Overview of Reproduction continued 3. Physiology –sex chromosomes: XY = M; XX = F ( most) ZZ = M and ZW = F (Poeciliidae & Tilapia spp) some fishes have.

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

butter hamlet

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

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

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

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

end

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

epidermis

Neruomast: Fig 10.4

water

fish

cupula

sensory cells

background pulse rate

increasing pulse ratedecreasing pulse rate

Lateral Line (cross section) Fig. 10.5

subeipdermal tissue

epidermis

lateral line porescupulae

lateral line canalendolymph

end

Lateral Line (cross section) Fig. 10.5

vibrations

nerve impulse to brain

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”

end