Viviparity and intragonadal cannibalism in the diminutive sea stars Patiriella vivipara and P. parvivipara (family Asterinidae)

The Australian asterinid sea stars Patiriella vivipara and P. parvivipara have the most derived lifehistory pattern seen in the Asteroidea. They are simultaneous hermaphrodites, have intragonadal fertilisation, and incubate their young in the gonads to an advanced juvenile stage. As characteristic of brooding echinoderms, P. vivipara and P. parvivipara are diminutive, with P. parvivipara being the smallest known sea star. These species have the most restricted distribution known in the Asteroidea. Reproduction of two populations P. vivipara in Tasmania, Midway Point and Tesselated Pavement, was examined in specimens collected in 1991, 1992 and 1995. Reproduction of P. parvivipara in South Australia was examined in specimens collected from one population in 1991 and 1994. The gonads are ovotestes. Both species typically contain 6 to 8 predominantly female gonads and 1 predominantly male gonad. In the predominantly female gonads, only a few eggs and a small amount of sperm are produced at a time. Detection of sperm in these gonads requires histological examination. The amount of sperm in the predominantly female gonads appears sufficient to fertilise all the ova produced. The low allocation to male function and the simultaneous presence of mature eggs and sperm suggests that both species may be self-fertile. The amount of sperm in the predominantly male gonads however, would not be expected in exclusively self-fertilisers, suggesting that some outcrossing occurs. The significantly higher reproductive output of P. vivipara at Midway Point than at the Tesselated Pavement indicates that the Midway Point population is particularly important for the conservation of this species. P. vivipara and P. parvivipara have small, 140 to 150 m-diam eggs. Embryogenesis is asynchronous, with progeny at different stages of development in the gonads. The end-point of brooding is variable in P. vivipara, with juveniles emerging from the parent at sizes ranging between 1.5 and 5.0 mm diam. Juvenile P. parvivipara are born at a diameter of up to 2.5 mm. At birth the juveniles of both species are up to 25–30% of the parent's diameter. Birth involves distension of the gonopore, with a marked separation of the ossicles and softening of the connective tissue around the pore. The juveniles are considerably larger than the ova and depend on extraembryonic nutrition to support their growth. Once the mouth opens, the juveniles prey on their intragonadal siblings. Cannibalism accounts for the substantial post-metamorphic growth. Viviparity lies at the extreme end of the broadcasting-brooding continuum of life histories in Patiriella, and the life-history traits of P. vivipara and P. par-vivipara are compared with those of other Patiriella spp. to assess the changes associated with evolution of viviparity.     

A fetus with a chromosome 13 ring and placenta with chromosome 13 rod/ring mosaicism

A fetus was identified by prenatal cytogenetic diagnosis as having a karyotype 46,XY,r(13) (p11q13). Termination of the pregnancy yielded a severely malformed fetus. Fetal abnormalities included anencephaly, imperforate anus and urethral meatus, severe talipes, syndactyly, cardiac defects and other anomalies. Confirmatory studies on cultured placental villi cells indicated a second cell line, 46,XY, −13,+ 13qter→cen::13ql3→qter. This cell line was not detectable in cells derived from the fetus despite extensive studies. It seems likely that the two cell lines arose simultaneously with selection favouring the 46,XY,r(13) line. How the chromosome rearrangements may have arisen is discussed. We are unaware of other cases where a cell line identifiable by a chromosome abnormality appeared to be confined to placental tissue. However, studies on placental tissue may be helpful in understanding the origin of other unbalanced de novo rearrangements.     

Impacts of near future sea surface pH and temperature conditions on fertilisation and embryonic development in Centrostephanus rodgersii from northern New Zealand and northern New South Wales, Australia

Oceans are warming and becoming more acidic. While higher temperature and lower pH can have negative effects on fertilisation and development of marine invertebrates, warming may partially ameliorate the negative effect of lower pH. This study determined the effect of warming (3 °C) and decreased pH (0.3, 0.5, 1.1 units below ambient) on fertilisation and development in two populations of the sea urchin Centrostephanus rodgersii, one at its northern range limit (Coffs Harbour, New South Wales NSW, 30°27′S, 153°14′E) and the other one in New Zealand where the species may be a recent arrival (Mokohinau Islands, 35°56′S, 175°9′E). Both populations were sampled in August 2011. The two populations exhibited a differential response to temperature, while pH affected them similarly. Fertilisation was robust to pH levels forecast for 2100, and it was only slightly reduced at pH values forecast for 2300 (i.e. ≈5 and ≈8 % for the northern NSW and the New Zealand populations, respectively). Decreased pH (pH = 7.6) reduced the percentage of succeeding developmental stages. Progression through cleavage and hatching stages was faster at +3 °C in the New Zealand population but not in northern NSW urchins, while for the NSW population, there was a positive interaction between temperature and pH at hatching. Gastrulation was negatively affected by an extreme pH 7.0 treatment (60–80 % reduction) and least affected by increased temperature. The percentage of abnormal embryos at gastrulation increased significantly at +3 °C treatment in the northern NSW population. Predicted future increases in temperature may facilitate further expansion of the geographical range of C. rodgersii in New Zealand, with a minimal effect of concurrent reduced pH.     

Seasonal variation in the effects of ocean warming and acidification on a native bryozoan, Celleporaria nodulosa

Ocean warming and acidification are co-occurring stressors likely to affect marine biota through climate-driven change to the ocean. We investigated the effects of increased temperature and lowered pH, solely and in combination, on the growth of the endemic Australian bryozoan, Celleporaria nodulosa. Two temperatures and three pH levels were fully crossed in experimental treatments performed in winter 2008 (August) and summer 2009 (February/March). Fragments of C. nodulosa colonies (clones) were collected from Coffs Harbour, NSW, Australia, (30°18′S, 153°09′E) and elongation of colonies was assessed periodically over a 12-day incubation period. Lowered pH in winter significantly decreased growth. Elevated temperatures during the summer significantly impeded the growth of bryozoan colonies, possibly masking the effect of ocean acidification and discovering a maximal thermal tolerance at around 27 °C for C. nodulosa. The effects of decreased pH and increased temperature may be seasonally dependent and particularly acute during the summer months. Thermal stress may in fact be the initial stressor before ocean acidification, negatively affecting organisms in such a way that they are unable to survive before feeling the effects of ocean acidification.     

Deposition of contaminant aerosol on human skin

Over recent years, it has been established that deposition of various types of pollutant aerosols (e.g., radioactive) on human skin can have serious deleterious effects on health. However, only few investigations in the past have been devoted to measurement of deposition velocities on skin of particles of the potentially problematic sizes. An experimental programme has shown the deposition velocities on skin of particles in the ca. 0.5-5 microm AMAD range to be high and generally associated with great variations. A series of investigations have been made to identify some of the factors that lead to this variation. Part of the variation was found to be caused by differences between individuals, whereas another part was found to be related to environmental factors. The identification of major influences on skin contaminant deposition is important in estimating health effects as well as in identifying means for their reduction.     

Measurement of contaminant removal from skin using a portable fluorescence scanning system

The residence time of particulate contamination on the human body is a factor that has an important impact on the accuracy of exposure assessment in the aftermath of an accidental release of radionuclides to the atmosphere. Measurements of particle clearance from human skin were made using an illumination system to excite fluorescence in labelled silica particles and a CCD camera and image processing system to detect this fluorescence. The illumination system consists of high-intensity light emitting diodes (LEDS) of suitable wavelengths arranged on a portable stand. The physically small size of the LEDs allows them to be positioned close to the fluorescing surface, thus maximising the fluorescent signal that can be obtained. The limit of detection was found to be 50 microg of tracer particle per cm2. Experiments were carried out to determine the clearance rates of 10 microm and 3 microm particles from the skin. Results show that, in the absence of any mechanical rubbing of the skin, the clearance of particles from the skin followed an approximately exponential decay with a half-time of 1.5-7.8 h. Skin hairiness and degree of human movement were found, in addition to particle size, to have an important influence on particle fall-off rate.     

Reproductive cycle of Centrostephanus rodgersii (Echinoidea), with recommendations for the establishment of a sea urchin fishery in New South Wales

The reproductive cycle of the sea urchin Centrostephanus rodgersii (Agassiz) was investigated in two populations, at Clovelly and Little Bay, in Sydney, New South Wales, Australia. C. rodgersii were collected at monthly intervals from February 1992 through January 1993. The reproductive cycle was determined by histological examination of oogenesis and spermatogenesis, monthly measurements of gonad index (GI), and induction of spawning by KCl injection. C. rodgersii has an annual reproductive cycle that was highly synchronous in both populations. From February to June, gametogenesis was accompanied by a decline in the amount of nutritive tissue in the gonads. The urchins were mature from June to September, with peak spawning between July and August, as indicated by a significant drop in GI. The breeding season of C. rodgersii therefore coincides with the lowest sea temperatures and the shortest days of the year. The gonads returned to the recovering condition within a month of spawning, with a substantial thickening of the nutritive layer along the gonad wall, and the GI returned to near pre-spawning levels. As a result, the spent phase was rarely found in C. rodgersii. With the exception of a significant decrease in the GI following spawning of urchins from the Clovelly population, the GI measurements did not show any distinct pattern through time. Specimens spawned in response to KCl injection from mid-May to early October, with the maximum response in July. Although all individuals sampled were at a similar stage of maturity at any one time, inter-site differences were seen with all of the methods used. Gonad indices from Little Bay were consistently higher and less variable than those from Clovelly for most of the year. The Little Bay population could also be induced to spawn for a longer period of time than could the Clovelly population. The breeding season of the Little Bay population appears to be longer than that of the Clovelly population. The relationship between size and sexual maturity was also examined. All C. rodgersii with a test diameter of >60 mm could be induced to spawn and produced viable gametes. C. rodgersii has been nominated for commercial exploitation in New South Wales, and the results of this investigation are used to make recommendations on the timing and size limits for a fishery utilising this species.     

Stormflow hydrochemistry of a river draining an abandoned metal mine: the Afon Twymyn, central Wales

Contaminated drainage from metal mines is a serious water-quality problem facing nations that exploit metal mineral resources. Measurements of river hydrochemistry during baseflow are common at mine sites, whilst detailed hydrochemical information regarding stormflow is limited and often confined to a single event. This study investigates the seasonal evolution of stormflow hydrochemistry at an abandoned metal mine in central Wales, UK, and the possible sources and mechanisms of metal release. Significant flushing of metals was observed during stormflow events, resulting in concentrations that severely exceeded water-quality guidelines. The relationship between metal concentrations and river discharge suggests dissolution of efflorescent metal sulphates on the surface of the mine spoil as the principal source of the contamination. High fluxes of Pb during stormflows are linked to extended periods of dry weather prior to storm events that produced water table drawdown and encouraged oxidation of Pb sulphide in the mine spoil. However, some Pb flushing also occurred following wet antecedent conditions. It is suggested that Fe oxide reduction in mine spoil and translatory flows involving metal-rich pore waters results in flushing during wetter periods. Detailed measurements of stormflow hydrochemistry at mine sites are essential for accurate forecasting of long-term trends in metals flux to understand metal sources and mechanisms of release, to assess potential risks to water quality and instream ecology, and to gauge the potential effectiveness of remediation. In order to protect riverine and riparian ecosystems, it is suggested that routine monitoring of stormflows becomes part of catchment management in mining-impacted regions.