South American Lungfish:A Living Fossil with largest Genome

SOUTH AMERICAN LUNGFISH

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Context

Recent analyses revealed that the South American lungfish genome grew massively during the past 100 million years.

South American Lungfish

The South American lungfish is an extraordinary living fossil.
It has been around for over 400 million years, making it the nearest living relative to the first land vertebrates.
It closely resembles its primordial ancestors from the Devonian period.

Habitat and Distribution

This freshwater species, known as Lepidosiren paradoxa, inhabits slow-moving and stagnant waters.
It is found across several South American countries, including Brazil, Argentina, Peru, Colombia, Venezuela, French Guiana, and Paraguay.
These environments are typically low in oxygen, where the lungfish's ability to breathe air is a significant advantage.

Genomic Marvel

The South American lungfish also boasts the largest genome of any animal.
Scientists have sequenced its genome, which is about 30 times larger than the human genome.
This immense genetic blueprint provides insight into the lungfish's complex evolutionary background and adaptations.

Category	Details
Scientific Name	Lepidosiren paradoxa
Common Names	South American lungfish, American mud-fish, scaly salamanderfish
Habitat	Swamps and slow-moving waters of the Amazon, Paraguay, and lower Paraná River basins in South America
Family	Lepidosirenidae (some authors include Protopterus in this family)
Brazilian Names	piramboia (snake-fish), pirarucu-bóia, traíra-bóia, caramuru
Taxonomy	Closely related to African lungfishes (family Protopteridae); both families diverged during the Early Cretaceous. Some papers suggest classifying both within Lepidosirenidae, but commonly distinct families.
Description	Immature lungfish: spotted with gold on a black background; adult: fades to brown or gray. Fused tooth-bearing bones, autostylic jaw suspension, elongated body, reaches 125 cm (4.10 ft). Thin pectoral fins, larger pelvic fins. Gills reduced in adults.
Feeding Habits	Juveniles: insect larvae and snails. Adults: omnivorous, including algae and shrimp, using heavily mineralized tooth-plates.
Adaptations	Burrows into mud during dry season, creating a chamber with holes for air. Produces a mucus layer to retain moisture and slows metabolism.
Reproduction	Mates during rainy season. Builds a nest with highly vascularized pelvic fins for oxygen enrichment. Young have external gills and become air-breathing at about seven weeks.
Fossils	Fossils found between 72 and 66 mya, during the Maastrichtian stage of the late Cretaceous.
Genome	As of August 2024, L. paradoxa has one of the longest genomes (91 billion bases, 30 times larger than the human genome). Marbled lungfish has the largest genome (130 billion bases). Low levels of PiRNA, which suppresses transposon activity, might contribute to its large genome.

The South American lungfish (Lepidosiren paradoxa) has an IUCN Red List status of Least Concern (LC). It is not evaluated by CITES or CMS. The South American lungfish is also considered harmless to humans.

PRACTICE QUESTION

Q. Consider the following statements about the South American lungfish:

1. It is a living fossil and closely resembles its primordial ancestors from the Devonian period.

2. It is found exclusively in high-oxygen environments in South America.

3. It has the largest genome of any animal, approximately 30 times larger than the human genome.

Which of the above statements is/are correct?

A) 1 and 2 only

B) 1 and 3 only

C) 2 and 3 only

D) 1, 2 and 3

Answer: B) 1 and 3 only

SOURCE: THE HINDU