Growth and morphological development of laboratory-reared larval and juvenile bighead catfish Clarias macrocephalus (Siluriformes: Clariidae)

Morphological development in laboratory-reared larval and juvenile bighead catfish Clarias macrocephalus is described. Body length (BL) of larvae and juveniles was 3.4 ± 0.3 (mean ± SD) mm just after hatching, reaching 11.3 ± 1.0 mm by day 16, and 24.2 ± 2.8 mm by day 40. Overall aggregate fin ray numbers (except for caudal fin procurrent rays) attained full complements by 15.2 mm BL. Gill buds appeared on day 0, those of barbels (four pairs) and primordial nostrils on day 1, and pectoral fins on day 3. All larvae began feeding by day 3. Conical teeth were observed on day 7. Notochord flexion began on day 2, the yolk being completely absorbed during days 7–9. Melanophores were scarce at hatching, increasing with growth to cover almost the entire body except the ventral surface of the abdominal cavity. Proportions of head length, pre-anal length, body depth, eye diameter, and maxillary barbel length became relatively constant after yolk absorption, those of snout length and upper jaw length increasing until ca. 12–13 mm BL and decreasing thereafter. Suprabranchial organ started developing in postflexion larval stage larger than ca. 11.0 mm BL (day 16), and air-breathing was suggested to be functional at that time.     

Occurrence of biflagellate spermatozoa in Cetopsidae, Aspredinidae, and Nematogenyidae (Teleostei: Ostariophysi: Siluriformes)

In the present study spermiogenesis was investigated in Cetopsis coecutiens (Cetopsidae), and Bunocephalus amazonicus (Aspredinidae), while spermatozoa ultrastructure was investigated in C. coecutiens, B. amazonicus, and Nematogenys inermis (Nematogenyidae). Aspredinidae and Cetopsidae share a spermatogenesis of the semicystic type, and a particular type of spermiogenesis process not reported in any fish group. In the three species analyzed, spermatozoa are biflagellate with flagella having the classical axoneme formulae (9 + 2). The analysis of thirteen characters showed the presence of eight characters shared by Cetopsidae and Aspredinidae, and six characters shared by Cetopsidae and Nematogenyidae, which may suggest that these three families may be more related than actually hypothesized, comprising a very primitive siluriform lineage originated after Diplomystidae.     

Africa's Clarias gariepinus (Teleostei: Clariidae) appears in rivers in Brazil

As a major tributary of the Nyl River, and ultimately for the Nylsvley wetland, the Olifantspruit, Limpopo province, South Africa, was investigated during the summer (high flow) and winter (low flow) of 2007 at three sites. This preliminary study used physical and biological indicators to determine the quality of the water that ultimately flows into Nylsvley. Significant seasonal differences were found. The observed differences relate to habitat structural differences and human activities in the catchment. Key findings included higher water temperatures during the high-flow period than during the low-flow period. The higher temperatures were accompanied by lower concentrations of dissolved oxygen at all sites. In total, 13 fish species were recorded, with most being found in the pool biotopes. The Nantes site, located nearest to the Nylsvley wetland, had the highest number of fish species, possibly indicating a linkage between these two systems. The most common macroinvertebrate families were the Baetidae, Aeshnidae and Coenagrionidae. It can be assumed that this river acts as an important refuge area for fish and macroinvertebrates from the Nyl River, and therefore it is important to conserve the Olifantspruit.     

Insight into the phylogeny of African Clariidae (Teleostei, Siluriformes): implications for their body shape evolution, biogeography, and taxonomy

The phylogenetic relationships among Clariidae species (Teleostei, Siluriformes) were assessed using 563 nucleotides of the cytochrome b mitochondrial gene. We included 32 Clariidae species representative of seven genera in our analysis. Hetropneustes fossilis (Heteropneustidae) and Clarotes laticeps (Claroteidae) were used as outgroups. The molecular data identified two evolutionary lineages that correspond on one hand to African species and on the other hand to Asian species. Morphological and osteological evolution in Clariidae did not follow an orthogenetic series. Species with robust body, strong ossified head, and large adipose fin were not ancestral ones and eel-like species were not phylogenetically related and represent independent adaptation to life in mud. Adaptation to life in deep water occurred two times independently in lake Tanganyika (with Dinotopterus cunningtoni) and in Lake Malawi (with Bathyclarias species). Molecular dating using a molecular clock of 1% divergence per million years and a comparison with fossils records allowed an estimate of the timing of cladogenesis within the species studied. The Clariidae family originated in Asia 50 MY ago but contemporary African and Asian studied species originated from a common ancestor that was present on the Arabian plate about 15 MY ago. Systematic implications of these results are also discussed.     

Bacterial infection of mudfish Clarias gariepinus (Siluriformes: Clariidae) fingerlings in tropical nursery ponds

Bacterial infection among the most common cultured mudfish Clarias gariepinus in Africa, has become a cause of concern, because it constitutes the largest economic loss in fish farms. In order to provide useful biological data of the pathogens for good management practices, samples were collected monthly between January 2008 and December 2009 in three monoculture nursery ponds, located in three different positions: upriver (A, grassland), mid-river (B, mixed forest and grassland) and downriver (C, rainforest) along 200 km length of Cross River floodplains, Nigeria. A total of 720 fingerlings between 15.1 and 20.7 g were analyzed to determine the degree of infection. The bacterial pathogens were taken from their external surfaces, and were isolated and identified by standard methods. The caudal fins of fingerlings from pond A had the highest bacterial load (5.8 x 10(3) cfu/g), while the least counts (1.2 x 103 cfu/g) were identified on the head of fish from pond C, with Flexibacter columnaris as the major etiological agent. Pseudomonas fluorescens, Aeromonas hydrophila, Escherichia coli, Staphylococcus aureus and Micrococcus luteus were identified as co-isolates with P. fluorescens as dominant (0.7 x 10(2) cfu/mL) co-isolates in pond water. Clinical signs of five white spots with red periphery appeared on the external surface of infected fish. All the fish sampled, died after 4 to 9 days. There was no significant difference in the bacterial counts between different ponds, but the difference between fish organs/parts examined was significant. Fish from these ponds are therefore potentially dangerous to consumers and highly devalued, with the economic impact to producers. Preventive methods to avoid these infections are recommended.     

Age, growth and mortality of Clarias gariepinus (Siluriformes: Clariidae) in the Mid-Cross River-Floodplain ecosystem, Nigeria

Clarias gariepinus is a threatened highly prized species used for some elite ceremonies by the local communities. Artisanal fishers take advantage of this species annual breeding migration from the lower Cross River to the floodplain lakes in Mid-Cross River during the rainy season, and some migrant stocks are not able to spawn. Since there is a lack of information on this species population dynamics in the Mid-Cross area, this study aimed to evaluate the age, growth and mortality to support the development of effective management plans. For this, monthly overnight gill net catches (from 6 to 72mm mesh sizes) were developed between March 2005 and February 2007. Growth parameters were determined using the FiSAT II length-frequency distribution. A total of 1 421 fish were collected during the survey. The asymptotic growth (L(infinity)) was 80.24cm, growth rate (K) was 0.49/year while the longevity was 6.12 years. The annual instantaneous rate of total mortality (Z) was 2.54/year and the natural mortality (M) was 0.88. Fishing mortality (1.66/year) was higher than the biological reference points (F(opt) = 0.83 and F(limit) = 1.11) and the exploitation rate (0.66) was higher than the predicted value (E(max) = 0.64) indicating that C. gariepinus was over exploited in the Mid-Cross River-Floodplain ecosystem. Some recommended immediate management actions are to strengthen the ban of ichthyocide fishing, closure of the floodplain lakes for most of the year, restricted access to the migratory path of the fish during the flood period and vocational training to the fishers. In order to recover and maintain a sustainable harvest, I suggest that a multi-sector stakeholder group should be formed with governmental agents, community leaders, fishers, fisheries scientists and non-governmental organizations. These short and long term measures, if carefully applied, will facilitate recovery of the fishery.     

A new genus and species of proteocephalidean (Cestoda) from Clarias catfishes (Siluriformes: Clariidae) in Africa

A new proteocephalidean cestode is described from 2 catfishes, Clarias gariepinus (type host) and C. cf. anguillaris (Siluriformes: Clariidae), from Ethiopia (type locality), Sudan, Tanzania, and Zimbabwe, and a new genus, Barsonella, is proposed to accommodate it. The genus belongs to the Proteocephalinae because its genital organs (testes, ovary, vitellarium, and uterus) are situated in the medulla. Barsonella lafoni, the type and only species of the new genus, is characterized mainly by the possession of an additional opening of each sucker; circular musculature on the anterior margin of suckers, serving as a sphincter; a small thin-walled glandular apical organ; absence of well-developed osmoregulatory canals in mature, pregravid, and gravid proglottids; and a large strobila, up to 173 mm long and 3.2 mm wide. Species of Marsypocephalus Wedl, 1861 (Marsypocephalinae), other large-sized proteocephalidean tapeworms occurring sympatrically in African catfishes (Clarias and Heterobranchus) and also possessing a sphincter-like, circular musculature on the anterior part of suckers, differ from B. lafoni in the absence of an additional sucker opening and glandular apical organ, the cortical position of the testes, well-developed osmoregulatory canals throughout the strobila, and a large cirrus sac. Proteocephalus glanduligerus (Janicki, 1928), another cestode parasitic in Clarias spp. in Africa, is much smaller than B. lafoni (maximum length 15 mm), has suckers without additional opening and circular musculature on the suckers, a large-sized glandular organ, much larger than suckers, and well-developed osmoregulatory canals. Comparison of partial sequences of the 28S rRNA gene for 7 samples of B. lafoni from 2 different hosts and 4 localities in Ethiopia, Sudan, and Tanzania has shown a very low genetic variability. In a limited phylogenetic analysis, B. lafoni formed a clade with Corallobothrium solidum Fritsch, 1886 (Proteocephalidae: Corallobothriinae), an African electric catfish parasite. This clade was the sister group of almost all Neotropical taxa from pimelodid and other catfishes.     

Reconstruction of Electric Discharge Patterns and Electrogenesis Mechanism in African Sharptooth Catfish Clarias gariepinus (Clariidae,Siluriformes)

Doklady Biological Sciences - Electrical discharges (EDs) in the African sharptooth catfish Clarias gariepinus were studied. Irregular monopolar EDs, lasting for 8–10 ms and longer, and more...     

Effects of jaw adductor hypertrophy on buccal expansions during feeding of air breathing catfishes (Teleostei,Clariidae)

Some species of Clariidae (air breathing catfishes) have extremely well developed (hypertrophied) jaw closing muscles that increase the maximal biting force of these species. As these enlarged jaw muscles tightly cover the suspensoria, which are firmly connected to the neurocranium, we expect diminished lateral expansions during suction for species with hypertrophied jaw muscles. In turn, this could imply a reduced suction performance for these species. Compared to Clarias gariepinus, which has relatively small jaw closers, Clariallabes longicauda shows a clear hypertrophy of the jaw adductors. A kinematic analysis of prey capture in these two species is presented here. As predicted, Clariallabes longicauda shows less lateral expansion (average abduction of the hyoids of 19.0°) than Clarias gariepinus (abduction of 31.1°). However, our data indicate that the decrease in lateral expansion capacity in the species with excessive adductor development is compensated for by a larger and faster ventral expansion of the buccal cavity by depression of the hyoid.     

The study of sensory bases of the feeding behavior of the African catfish Clarias gariepinus (Clariidae,Siluriformes)

An experimental study of the role of vision and some other sensory systems in the feeding behavior of the African catfish Clarias gariepinus (SL 20–24 cm, weight 80–95 g) was performed. It was shown that catfish similarly efficiently detect pellets of artificial food in the light and in the dark; in the dark, they display a greater preference for liver pieces than for pellets of artificial food of the same size. Blue pellets were most attractive for fish; red pellets, less attractive; and green pellets were the least attractive. Color selectivity is exhibited by catfish in the light at various combinations of pellets of different colors delivered simultaneously, but is lost in total darkness. The data obtained indicate the polysensory basis of the feeding behavior of catfish. In the light, a well-developed visual reception provides not only for a successful search for food, but also for a selective choice of food items by color. The olfactory and taste properties of food are important regulators of feeding under various light conditions. Thus, C. gariepinus, like other euryphagous fish, lacks a profound sensory specialization in the feeding behavior. When environmental conditions change, the role of the leading sensory system may pass from one sense organ to another.     

Food composition and digestive enzymes in the gut of pond-cultured Clarias isheriensis (Sydenham 1980), (Siluriformes: Clariidae)

Food composition, diestive enzyme distribution and activity in the gut of pond-cultured Clarias isheriensis were studied It had an omnivorous diet but fed mainly on plancon (particularly Cyanophyceae) and detritus. Qualitative determinations of digestive enzymes in the gut showed that it is capable of digesting carbohydrates, proteins and lipids in its diet. Carbohydrases (amylase, cellulase, maltase, salicinase, sucrase and trehalase) were detected and their activities restricted to the stomach, duodenum and ileum. The incidence of cellulase activity could be responsible for the capacity of this fish species to digest large quantities of Cyanophyceae present in the pond. Lower activity of proteases (chymotrypsin, pepsin and trypsin) and lipases were recorded. Enzyme activity was not recorded in either oesophagus or rectum. The relative distribution and activity of the various digestive enzymes were possibly induced by the nutritional requirements of this catfish species.     

Chromosome analysis of walking catfish,Clarias magur (Teleostei,Siluriformes, Clariidae), using staining,FISH with 18S, 5S and BAC probes

The chromosomal characteristics of Clarias magur were examined using conventional (Giemsa-staining, Ag-impregnation and CMA₃ + DAPI fluorescence) and molecular/ FISH (18S & 5S rDNA probes + one BAC DNA probe) cytogenetic tools. The diploid chromosome number was 50 and the karyotype consisted of 14 metacentric, 20 sub-metacentric, 8 sub-telocentric, 8 acrocentric chromosomes with 84 chromosome arms without any heteromorphic pair. The C-heterochromatic blocks were located on centromeric position of 13 pairs of chromosomes. The NOR sites, visualized by AgNO₃- and CMA₃- staining, were situated at p arms of chromosome pair No. 21, which also corresponded to 18S rDNA site visualized by FISH. The FISH signal of ICF_001_D19 clone probe was observed on 18th chromosome pair. The findings of the present study on C. magur provided valuable markers for the chromosome identification and locations of genes of the BAC clone on the chromosome will lead to the construction of physical map of genome of this species.     

Sperm ultrastructure and a new type of spermiogenesis in two species of Pimelodidae, with a comparative review of sperm ultrastructure in Siluriformes (Teleostei: Ostariophysi)

During spermiogenesis, the spermatids of the pimelodid species Pimelodus maculatus and Pseudoplatystoma fasciatum show a central flagellum development, no rotation of the nucleus, and no nuclear fossa formation, in contrast to all previously described spermatids of Teleostei. These characteristics are interpreted as belonging to a new type of spermiogenesis, named here type III, which is peculiar to the family Pimelodidae. In P. maculatus and P. fasciatum, spermatozoa possess a spherical head and no acrosome; their nucleus contains highly condensed, homogeneous chromatin with small electron-lucent areas; and a nuclear fossa is not present. The centriolar complex lies close to the nucleus. The midpiece is small, has no true cytoplasmic channel, and contains many elongate and interconnected vesicles. Several spherical to oblong mitochondria are located around the centriolar complex. The flagellum displays the classical axoneme (9+2) and no lateral fins. Only minor differences were observed among the pimelodid species and genera. Otherwise, spermiogenesis and spermatozoa in the two species of Pimelodidae studied exhibit many characteristics that are not found in other siluriform families, mainly the type III spermiogenesis.     

Ontogenetic shift in mouth opening mechanisms in a catfish (Clariidae, Siluriformes): a response to increasing functional demands

During ontogeny, larval fish have to deal with increasing nutritional and respiratory demands as they grow. As early ontogeny is characterized by an increasing complexity of moving structural elements composing a fish skull, some constraints will have to be met when developing mechanisms, which enable feeding and respiration, arise at a certain developmental stage. This article focuses on the presence/absence of a possible functional response in mouth opening during ontogeny in Clarias gariepinus. Some reflections are given, based on morphological data, as well as related function-analysis data from the literature. Starting shortly after hatching, a total of up to five different mouth opening mechanisms may become functional. Of these, three may remain functional in the adult. As could be expected, the apparatuses that enable these mechanisms show an increase in complexity, as well as a putative improvement in mouth opening capacity. Initially, two consecutive mechanisms may allow a restricted depression of the lower jaw (both passively and actively). Synchronously, two more mechanisms may arise, which involve the coupling of the hyoid depression to the mouth opening. At about 11 mm SL a fifth mechanism becomes established, better known as the opercular mouth opening mechanism. An overlapping chronology of functionality of the different mechanisms, as well as differences in efficiencies, could be an indication of the absence of a true critical period in C. gariepinus (at least in relation to mouth opening), as well as the possible presence of a shift in feeding type. Finally, the coupling of the chronology of the shift in mouth opening mechanisms and several morphological, behavioral, and physiological changes during ontogeny, related to feeding and respiration, make it possible to distinguish five important phases in the early life history of C. gariepinus.     

Sperm of Doradidae (Teleostei: Siluriformes)

Spermatic characteristics were studied in 10 species representing several distinct groups within the catfish family Doradidae. Interestingly, different types of spermatogenesis, spermiogenesis and spermatozoa are correlated with intrafamilial groups previously proposed for Doradidae. Semi-cystic spermatogenesis, modified Type III spermiogenesis, and biflagellate sperm appear to be unique within Doradidae to the subfamily Astrodoradinae. Other doradid species have sperm with a single flagellum, cystic spermatogenesis, and spermiogenesis of Type I (Pterodoras granulosus, Rhinodoras dorbignyi), Type I modified (Oxydoras kneri), or Type III (Trachydoras paraguayensis). Doradids have an external mode of fertilization, and share a few spermatic characteristics, such as cystic spermatogenesis, Type I spermiogenesis and uniflagellate sperm, with its sister group Auchenipteridae, a family exhibiting sperm modifications associated with insemination and internal fertilization. Semi-cystic spermatogenesis and biflagellate spermatozoa are also found in Aspredinidae, and corroborate recent proposals that Aspredinidae and Doradoidea (Doradidae + Auchenipteridae) are sister groups and that Astrodoradinae occupies a basal position within Doradidae. The co-occurrence in various catfish families of semi-cystic spermatogenesis and either biflagellate spermatozoa (Aspredinidae, Cetopsidae, Doradidae, Malapturidae, Nematogenyidae) or uniflagellate sperm with two axonemes (Ariidae) reinforces the suggestion that such characteristics are correlated. Semi-cystic spermatogenesis and biflagellate sperm may represent ancestral conditions for Loricarioidei and Siluroidei of Siluriformes as they occur in putatively basal members of each suborder, Nematogenyidae and Cetopsidae, respectively. However, if semi-cystic spermatogenesis and biflagellate sperm are ancestral for Siluriformes, cystic spermatogenesis and uniflagellate sperm have arisen independently in multiple lineages including Diplomystidae, sister group to Siluroidei.     

Ecological and phylogenetic influence on mandible shape variation of South American caviomorph rodents (Rodentia: Hystricomorpha)

We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Chinchilloidea, and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence of phylogeny and ecology on this variation was assessed using phylogenetic comparative methods. Most morphological variation was concentrated in condylar, coronoid, and angular processes, as well as the diastema. Features potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process, and diastema) were present only in octodontoids; cavioids showed opposing trends, which could represent a structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera were distributed in the morphospace according to their classification into superfamilial clades. The phylogenetic signal for shape components was significant along phylogeny, whereas the relationship between mandibular shape and ecology was nonsignificant when phylogenetic structure was taken into account. An early evolutionary divergence in the mandible shape among major caviomorph clades would explain the observed strong phylogenetic influence on the variation of this structure. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 828–837.     

Genetic and morphological variability of the European mudminnow Umbra krameri (Teleostei,Umbridae) in Serbia and in Bosnia and Herzegovina,a basis for future conservation activities

As a basis for future conservation activities, the genetic and external body morphology variability of the European mudminnow Umbra krameri, a highly endangered fish species in Serbia and in Bosnia and Herzegovina, was determined for existing populations with the use of molecular markers (mitochondrial and microsatellite DNA) and geometric morphometric methods. Mitochondrial DNA cytochrome b gene analysis revealed two previously undescribed haplotypes: Da1 (the Lugomir population from the Danube River basin) and Sa1 (the Bakreni Batar and the Gromi?elj populations from the Sava River system), with a corresponding genetic distance of 0·7%. Paired values of F_ST and D_AS distances for microsatellite marker data show that the difference between the Danube and the Sava populations is seven to nine times higher than the difference between the populations within the Sava River system. Geometric morphometric analyses also support a clear separation of the Lugomir population from the Bakreni Batar and the Gromi?elj populations. The analysis of the body shape variation, however, indicates a significant difference between the two genetically indistinguishable Sava populations. The observed genetic and phenetic relationships of the analysed mudminnow populations most probably represent a consequence of historical, geographical and ecological factors. These results will offer guidelines for future protection, conservation and sustainable management of this species in the region.     

Apparent digestibility of crude protein and gross energy in some plant and animal-based feedstuffs by Clarias isheriensis (Siluriformes: Clariidae) (Sydenham 1980)

Apparent digestibility coefficient (ACD) of dry matter, crude protein and gross energy of white fish meal, blood meal, poultry by-product meal, hydrolysed feather meal, shrimp head meal, meat and bone meal, soybean meal, cottonseed meal, peanut meal, yellow maize, corn starch, cassava meal, sorghum, rice bran and cocoa pod meal were determined for Clarias isheriensis (47.5–51.2 g) fed to satiation with diets containing each test feedstuff in a 30:70 mixture with a reference diet, and chromium oxide as an indicator using the dissection technique. ADC_protein values ranged from 50 to 93 % while ADC_energy ranged from 42 to 98 %. Protein and energy content of animal or plant feed-stuffs were equally digestible to C. isheriensis.