Cryopreservation of collared peccary (Pecari tajacu) semen using different freezing curves, straw sizes, and thawing rates

AbstractThe objective of this study was to verify the effect of different freezing curves, straw sizes, and thawing rates on the cryopreservation of collared peccary semen. Twelve ejaculates were obtained from captive adult males by electroejaculation, and evaluated for sperm motility, kinetic rating, viability, morphology, and functional membrane integrity. The ejaculates were diluted in a coconut water extender (ACP-116c) with egg yolk and glycerol, packaged into 0.25mL or 0.50mL plastic straws and cryopreserved in liquid nitrogen following a slow (−10°C/min) or a fast (−40°C/min) freezing curve. After one week, samples were thawed at 37°C/1min or 70°C/8s and evaluated as reported for fresh semen, and also for kinematic parameters (computerized analysis). A significant decrease in sperm motility and kinetic rating was observed after glycerol addition at 5°C and also after thawing for all the treatments (P<0.05). Regarding post-thaw semen variables, no differences were verified between freezing curves when the same straw size and thawing rate were taken as reference (P>0.05). In general, values for sperm characteristics found after thawing at 37°C were better preserved than at 70°C (P<0.05), both in the use of 0.25mL or 0.50mL straws, which were similar for semen packaging (P>0.05). The evaluation of the kinematic parameters of sperm motility confirmed these results at values varying from 20% to 30% motile sperm for the samples thawed at 37°C, and values fewer than 12% motile sperm for samples thawed at 70°C (P<0.05). In conclusion, we recommend the use of a fast freezing curve that reduces the time spent on the cryopreservation of collared peccary semen, which could be packaged both in 0.25mL or 0.50mL straws, but the thawing should be conducted at 37°C/1min

Do fragment size and edge effects predict carbon stocks in trees and lianas in tropical forests?

Summary Tropical forests are critical for protecting global biodiversity and carbon stores. While forest degradation and fragmentation cause negative impacts on trees, many woody lianas benefit, with associated negative effects on carbon storage. Here, we focus on the key question of how abiotic environmental changes resulting from tropical forest fragmentation mediate the allocation of carbon into trees and lianas. We focus on the globally threatened Brazilian Atlantic Forest, in forest fragments spanning 13–23 442 ha in area and at fragment edges and interiors. Within each fragment, we established two transects: one at the edge and one in the interior. Each transect consisted of ten 10 × 10 m plots spaced at 20 m intervals. Within each plot, we sampled living trees with diameter ≥4·8 cm at 1·3 m above ground, living lianas with diameter ≥1·6 cm at 10 cm above ground, and several microclimatic and soil variables. Fragmentation changed a broad suite of abiotic environmental conditions recognized as being associated with forest carbon stocks: edges and smaller fragments were hotter, windier, and less humid, with more fertile and less acid soils at edges. Tree carbon stocks were thus higher in forest interiors than at edges, and were positively related to fragment size in interiors, but were not impacted by fragment size at edges. Trees and lianas showed different responses to fragmentation: in interiors of small fragments, tree carbon stocks declined whereas liana carbon stocks increased; and at edges, tree carbon stocks were not affected by fragment size, whereas liana carbon stocks were highest in smaller fragments. These patterns were strongly related to changes in abiotic environmental conditions. We conclude that the abiotic changes across the fragmentation gradient, rather than liana proliferation, were more likely to reduce tree carbon stocks. Cutting of lianas is frequently promoted for restoring forest carbon in human-modified tropical forests. However, this approach may not be effective for restoring forest carbon stocks in fragmented forests