Basic biology and classification of marine invertebrates

-Metazoan animal origins: 700 million to 1.4 billion ybp -Cambrian explosion: 600 mybp -evolution is not progressive, no increase in complexity after origination of phyla -many body plans are no longer around -What caused the dramatic radiation of metazoans?

Burgess shale fossil quarry in the Canadian Rockies

Some major phyla of marine invertebrates Poriferasponges Cnidariajellyfish, anemones, corals Annelidasegmented worms (e.g. polychates) Molluscaclams, mussels, octopus, squid Bryozoabryozoans Arthropodacrabs, shrimp, copepods, Echinodermataurchins, holothuroids, sea stars Urochordataascidians/tunicates You should know the phyla and examples and general characteristics of animals in each

Some basic terms: Benthic vs. Pelagic Sessile vs. Mobile Solitary vs. Colonial Sexual vs. Asexual Encrusting vs. Upright Autotrophic, Chemoautotrophic, Heterotrophic Predation, Herbivory, Omnivory, Primary production

Phylum: Porifera: Sponges -simplest multicellular animals, but not ancestral! -no true tissues -cells are independent and perform specialized functions -very efficient filter feeders -good spatial competitors -incurrent and excurrent canals -asymmetrical

Sponge anatomy-built around a system of pores, chambers, and canals -choanocyte -spicules

Phylum Cnidariajellyfish, anemones, corals What makes something a Cnidarian? -all are aquatic -tissues present but no organs -2 basic shapes or phases: polyp & medusa -nematocyst -tentacles -1 opening

Phylum Cnidariajellyfish, anemones, corals Physalia: man-o-war Cassiopia

Phylum Cnidariajellyfish, anemones, corals Hydroid Sea Pen

Phylum Cnidariajellyfish, anemones, corals Colonial reef coral Solitary reef coral Sea fan Anemone

Phylum Annelida Class Polychaetasegmented marine worms 6000 species Segmentation Setae A variety of feeding modes: Active predators, mucus bag feeders, mud-munchers and passive filter feeders Fire worm

Feather duster worm Christmas tree worm -serpulids: secrete CaCo3 shell -filter feeders

Phylum Mollusca Class Gastropoda: snails and limpets Class Polyplacophora chitons Cyphoma Cassis -second most diverse marine animal phyla (100,000+ species) -no segmentation -have complete gut -usually have a calcareous shell

Phylum Mollusca Class Gastropoda: snails and limpets Cone shell Conus geographus “mini melo” -many predatory snails are highly specialized

Bivalves: clams, oysters, mussels, scallops Phylum Mollusca Tridacna Giant Clam -some have autotrophic symbionts -most are active filter feeders

Cephalopods:octopods, squid, nautilus Phylum Mollusca Octopus-8 arms Squid-8 arms + 2 longer tentacles

Nudibranchs:sea slugs Phylum Mollusca Aplysia Sea Hare -most are specialized predators

Phylum Bryozoa:bryozoans -passive filter feeders -colonial -zoids

PhylumArthropoda SubphylumTrilobita SubphylumCheliceratahorseshoe crabs, sea spiders SubphylumCrustaeacrabs, shrimp, barnacles, copepods SubphylumUniramiainsects -by far the largest animal phylum -could represent several independent phyla -mono vs. polyphyletic -all are segmented, but segments are divided into different body regions -appendages are paired and jointed -all have an external skeleton -probably derived from annelids

PhylumArthropoda SubphylumCheliceratahorseshoe crabs, sea spiders

PhylumArthropoda SubphylumCrustaeacrabs, shrimp, barnacles, copepods

Blue crab Barnacles (goose neck)

Phylum Echinodermata Sea stars -radial symmetry

Phylum Echinodermata Diadema Pencil urchin Sand dollar

Phylum Echinodermata Ophioroids (brittle stars) Crinoids

Phylum Echinodermata Holothuroids Sea cucumbers

Urochordataascidians/tunicates