516 



THE BIOLOGY OF MARINE ANIMALS 



they were produced and secreted in an endocrine organ, the sinus gland 

 (Fig. 12.7(a)). This gland is usually located in the eye-stalk of malacostraca, 

 but in some forms (isopods, anomuran Upogebia, etc.) the sinus gland lies 

 near the brain. The gland is richly innervated and contains numerous 

 secretory inclusions. 



It is now established that the sinus gland belongs to the category of 

 neurosecretory organs. Secretory cells in various parts of the central nervous 



Fig. 12.7. (a). Location of the Sinus Gland in the Eyestalk of the Prawn 

 Palaemon serratus. The Right Eye is Viewed from Above, and a Small Aper- 

 ture has been Cut in the Cuticle above the Sinus Gland (from Knowles, 



1950) 



(b) Diagrammatic Representation of the Anterior Region of the 

 Nervous System of the Sand Shrimp {Crangon vulgaris (from Brown and 



Ederstrom (15), and Turner (68).) 



cc, circumoesophageal connective; eg, connective ganglion; e, medulla externa; 

 /', medulla interna; m, muscle; oe, oesophagus; sg, sinus gland; /, medulla terminalis; 

 tc, tritocerebral commissure. 



system (x-organ of the eye-stalk, brain, thoracic ganglia) send axons to the 

 sinus gland, where their swollen terminals form the secretory mass of the 

 organ. Secretory material (the hormonal precursors) passes down the axons 

 and is stored in the sinus gland, whence it is released into the blood stream 

 when occasion demands. Another important neurosecretory organ of 

 malacostracans occurs in the post-commissure (tritocerebrum) (Fig. 

 12.7(6)). 

 Release of hormonal material from the neurosecretory organs is regu- 



