Social inhibition of maturation in females of the temperate wrasse Pseudolabrus celidotus and a comparison with the blennioid Tripterygion varium

In two temperate reef fish, Pseudolabrus celidotus (Bloch and Schneider) and Tripterygion varium (Bloch and Schneider) studied near Leigh, New Zealand, most spawning activity was concentrated during the first 2 months of spawning seasons which lasted about 5 months. In P. celidotus, maturation and spawning of first-year females (0+) was delayed with respect to older (1+yr) females. Within the 0+ age class, the minimum size of maturation declined as the spawning season proceeded. However, in all females of T. varium, ripening and spawning took place over the same time ranges. Observations on the seasonal patterns of female aggression suggested that larger female P. celidotus were socially inhibiting the maturation of small females. The level of interaction was high compared to that in T. varium, and reached a peak over the onset of the spawning season. This hypothesis was tested by the removal of larger (1+yr) female P. celidotus from a field population. The remaining 0+ females increased in ovary weight and matured earlier than those in an undisturbed area. We argue from this experiment that it is of advantage for P. celidotus females to spawn early in the season and of advantage to inhibit other females from doing so. Two possible reasons are suggested, the first applying to sexchanging species such as P. celidotus, the second to temperate-water fishes in general.     

Linear regression with Type I interval- and left-censored response data

Laboratory analyses in a variety of contexts may result in left- and interval-censored measurements. We develop and evaluate a maximum likelihood approach to linear regression analysis in this setting and compare this approach to commonly used simple substitution methods. We explore via simulation the impact on bias and power of censoring fraction and sample size in a range of settings. The maximum likelihood approach represents only a moderate increase in power, but we show that the bias in substitution estimates may be substantial.     

Bryophyte responses to microclimatic edge effects across riparian buffers.

Although riparian buffers are an important aspect of forest management in the boreal forest of Canada, little is known about the habitat conditions within buffers, due in part to complex edge effects in response to both the upland clearcut and the stream. We investigated microclimatic conditions and bryophyte growth and vitality in seven locations between the stream edge and 60 m into the upland undisturbed conifer forests and at the clearcut sites with riparian buffer 30 km northwest of Thunder Bay, Ontario, Canada. We hypothesized that the growth and vitality of a pleurocarpous moss, Hylocomium splendens, and an acrocarpous moss, Polytrichum commune, would be directly related to the microclimatic gradients detected. We further hypothesized that sensitivity of the bryophytes to environmental factors will vary depending on their life form type, i.e., pleurocarpous moss will respond differently than the acrocarpous moss. Both bryophyte species were transplanted in pots and placed at 10-m intervals along 60-m transects perpendicular to the stream across the buffer and undisturbed sites. Bryophyte growth, cover, and vitality, as well as microclimatic parameters and plant cover, were measured over the summer in 2003. The riparian buffers were simultaneously affected by microclimatic gradients extending from both the clearcut edge and the riparian-upland ecotonal edge. Both bryophyte species responded to changes in the microclimatic conditions. However, vapor pressure deficit (VPD) was the most important factor influencing the growth of H. splendens, whereas for P. commune growth soil moisture was most important. Our study confirms earlier findings that interior forest bryophytes such as H. splendens can be used as indicators to monitor edge effects and biodiversity recovery following forest harvesting. We demonstrate that growth and vitality of these bryophytes reflect the prevailing near-ground microclimatic conditions at the forest edges. Abundance estimates of such bryophytes can be used to determine the depth of edge effects across both ecotonal edges (e.g., riparian-upland forest edge) and anthropogenically created edges (e.g., clearcut edge). Forest management practices must consider depth of edge in determining the appropriate width of riparian buffers that would be necessary to sustain biodiversity and associated values at the land/water interface.     

Reproductive isolation and reproductive output in two sympatric mussel species (Mytilus edulis, M. trossulus) and their hybrids from Newfoundland

The mussels Mytilus edulis L. and M. trossulus Gould are found sympatrically in most areas of Newfoundland, with a low frequency of hybrids. To assess the potential for reproductive isolation, we sampled mussels from three sites in an eastern Newfoundland Bay from May–October 1996 to determine if there were differences in the reproductive cycles of the two species and their natural hybrids. In mussels with sheil lengths of 38–42 mm, males and females with mature gametes were dominant in June for M. edulis and hybrids, while M. trossulus showed a lower frequency of individuals with mature gametes. M. trossulus and hybrids spawned over a prolonged period (from late spring to early autumn) compared with most M. edulis individuals that spawned over a period of 2–3 weeks in July. This asynchrony in spawning activity between the two species may partially explain the low frequency of hybrids found in previous studies of these mussel populations. Female and male hybrids between M. edulis and M. trossulus showed normal gonad development, ripening and spawning, providing an opportunity for the introgression of genes between the two species. M. trossulus had a higher reproductive output than M. edulis of similar shell length, while hybrids showed intermediate values of reproductive output. M. trossulus females produced smaller eggs than either M. edulis or hybrids. Differences in reproductive traits may partially explain the maintenance of the mussel hybrid zone in Newfoundland. Published online: 13 August 2002     

Prenatal diagnosis of congenital cystic adenomatoid lung malformation: A report of seven cases

Six cases of macrocystic and one case of microcystic congenital adenomatoid lung malformation were diagnosed by ultrasound between 20 and 31 weeks of gestation. Combined polyhydramnios and fetal hydrops was present in three cases, polyhydramnios alone in one case, and isolated fetal hydrops also in one case. In the remaining two cases, both polyhydramnios and fetal hydrops were absent. Fetal outcome was poor, i.e., two terminations of pregnancy, three early neonatal deaths, and two survivors.     

Early prenatal diagnosis of congenital hypophosphatasia: Case report

Congenital hypophosphatasia is an autosomal recessive disorder, which usually has a fatal outcome during the neonatal period. This report presents the prenatal diagnosis of hypophosphatasia at 16 weeks of gestation. The characteristic ultrasonic findings in this abnormality demonstrate the superiority of ultrasound as compared with radiography.     

Sulphur isotopic investigation of a polluted raised bog and the uptake of pollutant sulphur by Sphagnum

The sulphur content and sulphur isotopic composition of Sphagnum as well as anionic compositions and sulphur isotope ratios of rainwater inputs and bog waters have been measured at Thorne Moors, a raised bog in eastern England. Rainwater sulphate isotopic composition shows the sulphur input at this site to be dominated by anthropogenic pollution from fossil fuel burning. Strong depletion of sulphate (low SO4(2-)/Cl-) and enrichment in 34S in sulphate occurs at depth in the bog porewaters due to bacterial sulphate reduction. Some surface waters have low SO4(2-)/Cl-) and are 34S enriched due to removal of sulphate by downward diffusion into a sulphate-reducing zone. Other sites have high SO4(2-)/Cl-) which appears to result from oxidation of organically bound sulphur in the peat. Sulphur is present in Sphagnum at around 0.2% by weight and is depleted by 0 to -9 per thousand in the heavier 34S isotope compared to sulphate. Comparison with similar data from pristine coastal sites shows that sulphur incorporation into Sphagnum is enhanced in the polluted site (as Sphagnum sulphur concentrations are higher at lower total sulphur inputs) and that sulphur incorporation is accompanied by a smaller isotopic shift than in the pristine sites. The data support a model of preferential incorporation of partially reduced sulphur species (probably HSO3-) into Sphagnum. In pristine sites these are only available as oxidation products of sulphide formed by sulphate reduction and are 32S depleted. In polluted sites this source is augmented by sulphur(IV) species in atmospheric inputs and the resultant mixture is less depleted in 32S. Thus, in the polluted sites more HSO3- is available for uptake and the isotopic shift between Sphagnum and aqueous sulphur species is smaller.     

The fate and removal of triclosan during wastewater treatment.

This work examines the variation in removal efficiency of triclosan in wastewater treatment works in the United Kingdom between November 2003 and April 2004. Concentrations of triclosan were measured at set points within three different types of wastewater treatment works: rotating biological contactors, trickling filters, and activated sludge. Overall removal of triclosan through these plants ranged from 58 to 96% (rotating biological contactors), 86 to 97% (trickling filter), and 95 to 98% (activated sludge).