Habitat Selection Among Fishes and Shrimp in the Pelagic Sargassum Community: The Role of Habitat Architecture

Abstract

The pelagic Sargassum community represents an excellent model system to advance our understanding of how a complex habitat can influence biotic interactions. This study examined the habitat architecture of pelagic Sargassum fluitans to determine its effects on habitat selection for one shrimp species (Leander tenuicornis) and two fish species (Stephanolepis hispidus and Histrio histrio). Specifically, we manipulated interthallus spacing and depth of Sargassum habitats independently (i.e., in separate experimental trials) to test whether spatial components of habitat architecture influence habitat selection by these animal inhabitants. Additionally, two differing habitats (Sargassum vs intermingled seagrass species, Thalassia testudinum and Syringodium filiforme) were tested to determine whether structural components of habitat architecture influenced habitat selection. Results showed no significant effect of habitat selections for interthallus spacing experiments for L. tenuicornis and S. hispidus. However, H. histrio selected habitats with medium interthallus spacing characteristics in two experiments. All three animals selected habitats with a greater depth aspect. Finally, L. tenuicornis and H. histrio selected habitats with greater structural complexity (i.e., Sargassum habitat). These results demonstrate that habitat architecture (i.e., spatial and structural components) of Sargassum influences habitat selection by the aforementioned fauna and further illustrate that this pelagic macroalga is an essential habitat for multiple species.

The Use of Chemical Cues by Sargassum Shrimps Latreutes fucorum and Leander tenuicornis in Establishing and Maintaining a Symbiosis with the Host Sargassum Algae

“…When looking at both this current study and the previously mentioned studies on this community, it is clear that chemoreception is a major mechanism being used by several organisms in the Sargassum holobiont. Another study looked at habitat selection by both L. tenuicornis and the common fish species, Histrio histrio, and found that the organisms have preferred habitats based on structural complexity [8]. It is likely that all of these organisms are interconnected and play an important role in maintaining this symbiotic community, and the use of chemoreception is one vital component to the success of this symbiosis.…”

“…For example, L. tenuicornis shows a preference for deeper floating Sargassum patches (10-12 cm below the surface) than shallow patches. Additionally, L. tenuicornis positions itself in a parallel alignment with the fronds, thus allowing the shrimp to blend with the fronds and exhibit algal morphology mimicry [8]. Such behaviors by L. tenuicornis and its innate camouflage maximize protection from predators such as jacks, sargassum fish (Histrio histrio) and the gray triggerfish (Balistes capriscus), the last of which is one of the most abundant fish in Sargassum and feeds almost exclusively on Sargassum shrimp [1,7].…”