Scylla serrata are most commonly found with sheltered water in particular, estuaries, tidal flats and mangrove areas. They can tolerate a wide variation of conditions including temperatures between 12-15 degrees Celsius and salinity varying between 2-50 % (Keenan & Blackshaw, 1997). Whilst they can stand these variations, in recent studies it has been shown that their activity and feeding is greatly reduced in temperatures below 20 degrees.  They prefer muddy substrates as this is the easiest location for them to burrow during the day before coming out at night to feed (Department of Primary Industry New South Wales, 2010). Their diet mainly consists of barnacles, mollusc and bivalves but being a known an omnivorous scavenger, it is not uncommon to find them consuming plant material, other crabs and dead fish.

Introduction:
As commercial fisheries now look at aqua culturing as a possible future. Research into the possible meat yield of crabs become more and more important. Crabs are usually harvested once large enough to have undergone at least one mating season. At harvest, the crabs can be in a large range of weights, approximately 800 grams to 2-3kg (Keenan & Blackshaw, 1997). Therefore, for a species, like Scylla serrata, which are highly prized for the meat in their claw, it becomes paramount to know the relationship between weight of the crab and the yield or weight of the claw. In the same thought process, the relationship between the size of the crab’s claw in width and the weight of the crabs claw also becomes an important detail in deciding whether a crab claw would contain sufficient meat.

Method:
Crabs were collected from Moreton Bay, Queensland using standard crab pots with fish as bait. The crabs were then assessed to determine sex and if female were released back into the water. 20 males were then weighed using a standard scale, claws were weighed in a similar manner with the claw placed as dead weight on scale and then were measured using a ruler to determine width at longest part of the claw (See figure 6). The data was then analysed using linear regression techniques 

Results:
The results showed that as weight increased so did weight of the claw (P>0.05) as can be seen in figure 7. The claw weighed in a range of 40 to 50% the body weight of the crab. The crabs weight had a significant effect on the claw size with heavier crabs having larger claws (p>0.05) as can be seen in figure 5.

Discussion:
The claw size and weight were both affected by the weight of the crab. The relationship seems to be linear at the larger sizes indicating that the continuous growth of the crab may leads to both larger claws and weight. This may continue till the crab reaches a large size and may be more commercial valuable to those wishing to use these crabs for aquaculture purposing (Shelley & Lovatelli, 2011). In a similar study, the weight of the claw seemed to be related to weight of the animal in an exponential growth. Further study is need to analyse the trend to test for individuals of smaller and larger size.

The digestive tract of Scylla serrata is the same as any other member of the crustaceans. It is divided into three parts; foregut, midgut and hindgut. The foregut comprises of the mouth oesophagus and stomach. The midgut is known to be a tube with anterior and posterior caecum and midgut gland known as a hepatopancreas (Mantel, 1983). The hindgut from the is a simple straight tube that finishes at the anus. 

Scylla serrata’s circulatory system has always been classed as an open system like other crustaceans, but some suspect that the circulatory system of many crustaceans may be more complex than previously thought (McGaw, 2005). Like all decapods the heart of crab is single chambered with several arteries leaving it, these arteries feed throughout body of the crab the demand for oxygen (McGaw & Reiber, 2002). The heart is located on the dorsal side toward the posterior of the crab and is feed by a series of ostia. Out of the several arteries that leave the heart, only one artery, known as the descending artery, feeds the appendages. The rest spread out to other important feature of the crab such as the nerve cord and digestive tract.

The central nervous system is composed of a dorsal brain connect to a ventral nerve cord. This brain can be divided in three region known as the tritocerebrum, deuterocerebrum and protocerebrum. The ventral nerve cord is unlike other decapods as the subesophageal, thoraic and abdominal ganglia seem to be fused (Mantel, 1983). This may be due to the reduction of the abdominal segment as well as tail that all but non-existent in the crabs.

Gas exchange in Scylla serrata, like in other crustaceans, occurs across the surfaces of gills which are found in branchial chamber on the dorsal side of the body. Scaphognathites pump seawater into and through the chamber (Keenan & Blackshaw, 1997). Seawater enters the chamber at the posterior end and over each of the walking legs.  A series of bristles can be seen hanging down from the lower edge of the carapace to stop entry of unwanted organisms and for screening out particulate matter. On the interior these crabs have gills on both sides with epipods of the first maxilliped being specialised as gill cleaner for the crabs. These feature can be seen below in figure 9.

Scylla serrata is situated within the genus Scylla which has four representatives. The three other being located in similar locations are as follow Scylla olivacea, Scylla paramamosain and Scylla tranquebarica see figure 1. These species belong to the family Portunidae, also known as the swimming crabs all of which belong to the order decapoda (Karasawa & Schweitzer, 2006).