Gender determination in the Paiche or Pirarucu (Arapaima gigas) using plasma vitellogenin, 17β-estradiol, and 11-ketotestosterone levels

Abstract

Arapaima gigas is an air-breathing giant fish of Amazonian rivers. Given its great economic and cultural importance, the aquaculture development of this species represents an evident solution to face the decline of wild populations. In captivity, reproduction occurs generally in large earthen ponds where stocks of a few tens of brooders are maintained together at the beginning of the rainy season (December-March in the Peruvian Amazon). Fry production relies on the spontaneous formation of male and female pairs, which build a nest, delimit a territory and guard the offspring for at least 20 days from other congeners and predators. However, as sex determination of A. gigas is not possible by morphological criteria, it is very difficult to optimize reproduction conditions and fry production in each pond, which seriously hampers the culture of this species. This situation prompted us to develop sexing methodologies based on (1) the detection of female specific plasma Vitellogenin (Vtg) using an enzyme immuno assay (EIA), and (2) the determination of plasma 17beta-estradiol and 11-ketotestosterone levels for immature specimens. The Vtg purification was performed by electro-elution after polyacrilamide gel electrophoresis (PAGE) from plasma of 17beta-estradiol treated A. gigas juveniles. Two different Vtg molecules were isolated, (Vtg(1) and Vtg(2)) with 184 and 112 kDa apparent molecular masses, respectively, and two antibodies were raised in rabbits for each Vtg molecule. Adult fish were 100% accurately sexed by Vtg EIA, while 100% of immature fish and 95% of adults were accurately sexed by 17beta-Estradiol and 11-Ketestosterone ratios. We also observed different color pattern development in male and female adult fish (6-year-olds) around the reproductive period.

Sex determination in the Giant fish of Amazon Basin, Arapaima gigas (Osteoglossiformes, Arapaimatidae), using laparoscopy

“…The laparoscopic examination revealed six female and four male, fact that leads us to believe that scale coloration patterns of sexually immature fish was not reliable as a characteristic for sexual differentiation. Chu-Koo et al (2008) achieved 95% efficiency in sex determination of 2.8 year-old pirarucu by using enzyme-immuno-assay while laparoscopy produced 100% accuracy (present work) by direct observation of oocytes, leading us to believe that laparoscopy is a reliable method for sex determination in immature pirarucu and can be considered a powerful tool in the management of aquaculture facilities.…”

“…The word pirarucu comes from the native Brazilian language tupi-guarani and which means "red fish", which is the color both sexes turn during the mating season. Males display an intense red color on abdominal scales whereas the red color is less intense in female specimens (Fontenele 1955;Chu-Koo et al 2008). However, this characteristic is not reliable as a means to differentiate sexes, and therefore, it is not used for this purpose.…”

“…To the best of our knowledge, no reliable method for sexual determination has been described for this species with the exception of minor morphological differences observed only in mature fish during the initiation of courtship behavior at approximately five years of age (Imbiriba 2001;Saavedra-Rojas et al 2005;Chu-Koo et al 2008). The absence of external characteristics for sexual determination has encouraged the development of practical and nondamaging techniques of internal examination of the gonads based on laparoscopy.…”

The influence of sex ratio on the reproduction of pirarucu, Arapaima gigas, in captivity

“…Pirarucu breeders from the same origin had been reared at the farm for four years since the juvenile stage. Individuals were captured with a dragnet and measured, and blood samples were collected for sex determination by the presence of vitellogenin (Chu-Koo et al 2009) using a commercial kit (Acobiom®). Breeders were stocked in twelve earthen ponds with 0.10-0.13 ha surface area and 1.8 m deep, located side by side.…”

CIRI KELAMIN SEKUNDER PADA ARWANA SILVER (Sclerophages macrocephalus) VARIETAS PINOH

“…Penelitian determinasi seks arwana banjar dapat melalui teknik penentukan kelamin melalui metode dootblood menggunakan anti vetelogenin (Vtg). Pembuatan antibodi vitelogenin (Vtg) dalam tubuh kelinci dan pengujian antibodi dengan EIA seperti prosedur yang dilakukan oleh Chu-Koo et al (2008). Vtg didapat dari plasma darah ikan arapaima yang sebelumnya disuntik dengan 17β-estradiol.…”