Morphometric and genetic characterization of sympatric populations of Clarias gariepinus and C. anguillaris from Senegal

A sample of African Clarias catfishes from the Senegal River was studied using morphometry, allozyme variation, microsatellites and RFLPs of mitochondrial DNA. They all confirmed the presence of two species , C. gariepinus and C. anguillaris . The two species were closely related genetically and no diagnostic loci were found in allozymes and microsatellites studies. Two of the 11 haplotypes of mtDNA observed were shared by both species. Three of the four assays (morphometry, allozymes and microsatellites) allowed a precise characterization of both. One specimen occupied an intermediate position in the analysis of the data; it was considered an F_l hybrid whose possible origin is discussed.     

Enzymatic variation in African clariid catfishes

Enzymatic polymorphism was examined at 13 protein loci in four African clariid catfish species: Clarias anguillaris (Linnaeus, 1758), C. ebriensis Pellegrin, 1920, C. gariepinus (Burchell, 1822) and Heterobranchus longifilis Valenciennes, 1840. The latter appears to be closer to C. anguillaris and C. gariepinus than C. ebriensis . These results correspond with recently published karyological and morphometrical data.
Reproductive compatibility, under laboratory conditions at least, is demonstrated between C. gariepinus and H. longifilis . The hybrids were shown to be completely intermediate between the parental strains.     

Associations of allozyme variation and behavior in the cowpea weevil (Callosobruchus maculatus)

The cowpea weevil (Callosobruchus maculatus (Fabré)) exhibits several behavioral traits that are stable within, but vary among, strains. These traits are heritable and quantitative. We used cellulose acetate gel electrophoresis to quantify allozyme variation within and among laboratory cultures of four weevil strains and determine whether allozyme variation correlates with behavioral traits. Significant variation exists at 8 of 11 loci assayed and gene frequencies are significantly different among strains. The South Indian strain (SI) is most variable and measures of genetic distance set it apart from the other strains. It is also behaviorally unique. The Brazilian strain (BC) is most different from SI in allozyme diversity and behavioral phenotype, while two African strains (IITA, CAM) are intermediate in allozyme diversity and phenotype. These results are consistent with the known history of these strains and the differences in the allozymes parallel the differences in behavioral traits.     

Patterns of allozyme variation in Nordic Pilosella

Patterns of allozyme variation have been investigated in 101 clones representing most of the morphological variation (and taxa) found in the amphi-apomictic genus Pilosella Hill. in the Nordic countries. Levels of variation were very high, both within narrowly defined taxa and within the whole data-set, but the correlation between a morphology-based taxonomy and patterns of allozyme variation was very weak. Almost all enzyme bands were found in more than one taxon and the differences between broadly defined species in terms of the frequency of bands were generally small. Cluster analyses did not perfectly recover any taxon but there were some tendencies for samples of some broadly defined taxa (e.g. P. officinarum s. l., and P. cymosa ssp. cymosa) to cluster together. It is concluded that there is considerable gene-flow among virtually all Nordic morpho-types of Pilosella and this is considered an argument for applying a very broad species concept in this genus.Financial support for the present study has been recieved from Stiftelsen Harald E. Johanssons minnesfond at the Royal Swedish Academy of Sciences.     

Evolutionary genetics of Metridium senile. II. Geographic patterns of allozyme variation

Electrophoretic surveys have demonstrated that populations of the sea anemone Metridium senile along the northeast coast of the United States are polymorphic at four enzyme loci. Phosphoglucose isomerase (PGI) has two alleles in most populations, phosphoglucomutase (PGM) has three alleles, and two leucine aminopeptidase loci have two common alleles each. Phosphoglucose isomerase displays clinal variation and an apparent association with environmental temperature. Phosphoglucomutase shows clinal variation north of Cape Cod for two of the three alleles, while the two leucine aminopeptidase loci are not clinal. All loci show a great deal of variation in populations on Cape Cod, but there is no apparent systematic pattern to this variation. Temperature may be a selective agent in the maintenance of the PGI and PGM clines, although other possibilities cannot presently be completely excluded.Supported by Grant T-4 from the Health Research and Services Foundation, NSF DEB77-14442, NIH GM25809, and NIH GM28024.     

Healing of skin wounds in the African catfish Clarias gariepinus

The African catfish Clarias gariepinus was used as a model for wound healing and tissue regeneration in a scale-less fish. A temporal framework of histological and cell proliferation markers was established after wound induction in the dorsolateral cranial region, by removing the epidermal and dermal layers, including stratum adiposum (SA). Wound closure and epidermis formation was initiated within 3 h post-procedure (hpp) with migration and concomitant proliferation of epidermal cells from the wound borders. The wound was covered by this primary epidermal front 12 hpp and fusion of the opposing epidermal fronts occurred within 24 hpp. Attachment of the newly formed epidermal layer to the underlying dermis was observed 48 hpp concomitant with a second wave of cell proliferation at the wound edge. Normal epidermal thickness within the wound was achieved 72 hpp. Formation of a basement membrane occurred by 120 hpp with concomitant emergence of the SA from the wound borders. Wound healing in C. gariepinus skin involved closure of the wound and re-epithelization through cell migration with a single wave of early cell proliferation not documented in other species. Furthermore, covering of the wound by epithelium as well as the reappearance of the basement membrane and SA occurred sooner than in other fish species.     

Morphometric and advertisement call geographic variation in polyploid green toads

We describe the spatial pattern of variation of morphometric characters and call acoustic properties of tetraploid green toads [Bufo viridis complex) from eight populations in Central Asia, and we analyse the causal agents responsible for the patterns observed, by means of partial Mantel tests. Populations significantly differ with respect to both body size and body shape. Since animals inhabiting the driest regions are smaller, but not younger, man animals from less dry areas, we suggest that their small body size is due to the limiting effect of arid climate on growth rate. Differences in body shape are positively associated only with geographic distances, and we suggest that isolation by distance might have played an important role in determining the pattern of variation. Populations significantly differ also with respect to the acoustic properties of the call, in particular, with respect to temperature-adjusted pulse rate and body size-adjusted fundamental frequency; that is, with respect to those properties which are under the strongest morphological or physiological constraints, and that show the lowest variability within individuals (static properties). The pattern of variation of calls shows positive association with geographic distances, but not with climatic distances. Calls do vary, and in this region the main causal agent responsible for call variation might have been the isolation by distance. The evolutionary implications of these results are discussed.     

The seminal vesicle of the African catfish,Clarias gariepinus

Summary The seminal vesicle of the African catfish, Clarias gariepinus, consists of 36–44 fingerlike lobes built up of tubules in which a fluid is secreted containing acid polysaccharides, acid-, neutral- and basic proteins, and phospholipids. In this fluid sperm cells are stored. The seminal vesicle fluid immobilizes the sperm cells. After ejaculation, it prolongs the period of sperm activity. The seminal vesicle fluid is secreted by the epithelium lining the tubules. The tubules in the proximal part of the lobes are predominantly lined by a simple cylindrical and those of the distal part by a simple squamous epithelium. These epithelial cells contain enzymes involved in energy-liberating processes, the enzyme activites being proportional to the height of the cells. Interstitial cells between the tubules have enzyme-histochemical and ultrastructural features indicative of steroid biosynthesis. Similar characteristics are found in testicular interstitial cells. The most rostral seminal vesicle lobes and the most caudal testicular efferent tubules form a network of tubules that opens at the point where the paired parts of the sperm ducts fuse with each other. The tubules of most seminal vesicle lobes, however, form a complex system that fuses with the unpaired part of the sperm duct.     

Microgeographic variation in allozyme frequencies in relation to the degree of exposure to wave action in the dogwhelk Nucella lapillus (L.) (Prosobranchia: Muricacea)

Nucella lapillus from 15 sites 50 m to 21 km apart in S. Devon, S. W. England were analysed for allozyme variation at eight soluble enzyme loci. Sites were classified as either Exposed or Sheltered and a hierarchical analysis of allozyme variation carried out using Wright's Fixation Index, F_ST. Whelks from Sheltered sites segregated for alleles at the Est-3, Lap-2, Pep-2 and Mdh-1 loci which were virtually absent from exposed sites resulting in high F_ST values (0.289–0.506) when all samples were included. Consequently mean heterozygosity of the Sheltered samples was roughly twice that of the Exposed. Between Sheltered sites the frequencies of these 'additional' alleles varied substantially, even on a microgeographic scale and were found to be highly correlated with exposure. Within individuals the presence of the 'sheltered' alleles was correlated with the possession of the 'sheltered' shell shape as indicated by length divided by aperture height. This must necessarily be the case, however, if both are related independently to exposure. Although these correlations imply the action of selection there is evidence within the data for stochastic factors affecting the pattern observed. Complicating the picture further is the correspondence observed in the distribution of the 'sheltered' alleles with the known distribution of chromosomal translocations. Phenotypic associations within individuals also support the hypothesis that variation at the Est-3, Lap-2, Mdh-1 and Pet-2 loci is related to variation in chromosome number. However, the nature of the relations of karyotype and allozyme variation with shell shape and exposure remain speculative.     

Morphometric analysis of interspecific and microgeographic variation of crayfish from a Mexican cave

Two undescribed species of Procambarus crayfish (Crustacea, Decapoda) inhabit the subterranean stream running in the recently explored Cueva de Los Camarones, Chiapas, Mexico. Individuals ranging from dark, robust, large-eyed forms with an epigean mien to pale, comparatively slender, microphthalmic ones resembling related troglobites were found, but only the extremes could be distinguished visually. Evolutionary relationships among individuals were investigated morphometrically by means of multivariate analysis'on 14 body dimensions. These analyses revealed a significant discontinuity between the two species, mainly determined by the shape of the rostrum, chelae and telson. The occurrence of a few aberrant phenotypes may indicate the existence of some gene flow between the two species.
Microgeographic variation was demonstrated within the less cavernicolous species. The characters involved were the same as those that discriminate between the two species. These results are compared with allozymic data presented in a parallel paper and the role of genie introgression and environmental induction are discussed.     

Intraspecific variation in the postcranial skeleton morphology in African clariids: a case study of extreme phenotypic plasticity

Taxonomic relationships within the Clariidae, especially within the anguilliform species, are currently ambiguous due to the lack of a reliable structure of valid generic and specific characteristics. Based on the information available, it is difficult to properly diagnose the different elongated genera and species; this is due in part to a high degree of variability of certain traits generally considered to be important taxonomically. For example, the caudal skeleton is often considered to be an important diagnostic trait. However, the degree of phenotypic plasticity has not hitherto been adequately assessed. This paper deals with interspecific variation of the caudal skeleton of Clarias gariepinus , Platyallabes tihoni , Platyclarias machadoi , Gymnallabes typus , Channallabes apus and Dolichallabes microphthalmus . The caudal skeleton of C. apus is studied, using specimens from three regions in Gabon. Hypural fusions and haemal and neural spines show most variation. The observed morphological variation appears to be geographically independent, in contrast to other morphological features such as vertebrae.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 437–446.     

Development of sensory organs in larvae of African catfish Clarias gariepinus

African catfish Clarias gariepinus hatched with morphologically immature features; however, sensory organs developed rapidly with fish growth. Although the eyes of newly hatched larvae were immature without pigment, in 2 day‐old larvae, the retina of the eyes had already developed except for the rod cells. No free neuromasts were observed in newly hatched larvae. In 1 day‐old larvae, however, free neuromasts were observed on the head and trunk. Free neuromasts increased with larval growth. Newly hatched larvae had simple round‐shaped otic vesicles; however, all sensory epithelia of the inner ear were observed until the larvae were 3 days old. Two day‐old larvae swam horizontally, had sharp teeth, commenced ingesting rotifers and also artificial feed (small‐size pellets) under both light and dark conditions; by then the larvae already had many taste buds. Three day‐old larvae showed negative phototaxis and cannibalism by eating their conspecifics. Most of the free neuromasts observed in this study had the peculiar feature of many microvilli around the sensory cells on the apical surface. Detected free neuromasts as ordinary type lateral‐line organs were not observed in previous reports in teleosts. In 10 day‐old larvae, there were two lines of free neuromasts on the flank and lower edge of the trunk; presumptive canal neuromasts were oval shaped and had begun to sink under the skin. The direction of maximum sensitivity of the neuromasts was parallel with the longitudinal axis of their elliptical apical surface.     

Comparative studies of allozyme loci in Drosophila simulans and Drosophila melanogaster. I. Three dipeptidase loci

Genetic variation at three dipeptidase loci (Dip-A, Dip-B, and Dip-C) in Drosophila simulans was analyzed by starch gel electrophoresis. Dip-A was found to be polymorphic in four populations, while Dip-B and Dip-C were found to be polymorphic in one. The numbers of different alleles found at each respective locus were: Dip-A, two; Dip-B, two; and Dip-C, three. Dip-A was genetically mapped at 57.9 on the second chromosome, and Dip-B and Dip-C at 80.9 and 87.9 on the third chromosome, respectively. Neither Dip-B nor Dip-C has been mapped in D. melanogaster because both loci are apparently monomorphic. Their map positions in D. simulans with respect to flanking markers whose homologous genes have been cytogenetically localized in D. melanogaster suggested that they might be mapped cytogenetically by using available deficiencies in D. melanogaster. Accordingly, by the construction of interspecific hybrids which carried deficiencies of melanogaster and an allele of simulans with a mobility different from that of the fixed melanogaster allele, Dip-B and Dip-C were localized between 87F12-14 and 88C1-3 and between 87B5-6 and 87B8-10, respectively, in the salivary gland chromosomes of D. melanogaster. The similarity between these two species is discussed on the basis of these findings.     

Morphometric and genetic variation of small dwarf honeybees Apis andreniformis Smith, 1858 in Thailand

The small dwarf honey bee, Apis andreniformis, is a rare and patchily distributed Apis spp. and is one of the native Thai honey bees, yet little is known about its biodiversity. Thirty （27 Thai and 3 Malaysian） and 37 （32 Thai and 5 Malaysian） colonies of A. andreniformis were sampled for morphometric and genetic analysis, respectively. For morphometric analysis, 20 informative characters were used to determine the variation. After plotting the factor scores, A. andreniformis from across Thailand were found to belong to one group, a notion further supported by a cluster analysis generated dendrogram. However, clinal pattems in groups of bee morphometric characters were revealed by linear regression analysis. The body size of bees increases from South to North but decreases from West to East, although this may reflect altitude rather than longitude. Genetic variation was determined by sequence analysis of a 520 bp fragment of the mitochondrial cytochrome oxidase subunit b （cytb）. DNA polymorphism among bees from the mainland of Thailand is lower than that from Phuket Island and Chiang Mal. Although two main different groups of bees were obtained from phylogenetic trees constructed by neighbor-joining and unweighted pair-group method using arithmetic averages programs, no clear geographic signal was present. Thus, while the minor group （B） contained all of the samples from the only island sampled （Phuket in the south）, but not the southem mainland colonies, it also contained samples from the far northem inland region of Chiang Mai, other samples of which were firmly rooted in the major group （A）.     

A preliminary investigation of allozyme genetic variation and population geographical structure in Aphanius fasciatus from Italian brackish-water habitats

A total of 150 individuals from Aphanius fasciatus from coastal brackish-water habitats was analysed by allozyme electrophoresis to collect data on its genetic variation. From 22 enzymes, 43 putative enzyme-coding loci were resolved, 12 of which were polymorphic at P_0·99 level. Only one of the 31 probability tests showed a significant departure from the Hardy-Weinberg equilibrium. Aphanius fasciatus showed low levels of genetic polymorphism, with expected heterozygosity values ranging from 0·027 (S.E.=0·013) to 0·064 ( s.e. =0·023). Nei's genetic distances between populations ranged from 0·002 to 0·042. Weir & Cockerham F -statistics showed high levels of genetic heterogeneity among populations (jackknifed θ=0·302, s.e. =0·045) and estimates of N _m were < 1, indicating restricted gene flow. Significant positive correlation between genetic distance and geographical distance matrices, detected by Mantel's test ( g =1·941; P 0·001), is consistent with the prediction that the species is genetically structured by isolation-by-distance.     

Pack-hunting in two species of catfish, Clavias gariepinus and C. ngamensis, in the Okavango Delta, Botswana

During the annual drawdown in the Okavango Delta, Botswana, large shoals of catfish migrate upstream in the main river channels. The examination of samples of the sharptooth catfish Clarias gariepinus and blunttooth catfish C. ngamensis revealed that they were pack-hunting and selectively preying on two species of mormyrids, the bulldog Marcusenius macrolepidotus and the churchill Petrocephalus catostoma . The predation on mormyrids may be related to prey size and abundance. In addition, catfish may sense the electrical discharge given off by the mormyrids when disturbed. The catfish feed intensively for a few months and build up body reserves and reproductive condition prior to spawning on shallow floodplains with the onset of the annual floods from Angola.     

Comparative study on the cranial morphology of Gymnallabes typus (Siluriformes: Clariidae) and their less anguilliform relatives,Clariallabes melas and Clarias gariepinus

We compare the cranial morphology of four fish species with an increasing anguilliformism in the following order: Clarias gariepinus, Clariallabes melas, Gymnallabes typus, and Channallabes apus. The main anatomical‐morphological disparities are the stepwise reduction of the skull roof along with the relative enlargement of the external jaw muscles, which occurred in each of them. Gymnallabes typus and C. apus lack a bony protection to cover the jaw muscles. The neurocranial bones of C. gariepinus, however, form a closed, broad roof, whereas the width of the neurocranium in C. melas is intermediate. Several features of the clariid heads, such as the size of the mouth and the bands of small teeth, may be regarded as adaptations for manipulating large food particles, which are even more pronounced in anguilliform clariids. The jaw musculature of G. typus is hypertrophied and attached on a higher coronoid process of the lower jaw, causing a larger adductive force. The hyomandibula interdigitates more strongly with the neurocranium and its dentition with longer teeth is posteriorly extended, closer to the lower jaw articulation. The anguilliform clariids also have their cranial muscles modified to enable a wider gape. The adductor mandibulae and the levator operculi extend more posteriorly, and the anterior attachment site of the protractor hyoidei dorsalis shifts toward the sagittal plane of the head. A phylogenetic analysis of the Clariidae, which is in progress, could check the validity of Boulenger's hypothesis that predecessors of the primitive fishes, such as Heterobranchus and most Clarias, would have evolved into progressively anguilliform clariids. J. Morphol. 240:169–194, 1999. © 1999 Wiley‐Liss, Inc.     

The relevance of metrical, chromosomal and allozyme variation to the systematics of the genus Mus

The contribution of metrical, karyological and biochemical techniques towards taxonomic understanding is considered with respect to (1) the delimitation of species; (2) the classification of species at generic level; and (3) subspecific variation. All these techniques are useful for the discrimination of sibling species, with metrical discriminants especially important in helping to establish the geographical limits of species, being applicable to museum collections and to fossil material. In classification at the generic level multivariate morphometric analysis is of very limited value, but karyology and allozyme studies can make important contributions provided the majority of relevant species are examined. All techniques are relevant to establishing the major aspects of subspecific variation, for which formal subspecific nomenclature is rarely appropriate. Problems of extrapolation from inadequate samples are just as acute when using these techniques as with more traditional taxonomy based on morphology. Clear presentation of results in the form of data matrices and dendrograms is important in facilitating the integration of data into a useful taxonomic system.     

Temperature-induced changes of early development and yolk utilization in the African catfish Clarias gariepinus

Artificially fertilized eggs and yolk-sac larvae of a freshwater tropical/subtropical fish Clarias gariepinus receiving no external food were incubated at 22, 25 and 28° C until full yolk resorption. Developmental time, size and matter composition (CHNS-O Analyzer and ashing) were assessed at egg fertilization, hatching and yolk resorption; respiration was measured every 4–5 h. The course of acceleration of C. gariepinus embryonic developmental rate with temperature ( Q_{10 dev}) was compared over the temperature range to those of Cyprinus carpio and Oncorhynchus mykiss ; they differed greatly, but were similar when compared on the basis of effective temperatures specific to each fish. Specific growth rates for energy (88, 150 and 183% per day at 22,25 and 28° C, respectively) as well as the conversion efficiencies of egg energy (64, 71 and 68%, respectively) and protein (71, 78 and 76%, respectively) in C. gariepinus larval tissues were higher than those known for the endogenous feeding period of coldwater and temperate fish species. In C. gariepinus at the end of yolk resorption, the carbon percentage and caloric values of dry weight, size (in terms of dry matter, minerals, protein and energy per larva) and transformation efficiencies were lowest at 22° C, highest at 25° C and had slightly decreased at 28° C. A tentative mechanism which leads to the positive or negative response of body size to temperature over the viable temperature range is defined.