International Journal of Marine Science, 2017, Vol.7, No.4, 31-36
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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.
