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Because of potentially strong eco-evolutionary interactions with their hosts, parasites may initiate or enhance host diversification. The adaptive radiation of cichlid fish in Lake Victoria provides a good system to study the role of parasites at different stages of host speciation. We analyzed the macroparasite infection of four replicates of sympatric blue and red Pundamilia species pairs that vary in their age and extent of differentiation. Sympatric host species differed in parasite community composition and in the infection levels of some of these parasite taxa. Most infection differences were consistent between sampling years, indicating temporal consistency in parasite-mediated divergent selection between species. Infection differentiation increased linearly with genetic differentiation. However, significant infection differences between sympatric species were only found in the oldest, most strongly differentiated Pundamilia species pair. This is inconsistent with parasite-driven speciation. Next, we identified five distinct species of Cichlidogyrus , a genus of highly specific gill parasites that has radiated elsewhere in Africa. Infection profiles of species of Cichlidogyrus differed between sympatric cichlid species only in the oldest and most differentiated pair, again inconsistent with parasite-mediated speciation. To conclude, parasites may contribute to host differentiation after speciation, but do not initiate host speciation. [ABSTRACT FROM AUTHOR]

South American peacock basses (genus Cichla) have been widely introduced within and outside the Neotropical region due to their importance to fisheries, despite threats to the native fish fauna. We performed a literature review on the worldwide distribution of valid Cichla species by focusing on records of species richness and populations in their native and non‐native ranges. We tested for an effect of area, the number of large dams, human population density and gross domestic product as drivers of the distribution of peacock basses across the Freshwater Ecoregions of the World (FEOWs). A total of 544 studies led to 1,289 records of nine species. Their distributions within their native range (19 native FEOWs) were narrower than their distributions in their non‐native range (23 non‐native FEOWs), which encompass tropical and subtropical ecoregions of the Americas, Africa, Southeast Asia and the Pacific islands. Several of these FEOWs harboured more than one species, usually C. ocellaris and C. piquiti. Ecoregion areas were positively associated with species richness and population records in native FEOWs, whereas the number of reservoirs was positively related to the records of non‐native populations. These patterns provide further evidence of the role played by reservoirs as the main pathway for the introduction of peacock basses; thus, special attention should be given to the continuous monitoring of the spread of these invaders across watersheds in invaded ecoregions. Considering their broad distribution and the potential for peacock basses to thrive in human‐modified systems, severe damage to the native fish fauna is predicted. [ABSTRACT FROM AUTHOR]

To increase understanding of the chromosomal diversity among cichlid species, karyotypes of 19 species of Cichlidae belonging to 15 genera (Paratilapia polleni, Chromidotilapia guntheri guntheri, Hemichromis fasciatus, Steatocranus irvinei, Stomatepia pindu, Altolamprologus compressiceps, Julidochromis transcriptus, Neolamprologus tetracanthus, N. brevis, Gnathochromis permaxillaris, Eretmodus cyanostictus, Astatoreochromis alluaudi, Haplochromis callipterus, H. paludinosus, Nimbochromis livingstonii, N. polystigma, Pseudocrenilabrus multicolor victoriae, P. philander and Ctenochromis horei) were investigated for the first time. In spite of the variation in the karyotypes of cichlid fishes (from 2n = 42 to 2n = 48 chromosomes), the modal chromosome number was 2n = 44. Cytogenetic mapping of the 18S ribosomal RNA (18S rRNA) gene was accomplished. [ABSTRACT FROM AUTHOR]

This study quantifies the behavioral response of the widespread mouth brooding African cichlid Pseudocrenilabrus multicolor victoriae to progressive hypoxia. We exposed four gender/stage classes of P. multicolor (males, brooding females, females that had just released young, and non-brooding females) to progressive hypoxia and recorded the percent time spent using aquatic surface respiration (surface skimming, ASR) and gill ventilation rates. This was done for fish collected from three sites in Uganda (lake, swamp, and river) after long-term acclimation to normoxia. There was no effect of site of origin on response to hypoxia, but ASR thresholds did differ between gender/stage classes. The oxygen level (threshold) at which spent 10, 50, and 90% of their time at the surface using ASR was much higher for brooding females than for males, whereas ASR thresholds did not differ between non-brooding females and males. Similarly, the level at which ASR was initiated was much higher in brooding females than males, but did not differ between males and non-brooders, or between males and females than had just released young. The rate of gill ventilation dropped significantly in males and all stages of females after initiation of ASR, suggesting that surface skimming increases efficiency of oxygen acquisition. These results suggest that mouth brooding in female P. multicolor ASR improves oxygen uptake but imposes a cost in terms of time spent at the water surface, and this may affect maternal predation risk in low-oxygen habitats. [ABSTRACT FROM AUTHOR]

In this study we investigate the possible role of phenotypic plasticity and genetic assimilation in the process of adaptation and evolutionary change in the cichlid Pseudocrenilabrus multicolor victoriae. In the field we compared a population of a stable hypoxic habitat with one of a stable well-oxygenated habitat. In the laboratory, we compared individuals from the same mother raised under hypoxic or well-oxygenated conditions to examine phenotypic plasticity. Morphological parameters of three categories were measured: (a) the gill apparatus, (b) the surrounding structural elements, and (c) the outer shape of the fish. Swamp-dwelling fish had a 29% greater total gill surface area than fish from the well-oxygenated habitat due to their larger gill filament length and greater lamellar area. In the plasticity experiment, total gill surface area was 18% greater in the hypoxia group due to a larger number of longer filaments. Surrounding elements and outer shape also differed between the field populations and between fish grown under hypoxic and well-oxygenated conditions, but there was disparity between the field results and the plasticity experiment. The disparity between field and experimental fish may be due to: (a) differences in selection pressures between populations, (b) different constraints for genetic and plasticity changes, or (c) selection against plastic responses to hypoxia. Our results suggest that both (a) and (c) are involved. [ABSTRACT FROM AUTHOR]

Sounds were produced by the males of two species of cichlid fishes while courting females. Each courtship sound consisted of a series of distinct pulses occurring in rapid succession. Courtship sounds produced by Tramitichromis c£ intermedius and copadichromis conophorus were significantly different, in pulse rate and individual pulse durations. For C. conophorus calls (n = 127) the mean ± sd number of pulses per call was 10±3 and call duration was 181 ± 59 ms. There was a significant positive linear relationship between call duration and the number o,i pulses (r² = 0.912, p <0.001). The dominant frequency of the pulses in calls was 471 ±50 (range 372-594) Hz (n = 40 calls). T ef. intermedius also produced a pulsed courtship call: data (mean ± sd) from two male T. cf. intermedius: 9 ±2 pulses per call and duration 199 ±44 ms (n = 20 calls). The linear regression between call duration and number of pulses was positive (r² = 0.463, p 0.001). Pulse rate within calls of T. ef. intermedius compared to C. conophorus were significantly different (p= 0.018). Individual pulse durations were also significantly different (p= 0.043) between species. However, interpulse intervals were not significantly different (p = 0.177). These cichlids produced courtship sounds that were distinct by individual pulse durations and by pulse repition rate in a call. [ABSTRACT FROM AUTHOR]

Climate‐induced habitat change has often been invoked as an important driver of speciation and evolutionary radiation in cichlid fishes, yet studies linking morphological change directly to long‐term environmental fluctuations are scarce. Here, we track changes through time in the oral dentition of Oreochromis hunteri, the endemic and only indigenous fish species inhabiting the East African crater Lake Chala (Kenya/Tanzania), in relation to climate‐driven lake‐level fluctuations during the last 25,000 yr. Fossil teeth were recovered from six periods representing alternating high and low lake‐level stands associated with late‐Pleistocene and Holocene trends in rainfall and drought. To construct a reference framework for morphological variation in fossil assemblages, we first analyzed the variability in oral tooth morphology within the modern‐day fish population. These analyses established that, like other cichlids, O. hunteri gradually replace their bicuspid/tricuspid oral dentition with more unicuspid teeth as they grow. In the fossil assemblages, we found systematic and recurrent changes in the relative abundance of these oral tooth types, with a higher proportion of unicuspids during low‐stands. Moreover, O. hunteri living during low‐stands systematically developed unicuspid dentition at a smaller body size, compared with conspecifics living during high‐stands. Considering that low‐stand conditions created a sizable area of oxygenated soft‐bottom habitat that is lacking during high‐stands, we propose that the associated change in oral dentition reflects the fishes' exploitation of this new habitat either for feeding or for reproduction. The recurrent nature of the observed shifts provides evidence for the ability of O. hunteri to systematically adapt to local habitat change, and strongly suggests that morphological change in oral dentition promoted its long‐term population persistence in an aquatic ecosystem presenting the dual challenge of being both sensitive to climate change (creating constantly shifting selective pressures) and isolated from surrounding populations (limiting gene flow). In Lake Chala, ancient climate‐driven lake‐level fluctuations did not directly promote speciation in O. hunteri, but the population bottlenecks they may have caused potentially contributed to its divergence from sister species Oreochromis jipe. [ABSTRACT FROM AUTHOR]