Chapter 33: Invertebrates (Nematodes and Arthropods)Clinical applications in horseshoe crabs

Their blood cells can be used to quantify and detect bacterial endotoxins, used to check for contamination in vaccines

Clinical applications in horseshoe crabs

*Limulus* amoebocyte lysate (LAL)

Aspect of horseshoe crab blood cells that detect contamination

Ecdysozoan

Group of animals that shed a cuticle via ecdysis, consist of nematodes and arthropods

Cuticle

Tough external coat

Ecdysis

Molting

Phylum Nematoda

Most ubiquitous of all animals; covered by cuticle and has a hemocoel, doesn’t have a circulatory system

Ubiquitous

Found everywhere

Caenorhabditis elegans (C. elegans)

Well-studied model organism in biological research, roundworm

Trichinella spiralis

Roundworm that causes trichinosis, obtained through raw/undercooked meat; worm forces muscle tissue to become more elastic and produce more blood vessels

Phylum Arthropoda

Most successful animal phyla, consist of arthropods; have body covered entirely by cuticle made of chitin (exoskeleton)

Arthropod

segmented Ecdysozoan with a hard exoskeleton and jointed appendages

Chitin

Chain of proteins utilized by arthropods to form their cuticle

Caveats of exoskeleton

It prevents growth and ecdysis of it is energetically expensive and leaves organisms vulnerable

Closed Circulatory system

Circulatory system where blood is contained in vessels and has a predetermined path

Open Circulatory system

Circulatory system where blood flows and mixes freely throughout the body, not conducted through vessels

Hemolymph

Analogous to human blood, utilized in open circulatory systems

Hemocoel

Body cavity that surrounds tissues and organs

Clade Chelicerata

Lower classification of Phylum Arthropoda; consist of organisms that have chelicerae and lack antennae

Chelicerae

Claw like feeding appendages that serve as pincers or fangs

Eurypterids

Earliest species of Chelicerata, sea scorpions

Arachnids

Bulk of Chelicerata, have 6 pairs appendages, chelicerae, and pedipalps; spiders and scorpions

Pedipalps

Specialized limbs utilized in sensing, feeding, defense, and reproduction

Spinnerets

Specialized organ that makes silk

Clade Myriapoda

Lower classification of Arthropoda; Millipedes and centipedes, all are terrestrial; have a pair of antennae and 2 pairs of appendages modified as mouthparts

Millipede

“Thousand” legs, eat decaying leaves and plant matter; friendly :)

Centipede

“Hundred” legs, carnivores with poison claws; not friendly :(

Carnivore

Organism that consumes other living organisms (not plants)

Clade Pancrustacea

Lower classification of Arthropoda “all” crustacea; consist of crustaceans and insects

Isopod

Largest group of clade pancrustacea, morphologically diverse with flattened body; Pill bug!

Decapod

Group of Pancrustacea; ten legs and cuticles made of calcium carbonate, most are marine, crabs!

Copepod

Group of pancrustacea; Small crustaceans found in nearly all fresh/saltwater habitats, most numerous; krill!

Barnacles

Group of pancrustacea; Sessile with cuticle of calcium carbonate forming a shell, anchor to stationary marine structures and feed through extending appendages

Dorsal

Top side of thorax

Thorax

Area of an insects body between the head and abdomen

Incomplete metamorphosis

Young resemble adults but smaller and lacking wings, multiple molts to achieve adult size

Complete metamorphosis

Consist of larval stages specialized to feeding and growing and different looking adult stages dedicated to dispersal and reproduction

African sleeping sickness

Sickness caused by organism carried by flies

Tsetse fly

Fly that carries *Trypanosoma*

Trypanosoma spp.

Organism that causes African sleeping sickness

Malaria

Disease carried by mosquitoes

Mosquito

Insect that carries Malaria

Plasmodium spp

Organism that causes malaria

Thomas Eisner

Who said “Bugs are not going to inherit the earth. They own it now. So, we might as well make peace with the landlord”?

They are huge pollinators and food source for other organisms

What are some of the reasons that we should care about insects

They compete with us for food and cause disease

What are some of the reasons that we should not care about insects

Arthropoda

What is the most diverse phylum on planet earth

Mollusca

What is the second most diverse phylum on planet earth