{"id":127,"date":"2015-07-18T04:18:02","date_gmt":"2015-07-18T04:18:02","guid":{"rendered":"https:\/\/courses.candelalearning.com\/bio2labsxmaster2\/?post_type=chapter&#038;p=127"},"modified":"2016-01-06T22:18:27","modified_gmt":"2016-01-06T22:18:27","slug":"reading-mollusks","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/tcc-biolab\/chapter\/reading-mollusks\/","title":{"raw":"Reading: Mollusks","rendered":"Reading: Mollusks"},"content":{"raw":"This laboratory exercise covers the following animals. You should learn this classification scheme and be able to classify the animals into these categories.\r\n<ul>\r\n\t<li>Phylum: Mollusca (Mollusks)\r\n<ul>\r\n\t<li>Class: Polyplacophora (Chitons)<\/li>\r\n\t<li>Class: Gastropoda (snails)<\/li>\r\n\t<li>Class: Bivalvia (Clams)<\/li>\r\n\t<li>Class: Cephalopoda (Nautilus, Squid, Octopus)<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\nAll mollusks have a <strong>visceral mass<\/strong>, a <strong>mantle<\/strong>, and a <strong>foot<\/strong>. The visceral mass contains the digestive, excretory, and reproductive organs. The mantle is a covering. It may secrete a shell. The foot is muscular and is used for locomotion, attachment, and\/or food capture.\r\n\r\nThe mantle and foot can be seen in the figure 1. The visceral mass is underneath the gill.\r\n\r\n[caption id=\"attachment_405\" align=\"alignnone\" width=\"600\"]<img class=\"wp-image-405\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10.jpg\" alt=\"Figure 1.\" width=\"600\" height=\"383\" \/> Figure 1.[\/caption]\r\n\r\nThere may be a <b>radula<\/b>, a structure that resembles a tongue but contains hard plates and is often used for scraping food.\u00a0The coelom is reduced and limited to the region near the heart.\r\n\r\nMost mollusks have an <b>open circulatory system<\/b> but cephalopods (squids, octopus) have a <b>closed circulatory system<\/b>.\u00a0The blood pigment of mollusks is hemocyanin, not hemoglobin.\u00a0The heart of a clam can be seen in the photograph below.\u00a0Bivalves have three pairs of ganglia but do not have a brain.\r\n\r\nMost mollusks have separate sexes but most snails (gastropods) are hermaphrodites. Some marine mollusks have a ciliated larval form called a <b>trochophore<\/b>.\r\n<h2>Chitons (Class: Polyplacophora)<\/h2>\r\nChitons have a dorsal shell composed of 8 plates. A ventral foot is used for locomotion and for attachment to rocks. It pulls itself close to rocks for protection.\u00a0Observe the chiton on display.\r\n\r\n[caption id=\"attachment_396\" align=\"alignnone\" width=\"1024\"]<img class=\"wp-image-396 size-large\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-1024x381.jpg\" alt=\"Figure 1. Left: chiton, dorsal surface. Right: ventral surface\" width=\"1024\" height=\"381\" \/> Figure 2. Left: chiton, dorsal surface. Right: ventral surface[\/caption]\r\n<h2>Snails\u2014Class Gastropoda<\/h2>\r\nGastropods have an elongated, flattened foot and usually a head and shell although nudibranchs (sea slugs) and terrestrial slugs lack a shell.\r\n\r\nMost are marine but there are also numerous freshwater and terrestrial species.\u00a0Herbivorous gastropods use a radula to scrape food from surfaces. Carnivores may use a radula to bore a hole through surfaces such as bivalve (clam) shells.\u00a0Some gastropods such as the slug (below) do not have a shell.\r\n\r\nThe larvae undergo <b>torsion<\/b> during development. It is a twisting that positions the visceral mass so that the anus is above the head. It is due to one side of the visceral mass growing faster than the other. The advantage (or function) of torsion is uncertain but it may be to balance the animal or it may be to allow the head to be withdrawn into the shell first when predators approach.\r\n\r\nObserve the snails and slugs on display.\r\n\r\n[caption id=\"attachment_397\" align=\"alignnone\" width=\"500\"]<img class=\"wp-image-397\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug.jpg\" alt=\"Figure 2. A slug. Slugs do not have shells.\" width=\"500\" height=\"374\" \/> Figure 3. A slug. Slugs do not have shells.[\/caption]\r\n<h3>Gas Exchange (Respiration)<\/h3>\r\nSome gastropod species are terrestrial and have lungs for gas exchange, others are aquatic and use gills.\r\n\r\nThe space near the entrance to the shell that is bound by the mantle is the <strong>mantle cavity<\/strong>. Aquatic gastropods have gills located in the mantle cavity. The mantle of terrestrial gastropods functions as a lung.\r\n<h2>Bivalves\u2014Clams and relatives (Class: Bivalvia)<\/h2>\r\nBivalves have two shells (valves) held closed by powerful muscles. The shell is produced by the underlying mantle; it grows along the outer margins.\u00a0They use their foot for burrowing. Mussels use their foot for the production of threads for attachment.\r\n\r\nThe gills are large because they are used for filter-feeding as well as respiration. Food is trapped by mucus on the gills and moved by cilia. Water enters and exits through siphons.\r\n\r\nObtain a preserved clam for dissection and place it on a dissecting tray. Remove one of the <strong>valves<\/strong> (shells) by inserting a scalpel and cutting the adductor muscles on each side of the hinge. See the diagram below for the location of the <strong>adductor muscles<\/strong>.\r\n\r\n[caption id=\"attachment_398\" align=\"alignnone\" width=\"500\"]<img class=\"wp-image-398\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles.jpg\" alt=\"Figure 3. Adductor muscles of a clam.\" width=\"500\" height=\"334\" \/> Figure 4. Adductor muscles of a clam.[\/caption]\r\n\r\n[caption id=\"attachment_399\" align=\"alignnone\" width=\"1024\"]<img class=\"wp-image-399 size-large\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-1024x397.jpg\" alt=\"cuttingmuscles\" width=\"1024\" height=\"397\" \/> Figure 5. The anterior and posterior adductor muscles being cut so that the valves can be pulled apart.[\/caption]\r\n\r\nThe <strong>mantle<\/strong> is a membrane that surrounds the internal structures and is characteristic of all mollusks. The portion of the mantle from the exposed surface may have remained attached to the valve that was removed or it may be covering the internal structures. Find the mantle and if necessary, remove it to expose the internal structures of the clam.\r\n\r\nIdentify the foot, visceral mass, gills, and labial palps. The gills are large because they are used for filter-feeding as well as respiration. Food is trapped by mucus on the gills and moved by cilia to the mouth. Cilia on the labial palps also direct food and mucus to the mouth.\r\n\r\n[caption id=\"attachment_400\" align=\"alignnone\" width=\"500\"]<img class=\"wp-image-400\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3.jpg\" alt=\"Figure 5. \" width=\"500\" height=\"403\" \/> Figure 6.[\/caption]\r\n\r\nThe heart can be found in the area dorsal to and slightly posterior to the visceral mass. The coelom of bivalves is reduced and\u00a0limited to the area surrounding the heart. Because the coelom is reduced, it is difficult to see the digestive organs. Cut through the visceral mass and identify the intestine.\r\n\r\n[caption id=\"attachment_401\" align=\"alignnone\" width=\"500\"]<img class=\"wp-image-401\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005.jpg\" alt=\"Figure 6. \" width=\"500\" height=\"375\" \/> Figure 7.[\/caption]\r\n\r\nIn the photograph below, the foot and visceral mass have been lifted so that the mouth can be seen. Notice the labial palps on either side of the mouth.\r\n\r\n[caption id=\"attachment_402\" align=\"alignnone\" width=\"500\"]<img class=\"wp-image-402\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures.jpg\" alt=\"Figure 7. \" width=\"500\" height=\"375\" \/> Figure 8.[\/caption]\r\n<h2>Squid, Octopus, Nautilus, and Relatives (Class: Cephalopoda)<\/h2>\r\nCephalopods are predators and live in a marine environment.\u00a0A closed circulatory system allows them to move rapidly in pursuit of prey.\u00a0They move by jet propulsion; water in the mantle cavity is squirted rapidly through a siphon.\u00a0The foot has evolved into tentacles around head.\u00a0Cephalopods have a powerful beak-like structure to tear apart prey.\u00a0The sense organs of cephalopods are well developed.\r\n\r\nMollusks are the simplest animals with eyes. Some mollusks have <i><b>lenses <\/b><\/i>and therefore are capable of forming clear images. The camera-type eyes of some cephalopods (squid, octopus) are capable of focusing and forming clear images. Cephalopods are fast-moving predators and well-developed camera-type eyes help them catch prey.\r\n\r\nWell-developed brains (especially in octopuses) give them a high learning capacity. Cephalopods can hide from enemies by releasing a dark colored fluid from ink sacs.\r\n<h3>Shells<\/h3>\r\nThe shell of a nautilus encloses the animal. A squid's shell is small and internal. Octopuses do not have shells. Examine representative cephalopods on display.\r\n\r\n[caption id=\"attachment_403\" align=\"alignnone\" width=\"631\"]<img class=\"wp-image-403 size-full\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid.jpg\" alt=\"Figure 7. A Squid\" width=\"631\" height=\"259\" \/> Figure 9. A Squid[\/caption]","rendered":"<p>This laboratory exercise covers the following animals. You should learn this classification scheme and be able to classify the animals into these categories.<\/p>\n<ul>\n<li>Phylum: Mollusca (Mollusks)\n<ul>\n<li>Class: Polyplacophora (Chitons)<\/li>\n<li>Class: Gastropoda (snails)<\/li>\n<li>Class: Bivalvia (Clams)<\/li>\n<li>Class: Cephalopoda (Nautilus, Squid, Octopus)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>All mollusks have a <strong>visceral mass<\/strong>, a <strong>mantle<\/strong>, and a <strong>foot<\/strong>. The visceral mass contains the digestive, excretory, and reproductive organs. The mantle is a covering. It may secrete a shell. The foot is muscular and is used for locomotion, attachment, and\/or food capture.<\/p>\n<p>The mantle and foot can be seen in the figure 1. The visceral mass is underneath the gill.<\/p>\n<div id=\"attachment_405\" style=\"width: 610px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-405\" class=\"wp-image-405\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10.jpg\" alt=\"Figure 1.\" width=\"600\" height=\"383\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10.jpg 640w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10-300x191.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10-65x41.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10-225x143.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/Image10-350x223.jpg 350w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p id=\"caption-attachment-405\" class=\"wp-caption-text\">Figure 1.<\/p>\n<\/div>\n<p>There may be a <b>radula<\/b>, a structure that resembles a tongue but contains hard plates and is often used for scraping food.\u00a0The coelom is reduced and limited to the region near the heart.<\/p>\n<p>Most mollusks have an <b>open circulatory system<\/b> but cephalopods (squids, octopus) have a <b>closed circulatory system<\/b>.\u00a0The blood pigment of mollusks is hemocyanin, not hemoglobin.\u00a0The heart of a clam can be seen in the photograph below.\u00a0Bivalves have three pairs of ganglia but do not have a brain.<\/p>\n<p>Most mollusks have separate sexes but most snails (gastropods) are hermaphrodites. Some marine mollusks have a ciliated larval form called a <b>trochophore<\/b>.<\/p>\n<h2>Chitons (Class: Polyplacophora)<\/h2>\n<p>Chitons have a dorsal shell composed of 8 plates. A ventral foot is used for locomotion and for attachment to rocks. It pulls itself close to rocks for protection.\u00a0Observe the chiton on display.<\/p>\n<div id=\"attachment_396\" style=\"width: 1034px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-396\" class=\"wp-image-396 size-large\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-1024x381.jpg\" alt=\"Figure 1. Left: chiton, dorsal surface. Right: ventral surface\" width=\"1024\" height=\"381\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-1024x381.jpg 1024w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-300x112.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-65x24.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-225x84.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons-350x130.jpg 350w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/chitons.jpg 1291w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<p id=\"caption-attachment-396\" class=\"wp-caption-text\">Figure 2. Left: chiton, dorsal surface. Right: ventral surface<\/p>\n<\/div>\n<h2>Snails\u2014Class Gastropoda<\/h2>\n<p>Gastropods have an elongated, flattened foot and usually a head and shell although nudibranchs (sea slugs) and terrestrial slugs lack a shell.<\/p>\n<p>Most are marine but there are also numerous freshwater and terrestrial species.\u00a0Herbivorous gastropods use a radula to scrape food from surfaces. Carnivores may use a radula to bore a hole through surfaces such as bivalve (clam) shells.\u00a0Some gastropods such as the slug (below) do not have a shell.<\/p>\n<p>The larvae undergo <b>torsion<\/b> during development. It is a twisting that positions the visceral mass so that the anus is above the head. It is due to one side of the visceral mass growing faster than the other. The advantage (or function) of torsion is uncertain but it may be to balance the animal or it may be to allow the head to be withdrawn into the shell first when predators approach.<\/p>\n<p>Observe the snails and slugs on display.<\/p>\n<div id=\"attachment_397\" style=\"width: 510px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-397\" class=\"wp-image-397\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug.jpg\" alt=\"Figure 2. A slug. Slugs do not have shells.\" width=\"500\" height=\"374\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug.jpg 640w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug-300x225.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug-65x49.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug-225x168.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/slug-350x262.jpg 350w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p id=\"caption-attachment-397\" class=\"wp-caption-text\">Figure 3. A slug. Slugs do not have shells.<\/p>\n<\/div>\n<h3>Gas Exchange (Respiration)<\/h3>\n<p>Some gastropod species are terrestrial and have lungs for gas exchange, others are aquatic and use gills.<\/p>\n<p>The space near the entrance to the shell that is bound by the mantle is the <strong>mantle cavity<\/strong>. Aquatic gastropods have gills located in the mantle cavity. The mantle of terrestrial gastropods functions as a lung.<\/p>\n<h2>Bivalves\u2014Clams and relatives (Class: Bivalvia)<\/h2>\n<p>Bivalves have two shells (valves) held closed by powerful muscles. The shell is produced by the underlying mantle; it grows along the outer margins.\u00a0They use their foot for burrowing. Mussels use their foot for the production of threads for attachment.<\/p>\n<p>The gills are large because they are used for filter-feeding as well as respiration. Food is trapped by mucus on the gills and moved by cilia. Water enters and exits through siphons.<\/p>\n<p>Obtain a preserved clam for dissection and place it on a dissecting tray. Remove one of the <strong>valves<\/strong> (shells) by inserting a scalpel and cutting the adductor muscles on each side of the hinge. See the diagram below for the location of the <strong>adductor muscles<\/strong>.<\/p>\n<div id=\"attachment_398\" style=\"width: 510px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-398\" class=\"wp-image-398\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles.jpg\" alt=\"Figure 3. Adductor muscles of a clam.\" width=\"500\" height=\"334\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles.jpg 640w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles-300x200.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles-65x43.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles-225x150.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/adductor_muscles-350x234.jpg 350w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p id=\"caption-attachment-398\" class=\"wp-caption-text\">Figure 4. Adductor muscles of a clam.<\/p>\n<\/div>\n<div id=\"attachment_399\" style=\"width: 1034px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-399\" class=\"wp-image-399 size-large\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-1024x397.jpg\" alt=\"cuttingmuscles\" width=\"1024\" height=\"397\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-1024x397.jpg 1024w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-300x116.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-65x25.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-225x87.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/cuttingmuscles-350x136.jpg 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<p id=\"caption-attachment-399\" class=\"wp-caption-text\">Figure 5. The anterior and posterior adductor muscles being cut so that the valves can be pulled apart.<\/p>\n<\/div>\n<p>The <strong>mantle<\/strong> is a membrane that surrounds the internal structures and is characteristic of all mollusks. The portion of the mantle from the exposed surface may have remained attached to the valve that was removed or it may be covering the internal structures. Find the mantle and if necessary, remove it to expose the internal structures of the clam.<\/p>\n<p>Identify the foot, visceral mass, gills, and labial palps. The gills are large because they are used for filter-feeding as well as respiration. Food is trapped by mucus on the gills and moved by cilia to the mouth. Cilia on the labial palps also direct food and mucus to the mouth.<\/p>\n<div id=\"attachment_400\" style=\"width: 510px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-400\" class=\"wp-image-400\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3.jpg\" alt=\"Figure 5.\" width=\"500\" height=\"403\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3.jpg 590w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3-300x242.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3-65x52.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3-225x181.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/clam3-350x282.jpg 350w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p id=\"caption-attachment-400\" class=\"wp-caption-text\">Figure 6.<\/p>\n<\/div>\n<p>The heart can be found in the area dorsal to and slightly posterior to the visceral mass. The coelom of bivalves is reduced and\u00a0limited to the area surrounding the heart. Because the coelom is reduced, it is difficult to see the digestive organs. Cut through the visceral mass and identify the intestine.<\/p>\n<div id=\"attachment_401\" style=\"width: 510px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-401\" class=\"wp-image-401\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005.jpg\" alt=\"Figure 6.\" width=\"500\" height=\"375\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005.jpg 640w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005-300x225.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005-65x49.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005-225x169.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/img005-350x263.jpg 350w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p id=\"caption-attachment-401\" class=\"wp-caption-text\">Figure 7.<\/p>\n<\/div>\n<p>In the photograph below, the foot and visceral mass have been lifted so that the mouth can be seen. Notice the labial palps on either side of the mouth.<\/p>\n<div id=\"attachment_402\" style=\"width: 510px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-402\" class=\"wp-image-402\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures.jpg\" alt=\"Figure 7.\" width=\"500\" height=\"375\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures.jpg 640w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures-300x225.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures-65x49.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures-225x169.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/ClamInternalStructures-350x263.jpg 350w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p id=\"caption-attachment-402\" class=\"wp-caption-text\">Figure 8.<\/p>\n<\/div>\n<h2>Squid, Octopus, Nautilus, and Relatives (Class: Cephalopoda)<\/h2>\n<p>Cephalopods are predators and live in a marine environment.\u00a0A closed circulatory system allows them to move rapidly in pursuit of prey.\u00a0They move by jet propulsion; water in the mantle cavity is squirted rapidly through a siphon.\u00a0The foot has evolved into tentacles around head.\u00a0Cephalopods have a powerful beak-like structure to tear apart prey.\u00a0The sense organs of cephalopods are well developed.<\/p>\n<p>Mollusks are the simplest animals with eyes. Some mollusks have <i><b>lenses <\/b><\/i>and therefore are capable of forming clear images. The camera-type eyes of some cephalopods (squid, octopus) are capable of focusing and forming clear images. Cephalopods are fast-moving predators and well-developed camera-type eyes help them catch prey.<\/p>\n<p>Well-developed brains (especially in octopuses) give them a high learning capacity. Cephalopods can hide from enemies by releasing a dark colored fluid from ink sacs.<\/p>\n<h3>Shells<\/h3>\n<p>The shell of a nautilus encloses the animal. A squid&#8217;s shell is small and internal. Octopuses do not have shells. Examine representative cephalopods on display.<\/p>\n<div id=\"attachment_403\" style=\"width: 641px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-403\" class=\"wp-image-403 size-full\" src=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid.jpg\" alt=\"Figure 7. A Squid\" width=\"631\" height=\"259\" srcset=\"https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid.jpg 631w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid-300x123.jpg 300w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid-65x27.jpg 65w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid-225x92.jpg 225w, https:\/\/courses.lumenlearning.com\/tcc-biolab\/wp-content\/uploads\/sites\/4207\/2015\/07\/squid-350x144.jpg 350w\" sizes=\"auto, (max-width: 631px) 100vw, 631px\" \/><\/p>\n<p id=\"caption-attachment-403\" class=\"wp-caption-text\">Figure 9. A Squid<\/p>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-127\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Mollusks, Biology 102. <strong>Authored by<\/strong>: Michael J. Gregory, Ph.D.. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/b51ab7d9e5e1e7063dcb70cee5c33cf7f4b7bad8.googledrive.com\/host\/0Bx6hk6AUBHxDc2d4TDJZTFIyMGs\/files\/Bio%20102\/Bio%20102%20Laboratory\/Animal%20Diversity\/Lophotrochozoans\/Mollusks.html\">https:\/\/b51ab7d9e5e1e7063dcb70cee5c33cf7f4b7bad8.googledrive.com\/host\/0Bx6hk6AUBHxDc2d4TDJZTFIyMGs\/files\/Bio%20102\/Bio%20102%20Laboratory\/Animal%20Diversity\/Lophotrochozoans\/Mollusks.html<\/a>. <strong>Project<\/strong>: The Biology Web. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA: Attribution-NonCommercial-ShareAlike<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":74,"menu_order":4,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Mollusks, Biology 102\",\"author\":\"Michael J. 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