Invertebrate Zoology Exam 2 Study Guide

Vocabulary practice flashcards covering taxonomic clades, phyla, classes, orders, larval stages, and morphological components from the Invertebrate Zoology Exam 2 study guide.

Clade Platytrochozoa

A major spiralian clade supported by molecular phylogenetic evidence that unites the phyla Entoprocta and Cycliophora alongside the clades Rouphozoa and Lophophorata.

Buccal Funnel

An anterior, bell-shaped feeding apparatus in cycliophorans surrounded by a ring of compound cilia that creates currents to sweep lobster food scraps into the mouth.

Pandora Larva

An asexually generated larva in cycliophorans that develops by internal budding and directly produces a new feeding stage on the same lobster host.

Prometheus Larva

A dwarf, non-feeding male larva in the cycliophoran sexual cycle that attaches to a feeding individual to fertilize the developing female inside.

Chordoid Larva

The sexually produced, free-swimming ciliated dispersal larva of cycliophorans equipped with a ventral chordoid organ that swims to infect a new decapod host.

Calyx (Entoprocta)

The cup-shaped upper body of an entoproct supported by a stalk, housing the visceral organs and surrounded by a ring of ciliated tentacles.

Star-Cell Organ

A specialized pulsatile mesenchymal structure found near the junction of the stalk and calyx in colonial entoprocts that aids internal fluid transport.

Phylum Cycliophora: Bauplan and Organization

Bilateral, triploblastic, and acoelomate microscopic metazoans consisting of an anterior ciliated buccal funnel, a central trunk, and a posterior disc used for attachment.

Phylum Cycliophora: Habitat and Ecology

Exclusively marine epizoic commensals that attach to the mouthpart setae of nephropid lobsters, scavenging leftover food debris from the host's meals.

Phylum Cycliophora: Locomotion and Digestion

Adult feeding stages are completely sessile, anchored by a cellular stalk disc; digestion occurs via a complete, U-shaped gut operated by ciliary suspension feeding.

Phylum Cycliophora: Internal Physiological Systems

Lacks specialized circulatory and gas exchange organs, relying on simple diffusion; excretory flame bulb protonephridia occur in the chordoid larva but are absent in feeding stages.

Phylum Cycliophora: Reproductive Strategy

A complex cycle alternating between asexual clonal budding via Pandora larvae on a single host and sexual reproduction triggered by host molting using Prometheus and chordoid larvae.

Phylum Entoprocta: Bauplan and Organization

Bilateral, triploblastic, and acoelomate goblet-shaped animals composed of a stalked calyx bearing an apical tentacular crown where both mouth and anus open inside the atrium.

Phylum Entoprocta: Habitat and Ecology

Predominantly shallow marine benthic organisms, either living as colonial branching networks on rocks and algae or as solitary commensals on other marine invertebrates.

Phylum Entoprocta: Feeding and Digestion

Ciliary suspension feeders that use currents from tentacle cilia to draw particles into a U-shaped digestive tract consisting of an esophagus, stomach, intestine, and rectum.

Phylum Entoprocta: Excretion, Circulation, and Nervous System

Possess a single pair of flame-bulb protonephridia, internal transport aided by gut circulation and star-cell organs, and a reduced nervous system centered on a single subenteric ganglion.

Phylum Entoprocta: Reproductive Biology

Reproduce asexually by budding from stolons or calyces and sexually as dioecious or hermaphroditic spawners with internal fertilization and free-swimming ciliated larvae.

Clade Lophotrochozoa

A major protostome clade defined by genomic sequencing data whose members primitively share hard external calcified structures, trochophore larvae, or a lophophore.

Radula

A minutely toothed, chitinous ribbon present in most molluscs that rasps, scrapes, or shreds food before passing it into the digestive tract.

Odontophore

A cartilaginous internal mass that supports, elevates, and moves the overlying radular ribbon during molluscan feeding.

Visceral Mass

The central dorsal region of a mollusc's body containing the internal digestive, circulatory, excretory, and reproductive organs.

Mantle (Pallium)

A dorsal fold of epithelial tissue covering the visceral mass that secretes the calcareous shell or spicules and encloses the mantle cavity.

Mantle Cavity

A fluid-filled space beneath the mantle skirt that houses the respiratory ctenidia, osphradia, hypobranchial glands, anus, and nephridiopores.

Foot (Phylum Mollusca)

A ventral, muscular organ adapted for crawling via muscular pedal waves, anchoring, burrowing into sediment, or prey capture.

Ctenidia

Comb-like or feathery gills situated within the molluscan mantle cavity that function in countercurrent gas exchange and particle filtration.

Osphradia

Specialized olfactory and chemical sensory patches positioned near the incurrent siphon or gill axis to monitor incoming water quality.

Trochophore Larva

A free-swimming, top-shaped larval form featuring an apical tuft and a band of ciliated cells (prototroch) anterior to the mouth.

Sclerites (Mollusca)

Small, calcareous spines or scales embedded within the thick cuticular mantle of aplacophorans such as caudofoveates and solenogastres.

Peristaltic Locomotion (Aplacophora)

A burrowing movement driven by alternating contractions of circular and longitudinal body-wall musculature passing along the vermiform body.

Girdle (Polyplacophora)

The thickened, muscular outer margin of the chiton mantle that encircles, secures, and partially overlaps the eight dorsal shell valves.

Hypobranchial Gland

A mucus-producing gland located in the mantle cavity roof that coats waste particles to prevent sediment accumulation on the ctenidia.

Operculum

A tough, horny or calcified disc carried on the dorsal foot of snails that seals the shell aperture when the soft body retracts.

Columellar Muscle

The primary retractor muscle anchored to the internal spire of a coiled gastropod shell that pulls the head-foot complex inside.

Torsion

A 90° to 180° counterclockwise rotation of the visceral mass and mantle cavity relative to the foot during gastropod development, moving gills and anus anteriorly.

Detorsion

An evolutionary process occurring in certain gastropods, such as sea slugs, wherein the mantle cavity and visceral organs rotate back toward a lateral or posterior position.

Pedal Waves

Rhythmic waves of muscular contraction travelling along the ventral foot surface that propel crawling gastropods smoothly across substrates.

Crystalline Style

A rotating, enzyme-coated proteinaceous rod in the bivalve stomach that grinds against the gastric shield to wind mucus strings and liberate digestive enzymes.

Veliger Larva

A planktonic larval stage derived from a trochophore, possessing ciliated lobes called a velum used for both swimming and particle capture.

Phylum Mollusca: Bauplan and Organization

Triploblastic, coelomate, unsegmented bilaterians organized into three main divisions: head-foot, visceral mass, and an overarching mantle secreting a mineralized shell.

Phylum Mollusca: Circulation and Respiration

Characterized by an open circulatory system with a dorsal heart pumping hemolymph through a hemocoel (closed in cephalopods), with gas exchange primarily through ctenidia.

Phylum Mollusca: Excretion and Nervous Organization

Excretion is accomplished by metanephridial kidneys filtering coelomic fluid; the nervous system features a circumesophageal ring with paired pedal and visceral nerve cords.

Class Solenogastres

Slender, worm-like aplacophoran molluscs covered in cuticular sclerites that lack a true shell, have a reduced pedal groove foot, and feed on cnidarians.

Class Caudofoveata

Cylindrical, head-less aplacophorans completely lacking a muscular foot, covered in spicules, that burrow through marine sediments as deposit feeders.

Class Monoplacophora

Deep-sea, limpet-shaped molluscs bearing a single uncoiled cap-shell, displaying serial repetition of internal organ systems including multiple pairs of gills and kidneys.

Class Polyplacophora

Flattened marine grazers (chitons) characterized by eight overlapping dorsal shell plates, a heavy mantle girdle, and a broad muscular clinging foot.

Class Gastropoda

The most diverse molluscan class (snails and slugs), characterized by developmental torsion, a creeping broad foot, and typically an asymmetric coiled shell.

Class Scaphopoda

Benthic marine molluscs (tusk shells) with a single curved tubular shell open at both ends, lacking gills and heart, that capture meiofauna with thread-like captacula.

Class Bivalvia

Molluscs enclosed by two hinged lateral valves connected by a ligament, lacking a head and radula, which feed via large ciliated suspension-feeding gills.

Class Cephalopoda

Active marine predators featuring a closed circulatory system, complex image-forming eyes, an advanced brain, and a foot modified into prehensile arms, tentacles, and a funnel.