Topic 4B Flashcards
Lowkey not that important, except maybe for the life cycles
Finfish reproduction cycle
- Spawning (eggs + sperm)
- Embryo/fish larvae (1-15mm)
- Absorb nutrients from attached yolk sac - Metamorphosis (biological change in morphology) –> after approx 10 days
- Fish fry –> complete depletion of yolk sac; able to feed on their own
- Juvenile (fingerling)
- Adult –> reached maturity; able to spawn
Ovaries
- Shades of light pink to dark yellow –> due to mature oocytes full of yolk granules
Testes
- Whitish from beginning of maturation to the mature stage
Molluscs
- Bivalve (hinged shells)
- Gastropod (snails/slugs)
- Cephalopod (internal shell + tentacles)
Mollusc reproduction
- Mostly external fertilisation
- Internal fertilisation in some gastropods
- Usually dioecious; some hermaphroditic
Life cycle of bivalve/gastropod
- Spawning (sperm + eggs)
- Trochophore (aka planktonic stage)
- Free swimming larvae
- Bands of cilia - Veliger
- Organs develop
- Takes the morphology of a juvenile bivalve
- suspends in water column - Metamorphosis (biological change in morphology –> settle down into substrate)
- Spat/juvenile
- settled into substrate & growing - Adult
Location of gonads in mussels
Within mantle tissue
Location of gonads in clams
At base of foot
Location of gonads in oysters
Covers the outer surface of digestive gland
Location of gonads of abalone
Left side of shell, under the foot
Location of gonads of topshell
Near shell apex
Type of spawning (mussels, clams, oysters, abalone, topshell)
Broadcast spawner
How to identify sex of bivalve
- Colour of gonads (orange for females, cream for males)
- Identify male-associated polypeptide (only present in male; detection through gel electrophoresis)
How to observe maturity of bivalve
- Round & fully developed eggs = ripe gonads
- Elongated eggs with no nucleus = unripe gonads
- use microscope
Life cycle of shrimp
- Fertilised eggs
- Nauplius
- Protozoa
- Metamorphosis
- Mysis
- Megalopa
- Juvenile
Sex of shrimp
Male: Petasma (narrow structure, found b/w the foremost pair of swimming legs)
Female: Thelycum (broader structure, b/w the last pair of pleopods which provides an anchor site for male sperm packet received during copulation
Different stages of development of shrimp
Stage 1 (immature): Transparent & not visible Stage 2 (developing): Early maturation, olive green Stage 3 (nearly ripe): Expanded, dull-greyish green Stage 4 (ripe): Diamond shaped, dark olive green Stage 5 (spent): Flaccid
Internal fertilisation shrimp (process)
- Mostly occur at night & shortly after moulting of the female
- Approach –> male follows female
- Crawling –> crawl his head under female’s tail
- Chasing –> male chases escaping female
- Mating –> male turns ventral side up & grasp female/inverted
- Deposit of spermatophore onto the thelycum of female
(Closed thelycum: ripe female, before ovarian maturatiion; Open thelycum: female w ovarian maturation, immediately before spawning)
Life cycle of crab
- Adult spawning
- Zoea (4-5 moults)
- Megalopa
- Crablet/juvenile
- Adult
Note: the warmer the water, the faster the crab moves through the stages
Stages of development in crab
Stage 1 (immature): translucent/pale-white Stage 2 (developing): early maturation, light yellow Stage 3 (pre-maturing): expanded, yellow to orange Stage 4 (ripe): occupies available space in capacity, orange to red-orange
Mating behaviour of crabs
Mostly occur at night; shortly after moulting
- Pre-copulation: matured males attracted to immature females, grab female, position her under his abdomen, male extends chelipeds out for defense
- Molting: male guards aggressively over female
- Copulation: flips female around, female opens up abdomen –> allow transfer of sperm
