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Amphibian Reproduction - Anatomy & Physiology (view source)
Revision as of 14:06, 5 July 2012
, 14:06, 5 July 2012→Caecilians (Gymnophiona)
== Introduction ==
= Introduction =
Reproductive behaviour and physiology shows much placicity in amphibians. Gender and breeding season are controlled by genetics, photoperiod, temperature, humidity and food or mate availability.
Reproductive behaviour and physiology shows much placicity in amphibians. Gender and breeding season are controlled by genetics, photoperiod, temperature, humidity and food or mate availability.
= Reproductive Traits =
== Reproductive Traits ==
Amphibian reproduction can by classified by primitive traits that are shared by most fish (Oviparity, Anamniotic Eggs and a Cloaca). They also show derived traits (Metamorphosis, Ovoviviparity and Population Sex Modulation).
Amphibian reproduction can by classified by primitive traits that are shared by most fish (Oviparity, Anamniotic Eggs and a Cloaca). They also show derived traits (Metamorphosis, Ovoviviparity and Population Sex Modulation).
* Both male and female must be present.
* Both male and female must be present.
* Both sperm and [[The_Ovary_-_Oocytes_-_Anatomy_%26_Physiology|oocyte]] contribute to the embryo.
* Both sperm and [[Oogenesis - Anatomy & Physiology|oocyte]] contribute to the embryo.
== Gynogenesis ==
== Gynogenesis ==
* 99% female contribution.
* 99% female contribution.
* Mitosis occurs without separation and meiosis follows.
* Mitosis occurs without separation and meiosis follows.
* Sperm nucleus does not enter the [[The_Ovary_-_Oocytes_-_Anatomy_%26_Physiology|oocyte]] to form the diploid state.
* Sperm nucleus does not enter the [[Oogenesis - Anatomy & Physiology|oocyte]] to form the diploid state.
** Sperm contributes no genetic material to the embryo.
** Sperm contributes no genetic material to the embryo.
* Sperm are only required to [[Fertilisation%2C_Implantation_and_Early_Embryonic_Development_-Fertilisation-_Anatomy_%26_Physiology#Syngamy|activate]] the embryo.
* Sperm are only required to [[Fertilisation - Anatomy & Physiology#Syngamy|activate]] the embryo.
== Parthenogenesis ==
== Parthenogenesis ==
* An asexual form of reproduction found in females where growth and development of embryos occurs without fertilization by males.
* An asexual form of reproduction found in females where growth and development of embryos occurs without fertilization by males.
* 100% female contribution.
* 100% female contribution.
* Self-activated [[The_Ovary_-_Oocytes_-_Anatomy_%26_Physiology|oocytes]] require no contribution from sperm.
* Self-activated [[Oogenesis - Anatomy & Physiology|oocytes]] require no contribution from sperm.
* The offspring produced by parthenogenesis almost always are female in species where the XY chromosome system determines gender.
* The offspring produced by parthenogenesis almost always are female in species where the XY chromosome system determines gender.
= Gonads =
== Gonads ==
== Ovaries ==
=== Ovaries ===
* Produce 1-25,000 [[The_Ovary_-_Oocytes_-_Anatomy_%26_Physiology|oocytes]] at a time.
* Produce 1-25,000 [[Oogenesis - Anatomy & Physiology|oocytes]] at a time.
* Under the influence of the [[Endocrine_System_-_Pituitary_Gland_-_Anatomy_%26_Physiology|pituitary gland]].
* Under the influence of the [[Pituitary_Gland_- Anatomy & Physiology|pituitary gland]].
* [[The_Ovary_-_Oocytes_-_Anatomy_%26_Physiology|Oocytes]] squeeze out into the [[Peritoneal_cavity_-_Anatomy_%26_Physiology|peritoneal cavity]].
* [[Oogenesis - Anatomy & Physiology|Oocytes]] squeeze out into the [[Peritoneal_Cavity_- Anatomy & Physiology|peritoneal cavity (ceolom)]].
* Cilia in the ceolom direct the ova into the infundibulum of the oviduct.
== Female Ducts ==
=== Female Ducts ===
* The oviduct (Mullarian Duct) covers the egg with a jelly-like material.
* The oviduct (Mullarian Duct) covers the egg with a jelly-like material.
* Oviduct and utreter may be united through much of their length.
* Oviduct and utreter may be united through much of their length.
* Open into the [[Exotics_-_Amphibian_Reproductive_Anatomy_and_Physiology_-_Anatomy_%26_Physiology#Cloaca|cloaca]].
* Open into the cloaca.
=== Testes ===
* Located near the [[Urinary System Overview - Anatomy & Physiology|kidneys]].
* Produce sperm under the influence of the [[Pituitary_Gland_- Anatomy & Physiology|pituitary gland]].
* Often a rudimentary [[Ovary - Anatomy & Physiology|ovary]] (known as the Bidder's organ)nearby in the male.
==== Bidder's Organ ====
== Male Ducts ==
* Bidder's organ is a spherical, brownish organ in toads.
* The organ is located just in front of the [[Urinary System Overview - Anatomy & Physiology|kidney]] (mesonephros).
* It is formed at the cranial tip of the male and female gonad during the larval stage.
* Normally it is inactive and contains miniature [[Follicles - Anatomy & Physiology|follicles]] which have the capability to mature (becoming active).
* When the female population is scarce, the Bidder's organ enlarges and produces viable oocytes and then gonadotropins, which stimulate the growth of the Müllerian ducts to form uterus and oviducts.
* Its internal anatomy consists of two parts:
** Central portion: consists of connective tissue and rich in blood vessels.
** Periphery: consists of the cortex, which contains [[Follicles - Anatomy & Physiology|follicles]] in various stages of development.
** Molecules of various proteins are present in the outer layer of the [[Follicles - Anatomy & Physiology|follicles]], homologous to the zona pellucida of the ovum.
=== Male Ducts ===
* Mesonephric ducts carry both sperm and excretory waste.
* Mesonephric ducts carry both sperm and excretory waste.
= Parental care =
== Parental care ==
== Paternal ==
=== Paternal ===
=== Clutch Guarding ===
==== Clutch Guarding ====
* Male stands nearby to guard the clutch until they hatch.
* Male stands nearby to guard the clutch until they hatch.
=== Limb Carrying ===
==== Limb Carrying ====
* Carry the clutch of eggs on their limbs.
* Carry the clutch of eggs on their limbs.
=== Vocal Sac Brooding ===
==== Vocal Sac Brooding ====
* Eggs are laid and fertilised on land.
* Eggs are laid and fertilised on land.
* The male frog guards the eggs until the tadpoles hatch.
* The male frog guards the eggs until the tadpoles hatch.
* He then collects them in his mouth, without swallowing them, and passes them into his vocal sac.
* He then collects them in his mouth, without [[Deglutition|swallowing]] them, and passes them into his vocal sac.
* Fully developed froglets then escape the vocal sac and exit via the frog's mouth to the exterior.
* Fully developed froglets then escape the vocal sac and exit via the frog's mouth to the exterior.
=== Tadpole Carrying ===
==== Tadpole Carrying ====
* Carry tadpoles on their back.
* Carry tadpoles on their back.
== Maternal ==
=== Maternal ===
=== Internal Development ===
==== Internal Development ====
* Ovoviparous species.
* Ovoviparous species.
=== Pouch carrying of the clutch ===
==== Pouch carrying of the clutch ====
=== Epidermal clutch carrying ===
==== Epidermal clutch carrying ====
* Eggs are carried in small pores in the skin (epidermis).
* Eggs are carried in small pores in the skin (epidermis).
* Hatch by bursting through these pores to the exterior.
* Hatch by bursting through these pores to the exterior.
=== Gastric brooding ===
==== Gastric brooding ====
The Gastric-brooding frogs or Platypus frogs were a genus of ground-dwelling frogs native to Queensland in eastern Australia. The genus consisted of only two species, both of which became extinct in the mid-1980s. The genus was unique because it contained the only two known frog species that incubated the prejuvenile stages of their offspring in the stomach of the mother.
The Gastric-brooding frogs or Platypus frogs were a genus of ground-dwelling frogs native to Queensland in eastern Australia. The genus consisted of only two species, both of which became extinct in the mid-1980s. The genus was unique because it contained the only two known frog species that incubated the prejuvenile stages of their offspring in the stomach of the mother.
* This substance has the ability to turn off the production of hydrochloric acid in the stomach. This source of PGE2 is enough to cease the production of acid during the embryonic stages of the developing eggs.
* This substance has the ability to turn off the production of hydrochloric acid in the stomach. This source of PGE2 is enough to cease the production of acid during the embryonic stages of the developing eggs.
** Once the eggs hatch, the tadpoles too create PGE2.
** Once the eggs hatch, the tadpoles too create PGE2.
*** The mucus excreted from the tadpoles' gills contains the PGE2 necessary to maintain the stomach in a non-functional state. *** These mucus excretions do not occur in tadpoles of most other species.
*** The mucus excreted from the tadpoles' gills contains the PGE2 necessary to maintain the stomach in a non-functional state.
*** These mucus excretions do not occur in tadpoles of most other species.
* During the period that the offspring are present in the stomach the frog does not eat.
* During the period that the offspring are present in the stomach the frog does not eat.
* Tadpole development takes at least six weeks, during this time the size of the mother’s stomach continues to increase until it largely fills the body cavity.
* Tadpole development takes at least six weeks, during this time the size of the mother’s stomach continues to increase until it largely fills the body cavity.
* The offspring are completely developed when expelled.
* The offspring are completely developed when expelled.
= Species Differences =
== Species Differences ==
== Frogs and Toads (Anurans) ==
=== Frogs and Toads (Anurans) ===
=== Introduction ===
==== Introduction ====
Once at the breeding ground, male frogs call to attract a mate, collectively becoming a chorus of frogs. The call is unique to the species, and will attract females of that species. Some species have satellite males who do not call, but intercept females that are approaching a calling male.
Once at the breeding ground, male frogs call to attract a mate, collectively becoming a chorus of frogs. The call is unique to the species, and will attract females of that species. Some species have satellite males who do not call, but intercept females that are approaching a calling male.
Most temperate species reproduce between late autumn and early spring. In the UK, most common frog populations produce frogspawn in February, although there is wide variation in timing. Water temperatures at this time of year are relatively low, typically between four and 10 degrees Celsius. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures. More importantly, reproducing early in the season ensures that appropriate food is available to the developing frogs at the right time.
Most temperate species reproduce between late autumn and early spring. In the UK, most common frog populations produce frogspawn in February, although there is wide variation in timing. Water temperatures at this time of year are relatively low, typically between four and 10 degrees Celsius. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures. More importantly, reproducing early in the season ensures that appropriate food is available to the developing frogs at the right time.
=== Mating Calls ===
==== Mating Calls ====
* Mating calls are crucial for most species.
* Mating calls are crucial for most species.
* In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth that distend during the amplification of the call.
* In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth that distend during the amplification of the call.
=== Amplexus ===
==== Amplexus ====
* Amplexus is a form of pseudocopulation in which a male frog grasps a female with his front legs while she lays her eggs. At the same time, he fertilizes them with the fluid containing sperm.
* Amplexus is a form of pseudocopulation in which a male frog grasps a female with his front legs while she lays her eggs. At the same time, he fertilizes them with the fluid containing sperm.
* Some species show cephalic amplexus where the head of the female is held while others show complete lack of amplexus.
* Some species show cephalic amplexus where the head of the female is held while others show complete lack of amplexus.
=== Internal Fertilization ===
==== Internal Fertilization ====
* Only occurs in tailed frogs.
* Only occurs in tailed frogs.
** Not a true tail as found in tadpoles and salamanders.
** Not a true tail as found in tadpoles and salamanders.
=== Spermatheca ===
==== Spermatheca ====
* Organ of the female reproductive tract.
* Organ of the female reproductive tract.
* Sperm can be stored for as long as years!
* Sperm can be stored for as long as years!
== Salamanders and Newts (Caudata) ==
=== Salamanders and Newts (Caudata) ===
Primative salamander families have an Amplexus, but on the whole fertilization is internal.
Primative salamander families have an Amplexus, but on the whole fertilization is internal. Paedomorphosis (the retention of juvenile traits) is common.
=== Spermatophore ===
==== Spermatophore ====
* A packet of sperm with a pedestal to raise it above the ground in ponds.
* A packet of sperm with a pedestal to raise it above the ground in ponds.
* Picked up voluntarily by the female, depending on the success of the male's mating display.
* Picked up voluntarily by the female, depending on the success of the male's mating display.
=== Cloacal Kiss ===
==== Cloacal Kiss ====
* Some salamanders
* Press cloacae together for sperm transfer.
* Creates a water-tight seal so that the sperm is not compromised.
=== Caecilians (Gymnophiona) ===
* Caecilians are the only order of amphibians which only use internal insemination.
* The male caecilians have a penis-like organ, the phallodeum, which is inserted into the cloaca of the female for 2 to 3 hours.
* About 25% of the species are oviparous (egg-laying); the eggs are guarded by the female. For some species the young caecilians are already metamorphosed when they hatch; others hatch as larvae. The larvae are not fully aquatic, but spend the daytime in the soil near the water.
* 75% of the species are viviparous, meaning that they give birth to already developed offspring. The fetus is fed inside the female with special cells of the oviduct, which are eaten by the fetus with special scraping teeth.
** The egg laying species Boulengerula taitanus feeds its young by developing a special outer layer of skin, high in fat and other nutrients, which the young peel off with similar teeth. This allows them to grow by up to ten times their own weight in a week. The skin is consumed every three days, the time it takes for a new layer to grow, and the young have only been observed to eat it at night.
[[Category:Exotic Reproduction]]
[[Category:Bullet Points]]