In contrast, the midgut in placophores and conchifers is subdivided into a slender esophagus with a pair of glandular pouches, a distinct stomach with a pair of digestive glands, and a slender, often looped intestine. Mollusks include the largest invertebrates and the smartest invertebrates (the octopus). From the dorsal cerebral ganglia, two pairs of longitudinal nerve cords arise: a pair of lateral (pleural) nerve cords, often forming pleural ganglia (which innervate the mantle), and a ventral pair of pedal nerve cords, often forming pedal ganglia (which innervate the foot). Mollusca constitutes one of the largest phyla of animals, containing at least 47,000 different species and numbers of individuals. The protostyle or crystalline style may vary in form among the bivalves. we suggest a serial hom The simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur. Mollusca is a phylum which contains organisms such as snails, slugs, octopuses, squids, clams, and so on. Mollusca is a division of phyla which contains animals such as snails, slugs, octopuses, squids, clams, and more. Linnaeus, 1758. It includes such familiar organisms as snails, octopuses, squid, clams, scallops, oysters, and chitons. Although species-specific differences exist, its high level of complexity almost certainly is due to the cephalopods’ very active, fast-moving, predatory life style, and their complex behavior and extreme flexibility of response to different environmental situations. Most of the nervous currents are symmetrical and hit Their body has a cavity. Hemolymph is drained from ctenidia, gills, or other specialized respiratory epithelia into the respective auricles. Antagonistic neurohormonal control of reproductive activity and metabolic processes is performed in the gastropods through cerebral dorsal bodies and lateral lobes or juxtaposed organs and in the cephalopods through optic glands. Aside from the well-developed, vertebrate-like eyes of cephalopods, there are photoreceptors on the mantle margins of scallops and related bivalves. In general, it is more complex than those of roundworms or flatworms.Bivalves have a simple nervous system … A buccal nerve loop with paired ganglia generally supplies the radular apparatus in the head. 5. Annelids are a large invertebrate phylum, with over thousands of modern species such as ragworms, earthworms and leeches. Neurosecretions by cells outside the nerve cell bodies (ganglia) have been described in gastropods and cephalopods, the released hormones diffusing through the tissues rather than being concentrated in special organs. These ganglia are connected by connectives and commissures. The body is divided into head, dorsal visceral mass, and ventral muscular foot and mantle. Create your own unique website with customizable templates. The radula is used to bite, tear, and scrape various food materials. The phylum Mollusca includes the gastropods (snails, slugs, and periwinkles), bivalves (clams, oysters, mussels, and scallops), cephalopods... By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Octopus (Octopus vulgaris): Mollusks have a rather complex nervous system, which varies among species, with the most complex being the octopus. In primitive conchifers the stomach is of the so-called style sac type. The nervous system of mollusks varies greatly depending on the particular class. Class 1. The protostyle or the crystalline style are fully retained in the bivalves and gastropods that subsist on small microorganisms and detritus. 3. Hypothetical Plan of Molluscan Nervous System: The central nervous system consists of three pairs of ganglia, the cerebral, pedal and pleural ganglia. Heart rate in mollusks plays a crucial role in many metabolic processes, including excretion; hormones that affect the heart are released from the wall of veins in cephalopods or, in gastropods, from the subesophageal ganglia, the junction between the auricles and the ventricle.
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