Triploid Fecundity: Is it Dad’s Fault?

Kate M. Ritter

Dr. Stan K. Allen

Aquaculture Genetics and Breeding Technology Center

Recent ABC Research Found that Dying Oysters were Developing Females

Aren’t Triploids Supposed to be Sterile?

MOST COMMON: No eggs, or very

few eggs

RARE: Prolific eggs

What Good is a Ripe Triploid?

Essential for tetraploid production

2N

X

= 4N

3N

4N 4N

4N

Tetraploid Breeding

Propagating Tetraploids Generation 1

Generation 2

1 million eggs

2 million/ ea.

h2

h2

Tetraploid Fecundity is Increasing… or is it not?

• Fecundity is variable

• 100,000 – 5,000,000

• Intra-annual variability • Temperature, stress, disease

• Conditioning • System capacity • Algae quality

Triploid Production

4N 2N

3N

Most of the triploid’s chromosomes come from dad.

Timeline for Concerns Over Triploid Fecundity

1997 2003 2014 2015 2016

ABC Initiative

First 3Ns in VA

First Fecundity Reports

TMRT

Mortality Project

2018: Fecundity Study

(Hudson and Murray, 2017)

Triploid Fecundity is Increasing… or is it not?

• Triploids can get ripe

• Is incidence increasing? – Or just the number of farms?

– What role does site, the environment play?

• We can reconstruct the historical record through the pedigree

Reconstructing the Historical Record

Diploid Dam Group

Number of Families

“HANA” 2

“HANA” 4

“HANA” 4

“HANA” 2

• Is increased fecundity in the tetraploid sire transferring to the triploid offspring? • Used old and new tetraploid lines to create triploids

Theoretical Origination

Number of Generations Bred

Tetraploid Sire Group

2016 1 “LGT”

2014 2 “VBOY”

2006 6 “GNL”

2002 8 “GEN”

Field Deployment

• Two Sites – Western Shore,

Rappahannock River

– Eastern Shore,

Nandua Creek

• Two reps per family,

per site – Bottom cages

2018 Sampling: Survival, Sex Ratio, Egg Counts

Expected Results

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1 2 3 4 5 6 7 8

Egg

Co

un

t (p

er g

ram

wet

wei

ght)

Generation

?

Thank you

Kate M. Ritter Flow Cytometry and Lab Specialist, Master’s Student Aquaculture Genetics and Breeding Technology Center ritter@vims.edu 804-684-7712 Thank you to Nandua Oyster Company for the use of their farm. Thank you: Beazley Fellowship AAUW IWFA Dr. Eric Guévélou