Lecture 06 Major Protosome Clades

Two Major Protostome Clades

Lophotrochozoa and Ecdysozoa

Lophotrochozoa

A major protostome superphylum characterized by a lophophore, trochophore larval stage, spiral cleavage, and incremental growth.

Lophophore

A feeding structure with ciliated tentacles.

Trochophore

A larval stage found in Lophotrochozoans.

Spiral Cleavage

A pattern of embryonic cell division associated with Lophotrochozoa.

Lophotrochozoan Growth

Lophotrochozoans grow incrementally.

Major Lophotrochozoan Phyla

Rotifera, Platyhelminthes, Annelida, and Mollusca.

Rotifera (Rotifers)

Small aquatic animals that feed and move using cilia.

Rotifers as Bioindicators

Rotifers can be used as bioindicators for water quality.

Platyhelminthes (Flatworms)

Flatworms with a flat body plan and no coelom.

Flatworm Body Plan

The flat body provides a large surface area for gas exchange.

Four Main Platyhelminthes Lineages

Turbellaria, Cestoda, Trematoda, and Monogenea.

Turbellaria

A flatworm lineage with a blind digestive tract.

Cestoda

Endoparasitic flatworms associated with undercooked meat and complex life cycles.

Trematoda

Obligate parasitic flatworms.

Monogenea

Endoparasitic worms that are hermaphroditic.

Hermaphroditic

Having both male and female reproductive organs.

Annelida

Segmented worms.

Parapodia

Appendages in annelids from which chaetae (bristles) stick out.

Chaetae

Bristles that stick out from the parapodia of annelids.

Three Annelid Lineages

Polychaeta, Oligochaeta, and Hirudinea.

Polychaeta

Highly mobile annelids.

Oligochaeta

Annelids with few bristles that help fertilize soils.

Hirudinea

Ectoparasitic annelids that are fluid feeders.

Mollusca

A Lophotrochozoan phylum with a general body plan consisting of a foot, visceral mass, and mantle.

Foot in Mollusks

Used for locomotion.

Visceral Mass in Mollusks

Contains the internal organs and gills.

Mantle in Mollusks

Secretes the shell.

Four Main Mollusk Lineages

Bivalvia, Gastropods, Cephalopoda, and Polyplacophora.

Bivalvia

Suspension feeders with two shells connected by a hinge; includes clams and scallops.

Gastropods

Mollusks with a coiled shell or loss of the external shell; includes snails and slugs.

Cephalopoda

Mollusks with tentacles, an evolved beak, and jet propulsion for locomotion; includes squid and octopuses.

Polyplacophora

Mollusks such as chitons; associated with a muscular hydrostat.

Ecdysozoa

A major protostome superphylum that grows intermittently through ecdysis (molting).

Ecdysis

Molting; the process through which Ecdysozoans grow intermittently.

Major Ecdysozoan Phyla

Nematoda, Tardigrada, Onychophora, and Arthropoda.

Nematoda (Roundworms)

Roundworms with an elastic cuticle; can be free-living or parasitic.

Tardigrada (Water Bears)

Very tough organisms that are fluid feeders.

Onychophora (Velvet Worms)

Nocturnal predators that use sticky slime.

Onychophora Body Plan

Have a hydrostatic skeleton and lobe-like limbs.

Arthropoda

Arthropods with an exoskeleton made from chitin, a segmented body plan, and jointed appendages.

Arthropod Exoskeleton

Made from chitin.

Tagmata

Specialized body regions formed from segments in arthropods.

Major Arthropod Subphyla

Myriapoda, Chelicerata, Crustacea, and Hexapoda.

Myriapoda

Arthropods with a long trunk of segments and a metachronal gait.

Metachronal Gait

A coordinated pattern of leg movement found in Myriapoda.

Chelicerata

Arthropods with two tagmata, no antennae, and chelicerae.

Chelicerae

Specialized appendages found in Chelicerata.

Crustacea

Arthropods with two sets of antennae, a shell-like carapace, and lots of body-plan diversity; includes crabs.

Carapace

A shell-like covering found in crustaceans.

Hexapoda

Arthropods with 6 legs, one pair of antennae, 3 tagmata, and compound eyes.

Two Main Forms of Metamorphosis

Incomplete metamorphosis and complete metamorphosis.

Incomplete Metamorphosis

Direct development where juveniles look like small versions of adults.

Complete Metamorphosis

Indirect development with distinct developmental stages.

Powered Flight

Insects were the first animals to evolve wings.

Origin of Insect Wings

Insect wings are not derived limbs; they are cuticle extensions from the thorax.