Population continuity vs. discontinuity revisited: dental affinities among late Paleolithic through Christian-era Nubians

The present study revisits a subject that has been a source of long-standing bioarchaeological contention, namely, estimation of Nubian population origins and affinities. Using the Arizona State University dental anthropology system, frequencies of 36 crown, root, and intraoral osseous discrete traits in 12 late Pleistocene through early historic Nubian samples were recorded and analyzed. Specifically, intersample phenetic affinities, and an indication of which traits are most important in driving this variation, were determined through the application of correspondence analysis and the mean measure of divergence distance statistic. The results support previous work by the author and others indicating that population discontinuity, in the form of replacement or significant gene flow into an existing gene pool, occurred sometime after the Pleistocene. This analysis now suggests that the break occurred before the Final Neolithic. Samples from the latter through Christian periods exhibit relative homogeneity, which implies overall post-Pleistocene diachronic and regional population continuity. Yet there are several perceptible trends among these latter samples that: 1) are consistent with documented Nubian population history, 2) enable the testing of several existing peopling hypotheses, and 3) allow the formulation of new hypotheses, including a suggestion of two post-Pleistocene subgroups predicated on an age-based sample dichotomy.     

Endocrine events during pre-diapause and non-diapause larval-pupal development of the tobacco hornworm, Manduca sexta

The haemolymph ecdysteroid titre and in vitro capacities of prothoracic glands and corpora allata to synthesize ecdysone and juvenile hormone, respectively, during the last-larval instar of diapause-destined (short-day) and non-diapause-destined (long-day) Manduca sexta were investigated. In general, the ecdysteroid titres for both populations of larvae were the same and exhibited the two peaks characteristic of the haemolymph titre during this developmental stage in Manduca. The only difference in the titre occurred between day 7 plus 12 h and day 7 plus 20 h, when the short-day larval titre did not decrease as quickly as the long-day titre. The in vitro synthesis of ecdysone by prothoracic glands of short- and long-day larvae during the pharate pupal phase of the instar were also essentially the same. Activity fluctuated at times which would support the idea that ecdysone synthesis by the glands is a major contributing factor to the changes in the haemolymph ecdysteroid titre. There was one subtle difference in prothoracic gland activity between the two populations, occurring on day 7 plus 2 h. By day 7 plus 10 h, however, rates of ecdysone synthesis by the short- and long-day glands were comparable. This elevated activity of the short-day glands occurred just prior to the period the haemolymph ecdysteroid titre remained elevated in these larvae. The capacities of corpora allata to synthesize juvenile hormone I and III in vitro were not markedly different in long- and short-day last-instar larvae. At the time of prothoracicotropic hormone release in the early pupa, activity of corpora allata from short- and long-day reared animals was low and also essentially the same. There were a few differences in the levels of synthesis at isolated times, but they were not consistent for both homologues. Overall, there are no compelling differences in the fluctuations of ecdysteroids and juvenile hormones between diapause-destined and non-diapause-destined Manduca larvae. Since these hormones do not appear to play any obviously significant role in the induction of pupal diapause in this insect, the photoperiodic induction of diapause in Manduca appears to be a predominantly brain-centred phenomenon not involving endocrine effectors.     

Biology and prey range of Cryptognatha nodiceps (Coleoptera: Coccinellidae), a potential biological control agent for the coconut scale, Aspidiotus destructor (Hemiptera: Diaspididae)

Cryptognatha nodiceps Marshall is an important natural enemy used in biological control programmes against Aspidiotus destructor (Signoret), an introduced pest of coconut in many countries. In order to increase our understanding of C. nodiceps, the present study to quantify aspects of the developmental, reproductive and feeding biology under constant environmental conditions (26±2°C, 55-65% RH) was carried out. In addition, methods for culturing the scale and the beetle were developed. The average duration of development was 19.2±0.1 days for males and 19.6±0.2 days for females. Female longevity and lifetime fecundity was 35.6±5.1 days and 141.0±35.6 eggs, respectively. Life table statistics were as follows: reproductive rate, 9.99, intrinsic rate of increase, 0.09, finite rate of increase, 1.1, doubling time, 7.8 days and generation time, 41.1 days. Studies on feeding biology showed that C. nodiceps was oligophagous. The coccinellid fed and reproduced on prey species in two families, Diaspididae and Coccidae. Adults also fed on the coconut whitefly Aleurodicus cocois (Curtis) (Aleyrodidae) but no reproduction occurred on this prey. Aphididae, Psyllidae and Pseudococcidae were not fed upon.     

The behaviour of mosquitoes in relation to humans under holed bednets: the evidence from experimental huts

The physical integrity of bednets is a concern of national malaria control programs, as it is a key factor in determining the rate of replacement of bednets. It is largely assumed that increased numbers of holes will result in a loss of protection of sleepers from potentially infective bites. Experimental hut studies are valuable in understanding mosquito behaviour indoors, particularly as it relates to blood feeding and mortality. This review summarises findings from experimental hut studies, focusing on two issues: (i) the effect of different numbers or sizes of holes in bednets and (ii) feeding behaviour and mortality with holed nets as compared with unholed nets. As might be expected, increasing numbers and area of holes resulted in increased blood feeding by mosquitoes on sleepers. However, the presence of holes did not generally have a large effect on the mortality of mosquitoes. Successfully entering a holed mosquito net does not necessarily mean that mosquitoes spend less time in contact with the net, which could explain the lack in differences in mortality. Further behavioural studies are necessary to understand mosquito behaviour around nets and the importance of holed nets on malaria transmission.     

Who were the ancient Egyptians? Dental affinities among Neolithic through postdynastic peoples

Qualitative and quantitative methods are employed to describe and compare up to 36 dental morphological variants in 15 Neolithic through Roman-period Egyptian samples. Trait frequencies are determined, and phenetic affinities are calculated using the mean measure of divergence and Mahalanobis D2 statistics for discrete traits; the most important traits in generating this intersample variation are identified with correspondence analysis. Assuming that the samples are representative of the populations from which they derive, and that phenetic similarity provides an estimate of genetic relatedness, these affinities are suggestive of overall population continuity. That is, other than a few outliers exhibiting extreme frequencies of nine influential traits, the dental samples appear to be largely homogenous and can be characterized as having morphologically simple, mass-reduced teeth. These findings are contrasted with those resulting from previous skeletal and other studies, and are used to appraise the viability of five Egyptian peopling scenarios. Specifically, affinities among the 15 time-successive samples suggest that: 1) there may be a connection between Neolithic and subsequent predynastic Egyptians, 2) predynastic Badarian and Naqada peoples may be closely related, 3) the dynastic period is likely an indigenous continuation of the Naqada culture, 4) there is support for overall biological uniformity through the dynastic period, and 5) this uniformity may continue into postdynastic times.