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Vol. 53, 2014
Secretory activity of mandibular organ fluctuates in response
to reproductive season of the field crab Paratelphusa sp. (Brachyura;
Decapoda): an ultrastructural study
SN
Sarika1, N Gayathri2 and Anilkumar Gopinathan1*
1School
of Bio Sciences and Technology (SBST), VIT University, Vellore, Tamil
Nadu 632014, India.
2Electron Microscopy facility, Department of
Neuropathology, National Institute of Mental Health and Neurosciences
(NIMHANS), Bangalore 560029, India.
Abstract
Background: Mandibular
organ (MO) in decapods is suggested to play regulatory role in
reproduction, in few species; however, MO is considered to control
growth. The present study addresses this question by an ultrastructural
study on the MO of the field crab, Paratelphusa sp. Our sampling for consecutive years (2008 to 2012) revealed that Paratelphusa
sp. devotes July to October for reproduction, judged by the occurrence
of growing ovaries and the berried females. From November to the
succeeding June, the females are in a state of reproductive arrest
(non-reproductive period); ovaries during this season would appear as
white bands with no signs of yolk deposition.
Results: Morphologically, MO of Paratelphusa sp. is positioned posterior to the mandibles and is in close apposition with the distal end of the mandibular apodeme. MO of Paratelphusa sp. exhibited significant levels (t = 8.097, P < 0.0001, N
= 10) of season-dependent size variations. Our electron microscopic
observations reveal that the MO is highly secretory during the
reproductive period, evidenced by the occurrence of sacculated Golgi
bodies having dense inclusions, several mitochondria with tubular
cristae, and extensive networks of SER and rough endoplasmic reticulum
(RER). During the non-reproductive period, however, the MO is least
active; RER, the mitochondria, and the Golgi are only sparsely seen.
Interestingly, the plasma membrane exhibits a highly convoluted
appearance all the way through the non-reproductive period.
Conclusions: The present study reveals that the secretory activity of MO of Paratelphusa
sp. is entrained with reproductive activity. The existence of a high
correlation between MO secretory activity and ovarian growth implicates
the former’s role in reproduction.
Key words: Mandibular organ; Reproduction; Brachyuran crabs; Decapoda; Paratelphusa
*Correspondence: E-mail: ganilkumar@vit.ac.in
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