Don’t mistake the warty sea cucumber (Parastichopus parvimensis) with the one we peel, slice and add to a mixed green salad. The ocean variety is an animal named for its skin’s numerous black-tipped projections and cylindrical shape reminiscent of the familiar garden vegetable. Orange-brown to yellowish, a warty’s body is cushy, not crisp, and feels leathery due to its mass of muscle tissue. The cucumber is an echinoderm like sea stars and sea urchins but has several unique features lacking in its cousins. For one, it’s got a soft body. For another, the mouth and anus are located at separate ends of an elongated body. Speaking of the anus, it is also the only echinoderm with internal respiratory trees (lungs, if you wish), which are located just inside the anus. In other words, the warty breathes by drawing water in through the anus and then expelling it. The defining trait that identifies a cucumber as an echinoderm is its five-part symmetry: five rows of tube feet extend from the mouth along the body as is easily seen in, for example, a five-armed sea star.
Feeding is a round-the-clock affair for the sea cucumber. Mucus-covered tentacles, which surround the mouth, sweep across the surface; collected food bits are then transported into the mouth. A solitary critter, the warty is most abundant around cobbles, boulders and bedrock. I found a warty while tidepooling not long ago. After watching for a bit, I was rewarded by clear evidence that it was breathing. Recall that it draws water through the rectum to its respiratory tree, then forcefully expels the water. The internal water blasted into the surrounding water resulted in what appeared to be a water bubble that traveled to the water’s surface. As I continued to watch, every minute or so a bubble or three burbled up.
When threatened, the warty can contract its muscles and shoot out water from its body to make it shorter, thicker and harder, forcing predators to confront a much stiffer body. Other situations trigger a different response. The warty cucumber may expel sticky, toxic filaments to ensnare or confuse predators. In more heightened situations, the warty may expel all its internal organs through its anus. Such action isn’t life-ending because the cuke recovers by growing new innards. In fact, it can regenerate all parts of its body. Each fall, prior to reproduction, the warty finds a secure place to hide while its guts (including the sex organs, circulating system and respiratory tree) waste away. Within a month, the withered parts are regenerated.
Spawning usually takes place in November.The sexes are separate, and fertilization takes place externally, meaning that eggs of a female and sperm of a male are blasted into the water where, fingers crossed, they hook up. Successful fertilization generates free-swimming larvae, which float around for a few weeks before settling on the seafloor. Those that make it this far may live five to 10 years.
Cucumbers don’t have personality plus charming expressions or engage in playful antics, so why should we care about their survival? They aren’t called the “earthworms of the sea” for nothing. Acting as seafloor janitors, they ingest large amounts of sand, absorbing any organic matter for nutrition before returning the “polished” sand back to the seafloor. As such, they cultivate the seafloor in much the same way earthworms cultivate the soil. Sea cucumbers are also food to predators such as sea turtles, crustaceans and many fish, but humans are their greatest threat. There is an immense demand for sea cucumbers in Asian markets. Worldwide, many sea cucumber fisheries have collapsed from overharvesting. In areas where human activity has reduced the cuke population, the seafloor hardens, thus destroying the habitat for other bottom-dwelling creatures.
Overfishing of historically important species has led fishers to ply their trade down the food chain. In California, commercial fishers have been doing just that. The cucumber fishery has been developing off our coast for the past two decades. While the Department of Fish & Game requires fishers to purchase a permit, fishers are allowed an unlimited take. Past examination of Channel Islands’ warty cuke fishery showed large, significant declines in the cucumber population where they were harvested, compared to no-take reserves. Given that invertebrate fisheries like that for the warty sea cucumber are expanding, implementing the long-awaited Marine Life Protection Act cannot take place too soon.
— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to firstname.lastname@example.org.