10/ Phylum Nematoda (Roundworms) Flashcards
Is a large group with 25,000 recorded species (but possibly around 50,000).
Phylum Nematoda (roundworms)
The focus of this subject will be more on the common parasitic species of man and animals.
Phylum Nematoda (roundworms)
Under phylum that contains a mix both free-living
and parasitic members, classifications will not be included and the parasitic forms will be arranged by type.
Nematoda
(nematos) means=
'’threads”
Organs are organized enough to form organ-systems.
Organ-system grade
Level of complexity of Phylum Nematoda
Organ-system grade
Phylum Nematoda includes:
Free-living and parasites
Most important parasitic group: causes economic loss in animal and plant-based livelihoods.
Phylum Nematoda
Phylum Nematoda has a _____ shape?
Cylindrical
Phylum Nematoda has lack of?
Lack of motile cilia or flagella (except in one species)
Phylum Nematoda has an embryonic cell layer of?
Triploblastic
Anatomy and Physiology of a Nematode:
Epidermis
Muscles
Body cavity
Digestion
Nervous System
Reproduction
Thick, noncellular outer
covering made of collagen
o Comes in several layers
o Shed during growth stages
o Has high turgor (strong and
rigid, but flexible) – protects the
worm from hostile environments
Cuticle
The underlying
epidermis (also made on syncytial
tegument) that secretes the cuticle
Hypodermis
Epidermis:
Cuticle
Hypodermis
Complex; Looks more like nerve cells, with the processes contain contractile fibers (actin and myosin)
Muscles
Lie beneath the hypodermis.
Muscles
Only contract longitudinally, meaning the worm body can lengthen, shorten, and move in a
whip-like manner.
Muscles
The lack of circular muscle fibers means the worm body cannot increase/decrease its diameter.
Muscles
Body cavity:
Pseudocoelomate
Has a body cavity containing the organs, but does not have a structure called the peritoneum which holds organs in place.
Pseudocoelomate
Pseudocoelomate – has a body cavity containing the organs, but does not have a structure called the ________- which holds
organs in place.
peritoneum
(pseudo) means=
“false/fake”
Gut is complete: consists of a mouth, muscular pharynx, long non-muscular intestine, short rectum, and anus.
Digestion
Food is sucked into the mouth by contraction of the strong muscles of the pharynx and then pushed down when the muscles relax.
Digestion
Intestines is one cell-layer thick and has no muscles, so food matter can only move through intestine by body movements and by additional food being passed into the intestines.
Digestion
Digestion is intracellular by phagocytosis of.
gastrodermal cells
Is intracellular by phagocytosis of gastrodermal cells
Digestion
Nervous System:
Sensory Papillae
Amphids
Phasmids
Is a ring of nerve tissue and ganglia around the pharynx, which then gives rise to
2 nerve cords (ventral and dorsal nerve cord) that send signals to the rest of the body.
“primitive brain”
Found around head and tail
Sensory papillae
Pair of complex sensory organs that open on each
side of the head, which enters into a pore with dendrites.
Amphids
Reduced in parasitic nematodes
Amphids
Similar to amphids but found in posterior end only found in parasitic nematodes.
Phasmids
Reproduction:
Copulatory spicules