Whale of a debate put to rest

Date:

Share post:

Researchers have finally settled a decades-long dispute about the evolutionary origins of the pygmy right whale.

The smallest of the living baleen whales, it’s tank-like skeleton is unique, and its ecology and behaviour remain virtually unknown.

Because it is so unusual, the evolutionary relationships of the pygmy right whale (Caperea marginata) have long been a bone of contention.

In a study that solves the debate, just published in Marine Mammal Science, an international group of researchers sequenced the complete genome of Caperea, combining their findings with morphology and palaeontology.

Co-author Dr Felix Marx, curator of marine mammals at the Museum of New Zealand Te Papa Tongarewa explains the skull shape of the pygmy right whale seems to be adapted for skim-feeding, where a whale will swim at the water’s surface with its mouth open to food.

The smallest baleen whale, Caperea marginata, compared to the largest: the blue whale, Balaenoptera musculus [Credit: Carl Buell]

“This is very similar to the larger true right whale, leading some scientists to believe the two whales are closely related, hence their similar names. However, others believe the pygmy right whale is more closely related to species like the blue whale, which take big gulps of water to collect food instead of skimming,” he says.

He was pleased to be able to exploit the power of genomics to elucidate the history of life.

“After 150 years of anatomical orthodoxy and decades of dispute, genomics now shows beyond reasonable doubt that Caperea is a distinct lineage and not related to right whales.

“Like river dolphins and sperm whales, Caperea is the sole guardian of a unique piece of evolutionary heritage. It’s not just another weird right whale — it truly is the last survivor of an otherwise lost family that once played a much bigger role in Earth’s history,” he says.

Co-lead author Dr Kieren Mitchell, of Manaaki Whenua — Landcare Research, says new genetic information often prompts scientists to reconsider why different animals appear more similar or different to each other.

“When DNA and anatomy seem to be at odds about the relationship between species, usually that means there’s an even deeper and more interesting story to be discovered about their evolution,” he says.

Comparative figure image: The skull of Caperea resembles that of right whales because both need to accommodate long baleen plates for skim feeding. Their similarities are the result of convergent evolution [Credit: Felix Marx]

Co-author Dr Nic Rawlence, Otago Palaeogenetics Laboratory Director, describes Caperea as a “wonderful case of convergent evolution,” which occurs when two unrelated species end up appearing more and more alike as they adapt to similar selective pressures.

Caperea has historically been aligned with right whales because they look the same due to similar feeding strategies, when, in fact, it’s probable that Caperea is the last surviving member of an ancient group of whales called cetotheres,” he says.

Co-lead author Dr Ludo Dutoit, of Otago’s Department of Zoology, says now its position in the family tree of whales has been confirmed, researchers can start to explore what the Caperea lineage looks like, and what kind of past events were significant in driving its evolution.

Dr Marx agrees, adding that Caperea may be another example of how being ‘unusual’ helped save a lineage from extinction.

“River dolphins likely survived the demise of their marine relatives because they invaded freshwater habitats; sperm whales persisted when their toothed relatives disappeared because they were deep-diving suction specialists; and Caperea survived because it adapted to be a skim filter feeder, when most of its relatives presumably didn’t.”

Source: University of Otago [July 10, 2023]

ADVERTISEMENT

spot_img

Related articles

Searching for the chemistry of life

In the search for the chemical origins of life, researchers have found a possible alternative path for the...

Compound eyes a continuous feature of evolution

Researchers from Cologne, Tallinn, and Edinburgh have found out that the compound eyes of today's arthropods are still...

Hunting for living fossils in Indonesian waters

The Coelacanth (Latimeria menadoensis) was thought to be extinct for more than 60 million years and took the...

Plant study hints evolution may be predictable

Evolution has long been viewed as a rather random process, with the traits of species shaped by chance...

New evidence emerges on the origins of life

In the beginning, there were simple chemicals. And they produced amino acids that eventually became the proteins necessary...

Spawn of the triffid? Tiny organisms give us glimpse into complex evolutionary tale

Two newly discovered organisms point to the existence of an ancient organism that resembled a tiny version of...

First sequence of the Komodo dragon genome reveals clues about its evolution

The Komodo dragons are the largest lizards in the world. These predators weighing up to 200 pounds can...

New insights on link between genetic mutations and biological evolution

From the longer-beaked Galapagos Island finches studied by biologist Charles Darwin – which enabled them to more effectively...