Species that can Regenerate: From Lizards to Starfish

Context (IE): Recent studies spotlight remarkable regenerative abilities in several animal species, offering insights into survival mechanisms and potential biomedical applications.

Regeneration is the biological process by which organisms regrow lost or damaged body parts such as limbs, organs or tissues. It functions as a survival strategy, enabling species to escape predators, repair injuries and continue reproduction and mobility.

Sharks

Physical Characteristics: Sharks are cartilaginous fish with a streamlined body and sharp teeth.
Regeneration: Exhibits rapid tooth regeneration, replacing thousands of teeth throughout its lifespan.
Behaviour: Sharks are carnivorous predators, using keen senses to track prey.
Habitat: Shallow & deep waters across the world, typically in coastal & open-ocean regions.
Conservation Status: Several shark species are vulnerable or endangered due to overfishing and habitat loss, including the great white and hammerhead sharks.

Also refer to the Pondicherry Shark & the Ganges Shark.

Physical Characteristics: Starfish are marine invertebrates with radial symmetry and five arms belonging to the phylum of Echinodermata.

Regeneration: Can regrow multiple arms and even regenerate an entire body from a single arm.
Behaviour: Starfish move using tube feet on their underside and feed on bivalves like clams.
Habitat: Found in a variety of marine environments, from tide pools to deep-sea regions.
Conservation Status: Sunflower Sea Star: IUCN: CR | Tasmanian Live-Bearing Seastar: IUCN: CR
Threats: Climate change, particularly in warmer waters, but no species is globally endangered.
- Can regrow multiple arms and even regenerate an entire body from a single arm.
- Stores nutrients in limbs to sustain the regeneration process until vital organs like the mouth are reformed.

Source: IUCN

Physical Characteristics: Cylindrical, soft-bodied creatures with leathery skin. Appears similar to cucumber, with small tentacle-like tube feet for locomotion and feeding.
Sea cucumbers are part of a larger animal group called echinoderms, like starfish and sea urchins.

Size: Less than an inch (2.5 centimetres) to over six feet (1.8 meters).
Habitat: Inhabit deep ocean floors, particularly in tropical and subtropical regions.
- Range: Benthic (live on the ocean floor). Larvae are planktonic (float in the ocean currents). Found in virtually all marine environments.
Diet: Scavengers. Feeds on small food items in the benthic zone (seafloor) and plankton floating in the water column. They also eat algae, aquatic invertebrates, and waste particles.
Life span: 5 to 10 years.
Behaviour:
- Both Sexual and asexual reproduction. Eggs undergo external fertilisation. Females release eggs into the water that are fertilised by coming into contact with sperm that males have released.
- Often burrows into the seafloor, scavenging for organic matter.
- Sea cucumbers can confuse or harm predators by propelling their own toxic internal organs from their bodies in the direction of an attacker.
- Uses organ ejection as a defensive distraction tactic against predators like turtles or crabs.

Regeneration: Regrows internal organs within a week as a rapid response to injury.
Threat: Overfishing.
When disturbed, sea cucumbers can expose skeletal hooklike structures that make them harder for predators to eat.
Sea cucumber presence prevent pathogens from sickening co-occurring corals.
Sea cucumbers, scavengers of the seafloor that resemble cylindrical vegetables, have been consumed as a delicacy in Asia for centuries.
Conservation Status: IUCN: LC

Source: IUCN

Physical Characteristics: Slim-bodied amphibians, usually with smooth skin and a long tail.
Regeneration: Capable of regenerating fully functional tails, including spinal cord and nerve tissues. Regenerative process involves migration and specialization of wound-site cells into new tissues.

Behavior: Primarily terrestrial, but some species are aquatic. Known for their ability to absorb moisture through their skin.
Habitat: Found in temperate regions, mostly in moist environments.
Threat: Some species are threatened due to habitat destruction and climate change.
Conservation Status: IUCN: VU

Source: IUCN

Source: IUCN

The axolotl is a species of salamander.
Habitat: The species is found only in Lake Xochimilco, Mexico City.
Physical Characteristics:
- Axolotls exhibit a wide range of colors, including brown, black, albino, golden & spotted varieties.
- Posses feathery gills that protrude from the sides of heads, enabling them to breathe underwater.
- Axolotls don’t have legs when they hatch; they develop them a few weeks later.
Life span: 10–15 years.

Regeneration: Known for complete regeneration of limbs, tail, spinal cord, skin and even parts of its heart and brain.

Behavior: Primarily aquatic, axolotls are nocturnal and prefer slow-moving waters. They are carnivorous and feed on small fish, insects, and invertebrates.
Axolotls are known for their neotenic characteristics, meaning they retain their aquatic larval features throughout their lives.

Physical Characteristics: Small, silvery fish with elongated bodies.
Regeneration: River-dwelling tetras regenerate heart tissue post-injury; cave variants form scars.
Behavior: River tetras are active swimmers, while cave tetras are blind and rely on other senses.
Habitat: River tetras live in fast-moving streams, while cave tetras are found in underground, pitch-black caves.
Conservation Status: IUCN: LC, but some cave-dwelling populations are at risk due to the fragility of their unique habitat.

Source: IUCN

Physical Characteristics: Known for their color-changing abilities, chameleons have zygodactylous feet and elongated bodies.
Regeneration: Regrow limbs and tails following trauma, and can repair damaged nerve tissues.
Behavior:
- Chameleons are arboreal, primarily feeding on insects.
- Their color change is a response to temperature, light, and mood.
- Chameleons’ independently mobile eyes constantly scan separate views, but align forward for stereoscopic vision when hunting.
Habitat: Typically found in tropical forests & woodlands, particularly Madagascar & sub-Saharan Africa.
Conservation Status: IUCN: LC Eg- Asian Chameleon and panther chameleon.

Biomedical Interest: Species like axolotl & Mexican tetra are central to regenerative medicine research.
Evolutionary Insight: Regeneration offers clues on survival priorities, immune system roles, and energy investment in healing.