The effect of photoperiod on the circadian rhythm of mating responsiveness in the fruit fly, Dacus tryoni

ABSTRACT. The daily fluctuation in mating responsiveness of Dacus tryoni was recorded through a range of light cycles. Evidence was obtained of strict control of the fluctuation by a circadian clock. The phase setting of the fluctuation in the different light cycles was in conformity with Aschoff's (1965) generalizations about circadian rhythms, and had no relationship to overt sexual behaviour occurring during the cycles. The amplitude of the fluctuation in mating responsiveness varied between cycles, suggesting possible variation in the amplitude of the oscillation of the circadian clock.     

Mind, memory and history: How classifications are shaped by and through time, and some consequences

Understanding the history of systematics bears on contemporary issues such as the distinction between classifications and systems, the belief that ‘natural’ classifications reflect the progressive refinement of our ideas of relationships, and the dubious reputation acquired by systematics. Here I emphasize the extent to which ‘mind’ shapes classifications. I show that groups in biological classifications often have six or fewer members, in line with the number of things that humans can conveniently memorize together. Concerns about memorization are evident in the work of systematists like Tournefort, Linnaeus, and Antoine-Laurent de Jussieu, and the whole hierarchy of George Bentham's and J. D. Hooker's great Genera plantarum is structured by such concerns. An analytical element in Jussieu's work was emphasized by Cuvier and others, and the hierarchy of their classifications reflects more directly aspects of nature as they understood it, although concerns about memorisation remain evident. Linking an understanding of what classifications can represent to the ideas the makers of classifications had about nature makes it clear that classifications are rarely rigid class hierarchies, but are often more like systems. Historically, the synthetic approach, discussed here, tends to lead to systems, the analytical approach, to ‘classifications’. We must remember that systematists’ work is evaluated by other scientists, and by society at large. The confusion evident in systematics simply confirmed the negative perceptions that many people in the nineteenth century had of naturalists, botanists and zoologists, perceptions that persist today. Zoologica Scripta itself, and the Journal of Natural History, which under this title is about the same age, reflect part of this history. I conclude by emphasizing (1) if systems or classifications in the nineteenth century reflect ‘nature’, it is a nature very different from that we understand today, and (2) the extent and the persistence of the opposition between the synthetic and anaytical approaches.     

Nutrient limitation and soil development: Experimental test of a biogeochemical theory

Walker & Syers (1976) proposed a conceptual model that describesthe pattern and regulation of soil nutrient pools and availability during long-term soil and ecosystem development. Their model implies that plantproduction generally should be limited by N on young soils and by P on oldsoils; N and P supply should more or less equilibrate onintermediate-aged soils. We tested the application of this model to nutrientlimitation, using a well characterized substrate age sequence in Hawaiianmontane rain forest. Earlier experiments had evaluated nutrient limitationin forests on a young (300 y) and an old (4,100,000 y) substrate on the samedevelopmental sequence; N alone limited tree growth on the youngsubstrate, while P alone did so on the old one. An additional fertilizerexperiment based on replicated treatments with N, P, and all othernutrients combined, applied in individually and in all factorialcombinations, was established in an intermediate-aged site in theLaupahoehoe Forest Reserve, Hawaii. Here, diameter increments of thedominant tree Metrosideros polymorpha increased slightly with Nadditions, and nearly doubled when N and P were added together.Additions of elements other than N and P had no significant effecton growth. These results show that N and P had equilibrated (relativeto plant requirements) in the intermediate aged site. Together withthe earlier experiments, these results suggest that the Walker and Syersmodel provides a useful starting point for explaining the nature anddistribution of nutrient limitation in forest ecosystems.     

DETERMINANTS OF PRIMATE SOCIAL ORGANIZATION: COMPARATIVE EVIDENCE AND NEW INSIGHTS FROM MALAGASY LEMURS

The aim of this review is to summarize newly available information on lemur social systems, to contrast it with the social organization of other primates and to relate it to existing models of primate social evolution. Because of their evolutionary history, the primates of Madagascar constitute a natural experiment in social evolution. During millions of years of isolation, they converged with other primates only in the most fundamental way in the evolution of solitary, pair-living and group-living species, but deviate in several respects within these basic categories of social organization. Solitary lemurs remain poorly studied, but their social organization appears to be broadly similar to that of other solitary primates, even though the unexpected lack of sexual dimorphism may indicate that similar types of social organization can give rise to different mating systems. The determinants of a solitary lifestyle remain elusive. Pair-living lemurs show striking convergences with other monogamous primates in several behavioural traits, but also deviate in that the majority of species are at least partly nocturnal and do not exhibit direct paternal care of dependent young. Group-living lemurs have not evolved single-male groups, male-bonded and multi-level societies, and polyandrous groups may also be lacking. Female philopatry is common, but female bonds are generally weakly developed and eviction of females from natal groups is not unusual. Group-living lemurs also differ from anthropoids in that their groups have even adult sex ratios, smaller average size and may split up on a seasonal basis. Feeding competition, predation risk and reproductive competition can not fully explain these unusual aspects of lemur social organization. It has therefore been suggested that the social consequences of the risk of infanticide and of recent changes in activity may be ultimately responsible for these idiosyncracies of group-living lemurs, an explanation largely supported by the available evidence. Thus, social factors and fundamental life-history traits, in addition to ecological factors, contribute importantly to variation in social systems among lemurs, and possibly other primates. However, neither the diversity of lemur social systems, nor the evolutionary forces and mechanisms operating in these and other primates are yet fully understood.     

Polyamine Synthesis and Interconversion by the Microsporidian Encephalitozoon cuniculi

Polyamines are small cationic molecules necessary for growth and differentiation in all cells. Although mammalian cells have been studied extensively, particularly as targets of polyamine antagonists, i.e. antitumor agents, polyamine metabolism has also been studied as a potential drug target in microorganisms. Since little is known concerning polyamine metabolism in the microsporidia, we investigated it in Encephalitozoon cuniculi, a microspordian associated with disseminated infections in humans. Organisms were grown in RK-13 cells and harvested using Percoll gradients. Electron microscopy indicated that the fractions banding at 1.051-1.059/g/ml in a microgradient procedure, and 1.102-1.119/g/ml in a scaled-up procedure were nearly homogenous, consisting of pre-emergent (immature) spores which showed large arrays of ribosomes near polar filament coils. Intact purified pre-emergent spores incubated with [1H] ornithine and methionine synthesized putrescine, spermidine, and spermine, while [14C]spermine was converted to spermidine and putrescine. Polyamine production from ornithine was inhibitable by DL-alpha-difluoromethylornithine (DFMO) but not by DL-alpha-difluoromethylarginine (DFMA). Cell-free extracts from mature spores released into the growth media had ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetdc), and spermidine/spermine N1-acetyltransferase (SSAT) activities. ODC activity was inhibited by DFMO, but not by DFMA. AdoMetdc was putrescine-stimulated and inhibited by methylglyoxal-bis(guanylhydrazone); arginine decarboxylase activity could not be detected. It is apparent from these studies that Encephalitozoon cuniculi pre-emergent spores have a eukaryotic-type polyamine biosynthetic pathway and can interconvert exogenous polyamines. Pre-emergent spores were metabolically active with respect to polyamine synthesis and interconversion, while intact mature spores harvested from culture supernatants had little metabolic activity.     

Evolution of jaw depression mechanics in aquatic vertebrates: insights from Ghondrichthyes

The widely accepted phylogenctic position of Chondrichthyes as the sister group to all other living gnathostomes makes biomechanical analyses of this group of special significance for estimates of skull function in early jawed vertebrates. We review key findings of recent experimental research on the feeding mechanisms of living elasmobranchs with respect to our understanding of jaw depression mechanisms in gnathostome vertebrates. We introduce the possibility that the ancestral jaw depression mechanism in gnathostomes was mediated by the coracomandibularis muscle and that for hyoid depression by the coracohyoideus muscle, as in modern Chondrichthyes and possibly placoderms. This mechanism of jaw depression appears to have been replaced by the sternohyoideus (homologous to the coracohyoideus) coupling in Osteichthycs following the split of this lineage from Chondrichthyes. Concurrent with the replacement of the branchiomandibularis (homologous to the coracomandibularis) coupling by the sternohyoideus coupling as the dominant mechanism of jaw depression in Osteichthyes was the fusion and shift in attachment of the intcrhyoideus and intermandibularis muscles (producing the protractor hyoideus muscle, mistakenly refereed to as the geniohyoideus), which resulted in a more diversified role of the sternohyoideus coupling in Osteichthyes. The coracohyoideus coupling appears to have been already present in vertebrates where it functioned in hyoid depression, as in modern Chondrichthyes, before it acquired the additional role of jaw depression in Osteichthyes.     

The genetics of colour-patterns in the grasshopper Chorthippus brunneus

Several alleles were found to determine the colour of the dorsal pronotum in Chorthippus brunneus; there was evidence for at least two loci ( C and V ). Brown ( C^B )was the universal recessive and green ( C^C ) was dominant to all other colours. The white allele ( C^W )was codominant with green( C^G )and purple ( C^P ). Wing-patterns were determined by a separate, probably linked locus ( W ). A dominant plain wing-pattern ( W^P ) was associated with colours other than brown. Striped( W^S )and mottled( W^mo ) were codominant and a plain recessive allele ( W^P ) was also found. All three alleles were associated with the brown phenotype. A purple-sided allele ( S^Pu ) was sometimes obmd with C^pu.. S ^Pu was dominant to brown sides ( S^B ), A series of markings on the dorsal and lateral pronotum ( linea intermedia, fascia postocularis, linea media, carina media and zona lateralis ) were investigated and found to be controlled at separate loci which may be linked to W . These characters were expressed by dominant alleles.
Epistatic effects by modifier loci were shown to have an important effect on the determination of wing phenotype. Allele Wo⁺ , for example, suppressed the stripe-wing pattern, linea media, carina media and zona lateralis .
It was concluded that colour patterns appear to be under genetic control and that dominant alleles were rare in the wild. Changes in shades of colours were shown to be age-dependent and minor.