Invertebrate Zoology, Embryonic Development, and Animal Tissues Flashcards

Comprehensive vocabulary flashcards covering developmental biology, Porifera, Cnidaria, Platyhelminthes, Annelida, and animal tissues.

Isolecithal

Describes an egg with a small amount of yolk evenly distributed throughout the cytoplasm.

Meroblastic Cleavage

Incomplete or partial cleavage where only a portion of the egg cytoplasm divides due to the presence of a large yolk mass.

Holoblastic Cleavage

Complete cleavage where the cytokinesis furrow cleaves completely through the entire egg.

Coelblastula

A hollow blastula consisting of a blastoderm layer surrounding a central fluid-filled blastocoel cavity.

Discoblastula

A blastula produced by discoidal meroblastic cleavage, consisting of a cap of blastoderm cells atop an uncleaved yolk mass.

Schizocoely

The mode of coelom formation where the mesoderm splits to create the body cavity.

Enterocoely

The mode of coelom formation where the mesoderm and coelomic cavity outpouch or bud directly from the wall of the archenteron.

Archenteron

The embryonic primitive gut cavity formed during gastrulation that communicates with the outside via the blastopore.

Metamorism

The segmental organization of the body into repeated longitudinal units or segments characteristic of annelids.

Trochophore Larva

A free-swimming, ciliated marine larval stage characteristic of annelids and related invertebrates.

Prostomium

The anterior-most pre-oral lobe or region of an annelid head situated in front of the mouth.

Peristomium

The first true body segment of an annelid that surrounds the mouth.

Parapodia

Paired, lateral, unjointed fleshy appendages found on body segments of polychaetes used for locomotion and respiration.

Chaeta

Chitinous bristles or setae extending from the body wall or parapodia of annelids used in locomotion and anchoring.

Nephridia

Tubular excretory and osmoregulatory organs found repetitively in annelid segments to filter coelomic fluid and remove waste.

Clitellum

A specialized glandular region of the epidermis in earthworms and leeches that secretes mucus during copulation and forms a cocoon for eggs.

Prohaptor

The anterior attachment organ found in monogenean flatworms.

Opisthaptor

The specialized, posterior attachment organ in monogenean flatworms, often equipped with hooks, suckers, or clamps.

Acetabulum

The specialized ventral muscular sucker of trematodes used to anchor onto host tissues.

Scolex

The anterior attachment organ or 'head' of a cestode (tapeworm) equipped with suckers or hooks for adhering to the host intestine.

Rabdite

Rod-like secretory structures in the epidermal cells of free-living flatworms that discharge to form protective mucus.

Tegument

The specialized syncytial, metabolically active non-ciliated external body covering found in parasitic flatworms.

Flame Cell

A specialized hollow excretory and osmoregulatory cell in flatworm protonephridia containing a tuft of beating cilia.

Miracidium

The ciliated, free-swimming first larval stage that emerges from a trematode egg and infects an intermediate host.

Cnidocyte

A specialized stinging cell unique to cnidarians that contains an eversible stinging organelle.

Nematocyst

The stinging organelle or capsule within a cnidocyte that discharges an eversible coiled venom-bearing thread upon stimulation.

Velum

A circular muscular shelf of tissue projecting inward from the umbrella margin of hydrozoan medusae that aids in jet propulsion.

Rhoplaium

A club-shaped sensory structure located on the margins of scyphozoan medusae that houses statocysts and ocelli.

Planula

The free-swimming, ciliated, diploblastic larval stage typical of cnidarians.

Gastrozooid

A specialized feeding polyp in colonial cnidarians equipped with a mouth and tentacles.

Gonozooid

A specialized non-feeding reproductive polyp in colonial cnidarians responsible for producing medusae.

Dactylzooid

A specialized elongated, tentacle-like defensive and prey-capturing polyp in colonial cnidarians heavily armed with cnidocytes.

Pinacocyte

A flattened, epithelial-like cell forming the outer protective layer (pinacoderm) of sponges.

Choanocyte

A flagellated collar cell lining sponge chambers that generates water currents and traps food particles.

Archaeocyte

A totipotent, amoeboid wandering cell within the sponge mesohyl capable of differentiating into any cell type.

Mesohyl

The gelatinous, proteinaceous extracellular matrix located between the pinacoderm and choanoderm layers in sponges.

Spongin

A fibrous, flexible structural collagenous protein that forms the skeletal framework of many sponges.

Gemmule

An internal, dormant asexual reproductive bud formed by freshwater and some marine sponges to survive unfavorable conditions.

Asconoid

The simplest sponge body form characterized by a central unbranched spongocoel lined directly by choanocytes.

Leuconoid

The most complex and largest sponge body organization, consisting of branched incurrent canals and distinct choanocyte chambers.

Epithelial Tissue

A primary tissue type composed of contiguous sheets of closely packed cells that cover body surfaces, line cavities, and form glands.

Connective Tissue

A primary tissue type consisting of scattered cells embedded in an extracellular matrix that provides structural support and binds tissues together.

Ground Substance

The non-cellular, amorphous, gel-like component of connective tissue extracellular matrix surrounding cells and fibers.

Lacunae

Small cavities or spaces within dense connective tissue or skeletal matrix that house specialized cells.

Obliquely Striated Muscle

A muscle tissue type featuring myofilaments arranged in a staggered or diagonal striation pattern relative to the cell axis.

Parenchyma

The essential, specialized functional tissue of an organ, distinguished from structural or supportive connective tissue.

Stroma

The supportive structural framework composed of connective tissue and blood vessels that supports the parenchyma of an organ.

Glial Cell

Non-conducting supporting cells of the nervous system that protect, insulate, nourish, and support neurons.