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

Abstract

The Giant of Amazon basin, pirarucu, Arapaima gigas, is the largest scaled freshwater fish in the world. Pirarucu cultivation has recently started, driven by the decline in natural populations and high market value. Currently, there are no reliable methods for sexual differentiation in this species other than direct examination of gonads, which requires dissection of specimens. A non-lethal and less invasive method for sexual identification is highly desirable in order to properly group broodstock for mating and offspring production. We utilized laparoscopic examination in anesthetized pirarucu to differentiate between male and female individuals. This method allowed for the observation and differentiation of the reproductive organs within an individual. Our results suggest that laparoscopy is an efficient method for sex differentiation in pirarucu causing minimal stress to the fish. Determinação do sexo no peixe gigante da Bacia Amazônica, Arapaima gigas (Osteoglossiformes, Arapaimatidae), usando laparoscopia.O gigante da bacia amazônica, pirarucu, Arapaima gigas, é o maior peixe de escamas de água doce do mundo. O seu cultivo teve início recentemente motivado pelo declínio de suas populações naturais em virtude do alto valor de sua carne no mercado. Não existem métodos para a diferenciação sexual nesta espécie, o único método é o exame direto das gônadas, o qual requer a dissecação do espécime. Um método para a identificação sexual é altamente desejável, a fim de selecionar grupos de reprodutores para o acasalamento e, portanto, a produção de progênie. A fim de diferenciar reprodutores machos de fêmeas, foi utilizado o exame laparoscópico em animais previamente anestesiados. Este método permitiu a observação dos órgãos abdominais, incluindo gônadas, com grande precisão. Os resultados mostram que a laparoscopia é um método eficiente para a diferenciação do sexo em pirarucu e causam o mínimo de stress para os animais.

Effects of stocking density on the performance of juvenile pirarucu (Arapaima gigas) in cages

“…The low number of treatments and proximity of stocking densities occurred due to low supply of fingerlings in Ceará State. This occurs due to the absence of specific studies on plankton or other available food sources for larvae feeding, resulting in low survival in larval and fingerling stages (Carreiro et al, 2011;Núñez et al, 2011). Cage frames were made of steel pipes covered with a 30-mm galvanized wire mesh coated with UV resistant PVC.…”

Endoscopy application in broodstock management of Arapaima gigas (Schinz, 1822)

“…Given the impossibility of cannulating A. gigas (Núñez et al., ), the only method for maturity identification successfully tested thus far was through laparoscopy, although it was initially developed for juvenile sex identification (Carreiro et al., ). However, such a technique is invasive and involves surgery.…”

Bulked segregant analysis of the pirarucu (Arapaima gigas) genome for identification of sex-specific molecular markers

“…This issue is particularly critical for larger species, because fewer individuals tend to be kept as broodstock for reasons of production efficiency. High levels of behavior-induced stress caused by inadequate management of breeding animals, due to the allocation of disproportionate numbers of females to males in breeding tanks, can jeopardize the production of fry (Carreiro et al, 2011). In species such as sturgeon (Huso huso), where sex-specific molecular markers have not been identified (Keyvanshokooh et al, 2007), surgical (Falahatkar et al, 2011) and non-invasive (Masoudifard et al, 2011) methods have been developed for sexing fish.…”