Cost-benefit of feeding on anthropogenic organic matter: lipid changes in a detritivorous fish (Prochilodus lineatus)

The lipid composition of muscle and liver of detritivorous fish Prochilodus lineatus, settling particles and sediments from reference and polluted areas of the Paraná-Rio de la Plata basin were analyzed to evaluate the impact of feeding on contaminated detritus. Overall, muscular lipids were highly variable (14 ± 13 % wet mass, ww) and increased with body mass trough a rapid triglyceride accumulation [82 ± 7.9 % neutral lipids (NL) for fish weighing less than 1 kg to 99 ± 0.51 % NL for fish weighing more than 4 kg] with a parallel decrease of free fatty acid (13 ± 6.0 to 0.11 ± 0.23 % NL). Liver lipids were more uniform (6.0 ± 2.1 % ww) and were dominated by triglycerides (40 ± 21 % NL) and free fatty acids (34 ± 19 % NL). Compared with fish from reference areas in the North, polluted fish from Buenos Aires presented higher muscular lipid contents (24 ± 13 vs. 3.9 ± 3.1 % ww) and triglyceride abundance (98 ± 3.5 vs. 84 ± 9.7 % NL), and enlarged livers (Hepatosomatic index 1.4 ± 0.4 vs. 0.7 ± 0.2) enriched with esterified cholesterol (20 ± 9.1 vs. 11 ± 9.9 % NL). These differences were consistent with the higher proportions of lipids, enriched with free fatty acids and triglycerides, in stomach contents, settling particles and sediments from Buenos Aires relative to the North of the basin. The change in Prochilodus lineatus diet from organic-poor vegetal detritus in the north to polluted but abundant and fresh anthropogenic matter at Buenos Aires resulted in multiple alterations of lipid metabolism.     

Mating Behavior of Southern Stingrays, Dasyatis americana (Dasyatidae)

We document in detail the first complete sequence of mating events in the southern stingray, Dasyatis americana, based on observations of four matings (five separate copulations) at Grand Cayman, British West Indies and Bimini, Bahamas. These observations are significant because almost nothing is known about this important aspect of the life cycle of batoids, due to the rarity of encounters with mating animals in natural settings. Similar to mating behavior described in the manta ray, Manta birostris, the mating sequence of D. americana can be characterized as (1) 'close-following', (2) 'pre-copulatory biting', (3) 'insertion/copulation', (4) 'resting' and (5) 'separation'. Additional information gained from these observations includes the fact that (1) two of the females were mated very shortly (i.e. within minutes–hours) after parturition and (2) one of the mating events involved a single female that copulated (unforced) with two males in rapid succession. The latter observation suggests that polyandry and multiple paternity may be elements of the mating system of D. americana.     

Fetal and maternal thyroid hormones

It is well known that insufficient production of thyroid hormones during the fetal and neonatal period of development may result in permanent brain damage unless treatment with thyroid hormone is instituted very soon after birth. But congenital hypothyroidism is not the only situation in which brain damage may be related to insufficient thyroid function. Cretinism is the most severe manifestation of iodine deficiency disorders found in areas where iodine intake is greatly reduced. Some of the manifestations of cretinism suggest that the insult to the developing brain starts earlier than in the case of congenital hypothyroidism. Hypothyroxinemia of mothers with adequate iodine intake may also leave permanent, though less severe, mental retardation. For these reasons the possible role of maternal transfer of thyroid hormones during early fetal development have been reinvestigated, using the rat to obtain various experimental models. It has been shown that thyroid hormones are found in embryonic tissues before onset of fetal thyroid function and that thyroidectomy of the mother results in delayed development of the concepta. The concentrations of T4 and T3 in embryonic tissues from thyroidectomized dams were undetectable before the onset of fetal thyroid function, and still reduced in some tissues near term, despite the onset of fetal thyroid function. Treatment of control and thyroidectomized dams with methyl-mercaptoimidazole to block fetal thyroid function reduced thyroid hormone concentrations in fetal tissues near term, but this decrease could be partially avoided by infusion of physiological doses of thyroxine to the mothers. Iodine deficiency of the mothers resulted in thyroid hormone deficiency of the developing embryo, which was very marked until term in all tissues including the brain. The results strongly support a role of maternal thyroid hormones in fetal thyroid hormone economy both before and after the onset of the fetal thyroid function, at least in the rat. They also support a role of the hypothyroxinemia of iodine-deficient mothers in initiating the brain damage of the endemic cretin, a damage which would not be corrected once the fetal thyroid becomes active, as iodine-deficiency of the fetus would impair adequate production of hormones by its own thyroid, and maternal transfer would continue to be low.     

High-Performance liquid chromatography (HPLC) chiral separations of guaifenesin,methocarbamol, and racemorphan

HPLC chiral separations on silica gel coated with derivatized cellulose stationary phases are described. Most examples make use of the Chiralcel OD column from Daicel, Inc. With a judiciously chosen mobile phase, baseline separations of the enantiomers can be achieved. If those separations are used as a base for enantiomeric purity determination, detectable limits of 0.1% of the minor enantiomer are routinely accessible. Examples are given concerning separations of guaifenesin, methocarbamol, and racemorphan. © 1993 Wiley-Liss, Inc.