Large Barbs Research Articles

II ‐ Morphological diversity of “large barbs”; from Lake Tana and neighbouring areas: Homoplasies or synapomorphies?

In the Lake Tana barbs the PCA of skull measurements reveals “ontogenetic channels”; within which individual ontogenetic trajectories are located. Some individuals seem to acquire states of characters specific for a certain morphotype quite late when they are 20–25 cm SL and 3–5 years old. Morphologically different sympatric forms of large barbs are also found in the Didessa (Blue Nile basin), Genale (Wabi Shebeli basin), and Gibe (Omo basin) rivers. In all the three rivers barbs resembling certain morpho‐types of the Lake Tana barbs occur. Most probably, allopatric big‐mouthed forms originated independently from sympatric forms which have no conspicuous specific traits and that their similarity results from homoplasies.

Speciation of endemic Lake Tana barbs (Cyprinidae, Ethiopia) driven by trophic resource partitioning; a molecular and ecomorphological approach

A unique species flock of large barbs (Barbus spp.) from Lake Tana is presented, from the level of fish stocks to molecules. Evidence is given for the species status of 14 morphotypes of large barbs. They distinctly differ in: (1) head and body morphometrics, (2) food preferences, (3) distribution patterns, (4) maximal body size, (5) spawning area and period, and (6) molecular genetic characters. Most types show early morphological divergence at small size. Major Histocompatibility Complex (MHC) genes, encoding cell membrane proteins involved in defence against pathogens, were found to be diagnostic for the species' genetic identity. A strong selective pressure on particular amino acid positions in the MHC protein sequence most probably arose in response to different pathogen loads from the newly invaded ecological niches after formation of Lake Tana, ca. two million years ago.

Reproductive segregation among the Barbus intermedius complex of Lake Tana, Ethiopia. An example of intralacustrine speciation?

Reproductive segregation among the large barbs Barbus intermedius complex, Cyprinidae, of Lake Tana, Ethiopia, was investigated in the mouths and upstream reaches of rivers tributary to the lake, during the spawning seasons of 1993 and 1994. The percentage of running fish of four Barbus morphotypes [Acute (Ac), Bigmouth big‐eye (Be), Intermedius (In), and Shorthead (Sh)] peaks with the highest water level of the lake. Large differences are apparent in the minimum fork length of running fish among morphotypes [c. 12 cm for male Sh and 28 cm for male Bigmouth small‐eye (Se)]. Significant differences occur in temporal, but especially in spatial patterns of the relative abundance of running morphotypes, when the lake is compared with the four major river mouths and their upstream reaches. These different relative abundances are clearest among Ac, Be, In, Sh and Troutlike (Tr). Also, the absence from the rivers of some morphotypes that are usually abundant in the lake itself [Barbel (Ba), Dark (Da), Lip (Li), and Zurki (Zu)], and the abundant presence in the rivers of Tr, rare in the lake, strengthen the hypothesis that spatial and/or temporal spawning segregation is present among the morphotypes. There are indications that Bighead (Bh) and Zu spawn in the lake itself, while other morphotypes were only found running in or near rivers. Combined with the morphological, ecological, and genetic differences, these data suggest the existence of several Barbus species, forming a unique species flock, which probably evolved within the lake. The presence of several, instead of one Barbus species complicates management of sustainable fisheries and protection of the lake's biodiversity. Present results show the importance of the rivers for Barbus reproduction and stress the urgent need for careful management of fishing activities in spawning times and areas.

Survey of the variation in alar and malar thorns in skates: Phylogenetic implications (Chondrichthyes: Rajoidei).

A total of 62 species, representing 24 of the 28 supraspecific taxa of skates, was surveyed for the presence, distribution, and structure of alar and malar thorns. The survey revealed that alar thorns are almost universally present in mature male skates, and that malar thorns are of two types that may have separate origins. The location and orientation of alar thorns differed in two major clades of skates (groups I and II). They were either exposed on the disc with the crown oriented obliquely to the long axis of the base or imbedded in slits in the integument and oriented parallel to the long axis of the base. Group I possessed the former type of thorns and, with several exceptions, group II possessed the latter type. Group I either lacked malar thorns or possessed malar thorns that were most likely derived from generalized placoid scales. Group II possessed, with several exceptions, malar thorns derived from enlarged placoid scales. Within group I the supraspecific taxa Atlantoraja and Rioraja possessed unique alar thorns that were reclined laterally and associated with lateral grooves in the integument. Within group II the supraspecific taxa Anacanthobatis, Cruriraja, Dipturus, Okamejei, Raja, the North Pacific Assemblage, and the Amphi-American Assemblage had a large barb on the distal section of the crown of the alar thorn that suggests that these taxa form a clade. The crown of the alar thorns of the latter five supraspecific taxa was undulatory, thus supporting their monophyletic status. Another assemblage within group II had ridges that ran most of the length of the crown of the alar thorns corroborating their monophyletic status. The survey also suggested that variation of integumentary grooves associated with the alar thorns in Bathyraja, and presence or absence of malar thorns in Psammobatis, may be phylogenetically informative. © 1996 Wiley-Liss, Inc.

Lake Tana large barbs: phenetics, growth and diversification

Lake Tana large barbs: phenetics, growth and diversification

Lake Tana large barbs: phenetics, growth and diversification

Among the Lake Tana large barbs of about 10 cm SL only representatives of the‘ acute’morphotype can be distinguished, in the size range 10–20 cm SL‘ bigmouth big eye’ can be identified also. As for the rest, very few individuals can be confidently affiliated with a particular morphotype most of them looking like‘ intermedius’. Even within the range of 20–30 cm SL some individuals are still difficult to identify. Principal component analysis of cranial characters revealed discrete groups of morphotypes. Differences in both external and cranial characters of the morphotypes result from divergence which is most pronounced when fish are 4–5 years old and 20–25 cm SL. This divergence cannot be related exclusively with differences in the growth rates of individuals representing different morphotypes. Differences in food composition between the morphotypes probably increase in parallel with their morphological divergence. Differences between the morphotypes in the lateral line (11) and the gill rakers (Sb) counts were revealed using ANOVA. Comparison of the Lake Tana Barbus complex of forms with that previously known from Lake Lanao (Philippines) suggests that in both lakes the different forms arose sympatrically but that sympatric speciation in Lake Lanao has advanced further than in Lake Tana.

Ecomorphology as a tool in fisheries: identification and ecotyping of Lake Tana barbs (Barbus intermedius complex), Ethiopia

Fisheries development of Lake Tana, Ethiopia, urgently requires the identification of its unknown units of fish stock. A diversity of large barbs (up to 80 cm SL), lumped into one species Barbus intermedius and contributing over 35% of the annual catch, consists of at least thirteen distinct morphotypes (Nagelkerke et al., 1994), possibly species. Their abilities and limitations in food selection and feeding can be predicted from structural specializations following functional morphological methods. Using ecomorphology, a spectrum of ecotypes ranging from detritivores to piscivores is predicted. Such hypotheses may be tested by analysing these fishes' intestinal contents. From knowledge of available food organisms and the trophic segregation thus found among barbs and sympatric species, a preliminary food web has been constructed. This food web, together with quantitative studies on population dynamics and energy flow, provides a biological framework for rational fisheries management aiming at sustainable production and protection of biodiversity.

The barbs (Barbus spp.) of Lake Tana: a forgotten species flock?

In October–December 1990, the large barbs (Barbus) that contribute more than 35% of the catch in lake Tana (northern Ethiopia) were studied. Previous authors (Ruppell 1837, Boulenger 1902,1911, Bini 1940) described from 6 to 23 (sub)species for the lake. Banister (1973) lumped all of these into one subspecies: Barbus intermedius intermedius Ruppell,1837. We found that the Lake Tana Barbus could be readily categorized in at least 13 discrete morphotypes, some of which were already distinguished by local fishermen. None of the known descriptions are adequate to distinguish the barbs unambiguously, which is important for monitoring and management of developing fisheries. Intermediates between morphotypes were rare (< 10%). By applying canonical discriminant analysis on a set of 17 morphometric characters (including some directly associated with feeding) our initial morphotype-distinction was confirmed. Also, differences between the morphotypes in distribution, related to depth and substratum were found, as well as differences in intestinal contents, a key to the food-niche. The high number of piscivorous morphotypes (8 out of 13) was striking as piscivory is relatively rare among cyprinids. Piscivory was found to be highly correlated with morphological (feeding related) characters. The presence of discrete morphotypes, that also differ in food-niche and distribution, strongly suggests that several distinct populations exist, that may be (partly or completely) reproductively segregated. Knowledge about these populations, that may represent separate units of fish stock, is of crucial importance for the management of sustainable fisheries and protection of the biodiversity in Lake Tana. It is possible that several species or even a unique cyprinid species flock are present, that urgently need protection.

Morphological Divergence During Growth in the Large Barbs (Barbus Spp.) of Lake Tana, Ethiopia

Recently the large Lake Tana barbs (genus Barbus) were categorized into at least 13 distinct morphotypes based on large differences in general morphology, distribution and feeding habits. They are probably different populations and may even constitute a unique cyprinid species flock. This study demonstrates that 11 of the 14 morphotypes (as an additional morphotype 'Shorthead' is identified in this paper) can already be distinguished by their general external features at fork lengths of less than 12 cm. These distinctions were verified by statistical analysis of morphometric data. The distinction of the morphotypes in small specimens supports the hypothesis that several distinct Barbus species exist in Lake Tana. Knowledge of the population structure and species composition is very important for the reconstruction of the evolutionary history and mechanisms of this unique fish community. Moreover, in order to protect the biodiversity of the lake, it is important that the fisheries in the lake only increase on a sustainable basis and a detailed knowledge of the fish community structure is vital to achieve this goal.

Karyological study of some cyprinid species from Ethiopia. The ploidy differences between large and small Barbus of Africa

Chromosome sets of nine species of Barbus and a species of Varicorhinus from Ethiopia were investigated. All large Barbus (B. bynni, B. intermedius, B. ethiopicus) and V. beso are shown to have 2N =150, whereas all small Barbus (B. anema, B. kerstenii, B. paludinosus, and three unidentified (probably undescribed) species have 2N = 50. Based on the karyological data and on the published morphological data, an independent origin of small and large Barbus of Africa is suggested. The authors believe that large Barbus of Africa constitute a monophyletic group and that this group has no sister‐group relationships with any of the small Barbus of Africa.

Karyological study of some cyprinid species from Ethiopia. The ploidy differences between large and small Barbus of Africa

Chromosome sets of nine species of Barbus and a species of Varicorhinus from Ethiopia were investigated. All large Barbus (B. bynni, B. intermedius, B. ethiopicus) and V. beso are shown to have 2N =150, whereas all small Barbus (B. anema, B. kerstenii, B. paludinosus, and three unidentified (probably undescribed) species have 2N = 50. Based on the karyological data and on the published morphological data, an independent origin of small and large Barbus of Africa is suggested. The authors believe that large Barbus of Africa constitute a monophyletic group and that this group has no sister-group relationships with any of the small Barbus of Africa.

The structure and function of the genitalia in the Libellulidae (Odonata)

An outline of the morphology of the secondary genitalia of libellulid dragonflies is given together with a more detailed treatment of the components of the fourth (distal) segment of the penis. The variations of penis structure in 70 species, representing ten of the 11 subfamilies, are surveyed and catalogued. There is remarkable diversity in the presence and form of penis structures, particularly those associated with the medial process, namely the flagelium, cornua and inner lobes. A comparable survey of females shows that they can be provisionally divided into ten types according to the number and size of their sperm-storage organs. Comparisons of penis structures with the sperm-storage organs of females suggests that in species whose females store large amounts of sperm, usually doing so in one or a pair of organs, males possess highly extensible, lobate and bristly penes, commonly equipped with cornua. By contrast, in those species in which the females store small volumes of sperm, usually doing so in three organs, the penes bear either flagella equipped with proximally directed spines or with large terminal barbs, or they have narrow, spiny inner-lobes which resemble flagella. Some functional interpretations are proposed in the light of sperm competition. The variability of genital structure can be interpreted adaptively and does not closely reflect phylogenetic relationships. Functionally convergent structures have evolved a number of times from different origins.

Two new species of large Barbus (Pisces, Cyprinidae) from central Africa

Two new species of large Barbus (Pisces, Cyprinidae) from central Africa

A revision of the large Barbus (Pisces, Cyprinidae) of east and central Africa. Studies on African Cyprinidae. Part 2

A revision of the large Barbus (Pisces, Cyprinidae) of east and central Africa. Studies on African Cyprinidae. Part 2