Lab 3 (Annelids and Echinoderms) Flashcards
What are the classes to the Phylum Annelida?
Class Polychaeta
Class Oligochaeta
Class Hirudinida
Explain the basics to the Phylum Annelida
- Have adapted to marine, freshwater and terrestrial habitats
- Usually elongate, worm like animals
- Cross section would reveal a roughly tubular shape and a well muscled body wall
- Segmented bodies
- Metamerism is taken ti an extreme, where the internal and external structures are repeated nearly identically in each metamere
- Their coeloms are divided by septae (formed from peritoneum), which isolate the metameres internally
- Between each pair of septae is a fluid filled compartment that generates hydrostatic pressure, which contributes to locomotion
- This advanced skeleton combined with well developed muscles, makes for animals very proficient in coordinated digging, creeping and swimming movements
What are metameres?
Repeated, homologous body segments
What is metamerism?
The repetition of the homologous body segments
Explain the basics to the class Polychaeta
- Clamworms
- Found only in oceans, living in burrows dug in sand or debris of shallow waters
- They are nocturnal, emerging from their burrows to hunt and prey on smaller organisms at night
What is the support of the clamworms?
- The entire body is covered in a thick cuticle, which offers structural support and protection from the environment
What is the feeding/digestion of the clamworms?
- Head is at the anterior end of the animal
- The head is comprised of two main regions
1) the posterior region of the head is the peristomium (Contains the mouth and lacks the appendages found on the segments of the trunk. At rest, the mouthparts are typically converted and not visible)
2) Posterior end the last segment is the anus - The chitinous jaws indicate that this animal is a predator
What is the sensory of the clamworms?
- The anterior region of the head is called the prostomium and can be recognized by the presence of numerous sensory structures
- The four eyes are small and dark coloured
- One pair of antennae is found at the anterior end of the prostomium, between the larger palps
- Long tentacles also line either side of the prostomium
- The antennae, tentacles and palps are used for touch and taste
- On the posterior end of the animal is a pair of cirri
- There are other sensory cirri on each of the appendages
What is the locomotion of the clamworms?
- Every segment anterior to the peristomium has a pair of bristly lobed appendages (these are called parapodia)
- As individual parapodia undergo circular motions one at a time in a wave like fashion down the length of the body, the clam worms moves forward
- The entire body is well muscled and can undulate (this increases the speed at which the animal moves)
- The distal end of each lobe of the parapodium is equipped with a bundle of hair like bristles or setae
- A thick long chitinous spine called an aciculum is deeply embedded in each lobe, reaching all the way to the muscular body wall at the proximal end
- The acicula provide structural and mechanical support for the parapodia; the muscles to which they are attached are responsible for thrusting the acicula outward as the animal moves
- Cirri on either side of the lobes, are tactile sensory structures
What is the respiration of the clamworms?
- The large combined surface area of the highly vascularized parapodia is where most gas exchange takes place
What is the reproduction of the clamworms?
- They are dioecious and reproduce sexually but externally
- Mature clamworms leave their burrows in swarms and release their gametes into the water
Explain the basics of the class oligochaeta
- Few setae
- Posses a structure called a clitellum
- Earthworms are common clitellates
- They are found in moist, rich soil
- Mostly nocturnal
- Forage for food at night
- Consume large amounts of soil, from which they extract nutrients from live and decaying plant material
What is the external (general) of the earthworms?
- A segmented and metameric animal
- Covered by a thick cuticle
- It is rounded on one side and slightly flattened on the other (the latter is the ventral side)
- First four segments at the anterior end comprise the head (the first is the peristomium)
- The last segment (at the posterior ) bears the anus
- Thickened, saddle like clitellum is closest to the anterior end
- In mature worms, this structure secretes egg capsules into which eggs are laid
What is the peristomium?
It contains the mouth, just like that of the Polychaeta
What is the feeding/digestion of the earthworms?
- From the mouth (buccal cavity), food enters a thick, muscular pharynx and then moves into the esophagus
- Food then passes into a large, thin walled crop (similar to a stomach) where it is stored before it is passed to the muscular gizzard.
- Physical digestion (grinding) of the food takes place within the gizzard
- Ground up food is further digested and absorbed in the intestine (which runs posteriorly for the rest of the length of the body); solid waste is then finally passed out the anus
What is the excretion of the earthworms?
- Each side of the body wall of each segment also contains a nephridium
- Essentially it is a “mini kidney” that is involved in waste excretion
What is the circulatory/respiration of the earthworms?
- The esophagus is surrounded by the dark, circular aortic arches of the heart
- They have a closed circulatory system
- There are no respiratory organs; the slimy skin of the worm and its requirement for a damp environment are indications that it can diffuse oxygen and carbon dioxide directly through its skin into tiny capillaries underneath
- The dorsal vessel running along the top of the gut is muscular and is the main “pump” in the circulatory system
- The aortic arches of the heart ensure that blood flows into the ventral vessel and the capillaries on the ventral side
What is the circulatory/respiration of the earthworms?
- The esophagus is surrounded by the dark, circular aortic arches of the heart
- They have a closed circulatory system
- There are no respiratory organs; the slimy skin of the worm and its requirement for a damp environment are indications that it can diffuse oxygen and carbon dioxide directly through its skin into tiny capillaries underneath
- The dorsal vessel running along the top of the gut is muscular and is the main “pump” in the circulatory system
- The aortic arches of the heart ensure that blood flows into the ventral vessel and the capillaries on the ventral side
What is the reproduction of the earthworms?
- They are monoecious
- Cross fertilization occurs during copulation
- The male seminal vesicles (where sperm are stored and where they mature before copulation) are the most prominent reproductive organs and are found lying on either side of the esophagus
- The testes (where sperm is produced) are concealed inside the vesicles
- Lateral to and slightly beneath the anterior lobes of the seminal vesicles are 2 pairs of round seminal receptacles (these are female organs that store sperm after copulation)
- The ovaries (where eggs are produced) and the sperm ducts (through which sperm are voided from the body) are beneath the posterior lobes of the seminal vesicles
- During copulation, sperm are ejected from the sperm ducts of one animal and are taken up into the seminal receptacles of the other
- The clitellum secretes a cocoon, or egg case, which is slipped off the anterior end of the worm
- As the cocoon passes over the genital pores, eggs and sperm are released into it (fertilization occurs here)
- The cocoon is then deposited on the ground and the young hatch in a few weeks
What is the nervous/sensory of the earthworms?
- The ventral nerve cord lies below the intestine
- It runs the length of the body and connects to the cerebral ganglia in the head (found lying on top of the pharynx)
What is the movement/locomotion of the earthworms?
- The outer margins of the body are lined with two layers of muscle
- The outer layer consists of circular muscles that wrap around the body (contractions change the body’s circumference)
- Underneath, longitudinal muscles run from the head to tail (contractions shorten the body)
- Setae on the ventral surface of the animal grip the soil as it pulls itself forward
Explain the basics of the class hirudinida
- Leech
- Predaceous blood suckers that attach themselves to a host during feeding
- Freshwater animals (they feed on the blood of amphibians and mammals)
- Leech saliva contains anticoagulants that prevent blood form clotting and analgesics (that keep the host from being aware of its activity)
- Still used for medicinal purposes, such as to reduce blood in hematomas and promote blood flow at surgical sites
- They have segmented bodies
- Each segment is subdivided into 1 to 5 smaller segments called annuli
- The clitellum is only visible when the leech is fully reproductive (the pale segments on the upper portion of the body constitute the clitellum)
- The internal anatomy is similar to that of the earthworm
What is the feeding of the leeches?
- The anterior end possess the oral sucker, which bears the mouth
- the mouths of many species of leeches are equipped with numerous tiny sharp teeth to grasp the prey and promote blood flow
- The head bears many specialized sensory cells used to locate prey, including chemoreceptors and in many cases eye spots (ocelli)
What is the locomotion of the leeches?
- The posterior end end bears the caudal (tail) sucker
- The caudal sucker is not involved directly in feeding
- It helps anchor the animal and assists in locomotion
- To move, the oral sucker attaches and the body contracts
- the caudal sucker then attaches, and the body extends forward and the oral sucker attaches anew