Abstract In this study, we report six records of the non-native giant river prawn Macrobrachium rosenbergii (De Man, 1879) in the Furnas mega reservoir, state of Minas Gerais (Southeast Brazil), during continuous monitoring conducted from 2006 to 2023. All recorded specimens were males of the blue claw (BC) morphotype and possibly entered interior areas of the reservoir via accidental escapes. There was no occurrence of established populations in the region, nor any evidence of disease in the specimens obtained. However, continuous monitoring is recommended to record new escapes and determine the possibility of establishment of giant river prawn populations in the aquatic environment of the Furnas mega reservoir.

Abstract Gonopods are phylogenetically important morphological characters, and in several cases providing diagnostic characters to support taxonomic and phylogenetic studies. Relatively few studies, however, have emphasized in-depth descriptions of gonopods, and the functional morphology of these structures are poorly understood. We use SEM to describe and illustrate the two pairs of gonopods (G1 and G2) of nine species of Mithracidae (Majoidea) and of Macrocoeloma trispinosum Latreille, 1825, recently relocated to Epialtidae (Majoidea). The G1 was found to present the typical characteristics of Majoidea: long, with a mesial suture, setae inserted from the base to the distal second third and sensilla in the apical plate; the G2 is always short and conical. The apical region of the G1 was diagnostic for the species analyzed, which could provide important characters for differentiating among the majoids; and also for studying the functional, reproductive, and phylogenetic significance of these structures.

Resumo: O objetivo deste trabalho foi descrever a relação hospedeiro-Epistylis sp. durante infestação em peixes cultivados. Foram utilizados cinco tilápias-do-nilo (Oreochromis niloticus) e dez híbridos de surubim (Pseudoplatystoma reticulatum x P. corruscans), todos parasitados, para análise morfológica in vivo de peritríquios sésseis por microscopia de contraste de fase. Fragmentos de tecidos infectados foram processados para histologia e microscopia eletrônica de varredura. Epistylis sp. causou doença ulcerativa hemorrágica, e os ciclídeos foram mais susceptíveis ao parasitismo na superfície do corpo em razão da fixação das colônias nas escamas, o que não ocorreu nos pimelodídeos. Foi observada ocorrência de dermatite granulomatosa multifocal, associada à degeneração hidrópica do epitélio e às áreas ulcerativas de necrose. O estudo microscópico mostrou a presença de bactérias associadas aos pedúnculos de Epistylis sp. Portanto, esta espécie pode ser considerada porta de entrada para bactérias oportunistas.

Abstract: The objective of this work was to describe the host-Epistylis sp. relationship during infestation on farmed fish. Five Nile tilapia (Oreochromis niloticus) and ten hybrid surubim catfish (Pseudoplatystoma reticulatum x P. corruscans), all diseased, were used for in vivo morphological analysis of sessile peritrichs by contrast microscopy. Fragments of infected tissues were subjected to histological processing and scanning electron microscopy. Epistylis sp. caused hemorrhagic ulcer disease, and cichlids were more prone to develop infestations throughout the body surface due to the attachment of the colonies to the scales, which did not occur with pimelodids. Multifocal granulomatous dermatitis was observed, associated with the hydropic degeneration of the epithelium and to ulcerative areas of necrosis. Microscopic examination showed the presence of bacterial microflora associated to Epistylis sp. peduncles. Therefore, this species can be considered a portal of entry for opportunistic bacteria.

This study describes the histology and histochemistry of the male reproductive system in Callinectes ornatus, comparing juvenile and adult developmental stages. We also analyzed changes in the gonadosomatic (GSI) and hepatosomatic (HSI) indices, and the weights of the testis and vas deferens during the development. The results showed that all stages, beginning with the juvenile (JUV), through developing (DEV) and mature (MAT) adult males of C. ornatus produce sperm and spermatophores. During development, testicular lobes showed the same characteristics of production and release of sperm into the seminiferous duct. The vas deferens showed little histological and histochemical change in the epithelium in juvenile and adult males. The differences consisted of the larger amount of secretion in MAT males compared to JUV and DEV ones. The chemical composition of the seminal fluid was similar, but MAT males produced a more homogeneous secretion. Morphological and physiological maturation are not synchronized in C. ornatus, since JUV males produced spermatophores similar to those in DEV and MAT males. However, these JUV are not yet able to reproduce, since they still have the abdomen attached to the cephalothoracic sternum. The increase of the GSI during development was significant for MAT males, and is related to the production of sufficient volume of seminal fluid to form the sperm "plug" in the female seminal receptacle. The HSI decreased from DEV to MAT adult stages, indicating that reserves from the hepatopancreas are used to develop the reproductive system after the pubertal molt.