Friday, July 12, 2019

The White-Spotted Pufferfish

Pufferfish hiding in sediment, seen near
bottom of the photo. Credit: HIMB/R. Nunley
On our snorkel adventure this past week, LiAn and I came across what looked like to be a moving rock. As we got closer, we noticed it had eyes and fins. We then realized it wasn’t a rock at all and that it was a small pufferfish.

This pufferfish you see hiding in the sediment to the right is called a white-spotted pufferfish (Arothron hispidus). The spots may be hard to see which is why they are also commonly called the Stripebelly Puffer. Its Hawaiian name, O’opu hue means stomach like a gourd (Titcomb, 1972). O’opu hue is a great name for pufferfish because they are known to expand their stomachs with water and form a gourd shape with their bodies. They do very well hiding on the seafloor. As you can see in the picture, they are covered in sand and camouflage with the floor beneath them making it almost impossible to see at first glance.

Stripebelly puffer. Credit: Keoki Stender
The white-spotted puffer belongs to the family Tetraodontidae. The name Tetraodontidae comes from a chemical that many pufferfish have in their body called tetrodotoxin. It can be found in many marine animals including porcupine fish, triggerfish, and sunfish. It can be found in organisms living on land too. For example, the rough-skinned newt, Taricha granulosa has tetrodotoxin in their skin, ovaries, and in their muscles as well. Some predators of the rough-skinned newt, such as the garter snake (Thamnophis spp.) has a resistance to this toxin in order to continue preying on the newt (Mebs et al, 2019). The bacteria living in these animals create this neurotoxin making the pufferfish and newt poisonous to most predators, including humans (Bragadeeswaran et al, 2010). Tetrodotoxin is found mainly in the puffers skin and in little sacs throughout the body. A human has to ingest only a few milligrams of tetrodotoxin for it to be deadly (Bragadeeswaran et al, 2010). This toxin is not their only defense mechanism though. Like all puffers, the white-spotted puffer inflates and can blow up like a balloon if threatened. They do this by sucking in a lot of water quickly and expanding their stomach to become a spherical shape. This confuses predators and makes them much more difficult to consume. This can be dangerous for the pufferfish because stretching out their stomach and skin constantly makes it much more difficult to swim around. Once they are blown up, they can only float around in the water until they return to their normal size. With all of the self-defences the puffer has, it doesn’t use all of them at once. First, the pufferfish will blend in with the sediment or rocks below and camouflage itself to the best of its ability in hopes of not being seen. If the puffer is unsuccessful in hiding and gets spotted by a potential predator, the puffer will then puff up and hope that the predator is too lazy to try and figure out how to fit it in its mouth. If puffing up into a big ball doesn’t work, the puffer will take one for the team and hopefully kill or harm the predator with the toxins as it’s getting consumed.
Jaw and teeth of the closely related
spiny pufferfish. Credit: HIMB/R. Nunley

The white-spotted puffer feeds on algae, mollusks, sponges, corals, crabs, sea stars, and sea urchins (Randall, 2005). The pictures you see to the right are pictures of a pufferfish jaw. As you can see, all of their teeth are fused together to form a single plate. This beak-like jaw helps the pufferfish grind and crush its prey. This is why puffers are able to eat corals, mollusks, and sea urchins. Its diet includes organisms with tough outer shells or skeletons and by having this jaw shape and type, they are able to feed on what they like best.

You will most likely find the white-spotted puffer around the Hawaiian islands, Indo-Pacific, and French Polynesia. We found this white-spotted puffer on the south-west edge of Moku o Lo’e about 4-5 feet deep. They are very common in Hawaii and Kane’ohe Bay. These pufferfish may look cute and fun to play with, but they can easily bite off a finger, so admire their beauty from a respectful distance.

- Rachel

Bragadeeswaran, S, Therasa, D, Prabhu, K, & Kathiresan, K. (2010). Biomedical and pharmacological potential of tetrodotoxin-producing bacteria isolated from marine pufferfish Arothron hispidus. Journal of Venomous Animals and Toxins including Tropical Diseases.
Mebs, D., Yotsu-Yamashita, M., & Toennes, S. W. (2019). Tetrodotoxin content of Rough-skinned Newts, Taricha granulosa (Salamandridae), from their northern distribution range, British Columbia, Canada, and Southeast-Alaska, USA. Salamandra
Randall, J. E. (2005). Reef and Shore Fishes of the South Pacific: New Caledonia to Tahiti and the Pitcairn Islands. China: Library of Congress Cataloging-in-Publication Data. 
Stender, K. (n.d.). Stripebelly Puffer, Arothron hispidus: Fish Hole, Midway Atoll, 40 feet [image].
Titocomb, M. (1972). Native Use of Fish in Hawaii. Honolulu: The University Press of Hawaii.

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