Reproduction

Gonochroistic

• born sperm or egg producing and maintain status throughout entire life

Heterogametic

• sexes are assigned by differing chromosomes

• XY: sperm producing (heterogametic)

• XX: egg producing (homogametic)

• fishes do not have gender

GSD/GSD+ESD/ESD

• GSD: sex determining gene on sex chromosomes (trout and pufferfish (XX/XY), yellowtail and tongue sole (ZZ/ZW)

• GSD+ESD: sex determining genes and sex changing environmental factors (flounder and eel) GSD+ESD)

• ESD: sex changes in environmental factors (mangrove rivulus (simultaneous; both M/F) clownfish and grouper (either M→F or F→M)

Dioecious

• one sex for life

• sperm producing or egg producing

Hermaphrodites

• interchangeable between M and F

• simultaneous or sequential

Protogyny

• starts as females turns to male (wrasses)

• Monandric: males develop only from females (one pathway)

• Diandric: males can develop from females or directly from juvenile males (two pathways)

Protandry (clownfishes)

• start as males turns to female

Hormone used: androgen

Oviparous (flying fish)

• eggs fertilized inside or outside but laid outside by female

Ovoviviparous (mosquitofish)

• fertilized egg inside mom and hatch inside

Viviparous (sharks)

• direct physical connection with mom, born in womb. like humans, no egg hatched or needed

Parthenogenesis

• Gynogenetic: Form of asexual reproduction, may or may not require sperm. maternal genetic material only meaning males do not pass down DNA

• Hybridogenentic (aka parasitism): reproduction between different species. uses male genetic material for the offspring's body but discards it when creating her eggs, transmitting only the mother's genome and is renewed by mating with another male corresponding species.

Spawning

• eggs and sperm released or deposited into water and are fertilzed by other animals

Sexual parasitism (angler fish)

• relationship in which one sex benefits and the other is harmed

• male fishes bite onto females and latches on fusing tissues and shares one circulatory system

Brooding

• Mouth: fertilized eggs are carried and incubated in thevparent's mouth. (cuckoo cichlid)

• Head: fertilized eggs are carried on a supraoccipital hook on the male’s head (nursery fish)

• Pouch: is a sac or cavity in an animal's body where eggs or embryos are received and developed (seahorse)

• Nest: eggs are laid in nests and kept there until they hatch, nest guarding (usually by males) occurs in marine and anadromous fishes but is most common in freshwater species. (betta fish - bubble nest)

Harems vs satellite males

• Harem males: Polygyny group of fishes, where there is one harem male, usually significantly larger than the females, and multiple females within the group. If the male is removed from the harem, the largest female may begin courting the other females and develop male organs. Low genetic diversity if 1 male

• satellite males: non-territorial males that adopt an alternative mating strategy, positioning themselves near dominant territorial males to intercept females and fertilize eggs

Breeding tubercles

• Appear as either partial or fully keratinized cells in particular regions on males. Used to stimulate females during reproduction. Development of stimulated by hormones.

Intermittent organs

• Gonopodium - modified anal fin that can allow a male hook onto a female before releasing sperm

• Priapum - located under the chin, a combination of the pelvic girdle, postcleithrum, and pectoral pterygial elements in males are used to hold onto the female while fertilizing eggs before they are released

Sperm storage

• When males mate with a single female, this female is able to store sperm for long periods of time (female bamboo sharks)

• This offers females the option to fertilize eggs in optical conditions

• This allows males it allows for passing of genes

Sexual Dimorphisms

• Coloration: (Betta Fish) Male betta fish are much more vibrant than females of the species showing a wide variety of coloration.

• Size and Shape-Angler Fish: Female angler fish are much larger in size compared to the males (60 times the length). Males may find difficulty in finding food and their alimentary canals of some males be stunted.