Lecture 24 Ecdysozoa & Intro to Anthropoda Flashcards
what three clades does clade Bilatera have?
- Lophotrochozoa, Ecdysozoa, Deuterstomia
what are characteristics of the ecdysozoan clade?
- mot species-rich animal group
- covered by a tough exoskeleton called a cuticle
- shed their cuticle via ecdysis
- two largest phyla are: nematodes and anthropods
what is a cuticle?
non-living outer layer outside of epidermis
shed in moulting
what is below the cuticle?
the epidermis
what is the epidermis?
living cells that secrete substances (ie the cuticle)
what are the 3 layers of the cuticle
endocuticle
exocuticle
epicuticle
what is the epicuticle?
layer of waxes – top of the cuticle
what does moulting of the cuticle allow?
- increase in size in a step-wise manner
- provides muscular support and acts as a protective shield
what does moulting of the cuticle allow?
- increase in size in a step-wise manner
- provides muscular support and acts as a protective shield
what is the cuticle composed of?
chitin – long chain polymer of glucose-derived units,
in anthropods, the cuticle is frequently sclerotized
sclerites when shaped like plates
what are the 11 steps of moulting?
- apolysis - epidermis separates from cuticle
what are the 11 steps of moulting?
- apolysis - epidermis separates from cuticle
- inactive moulting fluid is secreted into the space
- cell proliferation and enlargement increases the surface area (folds) of the epidermis
what are the 11 steps of moulting?
- apolysis - epidermis separates from cuticle
- inactive moulting fluid is secreted into the space
- cell proliferation and enlargement increases the surface area (folds) of the epidermis
- thin protective layer is deposited between moulting fluid and epidermis
- enzymes in the moulting fluid are activated – endocuticle is digested, liquified products are absorbed by the epidermis, scerized cuticle is not digested
- at the same time, a new undifferentiated layer of cuticle is deposited beneath the protective layer
- moulting fluid is reabsorbed
- epicuticle (wax layer) is reabsorbed
- old exocuticle and epicuticle is moulted via ecdysis
- new cuticle expanded
- outside of new cuticle is sclerotized by secretions via ducts
what is phylum tardigrada?
ecdysozoa - water bears or moss piglets
- very small
- four pairs of claw-tipped lobopods
- rounded shape, stubby appendages, lumbering bear liek gait
- no antennae
- no gas exchange system
- harsh conditions cause tardigrades to enter a state of dormancy
what is phylum nematoda?
ecdysozoa – roundworms or threadworms
- found in aquatic habitats, soil, moist plant tissues, body fluids and tissues of animals
- morphologically similar: no segmentation, appendages, eyes; have an alimentary canal; lack a circulatory system; slightly pointy one end, blunt the other; moult
- pseudocoelomate
- usually sexually reproduction, 2 sexes, some hermaphrodites
- internal fertilization
- direct development
- eutelic: post-embryonic growth occurs by each cell growing in size, not by addition of cells
- move side to side by contraction of longitudinal body wall muscles
- many parasitic
- medically important
