Banca de DEFESA: RENAN RIBEIRO E SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RENAN RIBEIRO E SILVA
DATE: 15/03/2022
TIME: 09:00
LOCAL: INSTITUTO DE ZOOTECNIA
TITLE:

Median Lethal Concentration for nitrogen compounds in scallops of the species Nodipecten nodosus

KEY WORDS:

Pectinides, Nitrogenates, Toxicity.

PAGES: 33
BIG AREA: Ciências Agrárias
AREA: Zootecnia
SUMMARY:

Aquaculture has increased significantly over the years. In Brazil, the pectinid of the species Nodipecten nodosus stands out among the bivalve molluscs for its zootechnical potential. The availability of high-quality water is essential to guarantee an efficient production, where nitrogenous compounds play a prominent role and lacking of information for N. nodosus. The present study aimed to identify the median lethal concentration (CL50) of nitrogen compounds and to evaluate the presence of gill histological alterations in young forms (seeds) of scallops of the species N. nodosus exposed for 96h. 1500 seeds of N. nodosus were used for pre-tests and experimental design. Pre-tests were performed with concentrations of 3, 6, 12, 20, 35 and 45 mg/L of total ammonia, 25, 50, 100, 500, 600, 750, 900 and 1000 mg/L of nitrite and 100, 500, 1,000, 6,000, 7,500, 9,000 and 10,000 mg/L of nitrate to define the experimental ranges. During the pre-tests, it was not possible to verify the CL50 for nitrite and nitrate at the concentrations tested, not justifying an investigation through an experimental design. The acute toxicity of 96h exposure to ammonia in N. nodosus seeds was investigated in a completely randomized design, using five concentrations of total ammonia, 12, 15, 18, 25, 30 mg/L and the control (0 mg/L) with four replicates for each treatment. For the design, 24 tanks were used filled with a volume of 1L, density of 10 individuals with an average size of 16.15 ± 1.98 mm per tank. The seeds that died during the tests were fixed in buffered formalin diluted in marine water (20%), identified by treatment for histological analysis. The salinity during the test was 30.33 ± 0.42 g/L, the temperature 22.4 ± 0.68 ºC, the dissolved oxygen 5.88 ± 0.27 mg/L and the pH was 8.02 ± 0.68 ºC. 0.08. At the end of exposure for 96h, the mortality rate observed for the control group (0 mg/L) and for concentrations of 12, 15, 18, 25 and 30 mg/L of total ammonia were respectively 7.5, 72, 5, 77.5, 92.5, 100 and 100%. For the toxicity analysis and determination of the 96h LC50 of total ammonia, the TSK Test (Trimmed Spearman-Karber) was used with the elimination of the lower limit. According to the results, the 96h CL50 of total ammonia for the seeds of N. nodosus was estimated at 8.614 mg/L, converting this value to the concentration of toxic ammonia N-NH3 the value is 0.2972 mg/L N- NH3. Histological analysis of gills showed differences between treatments, with the presence of necrosis, hemocytic infiltrate and hyperplasia in animals exposed to concentrations of 18, 25 and 30 mg/L. The tests performed showed that the seeds are resistant to high concentrations of total ammonia and mainly to nitrite and nitrate, since it was not possible to estimate the CL50 for these compounds with the predetermined dosages. Due to these results, the species can be recommended to be used in intensive or super-intensive closed production systems, or even integrated with creations in closed environments with other aquaculture species with high nitrogen load.

BANKING MEMBERS:
Externo à Instituição - PAULO MÁRCIO SANTOS COSTA - FIPERJ
Presidente - 2376201 - LEONARDO ROCHA VIDAL RAMOS
Interno - 3067308 - MATHEUS PEREIRA DOS SANTOS