Transverse Section of the Exoskeleton of Brachyura Cuticle (Warner, 1977)

Epicuticle	Does not contain chitin  Composed of lipo-protein  Not as heavily calcified as the deeper layers
Exocuticle	Layers of chitin-protein microfibrils  Mirofibrils are tightly packed and fine  Pigmented
Endocuticle	Layers of chitin-protein microfibrils  Microfibrils are large and staked losely  Unpigmented
Membranous Layer	Uncalcified  Construction is similar to endocuticle

Major differences between the four layers.

Branchial Chambers, Gills & Ventilation

The branchial region of Stimdromia lateralis.
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Beneath the branchiostegites, are the branchial chambers.  Each of these chambers are wrap with a thin cuticular membrane, this membrane separates the chambers from hepatopancreas and carapace, hence, it lines the whole branchial region of the crab (Warner, 1977).

The brachial chamber of Brachyura (Warmer, 1977).

Each branchial chamber houses 9 gills.  These gills are connected to the bases of the thoracic limbs.  The gills are separated into 3 types:  

1. Podobranches -> arising from the epipods
2. Arthrobranches-> arising from the functions of limbs with the body
3. Pleurobranches-> arising from the body wall

Respiratory Pathway

Digestive System

Digestive tract of Stimdromia lateralis.

Gut:  Ectodermal foregut and hind-gut that are lined with cuticle, endodermal mid-gut that lacks cuticle.

Mouth:  Gland cells supplied mouth opening are situated between and behind the mandibles.

Oesophagus:  Short muscular tube that is also invested with gland cells.

Stomach:  There are two main regions of the stomach, the cardiac stomach, and the pyloric stomach.

With the special feature of gastric mill on the posterior end of the cardiac stomach, the cardiac stomach is mainly used for chewing and grinding, since the mandibles only cut and crush food when food is ingested by the mandibles, but not chewing (Warner, 1977).

Once food is processed into smaller pieces in the cardiac stomach, they enter the pyloric region of the stomach which is responsible for filtering and sorting of food particles.  Finely ciliated lining allows only small particles and liquid to pass through, the rest of the indigestible matters and coarser materials bypass the mid-gut and are then excreted from the anus at the end of the hind-gut (Warner, 1977).

The excretory organs of crustaceans are called the green glands, paired ducts structure that is situated at the base of the 2nd antennae (Ruppert et al., 2004).

There are four functional parts:  End Sac, Labyrinth, Bladder and the Ureter.  The end sac and the labyrinth are situated closely and together they form a green sponge mass behind the orbits.  These are the sites where blood ultrafiltration and urine modification occur.  The bladder is situated over the stomach of the crab, and it is connected to the ureter (Warner, 1977).

The abdomen and anus of Stimdromia lateralis.

Reproductive System

Gonads are paired organs that sit under the carapace and lie above the hepatopancreas.

Males:  Size of gonads are smaller than female.  Vasa deferentia which emerge from the testes are sites for sperm storage.  Ejaculatory ducts open on the ventral sides of the coxa of the last pair of legs.

Females:  Paired genital openings on the sternite of the 6th thoracic segment connecting the spermatheca that lie amongst the basal muscle of the 2nd walking legs.  After copulation, the spermatheca are stored with sperms.  Short oviducts on either side connect the ovaries to the spemathecae, where eggs pass through for fertilisation.

(Warner, 1977)


Nervous System