Morfologia, morfometria, distribuição de células mucosas e de cloreto em embriões e larvas de jundiá, Rhamdia quelen (Heptapteridae). Efeito do pH e concentração de cálcio e magnésio da água.
Fecha
2006-05-26Autor
Silva, Lenise Vargas Flôres da
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The ions Ca2+, Mg2+ and the water pH influence the morphological and morphometric
characters and also in the ionic regulation of fish. The objective of this study was describe the
morphological and morphometric development pattern of Rhamdia quelen embryo and larvae;
and to identify and determine the distribution of mucous and chloride cells in order to
evaluate the effect of water pH and hardness in different Ca2+ and Mg2+ concentration. After
fertilization the eggs were maintained at water pH 7.0 and 8.0 with three different Ca2+: Mg2+
concentrations (mg L-1): hardness 20 mg L-1 CaCO3 (5.0 Ca2+: 2.08 Mg2+, control) and
hardness 70 mg L-1 CaCO3 (20 Ca2+:5.59 Mg2+ and 23 Ca2+: 2.08 Mg2+) at 24±1oC. The eggs
(24 h post fertilization- hpf) and larvae (each 6 hours) 6 to 48 and 216 h post hatchery (hph)
were collected to analyze the hatching rate, survival and larvae growth, morphological and
morphometrics characters associates the vision (eye), feeding (development and functionality
digestive tract) and swimming abilities (fins), the distribution of mucus and chloride cells,
Na+/K+-ATPase activity enzyme, and whole body ionic content in embryo and larvae
homogenate. The fertilization, hatching rate, post-hatch survival, weight and length (48 and
216h) were higher in pH 8,0 and did not show significance difference related with Ca2+: Mg2+
concentrations. These suggest that the pH 8.0 is indicated to Rhamdia quelen larvae culture.
The increase of water hardness to 70 mg L-1 CaCO3, mainly 20 mg L-1 Ca2+ and 5,59 mg L-1
Mg2+ concentrations is recommended to both pH device improve the total body area larvae.
The increase of hardness with 23 mg L-1 Ca2+, is not adequate for Rhamdia quelen larvae, as
this Ca2+ concentration occurs an ionic unbalance Na+ and Cl- in both pHs. However, the
morphology did not change by pH and Ca2+: Mg2+ concentrations used. The developmental
stage between 6-216 hph was considered as critic period, device the development of
osmorregulatory structures (gills, intestine and kidney) and the necessary changes to begin the
exogenous feeding (open mouth, digestive tract, urogenital hole). Therefore, it is important
information to researches and/or fisheries to improve the techniques and handlings for
Rhamdia quelen early stages larvae culture to optimize the environmental conditions. The
mucous cell density show a relation with water Ca2+ concentration, and it is suggest that
beyond the possible adaptive responses, apparently the mucous cells number in silver catfish
larvae (Rhamdia quelen) are influenced by hardness (Ca2+ increases) and water pH in the
early phases. The larvae cultivated in pH 7.0 show high mucous cell and chloride cell number
than in pH 8.0. The water hardness 70 mg L-1 CaCO3 (independently Ca2+ and Mg2+
concentration) changed the chloride cell density in the first hours post hatchery (6-12 h), and
the number of these cells was lower in both pHs. Then, these results suggest that the mucous
and chloride cell number can be modulated by ionic environmental condition in the early
develpment of silver catfish larvae after hatchery. The thesis was organized in chapters, a
general introduction and the objectives, and it was followed by chapter 1 about morphology
and morphometry of embryo and larvae, chapter 2 about the distribution of mucous cells and
chapter 3 about the distribution the chloride cells of silver catfish (Rhamdia quelen) embryo
and it was with an integrated synthesis of study, the general conclusions and finish
considerations.