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Parananochromis moutingae (Teleostei: Cichlidae): a new species from Central Africa, and the first record of the genus in the Congo River basin
Abstract
Parananochromis moutingae, new species, is the first species of Parananochromis to be recorded as endemic to the Congo Basin. It is recorded from the Lefini, Lebomo, and Mayi Ndombe Rivers in the middle Congo. Paranano- chromis moutingae is distinguished from all congeners by a unique combination of the following meristic and morphological characters: three tubular infraorbital bones; a well-developed hanging pad on the pharynx roof; more scales between the dorsal-fin origin and the upper lateral line (5.5-6.5); more small scales between pectoral and pelvic fin insertions (8-10); presence of scales on the chest; more gill rakers on the lower limb of the first gill arch (8-9); more teeth (5-7) on pharyngobranchial 2 of upper pharyngeal jaw; longer snout (32-39 % HL); longer predorsal distance (33.9-36.1 % SL); broader than long lower pharyngeal jaw; straight urohyal spine; and slightly indented ventral margin of the lower pharyngeal keel. Despite concerted efforts, the species has not been collected in the Lefini River since its original discovery in 2008, probably as a result of the installation of a hydroelectric dam, but it seems to subsist in the other two locations.
Parananochromis moutingae, nouvelle espèce, est la première du genre qui soit endémique du bassin du Congo. L’espèce est présente dans les rivières Lefini, Lebomo et Mayi-Ndombe dans le Moyen Congo. Parananochromis moutingae se distingue de tous ses congénères par la combinaison unique des caractères méristiques et morphomé- triques suivants : trois infra-orbitaires tubulaire; un coussinet papilleux bien développé de chaque côté du pharynx; nombre élevé d’écailles entre la première ligne latérale et l’origine de la nageoire dorsal (5,5-6,5) ; nombre élevé des petites écailles entre la nageoire pectorale et le point d’insertion de la nageoire ventrale (8-10); la présence d’écailles sur la poitrine; grand nombre de branchiospines sur la partie inférieure du première arc branchial (8-9); nombre élevé de dents (5-7) sur les parties antérieures de l’os pharyngé supérieur; long museau (32-39% Ltête); grande distance prédorsale (33,9-36,1 % LS); l’os pharyngé inférieur plus large que long; pointe de l’urohyal droite; et la marge ventrale de l’os pharyngé inférieur légèrement échancrée. Malgré les efforts de collecte, l’espèce n’a plus été retrouvée récemment dans la rivière Lefini depuis sa récolte en 2008, probablement suite à l’installation d’un barrage hydroélectrique sur la rivière Lefini, mais elle semble subsister encore dans les deux autres localités.
Background
The iconic freshwater cichlid fishes (Cichlidae) comprise about 1750 validly named species and hundreds more that are known, but not yet described and named. Cichlids are an important source of protein for millions of people on several continents, are model organisms in studies of evolution, speciation, ecology, development, behaviour and physiology and are popular as aquarium fishes. Yet, comparative studies of cichlid internal anatomy are rare. Even their osteology has not been taxonomically surveyed. The cichlid postcranial skeleton has been especially neglected.
New information
Here, I provide the first survey in cichlids of the considerable variation in numbers of vertebrae, supraneurals and dorsal- and anal-fin supports (pterygiophores), as well as the patterns with which the pterygiophores insert between the neural or haemal spines. The study includes some 1700 specimens of nearly 400 cichlid species. Focusing on the largest subfamily, the African cichlids or Pseudocrenilabrinae, the survey furnishes data from species in all but one of its 166 genera. Limited data from species in the other cichlid subfamilies (Etroplinae, Ptychochrominae and Cichlinae) and from the related leaffishes, Polycentridae, are also presented. Key examples of pterygiophore insertion patterns from throughout the range of variation are illustrated and discussed. Detailed analytical tables and all raw data are provided in supplementary files.
A bizarre specialisation in Cyprichromis is noted, evidently for the first time. Uniquely in this Lake Tanganyikan genus, five to seven anal pterygiophores are abdominal in position, located anterior to the anal fin and inserting toward or between successive pairs of pleural ribs.
Taxonomic changes: The most speciose tribe of African cichlids, currently known as Haplochromini, is correctly called Pseudocrenilabrini. Based chiefly on the molecular phylogenetic findings of other workers, I propose four pseudocrenilabrine subtribes, one occurring in rivers and three endemic to Lake Malawi. I also re-assign the Lake Tanganyikan tribe Tropheini as another subtribe of Pseudocrenilabrini, in line with numerous molecular studies placing tropheines firmly within this tribe. The remaining genera of Pseudocrenilabrini remain incertae sedis in this tribe pending clarification of their phylogenetic relationships.
The character complex here surveyed is a promising source of taxonomically and phylogenetically informative characteristics distinguishing or uniting cichlid taxa at multiple hierarchical levels, from species through subfamily. This reference set of novel character data can also provide information for palaeontological studies of African cichlids. These attributes are skeletal features potentially available for study in well preserved fossils and may help determine their correct taxonomic placement.
Basin-scale planning is needed to minimize impacts in mega-diverse rivers
Parananochromis axelrodi , P. brevirostris and P. ornatus, three new cichlid species, are described from Gabon and southern Cameroon. Parananochromis axelrodiis a deep-bodied species differing from congeners in a combination of morphometric and meristic characters. Parananochromis brevi- rostris and P. ornatus are distinguished by the presence of four elements in the infraorbital series versus five elements in congeners. Parananochromis brevirostrisdiffers from P. ornatus in lacking chest squamation and in the presence of a weakly-developed pharyngeal pad (versus well-devel- oped pad and scaled chest in P. ornatus).
More than 40 years ago in their compendium of fish diversity in the lower Congo River (LCR), T. R. Roberts and D. J. Stewart posed the question, “Why does the LCR harbor so many cichlids?” Here we seek an answer through a synthesis of the last 40+ years of research on cichlid diversity, ecology, and speciation. Our review suggests a key role for the unique geomorphology and hydrology of the river itself and its history of connectivity to other African freshwater ecosystems. In contrast to the river upstream of Pool Malebo, the LCR channel is entirely bedrock, and littoral habitats are mostly rocky and rock-strewn. In situ measurements have recorded dramatic changes in channel topology, fluctuating bed bathymetry, and regions of extreme depth. A combination of high annual discharge, steep elevational decline, and fluctuating channel width and depth result in extraordinarily high-energy flow regimes throughout the LCR. In-stream hydraulics and bathymetry appear to play a key role in isolating cichlid populations and are likely powerful drivers for micro-allopatric isolation and speciation, often over remarkably small geographical scales. Moreover, this hydrologically extreme environment is the evolutionary backdrop for an unusual array of cichlid morphologies, including the only known blind cichlid (Lamprologus lethops).
Geographical distribution of African freshwater fishes is discussed with emphasis on the effects of major continental features, hydrographic history, and Pleistocene climatic fluctuations. Differences in the modes of dispersal and biological interactions among various categories of fishes, ecological as well as phyletic, have also had marked effects on distribution. The African continent can be divided into ten ichthyofaunal provinces. The geography of these provinces and composition of their fish faunas is briefly described. The paper concludes with a consideration of the faunistic relationships of African lakes with endemic fishes.
Parananochromis elobatus, new species, is an elongate species distinguished from congeners by the combination of: three tubular infraorbital bones, scales absent from the chest, a weakly developed pharyngeal pad, and short dorsal fin lappets. Parananochromis orsorum, new species, is diagnosed by the presence of four tubular infraorbitals, pelvic fin with black tips in females, and absence of silvery dots on body scales of males.
African cichlids formerly referred to as "Tilapia" represent a paraphyletic species assemblage belonging to the so called haplotilapiine lineage which gave rise to the spectacular East African cichlid radiations (EARs) as well as to globally important aquaculture species. We present a comprehensive molecular phylogeny of representative haplotilapiine cichlids, combining in one data set four mitochondrial and five nuclear loci for 76 species, and compare it with phylogenetic information of a second data set of 378 mitochondrial ND2 haplotypes representing almost all important "Tilapia" or Tilapia-related lineages as well as most EAR lineages. The monophyly of haplotilapiines is supported, as is the nested sister group relationship of Etia and mouthbrooding tilapiines with the remaining haplotilapiines. The latter are consistently placed in eight monophyletic clades over all datasets and analyses, but several dichotomous phylogenetic relationships appear compromised by cytonuclear discordant phylogenetic signal. Based on these results as well as on extensive morphological evidence we propose a novel generic and suprageneric classification including a (re-)diagnosis of 20 haplotilapiine cichlid genera and nine tribes. New tribes are provided for the former subgenera Coptodon Gervais, 1853, Heterotilapia Regan, 1920 and Pelmatolapia Thys van den Audenaerde, 1969, in addition for "Tilapia" joka, Tilapia sensu stricto and Chilochromis, Etia, Steatocranus sensu stricto, the mouthbrooding tilapiines and for a clade of West African tilapiines.
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