Interactions between juvenile marine fish and gnathiid isopods: predation versus micropredation

Penfold, R., Grutter, A.S., Kuris, A.M., McCormick, M.I. and Jones, C.M. (2008) Interactions between juvenile marine fish and gnathiid isopods: predation versus micropredation. Marine Ecology-Progress Series, 357 2: 111-119. doi:10.3354/meps07312


Author Penfold, R.
Grutter, A.S.
Kuris, A.M.
McCormick, M.I.
Jones, C.M.
Title Interactions between juvenile marine fish and gnathiid isopods: predation versus micropredation
Journal name Marine Ecology-Progress Series   Check publisher's open access policy
ISSN 0171-8630
1616-1599
Publication date 2008-04-01
Sub-type Article (original research)
DOI 10.3354/meps07312
Open Access Status DOI
Volume 357
Issue 2
Start page 111
End page 119
Total pages 9
Place of publication Oldendorf, Germany
Publisher Inter-Research
Language eng
Abstract Theory suggests that micropredators can be virulent and that they will impact smaller hosts more than larger ones. We examined the interactions between micropredatory gnathiid isopods and juvenile damselfish Acanthochromis polyacanthus, the only fish on the Great Barrier Reef without a pelagic larval stage. Compared to most other fishes, A. polyacanthus can potentially interact with reef-based micropredators much earlier in life. To determine whether gnathiid isopods feed on juvenile A. polyacanthus, 150 juvenile fish sub-sampled from 20 fish broods were surveyed for ectoparasites and micropredators. Gnathiids were associated with 5 A. polyacanthus broods with mean standard lengths (SL) between 4.2 and 21.1 mm. Gnathiids were also found attached to 5 individual A. polyacanthus juveniles <10 mm SL. To determine if infection is detrimental, and/or if juveniles eat gnathiids, we exposed juveniles from a range of sizes (7.2 to 23.5 mm SL) to an individual third stage gnathiid Gnathia falcipenis for 6 h. Gnathiids fed on 29% of fish and gnathiid feeding success was significantly reduced by time in captivity. In 99% of these infections, gnathiids were not eaten afterwards, indicating that micropredation and predation were mutually exclusive. In 40% of trials the fish ate the gnathiid before the gnathiid could feed on the fish, and the probability of gnathiids being eaten was significantly greater for larger fish. Gnathiids only caused mortality in fish <10 mm SL. These data indicate that larger juvenile A. polyacanthus were more likely to eat gnathiids, which preempted micropredation, and less likely to die after gnathiid infection than were smaller juveniles.
Formatted abstract
Theory suggests that micropredators can be virulent and that they will impact smaller hosts more than larger ones. We examined the interactions between micropredatory gnathiid isopods and juvenile damselfish Acanthochromis polyacanthus, the only fish on the Great Barrier Reef without a pelagic larval stage. Compared to most other fishes, A. polyacanthus can potentially interact with reef-based micropredators much earlier in life. To determine whether gnathiid isopods feed on juvenile A. polyacanthus, 150 juvenile fish sub-sampled from 20 fish broods were surveyed for ectoparasites and micropredators. Gnathiids were associated with 5 A. polyacanthus broods with mean standard lengths (SL) between 4.2 and 21.1 mm. Gnathiids were also found attached to 5 individual A. polyacanthus juveniles <10 mm SL. To determine if infection is detrimental, and/or if juveniles eat gnathiids, we exposed juveniles from a range of sizes (7.2 to 23.5 mm SL) to an individual third stage gnathiid Gnathia falcipenis for 6 h. Gnathiids fed on 29% of fish and gnathiid feeding success was significantly reduced by time in captivity. In 99% of these infections, gnathiids were not eaten afterwards, indicating that micropredation and predation were mutually exclusive. In 40% of trials the fish ate the gnathiid before the gnathiid could feed on the fish, and the probability of gnathiids being eaten was significantly greater for larger fish. Gnathiids only caused mortality in fish <10 mm SL. These data indicate that larger juvenile A. polyacanthus were more likely to eat gnathiids, which preempted micropredation, and less likely to die after gnathiid infection than were smaller juveniles.
Keyword Micropredator
Host–parasite interactions
Coral reef fish
Acanthochromis polyacanthus
Gnathia falcipenis
Gnathiid isopod
Mortality
Q-Index Code C1
Q-Index Status Confirmed Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Biological Sciences Publications
Ecology Centre Publications
 
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Created: Thu, 27 Nov 2008, 02:02:00 EST by Gail Walter on behalf of School of Biological Sciences