02043nas a2200205 4500008004100000022001400041245014400055210006900199260001600268300001400284490000800298520134200306100002601648700001701674700002701691700002001718700002101738700002201759856005601781 2020 eng d a0340-759400aIntragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua ♂ × C. compressirostris ♀) are fertile0 aIntragenus F1hybrids of African weakly electric fish Mormyridae  cJan-07-2020 a571 - 5850 v2063 a

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.

1 aKorniienko, Yevheniia1 aNguyen, Linh1 aBaumgartner, Stephanie1 aVater, Marianne1 aTiedemann, Ralph1 aKirschbaum, Frank uhttp://link.springer.com/10.1007/s00359-020-01425-702385nas a2200157 4500008004100000022001400041245011300055210006900168260001600237520163800253100002601891700002101917700002001938700002201958856024701980 2020 eng d a0021-996700aOntogeny of the electric organ discharge and of the papillae of the electrocytes in the weakly electric fish0 aOntogeny of the electric organ discharge and of the papillae of  cDec-08-20203 a

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.

1 aKorniienko, Yevheniia1 aTiedemann, Ralph1 aVater, Marianne1 aKirschbaum, Frank uhttps://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