Cryptocelidae Family of Flatworms
One Flatworm of the Cryptocelidae Family can be found in this website:
California Flatworm, Hylocelis californica. A representative of the Cryptocelidae Family of Flatworms.
Phylogeny: Marine Flatworms of the Cryptocelidae Family are within the phylum Platyhelminthes (Flatworms) and the subphylum Rhabditophora. These are the simplest of the worm groups and range in size from microscopic to several feet long; they are all very thin. They can be free-living or parasitic, and are found in both fresh and marine environments. The most well-known member of the Cryptocelidae Family is the parasitic tape worm, which lives in humans and is capable of reaching several feet in length. Cryptocelidae Flatworms are in the class Monogenea and the order Polycladida. The Cryptocelidae Family contains one subfamily, eight genera, and twenty-three species. Species in the Cryptocelidae Family are also commonly called Cryptocelids.
Morphology: The Flatworms are are oval, to elongate oval, in shape and flattened dorsally. They are unsegmented, soft-bodied invertebrates that are bilaterian, meaning they are equal on both sides of their centerline. They have lamellated rhabdites, rod-like granules in the cells of the epidermis. A second characteristic is that they have a duo-glandular adhesive system. This allows them to secrete an adhesive that attaches anchor cells to the substrate, allowing the animal to cling to the substrate. They also possess a substance that releases the anchor cells from the substrate allowing them to either cling to the substrate or become free swimming. The body has a high surface to volume ratio and has no skeletal structure. They possess highly branched digestive tracts of chocolate brown or dark green that form highly visible zigzag lines radiating from the central main intestine to the periphery. They are triploblastic, indicative that they are composed of three fundamental cell layers – outer ectoderm, middle mesoderm, and inner ectoderm. They have no body cavities (acoelomates) other than the gut, and they lack an anus. The same pharyngeal opening takes in food and expels waste. The gut is highly branched to allow intracellular food transport to all parts of the body with no cell being too far from the outside, making a flat shape a necessity. They take in oxygen but have no formal respiration system. The nervous system is very simple, being composed of two nerve cords running down each side of the body; they have two simple brains called ganglia, that are bundles of nerves. They do not have formal eyes but have two eyespots, which allow them to sense light. They move via tiny bristles called cilia and two layers of muscles under the skin. In an emergency they are capable of swimming via rhythmic muscular contractions. Some are brightly colored and contain toxic materials to help avoid predation. Cryptocelid Flatworms reach a maximum of 15 cm (5.9 inches) in length.
Habitat and Distribution: Cryptocelid Flatworms are found in a variety of habitats including rocks coral, sand, algae, and deep sea thermal vents. They live in the intertidal zone and to very deep water. Cryptocelid Flatworms are found worldwide in tropical to subtropical seas. Four species from this family are found in Mexican waters.
Reproduction: Cryptocelid Flatworms are hermaphroditic with each individual producing both eggs and sperm. They reproduce sexually with internal fertilization. They lay eggs in cases that contain a single egg that are attached to the undersides of rocks. The embryos may hatch into a planktonic larval stage or a miniature adult form. They have the ability to regenerate missing body parts with ease.
Ecosystems Roles: Cryptocelid Flatworms are either diurnal or nighttime predators that prey upon ascidians, insects, mollusks, small worms, and microscopic matter. They are preyed upon by fish and nudibranchs. They are utilized by the aquarium trade on a limited basis and as lab animals, but otherwise are not significant to humans. They are often associated with ascidians, bivalves and sponges.