Essays on Invertebrate Conservation
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WINGS ESSAYS ON INVERTEBRATE CONSERVATION THE XERCES SOCIETY SPRING 2010 CONTENTS Sea Anemones: Flowers of the Sea Susan J. Tweit Generally hidden from our view except at low tide, anemones lead surprisingly complex lives. Page 3. Butterfly Monitoring: On Being in the Right Place at the Right Time Arthur M. Shapiro A wealth of information collected over nearly four decades of dedicated field re- search is beginning to reveal startling changes in the lives of California butterflies, including declines in some formerly common species. Page 8. The Beautiful Katydids Piotr Naskrecki Katydids may be best known for the singing we hear during summer evenings, but they are a diverse group of insects with widely differing diets and lifestyles. And not all of them sing. Page 14. Appropriate Forest Management In the Face of a Bark Beetle Epidemic Scott Hoffman Black Although dead and dying forests are turning the mountain landscapes of western North America brown, we need to carefully think through our practices for deal- ing with the effects of an epidemic bark beetle infestation. Page 20. The Great Sunflower Project Gretchen LeBuhn Across North America, ordinary people are tracking the visits that bees make to sunflowers growing in their yards and gardens, thereby adding to our scientific understanding of the health of pollinator populations. Page 25. Xerces News A report on bark beetles; pollinator conservation strategy for Yolo County; new resources on our website; an expanded guide to freshwater mussels; protecting bumble bees and a stonefly; and the 2010 DeWind Award winners. Page 29. 2 WINGS Sea Anemones: Flowers of the Sea Susan J. Tweit If there is poetry in my book about the sea, ing up on my journaling while my stu- it is not because I deliberately put it there, dents, a group of creative writers from but because no one could write truthfully around the United States, were taking about the sea and leave out the poetry. a break to snorkel. Part of my attention — Rachel Carson, was on the wet-suited and swim-finned accepting the National Book Award bodies rocking in the swells around the for The Sea Around Us, 1952 buoy where the panga was moored, and part was on my writing, when Raoul, I was perched on the bench seat of a our boatman, exclaimed, “Mira, Susan! panga, a deep-sided fisherman’s skiff Flores del mar!” and pointed over the with a powerful outboard engine — a gunwales. vessel of the sort that is common trans- I looked over the side into the clear portation on the Sea of Cortez — catch- azure water. A school of hundreds of Anemones are carnivorous animals, closely related to corals and jellies. They get their color from algae that live within their bodies. Green anemone (genus Anthopleura), photographed by Bill Bouton. SPRING 2010 Rocky shores offer habitat for anemones and other marine life, and, at low tide, provide opportunities for people to observe these otherwise hidden creatures. Photograph by Kathy Hall. colorful fish flickered past and suddenly “Son gigantes!” I said. “How big do circled, producing a swirl of sparkling you think they are?” air bubbles. Then I saw what Raoul was Raoul held his hands out in a circle pointing at. Among the rocks protrud- about the size of a dinner plate. ing from the white sand bottom clearly “Wow,” I replied. As we watched, the visible perhaps twenty feet below was center anemone in the cluster burped. a cluster of sea anemones, or flores del Its flower-like central disk convulsed, mar, “flowers of the sea.” No ordinary the center drawing in as if to swallow sea anemones, however. They were itself, and the fringe of tentacles disap- huge, with flat central disks as big as pearing into its mouth. A moment later, my face, and colored bright greenish- a white fragment of something flew out, blue, with rows of petal-like tentacles the tentacles reappeared, and the disk that looked the size of my fingers. On rearranged itself back into a placid un- their fat stalks they swayed ever so gen- derwater blossom. tly with the swells, mimicking the mo- Sea anemones get their name from tion of the panga overhead. that deceptively lovely, flower-like ap- WINGS pearance. But the name of their phy- ach, and any inedible shell or bones are lum, Cnidaria — literally, “nettle-like heaved back out of the mouth slit with creatures”— is a better clue to their a very human burping motion. character. These anemones are no meek Most anemones cluster in colonies garden flowers. In fact, they’re not even of dozens or hundreds, but the flores plants at all; they are carnivorous ani- del mar that Raoul pointed out were mals, closely related to jellies and cor- not numerous enough to call a colony als. In the adult stage of their lives, sea — just three huge specimens with thick, anemones are sedentary, or nearly so, bumpy-skinned stalks. They were al- attached to the ocean bottom or to most certainly giant green anemones, some solid object underwater by the which are among the world’s largest, suction-cup-like disk at the bottom of found from Alaska to Panama attached the fleshy cylinder that comprises most to rocky substrates in locations ranging of the body. from nearshore tidepools to waters fifty The top of a sea anemone’s column feet deep. is what appears flower-like: the flat oral Giant green anemones are often disk with a slit-shaped mouth at its solitary creatures, but, in the vicin- center, surrounded by several rows of ity of such dense aggregations of food those petal-like tentacles. The gently as mussel and sea urchin beds, these waving “petals” are actually potent huge anemones may crowd together to armaments. Each tentacle is tipped by benefit from the foraging of predatory a nematocyst, a capsule that explodes sea stars, commonly called starfish. A on contact, expelling a sticky, thread- sea star strolling into an urchin bed, like dart studded with venomous barbs for instance, provokes an underwater that embed themselves in the flesh of stampede; as the spiny creatures try whatever touches them. The barbs carry to escape their many-armed predator, a neurotoxin powerful enough to stun some invariably rush directly into an- or kill small animals such as crabs, fish, other peril: the tentacles of giant green sea urchins, and shellfish. They’re not anemones. Also, sea stars are messy eat- generally large enough to pierce human ers, dropping chunks of meat and shell skin; still, the poison may cause a tin- that anemones can snag. gling or sticky sensation. Giant green anemones get their Sea anemones “hunt” by sitting startling coloration from other inver- patiently, their seemingly innocuous tebrates that live in their tissues. When tentacles open wide. When a smaller these anemones live where there is suf- creature such as a sea urchin careless- ficient sunlight, minute algae — either ly walks across the anemone or a fish bright green unicellular zoochlorellae brushes the tentacles, the nematocysts or yellow-brown dinoflagellates called release their stinging barbs, stunning zooxanthellae — take up residence in the prey. Like a flower closing with the the anemones’ digestive tracts. Both night, the tentacles quickly fold inward, types of algae make chlorophyll and bearing the food to the anemone’s synthesize their own food from sun- mouth. Once inside, the meaty parts are light. Some of the food they produce digested in the animal’s bag-like stom- leaks through their cell walls and into SPRING 2010 Despite the variety in color, these sea stars belong to a single species, the ochre sea star (Pisaster ochraceus). Sea stars are messy eaters, dropping chunks of food that can nourish nearby anemones. Photograph by Kawika Chetron. their hosts, akin to what happens with produced by the tiny algae is crucial — lichens, where a food-producing alga without it, they die. Coral “bleaching,” feeds the fungus within whose tissues the loss of color and subsequent death it resides. of coral in ocean reefs, happens when What is not clear is whether the the sugar-making zooxanthellae are anemone-algae relationship is similar killed by overly warm ocean water, as to that of the fungus and algae that is happening as a consequence of global make up lichens, where the non-pho- climate change. tosynthesizing fungus, which cannot Despite their stinging tentacles, sea survive on its own, essentially captures anemones are vulnerable to predators. and enslaves free-living, photosynthe- Some nudibranchs — brightly colored sizing algae as a food source. Like the mollusks often called seaslugs — graze species of algae in lichens, the algae of the tips of the tentacles and then ingest sea anemones can and do survive on the nematocysts, which lodge, in per- their own, but giant green anemones fect working order, at the ends of the apparently also can exist without their nudibranchs’ tubercles, soft “spines” algal partners, although then they grow protruding from their backs. The nu- more slowly than they otherwise would. dibranchs then use the nematocysts in Zooxanthellae have a similar relation- their own defense. ship with coral, except that, for these Other predators simply crawl or reef-forming ocean creatures, the food saunter up to an anemone’s succulent WINGS column and begin to feed. Wentletrap but animal, blooming on the threshold snails — small snails with long-spiraled of the deeper sea.” Strange flowers in- shells — secrete a violet-colored toxin deed: they live underwater, sting with that acts as an anesthetic, numbing their petals, house algae within their the tissues before they begin chewing. tissues, and eat meat.