Tiny shrimp can sniff their way to cave homes using unique chemical cues

Mysid shrimp, often called possum shrimp due to the pouches females use to carry their larvae, are known for their homing abilities.

Research has suggested that these cave-dwelling shrimp may rely on chemical cues to find their way back to underwater caves, similar to how coral larvae and reef-dwelling fish can detect differences between healthy and damaged reef environments.

“Here we show for the first time that mysids can tell the water-borne odor bouquet – its so-called chemical seascape – characteristic of their home cave apart from that of nearby caves,” said Dr Thierry Pérez, the lead author of a new study.

“This strongly suggests that these distinctive seascapes help them find their home cave again when they return from their nightly migrations.”

Cave-dwelling shrimp return home

Pérez and colleagues focused on the mysid species Hemimysis margalefi , a cave-dwelling shrimp found in sea caves of the northwestern Mediterranean. These shrimp are believed to exhibit strong fidelity to their natal caves, staying in the same one throughout their 1-2 year lifespan.

To investigate how these shrimp might navigate back to their caves, the researchers collected seawater samples from three caves in Calanques National Park, southern France.

They captured hundreds of adult H. margalefi from two specific caves—Fauconnière and Jarre—as well as individuals of another mysid species from the genus Leptomysis , which resides in shallow waters but not in caves, for comparison.

In each experimental trial, the shrimp were then given the choice of which cave water to follow, with the time spent in each arm indicating their preference.

The team tested 286 shrimp—230 H. margalefi and 56 Leptomysis . They also ran the experiments at different times of day, but found no effect of time on the shrimps’ preferences, indicating that the time of day didn’t influence their navigation abilities.

How climate change would affect these shrimp

The results of the study showed that Hemimysis margalefi exhibited a strong preference for water from their own natal caves. In contrast, the non-cave-dwelling Leptomysis showed no preference for any water type.

To understand the chemical basis of this behavior, the researchers analyzed the chemical composition of the water samples. They found that the chemical profiles of Jarre and Fauconnière caves were distinct, with unique metabolites like peptides, fatty acids, steroids, alkaloids, and some anthropogenic pollutants.

The researchers proposed that the metabolites in the water could be largely produced by sessile organisms like sponges, which are abundant in these caves and known to generate specialized chemicals.

This suggests that any environmental changes affecting the sponge and coral populations in these ecosystems could alter the chemical cues that organisms like H. margalefi use to navigate, potentially impacting the entire ecosystem.

Pérez emphasized in the press release that this is concerning given the increasing mass mortality of sponges and corals due to global environmental changes . The team is now working to further investigate the correlation between the chemical signatures of different caves and the biodiversity of sessile organisms within them, with a focus on the role of sponge and coral metabolites.

The study has been published in Frontiers in Marine Science .