Part 4 of our “Smorgasbord of Food Offerings from the Sea” series
by Janice Edwards
To conclude our series on Smorgasbord of Food Offerings from the Sea, we thought we would offer up some nice flowers to gaze at while you eat your grilled sea pork, sauteed sea apples, and some warm sea biscuits. Therefore, this post is on the organism known as the sea pansy, Renilla reniformis.
Sea pansies are fleshy and have a petal shape reminiscent of a...pansy. They are a type of soft coral classified in the order Pennatulacea, and are actually colonies of small polyps working together cooperatively to benefit the organism as a whole. The petal-shaped body, which can be up to 2 inches in diameter, is connected to a stalk known as a peduncle. It is this primary polyp, the peduncle, that anchors the sea pansies to the the ocean floor by thrusting itself into the sand or mud.
Living and Working Together Cooperatively Fact #2: On the upper side of the pansy are two types of secondary polyps. One type is a feeding polyp which secretes gooey mucus to trap zooplankton and organic matter floating nearby. From there the food is sent to a common digestive system for the whole colony to partake. The other type of secondary polyp can be found between the feeding polyps. They are like little water pumps and are responsible for inflating or deflating the entire colony. Very handy if the organism is trapped on a sandbar during low tide and needs to hide from predators!
Living and Working Together Cooperatively Fact #3: Sea pansies have an interesting way to ward off predators that also involves cooperative action. At night, if a predator approaches or touches it, the colony distracts it by sending out pulsating waves of bioluminescent greenish light. Can you say--shades of Jedi lightsabers? A green fluorescent protein along with an enzyme creates this light show. The enzyme is known as luciferase from the Latin word Lucifer meaning light bearer.
By Laura Lukas
Is it possible for any one person to know every species on Earth? The answer is a resounding no, for many reasons. My alma mater required students to take only 1/3 of the biology courses offered to science majors, so it's no surprise I struggle to keep my (many phyla of) worms straight from each other and worms from clam worms (which are annelids), clams, clam shrimp, and shrimp. [Somewhat sarcastically speaking of course!] Would the other 2/3 of courses have prepared me for what I see at the museum?
Working behind the scenes in the museum's ichthyology collection I am exposed to various treasures. Recently I've been finding invertebrate symbionts attached to fish hosts. One invertebrate with a particularly interesting life history is the tongue eating isopod; it literally looks like a tongue until you take a second look and see a bug like creature. This crustacean eats the tongue of a fish, and leaving a host with a life-long companion whether it wants it or not.
Other fish symbionts appear to be slightly less invasive. While looking over a sunfish, I noticed an object attached to the fish near the tail region. It seemed out of place and I dismissed it for an ID tag we sometimes attach to fish. Upon closer examination, I realized it was a parasite. The parasite looked very strange, so my colleagues and I were determined to ID it. We came to the conclusion that the parasite was an anchor worm. Rather than falling into the "true worm" phylum – rather many worm phyla – the anchor worm is the reproductive female form of a copepod, which is a crustacean!
A few weeks later I noticed another "worm" attached to a different fish, this time a marine species. Interestingly, the two copepods were found at different salinities, and showed obvious morphological differences. The freshwater copepod was more of a soft Y; the saltwater copepod was stiff and more cylindrical.
I was given the opportunity to remove the "worm" from its saltwater host. Using my expert surgery skills, I dug into the fish until finding the anchor portion. The anchor structure of the copepod was buried under the skin of fish at almost 1.5 times the length of the exposed body.
It seems there is no shortage in finding new (to me) species at work. These animals have evolved such curious lifestyles. It just goes to show how unique life is, and begs the question as to why these anchor worms began attaching themselves to fish in the first place. Food and transportation all in one package? Pretty tempting, if I do say so myself.
Part 3 of our “Smorgasbord of Food Offerings from the Sea” series
By Janice Edwards
If you have been following the previous posts in this series, you know we have had sea pork and sea apples as part of our Smorgasbord of Food Offerings from the Sea series. To round out our menu, we have the sea urchin Clypeaster roseaceus commonly known as a sea biscuit. Sea biscuits can be found in shallow tropical and temperate waters.
What’s In a Name Question #1 or Why Do They Call It That: The genus name, Clypeaster, is Latin for the outward appearance of these animals --”clypeus” means round shield and “aster” means star. How interesting that a marine animal sports the shape of a flower on its body!
The genus Clypeaster is in the phylum Echinodermata which, in addition to sea urchins, also includes starfish, sea lilies, and sea cucumbers. Sea biscuits tend to be more oblong and rounded than their cousins, the sand dollar. Both sea biscuits and sand dollars have a mouth midway on their underside and anus at the end, and as such are called irregular urchins.
What’s in a Name Question#2 or Regular vs. Irregular: Regular echinoids, or sea urchins, have no front or back end and can move in any direction. (Picture a spiny sea urchin in your mind.) Their longer, often painful-to-predators spines help protect them as they move around. Irregular echinoids have a definite front and back and move in a particular direction, often burrowing in sediment. Irregular urchins are considered to have evolved from an ancestral regular urchin form. Thus, anatomical characteristics exhibited by irregular urchins are thought to represent modifications to the anatomy of regular forms. Most echinoderms exhibit bilateral symmetry as larvae, meaning they can be divided into matching halves by drawing a line down the center. During development, echinoderms become five-fold (i.e., pentamerous) symmetrical, meaning they can be split into five similar segments around a central axis (center of the body). Irregular urchins exhibit secondary bilateral symmetry; as adults these organisms display bilateral symmetry, but in a manner unlike that they possessed as larvae.
Because sea biscuits have a different lifestyle than the regular sea urchins, they don’t need their spines for defense. Therefore, their spines are shorter and more hair-like. In other words, they are modified to help the sea biscuit move around in sediment where they live and feed. Notice the spines in the pictures of the sea biscuit below:
Take a look at this video of a sand dollar moving through sediment in much the same way as a sea biscuit:
Sea biscuits use small tube feet/spines on their underside to transfer sediment containing food particles into their mouth. Kind of like a set of conveyor belts! Echinoids graze off the substrate using a jaw apparatus known as an Aristotle’s Lantern. Sea biscuits and sand dollars have a modified form of Aristotle’s Lantern that they use to crush and grind sand.
What’s in a Name Question #3 or Why is it Called Aristotle’s Lantern: It’s named after the Greek scientist and philosopher Aristotle, of course. Some scientists thought his writings referred to the jaw apparatus looking like a kind of a lantern, specifically a horn lantern. However, this has recently been suggested to be a mistranslation. Aristotle's lantern may actually refer to the globular shape of whole echinoids, which resemble the ancient lamps of Aristotle's time.
Aristotle’s Lanterns contains not one, not two, but five teeth ! Ouch!
Check out these pictures of a sea biscuit found in the Atlantic Ocean off the North Carolina coast and housed in the NC Museum of Natural Sciences collection:
Although not in the most pristine condition, one can still see the rounded shield-like shape and the remnants of a petal-like “star.” It is about 6-½ inches long.
For dinner tonight, a 3-course meal: Grilled sea pork sauteed with sea apples and served with sea biscuits for you carb lovers out there.
Part 2 of our “Smorgasbord of Food Offerings from the Sea” series