Energy pathways associated with sustained spermatozoon motility in the endangered Siberian sturgeon Acipenser baerii

Abstract

Sturgeon spermatozoa are unique for their sustained motility. We investigated the relative importance of bioenergetic pathways in the energy supply of Siberian sturgeon Acipenser baerii spermatozoa during motile and immotile states. Spermatozoon motility and oxygen consumption rate (OCR) were analysed following exposure to inhibitors of oxidative phosphorylation (sodium azide, NaN 3), glycolysis (2-deoxy-Dglucose, DOG) and β-oxidation of fatty acids (sodium fluoride, NaF), and to an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenyl hydrazine, CCCP). No significant difference in curvilinear velocity was observed after addition of these reagents to activation medium (AM) or nonactivation medium (NAM) for incubation. Incubation of spermatozoa in NAM containing CCCP or NaN 3 resulted in significantly decreased motility duration compared to controls. The OCR of sturgeon spermatozoa in AM (11.9 ± 1.4 nmol O 2 min −1 (10 9 spz) −1) was significantly higher than in NAM (8.2 ± 1.5 nmol O 2 min −1 (10 9 spz) −1). The OCR significantly declined with addition of NaN 3 to AM and NAM. No significant difference in motility parameters or OCR was observed with NaF or DOG. These results suggest active oxidative phosphorylation in both immotile and motile spermatozoa. Nevertheless, mitochondrial respiration occurring during motility is not sufficient to meet the high energy demands, and the energy required for sustained motility of Siberian sturgeon spermatozoa is derived from adenosine triphosphate accumulated during the quiescent state.

Changes in Phenotypes and DNA Methylation of In Vitro Aging Sperm in Common Carp Cyprinus carpio

“…A previous study conducted on Indian major carp orangefin labeo ( Labeo calbasu ) have also observed a similar significant decrease in sperm motility during the first 12 h of storage [ 37 ]. The energy source [adenosine triphosphate (ATP) is the most common] produced and stored during the quiescent stage of spermatozoa in seminal plasma has been implicated as the primary source of immediate energy needed for spermatozoa motility [ 38 , 39 ]. Reduction in sperm motility is assumed to be a result of a decrease in ATP and oxygen during the storage time [ 40 ].…”

Bioenergetic Pathways in the Sperm of an Under-Ice Spawning Fish, Burbot (Lota lota): The Role of Mitochondrial Respiration in a Varying Thermal Environment

“…Recently, to measure the OCRs in biological samples, several novel methodologies have been devised, among which are the MitoXpress fluorescent assay [ 52 ], electron paramagnetic resonance oximetry [ 53 ], the Seahorse metabolic assay [ 54 ], the scanning electrochemical microscopy method [ 55 ], and the respiratory detection system [ 56 ]. Nevertheless, most mitochondrial respiration studies in fish spermatozoa, including this one, were performed using the conventional Clark-type polarographic method [ 10 , 31 , 35 , 36 , 57 ].…”

“…This observation is supported by the majority of the data for the trout [ 11 , 57 , 59 ]. In contrast, the trend of an enhanced OCR after motility activation is common in temperate, warm-water, or marine species such as the carp, African catfish, Siberian sturgeon ( Acipenser baerii ), and turbot [ 9 , 10 , 31 , 36 ]. To the best of our knowledge, the burbot in the presented study and the trout mentioned above are the only cold-water species in which spermatozoon metabolic pathways have been studied by means of the OCR.…”

“…The results are similar to the data for the trout at 10 °C [ 11 , 57 ]. While warm-water species such as the carp, sturgeon, and turbot spawn at 15–20 °C, enhanced OCRs after uncoupling in a non-active state have been observed [ 9 , 10 , 31 ]. The results suggest a homologous pattern for an uncoupling effect in the spermatozoa of cold-water (no enhanced capacity) and warm-water fish (enhanced capacity).…”

“…In various externally fertilizing fish, such as the cold-water trout ( Oncorhynchus mykiss ) and the warm-water carp ( Cyprinus carpio ) and turbot ( Psetta maxima ), studies have evaluated the enhancements in respiration during active and inactive states [ 8 ]. It has been revealed that the spermatozoa of some fish enhance oxidative metabolism after motility activation or after being exposed to an uncoupling agent [ 8 , 9 , 10 ]. Despite this documented knowledge, no prediction has yet been made for the enhanced respiration in a particular fish species based on its thermal habitat or taxon.…”