BI 112 Coelomate Invertebrates Objectives of this lab:

(1) introduce students to the concept of coelom (2) learn key morphological characteristics of the higher invertebrate phyla and classes (3) Recognize local representatives

I PHYLUM MOLLUSCA (clams, chitons, snails & slug, squids & octopi)

A. GENERAL CHARACTERISTICS:

True coelom- a lined body cavity; but small in molluscs! surrounding just the heart & kidney

Mantle & Mantle Cavity. Fold in outer body wall that forms a cavity for digestive, respiratory, and repro. organs; also secretes shell

Foot- a muscular structure (belly of a snail; wedge of a clam, head/tentacles of a squid)

Radula- file-like rasp used for eating

Members of the phylum Mollusca) are often extremely dissimilar looking, making the molluscan body plan the most malleable in the animal kingdom. The success of most mollusc groups is in part due to a protective calcium carbonate shell set in a protein matrix. A thin, often muscular, fold of tissue called the mantle, which covers the visceral mass, secretes the shell. The typical molluscan shell is composed of a thin, outer proteinaceous layer termed the periostracum, 2) a thick, hard middle calcareous layer called the prismatic layer, and 3) a thin, innermost calcareous layer known as the nacreous layer or mother-of-pearl. The periostracum protects the prismatic layer from chemical weathering and the smooth nacreous layer prevents abrasions to the mantle. Pearls are formed by the secretion of nacre around trapped foreign particles, such as sand and parasites.

Most molluscs, including snails, cephalopods, and chitons have a band of teeth in their esophagus called a radula, which is connected to a cartilage-like mass (figure right). The teeth of the radula consist mainly of chitin, protein & CaCO3, which are coated with a thin coat of magnetite. The magnetite enables molluscs, particularly herbivorous snails, to rasp algal cells from rocky substrates with the least amount of wear to the teeth.

A. MOLLUSC DIVERSITY

1. CLASS POLYPLACOPHORA Many Plate Bearing

The polyplacophorans, or chitons (figure right), are a group of algae-feeding molluscs that are restricted to rocky, intertidal pools. Their most noticeable characteristic is the series of 7-8 plates, which are partially or almost completely embedded in the mantle tissue that secretes them.

2.. CLASS GASTROPODA

The class gastropoda includes the snails, limpets, sea slugs, and terrestrial slugs. The muscular foot (pod) is located on their ventral surface (belly-side=gastro) and is used for locomotion. Most are characterized by the 90-180o torsion or twisting of their visceral mass, such that their anus and reproductive organs are located near their head.

Many aquatic snails are prosobranchs=forward gilled with gills that are visible as feathery appendages in front of the shell (below left).

Pulmonate (lung) gastropods (above right) include many freshwater snails, and all terrestrial snails and slugs. The lung in pulmonates is actually a thin, highly vascularized mantle cavity. Air enters the mantle cavity through a single small opening (pneumostome; see demo of the large land snail, Helix).

3. CLASS BIVALVIA or PELYCOPODA Bivalves are distinguishable from other mollusc groups on the basis of their 1) hinged shell, the left and right sides (valves). Bivalves have a posteriorly situated ventral incurrent and dorsal excurrent siphon and anterio-ventrally projecting foot (figure above right). See the siphons in your live fingernail clams. Food particles are filtered out by the large gills. Once food particles have been extracted from incurrent water, they are passed by labial palps (mitten-like structures) into an internal mouth opening

a-*FAMILY UNIONIDAE COMMON FRESHWATER MUSSELS

foot

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You should be able to recognize unios; these include our most consipicuous local clams. In Harlow Lake we find Lampsilis silquoidea and Pyganodon grandis. Lampsilus has hinge teeth on the shell, while Pyganodon lacks these teeth (see if you can tell the difference from some shells on display. Most of the Unios are relatively long-lived (12-200 years), dioecious, and highly fecund (200,000-17 million young per breeding season!!!). The glochidium, a parasitic larval stage, is perhaps the most unique characteristic of unionids. Many species, such as those in Lampsilis and Pyganodon have hooked glochidia that clamp on to fish gills, where they encyst parastically for several months.

b-FAMILY SPHAERIIDAE FINGERNAIL CLAMS

Sphaeriids are short-lived (1-2 years) clams with cream-colored shells. Unlike the filter-feeding Unios, fingernail clams obtain most of their food by deposit feeding, a process, which involves stirring up sediment particles using the foot, followed by selective sorting of food particles using the labial palps. Select a few live clams (bucket from Harlow Creek) and place them in a shallow dish with sand bottom. Observe their movementsfingernail clams are notorious for their ability to quickly bury themselves beneath the sand or mud. Note the long siphons.

4. CLASS CEPHALOPODA HEAD FOOT The cephalopods include the Nautilus, squid, cuttlefish, and octopods. In cephalopods, the foot is modified to form the arms or tentacles. The shell has been reduced to a thin, proteinaceous internal support structure called the pen (see demo). However, the chambered Nautilus possesses a prominent shell (see demo), while the octopods have lost their shell altogether.

II. Phylum Annelida A. GENERAL CHARACTERISTICS The Annelids are characterized by a well-developed coelom and segmentation. Unlike the coelom in molluscs, which mainly surrounded the heart, the annelid coelom encompasses all the internal organs and runs the entire length of their bodies. Segmentation allows for some redundancy (back up systems) of parts; for example, 5 hearts and multiple nephridia (excretory organs). Segmentation is probably most important in allowing complex movements, such as peristaltic, undulating movements useful in burrowing. Two of the three classes of annelids (Polychaetes and Oligochaetes) also have setae (bristles) that are used in locomotion. B. ANNELID DIVERSITY

3 classes: see demos of these three groupsbe able to recognize common reps 3

Polychaetes (marine worms with many=poly bristles) Oligochaetes (earthworm and relatives, with few=oligo bristles) Hirudinea (leeches)

III Phylum ARTHROPODA A. General Characteristics Phylum Arthropoda means jointed appendages, a characteristic that makes these inverterbrates among the most versatile and successful of all animals, specialized for virtually every niche and occupation on the planet. The arthropods also carry the annelid characteristics of a well-developed coelom and segmentation. Jointed appendages probably arose separately in several ancestral groups, i.e. the arthropods are probably polyphyletic. Arthropoda is divided into four subphyla: Subphylum Chelicerata (fanged arthropods) Subphylum Crustacea (arthropods w/mandibles & branched appendages) Subphylum Hexapoda (insects, 6 legs, unbranched appendages) Subphylum Myriopoda (centipedes, millipedes) The purpose of this lab is to become familiar with (1) the characteristics and diversity of the four subphyla, and (2) local diversity of aquatic arthropods B. Diversity (bold-faced taxa will be emphasized and you should know scientific or common names indicated)

1. Subphylum Chelicerata (fanged arthropods) Class Arachnida (spiders, mites, harvestmen, scorpions) Class Merostomata (horseshoe crabs)

2. Subphylum Crustacea Class Branchiopoda

Order Cladocera (water flea) Class Maxillopoda

Order Copepoda (copepods) Order Cirripedia (barnacles)

Class Malacostraca Order Decapoda (crayfish, crab, shrimp, lobster)

Order Isopoda (pillbugs) Order Amphipoda (scud)

3. Subphylum Hexapoda (Insects) 4. Subphylum Myriopoda (centipedes, millipedes)

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Common Freshwater Arthropods A. Crustacea

1. Scud 2. water flea 3. copepod 4. ostracod 5. isopod

B. Chelicerata 1. water mite

C. Uniramate-Class Insecta 1. stonefly 2. mayfly

several families-try to identify which one you have 3. hellgrammites

fish flies, dobson flies, alder flies 4. caddisflies

a. green free-living b. webspinners c. case builder

5. dragonfly 6. damsel fly 7. water boatman 8. backswimmer 9. predaceous diving beetle 10. other aquatic beetles 11. Dipteran (flies, gnats, etc) larvae

crane fly black fly mosquito other Dipterans

12. water scorpion

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BI 112 Coelomate InvertebratesA. MOLLUSC DIVERSITY1. CLASS POLYPLACOPHORA Many Plate Bearing2.. CLASS GASTROPODA

3. CLASS BIVALVIA or PELYCOPODASphaeriids are short-lived (1-2 years) clams with cream-colored shells. Unlike the filter-feeding Unios, fingernail clams obtain most of their food by deposit feeding, a process, which involves stirring up sediment particles using the foot, followe...III Phylum ARTHROPODASubphylum Chelicerata (fanged arthropods)Subphylum Crustacea (arthropods w/mandibles & UbranchedU appendages)Subphylum Hexapoda (insects, 6 legs, unbranched appendages)Subphylum Myriopoda (centipedes, millipedes)Order Cladocera (water flea)Class MaxillopodaOrder Copepoda (copepods)Order Isopoda (pillbugs)Order Amphipoda (scud)Common Freshwater ArthropodsA. Crustacea