A new type of dolphin has evolved in the Pacific Ocean

Researchers have identified a new subspecies of common bottlenose dolphin found only in the tropical regions of the eastern Pacific Ocean.

An analysis of several specimens by Ana Costa, a marine researcher at the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Sciences, and colleagues found that the new subspecies is smaller than other common bottlenose dolphins.

In a study published in the Mammalian Evolution Magazinethe scientists named the new subspecies Eastern Tropical Pacific (ETP) bottlenose dolphin, or Tursiops truncatum nuuanu in scientific terms.

Common bottlenose dolphins are found in temperate, subtropical, and tropical oceans. worldwidewith a world population estimated at around 600,000 individuals.

A new common subspecies of the bottlenose dolphin
The new common subspecies of the bottlenose dolphin, known as the eastern tropical Pacific bottlenose dolphin (Tursiops truncatus nuuanu). This subspecies is smaller than other common bottlenose dolphins.

These dolphins, which are highly intelligent creatures, grow to between 6.5 and 13 feet in length and can weigh more than 1,000 pounds. Its name is a reference to its short, thick snout, or rostrum.

While the common bottlenose dolphin is considered a single species (truncated tursiops), in some locations, scientists have observed distinct populations that have different ecological and habitat preferences.

coast said news week these differing preferences can lead to differences in genetics or form, potentially separating populations found in the same region into what scientists call ecotypes (a distinct population of a species that is adapted to local conditions) and even leading to speciation, the evolutionary process by which populations evolve to become distinct species.

For example, Costa and colleagues from the National Oceanic and Atmospheric Administration (NOAA)—Patricia Rosel of the Southeast Fisheries Science Center (SEFSC) and Eric Archer of the Southwest Fisheries Science Center (SWFSC)—showed in previous research that two ecotypes of The bottlenose dolphins that live along the US Atlantic coast were different enough in genetics and shape to be described as distinct species.

Based on their findings, the scientists proposed that an ecotype of the US Atlantic bottlenose dolphin, which prefers shallow water, be recognized as a new species, Tursiops erebennus (Tamanend’s bottlenose dolphin), while the other, which tends to be found in deeper waters, offshore, is still known as the globally distributed dolphin. truncated tursiops (common bottlenose dolphin).

Along the US Pacific coast, more specifically along the California coast, two common ecotypes of bottlenose dolphins have been identified, Costa said. Previous studies in the eastern Pacific Ocean, including in California, revealed differentiation between populations of common bottlenose dolphins. However, these were carried out in localized areas.

A distinct form of bottlenose dolphin was also suggested for the eastern tropical Pacific in the early 20th century, but it was based on only a few specimens and field records, according to the researcher.

“Therefore, despite previous studies in the area, it was necessary to better characterize the level of differentiation between these different populations and determine if there was, in fact, a distinct form of bottlenose dolphin in the eastern tropical Pacific.” Costa said.

To do this, Costa, Rosel and Archer collaborated with the late SWFSC researcher William Perrin, who passed away in July this year, to conduct a larger study with the aim of better understanding the taxonomy of common bottlenose dolphins in this region. . .

For him Mammalian evolution In the paper, the researchers examined the skulls of more than 130 bottlenose dolphin specimens from the eastern Pacific and western North Pacific, off the coast of Japan, which are in museum collections across the United States. In some cases, the team also looked at the full body length of these specimens.

A pair of common bottlenose dolphins ETP
A pair of bottlenose dolphins from the Eastern Tropical Pacific (ETP). These dolphins likely have a preference for deeper waters offshore between southern Baja California and the Galapagos Islands.

Their analysis revealed significant differences in shape between Pacific bottlenose dolphins, looking at two distinct groups.

“The bottlenose dolphins found in the waters off the eastern tropical Pacific coast formed a single group, and were significantly smaller, based on skull and body length, than the common bottlenose dolphins that form the other group. group,” Costa said. “Our findings indicated that offshore bottlenose dolphins of the eastern tropical Pacific are diverging from globally distributed common bottlenose dolphins and should be described as a separate subspecies.”

The new subspecies is restricted to the eastern tropical Pacific and probably has a preference for deeper waters offshore between southern Baja California and the Galapagos Islands.

Costa said that the differentiation of ETP bottlenose dolphins from other common bottlenose dolphins could be a result of the environment they occupy. For example, different environmental conditions in the eastern tropical Pacific and possible variations in feeding behaviors may be influencing differentiation.

“This subspecies is one of the smallest common bottlenose dolphins ever found,” Costa said. “Dolphins are a charismatic fauna, and it is common for the public to think that all dolphin species are already known. However, with the improvement of technologies and the integration of different methodologies, as well as the increase of samples from different areas, greater biodiversity. has been revealed in more recent years.”

The results of the latest study could have implications for protecting these animals.

“By better understanding the biodiversity in the ocean, we can better understand the relationship of dolphins with their environment and the threats they face, and in this way better define conservation and management strategies,” said Costa.

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