Is it possible to store spotted wolffish (Anarhichas minor) sperm by refrigeration?

Abstract

Spotted wolffish Anarhichas minor reproduction in captivity is dependent on in vitro fertilization. However, it is often challenging to acquire sufficient fresh sperm to fertilize the eggs that are obtained. In this study, we evaluate the possibility to store spotted wolffish sperm by refrigeration. Spotted wolffish sperm has the particularity that is already motile on stripping, and currently it is not possible to immobilize and reactivate. Thus, sperm refrigeration protocols should focus in extending this motility period that usually lasts up to 2 days. In a first experiment, we evaluated the possibility that the motility period of the sperm was limited by contamination with urine. The urea concentration in the sperm obtained both by stripping (17.10 ± 1.98 mg/dL) and directly from the testis (12.59 ± 2.37 mg/dL) was similar (p > 0.05), which indicate that the sperm collection method used avoid contamination with urine. Afterwards, we tested the possibility that the sperm motility period was limited by energy stores. The ATP concentration (initial value 5.65 ± 0.86 nmol/10 9 cells) remained stable (p = 0.099) during 30 h after sperm collection, and similar values (p = 0.329) were recorded at end of sperm storage in both diluted (3.88 ± 1.35 nmol/10 9 cells) and undiluted samples (4.76 ± 1.08 nmol/10 9 ). This indicates that the low intracellular ATP consumption, derived from the slow sperm motility, can probably be compensated rapidly enough by mitochondrial synthesis of ATP in the spotted wolffish sperm. In both experiments, diluted sperm kept higher percentage of motile cells during the storage time.

The status of spotted wolffish, Anarhichas minor: A commercially ready species for U.S. marine aquaculture?

“…Good post-thawing motility scores were achieved using reliable cryopreservation techniques by Le François et al (2008) 2020) achieved variable but repeatable results. Short-term refrigeration storage of spotted wolffish sperm also was evaluated (Gonzalez-Lopez et al, 2020). Hormonal induction of spotted wolffish spermatogenesis initially was studied by Kugathaj (2005) whereby the effect of 11-KT on sperm production was assessed in order to elevate the blood plasma level of 11-KT in males.…”

Spotted Wolffish Broodstock Management and Egg Production: Retrospective, Current Status, and Research Priorities

“…Sperm density is within the range of 10 9 cells per mL [25,26] and is almost clear in appearance. Meanwhile, sperm concentration has been primarily evaluated using a haemocytometer [25,26,106], and other approaches such as spermatocrit or spectrophotometry have also been tested [26]. In the Atlantic wolffish, the spermatocrit value was lower when males were kept at 8 or 12 • C several months prior to the spawning season compared to 4 • C [87].…”

“…This method provides an initial assessment of the motility and is often used in fertilization trials [110]. Nonetheless, the use of computer-assisted sperm analysis systems (CASA) provides a more objective evaluation and has also been employed in spotted wolffish sperm quality studies [25,102,106,111]. The CASA systems, besides the percentage motility, measure different sperm swimming velocity parameters, such as curvilinear velocity (VCL) or straight-line velocity (VSL), parameters associated with the trajectory such as linearity (LIN), and other parameters such as wobble of the sperm head; for a detailed description, see [112].…”

“…The high number of mitochondria is typical of fish with internal fertilization which allows the sperm to stay motile for a prolonged period. Regarding the seminal plasma, the pH varies between 6.3-6.7 with osmolality values between 310-330 mOsm [28,106], but none of these seminal plasma parameters seem to be related to the sperm motility [106].…”

“…It is often difficult to find spermiating males and with enough sperm volume at the end of the spawning season [1], and this represents a challenge to fertilize the last egg batches. Consequently, the development of sperm storage techniques has been extensively researched [25,102,105,106,109,111]. Cryobanking of the sperm of genotyped broodstock populations is justified in order to control undesirable inbreeding levels.…”