ore than an Axon This article first appeared in the Fall 1995 issue of LabNotes, an MBL publication.

Sure, they show up every April, but what are they actually doing out there in the Sound? It's one of the delicious ironies of seaside science that squid nerve cells are among the most thoroughly studied cells on earth, while the beautiful little animal itself is something of a mystery. There's an old joke, in fact, that biologists tend to view squid as a support system for axons. It is not quite true that nothing is known of Loligo, the local squid with the giant axons so favored by biologists, said Dr. Roger Hanlon shortly after he assumed directorship of the Marine Resources Center in September. Hanlon, who has raised other species of squid in a lab at the University of Texas, Galveston, said some questions about Loligo have been answered in recent years. "It only lives a year, on average - that's been shown beyond a question in the last year," Hanlon said. Past estimates have pegged squid's life span at anywhere from one to four years. The correct figure - one year - was established by studies of the animal's statocyst, a calcium carbonate rock in the animal's balance organ that grows in rings that are laid down daily, Hanlon said. And of course fishermen have known for decades that the animal is a migratory creature that comes to Cape waters every spring to spawn. "They overwinter in the deep water where the temperature is more stable," Hanlon said. A mobile predator that can travel five to ten miles per night, Loligo migrates to inshore waters in April, "when everything is blooming," Hanlon said. The hatchlings live off yolk for four to five days, and then begin preying, probably on copepods at first and then later on larval fishes and shrimp. "They also eat other squids at some point in their life cycle," Hanlon said. "Some portions of their migration back out is fueled by cannibalism." The question of how they reproduce is quite complicated - and still poorly understood, Hanlon said. The females are promiscuous (not a pejorative term, but simply the biological term for mating with multiple partners). "There's a lot of competition," Hanlon said. "Every female has at least two and probably three or more sources of sperm. The female arrives (in local waters) with sperm already stored in a pouch just under her mouth." The female gathered that sperm in an off-shore mating, in a head to head position. When she arrives inshore, the female pulls a jelly-like matrix of eggs out of her body and holds it her arms and releases the stored sperm to fertilize hundreds of eggs.

"But they don't just come here and release sperm and eggs," Hanlon said. "The males are fighting for temporary access to the females." During spawning in local waters, the successful male takes a position alongside the female, grasps her from underneath, and deposits sperm on the side of her mantel near her oviducts. When the female extrudes her eggs, some are fertilized by this sperm from the most recent male, while some are fertilized by the older sperm stored in the pouch. Loligo society, Hanlon suspects, also includes "sneaker males" - smaller males who do not compete successfully in fighting but nonetheless find a way to mate with females. While big males are busy fighting for access to females, a sneaker male zooms in and quickly mates the female from the top, releasing sperm directly to the eggs she holds in her arm. Sneaker males are known to exist in animals other than squid and have been documented on video of African squid, but are still a hypothetical part of the Loligo sex scene. 1997 Note: Sneaker males have now been documented in L. pealei. See the development section of the Loligo site or the recent Biological Bulletin article by Roger Hanlon with online video clips of this behavior. Hanlon hopes to answer the question of whether there are sneaker males next spring in a study that would involve diving. He is also planning to study squid paternity in the lab by doing a DNA analysis of fertilized eggs to see if some strands contain genes from three or more males. The answers, beyond shedding light on interesting reproductive strategies, may provide some guidance for biologists charged with fisheries management. For the last decade and a half, squid fishermen have taken an enormous number of animals out of local waters, as anyone who has taken a casual glance at the Vineyard Sound in mid-May knows. (The MBL squidders who fish for science, by the way, account for less than five percent of the season's catch and make less than a dent in squid populations). Although squid stocks have held up, there has been concern for years that the squid fisheries may collapse, as other fisheries have. Given the current ignorance about squid reproductive behaviors, those fears are reasonable, Hanlon said. If, for instance, fishermen remove too many of the big males, the proportion of sneaker males might increase. And if sneaker males are not just younger but smaller and less successful by way of genetics, then fishing out the big males could decrease the size of future generations. Whether or not there are sneaker males (Hanlon thinks there are), and whether or not they are genetically different (Hanlon suspects they are not), learning about the gene flow should help fisheries biologists make better management decisions. "They've been making decisions with no knowledge of the mating system," Hanlon said. "Fishing reproductively active animals is what ruined other fisheries. How careful do you have to be with squid?" Hanlon asked. "I don't know, but let's get some biology into the decision."