Biology of Fishes

LESSON 19

Terminology:• Plural for fish is fish• “There are many fish in my tank”

• Fishes – multiple species of fish• “The various fishes in the

ecosystem demonstrate the diversity of animals”

Variety• Fishes have a variety of shapes, sizes, colors

• Phylum Chordata• Subphylum Vertebrata

• Have an internal skeleton including backbone and skull

Variety• 3 major Classes

1) Jawless fishes2) Bony fishes3) Cartilaginous fishes

1) Jawless Fishes Hagfishes and lampreys:

Although these ancestors did not survive to the present day, it is important to recognize that they were enormously successful in their time, dominating the scene for some 140 million years, from approximately 490 to 350 MYBP.

1) Jawless fishes• Have remain virtually unchanged for more than 340 million years• Have survived through at least four major extinction events.• Most primitive fish species on Earth• Do not have scales, paired fins, or jaws

1) Jawless Fishes

• Elongated bodies• Sucker-shaped mouths• Feed by sucking on their prey

• Typically parasitic• Feed on dead or dying fish

• Skeleton made of cartilage

Characteristics• Believed to form a monophyletic group called the cyclostomes ("circle mouths")

• Members of this group of fishes produce an excessive amount of mucus as a defensive measure

Characteristics• While they are virtually blind, they have four pairs of tentacles around their mouths that are

used to detect food.

• Tongue-like structure that has barbs on it to tear apart dead organisms and to capture their prey

• Tongue secretes an enzyme that prevents blood from clotting in victim

http://www.medicalnewstoday.com/articles/282703.php

What is the goal of the study? Why is the discovery so important to evolutionary biologists?What other implications do lamprey genetics bring light to in relation to human ailments?

Hagfishes• Hagfishes are represented today by seven genera • 76 species all contained within a single family, the Myxinidae • Have tentacles• They are restricted to marine habitats throughout the temperate and tropical zones of the world• Ex: Gulfs of Mexico and Panama.

Lampreys

• Lampreys are represented by ten genera • 46 species all contained within a single family, the Petromyzontidae.• No tentacles

Habitat

• Native to Northern Atlantic Ocean • Coevolved with fish species• First found in Lake Ontario in 1835 • Invaded through shipping canals

Habitat• Niagara Falls served as a barrier to the rest of the lakes, but canals have allowed lampreys to invade the other lakes•No coevolution exists here• Fish cannot survive lamprey’s attacks here

• Great Lakes Fishery Commission releases chemicals to selectively kill lamprey larva and barriers to prevent adult species from moving upstream to spawn

2) Bony Fishes• Skeletons are made of bone• Incredibly numerous and diverse group• Approx. 50% of all vertebrate species are bony fishes•Majority are marine

• Economically important as major protein source for global communities

2) Bony Fishes

• Take in water through their mouth and pass it over gills to breathe

• Some need to keep moving to allow water to pass over gills

• Oxygen then transferred to fish’s bloodstream

• Then brought to the body’s cells

2) Bony Fishes

• Oxygen-poor water is released through operculum• Operculum: flap of flesh covering the gills

• Have one gill opening on each side of the head covered with operculum

peduncle

Bony Fish External Anatomy• Caudal fin: provides propulsion in water•Move to side-to-side•Where marine mammals move tails up and down

Bony Fish External Anatomy• Dorsal side – back side of fish•Dorsal fins: help stabilize fish and keep body from rolling over

Bony Fish External Anatomy

• Ventral side – belly side of fish• Pelvic and Anal fins:

provide stability

Bony Fish External Anatomy• Either side of fish• Pectoral fins: provide lift and propulsion•Assist in steering and moving vertically in water and column

• Fins have fleshy, translucent membranes covering bony spines

Fin Modifications- Some fish do not have all fins describedEx: Eel species – dorsal, pelvic, anal, and caudal fins are joined together

Ex: Mudskippers – modified pectoral fins allow animal to crawl on land

Bony Fishes Adaptations• Swim bladder – balloon structure filled with air near stomach and intestine

• Prevents fish from sinking if it stops swimming

Swim bladder

Bony Fish Adaptations

• Lateral line organ – detects vibrations in the water

•Numerous small cavities that run along middle of fish

Bony Fish Adaptation• Scales are covered in slimy mucus• Scales have a rounded shape

Checkpoint Describe the function of each of the following types of fins in fish. 1) Caudal - _____________________________________ 2) Pelvic - ______________________________________ 3) Anal - _______________________________________ 4) Dorsal - ______________________________________ 5) Pectoral - ______________________________________

3) Cartilaginous fishes

• This group includes sharks, skates, and rays• Have been on Earth for almost 450 million years ago• Evidence suggests many characteristics have not changed in over 100 MY

3) Cartilaginous Fishes

• Skeletons are made of bone-like substance called cartilage•Same as what makes up your nose and ears

• They have no true bones or swim bladder• Lack of bones allows for flexibility• Cartilage not easily fossilized because it decomposes quickly

3) Cartilaginous Fishes

• Most common evidence are fossilized teeth• Teeth are made of very hard substances•Enameloid•Dentine

Cartilaginous Fish Adaptations

• Placoid Scales - spiny tooth-like scales that are sharp to the touch• Embedded in animal’s skin (won’t flake

off like bony fishes)•Make the skin feel like sandpaper when

rubbed from tail to head• Rays skin feels like velvet from head to

tail

Cartilaginous Fish Adaptations• Have 5 or more gill slits on the sides or bottoms of their bodies

Cartilaginous Fish Adaptation• Spiracles: structures on their heads to take in water•Water passes over gills and out

through gill slits

• Most species (except bottom dwellers) breath through their mouths• Must swim continuously to maintain flow of water over gills

Cartilaginous Fish Adaptation• Must swim continuously to maintain flow of water over gills• Nostrils are not for breathing, but for sense of smell• Sharks have an acute smelling ability

Types of Cartilaginous fish

• Skates have flattened bodies and long tails

Types of Cartilaginous fish

• Rays have similar body shapes, but poisonous stingers

Types of Cartilaginous Fishes• Sharks are best-known cartilaginous fishes• Over 300 shark species living on Earth today• Many have fusiform streamlined body shape• Rapid declines due to human activities, pollution, climate change, overfishing• Several countries have enacted protection for sharks

General Diagram of Shark Anatomy

Shark Adaptations

• Sharks have anywhere from 6-20 rows of teeth• Back rows serve as replacement teeth for when active teeth are damaged or lost• Believed that shark can go through 20,000 teeth in its lifetime

Shark Adaptations• Shark teeth are clues to the niches of specific species• Predatory sharks have razor sharp teeth to tear prey into small pieces• Bottom-dwelling sharks have large flat teeth to crush shells of invertebrates

Shark Adaptations• Eyesight comparable to humans• Can detect blood nearly 0.3 miles away• 2/3 of shark’s brain is devoted to detecting and processing smells• Also can detect slightest sound vibrations in the water• Uses lateral line system

Shark Adaptations• Have a sixth sense• Ampullae of Lorenzini - Sensing organ consists of tiny pores located near shark’s snout• Able to pick up smallest electrical impulses produced by other organisms• Impulses created by other’s muscle or heart

contractions

Electrial Fields produced by animals in the water

Sharks: Great Ocean Predators• National Marine Sanctuaries – Channel Island: Swell

Shark Video•What adaptations do these shark exhibit?•What physical characteristics do all the sharks in the video have in common?

Checkpoint• Give 3 ways in which cartilaginous fish are different from bony fish.1) ___________________________________

2) ___________________________________

3) ___________________________________