Maturation-associated changes in the internal distribution of tetrodotoxin in the female goby Yongeichthys criniger

Abstract

Maturation-associated changes in the internal distribution of tetrodotoxin (TTX) in the goby Yongeichthys criniger were investigated in 29 and 40 female specimens collected from Okinawa, Japan, from August 2008 to June 2009 (Group I), and from November 2009 to August 2010 (Group II), respectively. In Group I, based on changes in the gonadosomatic index (GSI) and histologic observation of the ovary, the period from October 2008 through January 2009 was estimated to be the 'previtelline-forming period', February through March 2009 the 'vitelline-forming period', April through June 2009 the 'spawning period', and August 2008 the 'end of spawning period' of the preceding year. The TTX content (mouse unit [MU] per gram tissue) of each Y. criniger tissue (skin, muscle, liver, and ovary) quantified by liquid chromatography/mass spectrometry (LC/MS) was generally high during the spawning period and continued to rise until the end of spawning period, especially in the ovary. Total TTX per individual increased considerably during the spawning period, most of which located in the ovary, indicating that Y. criniger obtains a high amount of TTX during the spawning period, and accumulates most of it in the ovary. In contrast, the TTX content of the skin was highest at the end of spawning period, and most of the total TTX located in the skin during this period as well as during the previtelline-forming period. In Group II, the maturation stage of the ovaries of all specimens was determined, and the specimens were grouped accordingly. In the perinucleolus stage, yolk vesicle stage, and yolk globule stage I, most of the TTX was localized in the skin, but the TTX in the ovary greatly increased as the maturation stage advanced from yolk globule stage I to yolk globule stage III.