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New Deep-Sea Discovery: The Elusive Bathydevius caudactylus

In an extraordinary encounter with the deep ocean, scientists have unveiled a new species of sea slug, Bathydevius caudactylus, that inhabits the “midnight zone,” a region of the ocean where sunlight is absent. This creature was first observed in February 2000 at a depth of 8,576 feet in the Pacific Ocean using a remotely operated vehicle near central California.

The creature, nicknamed the “mystery mollusk” due to its unfamiliar appearance, intrigued ecologists. As Bruce H. Robison, an expert from the Monterey Bay Aquarium Research Institute, remarked, it seems as if it comprises “spare parts left over from making a bunch of other animals.”

Following that initial sighting, researchers embarked on an expedition to find additional specimens of B. caudactylus. Their efforts led them back to Monterey Submarine Canyon and extended their searches up to Oregon and into the Mariana Trench, ultimately observing 157 individuals. Many of these were found between 3,300 and 10,700 feet deep, adapting to water temperatures around 36 degrees Fahrenheit, while some thrived even deeper, at approximately 13,150 feet.

To understand the creature’s characteristics, researchers conducted DNA sequencing on several B. caudactylus samples. The findings revealed that this species belongs to an entirely new family of nudibranchs, popularly known as sea slugs. This revelation is significant, given that the ocean’s depths are not a common habitat for nudibranchs, indicating a remarkable evolutionary adaptation.

The anatomy of B. caudactylus is striking: it boasts a gelatinous, transparent body, a bell-shaped hood, a fringed tail with multiple finger-like appendages, and a short foot for maneuvering. Its vibrant red stomach and orangish-brown digestive gland are visible, lending to its ethereal appearance. The creature uses its hood effectively to trap shrimp, resembling the capturing method of a Venus flytrap.

When faced with potential threats, B. caudactylus employs strategies to escape detection. It predominantly relies on its transparency to remain inconspicuous, but it can also use bioluminescence to startle predators, occasionally shedding its tail appendages to mislead attackers.

Interestingly, B. caudactylus is hermaphroditic, possessing both male and female reproductive organs, a trait that may enhance mating success in the sparse deep-sea environment, though instances of observed mating remain unrecorded. This dual-gender characteristic allows the species to anchor itself during egg-laying at the seafloor, increasing reproductive opportunities.

The variety of nudibranchs is extensive, with approximately 3,000 identified species exhibiting a range of shapes and colors. Many use their pigmentation for camouflage or as a warning to potential predators, with some capable of adopting defenses from their prey. Nudibranchs typically feed on jellyfish, sponges, and other invertebrates, while some species exhibit cannibalistic behavior. While two other nudibranchs utilize similar feeding methods, they are distantly related to B. caudactylus, suggesting that this particular hunting strategy may have evolved independently.

This recent discovery of B. caudactylus underscores the vast unknowns of marine biology, particularly regarding deep-sea ecosystems. According to Steven H.D. Haddock, a marine biologist at MBARI, the findings highlight the necessity of advanced technologies for examining and cataloging these remote environments. As researchers delve deeper into oceanic studies, the insights gained will be crucial for informed ocean management and conservation efforts.

Source
www.smithsonianmag.com