Abstract
Fish diets have been traditionally studied through the direct visual identification of food items found in their stomachs. Stomach contents of Vandeliinae and Stegophilinae (family Trichomycteridae) parasite catfishes, however, cannot be identified by usual optical methods due to their mucophagic, lepidophagic or hematophagic diets, in such a way that the trophic interactions and the dynamics of food webs in aquatic systems involving these catfishes are mostly unknown. The knowledge about trophic interactions, including difficult relation between parasites and hosts, are crucial to understand the whole working of food webs. In this way, molecular markers can be useful to determine the truly hosts of these catfishes, proving a preference in their feeding behaviour for specific organisms and not a generalist way of life. Sequences of cytochrome oxidase subunit 1 (COI) were successfully extracted and amplified from mucus or scales found in the stomach contents of two species of stegophilines, Homodiaetus anisitsi and Pseudostegophilus maculatus, to identify the host species. The two species were found to be obligatory mucus-feeders and occasionally lepidophagic. Selection of host species is associated to host behaviour, being constituted mainly by substrate-sifting benthivores. Characiformes are preferred hosts, but host choice depends on what characiform species are available in their environments, usually corresponding to the most abundant species. This is the first time that host species of parasitic fishes bearing mucophagous habits are identified, and demonstrates the effectiveness of the extraction and amplification of mitochondrial DNA from the ingested mucus in gut contents. The molecular markers effectively allowed determine parasite preferences and helps in better understanding the food web and trophic interaction on which fish species are involved. Despite, the methodology applied here can be used for an infinitive of organisms improving ecological trophic studies.
Highlights
The role of parasites in food webs has been largely disregarded (Sukhdeo, 2012)
The stomachs of 42 specimens of H. anisitsi and 10 specimens of P. maculatus contained ingested items identified as mucus and occasionally scales, sometimes associated with sand (Tables 1, 2 and Supplementary Table 1)
DNA was successfully extracted from gut contents of all these specimens, but amplification gave positive results only for 10 specimens of H. anisitsi and 7 specimens of P. maculatus
Summary
The role of parasites in food webs has been largely disregarded (Sukhdeo, 2012). As an example, Winemiller and Polis (1996) was the most important contribution of food web studies but not approached the parasite-host interaction as part of the trophic webs. Since Elton insights (Elton et al, 1931) it is known that parasites are very important links in the food webs and are capable of externing major effects on ecological interactions. Many questions remain as how parasites might fit in food webs, if it should be included or excluded in the food webs, what is the role of parasites in host population regulation, and what are the evolutionary and ecological implications of parasite mediation in trophic interactions (Sukhdeo and Hernandez, 2005). Small alteration in the position of parasites and host can change the food chain length, connectance, and the establishment of food patterns (Huxham et al, 1995; Leaper and Huxham, 2002)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
