Overview of Reproduction continued

1
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

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bluehead wrasse (Labridae)
male

• harem

• dominance hierarchy

• dominant F becomes M

female juv.
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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

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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

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Lake Baikal
Approx. 400 mi. long
5315 ft
gt 1 mi. deep
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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

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nurse shark embryos
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lemon shark pup
yolk sac and stalk function like placenta and
umbilical cord
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Reproductive Strategies

• Energy Investment
• egg size number vs. survivability
• carp gt 2,000,000
• salmon 1500-2000
• parental investment energy vs. surviv.
• nest building
• parental care
• mouth brooders--cichlids ariids

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Parental care pouches (seahorses, pipefishes)
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male
female
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Parental care guarding
smallmouth bass--males
bullhead--both sexes
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Sensory Perception

• Most fishes have familiar senses
• sight
• hearing
• smell
• taste
• touch
• Senses generally similar to those of other verts.

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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

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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

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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

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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

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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

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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

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Hearing details

• sound travels farther 4.8 x faster in water
• sound waves cause body of fish to vibrate

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Hearing details continued

• inertia of otoliths resist vibration of fish
• sensory hairs bend, initiating impulse
• nerves conduct impulse to auditory region of brain

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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)

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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

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Fish Inner Ear Fig. 10.2
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Function of inner ear components

• semicircular canals ampullae --
• detect acceleration in 3D
• utriculus otolith --
• gravity and orientation
• sacculus/sagitta lagena/otolith --
• hearing

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Lateral line

• detects water movement
• low frequency vibrations
• specialized for fixed objects and
• other organisms
• Neuromasts -- fundamental sensory structure
• single or part of lateral line system

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Neruomast Fig 10.4
water
increasing pulse rate
decreasing pulse rate
fish
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Lateral Line (cross section) Fig. 10.5
subeipdermal tissue
endolymph
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Lateral Line (cross section) Fig. 10.5
vibrations
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Lateral line details

• often well-developed on head
• system poorly developed in lampreys and
  hagfishes--neuromasts only
• often no lateral line in inactive fishes
• well-developed in blind cave fishes
• functions like a sort of sonar
• exploration -- higher speed swim-by

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