The creation of sexual dimorphism in the gonads is essential for producing the male and female gametes required for sexual reproduction. Sexual development of the gonads involves both somatic cells and germ cells, which often undergo sex determination by different mechanisms. While many sex-specific characteristics evolve rapidly and are very different between animal species, gonad function and...

The round goby (Neogobius melanostomus Pallas 1811) is a non-native species in the Gulf of Gdańsk. The aim of this article is to assess the absolute fecundity and attempt to describe the gonad development cycle of round goby specimens from the Gulf of Gdańsk. The stages of gonad development were classified according to the modified Nikolski (1963) scale for perciformes, which was adapted for th...

In most organisms, primordial germ cells are set aside from the cells of the body early in development. To form an embryonic gonad, germ cells often have to migrate along complex routes through and along diverse tissues until they reach the somatic part of the gonad. Recent advances have been made in the genetic analysis of these early stages of germ line development. Here we review findings fr...

The objective of this study was to provide information on the histological characteristics of the gonads of male and female Armases rubripes crabs, and to try to establish a relationship between the microscopic and macroscopic stages previously identified. Thirty-six crabs were collected by hand between February 2003 and January 2004 in banks of Spartina alterniflora on Sahy Beach in Mangaratib...

A method to mitigate or possibly eliminate reproduction in farmed fish is highly demanded. The existing approaches have certain applicative limitations. So far, no immunization strategies affecting gonadal development in juvenile animals have been developed. We hypothesized that autoimmune mechanisms, occurring spontaneously in a number of diseases, could be induced by targeted immunization. We...

Recently, YY super-male yellow catfish had been created by hormonal-induced sex reversal and sex-linked markers, which provides a promising research model for fish sex differentiation and gonad development, especially for testis development. MicroRNAs (miRNAs) have been revealed to play crucial roles in the gene regulation and gonad development in vertebrates. In this study, three small RNA lib...

Sudhausia aristotokia n. gen., n. sp. and S. crassa n. gen., n. sp. (Nematoda: Diplogastridae): viviparous new species with precocious gonad development Matthias HERRMANN 1, Erik J. RAGSDALE 1, Natsumi KANZAKI 2 and Ralf J. SOMMER 1,∗ 1 Max Planck Institute for Developmental Biology, Department of Evolutionary Biology, Spemannstraße 37, Tübingen, Germany 2 Forest Pathology Laboratory, Forestry ...

An experiment was conducted to investigate the annual reproductive cycle of a Korean endemic species, Acheilognathus majusculus, from Jeokseong-myeon located in Seomjin River. The reproductive cycle is examined histologically regarding water temperature and day length of the habitat, the gonadosomatic index (GSI), the female ovipositor length index (OLI), monthly variation in egg diameter distr...

Groups of mature (5+ year old) Arctic charr Salvelinus alpinus held in sea water were exposed for 34 days to either a high (mean +/-s.e. 0.15 +/- 0.01 sea lice Lepeophtheirus salmonis g(-1) fish mass) (HI), medium (0.07 +/- 0.00 sea lice g(-1) fish mass) (MI) or no [control (C)] sea-lice infection during early stages of gonad development (June to July). Infection with sea lice resulted in incre...

In mammals, the Wilms' tumor suppressor gene, Wt1, encodes a transcription factor critical for development of the urogenital system. In teleost fish, however, two wt1 genes have been identified. In medaka wt1a is expressed in the lateral plate mesoderm during early embryogenesis. Later in development, wt1a is additionally expressed in the somatic cells of the gonadal primordium. We show here fo...