Week 9 | Animalia 2 | Nematoda and Arthropoda

Nematoda apomorphies

• Aquatic, moist terrestrial, parasitic

• Bilateral, cephalization

• Complete gut, pseudocoelomate

• Triploblastic; nervous system w/o brain

• Hydrostatic skeleton

• Dioecious with internal fertilization

Ascaris characteristics

• Slender bodies, tapered at both ends and covered by a cuticle

• Common parasite of humans, pigs, and other mammals

• 15-40 cm (6-18 in)

• Eggs are eliminated in host feces - are highly resistant

• Ingest food/water contaminated with eggs from feces

• Eggs pass through stomach and hatch in small intestine. Larvae migrate through blood, exit circulation and enter respiratory tract - out trachea into throat, swallow and reinfect

Ascaris female cross-section

Ascaris male cross-section

Arthropoda apomorphies

• Aquatic, terrestrial (land/air), some parasitic

• Bilateral, cephalization

• Complete gut, coelomate (protostome)

• Triploblastic; nervous system w brain, excretory, open circulatory system, respiratory system

• Exoskeleton

• Dioecious, internal fertilization, metamorphosis, parthenogenic

Arthropoda characteristics

• >1M species; largest phylum on Earth

• Cuticle has become modified into a hard exoskeleton

• Are protostomes with segmented bodies that include one pair of legs per segment

• Mouthparts are modified appendages (arm/leg)

• Three body regions: head, thorax, abdomen

• Coelom filled with hemolymph connected to an open circulatory system

Hemolymph

A fluid equivalent to blood in most invertebrates, occupying the hemocoel

Class Insecta characteristics

• More than ¾ of arthropods

• Evolution of wings led to exploitation of new environment

• Complete/incomplete metamorphosis

Complete metamorphosis

The type of insect development that includes egg, larva, pupal, and adult stages, which differ greatly in morphology

Incomplete metamorphosis

Involves a gradual development where the nymph progressively resembles the adult form

Grasshopper external anatomy

• Thorax has 3 segments each with a pair of legs (segments 2 & 3 have wings)

• Spiracles

• One pair of compound eyes and three ocelli

• One pair of antennae

• Mouth includes one pair of mandibles

• Two pairs of maxillae (2nd pair fused = labium)

• Upper lip is the labrum, which covers the mandibles

Class crustacea characteristics

• 2 pairs of antennae

• Carapace

Open circulatory system

Where hemolymph (blood) mixes with interstitial fluid and directly bathes tissues

Spiracles

External openings found in arthropods that allow air or water to enter the respiratory system

Ocelli

Eyespots on insects

Tapered

To become progressively smaller toward one end

Parthenogenesis

A form of asexual reproduction where offspring develop from unfertilized eggs, meaning a female can produce offspring without the need for a male

Difference between male and female crayfish

The first set of swimmers in the male is larger than the rest