Some tropical and subtropical coral reefs are home to a rather strange fish. A fearless species that does not escape🏃 when facing danger but instead showing slow and clumsy movements. Its appearance also contrasts with most streamlined fish species, presenting a near-square📦 shape and several protruding "horns" » This is the Horned Boxfish, 𝘓𝘢𝘤𝘵𝘰𝘳𝘪𝘢 𝘤𝘰𝘳𝘯𝘶𝘵𝘢 (Linnaeus, 1758) and we’ll discover that beneath its odd appearance lies "tough & toxic" defense mechanisms.
Spreading from the coasts of Japan to those of Australia or from Hong Kong to the South African waters of the Atlantic Ocean, this species has colonized vast areas🏝. The bright yellow or olive-colored bodies scattered with white and blue-black spots; coupled to its box-like shape makes this fish quite conspicuous. Adult Boxfishes are usually solitary and territorial🐟, while juveniles typically live in small groups attached to stag-horn corals. Young individuals have a rounder body shape, gradually becoming more squared as they mature, with their horns elongating with age. Boxfishes primarily feed on algae, coral polyps, zooplankton, and crustaceans. When hunting, they can jet streams of water💦 into muddy or sandy seabeds to uncover small invertebrates hidden beneath.
The Horned Boxfish, also known as the "Cowhorn fish," derives its name from the two long "horns" on its head🐃. These horns are slender, bony protrusions like "bone spurs" that actually break off quite easily, but can regrow over a period of time. Their scales are hexagonal-shaped and tightly connected; with research suggesting that the collagen fibers in the Longhorn Boxfish's scale armor give them exceptional flexibility and toughness, providing a higher level of defense compared to other species🛡️. Beneath their scales, their bodies are composed of fused bony plates, forming a robust box-shaped structure. The fins and tail extend from their bone-armor, and instead of gill covers, they have small slits/pores in their gill area, allowing them to suck water into their mouths for respiration. This enables them to breathe even when they are motionless or hiding on the seafloor🤿, preventing suffocation.
Because of this defense strategy, however, these fishes are unable to generate propulsion by wiggling their bodies, and can only move using their caudal and pectoral fins. As a result, they swim very slowly. It thus seems that they could easily be caught by predators 🦈but just like their close relatives, the pufferfishes, Boxfishes use toxins to protect themselves. When stimulated or stressed from the outside, they secrete a toxic mucus called "pahutoxin" through their skin☣️, which is a hemolytic toxin that causes the red blood cells of surrounding fish to rupture!
If you are interested in this "toxic cutie" or want to learn more about other fascinating marine creatures, come and visit the Hong Kong Biodiversity Museum! 👏You will surely have a lot of fun here. If you enjoy this post, please share it with friends and follow us for more amazing biodiversity stories weekly📖.
Text: Dezer
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