A lack of clear dietary differences between ontogenetic stages of invasive slippersnails provides important insights into resource use and potential inter- and intra-specific competition

Review of “Trophic niche of the invasive gregarious species Crepidula fornicata, in relation to ontogenic changes” Androuin et al. bioRxiv, PCI Ecology This is an interesting ms investigating the trophic ecology of slipper limpets, using a complimentary biomarker approach, combining fatty acids, isotopes, and natural history. The findings are based on observational data. The writing is generally good; it may be more text in some sections than is absolutely necessary, and it may be preferable to move some text from the discussion to the introduction. The methods and interpretation of the data seem appropriate. The figures are very informative. I have a few suggestions for improving the flow and interpretation below. The Abstract clearly states that ” the trophic niche of C. fornicata does not change significantly across its benthic life” which should have been the expected result. This paper is a classic example of ‘collect a lot of data and see if it tells us anything’. It is also common sense that the FA profiles would be different between the males and females and sampling dates. Abstract: what is ‘opportunistic suspension feeding behaviour’? That is their natural feeding mode, they feed upon what is in the surrounding water column! Overall, this manuscript presents a lot of data – everything they could measure – and no much in the way of synthesis or significance. In essence, it is overkill to make a nonstatement about nonexistent trophic niche differences. There isn’t even a clear discussion of why trophic niche differences would or could make a difference to anything tangible. It is also a dangerous practice to ‘infer’ anything, least of all assimilation of organic material (line 363). Line 429 which states that … the slipper limpet is an opportunistic suspension-feeder that exploits both pelagic and benthic particulate OM… is well known and this study did not discover that fact. It should have references. FA profiles would obviously be different between males and females and would vary over time, temperature, food availability, season, and other environmental factors. The manuscript is excessively long and longwinded. There are some interesting data, but as presented it is just a catalog of results, many of them repeated in the discussion. The entire paper reads like a thesis with every possible data point included. It could and should be shortened by half (at least). It is a tedious read and actual results and their significance are difficult to identify. The many instances are ‘references of convenience’, i.e. what was at hand or cited elsewhere, not the key for the Example: Blanchard 1997 the source that Crepidula