•Male first, then female

•Female, then male•Both at the same time

Hermaphrodites

The gonad of the mangrove rivulus is half

ovary and half testis

Parrotfish

Parrotfish•Female when young

•Male as they get older

Black Sea Bass

Black Sea Bass•Switch sex back and forth quickly

•More often female as they get older

Clownfish

Clownfish• There is only one female in

each group• The female and the largest

male in group do all the spawning

• When the female dies, the largest male replaces her and the second largest male becomes the new head male

Explaining Nemo

• Nemo should have had a lot of uncles around

• When Nemo’s mom died..• His dad should have turned into his

mom and…• One of his “uncles” should have

turned into his dad

Why Hermaphrodites?

• Dominant male has a harem. He has spectacular reproductive success because he gets to fertilize the eggs from many females during a “spawning aggregation”.

• Other smaller males could not compete with the dominant male, so they would have no success at all.

• If they are female instead, then they have some success right now, and have a shot at being the dominant male when they get older and larger.

• Sneaky strategy…– Small males that look like females can sneak into

the spawning aggregation

Midshipman

Midshipman• Type 1 males: Grow slowly but

get big. Strong vocal system for courting

• Type 2 males: Mature quickly, small size, huge testes!

• Type 2s sneak in and fertilize the female that the Type 1 fish attracted

Other Sneakers• Bluegill

– Dash in, dash out– Female mimics

• Salmon– Remember the Jacks?

Chromosome Anatomy

1 2 3 4

Meiosis

1st polar bodyJUNKJUNK

Egg

2nd Polar Body

Egg

2nd PolarBody

Embryo

Embryo

<< >

Poeciliidae

The polar body staysSperm activates eggSperm DNA rejected

>>>>

<

<

>><<

XX

XX

GynogeneticFish

Irradiated sperm activate egg. Heat and pressure save polar body.Sperm DNA doesn’t participate

Triploid FishTriploid Fish•Heat and pressure prevent the loss of the polar body

•Fish has 3 sets of chromasomes

Hydraulic cylinder for

making triploid fish eggs

>><< >>

<<

>>

<<

XX

XX

XX

Making aTriploid

Heat and pressure prevent loss ofpolar body

Fish grows up with anExtra set of chromosomes

<<

DiploidRed Blood

Cell

TriploidRed Blood

Cell

Recognizing Triploids

CoulterCounter

X XX XX XXY XY XY

XX= FEMALE

Mendel Punnett

XX x XY

XXXXXYXY

Male and female fish produce young with a 50:50 sex ratio

Key Color = sex coded forby genes (genotype)

= sex that fish looks and acts like (phenotype)

XX x XY

XXXXXYXY

XXXXXYXY

Testosterone

Testosterone feed causes all of the tilapia to grow up looking and acting like males regardless of their DNA.

WZ x WW

WZWZWWWW

Sex determination in some tilapia species is opposite to that of the normal X, Y system. The WZ fish are the females.

WZ x XY

WXWYZXZY

Some Die:All survivorsare male

Crossing pure blood WZ fish with pure XY fish can produce all male young.

WZ x WW

WZWZWWWW

WWWW

WZWZ

WW x WW

WWWWWWWW

Sex reversed

Sex reversed WW fish can be used to produce all-male young.

All male fishAll male fish1. Testosterone2. WZ x XY hybrids3.Genetic “super” males

using sex reversed WW females

• HermaphroditesHermaphrodites– What does it mean?What does it mean?– What are the advantages?What are the advantages?– SneakersSneakers

• Meiosis and polar bodiesMeiosis and polar bodies• Gynogenetic fishGynogenetic fish• Triploid fishTriploid fish• Three ways to make all male tilapiaThree ways to make all male tilapia

– TestosteroneTestosterone– WZ x XY hybridsWZ x XY hybrids– Super malesSuper males