CNIDARIANS AND CTENOPHORA

Diploblastic

 (two germ layers: ectoderm and endoderm, with mesoglea in between).

polyp

-Sessile (attached) form (e.g., Hydra, sea anemone).

 Free-swimming, bell-shaped form (e.g., jellyfish). 

Medusa

Cnidocytes and Nematocysts

 Specialized stinging cells used for defense and capturing prey.

Incomplete digestive system

• single opening functions as both mouth and anus

Nervous system Cnidarians and Ctenophora

Simple nerve net, no centralized brain

Asexual

• budding

•  Parent Hydra forms a bud → Bud develops tentacles and mouth → Detaches and becomes independent.

sexual

gamete formation

• Gametogenesis & Fertilization)

   Testes produce sperm & ovaries produce eggs → Fertilization occurs → Zygote forms.

Phylum ctenophora

 commonly referred to as comb jellies, encompasses a group of marine invertebrates known for their distinctive, jelly-like appearance and unique locomotive mechanisms.

 These creatures, often mistaken for jellyfish, play a significant role in marine ecosystems across the globe.

Comb plates

• biradial symmetry and are equipped with eight rows of cilia, known as

• which facilitate swimming and prey capture

Collablast

• sticky cells on their tentacles, to ensnare their prey, which mainly includes small crustaceans, fish eggs, and other marine invertebrates.

Nematocyst

1. a specialized cell in the tentacles of a jellyfish or other coelenterate, containing a barbed or venomous coiled thread that can be projected in self-defense or to capture prey.

Bioluminescence

• A notable feature of many ctenophore species is their ability to produce light bioluminescence, adding a mystical aspect to their presence in the ocean waters

  

stomodaeum

the large, expandable gastric cavity that opens from the mouth, also known as the pharynx, and is a key part of their digestive system

aboral anal pores

refers to a pair of small pores located at the aboral (opposite the mouth) end of the animal, through which waste products are expelled from the branched endodermal canal system

Colloblast

specialized, adhesive cells found in the tentacles of ctenophores (comb jellies) used to capture prey

statocyst

a key sensory organ located at the aboral pole (opposite the mouth) that functions as a balance and orientation sensor, containing a statolith and balancers to detect gravity and movement

hermaphroditic

an organism possessing both male and female reproductive organs, or exhibiting both male and female characteristics

cydippid larva stage.

a free-swimming, larval stage of ctenophores (comb jellies) that closely resembles the adult, particularly those belonging to the order _______ and are known for their direct development and early reproduction

Predators of Zooplankton

Regulate populations of small marine organisms.

Bioluminescence

 Studied for biomedical applications.

Marine Biodiversity

Contribute to oceanic food chains

Invasive Species Concern

Some ctenophores (e.g., Mnemiopsis leidyi) disrupt fish populations in non-native waters

Sexual Reproduction of Coral Anemone life cycle

 Gamete release → Fertilization → Planula larva → Settlement → New polyp formation.

Asexual Reproduction of Coral Anemone life cycle

•  Budding → New polyps form coral colonies.

•  Fragmentation → Broken pieces regenerate into new individuals.

   Pedal Laceration (Sea anemones) → Small tissue pieces develop into new anemones.

Asexual Reproduction pf Hydra (BUDDING)

 Parent Hydra forms a bud → Bud develops tentacles and mouth → Detaches and becomes independent.

example: Hydra viridissima (green hydra) and Hydra oligactis (brown hydra)

Sexual Reproduction of Hydra (Gametogenesis and Fertilization)

•  Testes produce sperm & ovaries produce eggs → Fertilization occurs → Zygote forms.

Example: Hydra circumcincta

Planula Larva Stage

• Zygote develops into a planula → Planula settles → New Hydra forms