Effect of sampling location, release technique and time after activation on the movement characteristics of scallop (Pecten maximus) sperm

Abstract

-Sperm characteristics of scallops have not been well described in the scientific literature. The effects of sperm release technique (thermal shock versus serotonin injection), of sperm collection technique (testis sampling versus serotonin injection), of sperm sampling location along the genital tract, of in vitro sperm maturation, and of time post activation on scallop sperm characteristics were assessed in the present work. Whatever sperm release technique used, no significant differences were observed regarding the percentage of motile spermatozoa and the velocity of the average path (VAP). Compared to testicular sperm, a higher percentage of motile spermatozoa, VAP and intracellular adenosine triphosphate (ATP) content were observed for sperm shed after serotonin injection. From the distal part of testes up to the gonopore, an increase of the percentage of motile spermatozoa and VAP was assessed, suggesting a sperm 'maturation process' along the genital ducts. A higher increase in the percentage of motile sperm was recorded during a 5 min incubation of testicular sperm in seawater containing 2 mM serotonin and seawater containing 10 mM caffein compared to seawater (control). In addition, a higher VAP was assessed, incubating testicular sperm in caffein, compared to control or serotonin. Then, the percentage of motile spermatozoa, VAP and intracellular ATP content exhibited a progressive reduction during the 10 h swimming period. Mean values of the percentage of motile spermatozoa, VAP, sperm track linearity (LIN) and intracellular ATP content recorded at the beginning of the movement period for sperm samples collected after intragonadal serotonin injection, were 82 ± 7%, 162 ± 15 µm s −1 , 0.33 ± 0.12 and 212 ± 133 nmol ×10 −9 spermatozoa (n = 9 males), respectively. The present study confirms the existence of a sperm "maturation process" along scallop genital ducts. In addition, the cessation of scallop sperm movement can be explained by the exhaustion of ATP content at the end of the movement phase.

CASA in invertebrates

“…CASA-Mot analysis of five species in two invertebrate phyla of so-called broadcast spawners show helical sperm tracks similar to those described by many investigators (Levitan 1993(Levitan , 1995(Levitan , 1998Au et al 2001;Farley 2002;Riffell and Zimmer 2007;Fitzpatrick et al 2010;Liu et al 2011;Suquet et al 2013;Fabbrocini et al 2016) or at least analysed by CASAMot or objective sperm motility analysis using alternative methods (Basti et al 2013;Lymbery et al 2016). There are few detailed descriptions of the nature of the patterns of these tracks, except for Liu et al (2011) and Vogel et al (1982), who referred to the helical tracks as 'Don Giovanni' and the forward moving tracks as 'Don Ottavio'.…”

“…Au et al 2001;Fitzpatrick et al 2010;Fabbrocini et al 2010Fabbrocini et al , 2016Basti et al 2013;Suquet et al 2013). Surprisingly, almost no detailed CASA research has been performed in other invertebrate phyla and accordingly our title falls short of expectations.…”

Cryopreservation of great scallop (Pecten maximus) sperm: effect of extender, cryoprotectant and cooling rate on sperm survival

“…In great scallop, it is not necessary to inhibit sperm movement before freezing because sperm movement has a long duration, lasting 8 to 10 h depending on males. This long movement duration is sustained by a gradual decrease of sperm intracellular ATP level during the movement phase: 19% of the initial ATP content is exhausted 1h post-activation and 40% after 3 h (Suquet et al 2013). The effect of extender composition has only been rarely studied in bivalves.…”

“…Sperm motility was estimated as previously described in Suquet et al (2013): briefly, the sperm was diluted (1:625 dilution rate) in SW (33.7 salinity, 20…”

“…Sperm is of the primitive type with an acrosome (Dorange and Le Pennec 1989). A sperm "maturation process" has been described along the scallop genital tract and the shedding of fully mature sperm was observed after intragonadal serotonin injection or thermal shock (Suquet et al 2013). Sperm activation in seawater triggers a high respiration rate and sperm movement which lasts for a few hours (Faure et al 1994a).…”