Reproductive Strategies: -The zebra mussel undergoes an annual cycle of gonadal growth and gamete maturation, culminating in one or more spawning events in late spring or early summer. -Spawning is to deposit eggs. - Variables that determine reproductive responses: -Temperature -Rates of temperature change -Food availability -Effects of neighboring mussels -Serotonin is a biogenic amine which is implicated in spawning behavior and can reliably trigger spawning. -Prior to spawning, serotonin reinitiates meiosis causing maturation from prophase I to metaphase I in females.