Chitons are the common name for species in the Class Polyplacophora. Chitons are considered more primitive in relation to other groups within the phylum such as bivalves or cephalopods. There are 8 dorsal plates lining the dorsal surface of these organisms. There are many primitive species of the class Polyplacophora that are still extant. However, only a few species of Monoplacophorans still exist in the world today.
Gastropoda is a very diverse class of molluscs. The subclass Prosobranchia , are often identified by their coiled, cone shaped or tubular shells [1]. The mantel cavity is typically located on the anterior of the organism. Important distinctions of these organisms are the variations or the absence of radula. These organisms utilize Nephridia for excretion of nitrogenous waste.
One characteristic of gastropods is the presence of a calcareous operculum. This structure acts as a shielded plate that protects the organism by covering the opening when it is retracted into its shell. In the photo below, the dark oval in the center is the operculum. They are calciferous and rough to the touch, protecting the opening to the shell like a man-hole cover.
Nudibranchs are typically categorized as sea snails which lack shells. Often they are richly colored and captivating to the eye. Their magnificent beauty is the result of aposematism which is the bright coloration exhibited by these organisms that warns predators that they are toxic, distasteful or dangerous. The shell is open at both ends, and both the head and foot of the animal are at the broader end.
The animal creates a current through the shell using its cilia and occasional contractions of its muscles to bring in water for respiration, which exits the narrow end of the shell.
They live in the sediment and most feed chiefly on foraminiferans, but detritus, microbes, and other small prey are also taken by their fine, cilia-covered tentacles. Baba K. The mechanisms of absorption and excretion in a solenogastre, Epimeniaverrucosa Nierstrasz , studied by means of injection methods.
Bunje P. The Aplacophora: The naked molluscs. University of California Museum of Paleontology. Burghardt I. Molluscan diversity at Bunaken National Park, Sulawesi. Wallacea — Davies M. Giere O. Springer, New York, New York. Heath H. The Solenogastres. Cambridge, Massachusetts.
Marin F. Mucins and Molluscan Calcification. Morton B. Feeding and Digestion in Bivalvia. In The Mollusca: Physiology. Part 2, vol 5. Saleuddin, A. Orr J. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms.
Porter S. Seawater Chemistry and Early Carbonate Biomineralization. DOI: Ruppert E. Scheltema A. Journal of Natural History 28 6 — Salvini-Plawen L. Malacologia 19 2 — Seifarth W. Marine Flatworms of the World. Accessed June Tudge C. The Variety of Life: A survey and celebration of all the creatures that have ever lived. Walsby J. The feeding mechanism and ecology of the New Zealand pulmonate limpet, Gadinalea nivea. Journal of Zoology, 2 — What is EOL? What's New?
Despite their name, cuttlefish are not fish but mollusks. Recent studies indicate that cuttlefish are among the most intelligent invertebrates, with one of the largest brain-to-body size ratios of all invertebrates. Cuttlefish have an internal shell called the cuttlebone and eight arms and two tentacles furnished with suckers, with which they secure their prey. The Humboldt squid is a large, predatory invertebrate found in the waters of the Pacific Ocean.
A mysterious sea creature up to 7 feet long, with 10 arms, a sharp beak and a ravenous appetite, packs of fierce Humboldt Squid attack nearly everything they see, from fish to scuba divers.
Traveling in groups of 1, or more and swimming at speeds of more than 15 miles an hour, these animals hunt and feed together, and use jet propulsion to shoot out of the water to escape predators. Humboldt squid live at depths of between and about 2, feet, coming to the surface at night to feed. They live for approximately two years and spend much of their short life in the ocean's oxygen-minimum zone, where very little other life exists. Because they live at such depths, little is known about these mysterious sea creatures.
The Humboldt squid usually lives in the waters of the Humboldt Current, ranging from the southern tip of South America north to California, but in recent years, this squid has been found as far north as Alaska. Marine biologists are working to discover why they have headed north from their traditional homes off South America. When marine biologist Roger Hanlon captured the first scene in this video, he started screaming.
Hanlon, senior scientist at the Marine Biological Laboratory in Woods Hole, studies camouflage in cephalopods: squid, cuttlefish and octopuses. They are masters of optical illusion. Fish or squid? Mollusks Have you ever been to the ocean or eaten seafood? This figure shows some of the more common and familiar mollusks.
Structure and Function of Mollusks Mollusks are a very diverse phylum. Mollusk Reproduction Mollusks reproduce sexually.
Ecology of Mollusks Mollusks live in most terrestrial, freshwater, and marine habitats. The different classes of mollusks have different ways of obtaining food. Gastropods may be herbivores, predators, or internal parasites.
They live in both aquatic and terrestrial habitats. Marine species live mainly in shallow coastal waters. Gastropods use their foot to crawl slowly over rocks, reefs, or soil, looking for food. Bivalves are generally sessile filter feeders. They live in both freshwater and marine habitats.
They use their foot to attach themselves to rocks or reefs or to burrow into mud. Bivalves feed on plankton and nonliving organic matter. They filter the food out of the water as it flows through their mantle cavity. Cephalopods are carnivores that live only in marine habitats. They may be found in the open ocean or close to shore. They are either predators or scavengers. They generally eat other invertebrates and fish.
Where's the Octopus? Summary Mollusks are invertebrates such as snails, scallops, and squids.
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