Observations on the larval development of Mystus macvopterus (Bleeker): Bagridae

From June to July 1988, larvae of Mystus macropterus (Bleeker) were obtained by artificial propagation of spawners collected from the Jialing River, China. Larvae grown in water temperatures ranging from 26 to 29°C were fully developed at approximately 20 days. The newly-hatched larvae measured 6.0–7.5 mm t.l. , exceeding the dimensions of any known newly-hatched larvae of freshwater catfishes indigenous to China. Five days after hatching, when the larvae were 11.4 mm t.l. and the prolarval stage was complete, exogenous feeding commenced. Twelve days after hatching, at 18.4 mm t.l. , the yolk sac disappeared, organogenesis was almost complete and the juvenile period began. At 20 days post-hatching, at 23.0 mm t.l. , the lateral line system had formed and the juveniles resembled the adults with respect to all external features, which signalled the end of thejuvenile period. Comparison of the larval development in eight species ofeconomic freshwater catfishes shows that the most significant aspect of the larval development of M. macropterus is the sustained (6–7 days) mixed nourishment period and the early differentiation of organs, which enhances the survival rate of the larvae.     

Reproductive biology of Mystus vittatus (Bloch) (Bagridae: Siluriformes) from Guntur,Andhra Pradesh

Maturation, minimum length at first maturity, spawning season, spawning periodicity, sex-ratio and absolute fecundity of Mystus vittatus, a common bagrid catfish, have been investigated. The observations show that spawning takes place during September and October. Each individual spawns only once in the season as evidenced by the study of the intraovarian ova. Females dominate the catches, and absolute fecundity (F) can be expressed by% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOabaeqabaGaciiBai% aac+gacaGGNbGaaeiiaiaabAeacaqGGaGaaeypaiaabccacaqGTaGa% ae4maiaab6cacaqGYaGaaeyoaiaabkdacaqGGaGaae4kaiaabccaca% qG0aGaaeOlaiaabgdacaqG3aGaaeymaiaabgdacaqGGaGaaeiBaiaa% b+gacaqGNbGaaeiiaiaabYeaaeaacaqGHbGaaeOBaiaabsgacaqGGa% GaaeOraiaabccacaqG9aGaaeiiaiaab2cacaqGXaGaaeOlaiaabwda% caqG0aGaaeinaiaabwdacaqGGaGaae4kaiaabccacaqGWaGaaeOlai% aabMdacaqG0aGaae4naiaabkdacaqGGaGaae4vaaaaaa!5FCC!\[\begin{gathered} \log {\text{ F = - 3}}{\text{.292 + 4}}{\text{.1711 log L}} \hfill \\ {\text{and F = - 1}}{\text{.5445 + 0}}{\text{.9472 W}} \hfill \\ \end{gathered} \]     

Condition, length–weight and length–length relationships of the Asian striped catfish Mystus vittatus (Bloch, 1794) (Siluriformes: Bagridae) in the Mathabhanga River, southwestern Bangladesh

The present study describes the annual condition as well the length–weight (LWR) and length–length relationships (LLR) of the Asian striped catfish, Mystus vittatus (Bloch, 1794) (Siluriformes: Bagridae), an important fishery in the Mathabhanga River (SW Bangladesh). A total of 2438 specimens (3.60–9.60 cm standard length) used in this study was caught with traditional fishing gear from January to December 2004. Overall, the allometric coefficient b of the LWR was close to the isometric value (b = 3.058), although it suggested negative allometric growth for males (b = 2.959) whilst positive allometric growth for females (b = 3.134). The results further indicated that the LLRs were highly correlated (r² > 0.989, P < 0.001). The monthly gonadosomatic index showed that the reproductive period of M. vittatus began in April, and ended in August when the highest values of the Fulton's condition factor (K) indicated their recovery. These results will be useful for fishery managers to impose adequate regulations for sustainable fishery management not only in the Mathabhanga River of Bangladesh but also in neighbouring countries.     

Complete mitochondrial genome of the Korean stumpy bullhead Pseudobagrus brevicorpus (Siluriformes, Bagridae)

We describe the complete mitochondrial genome sequence of the Korean stumpy bullhead Pseudobagrus brevicorpus, which is an endangered species in Korea. The circle genome (16,526?bp) consists of 13 protein coding, 22 tRNA, 2 rRNA genes and 1 control region. It has the typical vertebrate mitochondrial gene arrangement.     

Effect of long photoperiod on the maturation of ovary of the catfish, Mystus tengara (Ham.)

A study has been made of the effect of photoperiodism on the ovarian maturation of fresh water teleost, Mystus tengara (Ham.). The magnitude of ovarian recrudescence is more during maturing virgin phase as compared to during immature virgin and preparatory virgin phases in long photoperiod (14 hours/day) treated fish. Thus, the response of the ovary to long photoperiod increases with the approach of natural spawning period. The mature eggs are more in long photoperiod treated fish than in controls exposed to 12 hours/day photoperiod. In long photoperiod treated fish, prespawning period is reduced considerably. During spawning and post-spawning periods, the ovaries are refractory, since long photoperiod is ineffective in maintaining gravid ovaries beyond spawning period and the ovarian regression during post spawning period sets in regardless of nature of photoperiod treatment.     

Chromosomal evolution in naked catfishes (Bagridae,Siluriformes): A comparative chromosome mapping study

We analyzed the distribution of repetitive DNA sequences on the chromosomes of nine species of the Bagridae from Thailand, i.e., Hemibagrus filamentus; H. nemurus; H. wyckii; H. wyckioides; Mystus atrifasciatus; M. multiradiatus; M. mysticetus; M. bocourti and Pseudomystus siamensis. Two classes of microsatellites and one transposable element (TE) were mapped by fluorescence in situ hybridization. The distribution of the repetitive sequences was comparatively analyzed in view to investigate their contribution in the chromosomal evolution of this fish group. In all species the microsatellites (CA)₁₅ and (GA)₁₅ are abundantly distributed in all chromosomes, usually in the telomeric regions. The retrotransposable element Rex 1 is widely distributed over the whole genome including heterochromatin and euchromatin, but with an unexpected accumulation in one chromosome pair in some species. In fact, some species–specific patterns could be observed considering both microsatellites and TE distribution. The results demonstrated that the compartmentalization of repeated elements is not simply restricted to heterochromatic regions, as it has been postulated in the first concepts of the genomic organization of repetitive elements in genomes. Moreover, the organization of these repeats seems to reflect their intense and specific evolutionary pathway, providing new insights about the chromosomal evolution in the Bagridae.     

Studies on the biology of some freshwater fishes Part VI. Mystus cavasius (Ham.)

Summary The biology of a freshwater fish, M. cavasius with particular reference to its length frequency, breeding and food has been described. length frequency distribution gave an indication of 4 modes during the quarter, July–September.Both the sexes attain maturity when they are approximately 10 cm long. Females grow larger than the males and are more abundant in the population. The spawning of this fish seems to take place during August and September. Maturing ovaries of females show only one batch of eggs which is probably shed in a single spawning act. The condition factor of the fish has no correlation either with the seasonal changes in maturity or with the feeding rhythm. The fish has an omnivorous habit and consumes all types of food available in the habitat. The feeding is high during the monsoon and winter months and low during the summer months.This work was carried out in the Department of Zoology, Aligarh Muslim University, Aligarh, U.P. India in continuation of the series I–III by Qasim & Qasim (1964) and IV–V published elsewhere by the present author (1970–71).     

First record of Cymothoa indica (Crustacea, Isopoda, Cymothoidae) infecting the cultured catfish Mystus gulio in India

Cymothoa indica (Isopoda, Cymothoidae) is reported parasitizing the long-whiskered catfish Mystus gulio, cultured in an experimental cage in India. The specimens observed were adult males and females, which had mainly settled in the buccal cavity of juvenile catfish. The species was previously known from wild populations of Siganidae and Belonidae, but this is the first record of C. indica parasitizing the cultured long-whiskered catfish. Serious lesions, typical of a crustacean infection, were macroscopically visible inside the buccal cavity. The cumulative mortality, over a period of 10 d, was 100%. The parasitic problem was not successfully dealt with, due to an unexpected prevalence and very swift mortality.     

Spawning season, ovarian development and fecundity of female Trichomycterus corduvense (Osteichthyes, Siluriformes)

We studied female reproductive biology of Trichomycterus corduvense. The study was carried out in the Anizacate River (Córdoba, Argentina). Samples were collected throughout one year on a monthly basis. Seven oocyte phases were identified. Five ovarian stages were described based on the macroscopic analysis of the oocyte phases. The spawning season for the species ranges from October to February; it was determined based on variations in GSI and the existence of mature females. The dynamics of oocyte development of T. corduvense, indicated the asynchronism of maturation. The correlation coefficient between fecundity and the individual weight was very low. Therefore, we suggest that this coefficient cannot be used to predict T. corduvense fecundity.     

Preponderance of GC-rich sites in silver-stained nucleolus organizing regions of Rita rita (Hamilton) and Mystus gulio (Hamilton) (Bagridae, Pisces), as revealed by chromomycin A3-staining technique and scanning electron microscopic studies

The karyotypes of two species of catfish, Rita rita (Hamilton) (2n = 54; 14m + 34sm + 6st; NF = 102) and Mystus gulio (Hamilton) (2n = 58; 30m + 12sm + 2st + 14t, NF = 100) were studied through Giemsa-, silver- and chromomycin A(3)-staining techniques. The silver-stained karyotypes in both sexes of R. rita and M. gulio revealed that the nucleolus organizing regions were located terminally at the shorter arms (Tp) of one pair of submetacentric chromosomes, placed at positions Nos. 2 and 1, respectively, which was confirmed by scanning electron microscopy. Staining with a GC-specific fluorochrome, chromomycin A(3), produced bright fluorescence in the Ag-positive nucleolus organizer regions, suggesting thereby that nucleolus organizing regions actually included GC-rich sites of active r-RNA genes in metaphase chromosomes of these two bagrids. Further such studies are needed due to the extreme paucity of data on fish.     

Condition factor and diet of Chrysichthys nigrodigitatus and Chrysichthys auratus (Siluriformes: Bagridae) from Aiba Reservoir, Iwo, Nigeria

Chrysichthys nigrodigitatus and C. auratus are important, highly valued and threatened freshwater species. To contribute with their ecological knowledge, the condition factor and diet of these two congeneric species were studied between April 2005 and April 2006. Food items of fish were evaluated by occurrence and numerical abundance methods, and the possible changes among sexes, seasons and sizes were considered. Results showed that generally C. nigrodigitatus were better conditioned than C. auratus. The males of C. nigrodigitatus and females of C. auratus were in better condition than their respective opposite sex throughout the year, and during the wet season compared to the dry. The food items of C. nigrodigitatus and C. auratus were similar and comprised twelve species belonging to five groups: Insecta (three species), Crustacea (five species), Arachnida (one species), Rotifera (one species) and Mollusca (two species). Other food items included fish scales, unidentified green eggs, plant parts, detritus and sand. Insecta and Crustacea dominated the food items in both species. For C. nigrodigitatus, insect consumption increased with fish size, while Crustacea items decreased (from 89.59% for 8.1cm - 12.0cm size class to 1.58% for 20.1cm - 26.0cm size class). However, while C. auratus smaller sized fish preferred Crustacea (98.72% for 8.1cm -12.0 cm size class), larger sized fish had both groups in relatively similar amounts. Schoener Overlap Index for both species and between seasons is 1.00. Diet breadth ranged from 0.00-1.47 for C. nigrodigitatus and 0.00-1.32 for C. auratus. Food Richness ranged from 0.00-1.44 for both species. Gut Repletion Index for C. nigrodigitatus and C. auratus are 76.39% and 76.27% respectively. Although, there is considerable similarity and overlap in the utilization of food resource for both coexisting species, condition factor and feeding behavior suggest strategies to reduce intra- and interspecific competition.     

Insights into chromosomal evolution and sex determination of Pseudobagrus ussuriensis (Bagridae,Siluriformes) based on a chromosome-level genome

Pseudobagrus ussuriensis is an aquaculture catfish with significant sexual dimorphism. In this study, a chromosome-level genome with a size of 741.97 Mb was assembled for female P. ussuriensis. A total of 26 chromosome-level contigs covering 97.34% of the whole-genome assembly were obtained with an N50 of 28.53 Mb and an L50 of 11. A total of 24,075 protein-coding genes were identified, with 91.54% (22,039) genes being functionally annotated. Based on the genome assembly, four chromosome evolution clusters of catfishes were identified and the formation process of P. ussuriensis chromosomes was predicted. A total of 55 sex-related quantitative trait loci (QTLs) with a phenotypic variance explained value of 100% were located on chromosome 8 (chr08). The QTLs and other previously identified sex-specific markers were located in a sex-determining region of 16.83 Mb (from 6.90 to 23.73 Mb) on chr08, which was predicted as the X chromosome. The sex-determining region comprised 554 genes, with 135 of which being differently expressed between males and females/pseudofemales, and 16 candidate sex-determining genes were screened out. The results of this study provided a useful chromosome-level genome for genetic, genomic and evolutionary studies of P. ussuriensis, and also be useful for further studies on sex-determination mechanism analysis and sex-control breeding of this fish.