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Amazing Metazoan Archive
- The Amazing Metazoan for April 5 2013 is the greenling (genus Hexagrammos), a demersal fish commonly found throughout Sitka Sound. The Sound is home to three species of greenlings within the genus Hexagrammos, and one species of the genus Oxylebius. The rock greenling Hexagrammos lagocephalus is by far the most beautiful with its fiery orange, red, and deep brown markings and blue highlights. The Ahlgren Aquarium has two species of greenling in the tanks: the kelp greenling Hexagrammos decagrammus, and the white spotted greenling Hexagrammos stellatus. The kelp greenling in the photograph above is a male; females have gold mottling on a pale body and golden colored fins. Kelp greenling can grow up to two feet in length, and white spotted greenling attain roughly half that size. In both species, females lay the egg mass and males guard against predators. (Photo by Samantha Weaver)
BTY, the picture on facebook is a photo taken through a microscope of a scale from a white spotted greenling!
Is it a worm, a flower, or an invader from outer space? Click on the image to find out the identity of an animal that lives in the mud but gets its nutrients from the water.
This metazoan is a favorite among divers, and gets it namesake for its affinity for a certain type of habitat. Click on the photo to solve the clue and discover its identity.
- This entry’s Amazing Metazoan is our star attraction at the Molly Ahlgren Aquarium, the wolf eel (Anarrhichthys ocellatus). The wolf eel is not a true eel but a member of the wolf fish family Anarhichadidae, and unlike true eels such as morays, they possess pectoral fins and have flexible spines in their long dorsal fin. They also possess “canine” teeth as well as several rows of molars. Although they have a fearsome reputation for their ability to deliver a painful bite, they are in fact quite docile and have been the playful center of attention for hundreds of SCUBA divers. The aquarium’s wolf eel has been in residence since 2008, and was approximately 12 inches long when she was brought in by a fisherman. She now measures over 36 inches in length, and eats a variety of foods such as squid, salmon, and the occasional helmet crab. Click on the photo to see a short video of our wolf eel in her cave.
The Amazing Metazoan for January 14 2013 is a semi rigid animal that is fairly often seen in shallow subtidal areas. Notice the “bumps” in the photograph-the animal uses these structures for defense, cleaning, and respiratory purposes. Want to know what it is? Go to the Aquarium Gallery page and complete the jigsaw puzzle to find out!
For this week’s Amazing Metazoan, we are going to ask you to follow the clues to determine the identity of our featured aquarium animal. Let’s get started: What has scales, can live in diverse places such as the muck on the bottom of the ocean or as an epibiont on certain echinoderms, and is a close relative of an important terrestrial decomposer? Click on the photo and complete the jigsaw puzzle at the bottom of the page to find out!
Winter hasn’t even begun, but we bet that you are longing for those days of sunshine from summers past. Let us accommodate you with this photo of the gold dirona, Dirona pellucida, that was taken last summer during one of our collecting dives at the Eliason breakwater. The gold dirona, along with the similar looking white lined dirona and the not often seen Janolus fuscus, is an Arminid nudibranch. The leafy gold and white tipped appendages on this mollusc are the gills (called cerata). Gold dirona feed specifically on the bryozoan Bugula, which is an animal that resembles algae. This beautiful specimen was approximately 12 centimeters long.
The beautiful Aleutian Moonsnail Cryptonatica aleutica
It’s always a pleasure to see who’s roaming in our touch tanks at night; here we find the Aleutian moonsnail, which is easy to identify by its extensive mottled body. Contrary to what its name implies, this marine gastropod is found from Alaska all the way to southern California from the shallow intertidal down to depths of 400 meters (that’s over 1300 feet deep!). Cryptonatica aleutica was first described in 1919, but other species of Cryptonatica have been described as far back as the late 1700′s. One of Alaska’s most beautiful molluscs (in our opinion), the Aleutian moonsnail measures up to 6 centimeters, or 2.3 inches across.
Allow me to introduce you to the grainyhand hermit crab, Pagurus granosimanus. Although this anomuran crab may appear drab to the casual observer, closer inspection will reveal that it has a striking pattern of contrasting granules covering its walking legs and its “chelipeds” (the two front legs that hold the “chelae”, or pincers), as well as beautiful orange antennae (but not all grainyhands have orange antennae). Commonly found in tide pools and in the shallow intertidal zone, the grainyhand hermit crab prefers very large shells for its habitation. This particular touch tank resident is living in the shell of a deceased frilled dogwinkle.
Do you recognize this creature? This is a close up of the sunflower star, one of the largest (if not the largest) sea stars species found in Sitka Sound. Visitors to the aquarium often ask “why does the sunflower star look so soft and mossy?” If you look closely at the surface of the sunflower star with a magnifying lens, you will notice hundreds of fleshy projections called papula that give the animal its “soft and mossy” appearance. Scattered amongst the papula are numerous spines, which can be seen in this photo, and tiny jaw like structures called pedicillariae, which the animal uses for defense.
During a late morning excursion to collect live mealstock with the Molly O. Ahlgren Junior Curators, aquarium camp director Lynn Wilbur was under the Crescent Harbor dock shooting video when she noticed colonies of beautiful Vancouver feather duster worms (Eudistylia vancouveri). This species of polychaete worm is a member of the phylum Annelida, which it shares with earthworms. Feather duster worms build flexible, leathery sheaths through which they extend their feathery feeding appendages (known as radioles). When startled, a feather duster worm will retract its radioles, and the end of the tube folds over. Vancouver feather duster worms can be found under floats and walkways in at least two of Sitka’s harbors.
Look at what floated up at the aquarium! Chaya, our summer high school technician, discovered a winged nudibranch (Gastropteron pacificum) while cleaning one of the touch tanks. Contrary to what one may infer from its common name, this opistobranch mollusc is actually a member of the order Cephalaspidea.We believe that this individual recruited through our intake system that connects the touch tanks to the ocean, which provides a constant flow of nutrients for our critters. The winged nudibranch uses its wing-like appendages (called parapodial flaps) to seemingly fly through the water. When resting, the creature folds the flaps around itself, exposing the siphon that brings in oxygenated water. Chaya’s cephalispid is the size of a pinky fingernail, but winged nudibranchs can reach up to four centimeters in length.
Love in the touch tanks
The cloudy pinkish mass that you might see in our touch tanks isn’t some weird algal bloom-spring is here and our sea stars are spawning! Sea stars have separate sexes, and during spawning season the males and females release their eggs and sperm through their dermis into the water column. A sample taken from the bottom of our touch tank reveals thousands of eggs and sperm when viewed through a microscope. After fertilization, the sea star gametes undergo cell division and metamorphose into a planktonic stage, first becoming bipinnaria, then brachiolaria larva. As a member of the zooplankton community, they will beat their cilia and float with the ocean currents until they reach the juvenile stage, when they develop their arms (rays, which they will use for attaching to the substrate. Once on the bottom they will begin scavenging for food such as clams and worms, growing into the adult starfish that we are all familiar with.
Pinto abalone Haliotis kamtschatkana Also known as the northern abalone, this “coiled snail” is a much sought after member of the Haliotidae family, ranging from Japan, Siberia, Alaska, and as far south as Mexico. Attempts at opening a commercial fishery for this mollusc usually result in a severe decline in regulatory harvest size adults. Abalone have separate sexes and reproduce by releasing eggs and sperm into the water; males and females must be in close approximation in order for the gametes to make contact. After fertilization, abalone undergo a planktonic stage, feeding on phytoplankton in the water column. Once they reach their final developmental stage they will settle on rocks and in crevices to feed on microalgae; as they increase in size they will feed macroalgae (giant kelp).
Decorator crab Oregonia gracilis, named after the crustacean’s affinity for decorating its carapace with available pieces of algae, sponge, and other living material. The decorator crab starts out life as a member of the zooplankton community before maturing into its adult form. Like other species of decapods, decorator crabs “molt” (shed their exoskeleton) in order to grow larger. The individual in this photo recruited through our seawater intake system and underwent a series of molts to achieve a carapace size of approximately 4cm across. She now resides in one of our several display tanks.
Sea Leech Heptacyclus diminutus. “YUCK!”. That is what a visitor to the aquarium might say when closely viewing the sea leech Heptacyclus diminutus. This important member of the marine ecosystem is one of many marine leeches described in the fourth edition of the Light and Smith Manual, and is notable for its numerous light sensitive organs called ocelli. Heptacyclus diminutus attaches itself to rockfish by the oral sucker shown in the picture; we have also seen it attached to sculpins as well as an octopus. Sea leeches are introduced into the aquarium as stowaways on new residents or as hitchhikers through the intake system. Luckily for the squeamish, this leech spends most of its time attached to substrate by its caudal (tail) sucker. Heptacyclus diminutus is extremely photophobic as evidenced by its aversion to light when viewed under a microscope, and it disappears from the aquarium once spring progresses. The species name comes from the leeches’ diminutive stature; Heptacyclus diminutus achieves an average length of less than 1 cm and doesn’t seem to cause any harm to our fish.
Cookie star (Ceramaster patagonicus). This sea star gets its species name from the Straits of Magellen near Patagonia, where it was originally described aboard the research vessel Challenger. There are several species of cookie stars that range from South America to the Gulf of Alaska, as well as off the coast of South Africa. Ceramaster can be found at depths of 245 meters (800 feet). A similar sea star, the Arctic cookie star (Ceramaster arcticus), is also found in Alaska waters but is much smaller and more colorful. The cookie star feeds primarily on sponges, and is difficult to keep in an aquarium. March 15th, 2012
White Capped Limpet Acmaea mitra If you carefully explore the rocks and crevices in our subtidal touch tank you will likely encounter the white capped limpet Acmaea mitra. Although the common name for this nacellid gastropod may confuse some, the pink coloration comes from an encrusting red algae called Lithoamnia. When the animal dies, the algae wears off and beachcombers may find the snowy white shell of this mollusc all along the wrack line. March 1st, 2012
The white sea urchin (Strongylocentrotus pallidus) is an echinoderm that is seen infrequently in Sitka Sound, and can easily be confused with the white variety of the green sea urchin (Strongylocentrotus droebachiensis). S. pallidus has a somewhat squatter test than S. droebachiensis, its tube feet and tentacles are white to pale pink, and the spines are white. Sea urchins graze on algae, including giant kelp, with a five “toothed” aparatus, called the Aristotle’s lantern, located on the underside of the animal. Feb. 15th, 2012
