For whales, study shows gigantism is in the genes
Send a link to a friend
[January 20, 2023]
By Will Dunham
WASHINGTON (Reuters) - The blue, fin, bowhead, gray, humpback, right and
sperm whales are the largest animals alive today. In fact, the blue
whale is the largest-known creature ever on Earth, topping even the
biggest of the dinosaurs.
How did these magnificent marine mammals get so big? A new study
explored the genetic underpinnings of gigantism in whales, identifying
four genes that appear to have played crucial roles. These genes, the
researchers said, helped in fostering great size but also in mitigating
related disadvantageous consequences including higher cancer risk and
lower reproductive output.
Cetaceans, the marine mammal group encompassing whales, dolphins and
porpoises, evolved around 50 million years ago from vaguely wolf-like
land-based ancestors that belonged to a mammalian assemblage called
artiodactyls that includes today's cows, pigs, sheep and many others.
"Body size is a complex result of many genes, pathways, and physical and
ecological processes," said geneticist Mariana Nery of Universidade
Estadual de Campinas (UNICAMP) in Brazil, co-author of the study
published on Thursday in the journal Scientific Reports. "Our results
are among the first to study gigantism in cetaceans from a molecular
perspective."
The study focused on seven whale species exceeding 33 feet (10 meters)
long. Six are baleen whales, which consume tiny prey using a mouth
filter-feeding system involving baleen plates made of the same substance
found in people's fingernails. The sperm whale is a toothed whale that
hunts large prey like giant squid.
Blue whales can reach about 100 feet (30 meters) long, fin whales about
80 feet (24 meters), sperm and bowhead whales about 60 feet (18 meters),
humpback and right whales about 50 feet (15 meters) and gray whales
about 45 feet (13.5 meters).
After assessing nine genes including some associated with increased body
size in other mammals, the researchers found that four - named GHSR,
IGFBP7, NCAPG and PLAG1 - appear to have gained prominence during the
evolution of large whales.
GHSR is a gene involved in releasing growth hormone through the
pituitary gland, body weight, energy metabolism, appetite and fat
accumulation. It also is associated with controlling cell proliferation
and programmed cell death. Tumors essentially are formed by runaway cell
growth.
[to top of second column]
|
![](../images/012023PIX/news_h89.jpg)
A humpback whale is seen near the coast
of Mazatlan January 17, 2012. REUTERS/Stringer
IGFBP7 is a gene involved in promoting cell growth and division.
There is evidence it acts as a cancer suppressor in prostate,
breast, lung and colorectal tumors.
NCAPG, a gene associated with growth in people, horses, donkeys,
cattle, pigs and chickens, is linked to increased body size, weight
gain, cell proliferation and cell life cycles.
PLAG1, a gene associated with body growth in cattle, pigs, and
sheep, is involved in embryo growth and cell survival.
"Gigantism in the current cetacean lineage is recent, estimated at
approximately 5 million years ago. Before that, there were animals
with large sizes, like Basilosaurus, but these were exceptions, and
most cetaceans did not exceed 10 meters in length," said study lead
author Felipe Andre Silva, who worked on the research while earning
his master's degree in genetics and molecular biology at UNICAMP.
"Gigantism may bring some advantages such as a lower chance of being
preyed upon and a greater chance of obtaining food," Silva added.
Basilosaurus, a toothed apex predator from about 40 million years
ago, was the largest-known early whale. The baleen whale lineage
dates to roughly 36 million years ago, starting modest in size.
"The evolution of cetaceans is a fantastic story, as these huge and
charismatic animals attract the attention of many people," Nery
said. "But beyond the curiosity it arouses, these animals can teach
us a lot about the evolutionary process itself. And whales have
proven to be a very interesting model to understand how biodiversity
is generated and help answer fundamental questions in evolutionary
biology."
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
[© 2023 Thomson Reuters. All rights
reserved.]This material may not be published,
broadcast, rewritten or redistributed.
Thompson Reuters is solely responsible for this content. |