Phylum Cnidaria A highly diverse assemblage that includes jellyfish, sea anemonies, corals and hydras.

Characteristics of Cnidaria Diplobastic Metazoa (Ectoderm and Endoderm). Radialy Symmetrical. Specialized Cells Cnidocytes for Feeding. Two Body Types. 1) Polyp: Benthic. 2) Medusa: Pelagic.

CNIDARIA: HYDROZOA HYDRA SP. BUDDING FROM NEBRASKA LINCOLN: POLYP FORM

HYDRA SP. TOP VIEW

UPSIDEDOWN JELLYFISH: MEDUSA FORM Cassiopea frondosa

Tissue Layers Diploblastic = 2 germ layers mesoglea endoderm  gastrodermis ectoderm  epidermis mesoglea gelatinous matrix between the 2 layers gastrovascular cavity epidermis mesoglea gastrodermis

General Body Plan sac-like body (only 1 opening) Food and waste go in/out the same opening  no anus! water within GVC acts as a hydrostatic skeleton oral surface mouth gastrodermis Gastrovascular cavity mesoglea epidermis aboral surface

General Life Cycle

HYDRA SP. FEEDING A B C D

Nematocysts specialized stinging organelles found within cnidocytes (cells) cnidocytes are located in epidermis A cnidocyte with a nematocyst within it

Nematocysts nematocysts are like “mini-harpoons” cnidocil senses movement & acts like a “trigger” can inject poison, coil around prey, or be adhesive functions: - prey capture; defense nematocyst cnidocil cnidocyte Undischarged Discharged

Nematocyst Types

HYDRA SP. UNDISCHARGED STENOTELE NEMATOCYSTS

HYDRA SP. UNDISCHARGED AND DISCHARGED STENOTELE NEMATOCYSTS

HYDRA SP. UNDISCHARGED STENOTELE AND ATRICHOUS ISORHIZA NEMATOCYSTS

HYDRA SP. DISCHARGED STENOTELE AND ATRICHOUS ISORHIZA NEMATOCYSTS

Nematocyst Discharge

Biology Feeding Digestion Gas exchange & Excretion nematocysts within cnidocytes tentacles Digestion extracellular (in GVC) intracellular (by gastrodermal cells) incomplete system (no anus) Gas exchange & Excretion these systems are absent

Structure Nervous System Skeletal System nerve net (no central nervous system= no brain) sense organs statocysts (equilibrium organs) ocelli (photosensitive organs) Skeletal System Mesoglea; water in GVC acts as a hydrostatic skeleton, and some external skeletal system.

Reproduction Reproduction Asexual budding longitudinal fission

Reproduction Reproduction Sexual usually dioecious (separate sexes e.g. humans) monoecious (both male + female gonads in 1 individual) results in Planula larva

Phylum Cnidaria Class Hydrozoa: Freshwater and marine. Class Scyphozoa: Jellyfish, all marine. Class Anthozoa: Corals and Anemones, all marine. Class Cubozoa: Box jellyfish and Sea Wasps, all marine.

Class Hydrozoa medusa & polyp body forms Fire coral Millepora

Class Hydrozoa medusa & polyp body forms (medusa with velum) most are colonial  colonies are formed of individual zooids a single zooid

Class Hydrozoa many of these colonies show polymorphism  this is where there are several different types of polyps/zooid and each type is specialized for a different function e.g. gastrozooids = feeding polyps e.g. dactylzooids = defense polyps  all the zooids within a colony are genetically identical  these different zooids work together in the colony

Class Hydrozoa - a sessile colony showing polymorphism gonozooid                                         entire colony gastrozooid

Class Hydrozoa - a Portuguese Man-o-war (Physalia) is a floating hydrozoan colony showing polymorphism Float entire colony gastrozooid dactylzooid

Portuguese Man-o-war Victims

Fire coral victim!

Class Hydrozoa- life cycle sexual reproduction asexual reproduction

Class Hydrozoa No Medusa Stage Hydra is an example of a solitary, freshwater hydrozoan sexual reproduction No Medusa Stage asexual reproduction gonads bud

Class Hydrozoa Hydra is an example of a solitary, freshwater hydrozoan bud asexual reproduction

Great Plains Hydrozoans

Chlorohydra viridissima: The Green Hydra The green color arises from Chlorella-like unicellular algae each occupying a vacuole in the endodermal cells.

Hydra vulgaris The common Hydra

Craspedacusta sowerbii Velum

Lives predominantly as a polyp in small lakes, ponds, and old water filled quarries the medusa stage occurs during July-October.

Three ways of asexual reproduction #1) Polyp budding. #2) Non ciliated planulalike buds may be produced.

Three ways of asexual reproduction #3) Production of medusa buds.

Sexual Reproduction Asexual Reproduction

Polypodium hydriforme The most bizarre of the freshwater cnidarians and one of the most unusual species of ALL Cnidarians!!

Polypodium spends almost all of its pre-adult life as a parasite of Acipenseriform fishes.

LIFE CYCLE