Smashing Mantis Shrimp

Gonodactylus chiragra is a species of mantis shrimp that is widely distributed throughout the West Indo-Pacific. It is a medium to large-sized species, typically reaching a maximum length of 105 millimetres. Males display a range of colors from brown to dark green, while females can range from grey/green to white.

All mantis shrimp species are categorized as either spearers or smashers. Gonodactylus chiragra falls under the category of smashers, which means their second pair of thoracic appendages is significantly enlarged, forming a club-like structure used to smash their prey. When Gonodactylus chiragra spots its target, it delivers powerful and rapid strikes, making it one of the quickest punchers in the natural world. Snails, hermit crabs, and clams are common prey for this species, but they have been known to target larger animals such as molluscs and other crustaceans as well. Gonodactylus chiragra employs a unique fighting strategy where it circles around its target and aims for the head. This behavior is believed to have developed due to intense competition for suitable burrows among stomatopods. In captivity, Gonodactylus chiragra often strikes glass walls and air tubes in aquariums, highlighting its aggressive nature.

Underwater vision is significantly different from vision in ambient light due to strong spectral variations that affect color perception. Gonodactylus chiragra possesses eyes that are sensitive to linear polarization, making them highly unique within the animal kingdom. This sensitivity to polarization provides several advantages, including increased contrast enhancement, the ability to detect polarization reflecting prey, and improved navigation in the light-scattered ocean environment. The eyes of Gonodactylus chiragra are large stalked apposition compound eyes and possess two distinct features that contribute to their complexity. Firstly, they have the ability to rotate independently, with one eye being sufficient for capturing prey. Secondly, there is a midband present, which is a large strip of specialized clusters of photoreceptor cells that divides each eye into two segments. The midband contains polarization receptors in specific rows, allowing Gonodactylus chiragra to detect linearly polarized light. The midband also aids in binocular distant vision. Despite the complexity of their eyes, Gonodactylus chiragra lacks polarized body markings, unlike many other mantis shrimp species. It is believed that the evolution of lethal weapons, such as their powerful claws, was preferred over body signals due to the species' restricted habitat.

Gonodactylus chiragra is widely distributed in the western Indo-Pacific and is typically found in shallow water in the upper intertidal zone, particularly around boulders and coral heads where prey is abundant. While Gonodactylus chiragra is capable of burrowing, it typically inhabits existing rocky cavities created by natural processes or other animals, such as molluscs. However, Gonodactylus chiragra is equipped to erode the material of the burrow to fit its body shape perfectly. Burrows serve multiple purposes for this species, including protection, lookout points for locating prey, consuming prey, mating, and safeguarding eggs. Gonodactylus chiragra is diurnal and often seals off the entrance to its burrow at night using sand and rocks.