Circulatory System in Finfish and Shellfish

arteries 
are 
responsible 
for 
carrying oxygenated 
blood from the heart 
to the rest of the 
body, while the veins 
return deoxygenated 
blood 
from 
the 
different parts of the 
body to the heart.
Vein 
 
Deoxygenated 
Blood 
A
rtery 
 
Oxygenated 
Blood 

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Circulatory system in Prawn 
In prawn circulatory system is 
open or lacunar type
, in which the 
veins 
and capillaries are totally absent
. The blood vessels open into spaces. 
These spaces are without a proper epithelial lining and are called lacunae 
or sinuses. The sinuses together form the body cavity which looks like a 
coelom but filled with blood and devoid of epithelial lining is known as 
haemocoel 
Circulatory system in Palaemon consist of 
1. Pericardium 
2. Heart 
3. Arteries 
4. Blood Sinuses 
5. Blood Channels 
6. Blood 

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Pericardium
: it is a thin walled chamber around the heart and remain 
filled with haemo-coelomic fluid. The pericardiam cavity pumps blood 
into heart 
Heart
: it is a triangular and muscular structure and found in the 
pericardial sinus in the median dorsal part of thorax. There are 
5 
pairs of valvular opening
, the 
ostia
in the wall of heart. The 1
st
pair 
in mid dorsal region, 2
nd
pair in mid ventral region, 3
rd
pair on 
posterior border, 4
th
pair lie anterio-laterally and 5
th
pair posterio 
laterally. 
Arteries
: they are thick walled muscular tube, which arise from the 
heart and supply blood to different organs of body. Four main arteries 
are as follows: