exam 2 inverts

What is the habitat and ecological role of Cnidaria

are aquatic, both marine and freshwater

sessile or weakly swimming

all carnivorous predators

many have symbiotic unicellular algae

critical role in hermatypic (reef-buillding corals)

can supply 80% of nutritional needs and be required for the formation of the skeleton

What is the body plan of cnidarian

2 major morphological types: polyp and medusa

radial symmetry

oral / aboral axis main body axis

gastrovascular cavity - gut with one opening

hydrostatic skeleton - muscles exert against fluid and is circular and longitudinal muscles

to gain height circular muscles contract and longitudinal muscles are relaxed and mouth has to be closed

What are the layers of cnidarians

epidermis, mesoglea, gastrodermis

What are the principles cell types of the epidermis

epitheliomuscular cells : provide covering and form longitudinal muscle

interstitial cells: pluripotent cells

muscus secreting cells

sensory and nerve cells

cnidocytes: characteristic cells of cnidarians, contain special organelles called cnidae.

What are some categories of nematocyst-type cnidae

Penetrant

• Penetrate prey and inject a toxin (venom cocktail)

• toxin is a mixture of phenols and proteins

• may be neurotoxic, myotoxic, or necrotic

Adherent

• sticky tubules used for attachment

• assist in attaching prey to cnidarian tentacle

Volvent

• whiplike structures that coil around parts of prey and entrap

What is the feeding and nutrition of cnidarian

Prey is immobilized and adhered to tentacle

transferred to the gastrovascular cavity

then digested and remains regurgitated

What is the cnidarian nervous system and sense organs

nerve cells connect in a net-like arrangement

no cephalization

sensory structures may be present

• statocysts

• variable - simple photoreceptors, complex lensed eyes

Characteristics of Class Hydrozoa

solitary polyps or colonial polyps that also have medusae

polyps may have a supporting exoskeleton

• usually made of chitin, sometimes calcium carbonate

hydromedusae are small, have a velum and manubrium

gastrovascular cavity is a simple sac without pharynx or mesenteries

mesoglea acellular (no cells)

cnidae is epidermis only

aequorea - green fluorescent protein

What are hydroid colonies

form by repeated budding or polyps that stay connected

diverse colony morphology - depends on budding pattern

polyps are physiologically interdependent

• e.g., share a common gastrovascular cavity

Polyp types

• gastrozooid - feeding

• gonozooid - produce medusae by budding

• dactylozooid - defensive polyps

What is the life cycle a moon jelly

a colonial hydroid with both polyps and medusae

two kinds of polyps:

• gastrozooids and gonozooids

What is a tubularia life cycle

polyp with gonophores

gonophore produces ova which are fertilized in situ & develop into a planula

the planula develops into an actinula medusa is not released

What is an actinula

free swimming larva then settles and forms the first polyp of the next colony

What is a planula

has cilia, is multicellular, and is used for dispersal

Transdifferentiation

specified cells that can back track and become another specialized cell type

Characteristic of the Portuguese man o’war

sail using gas-filled float

long tentacles

large numbers of nematocysts

prey upon fish

Characteristics of Class Scyphozoa

true jellyfish (upside down jelly, moon jelly)

all marine

medusa stage predominates

polyps (scyphistoma) are small & inconspicuous

cnidae present in epidermis and gastrodermis

medusae are acraspedote (velum absent)

gonochoristic

Characteristics of Class Cubozoa

Box jellyfish or sea wasps

bell is square in cross section

velarium present → relatively fast swimmers

polyps produce medusae by metamorphosis

complex eyes - visual behaviors

painful stings

life cycles are poorly known

some species engage in copulation

Characteristics of Class Staurozoa

stalked jellyfish

attach via a stalked adhesive disk

8 tentacle-bearing arms

lack a velum

develop from a benthic, non-ciliated planula larva

planula develops into a stauropolyp which then becomes a stauromedusae

Characteristics of Class Anthozoa

sea anemones, sea fans, sea whips, sea pens, sea pansies, stony corals

polyps only

solitary or colonial (skeleton may be present)

usually reproduce both sexually and asexually (fission or pedal laceration)

all marine; hard substrates or burrowing (tube dwelling)

characteristics of subclass hexacorallia

tentacles of 6

sea anemones, true corals (stony corals)

living tissue is a thin layer that covers skeleton

Anthozoan polyps compared to hydrozoa

anthozoan have gastrovascular cavity with pharynx, mesenteries and provide surface area.

gonads present at the edge of mesenteries

What are acontial filaments that may be present

very long stringy at the base of the anemones

bear large number of nematocysts

predator defense

Reproduction in anthozoa: asexually

fission splits into two

pedal laceration

note copulation was observed in one species, some species brood their embryos

Anemone defense and aggression

acontial filaments

• numerous nematocysts

• extruded when anemone is harassed

acrorhagi

• aggressive organs: below tentacles (generally) (used against same species but are not clones; conspecifics which are genetically different)

• nematocysts

• toxins

Characteristics of subclass octocorallia, order pennatulacea

sea pens and sea pansies

8 tentacles

tentacles are pinnate

branched

Characteristics of sea fans (order gorgonacea)

complex supporting skeleton outer covering

axial rod

Characteristic of subclass ceriantipatharia

tube anemones

special cnidae that form a felt-like mat (tube)

Class myxozoa

~2000 species of obligate intracellular parasites

initially believed to be protozoans

Characteristics of Phylum Platyhelminthes

catenulida: simple pharynx, sac-like gut

rhabditophora: posess rhabdites, duogland adhesive system

turbellaria - free living, commensal, parasite

cestoda - tapeworms

monogenea - flukes

trematoda - flukes

Bilateria

bilateral symmetry

triploblastic

Nephrozoa

Organ system includes excretory structures

generally have a complete gut

Epithelium Ciliated

mucus glands: make slippery mucus to reduce friction

rhandoids / rhabidites: discharged from epidermis release substance that may affect prey

Duogland adhesive system: system for fast attachment and release from a surface

use the cilia for locomotion (ciliary gliding)

Turbellarian Locomotion

Ciliary gliding

undulatory swimming (wave-like)

What is the nutrition and feeding of platyhelminthes

incomplete gut (=g.v)

pharynx may be present and may be extended

scavengers and predators

Nervous system and sensory structures of platyhelminthes

ladder like nervous system

cephalization: defined head and sensory structure

anterior cerebral ganglion

longitudinal nerve cord

transverse connectives

sensory system

chemoreceptors : organic acids of decomposing animals

ocelli: single ocellus, simple eyes (detect light / dark)

statocysts

Protonephridia

drain fluid from the tissues

remove nitrogenous wastes

with excretion and osmoregulation

Excretion

removing toxic nitrogen containing substances

Osmoregulation

maintaining the correct balance of ions and water in cells/tissues

Reproduction

monoecious (= hermaphrodites) - simultaneous

reciprocal copulation common, not universal

hypodermic insemination may occur

penis fencing in one species

In females: forms ova, produces yolk, provides egg covering, gonopore present (not always)

In males: testes, penis

the female reproductive tract produces egg casing

development is usually direct, “hatching” is juvenile mini adult

indirect development may result in a Muller Larva. larval stage

Generalized anatomy of Molluscs

muscular foot to cling to substrate

shell

mantle: tissue that secretes the shell

mantle cavity: space between the mantle and dorsal foot

contains gills; may contain opening to reproductive system (gonopore), excretory system (metanephridia) nephridiopores

anus

sensory tissue osphradium

chemosensory

detects sediment in water

complete gut - radula W

What is the radula

feeding apparatus

used for scraping food materials

tucked in or out in the substrate

radula teeth (surface of tongue, chainsaw like with a lick like motion)

What is the body wall and shell of molluscs

pallial mantle

mantle lobes including

secretory (outer) - produces shell material

sensory (middle) - sensory structures

muscular (inner)

Characteristics of Polyplacophorans

Chitons

marine, rocky substrates

8 shell plates, mantle = girdle

herbivores that feed on algal films

radula teeth capped with magnetite

flexible with shell plates

complete gut anterior —> posterior

gills are paired ctenidia in mantle cavity

mantle cavity between foot and mantle

Class Gastropoda

snails, slugs, nudibranchs, sea hares

the largest group of molluscs present in most habitats

gastropods generally have

• a distinct head

• a shell that is a portable retreat

• torsion

Gastropod reproduction

many are gonochoristic

• spawning - fertilization occurs in water

• internal fertilization via copulation - complex reproductive systems, female tract may encase eggs in protective covering

some hermaphrodites

• sea hares, nudibranchs, sea slugs

Opisthobranchs

nudibranch

Class Bivalvia

2 shells hinged dorsally

adapted for burrowing in soft substrates

large mantle cavity; reduced head

gills used for gas exchange & food collection

Bivalve feeding

ciliated gill surfaces creat a water current through the mantle cavity

water enters via inhalent siphon and exits via exhalent siphon

particles settle on gill surfaces

ciliated tract carry particles ventrally to the gill margin & then anteriorly to the labial palps

labial palps sort particles

fine particles are moved to the mouth

dense particles are rejected - pseudofeces