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The biological life cycle, reproductive behavior and egg development of Nothobranchius species is perfectly adapted to the special conditions of the seasonal biotopes in which they occur. The adult fish deposit eggs into the muddy substrate of the habitat where they survive the dry season while undergoing development with intervening rest periods....
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... The cyprinodontiform fish genus Nothobranchius Peters, 1868 currently comprises 96 valid species, occurring mainly in seasonal wetlands of river drainages in northeastern, eastern and south-eastern Africa that are subject to seasonal rainfall . All known species feature an annual or semi-annual life cycle as a key adaptation to reproduce in an unpredictable biome of temporary freshwater pools that appear during monsoons, and which become desiccated during the dry season (Vanderplank 1940;Watters 2009;Nagy 2015). Because of their life cycle, annual killifishes form small populations with non-overlapping generations that are biogeographically isolated. ...
The karyotype differentiation of the twelve known members of the Nothobranchius ugandensis Wildekamp, 1994 species group is reviewed and the karyotype composition of seven of its species is described herein for the first time using a conventional cytogenetic protocol. Changes in the architecture of eukaryotic genomes often have a major impact on processes underlying reproductive isolation, adaptation and diversification. African annual killifishes of the genus Nothobranchius Peters, 1868 (Teleostei: Nothobranchiidae), which are adapted to an extreme environment of ephemeral wetland pools in African savannahs, feature extensive karyotype evolution in small, isolated populations and thus are suitable models for studying the interplay between karyotype change and species evolution. The present investigation reveals a highly conserved diploid chromosome number (2n = 36) but a variable number of chromosomal arms (46-64) among members of the N. ugandensis species group, implying a significant role of pericentric inversions and/or other types of centromeric shift in the karyotype evolution of the group. When superimposed onto a phy-logenetic tree based on molecular analyses of two mitochondrial genes the cytogenetic characteristics did not show any correlation with the phylogenetic relationships within the lineage. While karyotypes of many other Nothobranchius spp. studied to date diversified mainly via chromosome fusions and fissions, the N. ugandensis species group maintains stable 2n and the karyotype differentiation seems to be constrained to intrachromosomal rearrangements. Possible reasons for this difference in the trajectory of karyotype differentiation are discussed. While genetic drift seems to be a major factor in the fixation of chromosome rearrangements in Nothobranchius, future studies are needed to assess the impact of predicted multiple inversions on the genome evolution and species diversification within the N. ugandensis species group.
... The cyprinodontiform fish genus Nothobranchius Peters, 1868 currently comprises 95 valid species . They are recognised as seasonal fishes, commonly also referred to as annuals, with all known species having an annual or semi-annual life cycle (Peters 1963), an adaptation to the periodic drying up of their natural habitats, where they reproduce in the seasonally arid savannah biome (Vanderplank 1940;Watters 2009;Nagy 2015). Species of the genus occur in river drainages that are subject to seasonal rainfall (Wildekamp 2004;Watters 2009Watters , 2014 in which they inhabit ephemeral pools in the African ichthyological provinces as defined by Roberts (1975) and modified by Lévêque (1997): Nilo-Sudan, East Coast, Zambezi and Congo (van der Merwe et al. 2020); they are distributed from southern Sudan to KwaZulu-Natal in South Africa, and from Chad to Zanzibar and Mafia islands in Tanzania . ...
... The seasonal life cycle of Nothobranchius fishes, including N. ocellatus, has evolved through a unique suite of reproductive adaptations to enable them to persist in seasonal wetlands, under the characteristically erratic rainfall regime of semi-arid savannahs (Watters 2009;Nagy 2015). Eggs are deposited in the soft, black or grey mud of the habitat substrate that, critically, has characteristics typical of a vertisol, which includes a significant component of swelling clay minerals of the smectite group, thereby providing conditions necessary for the eggs to remain viable through the dry season (Watters 2009;. ...
During the course of a taxonomic study involving Nothobranchius ocellatus, a fast-growing seasonal killifish of predatory behaviour, important morphometric differences were observed between the original measurements of the lost holotype and the neotype and additional available material of the species. In a laboratory study, the total length (TL) of selected specimens was measured from hatching and, during the sub-adult to sexually mature young adult phase, from 37 to 84 days age, subjected to an additional suite of detailed morphometric measurements. Growth rate was relatively rapid and linear at 1.3-1.4 mm/day through the first phase to sexual maturity at 7-8 weeks, followed by a marked flattening of the growth curve with, from 14 weeks, rates of only about 1.0 mm/week in males and 0.6 mm/week in females. Under captive conditions, maximum TL for adult male specimens ranged from 101 to 116 mm and 88 to 102 mm for females. Analyses of the morphometric character measurements made during the 37-84 day development phase showed allometric shape changes, primarily seen in body depth, head length and several other measures of head features, proportions of caudal peduncle, and length of fin bases. These changes are most prominently seen in males and changes in head proportions are important in relation to the predatory behaviour of the species. Morphometric differences between the immature holotype and the newly available material, including the neotype, are consistent with allometric shape variation, particularly in males of this species. Considering the seasonal life cycle common to all Nothobranchius species, and similar growth patterns, it is likely that allometric growth has broad relevance within the genus, suggesting it is a factor that should be taken into account in taxonomic endeavours, especially when the number of study specimens is limited.
... Lampeyes are largely distributed from the western Sahel region to southern Africa (Wildekamp, 1995;Seegers, 1997). It is an ecologically diverse group of fishes, with species occupying distinct habitats, such as small streams, but also swamps, ponds and lakes, and brackish water estuaries (Nagy, 2015;Watters, 2015Watters, , 2017. Within the family, species are currently classified into twelve genera, comprising about 80 valid species (Wildekamp, 1995;Huber, 1999;Lazara, 2001;Seegers, 1997;Bragança & Costa, 2019). ...
Lacustricola margaritatus, a new species inhabiting small streams and swamps in the Lake Victoria basin in northwestern Tanzania and southern Uganda, and the Lake Kyoga basin in central Uganda, is described. Lacustricola margaritatus is a small species with a moderately deep body, moderate dimorphism and pronounced dichromatism. It is distinguished from all other Procatopodidae by the following unique combination of characters: live male body colour pattern with vertically-elongated iridescent light blue patches at scale centres, forming a striped appearance of dotted longitudinal lines on the flanks, particularly evident in the two or three series below the mid-longitudinal line; male having deeply coloured unpaired fins with orange-brown in the proximal and median parts and a narrow black distal band; male with a yellow base along the pectoral fin; female with dark grey scale margins and dark grey patches on scales along mid-longitudinal series creating a narrow dark grey stripe; both sexes showing inconspicuous postopercular blotch; and in both sexes, the cephalic sensory system is entirely situated in open grooves at all levels. The new species has previously often been misidentified as L. pumilus, originally described as inhabiting the Lake Tanganyika basin in northeastern Zambia, or 'L.' centralis, from the Lake Rukwa basin in southwestern Tanzania. Lacustricola margaritatus differs from the above two species by morphometric and meristic characters, body and fin colouration, and in arrangement of the cephalic sensory system.
... periodic drying out of their natural habitats (Vanderplank, 1940;Watters, 2009;Nagy, 2015). The 56 periodicity is determined by the rainfall pattern of the regions in which the habitats occur. ...
... This is especially common in the coastal region of Tanzania ( Figure 2). Usually, each 289 species would occupy a different niche of the biotope (Nagy, 2015). 290 ...
The small and colourful Nothobranchius fishes inhabit ephemeral habitats in freshwater wetlands of Africa and have extreme life‐history adaptations that allow their eggs to survive the periodic drying up of the seasonal natural habitats. They are subject to high levels of threat, with 72% of the 94 assessed species falling into one of the threatened Red List categories, as a consequence of habitat degradation of seasonal wetlands. There is, therefore, a need to conserve ephemeral waters for species that rely on the seasonality of habitats.
Extinction risk factors for all species of the genus were entirely reworked with IUCN Red List assessments, whereas first‐time assessments were established for species that had previously not been evaluated. These fishes complete their seasonal life cycle in ephemeral natural habitats and this makes them highly vulnerable, as such wetland habitats are often degraded owing to multiple interacting human‐induced stressors and threats, including cultivation of wetlands for agriculture, abstraction of water, expansion of urban areas and pollution load.
A fine‐scale classification scheme based on habitat type was used for each site to identify ecological characteristics and the pattern of threats. The classification scheme is based on a primary subdivision of natural habitats compared with those modified by human activities, with further subdivision within the two fundamental groupings. Out of the 478 analysed habitat site observations by the authors, 46% were affected by human activities.
Recommended conservation actions include: conducting surveys to better understand habitat trends and threats; establishing protected areas and effectively allocating resources to preserve wetland habitats; managing protection of the structural integrity of the habitats throughout the seasonal phases of wet and dry seasons; and raising awareness of the importance of healthy wetland systems and the value of the unique seasonal freshwater biodiversity.
... Species of the genus Nothobranchius are characterized by the following life history traits: a relatively small adult size, most species reaching 30-70 mm in standard length (SL), with only a few surpassing 100 mm SL; adaptation to unstable climatic and environmental conditions; producing large numbers of eggs to ensure a potentially adequate number of offspring; no parental care, nor protection of the offspring; a low ability to compete, with most offspring dying before reaching reproductive age (Nagy 2015). ...
Nothobranchius nikiforovi, a new species known from seasonal habitats in the lower Matandu drainage in south-eastern coastal Tanzania is described. It is distinguished from all other congeners, except N. eggersi, by males presenting two colour phenotypes: the blue phenotype having a bright iridescent light blue to blue-green body, with narrow red-brown scale margins creating irregular reticulated pattern, forming chevron-shaped crossbars on the posteroventral portion of body and light blue median fins with red-brown dotted pattern; the red phenotype has a dark red head, light blue dorsal and anal fins proximally and medially, dark red distally, with dark red stripes parallel to the fin rays, and a plain dark red caudal fin. Nothobranchius nikiforovi differs from N. eggersi by male colour pattern, the blue phenotypes having median fins with dark grey distal portion, some of the rays of dorsal and anal fins with white tips (vs. median fins with distinct slender white distal band), and the caudal fin lacking a spotted pattern (vs. dots arranged into irregular curved stripes); the red phenotype with golden stripe between the nape and dorsal-fin origin (vs. light-blue stripe), the dorsal and anal fins with a plain red distal portion and lacking a light distal band (vs. with distinct narrow white distal band), the pelvic fin lacking a distal band (vs. with distinct slender light blue to white distal band), and some morphometric differences. Phylogenetic analyses also support the genetic distinction of the new species from its closest known relative, N. eggersi, and confirm its position in the N. guentheri species group within the Adiniops subgenus.
... They are distributed from southern Sudan in the north to KwaZulu-Natal in South Africa in the south, and from western Chad in the west to eastern coastal Somalia, Zanzibar and Mafia islands off coastal Tanzania, and coastal Mozambique in the east (Wildekamp 2004;Watters 2009). They are recognized as seasonal fishes, commonly also referred to as annuals, with all known species having an annual or semi-annual life cycle (Peters 1963), a key adaptation to reproduce in the seasonally arid savannah biome characterized by the periodic drying out of their natural habitats (Watters 2009;Nagy 2015). ...
... The distinctive colour pattern of the males provides important diagnostic characters (e.g. Wildekamp 1978;Jubb 1981;Nagy 2018a), whereas little intra-specific morphological variation is known to occur (Nagy 2014(Nagy , 2015Reichard 2015). The genus has gained particular interest as it includes N. furzeri, the vertebrate species with the shortest lifespan recorded in captivity, which emerged as a model organism for investigating biological and molecular studies of ageing (e.g. ...
Nothobranchius elucens, new species, from a seasonal habitat in the Aringa system of the Achwa River in the upper Nile drainage in northern Uganda, is described. It belongs to the N. rubroreticulatus species group, whose members are characterised by male coloration of anal and caudal fins with slender light blue subdistal band and slender dark distal band. Nothobranchius elucens is distinguished from all other members of the genus by the following characters in males: body colouration golden-grey with brown scale margins creating irregular vertical stripes on trunk; anal fin yellow with brown spots proximally, with slender brown median band, followed by a slender light blue subdistal band and a slender black distal band; caudal fin brown proximally and medially, followed by a slender light blue subdistal band and a slender black distal band; dorsal fin golden with irregular brown stripes and narrow light blue subdistal band and with narrow black distal band. Furthermore, it differs from the closest known relative, N. taiti, also by the morphometric characters of having a smaller head length of 29.5-33.1 % SL; smaller prepectoral length of 31.2-33.9 % SL; greater head depth of 81-87 % HL; greater interorbital width of 43-49 % HL; and greater caudal peduncle length of 145-152 in % of its depth.
... The hydromorphic properties of these "cracking clay" substrates explain their key role as the primary determinants of the patchy occurrences of these small fishes across tropical landscapes; and, critically, how they persist in arid savannahs despite desiccation of their ephemeral pond habitats. Annualism, a life habit being found more often in the tropics, enables Nothobranchius to reproduce in the seasonally dry habitats of African savannahs, and a unique suite of reproductive adaptations defines the annual life histories of Nothobranchius (Watters, 2009;Nagy, 2015). Eggs are deposited in the soft mud of the habitat substrate, which has the typical characteristics of a vertisol; critically, the constituent smectite group minerals (mainly montmorillonite) have the capacity to absorb and adsorb water molecules between the layers of their crystal structures, and onto the grain surfaces, respectively. ...
... As many as three stages of diapause can interrupt the developing embryo within the egg (Peters, 1963;Wourms, 1965Wourms, , 1972aWourms, , 1972bWourms, , 1972cFurness et al., 2015;Pinceel et al., 2015). After hatching at the onset of the wet season, the fry grow rapidly, with sexual maturity attained within three weeks to two months (Markofsky and Matias, 1977;Nagy, 2015;Watters, 2009). It has further been shown by Vrtílek et al. (2018) that N. furzeri, the shortest-lived Nothobranchius species can, in its natural environment, be sexually mature within two weeks. ...
This paper reports a phylogeny of the African killifishes (Genus Nothobranchius, Order Cyprinodontiformes) informed by five genetic markers (three nuclear, two mitochondrial) of 79 taxa (seven undescribed and 73 of the 92 recognized species). These short-lived annual fishes occupy seasonally wet habitats in central and eastern Africa, and their distribution coincides largely with the East African Rift System (EARS). The fossil dates of sister clades used to constrain a chronometric tree of all sampled Nothobranchius recovered the origin of the genus at ∼13.27 Mya. It was followed by the radiations of six principal clades through the Neogene. An ancestral area estimation tested competing biogeographical hypotheses to constrain the ancestral origin of the genus to the Nilo-Sudan Ecoregion, which seeded a mid-Miocene dispersal event into the Coastal ecoregion, followed closely (∼10 Mya) by dispersals southward across the Mozambique coastal plain into the Limpopo Ecoregion. Extending westwards across the Tanzanian plateau, a pulse of radiations through the Pliocene were associated with dispersals and fragmentation of wetlands across the Kalahari and Uganda Ecoregions. We interpret this congruence of drainage rearrangements with dispersals and cladogenic events of Nothobranchius to reflect congruent responses to recurrent uplift and rifting. The coevolution of these freshwater fishes and wetlands is attributed to ultimate control by tectonics, as the EARS extended southwards during the Neogene. Geobiological consilience of the combined evidence supports a tectonic hypothesis for the evolution of Nothobranchius.
... The Cyprinodontiform fish genus Nothobranchius Peters, 1868 currently comprises 92 valid species. They are recognised as "annuals", with all known species having an annual or semi-annual life cycle (Peters, 1963), an adaptation to the periodic drying up of their natural habitats, where they reproduce in the seasonally arid savannah biome (Watters, 2009;Nagy, 2015). Species of the genus occur in river drainages that are subject to seasonal rainfall (Seegers, 1997;Watters, 2009Watters, , 2014 in which they inhabit ephemeral pools in the African ichthyological provinces as defined by Roberts (1975) and modified by Lévêque (1997): Nilo-Sudan, East Coast, Zambezi and Congo; they are distributed from southern Sudan to KwaZulu-Natal in South Africa, and from Chad to Zanzibar and Mafia islands in Tanzania. ...
... The seasonal life cycle of Nothobranchius fishes, including both members of the N. ocellatus species group, has evolved through a unique suite of reproductive adaptations to enable them to persist in seasonal wetlands, under the characteristically erratic rainfall regime of semi-arid savannahs (Watters, 2009;Nagy, 2015). Eggs are deposited in the soft, black or grey mud of the habitat substrate that, critically, has characteristics typical of a vertisol, which include a significant component of swelling clay minerals of the smectite group. ...
The description of Nothobranchius ocellatus was based on a unique holotype, comprising an immature male, and a photograph of a female. The holotype is apparently lost. The species is here redescribed in detail, and a neotype designated from a site near the original type locality. The range of distribution of the species is within the lower Rufiji and lower Ruvu river systems, contained within intersecting, tectonically-controlled and hydrologically-linked graben structures, the Rufiji Depression and Ruvu Valley Trough, and at relatively low elevations. Disjunct populations in the Matandu River drainage, previously regarded as the same species, are described as Nothobranchius matanduensis Watters, Nagy & Bellstedt, new species. The latter species occurs at significantly higher elevations than those of N. ocellatus and appears confined to a part of coastal Tanzania that has been tectonically relatively stable. The two species comprise the 'Nothobranchius ocellatus species group'. Differences in diagnostic characters between N. matanduensis and N. ocellatus are presented, the most obvious of which are grey scale margins and black spots on the head of males of the former (vs. red-brown scale margins and red-brown spots on the head of the latter). Further differences in colour pattern and morphology of both males and females of the two species are described in detail, and differences in cephalic sensory systems are also noted. Genetic divergence in partial sequences of the mitochondrial genes, ND2 and COI, and three nuclear genes, Glyt, MyH6 and SNX33, supports the genetic distinction of the two species within a well-defined N. ocellatus Clade, which is deeply rooted in Nothobranchius, thereby also confirming the subgenus status of Paranothobranchius. The ecology and biology of the species group is reviewed; both species are relatively large and piscivorous in nature, occupy seasonal habitats, and always occur syntopically with various other, smaller, Nothobranchius species.
... Species occur in river drainages of eastern and southeastern Africa that are subject to seasonal rainfall (Seegers, 1997;Watters, 2009). They are recognised as annuals, with all known species having an annual or semi-annual life cycle (Peters, 1963) geared to the periodic drying up of their natural habitats, where they reproduce in the seasonally arid savannah biome (Nagy, 2015). They inhabit temporary pools and swamps during the rainy season (Skelton, 2001). ...
Nothobranchius taiti, new species, is described from seasonal habitats in the Apapi River system, forming part of the Lake Kyoga basin in the upper Nile drainage in eastern Uganda. Nothobranchius taiti is distinguished from all other members of the genus by the following characters in males: body coloration light blue with seven to ten irregular red-brown vertical stripes; anal and caudal fins light blue with brown spots proximally, with brown median band, followed by a light blue subdistal band and a black distal band; dorsal fin golden with brown spots and irregular brown stripes and with slender black distal band. Furthermore, it differs from N. taeniopygus, a species to which it has previously been tentatively ascribed, by having a greater head length of 35.0-38.6 % SL; smaller head width of 50-57 % HL; smaller head depth of 71-80 % HL; smaller interorbital width of 31-40 % HL; and smaller postorbital length of 44-51 % HL.
... Nothobranchius killifish grow and mature rapidly, spawn continuously and lay tough, drought-resistant eggs in the substrate. Embryonic development is phased and suspended for variable periods (diapause) in tune with drought and rainfall periodicity (Nagy, 2014). Sharptooth catfish spawn on flooded grassy shores of lakes and rivers with the onset of rains and local floods (Bruton, 1979b). ...
Despite their often temporary nature, intermittent rivers and ephemeral streams (IRES) provide important habitat, resource advantages, and nurseries for a range of fish species throughout the world. Fishes have adapted to the variable nature of these environments. A small subset of species using IRES has evolved specific traits such as air-breathing that make living in extreme habitats possible, but the majority relies on opportunistic dispersal to colonize such areas. Fish existence in IRES is precarious but when conditions are favorable, fishes play major roles in ecosystem functioning (e.g., trophic links in food webs). Habitat fragmentation of IRES by water extraction, river regulation, and climate change is the biggest threat to their ecological integrity and has major implications for the distribution and abundance of fishes in IRES.
