Tank color influences the response of tomato clownfish (Amphiprion frenatus) to an acute stress challenge.

The trade of aquarium organisms is growing worldwide. This market depends on a continuous supply of healthy and colorful aquatic animals, but this sector has few initiatives. However, in the last decade, there has been a growing interest in researching captive breeding of these animals, aiming to develop a more sustainable aquarium hobby. Larviculture is an important phase in the cultivation process because the larvae are more sensitive to stress and variations in the bulk of variables, such as temperature, salinity, nutritional management, light intensity and spectrum, and environmental background colors. Because background color could be a promoter variable of proper welfare, we tested whether it affects the endocrine response of tomato clownfish Amphiprion frenatus larvae to an acute stress challenge. We show that background color influences the endocrine stress axis responsiveness in tomato clownfish. When fish were subjected to a standard acute stressor of 61 days after hatching, only fish adapted to white walls increased the whole-body cortisol levels. From the results presented herein, we recommend that white tanks be avoided for A. frenatus larviculture. Both, the less stress level and the good welfare condition of larvae reared in colored tanks may have robust, practical applications since almost all clownfish in the ornamental aquarium trade come from captive breeding.

Spawning, egg and larval description of the brazilian basslet Gramma brasiliensis Sazima, Gasparini & Moura, 1998 in captivity.

Brazilian basslet Gramma brasiliensis is a fish highly appreciated by the marine ornamental industry. There is an increasing interest in the development of a breeding protocol for this species. However, descriptions of the reproductive biology, eggs and larval development are scarce. This study was the first to describe the spawning, eggs and larvae of G. brasiliensis in captivity, including mouth size information. Six spawning events produced egg masses with 27, 127, 600, 750, 850, and 950 eggs. Larger egg masses showed embryos with at least two different developmental stages. Eggs are spherical (∼1.0 mm diameter), held together by filaments entangling chorionic projections. Larvae with fewer than 12 hph (hours post-hatch) presented 3.55 mm standard-length, well developed eyes, fully absorbed yolk sac, an inflated swim bladder and mouth opened. Exogenous feeding on rotifers began within 12 hph. The average mouth width at first feeding was 0.38 mm. The first settled larva was noted by day 21. This information should help to determine appropriate diets and prey-shift time during the larviculture of the species.

Embryonic and early larval development of two marine angelfish, Centropyge bicolor and Centropyge bispinosa.

Marine angelfish (family: Pomacanthidae) are among the most sought-after fish species in the saltwater aquarium trade. However, there is a lack of information in the literature on their early ontogeny. The objective of this study was to describe the embryonic and early larval development of two dwarf angelfish, the bicolour angelfish, Centropyge bicolor and the coral beauty angelfish, Centropyge bispinosa. The eggs of these two species were obtained from spontaneous spawning of the broodstock fish in captivity and incubated at 26.0 ± 0.2°C throughout the study. Fertilized eggs (n = 15) of both species are transparent, pelagic and spherical; the mean diameters of the eggs were measured at 703.6 ± 7.8 µm for C. bicolor and 627.6 ± 7.8 µm for C. bispinosa. The eggs of both species possessed a narrow perivitelline space, smooth and thin chorion, a homogenous and non-segmented yolk as well as a single oil globule. Overall, the observed embryonic development pattern of C. bicolor and C. bispinosa was very similar, and the main difference was the embryonic pigmentation pattern, which only became evident close to hatching. Larvae of both species started hatching at 13 h 30 min after fertilization, and the larval characteristics of both species also showed high levels of similarities. However, the mouth opening time for C. bicolor was 72 h after hatching (AH) and 96 AH for C. bispinosa. In general, the observed early ontogeny of C. bicolor and C. bispinosa also resembled that of other Centropyge species documented in the literature.

Thermal influence on the embryonic development and hatching rate of the flameback pygmy angelfish Centropyge aurantonotus eggs.

The flameback pygmy angelfish Centropyge aurantonotus, highly appreciated and valued by the aquarium market, is heavily harvested and traded. Temperature is one of the abiotic factors that has the most influence on fish development, especially in the early stages of life. For captive production, it is essential to know the appropriate environmental parameters for each species. In this sense, this study aimed to evaluate the influence of temperature on the embryonic development and hatching rates of C. aurantonotus incubated at six different temperatures (20, 22, 24, 26, 28, 30°C). Embryonic development events were very similar in terms of morphological and chronological characteristics compared with other species of the genus Centropyge. Incubation time was inversely proportional to temperature. The treatment at 22°C required twice the time of that required by 30°C treatment for hatching to occur. The best incubation temperature range was 24-28°C. Values below 22°C and at 30°C showed lower hatching rates compared with other treatments. Based on these results, the recommended temperature at which to incubate C. aurantonotus eggs is between 24-28°C.

Development and health status of Centropomus undecimalisparasitized by Rhabdosynochus rhabdosynochus (Monogenea) under different salinity and temperature conditions.

This study evaluated the correlation of hematological parameters with the mean abundance of the monogenean helminth Rhabdosynochus rhabdosynochus in Centropomus undecimalis reared at different temperatures and salinities. The experimental conditions were: 28 °C/0 ppt (parts per thousand); 28 °C/15 ppt; 28 °C/32 ppt; 25 °C/0 ppt; 25 °C/15 ppt; and 25 °C/32 ppt. The prevalence was 100.0% in fish at 28 °C/15 ppt, 28 °C/32 ppt and 25 °C/15 ppt, which was significantly different (p < 0.05) from those at 25 °C/32 ppt. The red blood cell (RBC) count, hematocrit and total leukocyte (WBC) count were significantly higher in fish at 28 °C/15 ppt and 28 °C/32 ppt. The mean abundance of R. rhabdosynochus, hematocrit and RBC showed positive correlations (P < 0.05) with temperature (ρ= 0.3908; ρ= 0.4771 and ρ = 0.2812). Mean abundance showed negative correlations with hemoglobin (ρ= -0.3567) and mean corpuscular hemoglobin concentration (MCHC) (ρ = -0.2684). No correlation between abundance and salinity was detected among the experimental conditions (ρ = -0.0204). The low numbers of monogeneans recorded (min -1 and max -33) explain the few changes to fish health. This suggests that these experimental conditions may be recommended for development of rearing of C. undecimalis in Brazil, without any influence or economic losses from R. rhabdosynochus.

Development and health status of Centropomus undecimalisparasitized by Rhabdosynochus rhabdosynochus (Monogenea) under different salinity and temperature conditions / Desenvolvimento e estado de saúde de Centropomus undecimalisparasitado por Rhabdosynochus rhabdosynochus (Monogenea) sob diferentes condições de salinidade e temperatura

This study evaluated the correlation of hematological parameters with the mean abundance of the monogenean helminth Rhabdosynochus rhabdosynochus in Centropomus undecimalis reared at different temperatures and salinities. The experimental conditions were: 28 °C/0 ppt (parts per thousand); 28 °C/15 ppt; 28 °C/32 ppt; 25 °C/0 ppt; 25 °C/15 ppt; and 25 °C/32 ppt. The prevalence was 100.0% in fish at 28 °C/15 ppt, 28 °C/32 ppt and 25 °C/15 ppt, which was significantly different (p < 0.05) from those at 25 °C/32 ppt. The red blood cell (RBC) count, hematocrit and total leukocyte (WBC) count were significantly higher in fish at 28 °C/15 ppt and 28 °C/32 ppt. The mean abundance of R. rhabdosynochus, hematocrit and RBC showed positive correlations (P < 0.05) with temperature (ρ= 0.3908; ρ= 0.4771 and ρ = 0.2812). Mean abundance showed negative correlations with hemoglobin (ρ= -0.3567) and mean corpuscular hemoglobin concentration (MCHC) (ρ = -0.2684). No correlation between abundance and salinity was detected among the experimental conditions (ρ = -0.0204). The low numbers of monogeneans recorded (min -1 and max -33) explain the few changes to fish health. This suggests that these experimental conditions may be recommended for development of rearing of C. undecimalis in Brazil, without any influence or economic losses from R. rhabdosynochus.

Este estudo avaliou a correlação dos parâmetros hematológicos com a abundância média de helmintos monogenea Rhabdosynochus rhabdosynochus em robalo-flecha, Centropomus undecimalis, cultivado em diferentes temperaturas e salinidades. As condições experimentais foram: 28 °C/0 ‰; 28 °C/15 ‰; 28 °C/32 ‰; 25 °C/0 ‰; 25 °C/15 ‰; 25 °C/32 ‰. A prevalência (P) foi de 100,0% nos peixes de 28 °C/15 ‰, 28 °C/32 ‰, 25 °C/15 ‰ significativamente diferente (p<0,05) dos peixes de 25 °C/32 ‰ (P=75,0%). O número de eritrócitos, hematócrito e leucócitos totais foram significativamente maiores nos peixes mantidos a 28 °C/15 ‰ e 28 °C/32 ‰. A abundância média de R. rhabdosynochus, hematócrito e número de eritrócitos mostraram correlação positiva (p<0,05) com a temperatura (ρ = 0,3908; ρ = 0,4771 e ρ = 0,2812, respectivamente). Houve correlação negativa da abundância média com a hemoglobina (ρ = -0,3567) e a concentração de hemoglobina corpuscular média (CHCM) (ρ = -0,2684). Não houve correlação entre a abundância e a salinidade entre os tratamentos (ρ = -0,0204). O baixo número de Monogenea registrado (mín: 1 e máx: 33) justifica as poucas alterações na saúde dos animais avaliados. Isso sugere que essas condições experimentais de cultivo podem ser recomendadas para um futuro desenvolvimento do cultivo de C. undecimalis no Brasil, sem que haja influência e perdas econômicas associadas a mortalidades, por parasitos R. rhabdosynochus.

Outbreak of mortality among cage-reared cobia (Rachycentron canadum) associated with parasitism / Surto de mortalidade em bijupirá (Rachycentron canadum) criado em tanque-rede associado ao parasitismo

This study reports a disease outbreak among juvenile cobia (Rachycentron canadum) farmed in cages in the state of Rio de Janeiro, Brazil, caused by the dinoflagellate Amyloodinium ocellatum and the monogenean Neobenedenia melleni. Two thousand five hundred fish were stocked at 0.4 kg/m3 in a set of 12 m3 tanks, in autumn (mean weight 15.0 ± 7.3 g) and in winter (mean weight 43.0 ± 5.6 g). Freshwater baths were administered as a routine treatment, as the symptoms were detected followed by two collection samples. Firstly in May 2011 (n = 5) and secondly in September 2011 (n = 10). In the first sample, the prevalence of N. melleni on the body surface was 100% and the mean intensity was 42.0 ± 1.7, while in the second sample the prevalence was 60% with a mean intensity 3.0 ± 0.2 and mean abundance 1.8 ± 0.4. Amyloodinium ocellatum was only found in the second sample, at a prevalence 100% and mean intensity 46.8 ± 3.4. The cause of fish mortality was possibly associated with a decrease in fish resistance after the first contact with monogenean parasites, allied with respiratory difficulty caused by the presence of A. ocellatum in the gills.

Este estudo relata a mortalidade em massa de juvenis de bijupirá (Rachycentron canadum) criados em tanques-rede no estado do Rio de Janeiro, Brasil, causada pelo dinoflagelado Amyloodinium ocellatum e o monogenea Neobenedenia melleni. Dois mil e quinhentos peixes estavam estocados à densidade de 0,4 kg/m3 em tanques-rede de 12 m3, no período do outono (15,0 ± 7,3 g; peso médio ± DP) e inverno (peso médio de 43,0 ± 5,6 g). Banhos de água doce foram realizados rotineiramente à medida que os sintomas eram detectados, quando então, foram efetuadas duas colheitas, sendo a primeira em maio de 2011 (n = 5) e a segunda em setembro de 2011 (n = 10). Na primeira colheita, a prevalência de N. melleni foi de 100% e a intensidade média de 42,0 ± 1,7, e na segunda, a prevalência foi de 60% e intensidade média de 3,0 ± 0,2 e abundância média de 1,8 + 0,4. Na segunda colheita, observou-se a presença de A. ocellatum (prevalência de 100%, intensidade média de 46,8 ± 3,4). Possivelmente, a causa da mortalidade estava relacionada à redução na resistência dos peixes após o primeiro contato com o parasito monogenea, juntamente com a dificuldade respiratória causada pelo dinoflagelado nas brânquias.

Monoculture of the ciliate protozoan Euplotes sp. (Ciliophora; Hypotrichia) fed with different diets / Monocultivo do protozoário ciliado Euplotes sp. (Ciliophora; Hypotrichia) com diferentes dietas

Ciliate protozoa of the genus Euplotes commonly appears contaminating mass cultures of rotifers but also with potential to be used as live food in the larviculture of marine fish. To obtain a monoculture of Euplotes sp., three diets were tested: 1) microalgae Nannochloropsis oculata, 2) commercial diet for rotifers Culture Selco 3000, and 3) baker's yeast (Saccharomyces cerevisiae). The ciliates were inoculated at 10 ind. mL -¹. On day 5, protozoa densities in the groups fed the commercial diet (1,911.0 ± 248.7 ind. mL-¹) and the baker's yeast (2,600.0 ± 195.3 ind. mL-1) did not differ, but were higher than the group fed microalgae (2.0 ± 1.4 ind. mL-1) (p < 0.05). On day 6, the density in the group fed baker's yeast was higher (15,484.0 ± 1,164.9 ind. mL-¹) than in the groups fed microalgae (3.0 ± 1.4 ind. mL-¹) or commercial diet (11,287.0 ± 1,468.0 ind. mL-¹). An exponential growth curve was observed for the protozoa fed baker's yeast (R² = 0.992; p < 0.05) and commercial diet (R² = 0.979; p < 0.05). The microalgae diet did not result in satisfactory growth of the protozoan. Feeding baker's yeast or commercial rotifer's diet to a monoculture of Euplotes sp. can result in very high densities of this protozoan.

Protozoários ciliados do gênero Euplotes comumente aparecem como contaminante em culturas massivas de rotíferos, apresentando potencial para ser utilizado na larvicultura de peixes marinhos. Para obter um monocultivo de Euplotes sp., foram testados três tipos de alimento: 1) microalga Nannochloropsis oculata, 2) dieta comercial para rotíferos Culture Selco 3000, e 3) fermento biológico (Saccharomyces cerevisiae). Os ciliados foram inoculados na concentração de 10 indivíduos mL-¹. No quinto dia, a densidade de protozoários nos tratamentos com dieta comercial para rotíferos (1.911,0 ± 248,7 ind. mL-¹; média ± desvio padrão) e fermento biológico (2. 600,0 ± 195,3) não diferiram entre si, mas foram superiores ao tratamento com microalga (2,0 ± 1,4) (p < 0,05). Ao sexto dia de cultivo, a densidade no tratamento com fermento (15.484,0 ± 1.164,9 ind. mL-¹) foi superior aos tratamentos com microalga (3,0 ± 1,4 ind. mL-¹) e dieta comercial (11.287,0 ± 1.468,0 ind. mL-¹). O cultivo destes ciliados apresentou uma curva de crescimento exponencial para o fermento (R² = 0,992; p < 0,05) e a dieta comercial (R² = 0,979; p < 0,05). O uso da microalga N. oculata não resultou em crescimento satisfatório destes organismos. O uso de fermento biológico e dieta comercial para rotíferos no monocultivo de Euplotes sp., pode resultar em altas densidades do protozoário.

Outbreak of mortality among cage-reared cobia (Rachycentron canadum) associated with parasitism.

This study reports a disease outbreak among juvenile cobia (Rachycentron canadum) farmed in cages in the state of Rio de Janeiro, Brazil, caused by the dinoflagellate Amyloodinium ocellatum and the monogenean Neobenedenia melleni. Two thousand five hundred fish were stocked at 0.4 kg/m3 in a set of 12 m3 tanks, in autumn (mean weight 15.0 ± 7.3 g) and in winter (mean weight 43.0 ± 5.6 g). Freshwater baths were administered as a routine treatment, as the symptoms were detected followed by two collection samples. Firstly in May 2011 (n = 5) and secondly in September 2011 (n = 10). In the first sample, the prevalence of N. melleni on the body surface was 100% and the mean intensity was 42.0 ± 1.7, while in the second sample the prevalence was 60% with a mean intensity 3.0 ± 0.2 and mean abundance 1.8 ± 0.4. Amyloodinium ocellatum was only found in the second sample, at a prevalence 100% and mean intensity 46.8 ± 3.4. The cause of fish mortality was possibly associated with a decrease in fish resistance after the first contact with monogenean parasites, allied with respiratory difficulty caused by the presence of A. ocellatum in the gills.

Effect of salinity on the oxygen consumption of larvae of the silversides Odontesthes hatcheri and O. bonariensis (Osteichthyes, Atherinopsidae)

Starved larvae of the silversides O. hatcheri (2- and 5-days-old) and Odontesthes bonariensis (5-days-old) were used to compare the oxygen consumption rates at 0, 5, 10, 20 and 30 ppt salinity. Oxygen consumption of O. hatcheri and O. bonariensis was minimal at 0 and 10 ppt, respectively, salinities close to those encountered in areas inhabited by these fishes. In both species, oxygen consumption rates thereafter increased with increasing salinity, and then abruptly decreased at 30 ppt. Lower consumption at extreme salinities might be a result of reduced activity, which in itself was salinity-modulated. Differences in activity may explain the fact that oxygen consumption rates of 5-day-old larvae were higher than 2-day-old larvae, which still possess yolk-sac. In this case, starved larvae incurred in higher metabolic demand due to the continuous swimming in the search for food.

As larvas em inanição de peixe-rei O. hatcheri (2 e 5 dias de idade) e Odontesthes bonariensis (5 dias de idade) foram usadas para comparar as taxas de consumo de oxigênio em salinidades de 0, 5, 10, 20 e 30 ppt. As taxas de consumo de oxigênio de O. hatcheri e O. bonariensis foram mínimas a 0 e 10 ppt, respectivamente, salinidades próximas aquelas encontradas nas áreas onde estes peixes habitam. Em seguida, em ambas as espécies, as taxas de consumo de oxigênio aumentaram com o incremento da salinidade, e abruptamente caíram a 30 ppt. As taxas de consumo mais baixas em salinidades extremas podem ser resultado da atividade reduzida, sendo portanto modulada pela salinidade. Diferenças na atividade possivelmente explicam o fato das taxas de consumo de oxigênio de larvas de 5 dias de idade serem maiores em comparação a larvas de 2 dias, ainda com saco vitelínico. Neste caso, larvas em inanição impõem um maior gasto metabólico devido a natação contínua em busca de alimento.