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Lab Notes: Invertebrate Phyla - Mollusca & Arthropoda, Lab Reports of Biology

These lab notes provide an overview of the phyla mollusca and arthropoda, including their key characteristics, major classes, and unique features. The document also includes instructions for identifying and examining various mollusk and arthropod specimens.

Typology: Lab Reports

Pre 2010

Uploaded on 12/15/2009

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BIO 1
Section 3
Dr. Pablo Delis
Student Name
11/5/09
Taxonomy and Morphology: Mollusca & Arthropoda
Objective:
Familiarize us with the diversity of invertebrate animals and some of the key
characteristics that define the structure of the phylogenetic tree
Will learn to recognize the major invertebrate phyla and understand the unique
characteristics of each group
Appreciate the diversity of these phyla and be able to identify them.
The lab instructs us to answer questions about each phylum, which are answered here:
Phylum Mollusca
1. Coelom
2. Open circulatory system
3. Muscular foot, mantle, shell, radula, gills
1. Polyplacophora- shell is eight-part
2. Gastropoda- large flat foot, one or two gills, mantle folded into secondary gills or
lungs
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pf4
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BIO 1

Section 3 Dr. Pablo Delis Student Name 11/5/

Taxonomy and Morphology: Mollusca & Arthropoda

Objective:

  • Familiarize us with the diversity of invertebrate animals and some of the key characteristics that define the structure of the phylogenetic tree
  • Will learn to recognize the major invertebrate phyla and understand the unique characteristics of each group
  • Appreciate the diversity of these phyla and be able to identify them. The lab instructs us to answer questions about each phylum, which are answered here: Phylum Mollusca
  1. Coelom
  2. Open circulatory system
  3. Muscular foot, mantle, shell, radula, gills
    1. Polyplacophora- shell is eight-part
    2. Gastropoda- large flat foot, one or two gills, mantle folded into secondary gills or lungs
  1. Bivalvia- body enclosed in a two-looped mantle resulting in a shell that has two lateral valves of variable size and form connected by a dorsal hinge, no radula, foot is wedge-shaped, gills are plate-like
  2. Cephalopoda- shell is reduced, internal, or absent; head with eyes and radula; foot is modified into arms or tentacles Phylum Arthropoda
  3. Coelom
  4. Open circulatory system
  5. Jointed appendages, metamerism, exoskeleton Phylum Mollusca
  • Includes approximately 50000 living species
  • Includes chitons, clams, oysters, snails, slugs, nudibranchs, squids, cuttlefish, and others
  • Triploblastic, exhibit cephalization and have a true coelom
  • All organ systems are represented
  • Muscular foot used in locomotion
  • A fold in the dorsal wall, mantle, encloses a mantle cavity which usually contains gills and secretes the exoskeleton or shell
  • Open circulatory system with pumping heart and a complete digestive system
  • Radula of the mouth may be in the form of a razor blade-like form used in scraping food from surfaces
  • Gills are plate-like
  • Sexes usually separate
  • Anodonta, Venus, Tagelus
  • Class Cephalopoda
  • Squids, octopuses, nautili
  • Shell reduced, internal, or absent
  • Head is well developed with eyes and radula
  • Foot is modified into arms and tentacles
  • Siphon is present
  • Sexes separate
  • Loligo, Octopus, Sepia
  • Examination of Mollusks
  • Examine and sketch radula of a snail
  • Mussel (or Clam) Dissection
  • Pairs of students obtain a preserved specimen of the freshwater mussel or clam
  • Perform dissection in dissection tray
  • Open bivalve by inserting scalpel or razor blade between the valves near the adductor muscles
  • Cut these muscles in order that the two valves can be separated
  • Do not destroy the softer organs within the valves
  • Place the mussel on your dissecting tray with the hinge side down while trying to cut the muscles
  • Identify the delicate mantle that secreted the calcium carbonate forming the shell and the paired gills
  • Identify the paired labial palps that are used to guide food into the mouth
  • Identify the visceral mass that contains most of the digestive organs, the intestine as it exits the visceral mass and the heart that wraps around the intestine in the dorsal region
  • Identify the muscular foot used in locomotion
  • Identify the anus, if possible
  • Examine the respiratory system
  • Water is circulated to the gills by way of an incurrent siphon that lies ventral to the excurrent siphon - Both siphons are in the posterior region
  • Make a sagittal cut through the visceral mass in order to view the digestive organs
  • Identify the esophagus that connects the mouth to the stomach, intestine, digestive glands, and gonads - Digestive glands produce and release digestive enzymes to the stomach and intestines - Digestive glands are greenish in color - Gonads are orangish in color
  • Identification of many mollusks can be made by only examining the shell
  • Exoskeleton with limy salts (calcium carbonate)
  • Biramous appendages
  • Head with two pairs of antennae
  • Numerous classes include decapods, microscopic aquatic forms, isopods, amphipods, etc
  • Subphylum Myriapoda
  • Centipedes and millipedes
  • All appendages are uniramous
  • One pair of antennae on the head
  • One pair of mandibles and one or two pairs of maxillae provide chewing mouthparts
  • Class Diplopoda
  • Millipedes
  • Body elongate and wormlike
  • Variable number of body segments (somites) usually with two pairs of legs per somite
  • Class Chilopoda
  • Centipedes
  • Elongated, dorso-centrally flattened body
  • Variable number of somites each with a single pair of legs
  • Subphylum Hexapoda
  • Insects, springtails, and relatives
  • Appendages and uniramous
  • One pair of antennae on the head
  • Mandibles and maxillae
  • Body with a distinct head, thorax, and abdomen
  • Thorax usually with three pairs of jointed legs and two pairs of wings
  • Class Insecta
    • Largest class of arthropods and the most successful group of animals that have ever lived; most have two pairs of wings on the abdomen
  • Examination of Arthropods
  • Subphylum Trilobita
  • Examine the pictures or fossil specimens of trilobites
  • Note the compound eyes, and be sure you can identify them to the subphylum
  • Subphylum Cheliceriformes
  • Class Merostomata
  • Horseshoe crab ( Limulus Polyphemus )
  • Not really crabs but members of an ancient group of chelicerates, the Merostomata, most of which are extinct
  • Marine bottom dwellers that feed on mollusks, worms, and algae
  • They come onto Atlantic and Gulf coastal beaches to breed in the spring
  • From a dorsal view, identify the exoskeleton, cephalothorax (that is covered by a carapace) and compound eyes
  • Examine the hard exoskeleton that consists of a cuticle that is hardened with an organic substance termed chitin and mineral salts consisting primarily of calcium carbonate
  • This exoskeleton must be shed periodically to accommodate growth
    • Ecdysis
  • The primary body segments are the cephalothorax and abdomen
  • Examine the carapace that covers the cephalothorax and note the anterior extension termed the rostrum
  • Two pairs of antennae and compound eyes are present in the head region
  • The first pair of antennae are subdivided to form antennules
  • Turn the crayfish over to reveal the five pairs of legs
  • The first pair of legs (chelipeds) are highly specialized in most to form pinching structures
  • The remaining four pairs of legs are walking legs
  • The mouthparts demonstrate second and third maxillipeds on the head region
  • Note the swimmerets on the underside of the abdomen
  • The first pair of swimmerets (gonopods) are longer in males for sperm transfer to females
  • All swimmerets are of equal size in females and are used to hold aerate eggs and crayfish larvae
  • The powerful muscles of the abdomen flex the broad tail that consists of a central telson and lateral uropods, thus providing a backward swimming motion
  • Note that the uropods, the swimmerets, and the antennules are all double- branched, or biramous