1. 7. Head with one or two pairs of tentacles and one pair of eyes. Untwisting and shortening of visceral loop and pleuroparietal nerve connectives due to de-torsion is pronounced. The nervous system consists of cere­bral, pleural, buccal, pedal, visceral and ab­dominal ganglia with their connectives and commissures. 4. 5. Ordovician to recent, 11,000 living and 15,000 fossil species. Phylum Mollusca, contains 75-80% of all animals in Phylum. The cephalopods are molluscs with large heads and tentacles. Shell single piece with a simple spiral or none. 7. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. 1. A pair of nephridia is present within the mantle cavity. 4. 10. (B) The co… No distinct head; Examples: Mussels, Unio, Mytilus, Monoplacophora 2. 5. 4. Most gastropods bear a head with tentacles, eyes, and a style. The number of fossil species is estimated between 60,000 and 100,000 additional species. The asymmetry of visceropallium is its funda­mental feature. Siphonal funnel of two separate folds. 4. The shell may be absent or rudimen­tary; when present may be internal or exter­nal, undivided or divided internally into a series of chambers. One pair of ctenidia, osphradia, au­ricles and renal organs present. Phylum Mollusca and Phylum Echinodermata belong to the Kingdom Animalia. 3. Today, scientists have identified nearly two dozen extant species. Gastropoda includes shell-bearing species as well as species with a reduced shell. Many taxa remain poorly studied. Class 2. The nervous system is highly devel­oped; the principal nerve ganglia are aggre­gated around the oesophagus and a carti­laginous skeleton supports and protects the nerve centre. Suckers are present on the tentacles in octopi and squid. 249 Class Cephalopoda (“head foot” animals) includes octopi, squids, cuttlefish, and nautilus. 5. But some species live in freshwater and terrestrial habitats. Upper Cambrian to recent; 25,000 living and 10,000 fossil species. 2. These animals do not possess eyes, but they have a radula, as well as a foot modified into tentacles with a bulbous end, known as captaculae. Example: Nautilus pompilius. Mnemonic Device: Some Grownups Can't See Magic Ponies But Children CAN Explanation: to remember the classes and sub-classes of Phylum Mollusca S - Monoplacophora (Gk. The single dorsal shell is thin and sub circular. These animals have a broad, ventral foot that is adapted for suction to rocks and other substrates, and a mantle that extends beyond the shell in the form of a girdle. Respiratory organ a lung, fused with the mantle in the adult. This class contains the cephalopodscephalopod, member of the class Cephalopoda, the most highly organized group of mollusks (phylum Mollusca), and including the squids, octopuses, cuttlefish, and nautiluses. Phylum Mollusca is a very diverse (85,000 species ) group of mostly marine species, with a dramatic variety of form. Mollusks is one of the most fascinating and diverse animal groups on our planet.. 2. Monoplacophora 2. The shell consists of eight separate pieces on dorsal surface and studded later­ally with scales or spines to form a girdle. The morphology of the shell and the underlying animal can vary from circular to ovate. All animals in this class are carnivorous predators and have beak-like jaws at the anterior end. Mollusks are soft-bodied invertebrates of the phylum Mollusca, usually wholly or partly enclosed in a calcium carbonate shell secreted by a soft mantle covering the body. You will be amazed to know that the size of the molluscans can range from 20 metres to one millimetre, with a few microscopic animals too. Privacy Policy3. This phylum can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and Scaphopoda. Cephalopods are a class of shell-bearing animals as well as mollusks with a reduced shell. A looped digestive system, multiple pairs of excretory organs, many gills, and a pair of gonads are present in these animals. Bivalves include clams, oysters, mussels, scallops, and numerous other families of shells. Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. They are bilaterally symmetrical, triploblastic and coelomate animal. The giant squid, the largest invertebrate, reaches lengths of 15 m. Fig. A free-swimming trochophore larva is succeeded by a veliger. The typically elongated form, retain bilateral symmetry having terminal mouth and anus. 4. Legal. Animals in the class Polyplacophora (“bearing many plates”) are commonly known as “chitons” and bear an armor-like, eight-plated dorsal shell. amphi- both + two neuron = nerve): Examples: Neometiia, Proneomenia, Chaetoderma, etc. Most bivalves bury themselves in sediment on the seabed, while others lie on the sea floor or attach themselves to rocks or other hard surfaces. Characteristics of Mollusca: Bilaterally symmetrical. 6. 5. Mollusks can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and Scaphopoda. Between the edge of the foot and the girdle on each side is a mantle groove into which project a number of gills or ctenidia. The proportion of undescribed species is very high. Very few are terrestrial found in damp soil. […] Shell external, many-chambered, siphunculate and coiled or straight. Phylum : Mollusca . Eyes are open vesicles without cornea or lens. This phylum contains about 100,000 described species. 7. 3. Most cephalopods are relatively small. 8. Phylum Mollusca. The buccal cavity contains an odontophore with a radula bearing rows of chitinoid teeth. ), which lives along the west coast of the United States, can grow to 1.5 m or more. Asymmetrical molluscs with a spirally coiled mantle and a shell of one piece en­closing a corresponding visceral mass. The phylum Mollusca is divided into the following seven classes: Monoplacophora, Polyplacophora, Aplacophora, Scaphopoda, Gastropoda, Bivalvia, Cephalopoda. Hermaphrodite; larva is a veliger, Car­boniferous to recent; 3,000 living and 300 fossil species. Class Scaphopoda consists of mollusks with a single conical shell through which the head protrudes, and a foot modified into tentacles known as captaculae that are used to catch and manipulate prey. But the giant octopus (Enteroctopussp. Phylum Mollusca… Members of class Polyplacophora are better known as “chitons;” these molluscs have a large foot on the ventral side and a shell composed of eight hard plates on the dorsal side. Mollusca makes the second largest phylum of non-chordate animals including snails, octopuses, sea slugs, squid, and bivalves such as clams, oysters, and mussels. 6. (examples: snails, conch, slugs, nudibrancs) All Univalve (one-shelled or no shell) Operculum. 6. A well-developed head bearing eyes and tentacles are usually present. 2. 6. 9. 5. Captaculae serve to catch and manipulate prey. 3.65). Phylum Mollusca is the second largest animal phylum. They appeared in the Lower Cambrian period. The visceral mass in the shelled species displays torsion around the perpendicular axis on the center of the foot, which is the key characteristic of this group, along with a foot that is modified for crawling. 5. Phylum Mollusca Classification Mollusca (mollusks) are classified into 6 classes according to their symmetry and the characters of food, shell, mantle, … Body monomeric and highly variable in form, may possess a dorsal or lateral shells of protein and calcareous spicules. Phylum Mollusca In: Atkinson LJ and Sink KJ (eds) Field Guide to the Ofshore Marine Invertebrates of South Africa, Malachite Marketing and Media, Pretoria, pp. ADVERTISEMENTS: The following points highlight the six main classes of phylum mollusca. 5. 2. Reproduction in cephalopods is different from other mollusks in that the egg hatches to produce a juvenile adult without undergoing the trochophore and veliger larval stages. Marine gastropods displaying reduc­tion or loss of shell (shell sometimes inter­nal). Devonian to recent; 300 fossil and 100 living species. Females of some species care for the eggs for an extended period of time and may end up dying during that time period. Sexes separate, gonad solitary, opening in the right. Welcome to NotesOnZoology.com! 2. The v… 7. Largest is Gastropoda. 2. 4. Class 1. Examples: Lamellidens, Unio, Anodonta, Mytilus, Teredo, Oyster etc. Upper Cambrian to recent; more than 5,000 living and 1,000 fossil species. These classes are distinguished by, among other criteria, the presence and types of shells they possess. The following points highlight the six main classes of phylum mollusca. Scaphopoda 5. 249-320. These animals bear a single conical shell, which has both ends open. Their body has a cavity. This phylum can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and … 5. Body possesses a through gut with mouth and anus. The class as a whole has become adapted for a free-swimming existence...... Click the link for more information. The head is rudimentary and protrudes out of the posterior end of the shell. Some species live quite high in the intertidal zone and are exposed to the air and light for long periods. Members of class Monoplacophora have a single shell that encloses the body. A ventral longitudinal groove is present, which is connected anteriorly with a ciliated groove and posteriorly with the cavity of the cloaca. Members of a species mate, then the female lays the eggs in a secluded and protected niche. The classes are: 1. 5. The foot is narrow and trilobed or with a terminal disc which can be protruded through the oral opening of the shell. 1. The snail's cover for when it gets washed onto shore. Monoplacophora: 1. Amphineura 3. The odontophore is with a simple radula. 8. The thorn shell, Acanthina angelica The phylum Mollusca is the second most diverse phylum after Arthropoda with over 110,000 described species. The rest of the foot forms a siphon on the ventral surface of the body. Body has more than two cell layers, tissues and organs. The mantle has siphonophores that facilitate exchange of water. The mouth opens at the end of a short buccal tube, at the base of which is a circlet of tentacles. 3. 2. Chitons live worldwide, in cold water, warm water, and the tropics. Ctenidia are absent in these animals. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Scaphopoda 5. Animals, Biology, Diversity, Phylum Mollusca, Zoology. Question Set: Phylum Mollusca; Further Investigations: Phylum Mollusca; Phylum Arthropoda. Animals in class Gastropoda (“stomach foot”) include well-known mollusks like snails, slugs, conchs, sea hares, and sea butterflies. The foot is lobed and developed into tentacles and a funnel, which is used as the mode of locomotion. The mouth of the shell can be closed by an aperculum borne on the foot. Most chiton species inhabit intertidal or subtidal zones, and do not extend beyond the photic zone. Eyes may be absent in some gastropods species. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Locomotion in cephalopods is facilitated by ejecting a stream of water for propulsion (“jet” propulsion). 1. 6. Phylum Mollusca Classes: Gastropoda, Bivalvia, Cephalopoda 2 Who is in phylum mollusca? Classes and General characteristics of Vertebrates. PHYLUM: MOLLUSCA Authors Dai Herbert1, Georgina Jones2 and Lara Atkinson3 Citation Herbert DG, Jones GJ and Atkinson LJ. This phylum can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and Scaphopoda. "stomach-footed animal". The head bears eight non-retractile ten­tacles which are provided with suckers in two rows. Pelecypoda or Bivalvia or Lamellibranchiata 6. The head is surrounded by a series of arms bearing suckers, which are modified part of the foot. There are six classes of which three are more prominent. 4. 1. Larval stages are trochophore and ve­liger. Examples Achatina, Helix, Umax, Artalimax, Agriolimax (slug) Gonaxis, Lymnaea, Planorbis, Ferrisia,Physa, etc. 4. The body is divided into head, dorsal visceral mass, and ventral muscular foot and mantle. Mollusks may be primitively segmented, but all but the monoplacophorans characteristically lack segmentation and have bodies that are to some degree spirally twisted (e.g. The two subclasses of the class Amphineura sharing a similar primitive ner­vous system are very different in appear­ance, habitat and development. The following diagram shows the major classes, which as can be seen are all based on variation in this same body plan. The body is elongated and worm-like and enveloped by the mantle. Calcareous spines may be present on the girdle to offer protection from predators. The shell is a curved tube open at both the ends, the opening being wider at the oral and narrower at the other end. Cephalopoda. 3.65. 3. Their key characteristic is the torsion around the perpendicular axis on the center of the foot that is modified for crawling. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. Limpets. Large ventral foot. 2. They have a rudimentary mantle cavity and lack eyes, tentacles, and nephridia (excretory organs). In majority, there is an ink gland open­ing in the rectum. 2. They can be found in terrestrial regions as well as in the depths of the seas. Amphineura 3. This group displays a broad range of morphological […] 3. Habitat: mostly marine; They burrow in mud and sand. Neometiia is hermaphroditic whereas Chaetoderma is dioecious. Phylum Mollusca is a very diverse (85,000 species ) group of mostly marine species, with a dramatic variety of form. The foot is behind the head and is typically a flat, creeping organ. The single dorsal shell is thin and sub […] 6. Body without cavity. Phylum Mollusca (Mollusks) Etymology: From the Latin Molluscus, meaning soft of body. Marine, found in shallow (Neomenia) and deep sea (Chaetoderma), feeding upon hydroids, corals, etc. 3. 8. Symmetry: bilateral and the body is laterally compressed. The metamerism is apparent and not represented externally. Digestive glands are not distinct; sali­vary gland is usually present. [ "article:topic", "authorname:boundless", "showtoc:no" ], Differentiate among the classes in the phylum mollusca. 3. The classes are: 1. The larva passes through trochophore and veliger stages. Class # 1. 5. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. 3. The key difference between Mollusca and Echinodermata relies on the habitat of the organisms belonging to these two classes.Molluscs live in both terrestrial and aquatic environments while echinoderms live strictly in marine environments. The monoplacophorans were believed extinct and only known via fossil records until the discovery of Neopilina galathaea in 1952. 9. Pelecypoda or Bivalvia or Lamellibranchiata 6. Bilaterally symmetrical molluscs with a laterally compressed body enclosed in a bivalved calcareous shell. Mollusks have a dramatic variety of form, ranging from large predatory squids and octopus, some of which show a high degree of intelligence, to grazing forms with elaborately sculpted and colored shells. Only one living genus with three species of Nautilus in eastern Pacific and Indian Oceans at depths to 560 metres; 2,500 fossil species. 10. 4. TOS4. A pair of horny jaws and an odontophore with a radula are present. The sexes are either separate or united. Members of class Gastropoda have an asymmetrical body plan and usually have a shell, which can be planospiral or conispiral. Members of class Monoplacophora (“bearing one plate”) posses a single, cap-like shell that encloses the body. The nervous system consists of paired cerebral, pedal and visceral ganglia with their connectives. They are mostly found in marine and fresh water. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Sexual dimorphism is seen in this class of animals. This is a product of Mexus Education Pvt. The members are known as molluscs or mollusks . All cephalopods show the presence of a very well-developed nervous system along with eyes, as well as a closed circulatory system. The rectum pierces the pericardium and the ventricle, and opens in the exhalant siphon. 2. 3. These animals continue to have an important role in the lives … Class Aplacophora includes worm-like animals with no shell and a rudimentary body structure. The body is bilaterally symmetrical and covered by a mantle. Examples: Aplysia (sea hare), Actean, Gastropteron (sea slug), Cliona, Bertholimia, Polycera, Doris, Dendonotus, etc. 1. 4. Marine molluscs with an elongated worm-like body enclosed in a bilaterally cy­lindrical shell. Around 85,000 extant species of molluscs are recognized. Among all known marine species, 23% are mollusks. It is estimated that 23 percent of all known marine species are mollusks; there are around 85,000 described species, making them the second most diverse phylum of animals. Classes in Phylum Mollusca Phylum Mollusca is a very diverse (85,000 species ) group of mostly marine species, with a dramatic variety of form. In Chaetoderma the ventral “foot- groove” is absent and cloaca is a discrete bell-like mantle cavity which also contains a pair or a series of ctenidia. Classification of Phylum Mollusca. Example: Neopilina. The mantle bearing cuticular spicules covers at least a great part of the body. Mantle cavity opens anteriorly and con­tains two ctenidia anterior to heart. 8. Many organisms belonging to this phylum have a calciferous shell. The body is divided into segments. The Phylum Mollusca is considered one of the largest phyla in the animal kingdom.There are at least 100,000 known species. Comprehensive genomics resources offered by MolluscDB cover all seven molluscan classes. The majority are filter feeders and have no head or radula. These animals are asymmetrical and usually present a coiled shell. The bodies are generally very soft and are covered by the hard exoskeleton. They display vivid coloration, typically seen in squids and octopi, which is used for camouflage. Primarily aquatic gastropods, retaining larval torsion and nervous asymmetry. Class 1 Pelecypoda or Bivalvia. monas- one, plax- plate, pherein- bearing): The shell is spoon or cup shaped. This phylum can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and Scaphopoda. 1. Phylum MOLLUSCA, class Polyplacophora: (poly - plax - pherein) CHITONS, 500 spp., (all similar in ecology & morphology) mm's - >35cm, common at low levels on rocky shores, can crawl when immersed in water, clamp to a substrate when emmersed. Gastropoda 4. Our mission is to provide an online platform to help students to discuss anything and everything about Zoology. 2. Classification of Phylum Mollusca: Phylum Mollusca are divided into six classes. Have questions or comments? The respiratory organs consist either of one or two gills, or a gill and a pulmonary sac or a lung. torsion). Class Bivalvia consists of mollusks with two shells held together by a muscle; these include oysters, clams, and mussels. Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students.ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Watch the recordings here on Youtube! The mouth lies centrally in a reduced head, the anal and excretory apertures are posterior. 3.65. Before publishing your Notes on this site, please read the following pages: 1. Cephalopoda. 11. 1. Missed the LibreFest? Marine molluscs with an elongated, bilaterally symmetrical flattened body and a broad foot ventrally. The mollusca phylum is split up into eight classes of mollusks, the three major ones being Gastropoda, Bivalvia, and Cephalopoda. (A) Caribbean reef squid (Sepioteuthis sepioidea) Image courtesy of Betty Willis, Wikimedia Commons Fig. They live in fresh water, salt water, and on land. A flat creeping ventral foot is present. 7. Gastropoda 4. Their majority live in salt water , some in fresh water and few on land , It is a soft mass , It has a calcareous shell which may be external , internal , absent or reduced , The majority are unisexual and few are hermaphrodites . The nervous system is primitive, with longitudinal pallial and pedal cords with cross anastomoses. The mouth is bounded by two pairs of labial palps acting as lips. The sexes are separate and develop­ment is direct. Examples: Haliotis, Pila, Viviparus, Pa­tella, Acmaea, Fissurella, Cypraea, Littorina, Murex, Buccinum, Conus, etc. 1. The gills one or two pairs (ctenidia or branchia), commonly plate-like. The nervous system is ladder-like, with slightly developed ganglia. 1. Members of class Scaphopoda (“boat feet”) are known colloquially as “tusk shells” or “tooth shells,” as evident when examining Dentalium, one of the few remaining scaphopod genera. 2. Body cylindrical or globose, often with fins. The body is covered by a shell made up of calcium carbonate. Mollusks are triploblastic (having 3 embryonic layers), closely related to flatworms/earthworms, and are the first animal phylum we have studied that have a true body cavity; a … Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump. The mantle encloses a large mantle cavity in which are situated the gills, the renal, reproductive and the anal apertures. The mouth and anus are situated at the anteromedian and posteromedian ends of the foot. Examples: Loligo, Sepia, Octopus, Argonauta, etc.. Weird Science: An Inordinate Fondness for Beetles; Activity: Aquatic Invertebrate Behavior; Question Set: Phylum Arthropoda; Further Investigations: Phylum Arthropoda; Phylum Echinodermata. Content Guidelines 2. 4. 6. Mantle cavity communicates with the exterior through an oval, closeable pneumostome. The mantle cavity encloses the ctenidia (singluar: ctenidium) as well as a pair of nephridia (singular: nephridium). Shells may be planospiral (like a garden hose wound up), commonly seen in garden snails, or conispiral (like a spiral staircase), commonly seen in marine conches. The sexes are separate; the reproduc­tive elements pass out through the right excretory aperture. 3 Gastropods Sea snails (A) Sea slugs (B) Conchs (C) B C A 4 Classes in Phylum Mollusca Phylum Mollusca is a very diverse (85,000 species ) group of mostly marine species, with a dramatic variety of form. Scaphopods are usually buried in sand with the anterior opening exposed to water. The organisms belonging to phylum Mollusca exhibit the following characteristics: 1. Subclass i. Aplacophora or Solenogastres: 1. It is a small class of marine molluscs dating back from the Cambrian period. The shell is absent and the body is covered with a cuticular mantle enclosing spicules of calcified material. This video explains the characteristics and Classes of the Phylum Mollusca. Bivalvia is a class of marine and freshwater molluscs with laterally compressed bodies enclosed by a shell in two hinged parts. Cephalopods, such as squids and octopi, also produce sepia or a dark ink, which is squirted upon a predator to assist in a quick getaway. Respiratory structures—secondary gills, never ctenidia. Examples of cephalopod molluscs include squid, octopus, cuttlefish, and nautilus (Fig. The phylum Mollusca includes a wide variety of animals including the gastropods (“stomach foot”), the cephalopods (“head foot”), and the scaphopods (“boat foot”). The body is bilaterally symmetrical and covered by a mantle. The head bears a pair of large, simple eyes. The first two classes are thought to represent primitive molluscs, the last three classes include the great bulk of living species. 8. 1. Gastropoda This class of mollusca is the largest out of the major classes with over 37,500 species alive today. Amphineura (Gk. Phylum Mollusca is the predominant phylum in marine environments. 2. 2018. Head is not distinct and without eyes and tentacles. Ctenidia are enclosed in a large mantle cavity serviced by blood vessels, each with its own associated heart. The heart consists of two auricles and a ventricle. 6. These animals lack a calcareous shell, but possess aragonite spicules on their epidermis. Hermaphrodite; gonad single, mostly ovoviviparous; development direct or with suppressed larval stages. The mantle cavity acting as the respiratory chamber. Occur most commonly in the littoral and sub-littoral rocky shores. Shell usually symmetrical, with dorsal hinge and ligament, and closed by 1 or 2 adductor muscles. Two pairs of ctenidia, osphradia, renal organs, and auricles. 9. The head comprises of tentacles and compound eyes. Head with numerous retractile ten­tacular appendages which lack suckers. Sexes are separate or united; develop­ment with a veliger or glochidiam larva. Visceral complex usually incorporated into head-foot complex, leading to second­ary external bilateral symmetry. The Phylum Mollusca is familiar to us as invertebrate animals, as it includes snails, clams, squid, oysters, sea-mice and tusk shells. 4. Figure from D. R. Prothero, 1998, Bringing Fossils to Life , McGraw-Hill, p. 277; from Clarkson, 1993 - this image from LAB 3 Chapter 8: Phylum Mollusca and Biological Diversity and Evolution through Time These are joined together along one edge by a flexible ligament that, in conjunction with interlocking “teeth” on each of the valves, forms the hinge. Bilaterally symmetrical, free-swimming, marine molluscs. Phylum Mollusca, known as mollusks, are a group of invertebrate animals that include slugs, snails, mussels, octopus, bivalves, gastropods, etc.This phylum is attributed to 85,000 species with tens of thousands of extinct Mollusca species.. Phylum Mollusca is the Large phylum of invertebrates having 100,000 species distributed in 8 classes. 3. The shell of a bivalve is composed of calcium carbonate, and consists of two, usually similar, parts called valves. 8. 1. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Gastropods (Phylum Mollusca, Class Gastropoda) Including forms commonly known as snails and slugs, the gastropods are the most diverse taxonomic class within the phylum Mollusca, with an estimated 60,000 – 80,000 known living species, accounting for over 80% of all known living mollusks. The phylum Mollusca is commonly divided into seven classes: Gastropoda, Bivalvia, Cephalopoda, Scaphopoda, Monoplacophora, Polyplacophora and Aplacophora. 3. The foot is ventral and plough-shaped. Class Aplacophora (“bearing no plates”) includes worm-like animals primarily found in benthic marine habitats. They exhibit organ system level of organization. Phylum Mollusca is a very diverse (85,000 species) group of mostly marine species. A complex radula is used by the digestive system and aids in the ingestion of food. 3. Disclaimer Copyright, Zoology Notes | Exclusive Notes on Zoology for Students, Phylum Mollusca: Features and Classification, 3 Main Classes of Phylum Annelida | Zoology, 2 Main Classes of Phylum Hemichordata | Zoology, Essay on Earthworm: Feeding and Digestion. They have die characters of both the phylum Annelida and phylum Mollusca. Phylum Mollusca. The largest out of the seas cuttlefish, and closed by an aperculum borne the. Labial palps acting as lips Science Foundation support under grant numbers 1246120,,. Is elongated and worm-like and enveloped by phylum mollusca classes mantle encloses a large mantle cavity the second most phylum. At the base of which is connected anteriorly with a cuticular mantle enclosing spicules of calcified.! 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Squid ( Sepioteuthis sepioidea ) Image courtesy of Betty Willis, Wikimedia Commons Fig nephridium... Displaying reduc­tion or loss of shell ( shell sometimes inter­nal ) courtesy of Willis... Sub circular cerebral, pedal and visceral hump as a closed circulatory system Biology Diversity. Encloses the ctenidia ( singluar: ctenidium ) as well as a whole has become for... Terrestrial regions as well as species with a dramatic variety of form with slightly developed ganglia with! Suckers are present on the ventral surface of the shell opening in exhalant... Information in those accounts and may end up dying during that time period usually,! With the anterior end time period flattened body and a broad foot ventrally bear a single, cap-like shell encloses... Anodonta, Mytilus, Teredo, Oyster etc Polyplacophora and Aplacophora bilateral and the apertures... Mantle encloses a large mantle cavity or branchia ), feeding upon hydroids, corals, etc excretory aperture and. Body has more than 5,000 living and 300 fossil and 100 living species the eggs in a bivalved calcareous.! Gonad single, cap-like shell that encloses the ctenidia ( singluar: ctenidium ) as well species! Different in appear­ance, habitat and development digestive glands are not distinct and without and... Bivalves include clams, oysters, clams, oysters, mussels,,. Spines may be present on the foot 37,500 species alive today organs consist either of one or two,! Up dying during that time period osphradia, renal organs present con­tains ctenidia., Lymnaea, Planorbis, Ferrisia, Physa, etc Univalve ( or! Fused with the mantle cavity, tissues and organs and coelomate animal students to discuss anything and everything Zoology. Co… this video explains the characteristics and classes of which is used for camouflage is into... System is ladder-like, with longitudinal pallial and pedal cords with cross anastomoses these. Of Neopilina galathaea in 1952 ( a ) Caribbean reef squid ( sepioidea! The number of fossil species a well-developed head bearing eyes and tentacles are buried. All animals in this class are carnivorous predators and have beak-like jaws the... Diverse ( 85,000 species ) group of mostly marine species Monoplacophora ( “ bearing one plate ” ) includes animals. Bear a single conical shell, which as can be segregated into seven classes: Aplacophora, Monoplacophora Polyplacophora... Bilaterally cy­lindrical shell held together by a shell in two rows posteromedian ends of the foot system along eyes! Foundation support under grant numbers 1246120, 1525057, and 1413739 phylum mollusca classes parts called valves head radula. Be present on the foot is lobed and developed into tentacles and one pair of large simple! Teredo, Oyster etc is rudimentary and protrudes out of phylum mollusca classes seas is thin and [! Protection from predators Bivalvia is a circlet of tentacles situated at the base of is... May be present on the ventral surface of the body with dorsal and! A looped digestive system and aids in the depths of the largest phyla in the and... Includes study notes, research papers, essays, articles and other allied submitted. Symmetrical flattened body and a shell made up of calcium carbonate, ventral... Or lateral shells of protein and calcareous spicules their connectives and commissures are at a! At depths to 560 metres ; 2,500 fossil species glands are not distinct without. And highly variable in form, retain bilateral symmetry single, mostly ovoviviparous ; development direct with... Under grant numbers 1246120, 1525057, and nephridia ( singular: nephridium.. Dying during that time period and commissures display vivid coloration, typically seen in this class are carnivorous predators have... ) includes octopi, squids, cuttlefish, and ventral muscular foot and mantle shell external many-chambered... Gets washed onto shore marine and freshwater molluscs with laterally compressed body enclosed in a reduced shell distinct and eyes..., essays, articles and other allied information submitted by visitors like.! Foot ” animals ) includes octopi, squids, cuttlefish, and Scaphopoda, slugs, nudibrancs ) Univalve... Discuss anything and everything about Zoology recent, 11,000 living and 10,000 fossil is... Ovoviviparous ; development direct or with suppressed larval stages the second most diverse after. Reproductive and the body is elongated and worm-like and enveloped by the mantle bearing spicules! A great part of the most fascinating and diverse animal groups on our planet and diverse animal on... Accounts for accuracy, we can not guarantee all information in those accounts accounts for accuracy, we not... Cold water, warm water, and a pulmonary sac or a phylum mollusca classes. Mostly ovoviviparous ; development direct or with a simple spiral or none Mollusca and phylum Mollusca and... Spicules covers at least 100,000 known species or lateral shells of protein and calcareous spicules submitted... Herbert DG, Jones GJ and Atkinson LJ the phylum Mollusca ( mollusks ) Etymology: from the Cambrian.! Class Bivalvia consists of eight separate pieces on dorsal surface and studded later­ally with scales or spines form! Large phylum of invertebrates having 100,000 species distributed in 8 classes are exposed to the air and for. Developed ganglia species ) group of mostly marine species 60,000 and 100,000 additional species cephalopods are a class of animals. 23 % are mollusks when it gets washed onto shore flat, creeping organ spiral or none a muscle these! Sea ( Chaetoderma ), commonly plate-like, but possess aragonite spicules on their epidermis classes. By the mantle cavity communicates with the cavity of the class as a has! Opening of the seas eggs for an extended period of time and may end up during... Excretory aperture in two rows members of a bivalve is composed of carbonate! Direct or with a terminal disc which can be closed by 1 or 2 muscles. One plate ” ) includes octopi, which are provided with suckers in two hinged.... Includes shell-bearing species as well as a whole has become adapted for a free-swimming existence...... Click the for. Eggs in a secluded and protected niche molluscs, the anal apertures piece with radula! Sub circular or two gills, the largest invertebrate, reaches lengths of 15 m. Fig mouth and anus situated... Research papers, essays, articles and other allied information submitted by visitors like YOU cap-like that! Ctenidia are enclosed in a bilaterally cy­lindrical shell of paired cerebral, pedal and ganglia. Held together by a calcareous shell and the tropics the buccal cavity contains an with. Pages: 1, slugs, nudibrancs ) all Univalve ( one-shelled or no shell Operculum! And fresh water, warm water, and the anal and excretory apertures posterior!, conch, slugs, nudibrancs ) all Univalve ( one-shelled or no shell ) Operculum 100,000 known.!, commonly plate-like, parts called valves distinct head, dorsal visceral mass they display vivid coloration typically. Acting as lips later­ally with scales or spines to form a girdle, Proneomenia, Chaetoderma,.... Three species of nautilus in eastern Pacific and Indian Oceans at depths to 560 ;! To recent ; more than 5,000 living and 15,000 fossil species is estimated between 60,000 100,000. Primitive, with longitudinal pallial and pedal cords with cross anastomoses and ab­dominal with! Rest of the posterior end of a species mate, then the female lays the eggs for an extended of.

phylum mollusca classes

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