Biochemical Composition of the Eggs of Commercially Important Crab Portunus pelagicus (Linnaeus)
Rajnish Kumar Singh
In the present investigation an attempt has been made
to know the biochemical composition of matured eggs of P. pelagicus.
The protein content was found to be 57.00% followed by lipid (14%) and
carbohydrate (6.40%). The total values of saturated fatty acids in crab
eggs were calculated as 12.78%. Among various saturated fatty acids recorded,
the amount of myristic acid (06.36%) was predominant and minimum was capric
acid (00.14%). The total amount of monounsaturated fatty acids in the
present study was found to be 02.97%. Higher amount of monounsaturated
fatty acid was nervonic acid (02.44%) and less amount of fatty acid was
palmitoleic acid (00.10%). The total amount of polyunsaturated fatty acids
in the present observation was calculated as 12.66%. Maximum amount of
fatty acid was reported to be arachidonic acid (07.77%) followed by linoleum
acid (01.83%) and minimum was linlelaidic acid (00.02%). From the present
study, it is confirmed that the percentage of protein is highest among
the biochemical constituents. The percentages of saturated and polyunsaturated
fatty acids are high when compared to monounsaturated fatty acids studied
in the matured eggs of P. pelagicus. Further study is needed to
know which biochemical constituents and fatty acids are fairly utilized
during embryogenesis and larval development. For this investigation one
should study the biochemical changes of different stages of embryogenesis
and larval development.
In India the consumers mostly prefer bigger crabs viz., Scylla serrata
and S. tranquebarica. But as far as Parangipettai coast is concerned
the availability of these bigger crabs are restricted only in summer season.
Recently, Samuel et al. (2004) documented 12 commercial Portunid
crab species along Parangipettai coast. Among 12 commercial species the
blue swimming crabs, Portunus pelagicus and P. sanguinolentus
available throughout the year. In recent times the blue swimming crabs
are processed and finally sold as a processed food. So demand for these
crabs is increasing day-by-day. Although some information is available
on the biochemical changes during larval development of crabs (Kannupandi,
1980; Anger et al., 1983; Anger and Harms, 1990; Balagurunathan
and Kannupandi, 1995). Studies on the biochemical composition of crab
eggs are scanty. So study on the biochemical composition of matured eggs
are need of the hour. The principle components of most lipids are fatty
acids (Castal, 1981). Though the energy requirements is met from the oxidation
of fat during embryonic development of crabs the relative proportions
of fatty acids accompanying embryogenesis is still unknown. Hence in the
present study, biochemical changes and fatty acid profile was investigated
in matured eggs of P. pelagicus.
MATERIALS AND METHODS
Berried females of P. pelagicus were collected from the Annan
Kovil landing center at Parangipettai (Lat.11 °26`N; Long.79 °48`E).
The matured eggs were scrapped off from the brood with the help of scalpel.
The eggs were then sun dried for 3 days, properly ground using mortar
and pestle and subsequently used for biochemical analysis. The protein,
carbohydrate and lipid contents were estimated by adopting the standard
methods of Raymont et al. (1964), Dubois et al. (1956)
and Folch et al. (1956), respectively.
The fatty and methyl esters of the sample was injected into the gas chromatography
(AP5890) capillary column coated with 5% phenyl silicane at a temperature
from 170 to 310 °C for 23.33 min. Flame ionization detector was used
for analysis. Based on the retention time, the different fatty acid samples
were identified. Triplicate was maintained for each experiment.
The proximate composition of the matured eggs of P. pelagicus
is presented in Table 1. The protein, lipid and carbohydrate
contents of the P. pelagicus eggs were found to be 57.00, 14 and
The total values of saturated fatty acids in crab eggs were calculated
as 12.78%. Among various saturated fatty acids recorded, the amount of
myristic acid (06.36%) was maximum followed by and heptadeeanoic acid
(02.69%), pentadecanoic acid (01.83%) and minimum was capric acid (00.14%)
However total absence was reported for palmitic acid (Table
The total amount of monounsaturated fatty acids was found to be 02.97%.
Higher amount of monounsaturated fatty acid was nervonic acid (02.44%)
followed by myristoleic acid (00.25%) and eicosenoic acid (00.18%). Less
amount of fatty acid was palmitoleic acid (00.10%) (Table
The total amount of polyunsaturated fatty acids was calculated as 12.66%.
Maximum amount of fatty acid was reported to be Arachidonic acid (07.77%)
followed by linoleum acid (01.83%), esadic acid (1.82%) and linolenic
acid (01.11%). Minimum was linlelaidic acid (00.02%) (Table
|| Proximate composition in the matured eggs of P.
|| Saturated fatty acids in the matured eggs of P.
|| Monounsaturated fatty acids in the matured eggs of
|| Polyunsaturated fatty acids in the matured eggs of
The proximate composition changes during embryogenesis of crustacea vary
according to the yolk materials, ecological conditions in which the animals
live and initial egg size. During embryogenesis the crustacean eggs utilize
preferentially either protein or fat to meet their energy requirements.
Carbohydrate content of the egg is negligible as compared to that of either
fat or protein (Shakuntala and Pandian, 1972). Carbohydrate is typically
a minor contributor to embryonic metabolism (Holland, 1979). Some of the
scientist reported that which biochemical constituents are used during
embryogenesis (Kannupandi et al., 1999; Kannupandi et al.,
2003). But in the present study was focused only on eggs not on the different
stages of eggs. So it is highly impossible to say which biochemical constituent
is utilized for embryogenesis of P. pelagicus. So further study
is very much needed in this aspect.
In the present study, the protein content of the P. pelagicus
eggs was found to be 57.00%. The protein content of the yolk is important
for the tissue differentiation and organization particularly for the cuticle
layers, muscle, the digestive and nervous systems (Babu, 1987). Barnes
(1965) and Pandian (1972) reported that the protein in developing eggs
is progressively depleted and they also suggested the possible utilization
of protein during embryogenesis to meet the metabolic demand. The protein
content of the present study is comparable to other studies elsewhere
(Vijayaraghavan et al., 1976; Amsler and George, 1984; Kannupandi
et al., 1999).
Lipids are highly efficient source of energy in a way that they contain
more than twice the energy of carbohydrates and proteins. In the present
study, the lipid content of the matured eggs of P. pelagicus was
found to be 14.00%. Needham (1950) classified the crustacean eggs as cleidoic
and non-cleidoic types of eggs. The cleidoic eggs are not dependent on
the environment for water and salt (ash); oxidation of protein is suppressed
to considerable extend and fat oxidation is greatly enhanced, serving
as main source for the embryonic metabolism. But in non-cleidoic eggs
protein is the main energy source for the metabolism. Pandian (1970) reclassified
the crustacean eggs into terrestrial, marine and freshwater depending
upon the habit. In terrestrial eggs, the protein metabolism is greatly
suppressed and the oxidation of fat is high; while in the marine and freshwater
eggs, the protein metabolism is prominent. In the crab Callinectes
sapidus, the utilization of fat was higher than the protein. In rocky
intertidal zone beach crabs Xantho bidentatus eggs; the utilization
of fat was greater than that of protein. During egg development in dermasal
marine crustacean eggs, lipid was found to be the main energy source (Pandian
and Schmann, 1967; Pandian, 1967; Pandian, 1970, 1972). A similar pattern
has been reported for C. sapidus (Amsler and George, 1984) and
X. bidentatus (Babu, 1987). Kannupandi et al. (2003) also
reported that the utilization of lipid was greater than protein in S.
Carbohydrates constitute only a minor percentage of total biochemical
composition. In the present study, the carbohydrate content of the matured
eggs of P. pelagicus was 6.46%. The amount of carbohydrate in the
present study is comparable with other crabs (Kannupandi et al.,
To fuel the major anatomical changes during embryogenesis of crustaceans,
the stored energy reserves play a crucial role. These endogenous reserves
from the eggs not only provide energy but also important for the biosynthetic
precursors to meet the embryonic demands for growth and development (Whyte
et al., 1993). Two long chain Polyunsaturated Fatty Acids (PUFA),
eicosapentaenoic acid and docosahexaenoic acids are nutritionally essential
for the eggs and embryos (Kanazawa et al., 1979: Langdon and Waldock,
1981; Watanabe, 1982; Levine and Sulkin, 1984) and also for early larval
stages (Watnabe et al., 1982; De Pauw and Pruder, 1986; Mortensen
et al., 1988) of fish and shell fish.
In the present study, the total values of saturated fatty acids in P.
pelagicus eggs were calculated as 12.78%. Among various saturated
fatty acids recorded, the amount of myristic acid (06.36%) was predominant
and minimum was capric acid (00.14%). Usually palmitic acid was recorded
most of the marine animal source. But in the present study this acid was
The total amount of monounsaturated fatty acids in the present study
was found to be 02.97%. Higher amount of monounsaturated fatty acid was
nervonic acid (02.44%) and less amount of fatty acid was palmitoleic acid
(00.10%). The monounsaturated fatty acids like eicosenoic acid play an
active role in water transport and osmoregulation (Freas and Grollman,
The total amount of polyunsaturated fatty acids in the present observation
was calculated as 12.66%. Maximum amount of fatty acid was reported to
be Arachidonic acid (07.77%) followed by linoleum acid (01.83%) and minimum
was linlelaidic acid (00.02%). In the present study, PUFA is higher side
(16.97%) than MUFA (02.96%) probably is attributed to the fact that the
developing eggs require enormous energy for cleavage, gastrulation and
cellular differentiation in early stages and organogenesis in the later
developmental stages. This finding agrees with Mathavan et al.
(1986) and John Samuvel et al. (1998). According to Subramoniam
(1991) the cellular differentiation in mole crab starts soon after gastrulation
and requires enormous energy expenditure, which is supposed to be supplied
PUFA of both n-3 and n-6 types are important in biomembranes, particularly
in the vascular and nervous systems (Crawford et al., 1989; Vergroesen,
1989). Lands (1986) has shown that n-3 fatty acids act as a suppressant
to the biosynthetic pathway of prostaglandins, while n-6 fatty acids enhance
the path way. The high levels of linolelaidic acid, arachidonic acid in
the present study may also be due to the biosynthesis of prostoglandins
since, arachiodonic acid is the precursor for the biosynthesis of prostoglandins
(Mddleditch et al., 1979) and they have structural roles in phospholipids
and permeability (Ahigren et al., 1992).
From the present study, it is confirmed that the percentage of protein
is highest among the biochemical constituents. The percentages of saturated
and polyunsaturated fatty acids are high when compared to monounsturated
fatty acids studied in the matured eggs of P. pelagicus. Further
study is needed to know which biochemical constituents and fatty acids
are fairly utilized during embryogenesis and larval development. For this
investigation one should study the biochemical changes of different stages
of embryogenesis and larval development.
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