The identification and distribution of gonadotropin-releasing hormone-like peptides in the central nervous system and ovary of the giant freshwater prawn, Macrobrachium rosenbergii

Abstract

In the present study, we demonstrated the existence of GnRH-like peptides in the central nervous system (CNS) and ovary of the giant freshwater prawn, Macrobrachium rosenbergii using immunocytochemistry. The immunoreactivity (ir) of lamprey (l) GnRH-III was detected in the soma of medium-sized neurons located in neuronal cluster number 11 in the middle part of supraesophageal ganglion (deutocerebrum), whereas ir-octopus (oct) GnRH was observed in the soma of both medium-sized and large-sized neurons in thoracic ganglia, as well as in the fibers innervating the other medium-sized and large-sized neuronal cell bodies in the thoracic ganglia. In addition, ir-lGnRH-I was observed in the cytoplasm of late previtellogenic oocyte and early vitellogenic oocyte. These data suggest that M. rosenbergii contain at least three isoforms of GnRH: two GnRH isoforms closely related to lGnRH-III and octGnRH in the CNS, whereas another isoform, closely related to lGnRH-I, was localized in the ovary. This finding provides supporting data that ir-GnRH-like peptide(s) may exist in this decapod crustacean.

Existence and distribution of gonadotropin-releasing hormone-like peptides in the central nervous system and ovary of the Pacific white shrimp, Litopenaeus vannamei

“…Similarly, in our earlier studies, lamprey (I) GnRH-ir and octGnRH-ir have not been detected in the eyestalk of P. monodon (Ngernsoungnern et al 2008c) or in M. rosenbergii (Ngernsoungnern et al 2008a). This is in contrast to the report by Amano et al (2009) who have shown GnRH-ir in the neurons of the medulla interna and immunoreactive fibers in the medulla interna, medulla externa, and lamina ganglionalis in the Kuruma prawn, Marsupenaeus japonicus.…”

“…Furthermore, no octGnRH-ir has been detected in neurons or in any neuropils in the abdominal ganglia of M. rosenbergii (Ngernsoungnern et al 2008a), although some positive fibers have been seen in P. monodon (Ngernsoungnern et al 2008c). Since the intensity of GnRH-ir is low, and since positive fibers are sparse, we suggest that GnRH in the abdominal ganglia might not be a significant factor in the regulation of ovarian maturation in the white shrimp.…”

“…In the black tiger shrimp, P. monodon, octGnRH-ir has been detected in medium-sized neurons in cluster 6, with some fibers of the median protocerebrum, deutocerebrum, and tritocerebrum being octGnRH-positive (Ngernsoungnern et al 2008c). In the freshwater prawn, M. rosenbergii, lGnRH-III-ir has been detected in medium-sized neurons in cluster 11 of the deutocerebrum, but no octGnRH-ir neurons and fibers have been found in the median protocerebrum, deutocerebrum, and tritocerebrum (Ngernsoungnern et al 2008a). In comparison with these two shrimp species, GnRH-like peptides in L. vannamei seem to be more widely spread.…”

“…Our group has previously investigated the existence of GnRH-like peptides, by using antibodies against lGnRH-I, lGnRH-III, and octGnRH, in two other prawn species. lGnRH-I-ir has been detected in the cytoplasm of late previtellogenic oocytes (Oc2) and vitellogenic oocytes (Oc3) in M. rosenbergii (Ngernsoungnern et al 2008a) and in the cytoplasm of the follicular cells in the vitellogenic stage (Oc3) of P. monodon (Ngernsoungnern et al 2008b). However, in L. vannamei, octGnRH-ir and tGnRH-I-ir have been localized not only in the cytoplasm of previtellogenic oocytes (Oc2), vitellogenic oocytes (Oc3), and mature oocytes (Oc4), but also in follicular Fig.…”

“…Octopus GnRH, lamprey GnRH-I, and lamprey GnRH-III can also induce ovarian maturation in the freshwater prawn (M. rosenbergii; Ngernsoungnern et al 2009). In addition, the existence and distribution of GnRH-like peptides in the central nervous system (CNS) and in reproductive tissues have been revealed by using immunohistochemistry in a number of invertebrates, including mollusks (A. californica; Pazos and Mathieu 1999;Tsai et al 2003; Haliotis asinina; Nuurai et al 2010b), tunicates (Ciona intestinalis; Tsutsui et al 1998;Di Fiore et al 2000), the black tiger shrimp (P. monodon; Ngernsoungnern et al 2008c;Ngernsoungnern et al 2008b), and the freshwater prawn (M. rosenbergii; Ngernsoungnern et al 2008a), and might be present in other crustaceans, including L. vannamei.…”