Aluminum neurotoxicity in mammals

Although aluminum comprises a large percentage of the Earth's crust, it is excluded from body tissues, and especially from the central nervous system. When aluminum is experimentally introduced to the central nervous system, several neurotoxic effects are observed:i.e. neurofibrillary changes, behavioral and cognitive deficits and enzymatic and neurotransmitter changes, as well as certain types of epileptic seizures.The localization of relatively high levels of aluminum in Alzheimer disease, Guamanian amyotrophic lateral sclerosis and Parkinsonism-dementia has led to the implication of aluminum as a pathogenic factor in these diseases. Recent studies have shown that microtubule-associated proteins are part of the paired helical filaments which make up the intraneuronal neurofibrillary tangle. Other studies have identified the protein making the vascular and neuritic (senile) plaque amyloid and located the gene responsible for this protein to chromosome 21.Our electron microprobe analysis studies have not found the levels of aluminum or silicon in either the neurofibrillary tangles or amyloid cores reported elsewhere, nor have the levels of aluminum been elevated in approximately one half of the tangles and plaque cores examined to date.     

Metabolic studies on thiobiotic free-living nematodes and their symbiotic microorganisms

The marine, free-living Stilbonematinae (Nematoda: Desmodoridae) are remarkable for the ectosymbiotic, prokaryotic microorganisms that populate their entire body surface. These nematodes occur in sulfidic sediments in the microoxic zone just above the sulfide maximum. Several facts point to a chemolithotrophic, sulfide oxidizing nature of the microorganisms. The oxygen uptake of three species was measured with and without their microbial coat using Cartesian and Gradient Diver microrespirometry in February 1989 at Carrie Bow Cay (Belize Barrier Reef). Symbiont-free stilbonematids exhibited constant and uniform oxygen uptake rates over several hours; rates which are significantly lower than those of oxyphilic nematodes. Freshly extracted stilbonematids, with intact bacterial coats, consumed significantly more oxygen than symbiont-free worms in the first 3 h of measurement. While the rates of aposymbiotic worms were more or less constant over time, the rates of symbiont-carrying worms exhibited a conspicuous drop during prolonged respiration. InStilbonema sp., symbiont carrying individuals kept under oxygenated conditions for more than 12 h had a respiration rate similar to those of aposymbiotic specimens. When such worms were re-incubated in sulfide-enriched seawater the respiration rate was significantly elevated. The possibility of recharging the oxygenated symbiosis system via sulfide-uptake is seen as an indication that storage of reduced sulfur compounds, or reserve substances synthetized in the presence of sulfide, play a decisive role in the metabolisms of the symbiotic bacteria. Migration of nematodes between sulfidic and oxidized sediment-layers are, most likely, the key to understanding the success of this nematode-bacteria symbiosis.Please address all correspondence and requests for reprints to Professor J. Ott     

Biomasses,catch rates and abundances of demersal fishes,particularly predators of prawns,in a tropical bay in the Gulf of Carpentaria,Australia

The demersal fish fauna of Albatross Bay, in the eastern Gulf of Carpentaria, northern Australia, was sampled on seven cruises from August 1986 to November 1988, using a random stratified trawl survey. Four depth zones between 7 and 45 m were sampled during both day and night. The mean biomass of fish from all seven cruises was 297 kg ha^–1 for days trawls and 128 kg ha^–1 for night trawls. The overall mean catch rates were 922 kg h^–1 for day trawls and 412 kg h^–1 for night trawls. There were marked differences between cruises in both the biomass and catch rate. Approx 890 000 fish of 237 species were collected. Of these, 25 species comprised 82% of the total biomass and 74% of the overall catch rate. The dominant families were Leiognathidae, Haemulidae and Clupeidae, with Sciaenidae and Dasyatidae important at night.Leiognathus bindus was the most abundant species. Twenty-five species occurred in more than 50% of trawls, withCaranx bucculentus the most frequently caught (96% of all trawls). Thirty four species were predators on prawns; their absolute mean biomass was 50 kg ha^–1 during the day and 39 kg ha^–1 at night. The corresponding catch rates were 171 and 125 kg h^–1. Multiple-regression analyses were used to discriminate the effects of diel, seasonal, depth and cruise patterns. Of the 31 most abundant species, 15 showed diel patterns of abundance; 11 species showed seasonal patterns of abundance; 23 species had differential depth distribution; and 13 species showed significant cruise-to-cruise variation in abundance. Cruise variations in abundance were tested against salinity, temperature, tidal exchange, plankton biomass and prawn abundances as well as periods (and lags) of total rainfall prior to sampling. Only total rainfall showed any significant correlation. Total rainfall over a period of 6 wk immediately prior to sampling showed significant positive correlations with the abundances of five species, with overall daytime catch rates, and with the suite of 34 prawn predators. Rainfall and river runoff into Albatross Bay were significantly correlated. In Albatross Bay, the complex of factors affecting fish abundances and the magnitude of between-cruise differences indicate that such tropical communities may be unpredictable and are not seasonally constant. The high catch rates in Albatross Bay relative to similar tropical areas elsewhere are discussed and attributed to the light exploitation of the Albatross Bay stocks. Other than a prawn fishery, there is no commercial trawling in Albatross Bay. Hence, the only fishing mortality is a result of by-catch from prawn trawling. The annual total of such fish by-catch is probably less than 10% of the estimated standing stock of 93 000 tonnes.     

Systemic retention of ingested cantharidin by frogs

Summary Frogs(Rana pipiens) fed on blister beetles (Meloidae) or cantharidin, retain cantharidin systemically. After cessation of feeding, they void the compound relatively quickly. Systemic cantharidin does not protect frogs against ectoparasitic feeding by leeches(Hirudo medicinalis) or predation by snakes(Nerodia sipedon). As suggested by our data, and from reports in the early literature, ingestion of cantharidin-containing frogs can pose a health threat to humans.Paper no. 95 of the seriesDefense Mechanisms of Arthropods; no. 94 is LaMunyon & Eisner, Psyche (in press)     

On the integration of individual foraging strategies with colony ergonomics in social insects: nectar-collection in honeybees

Summary We experimentally tested whether foraging strategies of nectar-collecting workers of the honeybee (Apis mellifera) vary with colony state. In particular, we tested the prediction that bees from small, fast growing colonies should adopt higher workloads than those from large, mature colonies. Queenright small colonies were set up by assembling 10 000 worker bees with approximately 4100 brood cells. Queenright large colonies contained 35 000 bees and some 14 500 brood cells. Thus, treatments differed in colony size but not in worker/brood ratios. Differences in workload were tested in the context of single foraging cycles. Individuals could forage on a patch of artificial flowers offering given quantities and qualities of nectar rewards. Workers of small colonies took significantly less nectar in an average foraging excursion (small: 40.1 ± 1.1 SE flowers; large: 44.8 ± 1.1), but spent significantly more time handling a flower (small: 7.3 ± 0.4 s ; large: 5.8 ± 0.4 s). When the energy budgets for an average foraging trip were calculated, individuals from all colonies showed a behavior close to maximization of net energetic efficiency (i.e., the ratio of net energetic gains to energetic costs). However, bees from small colonies, while incurring only marginally smaller costs, gained less net energy per foraging trip than those from large colonies, primarily as a result of prolonged handling times. The differences between treatments were largest during the initial phases of the experimental period when also colony development was maximally different. Our results are at variance with simple models that assume natural selection to have shaped behavior in a single foraging trip only so as to maximize colony growth. Offprint requests to: P. Schmid-Hempel     

Movements of blue sharks (Prionace glauca) in depth and course

Acoustic telemetry was used to follow 22 blue sharks,Prionace glauca (Linnaeus), over the continental shelf and slope in the region between George's Bank and Cape Hatteras between 1979 and 1986. The sharks frequently made vertical excursions between the surface and depths of several hundred meters. The oscillations, which were repeated every few hours, were largest in the daytime and were smaller in amplitude and confined to depths near the thermocline at night. This behavior was prominent in trials from August through March, but was not seen from June through July. Diving is discussed in terms of a hunting tactic and behavioral thermoregulation. Most of the sharks moved in a southeasterly direction from the release point and many maintained a constant course day and night for several days. The sharks may orient to the earth's magnetic field, or to the ocean's electric fields, allowing them to swim on a constant heading in the absence of celestial cues. These possibilities are discussed in the appendix.     

Female-enhanced male competition determines the first mate and principal sire in the spider Linyphia litigiosa (Linyphiidae)

Summary Two to five days before sexual maturation, female sierra dome spiders (Linyphia litigiosa: Linyphiidae) undergo a transformation in their behavior toward males that visit their webs. During this latter part of their penultimate instar, females change from consistently positioning themselves far away from males to actively maintaining close proximity, reactions I call avoidant and associative behavior, respectively. Consistent associative behavior ceases after the female's first mating and thus is limited to soon-to-mature penultimate females. When a mate-seeking male fords an associative female, he attempts to guard her until she matures; this is often a multi-day affair. In contrast, males guard immature avoidant and mature mated females for only a single day. This dichotomy in male guarding times can be understood by the fact that associative behavior signals that the female will soon develop peak reproductive value. Upon completion of their final molt, 98% of females immediately mate with the current guarding male. Secondary suitors are not as likely to achieve mating. Moreover, first mates father 1.8 times more offspring, on average, than secondary mates. Whenever they meet on any female's web, males fight until one of the contestants withdraws. Fights typically are intensive, occasionally deadly, and often result in usurpation of the web by the newly arriving male. Larger males win more fights, but other qualities (e.g., vigor and persistence) appear to be important when contestants differ by less than 10–20% in body weight. Prolonged (i.e., multi-day) guarding of associative females enhances the intrasexual selection process by ensuring that every male that arrives at the web finds it already guarded. Therefore every male that finds the web becomes a participant in a series of male-male conflicts and web usurpations which span the period between the resident female's commencement of associative behavior and her sexual maturation. Since unforced male departures from the webs of associative females are rare, victors are retained on the web until they themselves lose a fight. This facilitates a steady increase in the fighting ability of sequential guards throughout the associative period, up until female maturation and mating. On my study site, first mates represented the final winners in a combative sorting process based on a minimum average of 2 fights; they were heavier and larger than secondary mates and randomly sampled males. The combination of (1) associative behavior by nearly mature females, (2) high mating propensity of newly mature females, and (3) first male sperm priority, constitutes a system whereby females enhance male-male competition and boost the expected fighting prowess of the principal sire of their progeny. Since males appear to make no material contribution toward progeny, the female's behavior probably functions to improve the genetic constitution of the offspring. In addition, the timing of associative behavior may limit prolonged guarding by food-stealing males to a period (1) encompassing the female's pre-molt fast and (2) before the heavy yolking of eggs, thereby ameliorating the nutritional costs of intrasexual selection.     

Accumulation and loss of biomass inLiocarcinus holsatus larvae during growth and exuviation

Liocarcinus holsatus (Fabricius) larvae, of females originating from the Elbe Estuary, FRG, were reared in the laboratory at constant 15°C in May 1988. For each larval stage, developmental time was measured by individual cultures (Zoea I: 6.7±0.7d; Zoea II: 5.0±0.6d; Zoea III: 4.8±0.7 d; Zoea IV: 5.3±0.6d; Zoea V: 6.1±1.1d; Megalopa: 10.45±0.7d). During the entire period of development, dry weight (W), carbon (C), nitrogen (N), and hydrogen (H) were measured daily (Zoea I to V) or every second day (Megalopa). The energy content (E) was estimated from C. Biomass and energy (per individual) increased in each larval stage as a parabolic function of age and is described by power functions. C, H, and E exhibit a higher percentage gain (relative to initial values at the time of hatching) than W and N. It is suggested that proportionally more lipid than protein is accumulated during larval development. Cyclical changes in the relative biomass (% W) correspond to the larval moult cycle, indicating a rapid uptake of water and minerals immediately after hatching and a later increase in tissue growth. Changes in the C:N ratio suggest that during the first period more lipid than protein is accumulated. These patterns of growth and elemental composition are compared with literature data and a high degree of similarity in the growth characteristics of decapod larvae is seen. In addition W, C, N, and H values as well as E were measured for the exuviae of Zoea I to V and Megalopa. The percentage loss of growth rate by exuviae for each larval instar were higher in W (12 to 16%) and C (8 to 12%), and varied between 5 and 10% for N, H, and E.     

Measuring ecological stress: Variations on a theme by R.M. Warwick

Two new indices are presented which reflect quantitatively the changes to be expected in an ecological community under stress, as previously described by R. M. Warwick. The indices summarize information which he presented graphically, and permit analyses of trends and inferential tests. We suggest that these indices should be tested with a wide variety of ecological time-series data in order to evaluate the feasibility of inferring ecological stress from static data.     

What is the sex ratio of harpacticoid copepods in the deep sea?

The sex ratios of deep-sea harpacticoids have been thought to be greatly skewed toward females. The representation of males is notably more equitable (approximately 1:2) at three deep-sea sites (San Diego Trough: 32°52.4N, 117°45.5W, 1 050 m, January 1987; Porcupine Seabight: 51°36.85N, 12°57.30W, 1 369 m, August 1984; northwest Atlantic, 40°27N, 62°20W, 4 820 m, July 1982, June 1983). This ratio conceals extensive variation at the species level. For some species, males are unknown. For other species, males are more numerous than females. Sampling bias against males can occur and may explain the more extreme reports of male rareness in the literature.