“You know, those are actually animals!” a stranger told me as I tsk-tsked at what appeared to be Crayola-yellow shoestrings, rope, plastic or fishing line strewn along the sands of Boca Chica Beach one afternoon in early spring.
My error was a common one. Well-intended volunteers regularly dispose of tangled clumps of this creature—sea whip soft coral—along with soda cans, fishing line and plastic bags. Invertebrates like these are so vastly different from us—sans bilateral symmetry and lacking discernable eyes, nose and mouth— that we struggle to understand how they function and even appreciate them as fellow creatures.
Looking like a colorful, slightly branched bush, our local species (Leptogorgia virgulate), clings to rocks and shells in the shallows and estuaries of the Gulf, usually colored yellow, but also in reddish or purplish hues. Averaging eight inches in height, it can reach three feet. Like others in its family Gorgoniidae, the sea whip consists of a colony of polyps huddled together along a colorful supportive branch-like structure—consisting of spicules, or embedded lime— over what appears to be a wire skeleton. An adult sea whip is sessile, or immobile.
Though a beached sea whip is usually dead, with polyps retracted, immersing a recently beached one in water may animate its polyps. Translucent white and cylindrical— like tiny sea anemones—they pop out from their branches to feed upon floating plankton, their dual-purposed mouths surrounded by eight feathery tentacles, each bearing nematocysts, or stinging cells. Tentacles place food in their mouths, and enzymes break down food, with cells lining their cavities absorbing nutrients. Wastes then emerge from the same orifices.
Joining jellyfish, sea anemones and other corals in the phylum Cnidaria, the sea whip lacks a central nervous system, having, rather, a nerve net. It also bears statocysts, receptor organs which communicate the effects of gravity and ocelli— light-sensing organs bearing pigment and photoreceptor cells.
Unlike hard coral, sea whips reproduce sexually, their colonies being either entirely male or female. Influenced by water temperatures and lunar cycles, they release gametes, or sexual cells, into the water column, where they meet, growing into planulae, or free-swimming larvae. Attracted to light, planulae initially swim upwards into transporting currents. Undergoing several stages over from three to twenty days, they swim down towards a substrate, or surface—generally a rock or shell—then metamorphosize into polyps and form a colony.
Sea whips attract lots of company, some benign and others predacious, with the colony’s chemical defenses preventing some destructive barnacles, algae and bryozoans (moss animals) from attaching to it. The sea whip simnia, a tiny gastropod, or snail, feeds on polyps, absorbing the sea whip’s color. This video, by Jace Tunnell of the Harte Institute offers an excellent illustration of this snail and its consumption of the sea whip’s polyps:
