Marine Science: Ichthyology and Fish Biology

Vocabulary practice flashcards covering fish taxonomy, anatomy, circulatory and digestive systems, osmoregulation, sensory adaptations, coloration mechanisms, and reproductive strategies.

Ichthyology

The scientific study of fishes and how they have adapted in their environment.

Taxonomy

The science of classification and grouping living things based on shared characteristics.

Phylum Chordata

A taxonomic phylum characterized by four key anatomical features: a single dorsal hollow nerve cord, gill or pharyngeal slits, a notochord, and a post-anal tail.

Subphylum Vertebrata

Chordates characterized by having a backbone (vertebral column), a brain encased in a skull, an endoskeleton, and bilateral symmetry.

Agnatha

The class of jawless fishes, which includes hagfishes and lampreys.

Hagfish

Exclusively marine jawless fishes with $70$ known species and a super slimy defense mechanism, known to eat dead or dying organisms from the inside out.

Lamprey

Jawless fishes ($30$ known species) that are mostly freshwater, feed on bottom invertebrates, and attach to other fish to suck blood.

Chondrichthyes

The class of cartilaginous fishes—including sharks, skates, rays, and ratfishes—possessing a skeleton made of cartilage, movable jaws, usually a ventral mouth, paired lateral fins, and placoid scales.

Placoid Scales

Dermal denticles that cover the skin of cartilaginous fishes.

Ram Ventilation

The method of breathing used by most sharks, where swimming forward forces water across the mouth and over the gills.

Bull Shark (Carcharhinus leucas)

A primarily marine shark species notable for its ability to travel up freshwater rivers.

Pygmy Shark (Squaliolus laticaudus)

The smallest shark species, reaching a total length of $25\,\text{cm}$.

Whale Shark (Rhiniodon typus)

The largest shark species, reaching lengths of up to $12\,\text{m}$.

Rays

Dorsoventrally flattened cartilaginous fishes with ventral mouths, grinding plate teeth, $5$ pairs of ventral gills, eyes on top of the head, a whip-like tail with a stinging spine near the base, and live birth.

Skates

Dorsoventrally flattened cartilaginous fishes with ventral mouths, grinding plate teeth, and $5$ pairs of ventral gills that lay eggs and lack a whip-like tail or stinging spine.

Ratfishes (Chimaeras)

Deep-water cartilaginous fishes (~$30$ known species) measuring $60\,\text{cm}$ to $1\,\text{m}$ in length, having one pair of covered gill slits, feeding on bottom-dwelling crustaceans and molluscs, and where females are typically bigger than males.

Osteichthyes

The class of bony fishes comprising about half of all vertebrates ($>31{,}000$ species), characterized by a skeleton made partially of bone, an operculum, fin rays, a terminal mouth with a protrusible jaw, and a swim bladder.

Operculum

A protective bony flap that covers and encloses the gills in bony fishes.

Cycloid and Ctenoid Scales

Scales made of bone covered by skin and mucous in bony fishes; cycloid scales are smooth, whereas ctenoid scales have rough edges.

Swim Bladder

A gas-filled internal organ found in bony fishes that regulates buoyancy.

Homocercal Caudal Fin

A symmetrical tail fin characteristic of most bony fishes.

Pyloric Caeca

Blind-ended fingerlike tubes connected to the intestine in bony fishes that secrete digestive enzymes.

Spiral Valve

A corkscrew-shaped internal structure found mainly in the intestine of cartilaginous fishes that increases surface area for nutrient absorption.

Cloaca

The common chamber and exit for digestive waste and reproductive products in cartilaginous fishes.

Liver (in Cartilaginous Fishes)

A large organ that secretes bile to break down fats and is notably enlarged with oil to help provide buoyancy in the absence of a swim bladder.

Fish Circulatory System

A closed, single-circuit circulatory system powered by a $2$-chambered heart, where arteries deliver oxygenated blood to the body and veins return deoxygenated blood and dissolved $\text{CO}_2$ to the heart.

Osmoregulation in Bony Fish

The physiological mechanism where marine fish drink hypertonic seawater to replace lost water, excrete excess salts through specialized chloride cells in the gills, and produce low volumes of urine via the kidneys.

Osmoregulation in Cartilaginous Fish

The process of retaining urea and TMAO in the blood to keep solute concentration close to seawater, absorbing water through the skin and gills, and eliminating excess sodium and divalent ions via the rectal gland and kidneys.

Rectal Gland

An organ located near the intestine in cartilaginous fishes that actively excretes excess sodium and salts to regulate internal osmolarity.

Olfactory Sacs

Sensory structures in fish that function in smelling by detecting dissolved chemical components in the water.

Barbels

External whisker-like appendages equipped with taste buds found on many bottom-feeding fishes.

Otoliths

Calcareous ear stones resting on sensory hairs that detect movement and gravity to maintain balance and equilibrium in bony fishes.

Lateral Line

A sensory system consisting of small, pore-opened canals along each side of the body lined with neuromasts that detect vibrations in water to maintain position in schools.

Neuromasts

Specialized mechanoreceptive cells with a cupula and sensory hairs that detect vibration and water displacement within the lateral line.

Ampullae of Lorenzini

Pores located on the anterior ventral surface of cartilaginous fishes connected to jelly-filled canals that detect weak electrical fields, aiding in prey detection and navigation.

Chromatophores

Irregularly shaped dermal cells with varying amounts of pigment that aggregate or disperse pigment granules to change skin coloration.

Iridophores

A specific type of chromatophore containing reflective crystals that produce iridescent colors by selectively scattering and reflecting light.

Leucophores

Dermal structural cells that reflect white light.

Warning Coloration

Bright, conspicuous skin patterns that make a fish easy to see, signaling bad taste, poison, or venom to deter predators (exemplified by Lythrypnus dalli).

Cryptic Coloration

Camouflage coloration that allows an organism to blend into its surrounding environment, deceiving predators or prey (exemplified by Syanceia verrucosa).

Disruptive Coloration

High-contrast markings, such as stripes, bars, or spots, that visually break up the outline of a fish's body (exemplified by Sebastes serriceps).

Countershading

A coloration scheme featuring a dark dorsal side and a light ventral side, disguising open-water animals from predators viewing them from above or below (exemplified by Prionace glauca).

Oviparity

A reproductive strategy in which eggs are spawned and develop outside the mother via internal or external fertilization (seen in Medialuna californiensis and Paralabrax clathratus).

Ovoviviparity

A reproductive mode where fertilized eggs remain and develop inside the mother's uterus without direct maternal nutrient delivery, resulting in live birth (seen in Myliobatis californica).

Viviparity

A reproductive strategy where embryos receive direct nourishment from the uterine wall (without an egg shell) followed by live birth (seen in Embiotoca jacksoni).

Parthenogenesis

A form of asexual reproduction involving the development of an unfertilized egg into a female embryo without sperm fertilization (documented in Sphyrna tiburo).

Simultaneous Hermaphroditism

A condition in which an individual produces functional sperm and eggs at the same time, facilitating cross-breeding or rare self-fertilization in deep-sea habitats (seen in Hypoplectrus floridae).

Sequential Hermaphroditism

A reproductive adaptation in which an individual changes sex during its lifespan in response to social cues and hormonal shifts.

Protandry

A form of sequential hermaphroditism where an individual begins life as a male and later transitions into a female.

Protogyny

A form of sequential hermaphroditism where an individual begins life as a female and later transitions into a male (seen in Bodianus pulcher).