The physiological transition to aerial breathing in larval air-breathing fishes is poorly understood. We investigated gill ventilation frequency (f), heart rate (f), and air breathing frequency (f) as a function of development, activity, hypoxia, and temperature in embryos/larvae from day (D) 2.5 to D30 posthatch of the tropical gar, Atractosteus tropicus, an obligate air breather. Gill ventilation at 28°C began at approximately D2, peaking at ∼75 beats/min on D5, before declining to ∼55 beats/min at D30. Heart beat began ∼36-48 h postfertilization and ∼1 day before hatching. f peaked between D3 and D10 at ∼140 beats/min, remaining at this level through D30. Air breathing started very early at D2.5 to D3.5 at 1-2 breaths/h, increasing to ∼30 breaths/h at D15 and D30. Forced activity at all stages resulted in a rapid but brief increase in both f and f, (but not f), indicating that even in these early larval stages, reflex control existed over both ventilation and circulation prior to its increasing importance in older fishes. Acute progressive hypoxia increased f in D2.5-D10 larvae, but decreased f in older larvae (≥D15), possibly to prevent branchial O loss into surrounding water. Temperature sensitivity of f and f measured at 20°C, 25°C, 28°C and 38°C was largely independent of development, with a Q between 20°C and 38°C of ∼2.4 and ∼1.5 for f and f, respectively. The rapid onset of air breathing, coupled with both respiratory and cardiovascular reflexes as early as D2.5, indicates that larval A. tropicus develops "in the fast lane."
This study is a first report of rotifer form the South of Mexico. The rotifers were collected from the fishponds arround Biological Division, UJAT and we examined their morphometric characters, cultivated and identified them. We conducted experiment at different salt concentrations tested at 0g L–1 water (no add NaCL), 2g L–1, 4g L–1, 6g L–1, 8g L–1, 10g L–1 water. The species were identified as Brachionus angularis Gosse (1851) characterized by having two anterior spines, which are almost invisible while B. quadridentatus brevispinus Ehrenberg (1832) with six anterior spines, which can be seen clearly. Lorica size of B. angularis and B. quadridentatus brevispinus are about 12.14 and 12.8 m, respectively and the size is much smaller than B. plicatilis (Mazatlan strain).
Se efectuó un bioensayo en larvas del "Atractosteus tropicus", para lo cual se seleccionaron un total de 1,054 individuos con un peso y longitud inicial de (0.08±0.01 g y 26.0±3.0 mm respectivamente) aplicando un diseño bifactorial, donde el primer factor fueron los dos tipos de aceites; vegetal (Patrona, Edo. Mex) y sardina, el segundo factor fueron los dos niveles de lípidos 10 y 15%, más la dieta control comercial para trucha, (Silver Cup®) con 45% de proteína y 16% de lípidos, evaluados por triplicado con una duración de 28 días. Los resultados mostraron que las larvas alimentadas con la dieta (SOL10%) y aceite de pescado con 15% de lípidos (SOL15%), fueron estadísticamente diferentes entre sí y las que mejores pesos y longitudes totales obtuvieron (3.76±0.55 g y 12.13±1.25 mm; 1.46±0.37 g; 7.31±0.67mm) contra las larvas alimentadas con las dietas de control y aceites vegetales (CDPL16%, VOL10% y VOL15% de lípidos). Por lo que se concluye que en la alimentación de las larvas de "A. tropicus" se debe usar aceite de sardina, aunque la utilización de aceites vegetales es posible, no obstante probablemente en menor cantidad.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.