Systems

What are the levels of biological make-up?

Cell = smallest unit of life

Tissues = collection of cells (same type/function)

Organs = collection of tissues (different type/function but work together)

Systems = collection of organs working together

What are examples of tissues?

Muscle

Bone

What are examples of organs?

Stomach

Heart

What are examples of systems?

Reproductive

Digestive

What is the largest system in the body?

Integument system (skin)

What does the skin do?

Acts as a protective barrier between the internal environment and the external environment

Involved in sensory reception, secretion, excretion, respiration, heat regulation, locomotion, coloration, digestion, nutrition, mineral deposition, osmoregulation

What is the function of the integument system?

Help maintain body form

Provide protection from abrasions

Support accessory structures

Allow for movement of ions and solutes

Minimize hydrodynamic friction

Prey capture/manipulation

What are the 2 layers of skin?

Epidermis

Dermis

What is the epidermis?

Outer, protective, nonvascular layer

What is the epidermis’s purpose?

Contains mucous glands, venom glands, photophores, sense organs, lateral line organs

Dermal denticles pass through this

What is the dermis?

The underlying connective tissue layer

What is the dermis’s purpose?

Contains nerve endings, blood vessels, and lymph vessels

Dermal denticles originate here

What are the cellular glands?

Primarily mucus and venom glands

What is the function of the neural crest cell?

Create mesenchyme for development of photophores, chromatophores and scales/dermal denticles

What is the function of the hard structure (dermal denticles) in the soft tissue?

Creatures structure for the body

Soft tissue = mobility

Dermal denticle = more protection

Where are the photophores located?

In the epidermis

What are the light from photophores used for?

Countershading

Schooling (species recognition)

Prey attraction

Obscure position of mouth

What families are photophores present in?

Etmopteridae

Dalatiidae

How do dermal denticles help with hydrodynamics?

They have ridges and cusps

How do dermal denticles change throughout life?

Skates, rays, chimaeras rely on mucus secretion (have reduced denticles)

Embryos use mucus for protection (scales displace mucoid cells during growth)

Adults still secrete mucus but on a smaller scale

Scales are shed and formed continuously and get larger as the animal grows larger

What type of dermal denticles do fast swimmers (Mako, Hammerheads, Dusky)?

Smaller, lighter denticles (300 microns wide, 7 ug)

More dermal denticles per square centimeter (11.5)

Why do faster swimmers have smaller dermal denticles?

For good hydrodynamics (makes them light in the water column)

Water flowing over something small and smooth = less friction

What type of dermal denticles do moderate swimmers have (Sandbar, Blue)?

Moderate length and weight (300 microns wide, 40 ug)

Moderate denticles per square meter (8.6)

What type of dermal denticles do sluggish/benthic swimmers have (Nurse, Sandtiger)?

Large, heavy denticles (600 microns, 40 ug)

Less denticles per square meter (2.4)

Why do benthic swimmers have larger dermal denticles?

No need to maintain positions in the water column (not streamlined/light, largest/heaviest dermal denticles)

What are some modifications of scales?

Fin spines

Stingray spines

Rostral teeth

Teeth

How do stingray spines work?

Stop growing after reaching full size (can be replaced!)

Covered in a heath of skin/mucus

2 ventrolateral grooves house venom glands

Ending point has barbs that face backward along the spine

What are the 3 main properties of water?

Very dense

High viscosity (resistance to deformation)

Energetically costly to move

What are the types of drag?

Frictional drag

Form/Pressure drag

What is frictional drag?

Interaction between the surface of the organism and the water (nothing to do with speed of the animal)

What is form drag?

Difference in pressure in front of the organism verses behind the organism

How does frictional drag work?

When water molecules hit a structure, they lose momentum

The water closest to the body is slowed the greatest, while the effect lessens further from the body surface

What is a boundary layer?

Non-moving water layer that creates friction with surrounding water

How do elasmobranchs reduce frictional drag?

Reduce surface area

How do elasmobranchs reduce surface area?

Fold in fins (EX: Chimaera)

Cover body surface with mucus

Reduce scale sizes

Schooling

Move out of high current water

How does form drag work?

When water flow separates away from the body (causes backflow)

More pronounced at higher speeds

Greater than frictional drag

What is backflow?

Chaotic water movement to fill in the low pressure area

How do elasmobranchs reduce form drag?

Increase surface roughness

Streamline shape (fusiform, tapering)

Life history traits

How do elasmobranchs increase surface roughness?

Increase the dermal denticles —> this will increase frictional drag

Each divot from the dermal denticle creates miniature backflow

By the time the flow reaches the end of the animal there is already a natural backflow

How do fin sizes differ in sharks?

Pelagic need more lift so they have bigger fins (more form drag)

Benthic need less lift so they have smaller fins (less form drag)

What is the general tooth structure?

Made of apatite crystals (calcium phosphate)

Acellular bone

Not anchored in the jaw (on a fibrous tooth bed)

Dermal denticles and teeth are basically identical

Why do sharks replace teeth?

They need different size teeth at different life stages (juveniles replace more because they are growing quicker)

Replacement times vary (some can even replace entire rows at a singular time)

What is sexual heterodonty?

The differences in teeth depending on sex

Atlantic stingray (males = pointy teeth, females = flat teeth)

What are ontogenic differences in teeth?

Differences in teeth depending on life stage

Great White (juveniles = pointy teeth because smaller prey items, adults = large, serrated teeth)

Give some examples on how teeth dictate diet.

Large central cusp with lateral cusps (clutching/holding fish/invertebrates)

Long, thin and pointed, angled inward (catch slippery fish/squid, tearing flesh)

Serrated and triangular, angles (Tear, cutting/sawing chucks of flesh)

Flat millstone of pavement-like (grinding shellfish/crabs)

Low molar-like (crush crustaceans)

Hundreds of tiny teeth (filtering plankton/small fish)

What trophic level are most sharks?

Tertiary consumers

What do apex predator sharks eat?

Dolphins, seals

What do tertiary consumer sharks eat?

Squid, small fish, invertebrates

What do primary consumer sharks eat?

Plankton

What is the purpose of the digestive system?

Process by which food is broken down into usable products and waste

Why do sharks need a strong, effective digestive system?

They cannot chew food into smaller pieces

What is a unique thing sharks can do with their stomachs?

Evert their stomachs/regurgitate to rid their body of items that are indigestible/harmful

What are the main organs of the digestive system?

Mouth

Oral cavity

Esophagus

Stomach

Intestine

Rectum

Cloacal

What are the accessory organs of the digestive system?

Pancreas

Liver

Gall bladder

What are the types of spiral valves?

Scroll

Posterior funnel

Spiral

What elasmobranchs have scroll spiral valves?

Sphyrnidae

What elasmobranchs have a posterior funnel spiral valve?

Rays, skates

What elasmobranchs have a spiral spiral valve?

Holocephalans

Most sharks

What is this?

Scroll Spiral Valve

What is this?

Funnel Spiral Valve

What is this?

Spiral spiral valve

What do the folds in the valve reflect?

The diet

More folds = more plant-based diet

Chimaera = 2-3 folds

Basking Shark = 50 folds

What is the largest internal organ?

Liver

What does the liver do?

Produce bile

Holds squalene and other lipids for energy and buoyancy

Detoxified the blood and regulates blood products

How do livers change between a sharks mode of life?

Large, slow swimming sharks = large buoyant livers to make them neutral

Faster sharks = smallest livers, swimming aids in buoyancy

Benthic sharks = small livers because they swim at intervals + not benefit from density reduction

What type of diet do juvenile sharks normally have?

Invertebrates

What type of diet do adult sharks normally have?

Teleosts, smaller sharks, marine mammals, reptiles, birds

More diverse

What are often highly specialized diets?

Zooplankton, crustacenas, cephalopods

What trophic level typically has a more generalized diet?

Top predators

Why are digestion rates variable?

Based on type of food and species of shark

What is the typical length of eating and length of digestion?

Short feeding bouts followed by long periods of digestion

What are digestion rates affected by?

Temperature

Amout of food

How does temperature affect digestion rates?

Higher temperature accelerates digestion

Higher temperatures increase secretion of digestive enzymes

How does the amount of food affect digestion rates?

A large meal is digested more rapidly

Why do elasmobranchs have a slow digestion rate?

The spiral valve design dictates slower rates of gastrointestinal emptying, lower food consumption rates, and slower food dynamics compared to teleosts

What are the parts of the gill structure?

Gill arch

Gill raker

Primary lamellae

Secondary lamellae

Demibranch

Holobranch

What are gill arches?

Where everything projects off of

5 gill slits = 5 gill arches

What are gill rakers?

Cartilaginous projections off the gill arch

Project into the pharynx area

What are primary lamellae?

Highly vascularized structure

Comes off the other side (compared to the gill rakers) of the gill arch

What are secondary lamellae?

Site of gas exchange

Branches perpendicular off of the primary lamellae

What is a demibranch?

One set of primary lamellae + secondary lamellae on the gill arch

Happens on only 1 gill arch

What is a holobranch?

Two sets of primary lamellae + secondary lamellae

Happens on all the other arches

How does gas exchange in the gills work?

Water passes between the primary lamellae and secondary lamellae

Blood flows in the opposite direction of the water (Counter current exchange)

What is counter current exchange?

Dissolved gases diffuse faster between fluids with a high concentration gradient (flow in opposite directions to keep up the concentration gradient through the whole gills)

Low oxygen blood is continually meeting fresh water with a high oxygen concentration

This maintains the concentration gradient and oxygen continues to diffuse into the blood

What is ventilation?

Means by which water is passed over the gills

What are the types of ventilation chondrichthyans use?

RAM ventilation

Buccal ventilation

What are the 2 types of RAM ventilation?

Obligate

Facultative

What is RAM ventilation?

Forward movement is used to pass water over gills

What types of elasmobranchs use RAM ventilation?

Most highly active fish

What is obligate RAM ventilation?

Must have forward motion at all times

What is facultative RAM ventilation?

Use RAM ventilation when moving but can actively ventilate when at low speeds/when stopped

How do RAM ventilating elasmobranchs maintain oxygen uptake when oxygen levels decline?

Swim faster

Open mouth wider

Change respiratory efficiency (increasing blood flow [perfusion] + recruit lamellae [secondary])

What is buccal ventilation?

The use of the buccal and pharyngeal/gill movements to pass water over gills

Some have specialized muscles to contract gills and pump water

What are the steps to buccal ventilation?

Open mouth and close gills

Depress the tongue to expand the buccal cavity and create negative pressure

Pressure change forces water in the mouth

Mouth closes

Gills open

Floor of the buccal cavity raises and forces the water out over the gills

How do spiracles help in buccal ventilation?

Keep mouth closed and drop their tongue to draw water in from the spiracles

What does the excretory system do?

Maintains proper concentration of internal ions, proper body volume (water column), osmotic balance, metabolic end products, foreign substances

Where is the kidney?

Embedded in dorsal cavity wall

Runs entire length of the body

What is the function of the kidney?

Arteries branch off the dorsal aorta and enter the kidney where the blood is filtered

Some molecules are reabsorbed for aid in osmoregulation

Nitrogenous waste is collected and supplied to the ureter for excretion as urea

What type of circulatory system do sharks have?

Closed

What does it mean to be a closed circulatory system?

Blood is contained in arteries and veins and a muscles continually contracts to circulate it