Parental care in Amphibians

Parental care in Amphibians

In the realm of amphibians, parental care refers to any behaviour exhibited by a parent that enhances the survival prospects of its offspring, as defined by Trivers (1972). Such investment may come at the cost of the parent's ability to invest in additional offspring. Amphibians employ various strategies to safeguard their eggs during early development. This care involves attending to the eggs, transporting eggs or larvae, and providing nourishment to the larvae.

Parental care is typically associated only with species that deposit their eggs in single clusters, rather than those that scatter their eggs in aquatic environments. Nest construction, whether before or during egg deposition, is not classified as parental care. However, in certain species where nests are constructed, one parent may still attend to the eggs. Similarly, while some species retain eggs in the oviducts and provide nourishment to the developing young, this is not considered parental care in the strict sense.

There are various ways by which the parental care is shown in amphibians.

1. Selection of Site: Some amphibians pick safe, damp spots near water to lay their eggs. For example, the Rhacophorus schlegli frog in Japan lays eggs in a hole on muddy river or pond banks, covering them with foamy mucus to keep them from drying out. Gyrinophilus frogs lay their eggs under stones in streams. Sometimes, eggs are carried on the frog's body. Hylodes frogs lay eggs on the undersides of leaves hanging over water. Triton frogs may stick their eggs to underwater plants using a glue-like substance.

2. Making Water Frothy: Rhacophorus maculates frogs create frothy water around their eggs by moving their limbs after laying them. This froth helps prevent the eggs from drying out and makes them harder for predators to spot.

3. Defending Eggs: Green frogs like Rana clamitans males defend their eggs by keeping smaller intruders out of their territory. Mantophryne robusta males hold clusters of eggs in a gelatinous covering with their hands to protect them.

4. Formation of Nests: Some amphibians build nests for deposition of eggs.

1. Mud Nest: Hyla faber frogs dig tiny holes in the mud where they lay and nurture their eggs.

2. Leaf Nest: The South American tree frog Phyllo medusa hypochondrales creates nests by folding and sticking together leaf edges, providing a safe space for their eggs.

3. Shoot Nest: Triton frogs build nests by attaching shoots together using a gel-like substance secreted by their bodies.

5. Direct development: Direct Development: Certain terrestrial or tree frogs, such as Hylodes and Hyla nebulosi, have eggs that hatch directly into small juveniles, bypassing the vulnerable larval stage and reducing the risk of predator attacks and larval mortality.

6. Carrying eggs over the body

i) Coiling Around Eggs: Female Amphuima and Ichthyphis frogs guard their eggs by wrapping their bodies around them until they hatch. In Megalobatrachus, males take on this protective role.

ii) Transferring Tadpoles to Water: Species like Phylobates and Pelobates, found in tropical Africa and South America, carry newly hatched tadpoles in their mouths and transport them to water.

iii) Eggs Glued to the Body: Female Salamander Desmognathus fuscus carry clusters of eggs attached to their bodies. In the Sri Lankan tree frog Rhacophorus reticulates, eggs are glued to the females' bellies. In the European frog Alytes obstericans, males take responsibility for egg care by wrapping them around their hind legs.

iv) Eggs in Back Pouches: Hyla goeldii females carry eggs on their backs. Desmognathus females shelter eggs in underground holes. Pipa pipa females transport eggs on their backs. Cryptobatrachus evansi's dorsal skin has small pockets for egg lodging. Pipa dorsigera's eggs develop in pits on the females' backs, with the dorsal skin becoming soft, spongy, and vascular during breeding.

7. Carrying Eggs on the Body: In Arthroleptis frogs, the larvae are attached to the males and transported from one water body to another.

8. Organs as Brooding Pouches: Male South American frogs of the Rhinoderma darwinii species incubate fertilized eggs in their vocal sacs until they fully develop. In Hylambates breviceps, females carry eggs in their mouth cavity.

9. Viviparity: Salamandra atra and S. maculosa exhibit a unique reproductive behaviour known as viviparity. In this process, eggs are placed inside the uterine cavity where they undergo complete development. The uterine wall functions similarly to a primitive placenta, supporting the development of the embryos.