ABSTRACT At inadequate stocking density, fish generally show different physiological responses. The effects of stocking density on Arapaima gigas larvae productive parameters have been determined in a previous study. This study aimed to evaluate the effect of the stocking density on the water quality, hematological and biochemical profile, and productive performance of juvenile A. gigas. One hundred and eighty twelve months old, A. gigas were distributed into tanks using initial densities of 103.90, 157.95 and 220.11 kg m-3 with three replicates. Ammoniacal nitrogen, carbon dioxide, dissolved oxygen pH, alkalinity, and hardness were determined using a LaMotte Fish Farm 9, AQ-2 model, Maryland, USA, freshwater test kit. Blood samples were taken at 13, 14, and 15 months old by pricking the caudal vein and profiles of glucose (Glu), total protein (TP), albumin, aspartate transaminase (AST), alanine transaminase (ALT), and urea, were determined in blood serum. Rearing water was saturated in ammoniac nitrogen, carbon dioxide, and dissolved oxygen but have not changed with the increase of stocking density (P < 0.05), Erythrocyte's count (EC) diminished (P < 0.05), nonetheless, hemoglobin, mean concentration hemoglobin (MCH) and mean cell volume (MCV) increased (P < 0.05). Albumin, AST, ALT and urea diminished at 220.11 kg m-3 stocking density (P < 0.05). The feed intake increased, final biomass gain was 100.26 ± 19.00, 119.10 ± 13.95, and 130.24 ± 08.07 kg m-3, but did not change as density increased (P < 0.05). Juveniles of A. gigas showed no variation in productive performance with an increase in the stocking density. Furthermore, hematological and biochemical adapting profile to high stocking densities characterized this species.

Este estudo caracterizou morfologicamente Trichodina heterodentata Duncan, 1977 de alevinos de "pirarucu" Arapaima gigas cultivados no Peru. Esfregaços do corpo e brânquias foram secos à temperatura ambiente, impregnados com nitrato de prata e/ou corados com tricrômico de gômori. A prevalência foi de 100%. Trichodina heterodentata foi considerada um tricodinídeo de tamanho médio com diâmetro médio do corpo de 56,0+ 5,25 (47,3-76,0) μm, anel denticulado 28,21± 2,71 (20,0-34,7) μm, disco adesivo 45,7±3,8 (37,1-57,3) μm de diâmetro e número de dentículos de 20,7± 2,6 (12-24). O presente estudo registra não somente a primeira ocorrência de T. heterodentata no Peru mas também o primeiro registro do tricodinídeo parasitando A. gigas. Tabelas comparativas biométricas de todos os registros de T. heterodentata também são apresentados.

This study characterized morphologically Trichodina heterodentata Duncan, 1977 from cultivated fingerlings of "pirarucu" Arapaima gigas in Peru. Body and gill smears were air-dried at room temperature, impregnated with silver nitrate and/or stained with gomori trichromic. Prevalence was 100%. Trichodina heterodentata was considered a medium-sized trichodinid with mean body diameter of 56.0+ 5.25 (47.3-76.0) μm, denticulate ring 28.21± 2.71 (20-34.7) μm, adhesive disc 45.7±3.8 (37.1-57.3) μm diameter and number of denticles of 20.7± 2.6 (12-24). The present study reports not only the first occurrence of T. heterodentata in Peru but also the first record of this trichodinid infesting A. gigas. Camparative tables of all reports of T. heterodentata are also presented.