The early catfish catches the worm: predation of Corydoras aeneus (Siluriformes, Callichthyidae) on freshwater nematodes

[Horlack]

The early catfish catches the worm: predation of Corydoras aeneus (Siluriformes, Callichthyidae) on freshwater nematodes

Published by/Issue : EDP Sciences, 2018 and, Ann. Limnol. - Int. J. Lim. 2018, 54, 29
Received : 2 December 2017;
Accepted : 18 June 2018
Authors : Nabil Majdi Sebastian Weber and Walter Traunspurger
DOI : https://doi.org/10.1051/limn/2018019
PDF : https://www.limnology-journal.org/artic ... 170073.pdf

In this study, we measured the daily consumption of four different nematode species by a small freshwater catfish species, Corydoras aeneus (Gill, 1858). Consumption of nematodes by fishes was significant with a single C. aeneus individual being able to consume in 24 h between 40 581 and 75 849 adult nematodes depending on the nematode species offered. This represented the ingestion of up to 238 mg wet weight when considering the largest nematode species : Panagrellus redivivus. Our results strengthen the growing evidence of a significant trophic channel existing between meiobenthic invertebrates like nematodes and small bottom-feeding fishes like C. aeneus. We also discuss the relevance of using P.redivivus as live food for rearing C. aeneus which is a popular ornamental fish.

Keywords : Predator-prey interaction / aquaculture / benthic ecology /Caenorhabditis elegans / Panagrellus redivivu

[Bas Pels]

238 mg of food for a say 5 cm Corydoras, of approximately 5 g will imply a food percentage of around 4,8 %

That´s an awfull lot: a 70 kilo human would have to eat 3,33 kilos of food in comparison.

All the reason to read the article. This sais `juveniles` and `starved 24 hours before the experiment`

That is, the amount of food, as a percentage of bodyweigt is even higher, and the fishes are lightly starved.

I have some problems with the results

[Narwhal72]

I would have to think the wet weight of the food plays a factor. What percentage body weight of a nematode is water? If it's something like 80% then we are talking only 47.6 mg dry weight.

But I have no idea what a nematodes moisture content is.

Andy

[Bas Pels]

I would assume it is over 95 %. But still, meat is over 80 % water, and vegetables 90 to 95 % - if my memory serves me right

[Horlack]

Dr Nabil Majdi

https://scholar.google.fr/citations?use ... AAAJ&hl=fr
http://www.uni-bielefeld.de/biologie/Zo ... majdi.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4388577/

He is specialist of micro-fauna, invertebrate and nematode

He do his PhD Thesis in Functional Ecology, at Toulouse University (France)
http://www.theses.fr/2011TOU30260

For me, even though his sciences news may seem strange on some points, I think, that my impression is wrong. He seems competent according to his diplomas and specialties.

[Lycosid]

This paper (Do Meio- and Macrobenthic Nematodes Differ in Community Composition and Body Weight Trends with Depth?) estimates dry weight of nematodes as 25% of wet weight (and links to some not-so-open source papers to justify that).
The original paper states that prey weight as a percent of predator weight ranged between 14 and 54%. 54% wet weight would leave 13.5% the wet weight of the fish as dry mass of prey. This might be possible - especially since the tests lasted 24 hours, which gives the catfish time to digest the nematodes, excrete the excess fluid, and eat some more.
However, the purpose of the paper seems to be to demonstrate the effect size of the feeding of a large predator on small prey (5 orders of magnitude differences separate predator and prey). The one and only figure in the paper compares before and after in nematode numbers. The ecological point of the paper stands as long as those ratios are reasonably correct. If the raw numbers were off that would be less important, and so the method of estimating nematode numbers needs to be an apples-to-apples comparison more than it needs to be an excellent count of nematodes.

[MChambers]

Thanks for sharing this!

That’s a lot of microworms! Maybe I should be feeding microworms daily to all of my Corydoras.