Developmental Endocrinology of the Dipnoan, Neoceratodus forsteri

The development of the pineal, pituitary and thyroid glandsof the extant lungfish, Neoceratodus forsteri, are being studiedboth morphologically and functionally. This paper presents datafrom hatching to 40–52 weeks for a standardised seriesof lungfish, bred at Macquarie University. At hatching, thepineal comprises a single organ attached to the roof of thediencephalon, with well-developed photoreceptor, supportingand ganglion cells. The photoreceptors gradually degenerate,giving way to secretory cells which contain electron dense granules.These latter are immunoreactive to melatonin antibodies anddigestable with protease. The pituitary at hatching comprisesa hollow ball of cells lying beneath the infundibular regionof the hypothalamus. Ultrastructurally, four cell types canbe distinguished by cytoplasmic granule size after the firstfour weeks of development posthatching. By 20 weeks, a furtherthree cell types are recognisable. Inununogold labelling hasidentified corticotropes and melanotropes at four weeks and,at 20 weeks, prolactin cells, thyrotropes and somatotropes alsocan be identified. The thyroid is only just apparent at hatching,containing 2–3 follicles. Thenumbers of follicles increasesgradually, and variably between animals, with age. Iodine uptakein methimazole-treated animals did not exceed that of controlsat any of the three stages tested, indicating a lack of feedbackcontrol between thyroid hormones and pituitary thyrotropes at,or before, 40 weeks of age. Thyroid hormone receptors in theliver at 40 weeks are predominantly immunoreactive to humanTRac antibodies. These findings taken together suggest that,up to 40 weeks post hatching, lungfish development is equivalentto amphibian premetamorphic development. This would be consistentwith lungfish neoteny, but cannot be taken as evidence for neotenyuntil confirmed at later stages of development     

Location of bumblebee nests is predicted by counts of nest‐searching queens

1. Bumblebee nests are difficult to find in sufficient numbers for well replicated studies. Counts of nest‐searching queens in spring and early summer have been used as an indication of preferred nesting habitat, but this relationship has not yet been validated; high densities of nest‐searching queens may indicate habitat with few nesting opportunities (meaning that queens have to spend longer looking for them). 2. From mid April 2010, queen bumblebees were counted along 20 transects in grassland and woodland habitats in central Scotland, U.K. The number of inflorescences of suitable forage plants were also estimated at each transect visit. The area surrounding each transect was searched for nests in the summer. 3. In total, 173 queen bumblebees were recorded on transects, and, of these, 149 were engaged in nest‐searching. Searches subsequently revealed 33 bumblebee nests. 4. The number of nest‐searching queens on transects was significantly, positively related to the number of nests subsequently found. Estimated floral abundance along the transect did not correlate with numbers of nest‐searching queens or with the number of nests found, suggesting that queens do not target their searching to areas that are locally high in spring forage. 5. The data suggest that counts of nest‐searching queens provide a useful positive indication of good nesting habitat, and hence where bumblebee nests are likely to be found later in the year.     

Studies on the initiation of adventitious roots on mung bean hypocotyl

During the early stages of root induction in hypocotyls of mungbean cuttings, four new peroxidase isoenzymes are formed inthat part of the cutting that produces roots. These isoenzymesare in addition to and different from the three already presentin the hypocotyl. Forty-eight hr is required for the changeto take place from the original three to seven isoenzymes. Thechange in isoenzyme pattern and root initiation itself are retardedwhen streptomycin is applied during the very early stages ofroot induction. However, during the latter part of the first24-hr period after the cutting is made and when some of thenew isoenzymes have already been formed, the rooting processbecomes insensitive to this antibiotic. Cytologically, the occurrenceof cell division is paralleled by the formation of the fournew peroxidase isoenzymes. The delay in the occurrence of celldivision caused by the presence of streptomycin is paralleledby a similar delay in the formation of the four new isoenzymes. (Received November 27, 1970; )     

Impacts of birds of prey on gamebirds in the UK: a review

The influence of predators on the distribution, density and dynamics of their prey species has long been of interest to ecologists and wildlife managers. Where the prey population is also utilized by humans, conflicts may arise through competition for a limited resource. Because gamebird shooting in the UK provides employment, recreation and income, the impact of birds of prey on gamebird populations has been the subject of intense debate for many years. Various approaches have been used to assess the impacts that raptors have on gamebird populations. Here we review the applicability and limitations of the methods used and assess the scientific evidence for population-level and economic impacts of raptors on gamebird populations in the UK. Raptors may, in some situations, take large numbers of gamebirds and may be an important proximate cause of mortality, although few studies have addressed the impacts of raptors on either breeding or pre-shooting densities. Two exceptions are studies of Hen Harrier Circus cyaneus , Peregrine Falcon Falco peregrinus predation on Red Grouse Lagopus lagopus scoticus on moorland in Scotland and Sparrowhawk Accipiter nisus predation on Grey Partridge Perdix perdix on farmland in England. Both these studies suggested that raptors could have population-level impacts when their gamebird prey was already at low density. Studies on predation of captively bred gamebirds suggest that numbers taken by raptors at release pens vary considerably and in a few cases raptors have been documented killing relatively large numbers. On the whole, however, it appears that raptors account for a relatively small proportion of mortality among released birds and the impact on subsequent shooting bags is unknown. We summarize important gaps in current knowledge and recommend specific areas for future research.     

Functional significance of the dark central floret of Daucus carota (Apiaceae) L.; is it an insect mimic?

In Daucus carota L. (Apiaceae) the florets comprising the central umbellet of inflorescences are usually pink or dark purple, presenting a marked contrast to the surrounding umbellets, which are generally white. The number of dark florets varies, and some inflorescences have no dark florets. It has been proposed that the dark florets function as an insect mimic, and in so doing serve to attract insects to the flower. In contrast, other authors, Darwin included, suggest that they are functionally redundant. The present study examined whether the dark florets attract insects, and also whether this effect can be replicated by replacing these florets with an insect. At the study site in Portugal the predominant insect visitor was the beetle Anthrenus verbasci L. (Dermestidae), which is similar in size and shape to the dark florets. Large inflorescences and those with more dark florets attracted more beetles than small inflorescences and those with fewer or no dark florets. Inflorescences with the dark florets removed attracted fewer beetles visitors compared with intact inflorescences. Inflorescences in which the dark florets were replaced with one or a cluster of five dead, freeze-killed A. verbasci attracted more beetles than inflorescences from which the dark florets had been removed. Replacement of the dark florets with a relatively large Meloid beetle resulted in the attraction of markedly fewer A. verbasci . We conclude that the dark florets can act as an insect attractant for some insect groups by acting as an insect mimic, and that they are adaptive, in contrast to the speculations of Darwin.     

MHC heterozygosity and survival in red junglefowl

Genes of the major histocompatibility complex (MHC) form a vital part of the vertebrate immune system and play a major role in pathogen resistance. The extremely high levels of polymorphism observed at the MHC are hypothesised to be driven by pathogen‐mediated selection. Although the exact nature of selection remains unclear, three main hypotheses have been put forward; heterozygote advantage, negative frequency‐dependence and fluctuating selection. Here, we report the effects of MHC genotype on survival in a cohort of semi‐natural red junglefowl (Gallus gallus) that suffered severe mortality as a result of an outbreak of the disease coccidiosis. The cohort was followed from hatching until 250 days of age, approximately the age of sexual maturity in this species, during which time over 80% of the birds died. We show that on average birds with MHC heterozygote genotypes survived infection longer than homozygotes and that this effect was independent of genome‐wide heterozygosity, estimated across microsatellite loci. This MHC effect appeared to be caused by a single susceptible haplotype (CD_c) the effect of which was masked in all heterozygote genotypes by other dominant haplotypes. The CD_c homozygous genotype had lower survival than all other genotypes, but CD_c heterozygous genotypes had survival probabilities equal to the most resistant homozygote genotype. Importantly, no heterozygotes conferred greater resistance than the most resistant homozygote genotype, indicating that the observed survival advantage of MHC heterozygotes was the product of dominant, rather than overdominant processes. This pattern and effect of MHC diversity in our population could reflect the processes ongoing in similarly small, fragmented natural populations.     

Characterization of 29 polymorphic artiodactyl microsatellite markers for the mountain goat (Oreamnos americanus)

We report the results of a cross‐species amplification test of 156 bovine, ovine and cervid microsatellite markers in a wild population of mountain goats, Oreamnos americanus, inhabiting Caw Ridge, Alberta, Canada. Twenty‐nine markers were found to be low to moderately polymorphic with between two to nine alleles per locus. Observed heterozygosity ranged from 0.14 to 0.85 for a sample of 215 mountain goats. This set of markers will be used in parentage analyses to construct the pedigree of the long‐term studied population and to investigate the effects of individual genetic variability on life‐history traits.