@article {608, title = {Intergenus F1-hybrids of African weakly electric fish (Mormyridae: Gnathonemus petersii ♂ {\texttimes} Campylomormyrus compressirostris ♀) are fertile.}, journal = {J Comp Physiol A Neuroethol Sens Neural Behav Physiol}, year = {2022}, month = {2022 Feb 04}, abstract = {

Hybridisation is an important element of adaptive radiation in fish but data are limited in weakly electric mormyrid fish in this respect. Recently, it has been shown that intragenus hybrids (Campylomormyrus) are fertile and are able to produce F2-fish. In this paper, we demonstrate that even intergenus hybrids (Gnathonemus petersii ♂ \× Campylomormyrus compressirostris ♀) are fertile. Three artificial reproduction (AR) trials, with an average fertilisation rate of ca. 23\%, yielded different numbers of survivals (maximally about 50\%) of the F1-hybrids. The complete ontogenetic development of these hybrids is described concerning their morphology and electric organ discharge (EOD). Two EOD types emerged at the juvenile stage, which did not change up to adulthood. Type I consisted of four phases and Type II was triphasic. The minimum body length at sexual maturity was between 10 and 11\ cm. Malformations, growth and mortality rates are also described.

}, issn = {1432-1351}, doi = {10.1007/s00359-022-01542-5}, author = {Korniienko, Yevheniia and Nzimora, Kingsley C and Vater, Marianne and Ralph Tiedemann and Kirschbaum, Frank} } @article {602, title = {Intragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua ♂ {\texttimes} C. compressirostris ♀) are fertile}, journal = {Journal of Comparative Physiology A}, volume = {206}, year = {2020}, month = {Jan-07-2020}, pages = {571 - 585}, abstract = {

Hybridization is widespread in fish and constitutes an important mechanism in fish speciation. There is, however, little knowledge about hybridization in mormyrids. F1-interspecies hybrids between Campylomormyrus tamandua ♂ \× C. compressirostris ♀ were investigated concerning: (1) fertility; (2) survival of F2-fish and (3) new gene combinations in the F2-generation concerning the structure of the electric organ and features of the electric organ discharge. These F1-hybrids achieved sexual maturity at about 12\–13.5 cm total length. A breeding group comprising six males and 13 females spawned 28 times naturally proving these F1-fish to be fertile. On average 228 eggs were spawned, the average fertilization rate was 47.8\%. Eggs started to hatch 70\–72 h after fertilization, average hatching rate was 95.6\%. Average mortality rate during embryonic development amounted to 2.3\%. Average malformation rate during the free embryonic stage was 27.7\%. Exog- enous feeding started on day 11. In total, we raised 353 normally developed larvae all of which died consecutively, the oldest specimen reaching an age of 5 months. During survival, the activities of the larval and adult electric organs were recorded and the structure of the adult electric organ was investigated histologically.

}, issn = {0340-7594}, doi = {10.1007/s00359-020-01425-7}, url = {http://link.springer.com/10.1007/s00359-020-01425-7}, author = {Korniienko, Yevheniia and Nguyen, Linh and Baumgartner, Stephanie and Vater, Marianne and Ralph Tiedemann and Kirschbaum, Frank} } @article {598, title = {Ontogeny of the electric organ discharge and of the papillae of the electrocytes in the weakly electric fish}, journal = {Journal of Comparative Neurology}, year = {2020}, month = {Dec-08-2020}, abstract = {

The electric organ of the mormyrid weakly electric fish, Campylomormyrus rhynchophorus (Boulenger, 1898), undergoes changes in both the electric organ discharge (EOD) and the light and electron microscopic morphology as the fish mature from the juvenile to the adult form. Of particular interest was the appearance of papillae, surface specializations of the uninnervated anterior face of the electrocyte, which have been hypothesized to increase the duration of the EOD. In a 24.5\ mm long juvenile the adult electric organ (EO) was not yet functional, and the electrocytes lacked papillae. A 40\ mm long juvenile, which produced a short biphasic EOD of 1.3\ ms duration, shows small papillae (average area 136\ \μm2). In contrast, the EOD of a 79\ mm long juvenile was triphasic. The large increase in duration of the EOD to 23.2\ ms was accompanied by a small change in size of the papillae (average area 159\ \μm2). Similarly, a 150\ mm long adult produced a triphasic EOD of comparable duration to the younger stage (24.7\ ms) but featured a prominent increase in size of the papillae (average area 402\ \μm2). Thus, there was no linear correlation between EOD duration and papillary size. The most prominent ultrastructural change was at the level of the myofilaments, which regularly extended into the papillae, only in the oldest specimen \– probably serving a supporting function. Physiological mechanisms, like gene expression levels, as demonstrated in some Campylomormyrus species, might be more important concerning the duration of the EOD.

}, issn = {0021-9967}, doi = {10.1002/cne.25003}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/cne.25003https://onlinelibrary.wiley.com/doi/pdf/10.1002/cne.25003https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2Fcne.25003https://onlinelibrary.wiley.com/doi/pdf/10.1002/cne.25003}, author = {Korniienko, Yevheniia and Ralph Tiedemann and Vater, Marianne and Kirschbaum, Frank} } @article {543, title = {Intragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: physiological and histological investigations of the electric organ ontogeny}, journal = {Journal of Physiology-Paris}, year = {2017}, month = {Jan-01-2017}, abstract = {

African weakly electric mormyrid fish show a high diversity of their electric organ discharge (EOD) both across and within genera. Thanks to a recently developed technique of artificial reproduction in mormyrid fish, we were able to perform hybridizations between different genera and within one genus (Campylomormyrus). The hybrids of intergenus hybridizations exhibited different degrees of reduced survival related to the phylogenetic distance of the parent species: hybrids of the crosses between C. rhynchophorus and its sister genus Gnathonemus survived and developed normally. Hybrids between C. rhynchophorus and a Mormyrus species (a more basal clade compared to Campylomormyrus s) survived up to 42 days and developed many malformations, e.g., at the level of the unpaired fins. Hybrids between C. numenius and Hippopotamyrus pictus (a derived clade, only distantly related to Campylomormyrus) only survived for two days during embryological development. Seven different hybrid combinations among five Campylomormyrus species (C. tamandua, C. compressirostris, C. tshokwe, C. rhynchophorus, C. numenius) were performed. The aim of the hybridizations was to combine species with (1) either caudal or rostral position of the main stalk innervating the electrocytes in the electric organ and (2) short, median or long duration of their EOD. The hybrids, though they are still juveniles, show very interesting features concerning electrocyte geometry as well as EOD form and duration: the caudal position of the stalk is prevailing over the rostral position, and the penetration of the stalk is dominant over the non-penetrating feature (in the Campylomormyrus hybrids); in the hybrid between C. rhynchophorus and Gnathonemus petersii it is the opposite. When crossing species with long and short EODs, it is always the long duration EOD that is expressed in the hybrids. The F1-Hybrids of the cross C. tamandua x C. compressirostris are fertile: viable F2-fish could be obtained with artificial reproduction

}, keywords = {Artificial reproduction, Campylomormyrus, Electric organ ontogeny, Hybrids, mormyrids}, issn = {09284257}, doi = {10.1016/j.jphysparis.2017.01.003}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0928425717300037}, author = {Frank Kirschbaum and Nguyen, Linh and Baumgartner, Stephanie and Chi, Linda and Wolfart, Rene and Elarbani, Khouloud and Eppenstein, Hari and Korniienko, Yevheniia and Guido-B{\"o}hm, Lilian and Victor Mamonekene and Vater, Marianne and Ralph Tiedemann} } @article {480, title = {Comparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae)}, journal = {Journal of Comparative Physiology A}, volume = {201}, year = {2015}, month = {Jan-04-2015}, pages = {357 - 374}, abstract = {

The electric organ (EO) of weakly electric mormyrids consists of flat, disk-shaped electrocytes with distinct anterior and posterior faces. There are multiple species-characteristic patterns in the geometry of the electrocytes and their innervation. To further correlate electric organ discharge (EOD) with EO anatomy, we examined four species of the mormyrid genus Campylomormyrus possessing clearly distinct EODs. In C. compressirostris, C. numenius, and C. tshokwe, all of which display biphasic EODs, the posterior face of the electrocytes forms evaginations merging to a stalk system receiving the innervation. In C. tamandua that emits a triphasic EOD, the small stalks of the electrocyte penetrate the electrocyte anteriorly before merging on the anterior side to receive the innervation. Additional differences in electrocyte anatomy among the former three species with the same EO geometry could be associated with further characteristics of their EODs. Furthermore, in C. numenius, ontogenetic changes in EO anatomy correlate with profound changes in the EOD. In the juvenile the anterior face of the electrocyte is smooth, whereas in the adult it exhibits pronounced surface foldings. This anatomical difference, together with disparities in the degree of stalk furcation, probably contributes to the about 12 times longer EOD in the adult.

}, issn = {0340-7594}, doi = {10.1007/s00359-015-0995-6}, url = {http://link.springer.com/10.1007/s00359-015-0995-6}, author = {Paul, Christiane and Victor Mamonekene and Vater, Marianne and Philine G.D. Feulner and Engelmann, Jacob and Ralph Tiedemann and Frank Kirschbaum} }