Reading Assignment:• Chapter 18 Minnows, Characins and

Catfishes (Ostariophysi)

pirañha

Effect of Ammonia on Growth:• NH3 is more toxic than NH4

+

• relative Conc. Depends on pH– at 24C: 0.5% NH3 at pH = 7

34% NH3 at pH = 9

• 96 hr LC50 = 3.8 mg/L NH3

• as low as 0.6 mg/L for some spp.• slow growth & tissue damage at 0.006-0.34 mg/L

(continuous exposure)

Transport problems

Aquarium problems

end

Effects of other factors on growth:

• Growth reduced at sub-optimal salinities

end

scope

Model: effect of environment on fishes

Environmental Variable

Met

abol

ism

scope

simplify

active metabolic rate - standard metabolic rate

end

lethal

high

lethal

low

Model continued:S

cope

tolerance

lethal

low

Str

ess

stressedtolerance

hypothetical physical or

psychological stress

lethal

highEnvironmental Variable

end

end

Overview of Reproduction:Varies greatly among fishes

1. behavior:– courtship behavior– nest building– parental care versus no care– mixed behaviors

• sneaker bass• sneaker and mimic bluegills

– migration• anadromy- spawn in FW, mature in SW• catadromy - spawn in SW, mature in FW

salmon; smelt

eels

end

Anadromous salmon

end

Overview of Reproduction continued

2. Anatomy:– claspers - chondrichthyes– gonopodium - Poeciliidae– sexual dimorphism

• males larger in territorial species (salmon)

• females usu. larger in others

end

catshark with claspers

claspers

end

black molly gonopodium

end

gonopodium

end

Sexual dimorphism in salmon:

male

female

end

Overview of Reproduction continued

3. Physiology– sex chromosomes:

• XY = M; XX = F (most)

• ZZ = M and ZW = F (Poeciliidae & Tilapia spp)

• some fishes have 3 or more sex chromosomes

– sex not under complete genetic control• hermaphrodites--both sexes (many in Serranidae)

– usu. one sex at a time– exception hamlet (serranid)

• sex changes--bluehead wrasse

end

bluehead wrasse (Labridae)

female & juv.

male

• harem

• dominance hierarchy

• dominant F becomes Mend

Overview of Reproduction continued

3. Physiology continued– parthenogenesis -- egg develops w/o fertilization

• Ex: Amazon molly– all female– produce genetic clones

• Ex: gynogenesis in Phoxinus (Cyprinidae)– all female– gynogenesis--sperm required, DNA from male not

incorporated in embryo

end

Reproductive Modes in Fishes:• Oviparous -- egg layers; most fishes

– internal or external fertilization

• Ovoviviparous– internal fertilization– eggs hatch internally– live birth– yolk only nutrition– EX: Lake Baikal sculpins

• marine rockfishes

• some sharks

end

Lake Baikal

Approx. 400 mi. long

> 1 mi. deep

5315 ft

end

Reproductive Modes in Fishes: continued

• Viviparous--live birth– nutrition provided directly by mother– EX: embryonic cannibalism -- a few sharks

• fins against uterine wall -- surf perches• placenta-like structures--pericardial tissues in

Poeciliidae

end

nurse shark embryosend

lemon shark pup

yolk sac and stalk function like placenta and umbilical cordend

Reproductive Strategies:Energy Investment

egg size: number vs. survivability

carp > 2,000,000

salmon 1500-2000

parental investment: energy vs. surviv.

nest building

parental care

mouth brooders--cichlids; ariids

end

Parental care: pouches (seahorses, pipefishes)

end

femalemale

end

Parental care: guarding

bullhead--both sexes

smallmouth bass--males

end

end

nurse shark embryosend

lemon shark pup

yolk sac and stalk function like placenta and umbilical cordend

Reproductive Strategies:Energy Investment

egg size: number vs. survivability

carp > 2,000,000

salmon 1500-2000

parental investment: energy vs. surviv.

nest building

parental care

mouth brooders--cichlids; ariids

end

Parental care: pouches (seahorses, pipefishes)

end

femalemale

end

Parental care: guarding

bullhead--both sexes

smallmouth bass--males

end

end

Sensory Perception

• Most fishes have familiar senses:– sight– hearing– smell– taste– touch

• Senses generally similar to those of other verts.

end

Overview of Sensory Differences

1. Chemoreception– taste & smell; distinction blurred in water

2. Acustico-lateralis System– sensing of vibrations; hearing & lateral line

3. Electroreception– sensing electromagnetism from earth & orgs.

4. Pheromones– chemical messages from other fish

end

1. Chemoreception details

• Olfaction & taste --sense chemicals

• Differences:– location of receptors:

• olfaction -- special sensory pits

• taste -- surface of mouth, barbels

– sensitivity• olfaction -- high

• taste -- lower

end

Olfaction details:• Sense food, geog. location, pheromones• structure -- olfactory pit

– incurrent & excurrent openings (nares) divided by flap of skin

– olfactory rosette -- sensory structure; large surface area

• water movement driven by:– cilia – muscular movement of branchial pump – swimming

end

Olfaction details continued:• Sensitivity varies--high in migratory spp.• Odors perceived when dissolved chem. makes

contact with olfactory rosette• anguilid eels detect some chems. in conc. as low

as 1 x 10-13 M !– M = # moles per liter

• salmon detect amino acids from the skin of juveniles

• sea lampreys detect bile acids secreted by larvae• directional in nurse, hammerhead sharks

end

Taste details-- short-range chemoreception

• detects food, noxious substances

• sensory cells in mouth and on external surfaces, skin, barbels, fins

• particularly sensitive to amino acids, small peptides, nucleotides, organic acids

end

2. Acoustico-lateralis system

• Detects sound, vibration and water displacement

• Functions in orientation & balance

• Organs:– inner ear (no external opening, no middle ear,

no ear drum)– lateral line system

end

Hearing details:

• sound travels farther & 4.8 x faster in water

• sound waves cause body of fish to vibrate

sensory structure of ear

sensory hairs otolith

end

end

Hearing details continued:

• inertia of otoliths resist vibration of fish

• sensory hairs bend, initiating impulse

• nerves conduct impulse to auditory region of brain

end

Hearing details continued:

• certain sounds cause insufficient vibration– weak sounds– high frequency– distant sounds

• enhancements for sound detection– swim bladder close to ear– swim bladder extensions (clupeids, mormyrids)– Weberian apparatus--ossicles (ostariophysans)

end

Structure of Inner Ear:• 3 semicircular canals--fluid-filled tubes w

sensory cells (hair-like projections)

• 3 ampullae--fluid filled sacs w sensory cells

• 3 sensory sacs containing otoliths– otoliths--calcareous bones; approx. 3x as dense as

fish

Gna

thos

tom

ata

• 1 in Myxini• 2 in Cephalaspidomorphi

end

Fish Inner Ear: Fig. 10.2

semicircular canal

lagena

otolith (sagitta)

utriculus

otolith

sacculus

otolith

ampullae

end

Function of inner ear components:

• semicircular canals & ampullae --– detect acceleration in 3D

• utriculus & otolith -- – gravity and orientation

• sacculus/sagitta & lagena/otolith -- – hearing

end