PRELIMINARY CYTOGENETIC STUDIES of Parachanna Obscura OBTAINED from EGBE RESERVOIR, EGBE EKITI

Asian Journal of Advances in Research

5(1): 1-5, 2020

PRELIMINARY CYTOGENETIC STUDIES OF Parachanna obscura OBTAINED FROM EGBE RESERVOIR, EGBE EKITI

F. A. OLA-OLADIMEJI1*, O. V. EKUNDARE2 AND A. V. AYODELE1 1Department of Zoology and Environmental Biology, Faculty of Science, Ekiti State University, P.M.B. 5363, Ado-Ekiti, Nigeria. 2Department of Biology, Osun State College of Education, Ilesa, Nigeria.

AUTHORS’ CONTRIBUTIONS This work was carried out in collaboration among all authors. Author FAO designed the study, managed the literature searches and wrote the final manuscript. Author VOE carried out laboratory procedure and proof read the first draft of the manuscript. Author AVA assisted in the experiment and wrote the first draft. All authors read and approved the final manuscript.

Received: 24 June 2020 Accepted: 29 August 2020 Published: 07 September 2020 Original Research Article

ABSTRACT

Parachanna obscura belongs to the Family Channidae and are commonly found in Asia and Africa. This preliminary research was carried out to assess and provide information on the chromosome number and morphology of P. obscura using standard procedures. The modal diploid chromosome number of 2n = 44 was observed in this study. The study further showed that the chromosome types for the studied fish consisted of 10 metacentric, 12 submetacentric, 20 acrocentric and 2 telocentric chromosomes with 'Nombre Fondamental' (NF) of 68. The present study provides a piece of baseline information on the karyotype of this important species of fish which can help in further studies regarding its production in a controlled environment for its sustainability.

Keywords: Parachanna obscura; preliminary; chromosome; morphology; Nombre Fundamental.

1. INTRODUCTION not so popular since the most common culture species are Tilapia spp. and Clarias spp. [4-5]. However, Parachanna obscura, the African obscure snakehead, cases of extensive farming have been reported from is an aquatic organism of the Family Channidae that Nigeria, Cameroon, Gabon and Democratic Republic lives in freshwater. Members of this family are not of Congo, Ivory Coast [3]. The healing importance of very much globally distributed; they are mostly found African snakehead culture has been known by the in Asia and Africa [1-2]. Parachanna obscura and Asians, particularly, in China, Thailand, India, Parachanna africana are the two available species in Vietnam, and Malaysia. The presence of Arachidonic West Africa (Sydenham). [3] described it as a Acid (AA), a polyunsaturated omega-6 fatty acid [6] freshwater fish characterised by an elongated, makes the meat of African snakehead fish of high fusiform, sub-cylindrical body covered with cycloid pharmaceutical importance. scales of medium size and they also have a protractile mouth. They are carnivorous and so feed on any form Cytogenetic studies have been conducted on other fish of meat they can easily obtain with juveniles known species primarily to improve the production of their to feed on small meat and adults on larger ones. In hybrids. With this species being one of the least tropical Africa, the culture of Parachanna obscura is studied fish in Nigeria, the knowledge of their ______

*Corresponding author: Email: [email protected];

Ola-Oladimeji et al.; AJOAIR, 5(1): 1-5, 2020

karyotype is uncertain. The knowledge of replicated chromosomes from migrating to their chromosomes provides very useful information to respective poles [10]. Another 100ml of distilled clarify species status, to identify loci of interest in water was measured into a beaker followed by the aquaculture and to provide useful information for addition of 0.56g of KCl which was mixed with the conservation programs and sustainable exploitation distilled water. After three hours, the tubes to use [7]. were cleaned with distilled water and the fish samples were sacrificed by decapitation and dissected. The In Africa, no information exists on the kidneys were deposited into KCl for 45 minutes, after cytogenetic studies of Parachanna obscura. which it was macerated with mortar and pestle to However, studies on this species have focused on homogenize the solution and the tissue using the their proximate analysis [8], biology, [9] and length- modified method of [11]. The supernatants were weight relationship [3]. Therefore it is necessary to removed by pouring it into centrifuge tubes, the tubes obtain information on this species on P. obscura in were centrifuged for 7 minutes at 1000 rpm, then the order to develop its cultivation. However, supernatants were removed. 3:1 methanol and acetic the culture of snakehead without understanding its acid were mixed and 6ml of the mixture was used for chromosome number can create more problems when fixation and then centrifuged for 7 minutes at 1000 culturing. rpm. After the supernatant was removed, refixation was carried three times using the above method. Cells 2. MATERIALS AND METHODS from the fixatives were transferred to clean and pre- warmed slides using Pasteur pipette. The slides were 2.1 Collection of Specimen allowed to dry for 24 hours and stained with Giemsa stain solution for 20-25 minutes. Finally, the slides A total of 75 specimens of Parachanna obscura were were rinsed with distilled water and dried. Slides were collected from Egbe reservoir at Egbe Ekiti. They covered, viewed under a binocular microscope and were harvested with available fishing gears which are well-separated metaphase chromosomes were cast nets and transported to Zoology and photographed. A karyogram was prepared by 18 high- Environmental Biology Laboratory in Ekiti State contrast chromosome photographs and the individual University, Ado Ekiti for their measurements. The chromosomes were cut out of the photographs. samples were identified by experts in fisheries in the Classification and karyogram of the chromosomes department. Then, the length and weight of the fish were performed according to the techniques described were done with metre rule and weighing balance by [12]. The final karyogram was then scanned and respectively. printed.

2.2 Chromosome Preparation 3. RESULTS AND DISCUSSION

100ml of distilled water was measured into a conical 3.1 Chromosomal Analysis flask, using an electronic weighing machine. Then, 0.05g of colchicine was measured and mixed with Most of the chromosomes seen was very small in size. 100ml of the distilled water. 1.5ml of the solution was The modal diploid chromosome numbers were 44 injected intraperitoneally into the fish samples to (2n=22) which consisted of 10m+12sm+20a+2t disrupt spindle formation at mitosis and prevent the (Fig. 1).

Plate 1. Mitotic metaphase (x 1000) chromosomes of P. obscura

Ola-Oladimeji et al.; AJOAIR, 5(1): 1-5, 2020

Metacentric = 10 Sub-metacentric = 12 Acrocentric = 20 Telocentric = 2

Fig. 1. Chromosome arrangement of Parachanna obscura

Studies on fish chromosomes are still scarce in different geographical regions to confirm its diploid comparison with other vertebrates [13]. Some fish number. However, with the present information on the groups share a common karyotype structure and an chromosome structure and number of this species equal number of chromosomes [14-16]. However, living in Egbe reservoir, additional data is provided some species of catfish (Siluriformes) show a great for the fish database. diversity in the organization of the genome; this includes the karyotype as well as the amount of DNA COMPETING INTERESTS included in each nucleus [17]. Data for many important fish groups are still lacking in fish lists Authors have declared that no competing interests [18].In the last two decades, large amounts of data exist. were generated concerning the chromosomal mapping of several fish species [19], however, cytogenetic data REFERENCES of P. obscura is yet to be available therefore restricting the means of understanding the 1. Qin J, AW Fast. Food selection and growth of evolutionary trends associated with this species. young Snakehead Channa striatus. J. Appl. Cytogenetic studies are essential in providing basic Ichthyol. 1997; (13):21-25. information on fish breeding programs such as 2. Ali AB. Aspects of the reproductive biology of chromosome manipulation techniques [20]. In female snakehead (Channa striata Bloch) addition, the analysis of chromosomes is important for obtained from irrigated rice agroecosystem, genetic control, taxonomy and evolutionary studies Malaysia. Hydrobiologia. 1999;411:71-77. [21-24] and is widely used in various fish 3. Olanrewaju AN, Ajani EK, Kareem OK, investigations [25]. Analyses of fish cytogenetics Orisasona O. Relationship Between Physico- have provided information on the number and Chemical Parameters and Reproductive Indices morphology of their chromosomes [26] and sex of Parachanna obscura (Gunther 1861) in chromosomes [27-28]. According to [29], six species Eleyele Reservoir, Ibadan, Nigeria. Eur Exp of the Channid fish had been studied in Thailand, each Biol. 2017;7(6):36. having a different diploid chromosome number: 4. De Lapeyre BA, Muller-Belecke A, Horstgen- Channa striata, 2n = 44 [30], Channa marulius, 2n = Sehwark G. Increased spawning activity of 44, Channa micropeltes, 2n = 44, Channa lucius, 2n = female Nile tilapia (Oreochromis niloticus) (L.) 48 and Channa gachua, 2n = 112 [30]. [29] stressed after stocking density and photoperiod further about the differences between the manipulation. Aquacult. Res. 2010;41(10):561- chromosomes of some of the above species and 567. similar ones in India and Bangladesh which were 5. Ibrahim N, Nagar G.E. Water quality, fish Channa marulius, 2n = 40 and Channa gachua, 2n = production and economics of Nile tilapia, 78 [31-33]. Oreochromis niloticus and African catfish, Clarias gariepinus, monoculture and 4. CONCLUSION polyculture. J. World Aquacult. Soc. This present study of the chromosome study of P. 2010;41(4):574-582. obscura is preliminary;hence, a future investigation 6. Mat Jais AM, McCullock R, Croft K. Fatty should be made using larger populations from acid and amino acid composition in Haruan as

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