title: Field and laboratory investigations of Echyridella menziesii (Unionida: Hyriidae) interactions with host fishes

authors: Hanrahan, Nicole Joy

subjects: freshwater mussel

abstract: Globally, the study of freshwater mussels has increased markedly in recent years, spurred on by recognition that many mussel populations are declining or are already extinct. The New Zealand freshwater mussel Echyridella menziesii (Unionida: Hyriidae) has a current threat classification of ‘At Risk, Declining’, in part reflecting disruption of recruitment on host fish. The life cycle of E. menziesii includes a parasitic stage in which the larvae (glochidia) must attach to a host fish to transform into the juvenile stage. However, no research has been conducted to understand whether fish develop immunity that limits infestation rates, and little is known about the spatial and temporal variations of mussel-host interactions in natural environments in New Zealand. This study therefore aimed to: i) determine whether multiple infestations of E. menziesii glochidia influenced the suitability of common bully (Gobiomorphus cotidianus) as a host; and ii) quantify fish host associations over the glochidial release period in three contrasting Waikato streams.

Common bully considered naïve to E. menziesii were infested with glochidia in the laboratory, and placed in individual, flow-through tanks (22oC) which were flushed every second day to measure glochidia detachment and juvenile excystment. Fishes were infested either one, two or three times, with ‘control’ fish infested for the first time in the second and third rounds. There were no differences in cumulative detachment rates of glochidia and no major reductions in metamorphosis success across multiple infestations. 

Metamorphosis success rate across all infestation rounds was ≤30%, and was highest when initial glochidia viability was also high. The lack of detectable immunity in common bully, at least after three sequential infestations, is promising for the future conservation of E. menziesii as host-fish are likely to be repetitively infested with glochidia over the mussel spawning season in a natural setting.

Infestation by glochidia was determined on the associated fish community, caught using a combination of electrofishing and minnow trapping. In parallel with these evaluations, mussel brood pouch development was assessed fortnightly from October 2018 to February 2019 at three Waikato stream sites. Peak glochidia release occurred in February when average monthly water temperatures were >18.8oC. A field method was developed to quantify glochidial attachment on external surfaces of fish, while internal attachment (gills, mouth) was quantified by laboratory dissection. While a range of fish hosts were identified, 86% of recorded glochidia were attached to Gobiomorphus species, including redfin bully (G. huttoni) and common/Crans bully (G. cotidianus/G. basalis). Most externally-attached glochidia (73%) occurred on caudal, pelvic and pectoral fins. Host associations appeared to favour benthic rather than pelagic species, and did not change throughout the mussel reproductive season despite seasonal change in fish communities.

This research demonstrates that common bully, and more broadly Gobiomorphus species, are important hosts for glochidia and do not develop immunity to repeated infestations. Gobiomorphus species have the potential to be very useful ‘tools’ to assist in restoring E. menziesii populations, and therefore conservation management must consider these host fish populations as well as other habitat and water quality factors affecting E. menziesii.

text: Field and laboratory investigations of Echyridella menziesii (Unionida: Hyriidae) interactions with host fishes Globally, the study of freshwater mussels has increased markedly in recent years, spurred on by recognition that many mussel populations are declining or are already extinct. The New Zealand freshwater mussel Echyridella menziesii (Unionida: Hyriidae) has a current threat classification of ‘At Risk, Declining’, in part reflecting disruption of recruitment on host fish. The life cycle of E. menziesii includes a parasitic stage in which the larvae (glochidia) must attach to a host fish to transform into the juvenile stage. However, no research has been conducted to understand whether fish develop immunity that limits infestation rates, and little is known about the spatial and temporal variations of mussel-host interactions in natural environments in New Zealand. This study therefore aimed to: i) determine whether multiple infestations of E. menziesii glochidia influenced the suitability of common bully (Gobiomorphus cotidianus) as a host; and ii) quantify fish host associations over the glochidial release period in three contrasting Waikato streams.

Common bully considered naïve to E. menziesii were infested with glochidia in the laboratory, and placed in individual, flow-through tanks (22oC) which were flushed every second day to measure glochidia detachment and juvenile excystment. Fishes were infested either one, two or three times, with ‘control’ fish infested for the first time in the second and third rounds. There were no differences in cumulative detachment rates of glochidia and no major reductions in metamorphosis success across multiple infestations. 

Metamorphosis success rate across all infestation rounds was ≤30%, and was highest when initial glochidia viability was also high. The lack of detectable immunity in common bully, at least after three sequential infestations, is promising for the future conservation of E. menziesii as host-fish are likely to be repetitively infested with glochidia over the mussel spawning season in a natural setting.

Infestation by glochidia was determined on the associated fish community, caught using a combination of electrofishing and minnow trapping. In parallel with these evaluations, mussel brood pouch development was assessed fortnightly from October 2018 to February 2019 at three Waikato stream sites. Peak glochidia release occurred in February when average monthly water temperatures were >18.8oC. A field method was developed to quantify glochidial attachment on external surfaces of fish, while internal attachment (gills, mouth) was quantified by laboratory dissection. While a range of fish hosts were identified, 86% of recorded glochidia were attached to Gobiomorphus species, including redfin bully (G. huttoni) and common/Crans bully (G. cotidianus/G. basalis). Most externally-attached glochidia (73%) occurred on caudal, pelvic and pectoral fins. Host associations appeared to favour benthic rather than pelagic species, and did not change throughout the mussel reproductive season despite seasonal change in fish communities.

This research demonstrates that common bully, and more broadly Gobiomorphus species, are important hosts for glochidia and do not develop immunity to repeated infestations. Gobiomorphus species have the potential to be very useful ‘tools’ to assist in restoring E. menziesii populations, and therefore conservation management must consider these host fish populations as well as other habitat and water quality factors affecting E. menziesii.

year: 2019

title: Taiwanese textbooks for young learners of English: A criterion-referenced analysis

authors: Wang, Wei Pei

subjects: Taiwan

abstract: This article focuses on one of the problems faced by one Pacific rim country, Taiwan, in coming to terms with the increasing globalization of English, that is, the production of textbooks that are appropriate for young learners. Increasing pressure to ensure that its citizens achieve a high level of proficiency in English has led Taiwan, in common with many other countries, to reduce the age at which children are introduced to English in schools. This has lead to the proliferation of English textbooks for young learners. The Taiwan national English curriculum guidelines recommend that teaching materials should cultivate communicative ability and should include varied activities, a range of different types of text, and interesting, practical and lively topics and themes. Three textbook series produced in Taiwan are analyzed and discussed here in terms of a range of effectiveness criteria. It is concluded that the textbook writers have not yet come to terms with the recommendations in the English curriculum guidelines. In that these recommendations are similar to recommendations included in national curriculum guidelines for the teaching of languages in many other parts of the world, it is suggested that language teaching materials produced elsewhere might usefully be analyzed in a similar way.

text: Taiwanese textbooks for young learners of English: A criterion-referenced analysis This article focuses on one of the problems faced by one Pacific rim country, Taiwan, in coming to terms with the increasing globalization of English, that is, the production of textbooks that are appropriate for young learners. Increasing pressure to ensure that its citizens achieve a high level of proficiency in English has led Taiwan, in common with many other countries, to reduce the age at which children are introduced to English in schools. This has lead to the proliferation of English textbooks for young learners. The Taiwan national English curriculum guidelines recommend that teaching materials should cultivate communicative ability and should include varied activities, a range of different types of text, and interesting, practical and lively topics and themes. Three textbook series produced in Taiwan are analyzed and discussed here in terms of a range of effectiveness criteria. It is concluded that the textbook writers have not yet come to terms with the recommendations in the English curriculum guidelines. In that these recommendations are similar to recommendations included in national curriculum guidelines for the teaching of languages in many other parts of the world, it is suggested that language teaching materials produced elsewhere might usefully be analyzed in a similar way.

year: 2007-02

title: Different coloured tears: Dual cultural identity and Tangihanga

authors: Edge, Kiri

subjects: bereavement

abstract: Although whānau/family that are configured by both Pākehā and Māori identities number significantly within New Zealand, there has been little or no attention paid to the ways in which these identities influence the bereavement processes that will inevitably impact upon the lives of these whānau/family. The present study explored the experiences of an individual, whose whānau/family included two life ways: Māori and Pākehā. Of specific focus was the ways in which these identities influenced his bereavement subsequent to the death of his beloved wife, who was of Māori descent. One elderly male Pākehā participant was interviewed, using an open ended narrative approach. The interview was semi-structured around five broad themes, but the focus was upon the participant’s experiences and his preference in expressing these. The data analysis utilised a thematic process which allowed the participant’s experiences to determine the emergent themes. The results depicted the diversity of issues that may be raised for dual cultural whānau/family within bereavement processes. Two central themes are discussed in relation to intercultural conflict and the eventual resolution that was created. Decision-making processes, cultural and language differences played significant roles within the conflict and exclusion experienced by the participant. Communication and compromise provided resolution to the prior conflicts experienced. This created positive and unexpected outcomes which resulted in increased understandings and the strengthening of links between the participant, his whānau/family and his wife’s marae.

text: Different coloured tears: Dual cultural identity and Tangihanga Although whānau/family that are configured by both Pākehā and Māori identities number significantly within New Zealand, there has been little or no attention paid to the ways in which these identities influence the bereavement processes that will inevitably impact upon the lives of these whānau/family. The present study explored the experiences of an individual, whose whānau/family included two life ways: Māori and Pākehā. Of specific focus was the ways in which these identities influenced his bereavement subsequent to the death of his beloved wife, who was of Māori descent. One elderly male Pākehā participant was interviewed, using an open ended narrative approach. The interview was semi-structured around five broad themes, but the focus was upon the participant’s experiences and his preference in expressing these. The data analysis utilised a thematic process which allowed the participant’s experiences to determine the emergent themes. The results depicted the diversity of issues that may be raised for dual cultural whānau/family within bereavement processes. Two central themes are discussed in relation to intercultural conflict and the eventual resolution that was created. Decision-making processes, cultural and language differences played significant roles within the conflict and exclusion experienced by the participant. Communication and compromise provided resolution to the prior conflicts experienced. This created positive and unexpected outcomes which resulted in increased understandings and the strengthening of links between the participant, his whānau/family and his wife’s marae.

year: 2011