Data from: Preying on cyprinid snout warts (pearl organs) as a novel and peculiar habit in the Lake Malawi cichlid Docimodus evelynae
Data files
May 12, 2026 version files 13.98 KB
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README.md
2.73 KB
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Results_of_XRF_analysis.csv
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Stomach_contents.csv
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Warts_number.csv
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Abstract
Cichlid fishes in the African Great Lakes have undergone explosive speciation, acquiring markedly varying ecologies and diets. There are multiple lineages of scale-eating cichlids, and their natural history and evolutionary ecology is only partially understood. We examined the feeding habit of Docimodus evelynae, a known scale eater, in Lake Malawi. The stomach contents of young individuals mainly consisted of unknown 1 mm hard, white warts (>30%). To clarify the origin of these warts, we conducted an X-ray fluorometer analysis and found they were rich in sulphur but low in silicon and calcium, suggesting they were epidermal tissues. Histological and morphological analyses revealed they were multicellular and cup-shaped. These characteristics matched only those of the pearl organs of the coexisting cyprinid Labeo cylindricus. DNA was extracted from the warts found in the stomach of five D. evelynae individuals, followed by PCR using primers targeting the partial COI gene of L. cylindricus. The resulting sequences exhibited 98% similarity to those of L. cylindricus. Pearl organs, never reported as a primary food for fish, could offer a substantial nutritional source based on calorific calculations. Understanding how this peculiar diet is foraged is essential for full comprehension of the food-web structure in this lake.
https://doi.org/10.5061/dryad.2fqz612vv
In this study, we found that the stomach contents of Docimodus evelynae in Lake Malawi were mainly composed of white bony warts, suggesting they had a strange habit of feeding. By integrating data from several analytical approaches (μCT scanning, histological studies, XRF analysis, DNA analysis, and caloric calculations), we found those white warts were the pearl organ of a dominant cyprinid Labeo cylindricus, which coexists in the lake. As far as we know, the pearl organ eating is a novel feeding habit and has not yet been described in any other fish species. This finding deepens our understanding of the unique adaptive radiation and consequent complicated interspecific interactions and ecological dynamics of cichlid fishes in Lake Malawi. All datasets were shown in “Pearl_organs_Dataset.xlsx”.
The data and file structure
- Sampling site: Thumbi West Island of Lake Malawi.
- Methods for processing the data: Figure 1C was obtained by the stomach content analysis of Docimodus evelynae. Table 1 was obtained by XRF analysis. Figure S2 was obtained by observing the pearl organ of Labeo cylindricus.
File 1: Stomach contents.csv
Description:
The diet of each individual was recorded. The food items listed include Warts, Catfish, Scale, Fin, Fish egg, Argulus, and UNID, each assigned a specific point value. SL (mm) indicates the standard body length. TP stands for total point.
File 2: Results of XRF analysis.csv
Description:
Results of XRF analysis, showing percentage (mean ± SD) of each element of potential hard, white wart candidates. "Analyzed parts" refers to the items analyzed, and "Origin" indicates the species. The subsequent entries show the percentage of each element in the candidate items.
File 3: Warts number.csv
Description:
This data illustrates the relationship between standard body length and the number of warts. It also includes information on when and where the specimens were collected. "Specimen ID" refers to the sample number, "Month of collection" refers to the month of collection, "Year of collection" refers to the year of collection, "Site of collection" refers to the collection site, "Collector" refers to the collector, "Species" refers to the fish species, "Sex" refers to the sex, "Body WW (g)" refers to body weight, "Body SL (mm)" refers to body length, "Number of pearl organs" refers to the number of pearl organs, and "Size class of pearl organ" indicates the size of the pearl organ.