Transcript Ichthyology Fall 2000 - University of North Dakota

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
Aquarium problems
Transport problems
• as low as 0.6 mg/L for some spp.
• slow growth & tissue damage at 0.006-0.34
mg/L (continuous exposure)
end
Effects of other factors on growth:
• Growth reduced at sub-optimal salinities
end
Model: effect of environment on fishes
Metabolism
scope
simplify
scope
active metabolic rate - standard metabolic rate
Environmental Variable
end
Model continued:
hypothetical physical or
lethal
lethal
lowlow
stressed
tolerance
Environmental Variable
tolerance
Stress
Scope
psychological stress
lethal
lethal
highhigh
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
salmon; smelt
– migration
• anadromy- spawn in FW, mature in SW
• catadromy - spawn in SW, mature in FW
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:
female
male
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)
male
• harem
• dominance hierarchy
• dominant F becomes M
female & juv.
end
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
5315 ft
> 1 mi. deep
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 embryos
end
lemon shark pup
yolk sac and stalk function like placenta and umbilical cord
end
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
female
male
end
Parental care: guarding
smallmouth bass--males
bullhead--both sexes
end
end
nurse shark embryos
end
lemon shark pup
yolk sac and stalk function like placenta and umbilical cord
end
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
female
male
end
Parental care: guarding
smallmouth bass--males
bullhead--both sexes
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
Gnathostomata
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
• 1 in Myxini
• 2 in Cephalaspidomorphi
end
Fish Inner Ear: Fig. 10.2
semicircular canal
ampullae
lagena
otolith
utriculus
sacculus
otolith
otolith (sagitta)
end
Function of inner ear components:
• semicircular canals & ampullae -– detect acceleration in 3D
• utriculus & otolith -– gravity and orientation
• sacculus/sagitta & lagena/otolith -– hearing
end