Topic 4F Flashcards
Define fecundity
The no. of eggs ripened by aquatic species during a spawning season/event
- Fecundity inversely proportional to amount of parental care
Define gametogenesis
Production of gametes or creation of haploid sex cells via meiosis
Oogenesis
Egg production in females
Spermatogenesis
Sperm production in males; sperm + semen = milt
Steps of oogenesis
- Follicle development
- Yolk vesicle formation
- Vitellogenesis (true yolk formation)
- Envelope formation
- Maturation
- Ovulation
Steps of spermatogenesis
- Mitosis proliferation
- Meiosis
- Spermiogenesis
- Spermiation
When identifying fish reproductive biology, have to determine:
- Proportion of stock that is reproductively mature
- Size/age at first maturity
- Current reproductive status
- Nature of reproductive cycle for particular population/species
List the methods of determining reproductive bio/sexual maturity
- Gross anatomical criteria (visually examine gonads)
2. Gonadal somatic index (compare gonad size to fish size)
List the type of reproduction with relation to fecundity
Oviparous (least fecund)
Ovoviviparous
Viviparous (most fecund)
Gonadal somatic index (GSI)
[Gonad mass/body mass (including gonad)] x 100
- NO UNIT
What affects fecundity (besides reproduction type)
- size of fish
- nutritional status of female
List the types of fecundity
- Absolute fecundity
- Relative fecundity
- Population fecundity
Absolute fecundity
No. of ripe eggs in one spawning season/year
- Varies due to age, length, weight, species
Relative fecundity
No. of eggs produced in a season per somatic weight of fish (eggs/gram)
Population fecundity
No. of eggs pawned by population in one season
- Sum of fecundities of all females
- (Expected fecundity of an average female} x (no. of breeding females in the pop.)
Size of eggs
- Negative correlation b/w egg size & env. conditions
- Low fecundity = larger eggs (larger yolks)
State the factors that affect reproduction (broad)
- Endogenous hormone signals –> physiological factor, hormone signals
- Exogenous factors –> ecological factor
List the exogenous factors affecting reproduction
- Temperature
- Photoperiod
- Tides
- Water depth
- Substrate type
- Salinity
Temperature (exogenous factor)
- Most crucial
- Controls maturation & spawning
- Within narrow temperature range
- Limiting factor during some gametogenesis stages
- Determines sex of fish
Photoperiod (exogenous factor)
- Influences thyroid gland, migratory activity & gonadal development
- Highly associated with endogenous rhythm
Water depth (exogenous factor)
- Spawn at one depth, live in diff depths during other times
Substrate type (exogenous factor)
Related to type of breeding strategies (spawning on diff substrates)
Salinity (exogenous factor)
Various degrees of mixing, precipitation, freshwater runoff may alter spawning habits, change spawning sites due to salinity change
Tides (exogenous factor)
- May spawn on daily/monthly tidal cycle or on a diel cycle
- usually after spring tides
Endogenous factors
- endogenous rhythm controls activities of reproduction –> migration + timing of repro, morpholigcal changes, start courtship behaviour
- via hormones & nerves (aka neuroendocrine factor)
- Influenced by ecological factors –> e.g. photoperiod, temp, salinity (e.g. ↓ duration of photoperiod = ↑ melatonin = ↓ gonadotropin prod. = ↓ gonadal activity
Hormone/enzyme produced by pituitary gland + function (fish reproduction)
- Gonadotropins –> e.g. FSH, LH, Gonadotropin release hormones + Gonadotropin release inhibiting factor
- Controls gametogenesis
- Production of sperm/eggs - Steroids –> e.g. 11α-ketotestosterone
- controls vitellogenesis (yolk formation) & spawning
Hormone/enzyme produced by liver + function (fish reproduction)
Insulin-like growth factors (e.g. Igf1)
- Regulates growth
- Gonad development
Hormone/enzyme produced by pineal gland + function (fish reproduction)
Melatonin
- Regulates gonadotropins
- Mediates photoperiodic effect sin the pituitary
Hormone/enzyme produced by bones + function (fish reproduction)
Arginine-vasotocine
- Influence LH release & interfere with production of gonadotropin release hormones
Hormones/enzymes produced by optic gland + function (crustacean reproduction)
- Gonadotropins
- Stimulate gonad development - Gonad-inhibiting hormone
- Inhibits vitellogenesis - Moult-inhibiting hormone (MIH)
- Inhibits MIH
Hormone/enzyme produced by cerebral ganglia + function (mollusc reproduction)
Caudodorsal cell hormone (CDCH)
- Induce ovulation
- Stimulate egg formation
- Induce egg-laying behaviour
List the organ/gland that produces hormones/enzymes that affects reproduction (fish, crustacean, mollusc)
Fish
- Pituitary gland
- Liver
- Pineal gland
- Bones
Crustacean
1. Optic gland
Mollusc
1. Cerebral ganglia
Artificial reproduction
- Process to fertilise eggs with sperm out of natural reproduction timing
- Done by manipulating environmental conditions (exo factors) or injection of hormones (endo factors)
Benefits/function of artificial production
- ↑ frequency of production
- ↑ survival rate of embryos
- Control batch production
Before conducting artificial reproduction:
- Ensure broodstock is well fed & recovered after last spawning
- Ensure optimal water quality parameters 3. separation of males/females whenever possible (diet different)
- Ensure broodstock ready –> gonads mature
- Ensure optimal water quality parameters
During female finfish reproductive cycle
- Presence of bloated belly
- ↑ed aggression
- Livebearers (e.g. guppy) have obvious gravid spot
Once reached maturity (male finfish)
- Stores sperm
Artificial reproduction in fish
- Do not reproduce as well in captive breeding –> stress-induced environment –> ↓es reproductive behaviour & oogenesis
- Stimulation of env. conditions required –> enhancement of diet + control water quality
- Hormonal injection/physical handling at later stage –> stimulate spawning
- Physical handling: stripping (female) & milting (male)
- Eggs & sperm mixed gently in container
Artificial reproduction in molluscs
- Sacrifice indiv. to observe maturity of gonads –> extraction of gametes to view under microscope
- Mainly influenced by temp
- -> ↑er temp = ↑ somatic & gametogenic growth; drop in temp = encourage spawning
Artificial spawning methods (mollusc)
- Temperature exposure
- Aerial exposure
(1. + 2. = stimulate intertidal conditions) - Chemical treatment
Ablation (artificial reproduction in crustaceans)
- Removal of one eyestalk, synchronise with lunar cycle
- X Organ Sinus Gland (XOSG) –> found in eyestalk; contains moult inhibiting hormone (MIH) and gonad inhibiting hormone (GIH)
- Remove XOSG (in eyestalk) releases gonadotropins –> initiate reproduction + exhibit spawning behaviour
Artificial insemination (Crustaceans)
- Mainly shrimps
- Removal of spermatophore from male shrimps
- Insert into female via open thelycum
Climate change & aquaculture
- Climate change = affect salinity & temp
- ↑/↓ in temp influence general metabolism, production; seasonality relative fecundity, no. of spawning
- Fish observed to spawn earlier/later
- Change in reproduction timing = affect overall ecology
- Mismatch b/w seasonality of larvae & zooplankton (food availability)
- High temp amplify impact of hormone-disrupting chemicals (from pollution) –> e.g. long term effects of clotrimazol (chemical), believed to disrupt hormones & interfere w sex ratio = ↓ mate search success & ↑ inbreeding potential
