Albinism results from a hereditary lack of pigmentation. This is caused by a disorder in an enzyme that control melanin metabolism (Kinnear et al., 1985). Forms of albinism can be: complete or total albinism, which is due to a lack of skin pigmentation; incomplete, where parts of the fish body lack melanin pigment; imperfect, which is recognized by reduced or light pigmentation in the skin and partial albinism or leucism resulting from reduced or absence of pigmentation from localized portions of the skin (Berdeen and Otis, 2011). Complete albinism is phenotypically known as a lack of integumentary and retinal melanin, indicating defects in the integumentary and retinal melanophores. Both total and partial albinism have been previously reported for several species of teleost fishes (Shinohara and Amaoka, 1993; Delgado et al., 2009; Mansur, 2011; Pillai and Somvanshi, 2011), as well as among chondrichthyans (Ishihara et al., 2001; Bottaro et al., 2005; Sandoval-Castillo et al., 2006; Reum et al., 2008; Veena et al., 2011; Bigman et al., 2015). When patches of reduced pigmentation are found distributed among normal pigmentation, this case is known as leucism (Ebert, 1985; Bechtel, 1995; Acevedo et al., 2009).

Fin anomalies in wild and reared fish are well documented in literature (Divanach et al., 1996), but those of the dorsal fin are not adequately reported (Hussain, 1979). Dorsal fin anomalies are usually involved in the saddleback syndrome (Sfakianakis et al., 2003; Al-Mamry et al., 2010; Jawad and AL-Mamry, 2012). Due to the unfavourable environmental conditions, different levels of skeletal deformities occur during the developmental period of the fish (Bengtsson, 1988; Lemly, 1993; Sfakianakis et al., 2004; 2006). Therefore, skeletal deformities are believed to be important markers of environmentally induced stress of fish in the wild (Bengtsson, 1988; Lemly, 1993; Boglione et al., 2006; Koumoundouros, 2008).

Both albinism and dorsal fin deformity cases have not been previously recorded from the Saudi waters of the Arabian Gulf. Here, we report the first record of albinism in Epinephelus areolatus (Family: Epinephelidae) and the dorsal fin anomaly in Argyrops spinifer (Family: Sparidae) from the vicinity of Jubail City, Saudi Arabia, Arabian Gulf coast.

1 Materials and Methods

One specimen with abnormal coloration of E. areolatus (TL 410 mm) and one specimen with deformed dorsal fin of A. spinifer (TL 450 mm) were captured on 20th February 2013 in the waters of Jubail City Saudi Arabia. The specimens were collected by local fishermen using drifting gill net. One specimens with normal coloration and one specimen with normal dorsal fin from the same fishing lot at the same fishing locality to make a comparison were obtained. Body and fins were examined carefully for external parasites, malformations, amputations and any other morphological anomalies. The specimens were deposited in the fish collection of the Fish Welfare Branch, Jubail, Saudi Arabia. Once in the laboratory, measurements were recorded to the nearest millimetre.

2 Results

Albinism case was observed in the species of E. areolatus. The description of the aberrant specimen in this species studied is given below based on the case of albinism.

Class: Actinopterygii

Family: Epinephelidae

Epinephelus areolatus (Forsskal, 1775)

Colour of normal specimen (TL 415 mm), Number of specimen = 1 (Figure 1):

Body and head with general pale-green to yellow coloration. Round dark spots distributed all over the body, head and fins, getting smaller toward the mouth. Large spots at the base of the spinous part of the dorsal fin.

Colour of abnormal specimens

Number of Specimen = 1 (TL, 410 mm) (Figure 2):

The whole body appeared lacking any coloration. A trace of the rounded- dark spots appear on the body, head and dorsal fin. The remaining fins appear to have lost their dark spots.

Dorsal fin anomaly case was observed in the species of A. spinifer. The description of the deformed specimen in this species is given below.

Family: Sparidae

Argyrops spinifer

Shape of the dorsal fin of the normal specimen (TL 470 mm) (Figure 3):

The spinous part of the dorsal fin with two types of spines of different length. The anterior 4 spines are the longest. The length of the spines reduced dramatically at the 5th spine and increased gradually toward the soft part of the fin. The length of the rays in the soft ray part is nearly the same and the general shape of this part take the curved contour of the fish body.

Shape of the dorsal fin of the abnormal specimens (TL, 460 mm) (Figure 4):

The spinous part and the anterior part of the dorsal fin look normal. The posterior 3-4 fin rays appeared severely deformed and joined together. In the dorsal edge of the fish body, it appears like the underneath supporting pterygiophores have been lost and the contour of this area is lower than that under the normal part of the dorsal fin. In addition to the dorsal fin anomaly observed, the lateral line below the deformed soft rays was shown to be anomalous and 7-8 lateral line scales appeared raised upward. The remaining parts anterior and posterior to the deformed area of lateral line were shown to be normal.

3 Discussion

Fish body coloration is an interesting field of study, but it is far away from being fully understood from the genetic point of view (Oliveira and Foresti, 1996). Albinism is a genetic disorder generated in conjunction with environmental factors such as the exposure during the early life history to high concentrations of trace metals such as arsenic, cadmium, copper, mercury, selenium and zinc (Oliveira and Foresti, 1996) as these metals have the ability to create a genetic random alteration (Wakida-Kusunoki and Amador-del-Ángel, 2013). In such genetic alteration, an autosomal recessive gene, when in homozygous state, produces a phenotype known as albino. This phenotype is diagnosed by the lack of melanin pigmentations. Albinism can be inherited if the alleles are autosomal and recessive, autosomal and dominant, or sex-linked (Purdom, 1993). The probability of the trace metals as the cause for albinism in our specimen looks possible as the Arabian Gulf waters of Saudi Arabia has been shown to have high levels of trace metals due to the oil spillage from the large number of the giant oil tankers that navigate this water way (Al-Saleh and Shinwari, 2002; Pourang et al., 2005; Al-Homaidan, 2007).

Unlike the nocturnal fishes, where albinism has a little effect, the diurnal fish individuals with albinism case could face high risk of predation due to being conspicuous to predators (Sazima and Pombal, 1986). By contrast, it seems that albinism may have less influence in feeding, growth and other aspects of life, such reproduction (Joseph, 1961). Due to the considerable size of the albino specimen obtained in the present, our result agrees with Joseph (1961). Sandoval-Castillo et al. (2006) permits us to postulate that, despite being an albino phenotype which makes an individual more visible to predators, albinism makes little impact on aspects of growth and performance of these specimens. Such assumption has also been applied to cases of albino sharks collected by Lipej et al. (2011). This is the first report of albinism in the species E. areolatus from the Arabian Gulf area in general and the Saudi Arabian waters in particular. The areolate grouper is a species of high commercial value and subject to fishing activities with a high number of individuals being captured for decades from the Arabian Gulf area with no previous record of albinism. This, then, is a rare event still unnoticed in most wild fish species, at least regarding adult individuals.

Dorsal fin plays an important role in fish locomotion activity and stability (Drucker and Lauder, 2005; Standen and Lauder, 2005); therefore it must be structured so as to handle the hydrodynamic stresses with the least possible disbursement of energy (Boglione et al., 1993). Any anomaly in the dorsal fin will weaken its flexibility, so impeding the performance of the fish. The dorsal fin deformity can be a result of the combination of genome, environment and developmental noise (Scheiner, 1993). It is clear that varieties in the genetic pool can control variations in the developmental pattern. Developmental aberration is a factor which can theoretically induce phenotype differences in genetically identical individuals developing in identical environments (Divanach et al., 1996). In this regard, Soulè (1982) argues that an expansion of the phenotypic variability is a characteristic of biologic systems subjected to stress (like intensive rearing conditions, for instance) and that developmental noise discloses itself as a decrease of the intracellular order. The second factor, the environment, which involve the impacts exerted by external conditions, such as biotic and abiotic conditions (Divanach et al., 1996).

Skeletal anomalies can be prompted during embryonic and postembryonic stages of the life of the fish through a complicated mechanism (Koumoundouros et al., 1995; Cataudella et al., 1996). In the present case of dorsal fin aberration in the soldierbream A. spinifer, without additional data it is impossible to support the biotic and abiotic hypotheses in causing such anomalies. Effects of an abiotic factor such as heavy metals in producing fin anomalies was demonstrated by Sloof (1982). Photo and thermo-period induction of reproduction might cause complete or partial absence of the caudal complex (Koo and Johnston, 1978) and vitamin C deficiency has been related to the fin degeneration in fishes. Among the biotic factors is the expected physical attack during the juvenile stage from aquatic organisms (Dulčíc and Soldo, 2005). Without additional data, it is impossible to support the biotic and abiotic hypotheses in causing the dorsal fin deformity. Therefore, further research and studies are needed to locate the prime cause of such anomaly. The presence of dorsal fin deformity in A. spinifer (in spite of being among the high commercially valued fish species in the Arabian Gulf area, large number of specimens have been landed and targeted by fishing fleets in the area for years) is considered a rare incidence worth the attention of the fisheries managers.

Authors’ contributions

Both authors were contributed equally to produce this manuscript.

Acknowledgments

We would like to thank the Ministry of Agriculture, Fish Welfare Branch, Jubail Province, Saudi Arabia for giving us the opportunity to examine and study the deformed fish specimens. Our thanks are also due to Sergey Bogorodsky of Station of Naturalists, Omsk, Russia and Ronald Fricke of Staatliches Museum für Naturkunde, Rosenstein, Germany, for identification of the species.

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