Changes in lipid composition during metamorphosis of bonefish (Albula sp.) leptocephali.

During metamorphosis of bonefish (Albula sp.) larvae (leptocephali) all energy requirements are provided by breakdown of endogenous compounds, with lipid catabolism accounting for about 80% of total energy production. The principal objective of the present study was to characterize the lipid classes and fatty acids utilized. Analysis of whole-body lipid content indicated that larvae lost about half (3.6 mg) of their total lipid during the 10-d period. Percentages of neutral and polar lipid in early metamorphosing larvae were 64.2 and 35.8%, respectively; these values showed little change during metamorphosis, indicating that both lipid classes were catabolized. Triacylglycerols, the principal neutral lipid of all metamorphic stages, decreased by 1.8 mg, accounting for half of the decrease in total lipid. Levels of phosphatidylethanolamine, the principal polar lipid in early larvae, decreased by more than 50% during metamorphosis; levels of phosphatidylcholine, which was not detected in early larvae, increased. Fatty acids showing the largest net decreases, presumedly used as energy sources, were 16:0 (30.4%), 14:0 (13.8%), 16:1n-7 (12.2%), 20:5n-3 (7.7%), 18:1n-9 (7.4%), and 18:4n-3 (6.9%). Most of 22:6n-3, the second most abundant fatty acid of early larvae, was conserved.

Histological examination of flight muscle development and breakdown in Bemisia tabaci (Homoptera: Aleyrodidae): Relationship to age and flight behvior.

Bemisia tabaci exhibited their longest flights between 3 and 5 days following adult eclosion. They rarely engaged in flight when they were < 4 hr old and were only capable of short-duration flights after day 7. This difference in flight capacity appears to be associated with changes in the flight musculature and mitochondria. Myofibrils and mitochondria accounted for approximately 50% and 33% of the area within the flight muscles, respectively. These two elements, however, varied with the age and sex of the whitefly. The percentage of the total area occupied by myofibrils was lower in 9-day-old males relative to females and all other age categories. Sarcomere length decreased in older whiteflies, regardless of the sex. Myofibril diameter did not vary with the age of the whitefly, but the diameter of female whitefly myofibrils was greater than the diameter of male whitefly myofibrils. The number of myosin filaments within a myofibril unit increased with age, peaking at 5 days of age for females and 7 days of age for males. In all age groups, females had more myosin filaments than were found in males. Changes in mitochondria and levels of glycogen were related to the observed differences in flight activity. The area occupied by mitochondria was small in < 4-h-old and 9-day-old whiteflies, and mitochondrial cristae were undeveloped in newly emerged whiteflies. In 7- and 9-day-old whiteflies the cristae began to separate, leaving visible spaces within the mitochondria. Glycogen granules were abundant in the flight musculature of newly emerged (< 4-hr-old), 1-day-old and 3-day-old whiteflies, but by 5 days of age only 25% of whiteflies contained glycogen granules. Seven- and 9-day-old whiteflies contained no visible glycogen. An examination of the flight muscle of whiteflies after flights of varying duration (up to 60 min) revealed no relationships between flight duration and the number of mitochondria or the percentage of the total area occupied by mitochondria. There was, however, a positive relationship between flight duration and the percentage of total area occupied by myofibrils. © 1995 Wiley-Liss, Inc.

A new procedure for handling impervious biological specimens.

A new application of techniques for preparing impervious biological specimens for light microscopy (LM) and transmission electron microscopy (TEM) has been developed. Microwave irradiation was used to facilitate fixation. A priming technique was used to increase the bonding of the outer surface of the specimens with the resin. Priming the waxy or cuticular surface with Z-6040 (gamma-glycidoxypropyl trimethoxysilane) solved the problem of specimen "pull out" from the resin. Insect specimens with various types of cuticles (waxy or chitinous) and seeds were successfully studied ultrastructurally using this technique.