@article {635, title = {Food and feeding habit of Mormyrus rume (Valenciennes, 1846) in Lake Geriyo, Adamawa, Nigeria}, volume = {11}, year = {2023}, month = {Nov-01-2023}, pages = {102-109}, abstract = {

Mormyrus, a prominent fish within the Mormyridae family in Lake Geriyo and are commercially found in fresh, smoked, fried and roasted forms across the diverse markets of Adamawa, Nigeria. The feeding habit of elephant snout fish from Lake Geriyo was studied during the period of dry season between October, 2022 to March, 2023. A total of 134 samples of fish species were sampled monthly from commercial fishers\’ catches at exactly 6:00am at the landing site. The major fishing methods employed by fisher folks for collecting the specimens were cast netting and set netting. The stomach contents were analysed using numerical and frequency of occurrence approaches. The results from this study indicated out of the 134 specimens collected during the study period, 69 were males, and 65 were females. Stomachs of 65 and 64 individuals were found to have recognizable food items. The higher percentage of identified food items by number were benthic insects and detritus which accounted for 69.713\% and 64.155\% respectively, while the higher percentage frequency of occurrence were detritus and chlorophytes accounted for 100\% and 98.462\% respectively. This revealed that M. rume is a bottom feeder, since benthic insects and detritus were the dominant food components. Diatoms, crustaceans, rotifers and protozoans had relatively lower contributions. The numerical analysis revealed insectivorous behaviour, the frequency of occurrence indicated detritivorous behaviour, and the relative contribution index demonstrated a preference for insects over detritus. Variation in stomach fullness revealed that 45.522\% of the total stomachs examined were at a half-full capacity and females consistently showcase higher foraging intensity than males. The most influential factor affecting the foraging activity of M. rume was the cold phase of the dry season.

}, issn = {2394-0506, 2347-5129}, doi = {10.22271/fish.2023.v11.i6b.2882}, url = {http://dx.doi.org/10.22271/fish.2023.v11.i6b.2882}, author = {B, Jibrin and N, Shu{\textquoteright}aibu} } @article {634, title = {Diet in phenotypically divergent sympatric species of African weakly electric fish (genus: Campylomormyrus){\textemdash}A hybrid capture/HTS metabarcoding approach}, year = {2023}, month = {Dec-21-2023}, abstract = {

Ecological speciation within the mormyrid genus Campylomormyrus resulted in sympatric species exhibiting divergence in their feeding apparatus and electric organ discharge (EOD). This study documents the overall diet of the genus Campylomormyrus and examines the hypothesis that the Campylomormyrus radiation is caused by adaptation to different food sources. We performed diet assessment of five sympatric Campylomormyrus species (C. alces, C. compressirostris, C. curvirostris, C. tshokwe, C. numenius) and their sister taxon Gnathonemus petersii with markedly different snout morphologies and EODs using hybrid capture/HTS DNA metabarcoding of their stomach contents. Our approach allowed for high taxonomic resolution of prey items, including benthic invertebrates, allochthonous invertebrates and vegetation. Comparisons of the diet compositions using quantitative measures and diet overlap indices revealed that all species are able to exploit multiple food niches in their habitats, that is fauna at the bottom, the water surface and the water column. A major part of the diet is larvae of aquatic insects, such as dipterans, coleopterans and trichopterans, known to occur in holes and interstitial spaces of the substrate. The results indicate that different snout morphologies and the associated divergence in the EOD could translate into different prey spectra. This suggests that the diversification in EOD and/or morphology of the feeding apparatus could be under functional adaptation.

}, issn = {0962-1083, 1365-294X}, doi = {10.1111/mec.17248}, url = {http://dx.doi.org/10.1111/mec.17248}, author = {Amen, Rahma and Havenstein, Katja and Kirschbaum, Frank and Tiedemann, Ralph} } @article {632, title = {Ontogeny reveals the origin of Gemminger bones in Mormyridae}, year = {2023}, month = {Jul-25-2023}, abstract = {

Mormyridae are well known and intensively studied for their weak electric organ discharges, which facilitate communication and orientation. The Gemminger bones of Mormyridae are located next to the electrical organ in the caudal peduncle; however, they have not attracted much interest until recently. Therefore, we investigated the diversity of Gemminger bones in mormyrids and studied their ontogenetic development in Mormyrus rume proboscirostris. Gemminger bones are paired, thin, elongated ossifications lying on the dorsal and ventral sides of the caudal peduncle, and usually reach anterior well below the dorsal and anal fin bases. Ontogeny revealed that they are not intermuscular ossifications, as suspected based on the anatomical position of this structure and the systematic position of the mormyrids. Instead, they are membrane ossifications that originate from the fin stays of the dorsal and anal fins.

}, issn = {0021-8782, 1469-7580}, doi = {10.1111/joa.13935}, url = {http://dx.doi.org/10.1111/joa.13935}, author = {Koch, Ann-Katrin and Kirschbaum, Frank and Moritz, Timo} } @article {630, title = {A new genome assembly of an African weakly electric fish (Campylomormyrus compressirostris, Mormyridae) indicates rapid gene family evolution in Osteoglossomorpha}, volume = {24}, year = {2023}, month = {Mar-20-2023}, abstract = {

Abstract Background Teleost fishes comprise more than half of the vertebrate species. Within teleosts, most phylogenies consider the split between Osteoglossomorpha and Euteleosteomorpha/Otomorpha as basal, preceded only by the derivation of the most primitive group of teleosts, the Elopomorpha. While Osteoglossomorpha are generally species poor, the taxon contains the African weakly electric fish (Mormyroidei), which have radiated into numerous species. Within the mormyrids, the genus Campylomormyrus is mostly endemic to the Congo Basin. Campylomormyrus serves as a model to understand mechanisms of adaptive radiation and ecological speciation, especially with regard to its highly diverse species-specific electric organ discharges (EOD). Currently, there are few well-annotated genomes available for electric fish in general and mormyrids in particular. Our study aims at producing a high-quality genome assembly and to use this to examine genome evolution in relation to other teleosts. This will facilitate further understanding of the evolution of the osteoglossomorpha fish in general and of electric fish in particular. Results A high-quality weakly electric fish (C. compressirostris) genome was produced from a single individual with a genome size of 862\ Mb, consisting of 1,497 contigs with an N50 of 1,399\ kb and a GC-content of 43.69\%. Gene predictions identified 34,492 protein-coding genes, which is a higher number than in the two other available Osteoglossomorpha genomes of Paramormyrops kingsleyae and Scleropages formosus. A Computational Analysis of gene Family Evolution (CAFE5) comparing 33 teleost fish genomes suggests an overall faster gene family turnover rate in Osteoglossomorpha than in Otomorpha and Euteleosteomorpha. Moreover, the ratios of expanded/contracted gene family numbers in Osteoglossomorpha are significantly higher than in the other two taxa, except for species that had undergone an additional genome duplication (Cyprinus carpio and Oncorhynchus mykiss). As potassium channel proteins are hypothesized to play a key role in EOD diversity among species, we put a special focus on them, and manually curated 16 Kv1 genes. We identified a tandem duplication in the KCNA7a gene in the genome of C. compressirostris. Conclusions We present the fourth genome of an electric fish and the third well-annotated genome for Osteoglossomorpha, enabling us to compare gene family evolution among major teleost lineages. Osteoglossomorpha appear to exhibit rapid gene family evolution, with more gene family expansions than contractions. The curated Kv1 gene family showed seven gene clusters, which is more than in other analyzed fish genomes outside Osteoglossomorpha. The KCNA7a, encoding for a potassium channel central for EOD production and modulation, is tandemly duplicated which may related to the diverse EOD observed among Campylomormyrus species.

}, issn = {1471-2164}, doi = {10.1186/s12864-023-09196-6}, url = {http://dx.doi.org/10.1186/s12864-023-09196-6}, author = {Cheng, Feng and Dennis, Alice B. and Osuoha, Josephine Ijeoma and Canitz, Julia and Kirschbaum, Frank and Tiedemann, Ralph} } @article {629, title = {Histology of Convergent Probing Appendages in Mormyridae}, journal = {Integrative Organismal Biology}, volume = {5}, year = {2023}, month = {Jan-01-2023}, abstract = {

Mormyridae is an early diverging family of Teleostean fishes that produce an electric field for navigation and communication using an electric organ. This clade has a diverse array of soft-tissue rostral appendages, such as the chin-swelling, the Schnauzenorgan, and the tubesnout combined with a Schnauzenorgan, that have evolved multiple times. Here we assess if macroscopically convergent, soft-tissue rostral appendages are also histologically convergent. Further, we investigate how the histology of these appendages can inform their function. We sampled independent gains of the chin-swelling and Schnauzenorgan to understand similarities and differences in their anatomies. We show that macroscopically convergent rostral appendages are also convergent at a histological level, and different types of rostral appendages share a similar anatomy; that said, minor differences likely relate to their specific functions. Based on a comparison of the skeletal muscle distribution and the differing attachment shapes of each appendage to the dentary, we conclude that the Schnauzenorgan is capable of a wider range of movements than the chin swelling. Furthermore, the anatomy suggests that these soft-tissue rostral appendages likely function as electrosensory foveas (i.e., an appendage that focuses a sensory system). Lastly, these histological data support the hypothesis that the chin swelling may be a precursor to the Schnauzenorgan.

}, issn = {2517-4843}, doi = {10.1093/iob/obad001}, url = {http://dx.doi.org/10.1093/iob/obad001}, author = {Peterson, R D and Evans, A J and Hernandez, L P} }