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

¹ Ifremer, UMR 6539, Physiologie fonctionnelle des organismes marins, Station expérimentale d’Argenton, Argenton, France
² Ifremer, UMR 6539, Physiologie fonctionnelle des organismes marins, Plouzané, France
³ University of South Bohemia in Ceske Budejovice, Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, 38925 Vodnany, Czech Republic

^a Corresponding author: marc.suquet@ifremer.fr

Received: 26 October 2012
Accepted: 15 March 2013

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 ± 15μm 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.