Large Barbs Research Articles

Phenetic relationships and probable ways of morphological diversification of the African large barbs (Barbus intermedius complex) in Lake Tana (Ethiopia)

29 quantitative and 18 qualitative skull characters were studied in the African large barbs (Barbus intermedius complex) from Lake Tana (Ethiopia). Based on results of principle components analysis phenetic relationships of 12 morphotypes were assessed. External features diagnostic of the morphotypes were found in individuals substantially different in the skull characters. The obtained data along with the data on morphological diversity of large barbs from Ethiopia beyond the Lake Tana basin suggest origination of the Lake Tana complex of forms from a complex of forms that existed in the upper reaches of the Blue Nile before the lake came into being, and the extant morphotypes of the Lake Tana barbs originated from three or four forms that composed the ancestral riverine local complex.

Individual ontogenetic trajectories and ontogenetic channels of three forms of large African barbs (Barbus intermedius complex). Analysis of experimental data

Changes of external morphological characters in three forms (morphotypes) of African barbs from Lake Tana (Ethiopia) belonging to Barbus intermedius complex were traced using electronic tags. It was shown that within age interval from two to four years individual ontogenetic allometric curves often cannot be described with a single power function equation. Individual ontogenetic trajectories in the principal components space within this interval strongly differ in shape meandering within ontogenetic channels outlined on the basis of cross-sectional data. Morphological differences between siblings are found that do not allow to classify some of them with the morphotype of their parents.

Influence of thyroid hormone on the sequence of cranial bones appearance in early ontogeny of the large African barb (Labeobarbus intermedius; Cyprinidae; Teleostei)

Influence of thyroid hormone on the sequence of cranial bones appearance in early ontogeny of the large African barb (Labeobarbus intermedius; Cyprinidae; Teleostei)

Thyroid responsiveness of the large African barb Labeobarbus intermedius (Teleostei; Cyprinidae): Individual variability and morphological consequences

Thyroid hormones (THs), produced by the thyroidgland, play an important role in the regulation of ontog-eny in bony fishes. They influence the rate of individualdevelopment of the body as a whole, as well as the ratesof growth and differentiation of its particular structures[1]. Definitive morphology of fishes is a result of inter-action between the developing body and a hormone,and depending on the TH level and an ability of thebody to respond to TH, i.e., TH-responsiveness.The TH level depends on the functional activity ofthe thyroid gland. A low activity and, as a result, lowTH levels lead to slowing down the ontogeny. On thecontrary, high TH levels accelerate the ontogeny [1, 2].Differences in the activity of the thyroid gland canresult in variability of the expression of morphologicalfeatures [2]. Recently, indirect data on individual vari-ability of TH-responsiveness in the large African barbLabeobarbus intermedius were reported. They demon-strated that juveniles of this fish differently respondedto similar doses of exogenous THs under experimentalconditions [3, 4]. Taking into account an important roleof TH-responsiveness in the ontogeny control, we stud-ied individual variability of TH-responsiveness and itsinvolvement in intraspecific morphological diversifica-tion in fishes.We compared morphological changes inL. intermedius siblings grown at a high level of exoge-nous TH. We focused our attention on the serial struc-tures that usually decrease in number when theL. intermedius siblings are growing under a high THlevel [3, 4].The eggs were obtained from the crossing ofL. intermedius spawners taken from a Lake Tana tribu-tary, the Gumara River (Ethiopia) and divided into twogroups. The first experimental group was put into amedium with a high TH content, namely, 2 × 10

On inheritance of the number of pharyngeal tooth rows in a large African barb Barbus intermedius

The number of pharyngeal tooth rows is an impor-tant taxonomic feature of cyprinid fishes (Cyprinidae)(Howes, 1991), which is used to elucidate the phyloge-netic links between single species and higher rank taxa(Heincke, 1892; Regan, 1911; Berg, 1912; Vladykov,1934; Chu, 1935; Vasnetsov, 1939; Nikol’skii, 1950;Fink and Fink, 1981; Nakajima, 1987; Cavender andCoburn, 1992; Golubtsov et al., 2005). Usually, thereare one to three rows of pharyngeal teeth in the cyprinidfishes (Nikolsky, 1950; Sibbing, 1991). In the majorityof cases, the number of pharyngeal tooth rows is thesame in all individuals of one species; however, it variesin some cyprinid species. Thus, decrease of the numberof pharyngeal tooth rows was noted in carp Cyprinuscarpio developing at high temperature (Tatarko, 1968).In addition, a decrease in the number of pharyngealtooth rows was also observed in single genotypes of C.carpio during studies on the inheritance of quantitativefeatures (Kirpichnikov, 1979).An increase in the number of pharyngeal tooth rowsfrom only one side was noted in such species as Clinos-tomus elongatus, Semotilus atromaculatus, C. carpio,and Notropis hudsonis. Abnormalities during develop-ment and tooth replacement (Evans and Deubler, 1955;Eastman and Underhill, 1973) were considered themost possible cause for this phenomenon. Cases whenthe fourth row of pharyngeal teeth appears on bothsides could hardly be considered the consequence ofabnormalities in tooth replacement. At least two speciesfrom the Schizotorax genus are known to have popula-tions with fish possessing both three and four rows ofpharyngeal teeth (Terashima, 1984; Mirza, 1991). Thepresence of four rows of pharyngeal teeth is noted insmall African barb Barbus paludinosus (Golubtsovet al., 2005). There have been a few finds of individualswith four rows of pharyngeal teeth in the populations ofEuropean barbs: B. barbus (Bodareu and Karlov,1984), B. lacerta, and B. mursa (Elanidze, 1983); anindividual with the following pharyngeal teeth formula1.1.2.3.5–5.3.2.1 was found in one of the populations ofa large African barb B. altianalis (Banister, 1973). Allindividuals from a recently found cyprinid species Ras-trineobola argentea have four rows of pharyngeal teeth(Anhelt et al., 2006).Although, some authors regard the operation ofancestral genes as the main reason for the appearance ofan additional fourth row of pharyngeal teeth, relying onthe examples provided above (Golubtsov et al., 2005;Anhelt et al., 2006), there have been no data on theinheritance of this state of the studied feature.Data on the state of the feature “number of pharyn-geal tooth rows” in the offspring of a large African barbB. intermedius obtained from spawners with three rowsof pharyngeal teeth, which is normal for this species,and from spawners with four rows of pharyngeal teethare given below.MATERIAL AND METHODSOne of the morphotypes of polymorphic large Afri-can barb B. intermedius from Lake Tana, Ethiopia,namely the “bigmouth small-eye” sensu Nagelkerke etal. (1995) (Fig. 1) served as the object of studies. A totalof 14 morphotypes of this species were found in thelake (Nagelkerke et al., 1994, 1995), being described asa separate species later (Nagelkerke and Sibbing,1997). A number of researchers put the validity of some(may be majority) described species under question(Mina et al., 2001; Zvorykin et al., 2006; Dzerzhinskiiet al., 2007). In this article we use the classification ofmorphotypes proposed by Nagelkerke (Nagelkerke etal., 1994, 1995). All morphotypes of large barbs fromLake Tana, as well as the majority of fish belonging tothe Barbinae subfamily, have the following pharyngealteeth formula 2.3.5–5.3.2 (Banister, 1973; our data).Experimental hybridizations of bigmouth small-eyemorphotype fish were performed in October 2005, in

Spawning of large Barbus (Barbus intermedins Complex) in a small river of the Lake Tana basin (Ethiopia) and relationships of some putative species

Direct observations on three forms (morph types) of spawning barbs, considered by some authors as different species, were carried out in September–October 2005 at the Gumara River and its small tributary, the Ducalit, in the Lake Tana basin. The spawning barbs were sampled using cast nets. Barbs of different morphotypes composed common spawning aggregations and were caught together. It is likely that troutlike females mate extensively with intermedius males and, probably, with bigmouth small-eye males. Experiments in artificial fertilization and rearing showed that, during the embryonic period, there was no increase in mortality of progeny from crosses of barbs of different morphotypes, in comparison with homonomic crosses, thus suggesting an absence of postzygotic reproductive isolation between the morphotypes. At the same time, mortality of progeny from crossing barbs with Varicorhinus beso Ruppell, 1836 was very high during the earliest stages of development, suggesting strong, even if incomplete, reproductive isolation ensured by postzygotic mechanisms.

Major histocompatibility genes in the Lake Tana African large barb species flock: evidence for complete partitioning of class II B, but not class I, genes among different species

Major histocompatibility genes in the Lake Tana African large barb species flock: evidence for complete partitioning of class II B, but not class I, genes among different species

Major histocompatibility genes in the Lake Tana African large barb species flock: evidence for complete partitioning of class II B, but not class I, genes among different species

The 16 African 'large' barb fish species of Lake Tana inhabit different ecological niches, exploit different food webs and have different temporal and spatial spawning patterns within the lake. This unique fish species flock is thought to be the result of adaptive radiation within the past 5 million years. Previous analyses of major histocompatibility class II B exon 2 sequences in four Lake Tana African large barb species revealed that these sequences are indeed under selection. No sharing of class II B alleles was observed among the four Lake Tana African large barb species. In this study we analysed the class II B exon 2 sequences of seven additional Lake Tana African large barb species and African large barbs from the Blue Nile and its tributaries. In addition, the presence and variability of major histocompatibility complex class I UA exon 3 sequences in six Lake Tana and Blue Nile African large barb species was analysed. Phylogenetic lineages are maintained by purifying or neutral selection on non-peptide binding regions. Class II B intron 1 and exon 2 sequences were not shared among the different Lake Tana African large barb species or with the riverine barb species. In contrast, identical class I UA exon 3 sequences were found both in the lacustrine and riverine barb species. Our analyses demonstrate complete partitioning of class II B alleles among Lake Tana African large barb species. In contrast, class I alleles remain for the large part shared among species. These different modes of evolution probably reflect the unlinked nature of major histocompatibility genes in teleost fishes.

Threatened Fishes of the World: Barbus ethiopicus Zolezzi, 1939 (Cyprinidae)

Presence of this species in the other significant tributary of Lake Zwai, the Katar River, has not been verified. Habitat and ecology: Large individuals (>220mm SL) were found in the lake, while small ones (<220mm SL, both juvenile and mature) were found in the Meki River. This suggests an annual cycle of feeding in the lake and breeding in its tributaries during the rainy season (June‐November), a pattern similar to other species of large African barbs (Dgebuadze et al. 1999). The presence of mature fish up to 210mm SL in the river during the dry season (in January‐March)suggeststhepresenceofindependentriverineandlacustrinepopulations.Reproduction:Presenceofjuveniles(21‐35.5mmSL inFebruaryand38‐43mmSLinMarch),apparentlyyoungerthan1year,intheupperreachesoftheMekiRiverduringthedryseasonisevidence of spawning at the end of the previous rainy season. Ripe running males (minimum 156mm SL) at this locality were recorded also in January and February. Threats: The Lake Zwai basin is a region of intensive human population growth, agricultural, and urban development. The main threat to B. ethiopicus is the degradation of water quality and availability due to human pollution and exploitation. Additional potential threats are overfishing and competition with exoticfish species introduced into the basin (Golubtsov et al. 2002). BecauseB. ethiopicusis coincidentally caught with the more abundant B. intermedius by commercial fishermen, continued exploitation of B. intermedius could cause extermination of B. ethiopicus from Lake Zwai. At least one species of exotic fish (the Far East crusian carp) introduced into the basin may compete for food with B. ethiopicus in the lower reaches of the system. Conservation recommendations: A search for populations of B. ethiopicus and its spawning grounds in the two main tributaries of Lake Zwai is urgently needed. Spawning grounds should be demarcated and legally protected. The barb fisheries in the lake needs to be immediately regulated and restricted during the period of barb breeding migrations. The possibility of artificial propagation of B. ethiopicus should be studied. Remarks: B. ethiopicus is most likely a unique representative of phylogenetic lineage quite distantly related to other Ethiopian large barbs as demonstrated by recent molecular data (Dimmick, unpubl.).

Riverine spawning and reproductive segregation in a lacustrine cyprinid species flock, facilitated by homing?

Abstract This paper aims at assessing the reproductive segregation within the endemic Barbus (renamed Labeobarbus) species flock of Lake Tana (Ethiopia). Migration, followed by temporal and spatial reproductive segregation in the upstream tributaries of two inflowing rivers was studied systematically over the 1999 and 2000 spawning seasons. Physical events that may trigger lacustrine migration and characterise suitability of spawning grounds were analysed. Six species migrate 30-40 km upstream Gumara River during declining flow, just after the rainy season. Spawning occurs in the well-oxygenated gravel beds of four Gumara tributaries. Eight 'large barb' species were absent from the rivers, or found only incidentally, thus segregating them at a macro-spatial scale from the six river-spawners. The missing species spawn either in the lake or in other rivers not sampled. Long distance migration and species-specific spawning sites suggest that homing may have facilitated reproductive isolation and speciation. A fine-tuning between homing and gonad development is suggested since females reach spawning maturity only as they arrive at the spawning grounds. This study provides convincing evidence for reproductive segregation, and contributes in unravelling the evolution of this unique Labeobarbus species flock. Collective migration and riverine spawning of six Labeobarbus species makes them very vulnerable for overfishing at the spawning areas.

Ecological position of ‘small barbs’ and their potential for fisheries: An option to reduce fishing pressure on ‘large barbs’ of Lake Tana (Ethiopia)?

The two barbs, Barbus humilis and Barbus tanapelagius are important pelagic fish in Lake Tana. These ‘small barb’ species (&amp;lt;10 cm fork length) play a key role in the Lake's ecosystem as a link between zooplankton and the top predators, mostly ‘large barbs’. This paper presents an overview on the position of ‘small barbs’ in the food web of Lake Tana as indicated from gut content analysis. Barbus tanapelagius, the most abundant and specialized species, exploited zooplankton. Barbus humilis mostly fed on detritus and zooplankton. Barbus tanapelagius, and to some extent the benthopelagic Barbus humilis, transferred energy from zooplankton to the top level of the food web. Barbus humilis is a vector of energy and biomass from detritus to top predators. Pelagic fisheries are proposed as an option to reduce fishing pressure on the endemic species flock of ‘large barbs’. If, however, a fishery on the ‘small barbs’ is proposed to increase the sustainable yield, implications on the ecosystem balance should be critically assessed. Regulations should be recommended for these fisheries (gear, habitats and season) accounting for the biological constraints.

Length at maturity and gillnet selectivity of Lake Tana's Barbus species (Ethiopia): Implications for management and conservation

Lake Tana's 15 large Barbus species form the only known intact endemic cyprinid species flock left in the world. The barbs contribute around one third of the total annual catch of the motorised commercial gillnet fishery which was introduced in 1986. A dramatic reduction of the adult Barbus stocks and the even lower proportion of recruits at the end of the 1990s, show the necessity for the development, implementation and control of fisheries legislation in Lake Tana. The reproductive biology of the Barbus species, essential for fishery management, is poorly known. This paper presents results on size at maturity, size at harvest and gillnet selectivity curves, which can be used to provide a scientific base for management proposals. Size at maturity varied widely among the Barbus species, ranging from 18.8 cm in Barbus brevicephalus to 44.3 cm in Barbus crassibarbis. Males matured at smaller size and reached smaller maximum length than females. Estimated selectivity curves fitted closely or were slightly larger than the observed length-frequency distribution of the commercial catch. The vast majority (85%) of barbs landed by the commercial gillnet fishery were mature. Fishing pressure on juvenile, immature fish is unlikely to be the cause of the observed decrease in Barbus stocks. Size control regulations like mesh size restrictions, intended to protect the immature part of fish populations are expected to have little positive effects on the Barbus stocks and are therefore not recommended. The drastic reduction in barbs during the 1990s is most like due to recruitment overfishing, that is, poorly regulated high fishing effort by the commercial gillnet fishery on the spawning aggregations of adult barbs during their annual breeding migration in river mouths and surrounding floodplains. Only effort control regulations limiting the gillnet fishery in the spawning season and/or areas will prevent a total collapse of the Barbus stocks as has happened to other cyprinids in African lakes. Such measures have to be implemented urgently to guarantee the conservation of Lake Tana's unique biodiversity as a sustainable source of cheap protein and as a natural laboratory to study the evolutionary processes underlying speciation in freshwater fish.

Revision of the ant genus Streblognathus (Hymenoptera: Formicidae: Ponerinae)

The southern African ant genus Streblognathus has long been regarded as being monotypic but a morphological reappraisal of available specimens shows that there are two species: Streblognathus aethiopicus (F. Smith), which occurs in the southern karoo of the Eastern Cape, and Streblognathus peetersi sp. nov., which occurs in the eastern grasslands of southern Africa. Workers and males are described and keyed. Male genitalia are illustrated and the significance of the large barbs on the penis valves is discussed.

Genetic Comparison of Three Barbus (Cyprinidae) Morphotypes from the Genale River, Ethiopia

Abstract The large barbs of East Africa are well known for their morphological plasticity. Mitochondrial DNA sequences were compared for specimens of three distinctive barb morphotypes collected syntopically from the Genale River in southeastern Ethiopia. The “normal,” “lipped,” and “large-mouthed” morphotypes are putatively referable to Barbus gananensis. An analysis of molecular variance revealed that the lipped and normal morphotypes are not genetically distinct (ϕST < 0.0001, P = 0.80) and that the group of large-mouthed haplotypes is significantly differentiated from a combined group of normal and lipped haplotypes (ϕST = 0.54, P < 0.001). The evolutionary relationships among the haplotypes were assessed with phylogenetic and minimum-length spanning trees. The results of the phylogenetic and spanning tree analyses are consistent with the analysis of molecular variance. The normal and lipped morphotypes represent morphological variants of B. gananensis, and the large-mouthed morphotype represents a ge...

Consequences and Modes of Morphological Diversification of East African and Eurasian Barbins (genera Barbus, Varicorhinus and Capoeta) with Particular Reference to Barbus Intermedius Complex

Based on results of the comparison of skull proportions and using available data on phylogeny of barbins we discuss patterns of morphological diversity of the present forms and modes of morphological transformations resulting in their emergence. There is no strict correspondence between distance in a character space and genealogical closeness of forms. Similar forms of barbins independently originated from a generalized form in different sites of Africa and western Asia. Regularity of patterns of morphological diversity is thought to be caused by the ‘channeling’ of morphological transformations. Heterochrony played an important part in evolution of the African ‘large Barbus’ and Varicorhinus. Extraordinary morphological diversity of the African barbins, Lake Tana barbs in particular, is caused mainly by drastic changes in patterns of relative growth late in ontogeny.

Barbus tanapelagius, A New Species from Lake Tana (Ethiopia): its Morphology and Ecology

The endemic cyprinid species flock in Lake Tana consists of 15 species of large hexaploid barbs, eight of which are piscivorous. Previously, it was assumed that all piscivores preyed on the same small barb species, Barbus trispilopleura. In this paper we present a description of morphology and ecology of a new abundant small barb species, Barbus tanapelagius sp. nova (holotype RMNH 33731) from Lake Tana, Ethiopia, which appears to be the major prey species for the large pelagic piscivorous barbs. B. tanapelagius differs clearly in morphology from the other 3 small, diploid Barbus species known from Lake Tana, B. trispilopleura Boulenger, 1902, B. humilis Boulenger, 1902 and B. pleurogramma Boulenger, 1902. Conspicuous differences are its elongated body, large eye diameter, prominent and hooked lower jaw contour and colouration. Preliminary data suggest that B. tanapelagius also differs ecologically from the other small Barbus spp. by its pelagic, strictly zooplanktivorous feeding and its occurrence mainly in the deeper, offshore waters. The other small Barbus species are most probably largely benthic feeders and dominant in the shallow inshore waters. Previous views about the evolution of the present 8 endemic piscivorous large barb species therefore require reconsideration, as the present paper shows a more complex scenario including several prey species.

The Piscivorous Barbs of Lake Tana (Ethiopia): Major Questions On Their Evolution and Exploitation

This paper surveys some major questions on the evolution of eight piscivorous Barbus species (B. acutirostris, B. dainellii, B. gorguari, B. longissimus, B. megastoma, B. platydorsus, B. truttiformis, and B. macrophtalmus), which together with six other species compose the endemic hexaploid 'large barb' species flock of Lake Tana. Preliminary data suggest that the major prey species of these piscivores (up to 90 cm length), in contrast to previous reports, is not Barbus trispilopleura, but at least two other diploid 'small barb' species (10 < cm). Data are collected from 1) the resource partitioning of the piscivores in the field, 2) aquarium experiments on the predator success in catching different prey species and size classes, 3) analyses on allometric growth and diet shifts in the field and 4) molecular genetic data, which will be combined to construct a hypothesis on the process of the evolution of these piscivorous barbs. Being the major target of commercial fisheries, knowledge on these piscivorous fish stocks and their prey species is required for aiming at sustainable fisheries. Preliminary data show a serious decline of fish stocks, most probably largely due to overexploiting their spawning grounds.

The Large Barbs (Barbus Spp., Cyprinidae, Teleostei) of Lake Tana (Ethiopia), With a Description of a New Species, Barbus Osseensis

Recently the complex of 'large', hexaploid barbs (genus Barbus) of Lake Tana, Ethiopia, was revised as 14 species (NAGELKERKE & SIBBING, 1997), seven of which were new. This paper describes another new species, Barbus osseensis and summarises the major features of the former new species (B. crassibarbis, B. megastoma, B. longissimus, B. tsanensis, B. brevicephalus, B. truttiformis, and B. platydorsus). Figures of all fifteen large barb species of Lake Tana are presented, and an identification key for specimens larger than 15 cm standard length is provided. The position of the large hexaploid barbs within the genus Barbus is discussed.

Venom induces alarm behaviour in the social wasp Polybioides raphigastra (Hymenoptera: Vespidae): an investigation of alarm behaviour, venom volatiles and sting autotomy

SummaryChemicals from the venom gland elicited alarm behaviour and attack in the Asian polistine wasp Polybioides raphigastra. When presented with crushed venom glands workers of this wasp respond with a mass stinging attack. Gas chromatography–mass spectrometry analyses show that the major volatiles in the venom gland are alkanes, monounsaturated alkenes and 2‐alcohols. Several pyrazines, a spiroacetal and aromatics were also identified as trace compounds. The anatomy and morphology of the sting apparatus are reported, and we describe sting autotomy in this wasp. This is the first such report for the Ropalidiinae. The structures responsible for autotomy are likely to be large barbs present on the sting lancets, and a conspicuous tooth present on the medial side of the left lancet. Sting autotomy in P. raphigastra probably plays an important role in the localization of sites of attack by wasps defending the nest.

Seasonal changes in fish community structure of intermittent streams in the middle reaches of the Guadiana basin, Portugal

Seven sites on three tributaries with intermittent flow regimes in the middle reaches of the Guadiana, i.e. Xévora, Caia and Degebe, were sampled approximately every 3 months from April 1995 to April 1997. The density and biomass of fish were greater in downstream rivers and sites. Along the Xévora River, a series of point abundance samples showed evidence of fish zonation along the river. Canonical correspondence analysis (CCA) suggested a simple relationship between the different species and their preferred habitat. The small‐sized Rutilus alburnoides and Leuciscus pyrenaicus used most or all of the habitats with some cover and flowing water. Greater concentrations of larger fish were found in downstream reaches which generally had greater depths as stream width increased: large Barbus microcephalus, B. steindachneri and B. comiza preferred such sites on the Degebe River. Droughts in seasonal Mediterranean streams such as the Guadiana River are a predictable natural disturbance. In the summer, flow ceases and some stretches of river consist of isolated pools. This results in intense aggregations of fish and possible competition for food and/or space. Although some species are well adapted to natural droughts, habitat degradation and possibly the introduction of exotic species contribute to marked variability in species composition.