Modeling the drift of European (Anguilla anguilla) and American (Anguilla rostrata) eel larvae during the year of spawning

The distribution of the leptocephalus larvae of European (Anguilla anguilla) and American (Anguilla rostrata) eels collected during recent Sargasso Sea surveys was used to model larval drift. The drift trajectories of individual larva were back-calculated to the estimated time of spawning, using current data from two global oceanographic assimilation models. The results of both models give the same overall result; widespread spawning extended in time from December to March. The drift was also calculated forwards for approximately 1 year. The forward drift modelling showed that most leptocephali remained in the area south of the Subtropical Frontal Zone. One conclusion is that the majority of leptocephali remain trapped and possibly die in the retention area. A small proportion of leptocephali are entrained into the Gulf Stream system. An implication is that the spawning success may be highly sensitive to oceanographic and climatic factors that alter the dispersion of leptocephali out from the retention area. An alternative interpretation is that the surveys were made too late after the peak spawning period and that the core spawning area was missed.

Growth and Development of Acanthiophilus helianthi (Diptera: Tephritidae) Feeding on Safflower, Carthamus tinctorius

Safflower fly, Acanthiophilus helianthi Rossi (Diptera: Tephritidae), undergoes four stages (egg, larva, pupa and adult) during its growth and development. In this study, observation showed that the egg’s stage took 1.16 ± 0.00, larva’s stage took 12.02 ± 0.13 and pupa’s stage took 7.03 ± 0.08 days before the emergence of adults. The male adult survived for 21.97 ± 2.69 days, while the female lived 19.19 ± 1.50 days. It was observed that the eggs were laid in a cluster, with a range between 10 – 50 eggs per cluster. The length and width of the individual egg were 1.12 ± 0.03 mm and 0.20 ± 0.00 mm respectively. The percentages of the survived individual larva decreased from the first instar until third instar. In the experiment, the length and width of the larva reached 7.77 ± 0.08 mm and 1.84 ± 0.03 mm respectively. Pupae were observed changing in colour from pale white to dark brown. The length and the width of the pupae observed were 6.78 ± 0.16 mm and 2.90 ± 0.02 mm. The longevity of the adults Acanthiophilus helianthi Rossi was influenced by the diets they consumed, the presence of other individuals, wideness of the areas, differences in time taken within the life cycle (between different stages) and temperature in the laboratory.

Hypoderma diana (Diptera, Oestridae) and Lipoptena cervi (Diptera, Hippoboscidae) as parasites of reindeer (Rangifer tarandus) in Scotland with notes on the second-stage larva of Hypoderma diana

Some of the reindeer (Rangifer tarandus) introduced into Scotland from Northern Sweden have become infested with the deer warble fly Hypoderma diana and the deer ked Lipoptena cervi.Evidence is presented which suggests that the larvae of H. diana proceed to their final site on the back of the host by way of the neural canal, and in this way probably caused the deaths of two reindeer in the winter of 1953–4.A detailed analysis is presented of the frequency with which various bands of spines occurred on second-stage larvae of H. diana. An analysis of the number of chitinous rings in the two posterior spiracles on second-stage H. diana larvae showed that in any individual larva the two numbers were not independently determined.On reindeer L. cervi produced puparia in December.

The Time of Action of the Gene Antennaless and Its Effect on the Development of the Cephalic Complex of Drosophila Melanogaster

A. The development of the antenna buds of the mutant antennaless of D. melanogaster has been examined and it is shown that: (1) Prior to about 70 hr., no histological difference is detectable as between normal and abnormal anlagen. (2) Normal antenna buds continue to grow exponentially after 70 hr.; abnormal buds scarcely grow at all. (3) The abnormal bud is also distinguished from wild type by its failure to segment. (4) Both normal (ant. +) and antennaless (ant. -) frontal sacs are everted normally in the pupa. B. The period during which the course of development of antennaless buds of the same genotype could be modified by specific nutritional substances was also determined. It is shown that media containing a high concentration of dextrose will induce a lowered exhibition. By transferring larvae from normal media to media of high dextrose content, it is found that the course of development of the antenna bud cannot be modified after about the 80th hr. of larval life. These experiments suggest that the effective period of the gene is relatively short and is probably not more than 12 hr. for each individual larva. This period corresponds to the T.E.P., but is not necessarily identical with ‘the time of action of the gene’.