Predation scars may influence host susceptibility to pathogens: evaluating the role of corallivores as vectors of coral disease

Abstract

Infectious diseases not regulated by host density, such as vector-borne diseases, have the potential to drive population declines and extinctions. Here we test the vector potential of the snail Drupella sp. and butterflyfish Chaetodon plebeius for two coral diseases, black band (BBD) and brown band (BrB) disease. Drupella transmitted BrB to healthy corals in 40% of cases immediately following feeding on infected corals, and even in 12% of cases 12 and 24 hours following feeding. However, Drupella was unable to transmit BBD in either transmission treatment. In a field experiment testing the vector potential of naturally-occurring fish assemblages, equivalent numbers of caged and uncaged coral fragments became infected with either BrB, BBD or skeletal eroding band, indicating that corallivorous fish were unlikely to have caused transmission. In aquaria, C. plebeius did not transmit either BBD or BrB, even following extended feeding on both infected and healthy nubbins. A literature review confirmed only four known coral disease vectors, all invertebrates, corroborating our conclusion that polyp-feeding fishes are unlikely to be vectors of coral diseases. This potentially because polyp-feeding fishes produce shallow lesions, not allowing pathogens to invade coral tissues. In contrast, corallivorous invertebrates that create deeper feeding scars increase pathogens transmission.

Corallivory in the Anthropocene: Interactive Effects of Anthropogenic Stressors and Corallivory on Coral Reefs

“…For instance, the coral-feeding butterflyfish Chaetodon multicinctus plays an implicit role in the dynamics of trematodiasis infection in some Porites spp., by serving as a final host in the life cycle of the trematode Podocotyloides stenometra (Aeby, 1998(Aeby, , 2002. Similarly, some corallivores can transmit disease pathogens to corals, and four invertebrate corallivores have been empirically linked to coral disease transmission (see Table 1 in Nicolet et al, 2018a). It is likely that this mechanism of disease transmission may be more common than currently appreciated.…”

“…Similarly, butterflyfishes prey on diseased coral tissue (Aeby and Santavy, 2006;Chong-Seng et al, 2011;Nicolet et al, 2013Nicolet et al, , 2018b with coral disease correlating positively with butterflyfish abundance (Raymundo et al, 2009). Corallivorous fishes may transmit disease pathogens orally or through feces (Aeby and Santavy, 2006), however, more research is needed to demonstrate if there is a causal link between corallivorous fishes (e.g., butterflyfishes and parrotfishes) and coral disease transmission (Nicolet et al, 2018a). Fish acting as vectors may be an important driver structuring coral-microbial communities, particularly for excavating corallivores, like parrotfishes, that create larger wounds in corals.…”

“…In the context of anthropogenic forcing, corallivory may act synergistically to destabilize the coral microbiome, leading to compromised host immunity (Zaneveld et al, 2017) and increased mortality (Zaneveld et al, 2016). Moreover, compared to MPAs, overfished reefs have a higher prevalence of coral disease (Raymundo et al, 2009) and larger populations of invertebrate corallivores capable of transmitting opportunistic bacteria (McClanahan, 1994;Sweatman, 2008;Nicolet et al, 2018a). These local processes may further fuel coral disease propagation via corallivory.…”

Treatment of Coral Wounds by Combining an Antiseptic Bilayer Film and an Injectable Antioxidant Biopolymer

“…Indeed, protection from corallivores with various foraging strategies can increase coral growth 38 and coral reproductive potential 39 . Moreover, beyond affecting corals through mechanical damage, corallivores provide entry points for opportunistic bacteria (e.g., coral diseases) and can aid in parasite transmission on the reef 40 . Further understanding of how the use of antiseptic bilayer and the injectable PCL-PCA copolymer might shape the effects of corallivores on coral health will also be important and will need to be elucidated in the next future.…”

Parrotfish predation drives distinct microbial communities in reef-building corals

“…Corallivorous, polyp-feeding butterflyfishes may also spread microbes and parasites via their mouthparts [14][15][16][17][18]. However, the fact that butterflyfishes remove limited coral tissue without exposing the underlying skeleton may make them unlikely candidates to transmit microbes among individual corals [16]. In contrast, many parrotfishes scrape or excavate both live coral tissue and skeleton, while also ingesting detritus and turf algae from rocky surfaces [19].…”