THE MATING SYSTEM OF THE SQUID LOLIGO VULGARIS REYNAUDII (CEPHALOPODA, MOLLUSCA) OFF SOUTH AFRICA: FIGHTING, GUARDING, SNEAKING, MATING AND EGG LAYING BEHAVIOR

摘要

The chokka squid migrates to coastal waters to spawn, and its behavior on shallow spawning aggregations was analyzed by video sequences taken during SCUBA diving. Most squids were paired (M/F) on the spawning sites, yet mate pairing duration was brief. Near to egg masses, a few lone large males were always present and would fight consort males to obtain access to paired females. Paired 'consort' males won 16 agonistic contests while unpaired 'intruder' males won 9; thus there was a considerable turnover rate for consortships. The larger male won in 14 of the 25 contests. Fighting involved mainly visual signalling but escalated to moderate physical contact (Fin beating) but not injury. Both sexes had multiple mates even within several hours. Two methods of mating were observed, each with different placement of spermatophores, and a third method possibly exists. Large paired males mated in the 'male-parallel' position and inserted spermatophores near the oviduct; egg laying usually occurred shortly thereafter. Small sneaker males were often successful in mating a paired female; they copulated in a modified 'head-head' position in which they attempted to place spermatophores amidst the female's arms. Remarkably, sneakers seemed to recognize when females were holding an egg capsule and then timed their copulation attempt at that time. Sneakers did not engage large male consorts in contests, and consorts seldom chased them away when they mated a female. The 'cuckolded' consorts did not attempt to mate females again before they laid the egg capsule. Males guarded females as they descended periodically to lay individual egg capsules. All of these features indicate a high level of sperm competition. There were no lone females on spawning sites, and all arrived there with stored sperm in the seminal receptacle, having presumably mated in the typical 'head-head' position previously. Females rarely rejected males (consorts or sneakers) and it is possible that they exerted some choice of male sperm. There was no form of parental care of the eggs or paralarvae. Reproductive tactics are discussed in relation to the life cycle of this valuable fishery species.