Hilsa (Tenualosa ilisha) is one of the flagship diadromous fish species of Bangladesh that migrate only through the Ganges-Meghna river system route. The biological profile of plankton from the Padma, Meghna and Tetulia reference river sites during 2011 spawning season of hilsa showed that in total of 58 taxa of plankton were present. Of which, 19 taxa (32.76%) were of phytoplankton and 39 taxa (67.24%) of zooplankton. Phytoplankton group belonged to Cyanophyceae (6 taxa), Chlorophyceae (7 taxa) and Bacillariophyceae (6 taxa) while zooplankton including Protozoa (10 taxa), Rotifera (19 taxa), Copepoda (4 taxa), Cladocera (5 taxa) and Ostracoda (1 taxon). The average abundance of plankton was recorded as 194.05 ± 82.58 indiv/l. The highest abundance of total plankton (692 indiv/l) was observed in Godagari, Rajshahi (Station 3) and was lowest (4.00 indiv/l) in Charghat, Rajshahi (Station 2). The highest abundance (49 indiv/l) of total zooplankton was observed in Godagari and lowest (1 indiv/l) in Charghat with mean value of 19.46 ± 4.12 indiv/l. The highest species richness (SR = 45) was observed in Daulotkhan, Vhola (Station 9) and the lowest (SR = 3) in Charghat (Station 2), with mean value of 17.10±4.408. Shannon-Weiner species diversity index (Hʹ) ranged from 3.334 in Daulotkhan (Station 9) to 1.5 in Charghat, (Station 2) with mean value of 2.717 ± 0.147. Based on the plankton profile it may be concluded that the biological quality of hilsa migratory river was not alike throughout the route which may restrict the migration up to up steam and spontaneous spawning of hilsa.
Aim Freshwater planarians may have a wide geographical range despite their assumed low vagility. Found across four continents, Dugesia may have either an ancient origin on a large palaeo landmass, followed by colonisation in different regions before continental fragmentation, or a more recent origin and subsequent transoceanic dispersal. We seek to resolve between these two hypotheses. Location Africa, Eurasia and Australasia. Taxon Genus Dugesia (Platyhelminthes: Tricladida: Dugesiidae). Methods We used data from the sequencing of six gene fragments and comprehensive taxonomic sampling of Dugesia from across its distribution range to reconstruct the phylogeny of this genus using maximum likelihood and bayesian inference methods. We conducted two phylogenetic dating analyses using Platyhelminthes fossils and palaeogeological events. Basing on the time‐calibrated molecular phylogenetic framework we evaluated the contribution of vicariance and dispersal to the biogeographical evolution of Dugesia. By reconstructing the ancestral areas and present‐day potential distribution using BioGeoBEARS and niche modelling, we elucidated the biogeographical history of the genus. Results The present‐day distribution of Dugesia is a result of different vicariance and dispersal events. However, we also found evidence of transoceanic dispersal. Consistent with previous hypotheses, Dugesia dates to the Upper Jurassic in the Afro‐Malagasy Gondwana region. We unveiled a novel biogeographical scenario for the genus, involving multiple events of colonisation in Eurasia from continental Africa via at least three dispersal routes. Main conclusions Dugesia is an ancient genus having reached its present distribution through a complex history of dispersal and vicariant events following its origin in southern Gondwana. Despite the low vagility of Dugesia, we found evidence of their overseas dispersal.
not available Bangladesh J. Zool. 49(1): 01-02, 2021
This study was conducted to compare mollusc diversity in migratory bird visiting and non-visiting lakes of Jahangirnagar University campus, Savar, Bangladesh from July, 2016 to June, 2017. A total of 13 species belonging to 6 families under 2 classes of Mollusca were encountered. The class Gastropoda dominated the faunal composition (91%) with 11 species under 5 families and the class Bivalvia constituting (9%) with 2 species under single family. Among them Bellamya bengalensis, Lymnaea accuminata, Indoplnorbis exeutus, Gyraulus convexiusculus, Melanoides tuberculata and Lamellidens marginalis were the most dominating taxa. The highest number of molluscan taxa was from the family Viviparidae (3 spp.) 29% followed by Planorbidae (2 spp.) 27%, Lymnaedae (3 spp.) 23%, Unionidae (2 spp.) 9%, Thiaridae (1 sp.) 8% and lowest from Piladae (2 spp.) 4%. Seasonal variation showed maximum density in the summer and minimum in the monsoon. Correlation (p> 0.05) indicate that B. bengalensis, L. accuminata, I. exustus, L. marginalis had close dependency to soil pH, soil organic Carbon, Soil organic matter and sand particle whereas M. tuberculata and G. convexiusculus show significant positive correlation with silt and clay particle. Biodiversity indices indicating low species diversity and richness of molluscs in both migratory bird visiting and non-visiting lakes. These findings emphasized the importance of protection and management of molluscs fauna in the lakes for supporting the food for the migratory birds. Bangladesh J. Zool. 47(2): 355-366, 2019
not available Bangladesh J. Zool. 49 (2): 187, 2021
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