (0.1 mg g-1) on growth and development. However, juveniles fed the highest supplement dose (10 mg g-1) displayed significantly smaller body mass and lower body condition, compared to all other supplement doses, from 4-months through to sexual maturity (7-months). These findings indicate that beta-carotene supplementation has positive effects on growth and development, but only at intermediate doses, and only in the larval life stage. This knowledge may assist with amphibian conservation by expediting the rate that metamorphs can be generated in captive breeding programmes. More broadly, this is the first study to demonstrate both dose and life stage-dependent effects of dietary beta-carotene supplementation on vertebrate growth and development.

Interventions for reducing extinction risk in chytridiomycosis-threatened amphibians

Wildlife diseases pose an increasing threat to biodiversity and are a major management challenge. A striking example of this threat is the emergence of chytridiomycosis. Despite diagnosis of chytridiomycosis as an important driver of global amphibian declines 15 years ago, researchers have yet to devise effective large-scale management responses other than biosecurity measures to mitigate disease spread and the establishment of disease-free captive assurance colonies prior to or during disease outbreaks. We examined the development of management actions that can be implemented after an epidemic in surviving populations. We developed a conceptual framework with clear interventions to guide experimental management and applied research so that further extinctions of amphibian species threatened by chytridiomycosis might be prevented. Within our framework, there are 2 management approaches: reducing Batrachochytrium dendrobatidis (the fungus that causes chytridiomycosis) in the environment or on amphibians and increasing the capacity of populations to persist despite increased mortality from disease. The latter approach emphasizes that mitigation does not necessarily need to focus on reducing disease-associated mortality. We propose promising management actions that can be implemented and tested based on current knowledge and that include habitat manipulation, antifungal treatments, animal translocation, bioaugmentation, head starting, and selection for resistance. Case studies where these strategies are being implemented will demonstrate their potential to save critically endangered species.

Knot security and tensile strength of suture materials

OBJECTIVE

To evaluate knot security and tensile failure load of suture tied in simple interrupted, beginning continuous, and ending continuous patterns for 11 suture materials commonly used in small animal surgery.

STUDY DESIGN

Mechanical study.

METHODS

For each of 11 suture material types, and 5 knot sizes (2, 3, 4, 5, and 6 throws) 2 surgeons each tied 6 knots (n = 12 for each knot size in 11 suture materials). Three types of patterns were evaluated: a simple interrupted square knot, a square knot beginning a simple continuous pattern, and the knot ending a simple continuous pattern. All knots were incubated in healthy canine donor plasma at 40°C for a minimum of 24 hours. Sutures were evaluated for knot security (knots untied, suture failed by breaking, suture slipped from the clamps, or suture untied before testing) and maximum load carried before knot slippage or knot failure (termed tensile failure load).

RESULTS

Significant differences were found in knot security and tensile failure load among suture types. There was no significant difference between the simple interrupted knots and the knots at the beginning of a simple continuous pattern; however, both were significantly less likely to fail than the knots tied at the end of a simple continuous pattern. The number of throws per knot had a significant effect for knot security and tensile failure load. Surgeon experience had a significant effect on failure mode and tensile failure load.

CONCLUSIONS

Suture type, number of throws per knot (knot size), suture pattern, and surgeon experience play an important role in knot security and should be considered when performing surgery.

Clinical and histologic effects of intracardiac administration of propofol for induction of anesthesia in ball pythons (Python regius)

OBJECTIVE

To assess the clinical differences between induction of anesthesia in ball pythons with intracardiac administration of propofol and induction with isoflurane in oxygen and to assess the histologic findings over time in hearts following intracardiac administration of propofol.

DESIGN

Prospective randomized study.

ANIMALS

30 hatchling ball pythons (Python regius).

PROCEDURES

Anesthesia was induced with intracardiac administration of propofol (10 mg/kg [4.5 mg/lb]) in 18 ball pythons and with 5% isoflurane in oxygen in 12 ball pythons. Induction time, time of anesthesia, and recovery time were recorded. Hearts from snakes receiving intracardiac administration of propofol were evaluated histologically 3, 7, 14, 30, and 60 days following propofol administration.

RESULTS

Induction time with intracardiac administration of propofol was significantly shorter than induction time with 5% isoflurane in oxygen. No significant differences were found in total anesthesia time. Recovery following intracardiac administration of propofol was significantly longer than recovery following induction of anesthesia with isoflurane in oxygen. Heart tissue evaluated histologically at 3, 7, and 14 days following intracardiac administration of propofol had mild inflammatory changes, and no histopathologic lesions were seen 30 and 60 days following propofol administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Intracardiac injection of propofol in snakes is safe and provides a rapid induction of anesthesia but leads to prolonged recovery, compared with that following induction with isoflurane. Histopathologic lesions in heart tissues following intracardiac injection of propofol were mild and resolved after 14 days.