End Product Inhibition of Serotonin Synthesis in the Rat Striatum

THE synthesis of serotonin (5-HT) in central serotoninergic neurones seems to depend on the intraneuronal concentrations of the amine. After acute or chronic treatment with a monoamine oxidase inhibitor (MAOI), which induced more than a three-fold increase in 5-HT concentrations, we observed a reduced formation of ³H-5-HT from ³H-tryptophan in the rat brain¹. More precisely, this effect could be seen by measuring the accumulation of ³H-5-HT in tissues 15 min after the intracisternal injection of ³H-tryptophan at various times after pheniprazine or pargyline treatments. The ³H-amine accumulation was much less after 3 h than 0.5 h after the MAOI injections. The existence of a 5-HT synthesis regulation by end product inhibition occurring at the first limiting step was proposed to explain these results¹.     

Comparative day and night feeding strategies of shorebird species in a tropical environment

A study was carried out in northeastern Venezuela to determine whether or not shorebirds feed at night in tropical environments. Results show that some Neotropical residents and Nearctic winter migrants feed during darkness. During daylight, Black-winged Stilts Himantopus himantopus, mexicanus group, were predominantly visual foragers (75% attempts were pecking), performing a tactile type of feeding technique (immersion of the whole head and portion of the neck while searching for food through soft mud) on other occasions. During night-time, they were almost equally visual (pecking) and tactile (multiple scythelike sweeps) foragers. Greater and Lesser Yellowlegs Tringa melanoleuca and T. flavipes foraged visually during daylight and tactilely (sidesweeping) at night. Short-billed Dowitchers Limnodromus griseus were tactile feeders (probers) both by day and by night while Semipalmated Plovers Charadrius semipalmatus during daylight and at night and Wilson's Plovers C. tvilsonia by night were sight feeders (peckers). Prey abundance was higher at night than during daylight. Black-winged Stilts and yellowlegs seemed to feed at night on food items at least partly different from those they fed upon during daylight.     

Maternal attendance and the maintenance of family groups in common earwigs (Forficula auricularia): a field experiment

Abstract.  1. Understanding the evolution of subsocial behaviour and parental care requires experimental tests of the functional significance of such behaviours and the role of tending parents in the maintenance of family groups. Studies in subsocial insects addressing these issues experimentally and in the field are still relatively rare.
2. In such a field experiment, it is demonstrated here that the presence of tending females enhances the maintenance of family groups in common earwigs, Forficula auricularia (Dermaptera; Forficulidae). Experimental removal of tending mothers resulted in substantially decreased recovery of occupied nest burrows and larvae. This effect may have been because of decreased survival among experimental larvae, although a possible role for enhanced larval dispersal could not be fully ruled out.
3. Experimental (motherless) larvae were partly observed in family groups with a tending female, in both experimental and control nest burrows, suggesting that these larvae had been adopted by family groups moving to new nest burrows, and/or that experimental larvae may have actively joined other family groups.
4. This study demonstrates under field conditions the functional importance of maternal attendance for the maintenance of family groups in common earwigs, and suggests that adoption and clutch-joining are factors affecting the social structure of this species.     

A biological consequence of reducing Arctic ice cover: arrival of the Pacific diatom Neodenticula seminae in the North Atlantic for the first time in 800 000 years

The Continuous Plankton Recorder survey has monitored plankton in the Northwest Atlantic at monthly intervals since 1962, with an interegnum between 1978 and 1990. In May 1999, large numbers of the Pacific diatom Neodenticula seminae were found in Continuous Plankton Recorder (CPR) samples in the Labrador Sea as the first record in the North Atlantic for more than 800 000 years. The event coincided with modifications in Arctic hydrography and circulation, increased flows of Pacific water into the Northwest Atlantic and in the previous year the exceptional occurrence of extensive ice‐free water to the North of Canada. These observations indicate that N. seminae was carried in a pulse of Pacific water in 1998/early 1999 via the Canadian Arctic Archipelago and/or Fram Strait. The species occurred previously in the North Atlantic during the Pleistocene from∼1.2 to∼0.8 Ma as recorded in deep sea sediment cores. The reappearance of N. seminae in the North Atlantic is an indicator of the scale and speed of changes that are taking place in the Arctic and North Atlantic oceans as a consequence of regional climate warming. Because of the unusual nature of the event it appears that a threshold has been passed, marking a change in the circulation between the North Pacific and North Atlantic Oceans via the Arctic. Trans‐Arctic migrations from the Pacific into the Atlantic are likely to occur increasingly over the next 100 years as Arctic ice continues to melt affecting Atlantic biodiversity and the biological pump with consequent feedbacks to the carbon cycle.     

French mosquito populations invaded by A2-B2 esterases causing insecticide resistance

In the mosquito Culex pipiens L., the two associated esterases A2 and B2 are responsible for resistance to organophosphorus (OP) insecticides in many countries of Africa, Asia and North America. We report here their presence and geographic spread in French populations based on the analysis of 168 samples collected from 1984 to 1990. First detected in 1986 in one sample from southern France, these esterases were progressively found in new geographic locations, so that in 1990 their distribution covered at least four contiguous French regions. RFLP analysis of the amplified B2 gene indicates that A2-B2 arrived in France most likely through migration. This genetic invasion is discussed in the light of the recent occurrence of A2-B2 in the mosquito genome, and of the consequences of this new resistance factor in natural populations already possessing other insecticide resistance genes.