The corallivorous invertebrate Drupella aids in transmission of brown band disease on the Great Barrier Reef

Abstract

Brown band disease (BrB) is an increasingly prevalent coral disease in the Indo-Pacific, but although the macroscopic signs of BrB have been associated with the ciliate Philaster guamensis, many aspects of its ecology remain unknown, particularly how the disease is transmitted among coral colonies. The aim of this study was to assess biotic factors affecting BrB transmission, explicitly testing whether corallivorous species contribute to disease spread. Several fish species were observed feeding on diseased tissue in the field, but did not influence either the progression or transmission rates of BrB on coral colonies in situ. In aquarium-based experiments, the butterflyfish Chaetodon aureofasciatus neither aided nor hindered the transmission of BrB from infected to uninfected corals. In contrast, the coral-feeding gastropod Drupella sp. was a highly effective vector of BrB, infecting more than 40 % of experimental colonies. This study also demonstrated the importance of injury in facilitating BrB infection, supporting the hypothesis that the BrB pathogen invades compromised coral tissue. In conclusion, disturbances and corallivorous activities that injure live corals are likely to contribute to increased occurrence of BrB provided that feeding scars create entry wounds sufficiently extensive to facilitate infection. These findings increase the understanding of the ecology of BrB, enabling better predictions of the prevalence and severity of this disease, and informing strategies for managing the impact of BrB on coral reefs.

Modulation of Hsp60 in response to coral brown band disease

“…The BrB ciliates have been observed to migrate along the length of branching corals from base to tip at a rate much faster than SEB ciliates do. While SEB progression rate in A. muricata has been estimated to be at a maximum of 1 to 2 mm d −1 (Antonius & Lipscomb 2001, Page & Willis 2008, the mean rate of BrB progression on diseased bran ches of A. muricata in the field varies from 5 to 20 mm d −1 (Ulstrup et al 2007, Lobban et al 2011, Nicolet et al 2013, Katz et al 2014, Randall et al 2015. We speculate that this rapid migration of the BrB ciliate would not give the coral defense mechanism the time necessary to react in an attempt to block and confine the infection.…”

“…Since different species of ciliates ingest Symbiodinium cells (Bourne et al 2008, Sweet & Bythell 2012, the term BrB disease is generally used to describe coral infections characterized by a brown band associated with any ciliate containing Symbiodinium and actively consuming coral tissue (Nicolet et al 2013, Sweet et al 2013.…”

“…To date, although this disease is well documented and significant efforts have been made in the identification of the associated microbial communities, less attention has been given to the effects of ciliate presence on coral health and physiology, especially considering the high progression rate of the disease (Nicolet et al 2013, Katz et al 2014. In this context, the use of molecular biomarkers (e.g.…”

“…This was performed by measuring Hsp60 levels in coral polyps situated at 3 different distances away from the disease lesion in colonies of the staghorn coral A. muricata, which is one of the most analyzed widespread species affected by the BrB syndrome worldwide (Ulstrup et al 2007, Bourne et al 2008, Lobban et al 2011, Sweet & Bythell 2012, Nicolet et al 2013.…”

Investigating the Driving Mechanisms Behind Differences in Bleaching and Disease Susceptibility Between Two Scleractinian Corals, Pseudodiploria Strigosa and Diploria Labyrinthiformis

“…These results are particularly important, as very few coral disease vectors have been confirmed (Sussman et al 2003;Nicolet et al 2013;ChongSen et al 2010). These findings also emphasize the importance of examining all members and associates of the coral holobiont, both macroscopic and microscopic, in the effort to understand coral disease etiology and resistance.…”