Marine Bio Invertebrates 1

Features and structures of cnidarians, porifera, and ctenaphora

Porifera

A basal phylum of sessile, primarily marine invertebrates characterized by a porous body plan lacking true tissues and organs. They utilize specialized flagellated cells called choanocytes to pump water through microscopic pores (ostia) and out an excurrent opening (osculum) for filter feeding and respiration, and are structurally supported by mineral spicules (calcium carbonate or silica) and fibrous spongin.

Choanocytes

<span>Specialized cells in sponges (phylum Porifera) that have a flagellum surrounded by a collar of microvilli, used for filtering food particles from water that flows through the sponge's body. They play a crucial role in water circulation and feeding.

Spicules

Structural elements in sponges, which can be made of calcium carbonate or silica, providing support and shape to the sponge's body. They can vary in form and size, contributing to the overall rigidity and defense of the sponge.

Osculum

The large opening in sponges (phylum Porifera) through which water exits after being filtered by choanocytes. It is essential for the expulsion of water and waste from the sponge's body.

Oista

A type of reproductive cell produced by sponges, involved in the asexual or sexual reproduction process, often encased in a protective structure that can survive unfavorable conditions.

Spongocoel

The central cavity within sponges where water is drawn in for filtering and nutrient absorption, connecting to the osculum for water expulsion.

There are three types of canals in sponges: asconoid, syconoid, and leuconoid, which determine the complexity and efficiency of water flow.

Pinacocytes

Flat, thin, epithelial-like cells that form the outer layer (pinacoderm) of porifera

Mesohyl

The inter-layer between the choanoderm and the pinacoderm on porifera. Is a gelatinous matrix.

Choanoderm

The innermost layer of porifera, formed from choanocytes

Cnidaria

A phylum of radially symmetrical, diploblastic aquatic invertebrates characterized by specialized stinging cells called cnidocytes containing nematocysts for prey capture and defense. They possess true tissues organized into an outer epidermis and inner gastrodermis separated by an acellular or cellular gelatinous mesoglea, a simple nerve net, a gastrovascular cavity with a single opening serving as both mouth and anus, and exhibit two basic body forms: sessile polyps and free-swimming medusae

Cnidocytes

Specialized stinging cells unique to cnidarians containing organelles such as nematocysts, used primarily for prey capture and defense. St9inger inside is called a nematocyst

Cnidocil

A specialized, hair-like sensory projection or modified cilium located on the apical surface of a cnidocyte. It functions as a mechanoreceptor trigger that, upon physical contact or chemical stimulation, initiates the rapid, explosive discharge of the nematocyst to inject venom or entangle prey and predators.

Nematocyst batteries

Specialized clusters of stinging cells (cnidocytes) found on the tentacles and body surfaces of cnidarians.

Endoderm

Inner-most dermal layer of cnidarians

Ectoderm

Outer-most dermal layer of cnidarians

Gastrovascular Cavity

The stomach of cnidarians and relatives

Mesoglea

A translucent, jelly-like extracellular matrix found in cnidarians (such as jellyfish, corals, and sea anemones) and ctenophores (comb jellies)

Ctenaphora

Ctenophora (commonly known as comb jellies or sea gooseberries) is a phylum of free-living, gelatinous marine invertebrates found in oceans worldwide.

They feature eight longitudinal rows of fused, beating cilia called comb plates. These act as diffraction gratings that scatter light into shimmering rainbow colors, and their rhythmic beating provides locomotion

Mesenchyme

Mesoglea with cells

Photosymbiosis

A mutually beneficial partnership between coral polyps and microscopic photosynthetic organisms—primarily dinoflagellates of the family Symbiodiniaceae (often called zooxanthellae)

Ctenes

Comb-like bands of thousands of fused cilia stacked along eight vertical strips (comb rows) that run the length of a ctenophore's (comb jelly's) body