A newly discovered species of jellyfish, sporting a remarkable 24 eyes, has been identified by researchers in Hong Kong’s Mai Po Nature Reserve. The tiny creature, scientifically named Tripedalia maipoensis, was found in a shrimp pond and represents the fourth known member of its family. This revelation highlights the ongoing biodiversity hidden within even well-studied ecosystems and underscores the importance of continued marine research in the region.
Researchers in Hong Kong have discovered a new species of jellyfish possessing 24 eyes, named Tripedalia maipoensis, in a shrimp pond within the Mai Po Nature Reserve. The tiny creature, measuring only about half an inch in diameter, is difficult to spot in the murky pond water.
The finding adds a fourth described member to the Tripedaliidae family, a closely related group of box jellyfish. Box jellyfish, as a whole, represent a small group of cnidarians, with only 49 known species worldwide to date.
The research was led by Professor Qiu Jianwen of Hong Kong Baptist University (HKBU), a marine biologist who monitors the response of coastal ecosystems to change. His research focuses on marine invertebrates, animals without backbones that live in the sea.
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Professor Qiu’s team sampled the shrimp ponds, located between mangrove forests and open estuaries, during nighttime expeditions from 2020 to 2022. These ponds are refreshed by tidal waters as the freshwater rivers meet the sea in the coastal area.
The water is brackish, a mix of freshwater and slightly salty seawater. Within this brownish-green mixture, the transparent jellyfish can easily slip through nets unless observed very carefully.
Tripedalia maipoensis possesses an almost colorless, transparent bell with a rounded cube shape. The bell reaches approximately six-tenths of an inch from top to bottom, allowing the animal to remain concealed among plant stems.
Extending outward from each corner of the bell are three flat, muscular pads – the pedalia – which anchor the tentacles and help propel the jellyfish through the water. A single tentacle, reaching up to four inches in length, hangs from the tip of each pad.
As the bell contracts and relaxes, a thin sheet of muscle – the velarium – partially covering the opening, helps focus the jet of water behind the jellyfish. Tripedalia maipoensis uses this focused propulsion to swim faster than many other jellyfish, which drift with weak pulsations.
To confirm this was a new species, the team examined specimens under a microscope, finding several similarities to its Caribbean relative, Tripedalia cystophora, but with key differences. The new species has three pedalia at each corner of the bell, only one tentacle on each pad, and branching canals in its velarium.
Beyond physical appearance, scientists constructed a phylogeny – a family tree showing the relationships between species – using DNA from several genes. This comparison placed Tripedalia maipoensis alongside Tripedalia cystophora, confirming they are close cousins rather than the same species.
Key data came from rRNA, a genetic material frequently used to compare species. On the 16S rRNA gene, Tripedalia maipoensis differed from Tripedalia cystophora by approximately 17.4 percent, a significant difference supporting the designation of a new species.
Like its close relatives, Tripedalia maipoensis carries 24 eyes arranged in four groups on structures called rhopalia. These rhopalia, sensory clubs each housing a group of eyes, hang slightly below the edge of the bell.
Within each group, two larger lens eyes – image-forming eyes with small lenses – handle most detailed vision. The remaining four pit and slit eyes are simpler organs primarily tracking light and dark rather than sharp shapes.
In experiments with Tripedalia cystophora, scientists found that some upward-facing eyes help the jellyfish remain beneath mangrove canopies. These eyes continuously orient towards the world above the water, providing sufficient visual guidance for the animal to avoid roots and other obstacles.
Tripedalia maipoensis has a similar arrangement of eye types, suggesting it may also use specific eyes for tasks such as hunting and navigation. Researchers still need to test precisely how the new species responds to light and shadow in its muddy pond habitat.
Despite their simplicity, box jellyfish exhibit surprising behavior for such small and soft creatures. They can swim quickly, avoid obstacles, and maintain position in patches of sunlight where small crustaceans gather.
Recent learning experiments with Tripedalia cystophora have shown that these jellyfish can alter their swimming behavior after encountering an obstacle. This behavior aligns with associative learning, a process where animals connect experiences with subsequent actions.
Tripedalia cystophora lacks a single brain, but possesses a central nervous system – a network coordinating signals from its eyes and muscles. Given the close relationship, scientists suspect that Tripedalia maipoensis may possess some of these learning capabilities once tested directly.
Tripedalia maipoensis is the first box jellyfish officially reported from the coastal waters of mainland China, altering the global range map of this group. Its habitat in managed shrimp ponds alongside a bustling city also demonstrates that human-shaped landscapes can still conceal unnamed species.
For conservationists, each new species adds to local biodiversity, the full variety of living organisms within an ecosystem. Discovering an additional species in a well-studied nature reserve like Mai Po leads scientists to suspect that more secluded wetlands may harbor even more life. The study was published in the journal Zoological Studies, according to Earth.com.
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