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This study investigated the in vivo and in vitro antiparasitic effects of the essential oil of Lippia alba and the bloodrelated and histopathological alterations that it causes in Colossoma macropomum. In the in vitro trial, the anthelminthic effects of 160, 320, 640, 1280 and 2560 mg/L of the essential oil were tested against monogenoideans (Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri) of the gills of this fish, which are its natural parasites. The concentrations of 1280 mg/L and 2560 mg/L showed 100% efficacy after 20 min of exposure to the essential oil, while at lower concentrations this efficacy against the gill monogenoideans only occurred after 2-3 h of in vitro exposure. However, in the controls, mortality of all of these monogenoideans only occurred after 9 h. A total of 240 fry were distributed into four treatments (20 fish per repetition) and three repetitions were used in the in vivo trial for baths with 100 and 150 mg/L of the essential oil of L. alba, for 30 min. The efficacy in this trial against Ichthyophthirius multifiliis in fish exposed to 100 and 150 mg/L of the essential oil was 40.7% and 50.3%, respectively. However, for monogenoideans, there was efficacy of 14.0% only in the fish exposed to 100 mg/L of the essential oil used. Moreover, the fish exposed to these concentrations of the essential oil presented increased plasma glucose levels, thus denoting signs of stress. Severe lesions such as hyperplasia, fusion of the lamellar epithelium, capillary dilatation, epithelial detachment, lamellar aneurysm, epithelial rupture with hemorrhage, congestion, edema, necrosis, mucous cell proliferation, chloride cells and lamellar hypertrophy were observed in the gills of the fish exposed to 100 and 150 mg/L of the essential oil of L. alba. Alterations to total protein levels, hemoglobin, hematocrit, red blood cell number, thrombocytes number, white blood cell number, lymphocytes, eosinophils and blood neutrophil number was also observed in these fish. The essential oil of L. alba showed great potential for antiparasitic treatment, given that it had high in vitro efficacy against monogenoideans and in vivo efficacy against the protozoon I. multifiliis. Because of the low concentrations of the essential oil (100 and 150 mg/L) that were tolerated by the fish and thus could be used in the therapeutic baths, the efficacy against monogenoideans was low. This indicates that there is a need for additional strategies for using this essential oil in antiparasitic treatments, since the concentrations that eliminate these ectoparasites are toxic for the hosts. Lastly, this was the first study on the antiparasitic activity of L. alba. Statement of Relevance The manuscript entitled "Antiparasitic activity of the essential oil of Lippia alba on ectoparasites of Colossoma macropomum (tambaqui) and its physiological and histopathological effects", represents original article on use of the essential oil of Lippia alba on ectoparasites of tambaqui, an important finfish of Amazon regio...

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This study evaluated the use of therapeutic baths containing essential oils of Lippia sidoides (pepper rosemary) and Mentha piperita (peppermint) on the hematological parameters of Nile tilapia parasitized by the monogeneans Cichlidogyrus tilapiae, Cichlidogyrus thurstonae, Cichlidogyrus halli, and Scutogyrus longicornis. A total of 320 juvenile fish were distributed into 16 tanks of capacity 100 L (20 fish per tank), divided into 4 treatments in quadruplicates: fish exposed to a bath of L. sidoides at 20 mg L −1 ; fish exposed to M. piperita at 40 mg L −1 ; fish exposed only to a water bath; and fish exposed to water + DMSO (dimethyl sulfoxide) bath. The fish were subjected to 3 baths for 10 min, at intervals of 24 h between treatments. After the third bath, parasitological and hematological analyses were performed. The parasite prevalence in fish treated with essential oils was seen to have decreased by 70%. The efficacy attained among fish treated with L. sidoides, in comparison with control water and water + DMSO, was 1.96% and 14.16%, respectively; and among fish treated with M. piperita, it was 33.33% and 41.63%, respectively. The total numbers of red blood cells (RBC) and thrombocytes were lower in fish treated with L. sidoides. Glucose concentration and neutrophil count were significantly higher in fish treated with L. sidoides. Because of the efficacy and positive hematological results, we suggest that baths of M. piperita at 40 mg L −1 should be used as anthelmintic action. Statement of relevance: Authors believe on the use of essential oils to treat ectoparasites of cultured fish and consequently no damages for hematological profile of Nile tilapia were found.

Infection by the acanthocephalan Neoechinorhynchus buttnerae is considered the most important obstacle in farmed tambaqui or cachama (Colossoma macropomum), the second most cultivated fish species in Brazil. This study describes the occurrence of N. buttnerae in farmed this fish based on parasitological and histopathological analysis in highly infected fish. A total of 102 fish were collected from fish farms located in Brazilian states in the northern region. All of the examined fish were heavily infected by N. buttnerae and showed no signs of anorexia, but heterogeneous growth and cachexia were frequently found. No cases of mortality were observed in fish farms. Macroscopically, the intestines showed hyperaemia, hardening, thickening of the intestinal wall, yellowish mucosal secretion and a bluetongue aspect. Histological sections showed different degrees of penetration of the acanthocephalan proboscis in the intestinal tissue, surpassing the mucosa, submucosa and muscular layer, provoking dilacerations due to their spines as well as an intense inflammatory reaction composed of macrophages, Langerhans cells and lymphocytes, and granuloma formation located mainly in the submucosa layer. Submucosal oedema, an increased number of goblet cells, metaplasia areas and a reduction of the intestinal villi were also observed. The results present an important register of N. buttnerae infection in C. macropomum and contribute to the comprehension of pathogeny caused by these worms. Statement of relevance: Characid fish farming has led to significantly increased fish production in Brazil. However, the most important obstacle is the acanthocephalan infection caused by Neoechinorhynchus buttnerae in the intestinal tract. The infection does not provoke death but cachexia and growth reduction are frequently observed as well as intense pathological conditions in histological sections.

O objetivo deste trabalho foi determinar a densidade de estocagem mais adequada para a fase de recria de juvenis de tambaqui (Colossoma macropomum) em tanque-rede. Foram utilizados 12 tanques-rede de 1 m³ cada, com peixes distribuídos nas densidades de 200, 300, 400 e 500 peixes/m³ em três repetições. Os peixes foram alimentados seis vezes por semana em três refeições diárias com ração comercial com 36% de proteína bruta, durante 60 dias. Foram analisados o crescimento em peso e em comprimento, o coeficiente de variação do comprimento, a taxa de crescimento específico e a glicose sanguínea aos 30 e 60 dias de criação. Ao final do experimento, foram analisados os seguintes parâmetros de produtividade: sobrevivência, conversão alimentar aparente, ganho de peso e produção por área. Os parâmetros físico-químicos da água foram avaliados a cada sete dias. O crescimento em peso e em comprimento, aos 60 dias, foi maior na densidade de 200 peixes/m³ do que na de 500 peixes/m³. O coeficiente de variação, a taxa de crescimento específico e a glicose não diferiram entre as densidades aos 30 e 60 dias. A sobrevivência final, a conversão alimentar aparente e o ganho de peso foram iguais em todas as densidades. A produção por área foi significativamente maior nas duas maiores densidades. Os resultados indicaram que a densidade de 400 peixes/m³ é a mais adequada para recria de juvenis de tambaqui em tanque-rede.

O pirarucu é um peixe nativo da bacia Amazônica com respiração aérea obrigatória. Em condições de criação, atinge até 10 kg em um ano, sendo um dos peixes com maior potencial para criação na Amazônia. O objetivo deste estudo foi avaliar as respostas de estresse em pirarucu quando submetido a práticas comuns em sistema de criação. Para isso, foram realizados três diferentes experimentos: 1) transporte; 2) adensamento; e 3) exposição à amônia. Foram analisados parâmetros do metabolismo energético (glicose e lactato), hormonal (cortisol), e de hematologia (hematócrito). Em todos os protocolos testados foram observadas alterações nos parâmetros fisiológicos do pirarucu. As respostas de estresse durante o transporte foram similares às do adensamento, porém, a magnitude das repostas ao adensamento foi maior. A exposição à amônia não causou alteração imediata nos parâmetros fisiológicos, havendo latência nas respostas de estresse. Com os resultados obtidos, pode-se concluir que as alterações nos parâmetros metabólicos ocorrem no momento de maior intensidade de manejo, e provavelmente podem ser reduzidas com adoção de boas práticas na criação.