Chapter 15: Invertebrate Dissections

Flashcards from Chapter 15 of the Integrated Principles of Biology 1 Lab Manual.

Dorsal side

The darker, “top” side of the earthworm

Ventral side

The lighter, “bottom” side of the earthworm

Metamers

The series of segments that compose the body of the earthworm

Prostomium

The small projection at the anterior end of the earthworm, covering the mouth

• Is not a true segment

Perostomium

The first true segment of the earthworm, surrounding the mouth and prostomium

Anus

The last segment at the posterior end of the earthworm

Chaetae

Bristlelike protrusions on the body of the earthworm that provide traction to the earthworm

Nephridiopores

Openings that exist on each segment of the earthworm found anterior to the ventral setae, excreting waste taken up by the nephridia from the coelomic cavity

Nephridia

Excretory organs in the earthworm that excrete waste products through nephridiopores in the body wall

Intestine

Where the food passes through in an earthworm, lined by an absorbant tryphlosole and blood vessels

Dorsal pore

These exist on every segment of the earthworm posterior to segment 10, opening directly from the coelom near the folds between segments

• These exude coelomic fluid during dessication

Oviducts

Openings that pass eggs from the earthworm on the ventral side of segment 14

Seminal receptacles

These exist on the lateral surface near the folds between segments 9, 10, and 11

Clitellum

The swollen series of segments containing large glands and functioning in reproduction

• Releases a tube of mucus a few days after copulation that slides off the earthworm’s body and collects eggs and sperm to be left into the soil, where fertilization finally occurs after sealing to complete one worm

• Can be used to identify the anterior end

Genital setae

Protrusions on the ventral surface of segment 15 that clasp two earthworms together during mating

Peristalsis

How an earthworm moves, through the combination of longitudinal and circular body muscles acting on the fluid-filled coelom

Cuticle

This covers the earthworm's body, forming a layer made up of the polysaccharide chitin which is secreted by the secreting and sensory epidermis

Coelom

The fluid-filled body cavity in earthworms, surrounded by circular and longitudinal muscles and lined by a membranous peritoneum

• Divided into segments by septa

Hydrostatic skeleton

This is comprised of the body wall and coelom, providing peristaltic locomotion through circular and longitudinal muscular contractions

Esophagus

A passageway for what the earthworm has consumed as food, joined to the pharynx

• Surrounded by esophageal glands, absorbing excess calcium from the blood

• Enlarges at the posterior end to form the crop, as temporary storage

Crop

Where food is temporarily stored in the earthworm, after passing through the esophagus, before opening into the muscularized gizzard

Gizzard

A highly muscularized part of the earthworm’s digestive system, where food is ground up with the aid of soil particles

Seminal vesicles

Lobes within the earthworm’s sperm reservoirs that secrete fluid during reproduction

Seminal receptacles

Two pairs of openings on the earthworm’s body in segments 9 and 10 that receive sperm during fertilization

• Serves to complete the female organs in earthworms, alongside the ovaries and oviducts

Copulation

A mutual exchange of sperm between two earthworms, where:

• Ventral surfaces and anterior ends of the earthworms come in opposite directions

• Mucus is secreted by the clitellum and adhered to by chaetae

• Sperm is released from the openings and released into the seminal receptacles of the other worm, requiring 2 to 3 hours

Suprapharyngeal ganglia

Two swellings at the anterior end of the earthworm that function as primitive brains, attached to the ventral nerve cord and nerves for movement and control

Exoskeleton

The hard, external covering of the crayfish made of chitin and calcium carbonate, secreted by the hypodermis

Chromatophores

Cells containing pigment granules in the hypodermis of a crayfish, enabling color adaptation

Cephalothorax

The term for the head and thorax of the crayfish

Carapace

The single piece of exoskeleton covering the cephalothorax dorsally and laterally

Rostrum

The termination of a crayfish’s head in a spiny, pointed projection

• Has several sensory organs close to it

Antennules

Located in front of the stalked, movable eyes, these act as balance organs using either gravity or a magnetic field

Antennae

Chemoreceptors located next to the antennules of the crayfish

Maxillipeds

Appendages surrounding the mouth of the crayfish that sometime bear gills and function in tearing food apart before being passed to the mandibles

Mandibles

Appendages located beneath the maxillipeds, rolling food into the mouth and holding food torn by the maxillipeds

Chelipeds

The pincers of the crayfish, used for defense and predatory feeding

Periopods

The four pairs of walking legs in a crayfish, used for cleaning the body, handling food, and walking

Swimmerets

These are enlarged on male crayfish for sperm transfer; in females, they are elongated for carrying eggs except the first pair is reduced

Uropods

The swimmerets on the last segment of each tailfish gender that are greatly enlarged and flattened, forming a wide tail fan with the telson attached to the anus

• Also are used in swimming

Green glands

The excretory organs of the crayfish, associated with the bladder and nephridiopores