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Aside from the well-developed, vertebrate-like eyes of cephalopods, there are photoreceptors on the mantle margins of scallops and related bivalves. Molluscs are generally regarded members of the Lophotrochozoa,[73] a group defined by having trochophore larvae and, in the case of living Lophophorata, a feeding structure called a lophophore. Phylum Arthropoda Digestive System Overview, Function & Anatomy | How Do Arthropods Digest Food? [4] The proportion of undescribed species is very high. While there are slight variations depending on if the mollusk is a carnivore, omnivore or herbivore, the general setup of the mollusk's digestive system is the same. Carnivorous molluscs usually have simpler digestive systems. Most molluscs have only one pair of gills, or even only a singular gill. Unlike humans, who have a closed circulatory system, mollusks have an open circulatory system in which oxygen and carbon dioxide are exchanged across gill filaments. Which of the following is the correct description of the body cavity of Mollusks? It covers the top of the body and encloses the internal organs. Their venom is a complex mixture of toxins, some fast-acting and others slower but deadlier. Their classification is done by considering modifications of shell and foot. The paired siphons of some bivalves draw water in and expel it, using this action for respiration, filter feeding, excreting wastes, and reproduction. What type of symmetry do MOST mollusks have? The heart is a muscular organ that pumps blood through the circulatory system when its muscles contract. The sorting process is by no means perfect. [92] Procopius, writing on the Persian wars circa 550 CE, "stated that the five hereditary satraps (governors) of Armenia who received their insignia from the Roman Emperor were given chlamys (or cloaks) made from lana pinna. There are seven classes of Mollusks: Monoplacophora, Polyplacophora, Aplacophora, Gastropoda, Scaphapoda, Bivalvia and Cephalopoda. Terrestrial mollusks exchange gases with the surrounding air. The Latin word for mantle is pallium, and you may see that used in some texts. What are the four main body parts of most mollusks? | Socratic which part of the mollusk body contains organs? Budd, G. E. & Jensen, S. A critical reappraisal of the fossil record of the bilaterian phyla. Do you know which ones? Most mollusks have tentacles for feeding and sensing, and many have a muscular foot. [33] The foot carries a pair of statocysts, which act as balance sensors. Because they live at such depths, little is known about these mysterious sea creatures. answer choices Gastropods Bivalves Cephalopods arthropods Question 5 30 seconds Report an issue Q. Mollusks! | Zoology Quiz - Quizizz The ventricle pumps the hemolymph through a middorsal sinus (in solenogasters and scaphopods) or vessel (aorta) into the body tissues. To better organize out content, we have unpublished this concept. As a member, you'll also get unlimited access to over 88,000 Ecology of Mollusks. This has a single, "limpet-like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate, and is secreted by a mantle covering the whole upper surface. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. [16] The visceral mass, or visceropallium, is the soft, nonmuscular metabolic region of the mollusc. If you have, then you probably have encountered members of the phylum Mollusca.