BISC316 Lab 1 Definitions

Eyes (with nictitating membrane)

Provide vision; the nictitating membrane is a protective, transparent lower eyelid that covers and protects the eye.

Mouth

Used for food and water intake during feeding and respiration.

Labial pocket

Folds of skin near the corners of the mouth that provide flexibility or sensory functions during jaw movement.

Spiracle

A modified first gill slit that allows water to enter the pharynx even when the mouth is closed or buried in sediment.

Endolymphatic pores

Small pores connecting to the inner ear, involved in balance, equilibrium, and hearing.

External nares (naris)

Nostrils used for olfaction (detecting chemical scents in water).

Ampullae of Lorenzini

Specialized electroreceptive organs sensitive to weak electrical fields produced by prey.

External gill slits (~5 pairs)

Openings through which water exits the pharynx after passing

Lateral line

A mechanoreceptive system that detects vibrations, water currents, and pressure changes.

Pectoral fins

Paired fins that provide lift, steering, and braking.

Dorsal fins (anterior and posterior)

Provide stability and prevent rolling during swimming.

Denticles (placoid scales)

Tooth-like dermal scales that reduce hydrodynamic drag and protect the skin.

Pelvic fins

Paired fins providing stability; in males, they are modified into claspers.

Claspers (male only)

Copulatory organs used to transfer sperm into the female's cloaca during internal fertilization.

Cloaca

A common exit chamber receiving the digestive, excretory, and reproductive tracts.

Caudal fin

A heterocercal tail fin that provides forward propulsion and thrust.

Coracoid bar of the pectoral girdle

Ventral skeletal support structure for the pectoral fins.

Puboischiadic (= ischiopubic) bar of the pelvic girdle

Ventral skeletal support structure for the pelvic fins.

Chondrocranium

Cartilaginous skull that encloses and protects the brain and major sense organs.

Splanchnocranium

Visceral skeleton forming the jaws and gill arches.

Vertebral column

Series of vertebrae protecting the spinal cord and providing axial skeletal support.

Rostrum

Snout projection that streamlines the head and houses electroreceptors.

Nasal (olfactory) capsules

Cartilaginous chambers enclosing the olfactory organs.

Orbit (for the eye)

Cartilaginous socket housing the eyeball.

Otic capsule

Capsule enclosing the inner ear for balance and hearing.

Endolymphatic foramen

Opening for the endolymphatic duct.

Visceral arches (#1–7)

Cartilaginous arches supporting the jaws and gills.

Mandibular arch (#1)

Forms the upper and lower jaws (palatoquadrate and Meckel's cartilage) used to capture prey.

Hyoid arch (#2)

Supports the mandibular arch and helps suspend the jaw.

Gill arches (#3–7)

Support the gills and gill rakers for respiration and feeding.

Teeth

Capture, hold, and tear prey.

Oral cavity

Passage for food intake.

Pharynx

Connects oral cavity to the esophagus; water flows through it to reach the gills.

Tongue

Immobile fleshy floor of the mouth aiding in food positioning.

Esophagus (containing rugae)

Muscular tube connecting pharynx to stomach; rugae allow expansion.

Stomach (containing rugae, main body & pyloric portions)

Storage and initial mechanical and chemical breakdown of food.

Pyloric sphincter

Valve regulating the passage of partially digested food into the intestine.

Small intestine (duodenum & spiral valve)

Primary site of digestion and nutrient absorption.

Colon

Short terminal segment leading to the rectum.

Rectal (digitiform) gland

Excretes excess salt (NaCl) from the blood to maintain osmotic balance.

Rectum

Stores feces prior to elimination.

Anus (in cloaca)

External opening for waste elimination.

Liver (right & left lobes)

Produces bile for fat digestion and stores oils (squalene) for buoyancy.

Gall bladder

Stores and concentrates bile.

Bile duct

Transports bile from the gall bladder/liver to the duodenum.

Pancreas (ventral and dorsal lobes)

Secretes digestive enzymes and hormones into the intestine.

Spleen

Immune organ involved in red blood cell production, storage, and recycling.

Kidney

Filters metabolic wastes from the blood to produce urine.

Accessory urinary duct / Archinephric ducts

Transport urine and wastes.

Urinary papilla & pore

Conveys urine into the cloaca for elimination.

Testes

Produce sperm and male sex hormones.

Archinephric ducts

Function as vas deferens to transport sperm.

Seminal vesicle

Secretes seminal fluid and stores sperm.

Sperm sac

Stores sperm prior to release.

Urogenital papilla & pore

Releases sperm and urine into the cloaca.

Claspers & Clasper groove / Siphon sac

Deliver sperm directly into the female cloaca during mating.

Left ovary

Produces eggs (ova) and hormones.

Ostium tubae

Funnel-shaped opening that catches eggs released from the ovary into the coelomic cavity.

Oviducts & shell (nidamental) gland

Transport eggs; the shell gland secretes egg cases or protective envelopes.

Uterus

Enlarged region of the oviduct where embryos develop (in viviparous/ovoviviparous sharks).

Oviduct openings in cloaca

Where eggs exit.

Embryo

Developing young shark.

Yolk sac

Provides nutrient reserves (yolk) to the embryo.

Umbilical cord

Connects the embryo to the yolk sac (in viviparous species).

Path of Food

Mouth → Pharynx → Esophagus → Stomach → Pyloric sphincter → Small intestine (Spiral Valve) → Colon → Rectum → Anus (Cloaca)

Form-Function Adaptation for path of food

The spiral valve inside the small intestine slows the passage of food and dramatically increases the surface area for nutrient absorption within a short gut length. The rugae in the stomach allow it to expand significantly for large meals.

Sperm Path

Testes → Archinephric ducts → Seminal vesicle → Sperm sac → Urogenital papilla → Cloaca → Transferred via claspers into the female.

Egg Path

Ovary → Coelomic cavity → Ostium tubae → Oviducts (where internal fertilization occurs).

Development Path

Fertilized eggs move into the uterus, where the embryo develops nourished by the yolk sac (via an umbilical cord in viviparous species) until birth as a juvenile shark.

Path of Urine

Kidneys → Accessory urinary/Archinephric ducts → Urinary papilla → Urinary pore → Cloaca