Abstract
BackgroundSemen from the chimpanzee species becomes a colloidal solid after ejaculation. The formation of this copulatory plug is believed to prevent additional spermatozoa of subsequent mating events from accessing the ova. However, this naturally preserved strategy hampers the processes for sperm preparation. In this study, we investigated whether collagenase can be used to degelify the semen plug and accelerate the semen liquefaction process in zoo captive chimpanzee species (Pan troglodytes).ResultsWe showed that incubation of chimpanzee ejaculates with 0.1% type I collagenase efficiently and significantly (p < 0.05) releases 2.7-fold more spermatozoa from the coagulated ejaculates, and this degelification process did not alter sperm morphology or viability; nor did it stimulate spontaneous capacitation or an acrosome reaction as assessed by tyrosine phosphorylation and peanut agglutinin stains; moreover, based on computer assisted sperm analysis assay, motility-related parameters remained similar to those of untreated spermatozoa. When collagenase effects were evaluated on cryopreserved sperm samples, we observed post collagenase treatment in which 2.5% glycerol, as a cryoprotectant, preserved sperm acrosome integrity better than 7.8%; however, 7.8% glycerol, as a cryoprotectant, maintained sperm motility better than that of 2.5% glycerol.ConclusionsOur results demonstrated for the first time that type I collagenase can be used to obtain a significantly higher number of spermatozoa from colloid chimpanzee semen ejaculate without affecting the physiological properties of spermatozoa, and these results are critical for the subsequent gamete development. Our results would benefit sperm preparation processes and cryopreservation efficiency per ejaculate, as more unaffected spermatozoa can be released from the semen plug within a shorter period of time. These results would also benefit the genetic diversity of the chimpanzee species, using sperm cells from less dominant individuals, and for achieving better pregnancy success in primates with significantly higher amounts of sperm for artificial insemination.
Highlights
Semen from the chimpanzee species becomes a colloidal solid after ejaculation
Type I collagenase facilitated the release of spermatozoa from colloid semen without affecting sperm morphology and viability In line with observations from earlier studies [10, 22], ejaculations from chimpanzees formed a colloid semen texture as soon as they were exposed to the air, and only a minimal amount of semen in liquid form could be observed (Fig. 1a)
Motility-related sperm parameters were not altered by type I collagenase treatment Sperm motility is the most important factor for successful fertilization in vivo; we evaluated the effects of type I collagenase on sperm motility using a wellrecognized system, namely, computer-assisted sperm analysis (CASA)
Summary
Semen from the chimpanzee species becomes a colloidal solid after ejaculation The formation of this copulatory plug is believed to prevent additional spermatozoa of subsequent mating events from accessing the ova. Yu et al BMC Veterinary Research (2018) 14:58 orangutan, gorilla), the ejaculates begin to coagulate and become a colloidal solid after exposure to the air [6, 7] The formation of this so called “mating plug” or copulatory plug is believed to prevent the additional spermatozoa of subsequent mating events from accessing the ova, which is critical to preserve genetic materials from a specific individual (especially the dominant individual from a species with highly hierarchical social structure) in wild animals [8]. We aim to investigate whether type I collagenase would facilitate semen liquefaction of chimpanzee semen and to evaluate whether collagenase treatment would affect sperm capacitation status, acrosome integrity and motilityrelated parameters using various independent approaches
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