• internal fertilization
• small number of large young
• protection within mother

• large number od eggs and sperm
• external fert- oviparous
• small amount of yolk
• larval phase
• increased mortality

• used by all elasmobranchs
• ensures energy is passed to embryos and is not wasted
• increased fertilization success

• yolk is digested by enzymes and transfered to circulatory system
• yolk platelets are moved into the fetal digestive system

• egg laying- retain eggs for short time and then deposit in substrate

• live birth- retain embryos until they are fully developed; give birth to live young

• relatively large eggs
• enslose embryos in tough egg cases; females pick substrate location
• once deposited, no further parental care, nurished by yolk
• incubation ranges from a few months to a year

oviparity

(cont)

• typically small and benthic- littoral or benthic in habitat
• young are small- related to amount of nutrients in yolk
• heterodontidae, scyliorhinidae, orectobolidae, and rajiformes
• most ancestral in sharks

• embryos retained in uterous for whole development
• aplacental or placental

• 4 function groups

1. yolk dependency
2. oophagy
3. adelophagy
4. placental analogues

• squaliformes, hexanchiformes, squatiniformes, orectolobiformes, carcharhiniformes, primitive batiods
• embryos depend on yolk
• retained in uterus until birth
• small at birth
• allows mother to select optimal area for birth
• less predation

• lamniformes
• ovaries grow to tremendous size (>5 Kg)
• eggs usually small
• embryos dependant on yolk for short period
• about 5 cm- start to ingest eggs
• precocial teeth allow them to rupture eggs

• sand tiger; releases 12 fertilized eggs
• when largest reaches 10-12 cm is seeks and kills other embryos
• as embryo grows it consumes siblings
• develope large protruding yolk stomachs
• large size

• myliobatiformes
• regions at the uterine epithelium secrete a nutritive "uterine milk" or embryotroph or histotroph- more nutrition than yolk
• produce few, large young
• short gestation- 2-4 months

• most carchariniformes
• nurished by yolk sac initially
• yolk connect to uterine wall- formes placenta
• unlimited supply of nutrients
• hematrophic transfer is majority of nutrition
• each embryo is compartmentalized in the mother: egg envolope encased young
• most reproduce biennually (every other year)
• hammerhead and sharpnose are annually

• paired, symmetrical structuressituated at the anterior end of the body cavity
• some species, embedded in epigonal organ
• enlarge during breeding season and regress during other times
• *mature when: claspers longer than pelvics, calcified, rotate 180 degrees
• *siphon sacs: thought to aid in movement of sperm

• diametric: carcharinidae and sphyrnidae
• radial: lamniformes
• compound: batiods

• production of sperm; testes
• sperm stored in epididymis and ductus defrons
• sprem usually encased in packet called sprem packets (spermatophores); protect sperm from sea water

• ovaries: generation of eggs, acquisition and accumulation of yolk
• biosynthesis and secretion of hormoes
• *mature when oviduct not embedded in dorsal wall
• *Nidimental gland: along the oviduct; where sperm is stored and eggs fertilized

• paired or single structureslocated anteriorly in body cavity
• both ovaries are functional in anscestrial formes and one is functional in derived forms; right ovary
• vary in size depending on sexual condition
• may be embedded in epigonal organ

ovaries

(cont)

• 2 types

1. external
2. internal

• carcharinids
• compact or naked
• produces few, large eggs

• lamnids
• produces countless eggs
• fedd developing embryos

• shell or oviduct gland
• secretes an egg membrane or shell that encloses egg
• sperm storage
• doubles in size immediately before fertilization

• sole functions if to transprt eggs
• paired, tubular
• ostrim- anterior portion: forms a funnel close to ovaries
• eggs: release into body cavity and are collected by the ostium and are transported to the nidimental gland

oviducts

(cont)

• uterus: posterior portion of oviduct
• vagina: posterior to uterus

• evidence in carcharhiniformes; no evidence in lamniformes
• ranges from 4 weeks to a year
• some species may have the ability to store sperm for longer periods

• encompasses ovarian cycles and gestation period
• ovarian cycle: how often a female develops a batch of eggs
• gestation period: length of time between fertilization and paturation

annual

concurrent cycle

• give birth and mate in same year
• mates right after giving birth
• sharpnose & hammerheads

biennual

consecutive years

• give birth one year, rest the next year
• most carcharhinids
• scientist have made assumptions w/many species and now how to reexamine

• bonnethead: 4 months
• spingy dogfish: 2 years

• reduced predation
• increased predatory efficency
• reduces # of competitors
• increased swimming efficency = increased survival