10/8/09

1

Invertebrates •  Animals without

backbones •  We’ll cover

characteristics of major phyla and some to class level (KPCOFGS)

•  We’ll also cover some natural history

•  Refer to your notes that I posted on-line!

•  Levels of complexity change (become more complex) as we move ‘up’ the evolutionary tree

•  ‘Ancient’ animals are no better or worse adapted than ‘more complex’ animals. Its all about survival.

Ctenophores here too

Lophophorates

• No real symmetry, associations of loosely aggregated cells - very simple!

• Coanocytes (flagellated), collar cells, allow for food intake and O2. Osculum is excurrent pore (can have several), pore cells intake water

• Skeleton Spicules (CaCO3, or SiO2), or spongin (household sponges)

• Ecology: sessile, benthic, filter feeder. Encrusting and upright, and boring

• Most are hermaphrodites: eggs and sperm (broadcast). Fertilization is internal. Also have asexual reproduction: budding, re-aggregation

Sponges: Porifera ‘pore bearer’

Sponges are Suspension Feeders Choanocytes or Collar cells - flagellated

food-trapping cells of a sponge that generate a current through the pores

10/8/09

2

Cnidaria •  Radial symmetry –  similar parts of the body are repeated around the

center. No front or back, No head •  Oral surface (mouth side) •  aboral surface (opposite of mouth side)

•  Two Body Forms –  Polyp -cylindrical and usually attached

•  Corals, •  Anemones •  many colonial hydroids

–  Medusa - umbrella-like swimming form •  upside-down polyp adapted for swimming

Polyp

Medusa

Feeding Polyps on colonial hydroid

Phylum Cnidaria •  Diverse forms: jellyfish, corals, anemones, sea fans etc.

Stinging cells = nematocysts •  Gastrovascular cavity digestion and absorbtion of

nutrients. Waste through mouth! Respiration occurs through diffusion.

•  Hydrostatic (water) skeleton •  Ecology: sessile and benthic, as well as free swimming

(planktonic). Filter feeders and predators. Some are colonial animals. (corals, sea fans, gorgonians, man-o-war). Some like man-o-war and by the wind sailors have sails to aid in movement!

Phylum Cnidaria •  Symbiosis is common with zooxanthellae: 95% of food

and formation of calcareous skeleton.

•  Sex: Two phase life cycle (polymorphism)=sessile polyp phase and mobile medusa phase. Sexual rep is usually by medusa (eggs and sperm by broadcast spawning, or internal fertilization). Polyp also undergoes asexual budding

Phylum Cnidaria •  Some have a two phase life cycle! Polyp and medusa

Phylum Cnidaria •  Some have a two phase life cycle! Polyp and medusa

Aurelia: one of ‘our’ Jellyfish (scyphozoan)

Stinging cells - unique to Cnidaria

Fluid filled capsule

•  Nematocysts discharge on contact and with other stimuli (e.g. fresh water!)

Nematocysts

10/8/09

3

Coral Polyp •  Zooxanthellae

–  photosynthetic dinoflagellates (Kingdom: Protista) that are adapted to live within corals.

Colonial cup coral, Orange Cup Coral, Brown Cup Coral

Phylum Cnidaria - Class Anthozoa

Phylum Cnidaria - Class Anthozoa

Metridium giganteum, Urticina lofotensis, Urticina piscivora

White plumed anemone, White spotted rose a., Fish eating anemone

Phylum: Ctenophora

•  Characteristics of Comb Jellies  About 100 species - more????  8 rows of ciliary combs (ctenes)  Bi-radial symmetry  Cilia beat continuously

•  Light is refracted off the cilia giving a prism-like color effect

 Respiration occurs at body surface  some have tentacles with sticky cells called

colloblasts used to capture prey  cells and tissues are organized into organs

(rudimentary)  simple Gut (single opening)

Phylum: Ctenophora •  Natural history of Comb Jellies

–  No segmentation; No circulatory system

–  length from a few mm (sea gooseberry) to 2 meters long (venus’s girdle)

–  Most are pelagic, Found in warm and cold oceans - many are deep sea and bioluminescent

–  Carnivores (e.g. eat fish larvae) –  Hermaphrodites – broadcast –  Lots we don’t know!

Phylum Platyhelminthes: flatworms

• As many as 20,000 species! • CNS, Brain (agg. Of nerve cells in head region).

Nerve cords and muscular system. • Many (such as flukes) are parasites (eg.

tapeworms – one is 40 feet long – in sperm whales)

• Bilateral • Organs and organ systems, nerves, brain, CNS,

muscles • No skeleton • Variety of functions (parasites, free living etc.) • Sexual, most have larval stage

10/8/09

4

Ph Nemertea (ribbon worms),� Ph Nematoda (roundworms)

Phylum Nematoda (roundworms) •  Bilateral symmetry •  dig tract, and true organs. •  Hydrostatic skeleton •  Huge #s in sediments, decomposers, parasites, •  Sexual reproduction with larvae. •  Can be seen in fish flesh!

Lophophorates: Lophophore=set of ciliated tentacles arranged in a horseshoe).

•  Suspension feeders, mostly colonial (individual zooids), live in area of low sedimentation

•  Bilateral •  Unsegmented, colonial. U shaped gut •  Exoskeleton of a variety of shapes •  Benthic filterfeeders •  Sexual and asexual.

•  Phylum Bryozoa: look like colonial hydrozoans. 4000 species, delicate colonies. Retractable lophophore. Zooids show task specialization.

Bryozoans (moss animals)

Phylum Annelida: segmented worms

•  bilateral •  Segmentation •  Gut cavity, complex movement and systems. Makes them

good crawlers and burrowers. •  2 Ventral nerve cords : peristaltic movement. Each

segment has ‘kidneys’ for nitrogenous waste, and parapodia with setae for movement.

•  Closed circulatory system. •  Have gills •  Hydrostatic skeleton - many have tubes etc! •  See ploychaeta: deposit feeders and suspension feeders:

active and passive, and carnivorous. Some crawl. •  Sexual. Trochophore larvae. often timed with phases of

moon.

10/8/09

5

Diopatra ornata Ornate Tube Worm

Phylum Annelida - Class Polychaeta

Class Polychaeta: most annelid species are here. 6,000 sp. Mostly marine. 5-10 cm long. Live singly or in aggregations. Build tubes made with lots of different things. Cilia and mucus aid in feeding.

Phylum Sipuncula (peanut worms).

• All marine. 350 sp, benthic. Most intertidal, few deep sea.

• Bilateral • Unsegmented. Can curl in to look like peanut.

Mouth and anus at same end • Hydrostatic • Burrows (open at one end). Calcarous tubes or

burrows. • Sexual: gametes released through temporary

gonads. External fertilization

Phylum Echiura: spoon worms. About 100 sp.

Fat innkeeper (Urechis Caupo). Burrow with commenal creatures in mud. Sweep detritus with proboscis and urechis uses a mucus net. Pumps water through burrow and through net. Close relatives of annelids.

Phylum Cheatognatha: arrow worms. Only about 100 sp.

• Bilateral • Unsegmented, flattened, quick movements, small

body (high SA/V ratio means they don’t have resp. circ or excret. Systems.). Cilia serve to notify them of movements in the water (like shark lateral line system)

• Hydrostatic • Predators, planktonic • Hermaphrodites

Phylum Mollusca •  Successful, more species of this phylum than any other in the

oceans. Diversity of shape and diversity of habitats that they inhabit is high.

•  110,000 species: second only to arthropods •  Soft bodied with a mantle that produces a shell (CaCo3) •  Unsegmented and bilateral symmetry •  Foot – ventral and muscular for locomotion •  Radula – ribbon of teeth for rasping, made of •  chitin. •  Separate mouth and anus •  Circulatory system – most open, cephalpods •  closed (Blood remains in vessels) •  Reproduction – dioecious and hermaphroditic,

–  most have trochophore larvae to veliger

Some are benthic, some are pelagic, and they live from the intertidal to the deep sea. Some are predators, some are herbivores (grazers), while still others are filter feeders.

10/8/09

6

•  Class Gastropoda – "stomach footed"– snails, ~ 90,000 species! Nudibranchs, limpets Feed with radula –rasping tongue, coiled shell (most), Graze, some are sessile, most are motile

•  Class Bivalvia – clams, mussels,oysters ~3000 species

2 shells, crystalline style (enzyme secretion), siphon, foot, gills, pearls laterally compressed, some burrow, bore, or

attach to hard substrate.

•  Class Cephalopoda – "head foot" ~600 species Siphon for jet propulsion, funnel, ink, pen, beak Active body plan of molluscs – octopuses – 8 arms, no shell, bottom and crevice dwellers, hunters – squid – 10 arms, 2 tentalcles, "pen", largest

invertebrate... – cuttlefish – 8 arms, 2 tentacles, cuttle bone

•  Class Polylacophora ~ – Chitons, 8 plate like shells, radula, foot ~600 sp

•  Phylum Arthropoda: ‘jointed leg’. 1 million species! (most numerous phylum). Includes the insects. Very successful phylum in terms of diversity of species and habitats they live in. They have an exoskeleton of chitin, and the molt their skeleton periodically (like snakes).

Subphylum Crustacea: 35,000 species, Includes the copepods, crabs, lobsters, krill, and barnacles.

•  Bilateral symmetry •  Segmented bodies. Paired appendages (jointed legs).

Dorsal (on the back) heart, and ventral (on the stomach) nerve cord. They (crustaceans) have a simple brain, and an open circulatory system.

•  Exoskeleton of chitin which they molt •  Some are planktonic (like copepods) while others are

benthic scavengers and predators (like shrimp and lobsters), and still others are filter feeders (like copepods).

•  They (crustaceans) have separate sexes. Male transfers sperm to female, and she holds the eggs. They have a planktonic nauplius larvae

•  Class Copepoda (oar foot): copepods. Small and planktonic. Major consumers of phytoplankton (mostly diatoms).

•  Class Decapoda (10 feet). Largest class. Crabs, shrimp and lobsters. All (even crabs) have a ‘tail’ like in the lobster. In the crab it is curled under. You can use it to sex a crab (in the male it is thin while in the female it is wide). Crabs have a high diversity of forms. Decapods are an important food source for humans.

•  Class Isopoda (equal feet): Pill bugs (terrestrial) and kelp isopods are examples of this class. Some are parasitic on fish gills. Others can be seen just above the high tide mark running like big pill bugs with large feet (they are actually marine – species ligia).

• Class Amphipoda (double feet): sand fleas, caprellids (you’ll see these later in our float lab), whale lice, and the little organisms that gray whales feed on are amphipods. They can occur in great numbers. Many (like the ones gray whales eat) are benthic and live in soft sediment. Laterally compressed bodies.

• Class Cirripedia (curled feet): barnacles. Sessile and hermaphroditic. They have the longest penis relative to body size of any animal on earth (over 6 times their body length!). Sessile, filter feed with their feet.

10/8/09

7

Cirripedia: barnacles Echinoderms - spiny skin •  Deuterostomes: Formation of the mouth

second in deuterostomes evolutionarily links echinoderms, hemichordates, and chordates. Primitive echinoderms and pterobranch hemichordates probably arose from an ancestral tentacled filter-feeder, which also gave rise to the chordate line.

Phylum Echinodermata •  ~ 6,000 species living from the intertidal to the very deep sea

•  Radial pentamerous (5 part) symmetry as adults •  Bilateral symmetry as larvae •  3 body cavities (coelomic cavities).

–  Water vascular system: tube feet –  Pedicellaria

•  Endoskeleton (CaCo3) •  Poor or absent circulatory system. •  Non-segmented •  Most are benthic as adults: filter feeders, grazers, scavengers,

detritivores, predators •  Most have separate sexes - broadcast and brood

Phylum Echinodermata •  Class Asteroidea (star-like): Sea stars (starfish).

About 1600 species. Some have as many as 50 arms! Stomach sticks out from body for external digestion. They can stick this stomach into a bivalve (clam) shell and begin digesting it!

•  Class Echinoidea (hedgehog like). Sea urchins and sand dollars, about 900 species. Very much like sea stars (in terms of body organization), but have no ‘arms’. In some urchins, the mouth (Aristotle’s lantern), is adapted for grazing on algae. Sand dollars live in soft sediment and filter feed with tube feet and move with their spines (opposite from other echinoderms).

Phylum Echinodermata

•  Class Ophiuroidea (snake form). Brittle stars and basket stars, about 2000 species. Their arms an wave and move like a snake. They use them for movement and filter feeding (the tube feet do the actual feeding).

•  Class Holothuroidea. Sea cucumbers. These lack actual spines, but have soft spiny projections. Many are eaten (there is quite a large fishery for them). There are about 1,100 species, and some are found very deep. They are filter feeders and deposit feeders (literally eat the mud or sand and digest organic matter out of it).

Figure 33.37 Anatomy of a sea star

10/8/09

8

Phylum Chordata • notochord –flexible rod support between nerve cord and gut

• Dorsal hollow nerve cord – forms from the ectoderm and rolls into a tube – dorsal to the notochord

• Pharyngeal slits – small opening at end of gut or pharynx (nearest to mouth).

• Muscular tail projecting beyond (posterior to) the anus

Phylum Chordata

Phylum Chordata Other characteristics:

•bilateral symmetry •Segmentation •three germ layers and a well-developed coelom. •ventral heart, with dorsal and ventral blood vessels and a closed circulatory system •complete digestive system •bony or cartilaginous endoskeleton usually present

SP Urohordata: tunicates, larvaceans, salps

•Cellulose tunic

•Mouth opens to a basket-like pharynx

•Pharyngeal gill slits

•Free swimming larval form

S.P Urochordata�

Class Larvacea � larvaceans