Phylum Cnidaria (formerly Coelenterata) G: stinging thread bearing

The Hydra Powers of regeneration stem from omnipotent cells

Evolutionary Relationships

Phylum Cnidaria All have nematocysts (cnidae) Have radial symmetry 2 layers (epidermis and gastrodermis) Mesoglea between epidermis and gastrodemrmis is a non-living layer All have tentacles surrounding the mouth and only a single opening to the digestive system

Phylum Cnidaria Body Plan: medusa and polyp Planula larvae in the life cycle Have muscles and nerves Muscles are not true muscles— epitheliomuscular cells

Life Cycle of a Cnidaria

Cnidae Are organelles secreted from cnidoblasts or nematocysts Each cnida can be discharged only once Mechanism of expulsion currently unknown

Class Scyphozoa (Asexual reproduction by strobilation (budding)) The true jellies Monoecious Sperm+egg= planula Manubrium - muscular cylinder that ends in the mouth

Class Scyphozoa

Class Cubozoa (medusa w boxlike body; rhopalia with complex, lensed eyes) Box jellyfish/ seawasp (cubomedusae) Restricted to tropical and subtropical waters Most derived cnidarians Chironex fleckeri

Jellyfish Emergency Pour vinegar over affected part, NEVER alcohol or water Children must be brought to the hospital ASAP for medical treatment

Class Hydrozoa Polyp form predominates Portuguese man of war Hydrocorals– very much like corals

Class Hydrozoa Order Hydroidea (hydra) Order Siphonophora – Portuguese man-o-war Physalia sp. – Floating colony of polymorphic hydrozoans nectophores,phyllozooids, gastrozooids, gonozooids, dactylozooids Order Hydrocorallina

Class Anthozoa (reef-building corals, anemones, sea fans, sea pansies) Absence of medusa Sea anemones and corals 70% of all cnidarian species Subclass Hexacorallia Subclass Octocorallia Coral wars Anatomy of a polyp (Source: NOAA)

Class Anthozoa Coral spawning 4 days after the new moon in the summer

Subclass Hexacorallia Can be ahermatypic or hermatypic (reef- building corals) Endosymbiont photosynthetic dinoflagellates called zooxanthellae (Symbiodinium) play an important role in coral growth. The symbiosis is quite fragile and can be thrown off balance by stressors in the environment.

Subclass Octocorallia Sea fans, seawhips (gorgonians), pipe corals Brain corals are also octocorals

Distribution of coral reefs

The Coral Triangle

Coral Reefs Corals in a reef are not stationary—there is a war for space going on all the time. The complex interactions and many micro habitats in a coral reef are key to its high species diversity. This ecosystem is being threatened by pollution, ocean acidification, and bleaching higher sea surface temperatures.bleaching