Porifera, Cnidaria, and Protozoa Vocabulary

Vocabulary flashcards covering Porifera (sponge structural features and cell types), Cnidaria (classes, dimorphic morphs, cnidocytes, and nerve nets), and Protozoa (Paramecium organelles, reproduction, and amoeboid forms).

Phylum Porifera

A phylum of aquatic, mostly marine animals (sponges) characterized as sessile, benthic filter feeders lacking true tissues, organs, muscles, nerves, eyes, or mouths.

Grade Parazoa

An ancestral grade of multicellular animal life (Metazoa) that lacks true tissues, represented primarily by sponges.

Choanocytes

Specialized collar cells in sponges featuring a flagellum surrounded by a collar of microvilli; they generate water currents and capture organic food particles ($0.1\text{--}5\,\mu\text{m}$) for intracellular digestion.

Pinacocytes

Tightly packed cells that line the outer exterior surface of a sponge.

Archeocytes

Amoeboid cells (also called amebocytes) in the sponge mesohyl involved in phagocytosis, completing food particle digestion, and distributing nutrients throughout the cell layer.

Spicules

Microscopic skeletal elements in sponges composed of calcium carbonate or silica, providing structural support.

Spongin

A fibrous collagen protein network forming the skeletal support structure in certain sponges, such as bath sponges.

Asconoid

The simplest sponge canal architecture, characterized by a single central spongocoel lined with choanocytes and water entering directly via dermal ostia.

Syconoid

A sponge body architecture featuring folded body walls that form radial canals lined with choanocytes.

Leuconoid

The most complex and filter-feeding efficient sponge architecture, containing extensive branched incurrent and excurrent canals leading to numerous flagellated chambers.

Choanoflagellates

Single-celled or colonial flagellated protozoans that share strong structural similarity to sponge choanocytes and represent the sister group to Metazoans.

Foraminifera

A group of amoeboid protozoans possessing calcium carbonate shells (tests) and pseudopods, whose fossilized remains accumulated to form limestone structures like the White Cliffs of Dover.

Contractile Vacuole

An osmoregulatory organelle in freshwater protozoans like Paramecium that collects excess internal water and excretes it to maintain cellular osmotic balance.

Macronucleus

The larger nucleus in Paramecium that controls day-to-day cellular metabolism and vegetative functions.

Micronucleus

The smaller nucleus in Paramecium dedicated strictly to sexual reproduction, undergoing meiosis and exchange during conjugation.

Paramecium Conjugation

A sexual reproductive process in Paramecium where two cells join and exchange haploid micronuclei generated through meiosis, giving rise to genetically distinct cells.

Phylum Cnidaria

A phylum of ancient, diploblastic metazoans displaying radial symmetry, a simple nerve net, a gastrovascular cavity, and specialized stinging cells called cnidocytes.

Diploblastic

Having a body structured from two germ tissue layers: an outer ectoderm (epidermis) and an inner endoderm (gastrodermis), separated by non-cellular mesoglea.

Polyp

The sessile, tubular body morph of a cnidarian with an upward-directed mouth surrounded by tentacles.

Medusa

The motile, umbrella- or bell-shaped body morph of a cnidarian with a downward-facing mouth and marginal tentacles.

Mesoglea

The non-living gelatinous matrix located between the epidermis and gastrodermis in cnidarians.

Cnidocytes

Specialized stinging cells unique to Phylum Cnidaria that contain explosive capsule organelles called cnidae or nematocysts.

Nematocyst

A microscopic capsule within a cnidocyte that, when triggered, rapidly ($\sim 10\,\text{ms}$) everts a barbed, hollow thread to inject paralyzing toxins into prey.

Gastrovascular Cavity

The central digestive compartment of cnidarians with a single opening functioning as both mouth and anus, where extracellular digestion occurs.

Hydrostatic Skeleton

A body support mechanism consisting of an incompressible fluid-filled gastrovascular cavity closed at the mouth, against which contractile cells exert pressure.

Epitheliomuscular Cells

Cells in the cnidarian epidermis containing longitudinal myofibrils at their bases, responsible for shortening body length upon contraction.

Nutritive-muscular Cells

Gastrodermal cells in cnidarians that absorb nutrients and contain circular myofibrils, which cause the body to narrow and elongate when contracted.

Nerve Net

A simple, diffuse network of interconnected sensory and motor neurons, synapses, and neurotransmitters present across tissue layers in cnidarians, coordinating movement without a brain or central nervous system.

Pneumatophore

The gas-filled polyp structure that functions as a floating crest in colonial hydrozoans such as the Portuguese man-of-war.

Dactylozooids

Specialized polyps in colonial hydrozoans equipped with long, coiled stinging tentacles used for defense and prey capture.

Class Myxozoa

A class of highly reduced, obligate endoparasitic cnidarians that infect aquatic hosts such as fish.

Turritopsis

A genus of hydrozoans known as the 'immortal jellyfish' capable of reverting its life cycle from the adult medusa back to the juvenile polyp stage via cell transdifferentiation.

Acrorhagi

Specialized fighting tentacles packed with potent toxin-filled nematocysts located on sea anemones (Anthopleura elegantissima), used in territorial defense against competing non-clone anemones.

Green Fluorescent Protein

A bioluminescent protein originally isolated from the hydrozoan jellyfish Aequorea victoria, widely used as a molecular marker in biological research.