Coral crabs, small creatures that inhabit the coral structures of tropical seas, have been the protagonists of a recent scientific breakthrough. A group of experts has revealed that these crustaceans use a technique of fluorescence-based camouflage, visually integrating into the striking reef environment. This discovery opens new lines of research on how marine animals interact and adapt to their complex habitats..
The research, led by scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, has captured the attention of the scientific community by revealing for the first time the phenomenon of fluorescence in crabs related to coralsThis is a significant advance in understanding both marine biological diversity and the mechanisms that promote the survival of these species in threatened ecosystems.
An unexpected discovery: fluorescence as a camouflage strategy
The work, published in the journal Proceedings of the Royal Society B, documents how the gall crabs of the Cryptochiridae family manifest fluorescent optical patterns in different parts of the body. It has been observed that absorbing high-energy light y re-issuing it At longer wavelengths—especially orange and red hues—these animals are able to conceal their presence among the bright colors of the coralsThis phenomenon, common in reef fish, was practically unknown among crustaceans until now.
The scientific team, under the direction of Susanne Bähr, made her discovery during a night dive. The researcher recounted how the crabs' peculiar fluorescence caught her attention, prompting her to investigate possible functions beyond simple body decoration. The central hypothesis is that Fluorescence could facilitate camouflage, helping the crabs blend in with the coral environment and probably avoid predators.
Although the biological function of this fluorescence is still being investigated, the location of the fluorescent areas —such as tweezers and abdomen— suggests that There could also be other uses, including sending signals between individuals. or communication during mating.
Symbiotic relationship and evolutionary adaptation
Gall crabs maintain a very close bond with corals that offer them shelter and food. Unlike other marine invertebrates that only seek protection in the coral, these crustaceans establish a long-term symbiosisAs Bähr herself explained, the life cycle begins when a larva settles on the surface of the coral; the coral then grows to envelop the larva, forming a burrow where the female will remain for her entire life.
The females feed on the mucus secreted by the coral and generate new larvae, while males look for a mateThe coexistence of these creatures affects both the survival of the crabs and the health of the reefs.
Fluorescence not only has implications for camouflage, but is also related to the evolutionary lineagesThe genomic study carried out allowed the reconstruction of the phylogenetic tree of the group, noting that fluorescence has been maintained or lost depending on gender and environmental pressures.
Implications for marine biodiversity
During the study, data were collected: 286 specimens of coral crabs, from the Red Sea, the Indian Ocean and enclaves such as the Maldives. They were used imaging techniques and fluorescence microscopy in 250 specimens to identify and quantify the fluorescent patterns, as well as spectrometry to determine the emission peak around 603 nanometers in the most common genera.
Morphological and genetic analysis revealed four main groups of “fluotypes”, ranging from species with little fluorescence to others with very noticeable patterns in specific areas of the body, such as the genus Opecarcinus. It was also detected that of the 250 specimens analyzed, 221 showed orange fluorescence under blue light, highlighting the significant presence of this trait in the group.
They were identified 18 distinct genetic clades, supporting the hypothesis that the origin of fluorescence is common in some lineages but has been modified over time. Furthermore, the crabs' visibility is affected by the type of shelter and the arrangement of the fluorescent patterns, helping them go unnoticed.
The researchers emphasize that it is not yet known whether the crabs themselves can perceive their fluorescence or whether it plays a role in intraspecific communication. Therefore, they recommend future research into the visual sensitivity of these crustaceans and the chemical compounds responsible for their fluorescent colors.
The lead author highlighted the importance of assessing the ecological role of these animals to conserve the coral reefsBoth aspects—fluorescence and its relationship to habitat—are essential to understanding how to protect these vulnerable ecosystems from the threats of climate change and environmental degradation.
