International Journal of Aquatic Biology
Volume:4 Issue: 5, Oct 2016

The karyological and cytological characteristics of an endemic cyprinodont fish of Iran, Aphanius darabensis Esmaeili, Teimori, Gholami & Reichenbacher, 2014 have been investigated for the first time by examining metaphase chromosomes spreads obtained from gill epithelial and kidney cells. The diploid chromosome number of A. darabensis is 48. The karyotype consisted of five submetacentric and 19 subtelocentric pairs of chromosomes (5smퟛ). The fundamental number (FN) is 58. Sex chromosomes were cytologically indistinguishable in this tooth-carp. According to this study and previous karyological reports from other cyprinodont species, it can be suggested that the diploid number (2n=48) is common amongst cyprinodont fishes. These results can be used as basic informations in population studies and management and conservation programs.

The histological status of adrenocortical tissues and the correlated seasonal changes in ovarian activities in Mystus vittatus was performed. The tubules and nests of interrenal and chromaffin cells were located in cephalic kidney around the main branches of posterior cardinal vein. Various female germ line cells were identified in the ovary based on size, distinctive features and histoarchitechture of the cells. However, on the basis of relative abundance and size of the different oocytes, the event of oogenesis has been found to occur in four distinct phases, including growth, maturation, spawning and post-spawning. The cytoplasmic features and the architecture of the interrenal and chromaffin cells varied during different phases of the reproductive cycle. During growth and maturation phases, the amount of cytoplasmic granules of interrenal cells increased than chromaffin cells that was in coincidence with the increase of early and late perinucleolar oocytes followed by highest frequency percentage of oocyte at stages IV and V. The cytoplasmic mass of interrenal cells was gradually elevated along with hypertrophied nuclei from the end of maturation and spawning phases also correlated with the increased frequency of mature oocytes. Therefore, gradual accumulation of cytoplasmic granules in the interrenal cells was noticed during post-spawning phase. The cytological variations in the interrenal and chromaffin cells harmonized with constitution of different ovarian cells during different reproductive phase in M. vittatus.

The members of mugilid species are usually difficult to recognize because of the well-known similarity observed in their external morphology. Nevertheless, their identification is very important for local fisheries management and conservation action. Therefore, in the present study we applied otolith morphology to evaluate its significance in identification of four selected mugilid species; Chelon subviridis (Valenciennes, 1836), Liza klunzingeri (Day, 1888), Ellochelon vaigiensis (Quoy & Gaimard, 1825) and Mugil cephalus Linnaeus, 1758 occurring in the Iranian waters of the Persian Gulf in southern Iran. The results indicated several otolith features to be important for identification of the selected mugilid species as follow; the position and sulcus centrality, the curvature of the cauda, and the type of anterior and posterior regions. Based on the total approach evidences, we conclude that otolith morphology in mugilid fishes can be evidently used for the species identification and probably estimation of their phylogeny. The findings are in agreement with the previous studies which documented taxonomic importance of otolith morphology.

Intraguild predation occurs when species competing for the same resource prey upon or parasitize one another. This may result in economic losses under commercial circumstances. A survey of the insect species of fish farms in Badagry and Ojo Areas of Lagos State, Nigeria was carried out followed by an evaluation of the predatory ability of Orthetrum abbotti nymphs on fish fry. Nymph predation was evaluated in the laboratory against fry of Clarias gariepinus and Oreochromis niloticus. Samples of insects were randomly collected from 10 earthen ponds, 10 concrete ponds and the vegetation surrounding the ponds and identified over a period of 12 weeks from three study fish farms. Six species of insects belonging to four orders namely Notonecta unifasciata, Gerris remigis, O. abbotti, Aedes aegypti, Dysticus marginalis and Acentria ephemerella syn. niveus were collected from the ponds. Studies on feeding preference of 5th nymphal instar of O. abbotti on fry of C. gariepinus and O. niloticus over other food types revealed that the dragonfly preferred to feed more on C. gariepinus fry than on O. niloticus although there was no significant difference in the number of O. niloticus and C. gariepinus fry preyed upon by O. abbotti nymphs.

The Ergene River is located in the Thrace Region of Turkey and is polluted by industrial and municipal waste. In the present study, we investigated the genotoxic and cytotoxic effects of water samples on Gambussia affinis in vivo using the piscine micronucleus (MN) test. Fish were exposed to 50, 100, 150 and 300 mL L-1 of water samples for 24 hrs, and MN, nuclear abnormalities (NA), polychromatic-normachromatic erythrocytes (PCEs/NCEs), and apoptotic erythrocytes were evaluated. In addition, water samples were analysed to determine the concentrations of the heavy metals. The results showed that MN, NA, and apoptosis frequencies significantly increase at all concentrations compared to the control. A significant correlation was found between genotoxicity endpoints and the concentration of water samples. The PCE-NCE ratio was significantly decreased at all treatments. The metal content of river water was not associated with the increase in the seasonal frequency of genotoxicity endpoints. The results indicated that the Ergene River has genotoxic and cytotoxic effects on erythrocytes of G. affinis in an in-vivo piscine MN test that could be due to organic and inorganic effluents.

Application of the immunostimulant is the most promising method for controlling diseases in aquaculture. In this study, the mortality rate and immune responses of rainbow trout (Oncorhynchus mykiss) fed on diet supplemented with Ducrosia anethifolia essential oil was investigated after challenging with Yersinia ruckeri. The essential oil mixed with sunflower oil at different concentrations (0.001, 0.01 and 0.1%) and the commercial food was coated with this oil. Fish were fed with diets for 8 weeks and infected with Y. ruckeri at the ending of feeding trial. Serum protein, albumin, globulin and lysozyme and bactericidal activity of challenged fish were evaluated one week after injection and mortality were counted till day 10. The results showed that albumin had not differed among treatments. The highest level of the protein and globulin were found in control group. Serum lysozyme activity showed no difference between groups. The highest and lowest serum bactericidal activity was observed in 0.001% and control group, respectively. The mortality rates in infected fish were as 55% in control group, 40% in 0.001%, 70% in 0.01% and 70% in 0.1% treatment. Lowest rate of mortality was observed in group 0.001%, while began two days earlier than other groups.

The research was carried out to enlist the fish species diversity along with diversity indices of existing fish species of Chalan Beel, Bangladesh. During the study, a total of 78 fish species including 69 native and 9 exotic fish species were recorded belonging 10 orders and 26 families. The values of Shannon-Weiner diversity index (H') indicated a good spread of fish population in Chalan Beel although the number of species was not found satisfactory. The degradation of water quality due to domestic discharges, jute rotting, excessive usage of agro-chemicals, indiscriminate fishing activity etc. were revealed as the causes of declining the fish diversity of this Beel. The Margalef’s richness index (d) expressed the species richness of Chalan Beel that started in July by joining new fish population with the existing fish species and reached gradually highest in November after breeding. Pielou’s index (J) showed the equal distribution pattern of fish species throughout the sampling area indicating a stable but incompatible habitat for existing fish species. The assessment of the study revealed the number of species was not found in expected level in view of the overall fish biodiversity of the country. Considering the observations, it is recommended for stopping water pollution, ensuring normal water flow and developing awareness of fishermen to retrieve the fish diversity of the study area. Besides, an inclusive management and conservation scheme is crying need for the Beel fishery to enrich the fish species diversity of the Chalan Beel as well as the country.

In the present study, rainbow trout weighting 3±0.3 g were vaccinated with an oral DNA vaccine encoding VP2 gene of a prevalent isolate of IPNV in Iranian trout farms encapsulated in sodium alginate microspheres and Chitosan tripolyphosphate (CS/TPP) nanoparticles. The vaccinated fish were then challenged with a virulent isolate of IPNV at 30 days post-vaccination. The transcriptional changes of adaptive- immune genes (IgM and IgT), as well as the VP4 gene of IPNV, as an indicators of viral replication were studied 45 days post-challenge. Analysis of RT-qPCR data showed lower levels of VP4 gene expression in the oral DNA vaccinated trout after IPNV challenge compared with the control one. Moreover, the constructed DNA vaccine did not enhance the expression of IgM and IgT genes above the levels observed in the carrier control group but it showed a mimic of viral activity and contributes to maintaining them at appreciable levels in vaccinated group.