Vitrification of Iberian wolf (Canis lupus signatus) sperm: A possible alternative to conventional cryopreservation

Sperm vitrification is a simple, inexpensive method that allows the cryopreservation of sperm in the field and for endangered species is a useful alternative to conventional freezing. The study, therefore, is focused on the suitability of vitrification for cryopreserving Iberian wolf sperm and utilizing plasma testosterone concentration as a marker for procedure efficacy. Sperm and blood samples were collected from 17 wolves. There were 14 samples suitable for cryopreservation (12 ejaculated and two epididymal). Immediately after collection, these samples were proportioned into two aliquots for conventional freezing using a Tris-citric acid-glucose based extender (TCG) or vitrification utilizing an animal protein free extender (HTF®). Vitrification occurred by directly plunging a sperm suspension into liquid nitrogen. Sperm were assessed for motility, membrane integrity, acrosomal status and DNA integrity before and after cryopreservation. With both techniques, there were similar post-thaw/warming results (P > 0.05) with respect to progressive motility, kinetic variables VCL, VSL, VAP and BCF, DNA fragmentation, sperm membrane functionality and morphological abnormalities. Total motile sperm, progression ratios LIN, STR, and WOB, the ALH, sperm viability and sperm with intact membrane and acrosome were greater (P < 0.05) in the conventional frozen-thawed sperm than vitrified-warmed sperm. Plasma testosterone concentrations varied from 0.0 ng/mL to 7.7 ng/mL. For epididymal sperm, sperm motility and viability following thawing were greater in vitrified-warmed samples than conventionally-frozen samples; however, small sample numbers precluded statistical analysis. When considered together, these results indicate vitrification may be a possible alternative for wolf sperm cryopreservation.

Zoo animals as sentinels for Schmallenberg virus monitoring in Spain

Schmallenberg virus (SBV) is a newly emerged vector-borne pathogen that affects many domestic and wild animal species. A serosurvey was carried out to assess SBV exposure in zoo animals in Spain and to determine the dynamics of seropositivity in longitudinally sampled individuals. Between 2002 and 2019, sera from 278 animals belonging to 73 different species were collected from five zoos (A-E). Thirty-one of these animals were longitudinally sampled at three of these zoo parks during the study period. Seropositivity was detected in 28 (10.1 %) of 278 animals analyzed by blocking ELISA. Specific anti-SBV antibodies were confirmed in 20 (7.2 %; 95 %CI: 4.2-10.3) animals of six different species using virus neutralization test (VNT). The multiple logistic regression model showed that "order" (Artiodactyla) and "zoo provenance" (zoo B; southern Spain) were risk factors potentially associated with SBV exposure. Two (8.7 %) of the 31 longitudinally-sampled individuals showed specific antibodies against SBV at all samplings whereas seroconversion was detected in one mouflon (Ovis aries musimon) and one Asian elephant (Elephas maximus) in 2016 and 2019, respectively. To the best of the author's knowledge, this is the first surveillance conducted on SBV in zoos in Spain. The results confirm SBV exposure in zoo animals in this country and indicate circulation of the virus before the first Schmallenberg disease outbreak was reported in Spain. Surveillance in zoological parks could be a complementary approach to monitoring SBV activity. Further studies are warranted to assess the impact of this virus on the health status of susceptible zoo animals.

Evidence of exposure to zoonotic flaviviruses in zoo mammals in Spain and their potential role as sentinel species

A serosurvey was carried out to assess emerging flavivirus exposure in zoo mammals in Spain and to determine the dynamics of seropositivity in species that were longitudinally sampled during the study period. Sera from 570 zoo animals belonging to 120 mammal species were collected at ten zoos (A-J) in Spain between 2002 and 2019. Twenty-one of these animals, belonging to ten different species, were sampled longitudinally at four of the zoos during the study period. Antigenically-related flavivirus antibodies were detected in 19 (3.3 %; 95 %CI: 2.0-5.2) of the 570 animals analyzed using bELISA. Seropositivity was observed in ten (8.3 %) of the 120 species tested. Five (23.8 %) of the 21 animals sampled more than once presented seropositivity in all samplings whereas seroconversion was only observed in one white rhinoceros (Ceratotherium simum). Flavivirus antibodies were found at six of the ten sampled zoos and in consecutive years between 2008 and 2018. Virus neutralization tests confirmed West Nile virus (WNV), Usutu virus (USUV) and tick-borne encephalitis virus (TBEV) infection in ten (1.8 %; 95 %CI: 0.7-2.8), five (0.9 %; 95 %CI: 0.1-1.6) and one (0.2 %; 95 %CI: 0.0-0.5) animal, respectively. Antibodies against Meaban virus (0 %; 95 %CI: 0.0-0.7 %) were not found in the tested sera. The results demonstrate WNV, USUV and TBEV exposure in zoo mammals, which may be of public health and conservation concern. Seropositivity to WNV and USUV was detected in regions where these viruses have not been reported previously. Anti-WNV antibodies found in zoo animals sampled in 2009 point to WNV circulation at least one year before the first outbreaks were reported in horses and humans in Spain. Our results indicate that zoo mammals could be useful sentinel species for monitoring emerging flavivirus activity in urban areas.

Giant panda (Ailuropoda melanoleuca) sperm morphometry and function after repeated freezing and thawing

This work examines the effects of subsequent cycles of freezing-thawing on giant panda (Ailuropoda melanoleuca) sperm morphometry and function, and assesses whether density-gradient centrifugation (DGC) can increase the number of freezing-thawing cycles this sperm can withstand. A sperm sample was collected by electroejaculation from a mature giant panda and subjected to five freezing-thawing cycles. Although repeated freezing-thawing negatively affected (P < 0.05) sperm motility and membrane integrity, in both nonselected and DCG-selected sperm samples, >60% of the sperm cells in both treatments showed acrosome integrity even after the fifth freezing cycle. In fresh semen, the sperm head length was 4.7 μm, the head width 3.6 μm, area 14.3 μm(2) and perimeter length 14.1 μm. The present results suggest that giant panda sperm trends to be resistant to repeated freezing-thawing, even without DGC selection.

Heterologous murine and bovine IVF using bottlenose dolphin (Tursiops truncatus) spermatozoa

Assisted reproductive technologies are of great importance for increasing the genetic diversity in captive animals. The use of bovine or murine oocytes in heterologous IVF provides advantages compared to homologous IVF in nondomestic animals, such as the accessibility to oocytes and the availability of well-developed in vitro maturation systems. The aim of this study was to determine the heterologous IVF parameters using cryopreserved dolphin spermatozoa and zona-intact bovine or murine oocytes and to examine the nuclear chromatin status of the dolphin spermatozoa. All the processes involved in the fertilization including embryo cleavage were observed by confocal microscopy and hybrid embryo formation was confirmed by polymerase chain reaction. Heterologous bovine IVF showed no polyspermy, lower percentages of pronuclear formation, and a lower cleavage rate compared to homologous IVF group (34.8% vs. 89.3%). Heterologous murine IVF showed a lower cleavage rate than homologous IVF (9.6% vs. 77.1%). With respect to dolphin sperm chromatin, it was more stable, i.e. more resistant to EDTA-SDS decondensation than the bovine sperm chromatin. This study revealed the stability of the dolphin sperm chromatin and the ability of the dolphin spermatozoa to penetrate zona-intact bovine and murine oocytes, leading to hybrid embryo formation.

POST-THAW VIABILITY OF EUROPEAN BISON (BISON BONASUS) SEMEN FROZEN WITH EXTENDERS CONTAINING EGG YOLK OR LIPIDS OF PLANT ORIGIN AND EXAMINED WITH A HETEROLOGOUS IN VITRO FERTILIZATION ASSAY

Basic characteristics of European bison (Bison bonasus) semen were described and the efficacies of two extenders-Triladyl, containing egg yolk, and a synthetic extender, containing soybean lipids-were tested for semen cryopreservation. Seven ejaculates were collected by electroejaculation from a 10-yr-old, European bison bull. Each ejaculate was diluted at 37 degrees C to a final concentration of 200 x 10(6) sperm/ml with Triladyl or the synthetic extender. Extended semen samples were frozen according to a standard bull semen freezing protocol. After 2 wk of storage, one straw from each extender and ejaculate was thawed, and postthaw quality was evaluated by individual sperm motility and movement rate, numbers of sperm morphologic abnormalities and intact acrosomes, functional integrity of the sperm membranes determined by hypoosmotic swelling test (HOST), viability (live-dead, eosin-nigrosin stain), and a heterologous in vitro sperm penetration assay (SPA). A total of 600 in vitro-matured bovine oocytes were inseminated with 1 X 10(6) spermatozoa of Holstein semen frozen-thawed in Triladyl (control) or of European bison semen frozen in Triladyl or the synthetic extender. Nuclear status of the oocytes was determined after 18 h of sperm-oocyte coincubation. Extender had no effect on any evaluated parameters of semen after dilution and cooling (4 hr at 5 degrees C) or in postthaw individual motility, quality of movement, and sperm morphology. However, significantly (P < 0.05) higher numbers of spermatozoa with intact acrosomes, intact membranes (HOST), and viable sperm (P < 0.01) were in semen frozen in Triladyl than in the synthetic extender. Mean values for heterologous SPA for bull (control) and for bison semen frozen in the synthetic extender were very much alike-63.3+/-10.6% and 63.1 +/- 15.9%, respectively; bison semen frozen in Triladyl was lower, 43.0+/-24.2% but not significantly different. Cumulative results from a variety of viability assays of diluted/cooled and frozen-thawed semen, including the heterologous SPA, suggest that European bison semen can be successfully frozen in both extenders tested in this study.