title: No evidence for a culturable bacterial tetrodotoxin producer in Pleurobranchaea maculata (Gastropoda: Pleurobranchidae) and Stylochoplana sp. (Platyhelminthes: Polycladida)

authors: Salvitti, Lauren R.

subjects: bacteria

abstract: Tetrodotoxin (TTX) is a potent neurotoxin found in the tissues of many taxonomically diverse organisms. Its origin has been the topic of much debate, with suggestions including endogenous production, acquisition through diet, and symbiotic bacterial synthesis. Bacterial production of TTX has been reported in isolates from marine biota, but at lower than expected concentrations. In this study, 102 strains were isolated from Pleurobranchaea maculata (Opisthobranchia) and Stylochoplana sp. (Platyhelminthes). Tetrodotoxin production was tested utilizing a recently developed sensitive method to detect the C9 base of TTX via liquid chromatography—mass spectrometry. Bacterial strains were characterized by sequencing a region of the 16S ribosomal RNA gene. To account for the possibility that TTX is produced by a consortium of bacteria, a series of experiments using marine broth spiked with various P. maculata tissues were undertaken. Sixteen unique strains from P. maculata and one from Stylochoplana sp. were isolated, representing eight different genera; Pseudomonadales, Actinomycetales, Oceanospirillales, Thiotrichales, Rhodobacterales, Sphingomonadales, Bacillales, and Vibrionales. Molecular fingerprinting of bacterial communities from broth experiments showed little change over the first four days. No C9 base or TTX was detected in isolates or broth experiments (past day 0), suggesting a culturable microbial source of TTX in P. maculata and Stylochoplana sp. is unlikely.

text: No evidence for a culturable bacterial tetrodotoxin producer in Pleurobranchaea maculata (Gastropoda: Pleurobranchidae) and Stylochoplana sp. (Platyhelminthes: Polycladida) Tetrodotoxin (TTX) is a potent neurotoxin found in the tissues of many taxonomically diverse organisms. Its origin has been the topic of much debate, with suggestions including endogenous production, acquisition through diet, and symbiotic bacterial synthesis. Bacterial production of TTX has been reported in isolates from marine biota, but at lower than expected concentrations. In this study, 102 strains were isolated from Pleurobranchaea maculata (Opisthobranchia) and Stylochoplana sp. (Platyhelminthes). Tetrodotoxin production was tested utilizing a recently developed sensitive method to detect the C9 base of TTX via liquid chromatography—mass spectrometry. Bacterial strains were characterized by sequencing a region of the 16S ribosomal RNA gene. To account for the possibility that TTX is produced by a consortium of bacteria, a series of experiments using marine broth spiked with various P. maculata tissues were undertaken. Sixteen unique strains from P. maculata and one from Stylochoplana sp. were isolated, representing eight different genera; Pseudomonadales, Actinomycetales, Oceanospirillales, Thiotrichales, Rhodobacterales, Sphingomonadales, Bacillales, and Vibrionales. Molecular fingerprinting of bacterial communities from broth experiments showed little change over the first four days. No C9 base or TTX was detected in isolates or broth experiments (past day 0), suggesting a culturable microbial source of TTX in P. maculata and Stylochoplana sp. is unlikely.

year: 2015-01-28

title: Geomorphic development of White Island Volcano based on slope stability modelling

authors: Moon, Vicki G.

subjects: White Island

abstract: White Island shows many geomorphic features associated with stratovolcanoes that have undergone major sector collapse, most notably the flat-floored amphitheatre comprising the present crater. ArcGIS is used to develop a reconstructed pre-failure cone and 2D limiting-equilibrium stability analysis is undertaken of the reconstructed cone. Water table ranges from 0% (dry) to 100% (saturated) are assumed and earthquake accelerations of 0–0.5 g bracket the likely range of accelerations expected in a volcanic setting; geotechnical data from Moon et al. [Moon, V., Bradshaw, J., Smith, R. and de Lange, W., 2005. Geotechnical characterization of stratocone crater wall sequences, White Island Volcano, New Zealand. Engineering Geology, 81: 146–178] are used. The models suggest that flank failure is a feasible explanation for the present-day geomorphology, and indicate that there were at least two retrogressive failures. The best model sees a core of hydrothermally altered material overlying relatively unaltered andesite lavas and breccias, where accelerations of 0.17 g (saturated slope) to 0.45 g (dry slope) are required to initiate failure (F = 1.0). The failure modelled was relatively small (volume of 0.21 km3), and would have mostly involved hydrothermally altered materials with some fresh rock mass. Two toreva blocks are recognised occupying the seaward margin of the amphitheatre, with a lobe of debris offshore suggested as the debris avalanche deposits. Modification of both the outer slopes of the island and the inner crater walls has occurred since the failure event, especially on the southwestern margin of the crater. Modelling suggests that further failure of the inner walls is likely and poses a significant hazard to tourists visiting the island; further outer slope failures are unlikely.

text: Geomorphic development of White Island Volcano based on slope stability modelling White Island shows many geomorphic features associated with stratovolcanoes that have undergone major sector collapse, most notably the flat-floored amphitheatre comprising the present crater. ArcGIS is used to develop a reconstructed pre-failure cone and 2D limiting-equilibrium stability analysis is undertaken of the reconstructed cone. Water table ranges from 0% (dry) to 100% (saturated) are assumed and earthquake accelerations of 0–0.5 g bracket the likely range of accelerations expected in a volcanic setting; geotechnical data from Moon et al. [Moon, V., Bradshaw, J., Smith, R. and de Lange, W., 2005. Geotechnical characterization of stratocone crater wall sequences, White Island Volcano, New Zealand. Engineering Geology, 81: 146–178] are used. The models suggest that flank failure is a feasible explanation for the present-day geomorphology, and indicate that there were at least two retrogressive failures. The best model sees a core of hydrothermally altered material overlying relatively unaltered andesite lavas and breccias, where accelerations of 0.17 g (saturated slope) to 0.45 g (dry slope) are required to initiate failure (F = 1.0). The failure modelled was relatively small (volume of 0.21 km3), and would have mostly involved hydrothermally altered materials with some fresh rock mass. Two toreva blocks are recognised occupying the seaward margin of the amphitheatre, with a lobe of debris offshore suggested as the debris avalanche deposits. Modification of both the outer slopes of the island and the inner crater walls has occurred since the failure event, especially on the southwestern margin of the crater. Modelling suggests that further failure of the inner walls is likely and poses a significant hazard to tourists visiting the island; further outer slope failures are unlikely.

year: 2009

title: Iwi sex ratios in the New Zealand population census: Why are women so dominant?

authors: Kukutai, Tahu

abstract: Recent census-based studies of iwi (tribal) population growth have revealed a high degree of volatility that cannot be explained by demographic factors alone. Although focused on a small number of iwi, these studies have shown that changing patterns of identification are an important driver of iwi population growth, and that the propensity to identify with an iwi appears to be much stronger among Māori women than men. Thus, the vast majority of iwi in the census have far more females than males, and female domination has increased over time. This paper describes the key features of female-favoured iwi sex ratios in the census and explores possible explanations. Focusing on sex ratios for the ten largest iwi, we find that female domination is highest in the 25–44 age group, and that this pattern is consistent over time. Further analysis shows that Māori women aged 25–34 years are more likely than their male counterparts to know detailed aspects of their pepeha (tribal identity), to explore whakapapa (genealogy) and to speak te reo Māori. Our results underscore the importance of Māori women as cultural connectors within their whānau, as well as in a broader iwi context.

text: Iwi sex ratios in the New Zealand population census: Why are women so dominant? Recent census-based studies of iwi (tribal) population growth have revealed a high degree of volatility that cannot be explained by demographic factors alone. Although focused on a small number of iwi, these studies have shown that changing patterns of identification are an important driver of iwi population growth, and that the propensity to identify with an iwi appears to be much stronger among Māori women than men. Thus, the vast majority of iwi in the census have far more females than males, and female domination has increased over time. This paper describes the key features of female-favoured iwi sex ratios in the census and explores possible explanations. Focusing on sex ratios for the ten largest iwi, we find that female domination is highest in the 25–44 age group, and that this pattern is consistent over time. Further analysis shows that Māori women aged 25–34 years are more likely than their male counterparts to know detailed aspects of their pepeha (tribal identity), to explore whakapapa (genealogy) and to speak te reo Māori. Our results underscore the importance of Māori women as cultural connectors within their whānau, as well as in a broader iwi context.

year: 2017