1 Introduction

With the presence of skeletal deformities that the fish may have during their early life history, a natural development of different parts of the fish cannot be attained. In turn, such anomalies can affect the morphology, growth and survival of the fish (Bogutskaya et al., 2011). In the wild, such deformities are relatively rare (Gavaia et al., 2009) and some abnormalities are considered so severe that they affect the fitness of the fishes, while others may be slight and not critical to survival (Ershov, 2008).

The Indian catfish, H. fossilis, is found throughout south and Southeast Asian countries including Bangladesh, India, Laos, Myanmar, Nepal, Pakistan, Sri Lanka and Thailand (Talwar and Jhingran, 1991). In some parts of the world, i.e., Iraq, it has been introduced in an aim to control of the snail Bulinus truncatus, the vector for the human parasite causing schistosomiasis (Jawad, 2015), but which proved to be ineffectual (Jawad, 2003).

Detecting skeletal deformities in fishes are important from the point of view of monitoring the environment. Skeletal abnormalities in H. fossilis were reported from individuals subjected to cold shock to induce triploidy (Tiwary and Ray, 2004). Other than this report, there is no information on record about the skeletal deformities in H. fossilis. Therefore, the present study is considered the first to document the description of dorsal fin anomaly in the Indian catfish collected from Ganges River, India.

2 Materials and Methods

During the osteological study on specimens of H. fossilis using radiographs of specimens deposited at the ichthyological collection of The Academy of Natural Sciences of Drexel University, Philadelphia, one specimen with catalogue no. ANSP 178663 has shown multiple skeletal deformities. Although the specimen was obtained from aquarium shop at Bangkok, it was originally collected from the Ganges River, India. The specimen was obtained by M.H. Sabaj and M. Hardman on 2^nd February 2001. The normal and abnormal fish specimens were 123 and 137 mm in total length (TL) respectively. Radiograph of a normal specimen (ANSP 123097) was obtained to determine the extent of the deformity. Radiographs were used to describe the skeletal deformities. In the process, the parts of the vertebrae were described in details.

3 Results

In the abnormal specimen of H. fossilis, there are 44 caudal vertebrae (Figure 1a; b). In those vertebrae, there are two locations of deformities observed. The 1st location involve the neural spines of the 4^th – 9^th caudal vertebrae and the 2^nd location involves the neural and haemal spines of the 36^th – 44^th caudal vertebrae. The middle of the neural spine of the 4^th – 9^th caudal vertebrae shown to have an abnormal ossification, where an irregular bony lump is present. Those of the 4^th and 5^th vertebrae have different shape from those of the 6^th – 9^th vertebrae. In the later 4 neural spines, the lump takes the spherical shape. In the neural spines of the 4^th and 5^th caudal vertebrae, the ossification is irregular and covers large area, with the neural spine of the 4^th vertebra being curved backward and that of the 5^th vertebra appeared as two parts joined irregularly (Figure 1a).

The 2^nd location of the abnormality appeared in the radiograph of the abnormal specimen is related to the neural and haemal spines of the 36^th – 44^th caudal vertebrae. These spines shown to be wavy instead of being straight as in the normal case (Figure 2b). The state of waviness in the neural and haemal spines of the posterior caudal vertebrae is more severe than those of the anterior caudal vertebrae. In the caudal vertebrae 38^th – 44^th, the neural and haemal spines are wavy from their base near the centrum to the tip of the spine near the dorsal side of the fish body.

4 Discussions

In the present deformed specimen, the anomalies represent a deformed neural and haemal spines of a number of caudal vertebrae. The abnormal calcification in the 1^st location of deformity can be as a result of disorganized and proliferating cells at the growth zones. Similar case was observed in the vertebrae of fishes by Ytteborg et al. (2012). On the other hand, Cockroft (1978) and Miura et al. (2004) have given examples, based on several mammalian cases, on the changes in the balance between cell death and cell proliferation may lead to malformations. In the growth process of the bony elements, increased growth of osteoblasts at the development zones is partly stabilized by increased cell death (Ytteborg et al., 2012). In the present case of abnormal calcification can be due to destabilization in the cell death.

It might be possible that the deformed specimen of H. fossilis has faced an unfavourable environmental factors that might cause this type of skeletal abnormality. Since this specimens is an adult, then the deformation in was not fatal, but it certainly affected the mobility in some way.

The wavy neural and haemal spines of posterior caudal vertebrae could be as a result of an adverse environmental factors (Jawad et al., 2014; 2015). Among these unfavourable environmental factors is the pollution with heavy metals, which approved to be one of the main agents in developing fish malformation (Chatain, 1994; Gavaia et al., 2009). The Ganges River passing through heavily populated settlements as with the case of the large rivers of the world. As a result, the water of this river became heavily polluted by different types of pollutants including heavy metals (Kannan, et al., 1993; Singh, 2001; Singh et al., 2005).

Lack of certain nutritional component such as phospholipids might be considered a possible cause for the skeletal deformities in H. fossilis. Kanazawa et al. (1981) showed that phospholipids reduced skeletal deformities in larvae of Plecoglossus altivelis and phosphatidy linositol reduced spinal malformations in larval D. labrax (Cahu et al., 2003). On the other hand, excess of phospholipids induced severe skeletal malformations in larval D. labrax (Villeneuve et al., 2005).

The mechanical factors in producing such anomalies cannot be excluded. Hilomen-Garcia (1997) has studied the fish larvae in the rearing tanks and the mechanical injuries they usually face. Koumoundouros (2010) has suggested that the mechanical load can cause lordosis in the vertebral column of the fish. Finally, Boglione et al. (2013) have mentioned the mechanical factors in causing skeletal deformities in different European fish species.

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