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Squamatological Variations in Five Inland Fishes of Bangladesh

MD. ASHRAFUL ISLAM
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

JOBAYDA SIFAT
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

H.M. AL KABID RAFIN
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

MOSTAFA ALI REZA HOSSAIN
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Fish scales have numerous hidden information in their structures that contribute in fish identification and classification. In the present study, scales were collected and examined from twelve body regions including lateral line of five fish species belonging to five Families and five Orders of inland fishes of Bangladesh. A wide spectrum of variations in the scales of five fish was recorded concerning the surface morphology, shape of the circuli, grooves, pattern of the different fields and the shape of ctenii. The morphological descriptions were based on the scale’s type, shape, features of the anterior, posterior and lateral fields, radii types, and circuli distribution. The microstructures included focus position and shape, shape of first circuli, number of radii and tubercle size and shape. Results of the study reveals that scales of the studied fishes were either cycloid or ctenoid types with notable variation in scale shape, circuli distribution, focus position and shape, shape of first circuli, radii types and tubercle size and shape. Considerable variation in lateral line scales were also observed and two types of lateral line scales observed with three sub-types. Morphometric indices were calculated from scale of the anterior dorsal flank area of each species and represented a valuable tool for species separation. The outcomes of the present study, first of its kind in Bangladesh, would assist in resolving identification problems for future fish taxonomists and fisheries-oriented researchers.

Keywords: Keywords: Scales, Morphology, Microstructure, Lateral line, Inland fish

Location: The local markets of Mohonganj, Netrokona, Mymensingh Sadar, Mymensingh district and Khulna Sadar, Khulna district, Bangladesh

Start Date:

End Date:

Program Area: Conservation and Biodiversity

Commodity: Fish

Objectives:

To screening and documenting the diversity of scale characteristics of five indigenous fish from the water bodies of Bangladesh in an attempt to determine the valid scale characters for identification of the studied species and to give an interpretation for the surface scale morphology. Also the study has been designed to describe the microstructures of the studied scales, inter-specific variability of scale shapes, and to describe the lateral line scales, present in the five fish.

Methodology:

Collection sites and selected fish: Fish sample were collected from the local markets of Mohonganj, Netrokona, Mymensingh Sadar and Khulna Sadar, respectively. Scales were sampled from 5 fish Species, belonging to 5 Families and 5 Orders of common inland fishes in Bangladesh. Preparation of scales: Before removing the scale, every single fish specimen was rinsed out with freshwater. Scales were taken from twelve areas of the selected fish. Maximum effort were given to remove as much tissue as possible while taking fish scales using forceps without damaging the scales. In case of some species, it was not possible to take scales from each of the selected twelve body areas as sufficient number of scales were not present. Scale materials were sonicated in 70% ethanol and brushed gently to remove the reaming tissue and staining was done using 0.05% Alizarin Red S solution for 45 minutes. Before mounting, the scales were kept in absolute ethanol after that on distilled water for 15 minutes to avoid curling. When scales became flexible, they mounted between the glass slides. For ensuring the moistness of scales, care was taken to impede curling. Photography of preserved fish scale: Microphotography digital imaging was performed using Delta IPOS-810 Stereo Zoom-Microscope (Budapest Telescope Centre, Budapest, Hungary) and Amscope microscope digital camera (Amscope USA) at lower magnification. For describing the microstructure of scales, Micros-Austria, Daffodil MCX100 Binocular Microscope (Micros, Austria) was used. Appropriate scale bars were added digitally using imaging software (Image J). Digital imageries were rendered on a computer using Adobe Photoshop CC 2015. Scale types and characteristics: The scales are defined following Roberts (1993) with some modifications and differentiated two main scale types as follows – i. Cycloid scales- no additional isolated ossifications, marginal indentations might happen. Two sub- types - scale without spine-like projections or marginal increments is known as true cycloid and scale with increased marginal site is termed as crenate scale. ii. Ctenoid scale – with additional isolate ossification forming distinct spines known as cteni. The isolate ossifications ascend as complete spines in two or more alternating row marginally. When isolate ossifications transmute into truncated spines sub-marginally, the cteni is known as transforming cteni. Scale characteristics that are used in this study are defined by Lagler (1947) and maintained uniformness of benchmarks used in preceding works by other researchers (Patterson et al. 2002, Brager and Moritz 2016, Gholami et al. 2013) are given. Scale shape, morphometric and microstructures: Scales show a high level of diversity in their shapes with considerable inter and intra-specific variation. Shape variability of fish scales are described in accordance with the number of different scale shapes that found within a specimen: uniform – 1 scale shape; low – 2 scale shapes; moderate – 3 scale shapes; high – 4 or more scale shapes. Different morphometric and microstructure characters and discriminative features of a scale are the important tools that measure inter and intra-specific variation of specimens. Morphometric structures of scales in our study included scale type, shape, field, cteni, circuli etc. while microstructure deals with shape of first circuli, focus position, tubercles and radii. The discriminative features of the morphometric structures of scalesare given.

Source of Information: Bangladesh J. Fish. (2019) 31(1) : 01-16

Article Link (Online Journal):

Funding Source:

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Achievement/Findings:

General shape, size and architectural specifications such as focus, circuli, radii, tubercles, cteni and so on of the fish scales - observed using microscopy have long been effectively used as versatile research material in various ichthyological researches such asphylogeny, sexual dimorphism, past environment experienced by fish, discrimination between hatchery-reared and wild populations, determined times of migration, periods of food scarcity, illness, the pathology of a fish scale due to water pollution, growth studies and pollution status of the ecosystems of which fishes are a part (Esmaeili et al. 2012). The results of the present work revealed that the characters of the scales of the five indigenous fishes exhibited species-specific valuable taxonomic characters and indicated that such scale characters are fixed and stable. The present analysis of the scale morphology of five fish may be used in combination with other morphological and molecular data in a synergic approach to the phylogenetic and systematic study of the fishes of Bangladesh.

Knowledge Management: Journal