Unravelling the macro-evolutionary ecology of fish–jellyfish associations: life in the ‘gingerbread house’

Abstract

Fish–jellyfish interactions are important factors contributing to fish stock success. Jellyfish can compete with fish for food resources, or feed on fish eggs and larvae, which works to reduce survivorship and recruitment of fish species. However, jellyfish also provide habitat and space for developing larval and juvenile fish which use their hosts as means of protection from predators and feeding opportunities, helping to reduce fish mortality and increase recruitment. Yet, relatively little is known about the evolutionary dynamics and drivers of such associations which would allow for their more effective incorporation into ecosystem models. Here, we found that jellyfish association is a probable adaptive anti-predator strategy for juvenile fish, more likely to evolve in benthic (fish living on the sea floor), benthopelagic (fish living just above the bottom of the seafloor), and reef-associating species than those adapted to other marine habitats. We also found that jellyfish association likely preceded the evolution of a benthic, benthopelagic, and reef-associating lifestyle rather than its evolutionary consequence, as we originally hypothesized. Considering over two-thirds of the associating fish identified here are of economic importance, and the wide-scale occurrence and diversity of species involved, it is clear the formation of fish–jellyfish associations is an important but complex process in relation to the success of fish stocks globally.

A phylogenomic framework for pelagiarian fishes (Acanthomorpha: Percomorpha) highlights mosaic radiation in the open ocean

“…These suggest a broad range of ecological opportunities of the kind thought to be critical in triggering divergence [15]. For example, a hypothesized proliferation of jellyfishes in the early Palaeogene [63] could have provided the substrate for diversification of pelagiarian clades that directly feed upon [9] or are otherwise associated with gelatinous zooplankton [67].…”

Sighting of the rare jellyfish Anomalorhiza shawi Light, 1921 in a marine protected area of Hong Kong

“…Anomalorhiza shawi is known to associate with other marine organisms, with previous records of A. shawi showing crabs and juvenile fishes found within the bell of the medusae (Chuan et al 2020). Small organisms will generally associate with jellyfishes to obtain shelter from predators (Purcell and Arai 2001;Ohtsuka et al 2010;Gonçalves et al 2016;Moraes et al 2017), providing trophic resources and protection for juvenile fish (Masuda et al 2008;Griffin et al 2019), as a food source (Pauly et al 2009; D'Ambra et al 2014), for prey collection (Masuda et al 2008), or as a form of transportation. Small crustaceans have also been observed in facultative commensalism with jellyfish (Martinelli Filho et al 2008).…”

Freshwater hydrozoan blooms alter activity and behaviour of territorial cichlids in Lake Tanganyika

“…The factors that promote the rapid growth, i.e. 'blooms', of gelatinous zooplankton populations in our oceans and freshwater systems have been a focus of considerable research to date [1][2][3][4][5]. More recent research examining the interactions between fish populations and blooms of gelatinous organisms suggests that their relationships can be complex [6].…”

“…Blooms can be harmful to fish populations by injuring or directly killing fish with their stinging cells, including their eggs and larvae, or by competing for the same food resources [7][8][9][10]. However, blooms may also be beneficial by providing an important food source for certain fishes [11][12][13], and even by providing nursery and foraging space for juveniles of other species [4,14,15]. Thus, the impact of gelatinous zooplankton blooms on individual fish and fish populations can be highly nuanced and depend on a wide range of ecological and species-specific factors.…”

“…Furthermore, substantial diet overlaps between certain fishes and jellyfish species have also been uncovered suggesting the potential for food competition [10]. Juvenile fish may also enjoy increased foraging opportunities by associating with gelatinous zooplankton, either by feeding on them directly or on the prey that they capture in their tentacles [4,14]. However, we currently have a poor understanding of how gelatinous zooplankton can impact other behaviours outside of a foraging context, such as social behaviour or parental care.…”