title: Effects of cortisol on female-to-male sex change in a wrasse

authors: Goikoetxea, Alexander

abstract: Sex change occurs as a usual part of the life cycle for many teleost fish and the modifications involved (behavioural, gonadal, morphological) are well studied. However, the mechanism that transduces environmental cues into the molecular cascade that underlies this transformation remains unknown. Cortisol, the main stress hormone in fish, is hypothesised to be a key factor linking environmental stimuli with sex change by initiating gene expression changes that shift steroidogenesis from oestrogens to androgens but this notion remains to be rigorously tested. Therefore, this study aimed to experimentally test the role of cortisol as an initiator of sex change in a protogynous (female-to-male) hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). We also sought to identify potential key regulatory factors within the head kidney that may contribute to the initiation and progression of gonadal sex change. Cortisol pellets were implanted into female spotty wrasses under inhibitory conditions (presence of a male), and outside of the optimal season for natural sex change. Histological analysis of the gonads and sex hormone analyses found no evidence of sex change after 71 days of cortisol treatment. However, expression analyses of sex and stress-associated genes in gonad and head kidney suggested that cortisol administration did have a physiological effect. In the gonad, this included upregulation of amh, a potent masculinising factor, and nr3c1, a glucocorticoid receptor. In the head kidney, hsd11b2, which converts cortisol to inactive cortisone to maintain cortisol balance, was upregulated. Overall, our results suggest cortisol administration outside of the optimal sex change window is unable to initiate gonadal restructuring. However, our expression data imply key sex and stress genes are sensitive to cortisol. This includes genes expressed in both gonad and head kidney that have been previously implicated in early sex change in several sex-changing species.

text: Effects of cortisol on female-to-male sex change in a wrasse Sex change occurs as a usual part of the life cycle for many teleost fish and the modifications involved (behavioural, gonadal, morphological) are well studied. However, the mechanism that transduces environmental cues into the molecular cascade that underlies this transformation remains unknown. Cortisol, the main stress hormone in fish, is hypothesised to be a key factor linking environmental stimuli with sex change by initiating gene expression changes that shift steroidogenesis from oestrogens to androgens but this notion remains to be rigorously tested. Therefore, this study aimed to experimentally test the role of cortisol as an initiator of sex change in a protogynous (female-to-male) hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). We also sought to identify potential key regulatory factors within the head kidney that may contribute to the initiation and progression of gonadal sex change. Cortisol pellets were implanted into female spotty wrasses under inhibitory conditions (presence of a male), and outside of the optimal season for natural sex change. Histological analysis of the gonads and sex hormone analyses found no evidence of sex change after 71 days of cortisol treatment. However, expression analyses of sex and stress-associated genes in gonad and head kidney suggested that cortisol administration did have a physiological effect. In the gonad, this included upregulation of amh, a potent masculinising factor, and nr3c1, a glucocorticoid receptor. In the head kidney, hsd11b2, which converts cortisol to inactive cortisone to maintain cortisol balance, was upregulated. Overall, our results suggest cortisol administration outside of the optimal sex change window is unable to initiate gonadal restructuring. However, our expression data imply key sex and stress genes are sensitive to cortisol. This includes genes expressed in both gonad and head kidney that have been previously implicated in early sex change in several sex-changing species.

year: 2022

title: The parasite release hypothesis and the success of invasive fish in New Zealand

authors: Zhang, Keshi

subjects: parasite release hypothesis

abstract: Non-indigenous species are commonly released from their native enemies, including parasites, when they are introduced into new geographical areas. This has been referred to as the enemy release hypothesis and more strictly as the parasite release hypothesis. The loss of parasites is commonly inferred to explain the invasiveness of non-indigenous species. I examined parasite release in New Zealand non-indigenous freshwater fishes. A literature review was undertaken in order to collate lists of the known parasite fauna of 20 New Zealand non-indigenous freshwater fish species. Records were collated from their home range, New Zealand, and some other introduced ranges, to determine whether these species have a reduced parasite diversity in the New Zealand and other introduced ranges. Five non-indigenous freshwater fish, mosquitofish (Gambusia affinis), rudd (Scardinius erythrophthalmus), goldfish (Carassius auratus), koi carp (Cyprinus carpio) and catfish (Ameiurus nebulosus), and one native freshwater fish, common bullies (Gobiomorphus cotidianus), were sampled and examined for metazoan parasites. Mosquitofish and bullies, of similar size and habitat, were examined with greater intensity than the other species. Based on the literature review and fish examination, I found that the non-indigenous freshwater fish in New Zealand have seemingly lost their parasites. Being “lost overboard” is likely to have caused the loss of some parasites as most of the additional hosts required for non-indigenous parasites are no present in New Zealand. However, the loss of most of mosquitofish’s parasites is likely due to “missing the boat”, as introduction into New Zealand was a two-step process, from their native range in North America, via Hawaii, before release in New Zealand. Additionally, other hosts required for parasites of mosquitofish are not present in New Zealand. The native common bullies were found to harbour more parasites than the non-indigenous mosquitofish. Two parasites were found from common bullies, the cysts of the trematodes Eustrongylides ignotus and Telogaster opisthorchis, and no parasites were found on mosquitofish. A lack of spillback of Eustrongylides ignotus from bullies to mosquitofish, despite being parasititised by this species in its native range, may due to mosquitofish not being able to feed on intermediate the hosts present in New Zealand. The establishment and spread of non-indigenous fish in New Zealand waters is likely not the sole result of parasite release, but given their apparent reduction or lack of parasites, it may be a factor contributing to their success.

text: The parasite release hypothesis and the success of invasive fish in New Zealand Non-indigenous species are commonly released from their native enemies, including parasites, when they are introduced into new geographical areas. This has been referred to as the enemy release hypothesis and more strictly as the parasite release hypothesis. The loss of parasites is commonly inferred to explain the invasiveness of non-indigenous species. I examined parasite release in New Zealand non-indigenous freshwater fishes. A literature review was undertaken in order to collate lists of the known parasite fauna of 20 New Zealand non-indigenous freshwater fish species. Records were collated from their home range, New Zealand, and some other introduced ranges, to determine whether these species have a reduced parasite diversity in the New Zealand and other introduced ranges. Five non-indigenous freshwater fish, mosquitofish (Gambusia affinis), rudd (Scardinius erythrophthalmus), goldfish (Carassius auratus), koi carp (Cyprinus carpio) and catfish (Ameiurus nebulosus), and one native freshwater fish, common bullies (Gobiomorphus cotidianus), were sampled and examined for metazoan parasites. Mosquitofish and bullies, of similar size and habitat, were examined with greater intensity than the other species. Based on the literature review and fish examination, I found that the non-indigenous freshwater fish in New Zealand have seemingly lost their parasites. Being “lost overboard” is likely to have caused the loss of some parasites as most of the additional hosts required for non-indigenous parasites are no present in New Zealand. However, the loss of most of mosquitofish’s parasites is likely due to “missing the boat”, as introduction into New Zealand was a two-step process, from their native range in North America, via Hawaii, before release in New Zealand. Additionally, other hosts required for parasites of mosquitofish are not present in New Zealand. The native common bullies were found to harbour more parasites than the non-indigenous mosquitofish. Two parasites were found from common bullies, the cysts of the trematodes Eustrongylides ignotus and Telogaster opisthorchis, and no parasites were found on mosquitofish. A lack of spillback of Eustrongylides ignotus from bullies to mosquitofish, despite being parasititised by this species in its native range, may due to mosquitofish not being able to feed on intermediate the hosts present in New Zealand. The establishment and spread of non-indigenous fish in New Zealand waters is likely not the sole result of parasite release, but given their apparent reduction or lack of parasites, it may be a factor contributing to their success.

year: 2012

title: Decolonising Midwifery Education in Aotearoa: A Case Study Approach

authors: Cleaver,  Deanne Lesley

subjects: Decolonisation

abstract: The bicultural nature of Aotearoa (New Zealand) creates a strong foundation for the unique environment that supports the weaving of indigenous knowledge throughout midwifery education, and in turn creating a platform for decolonisation. Te Tiriti o Waitangi/ The Treaty of Waitangi serves to inform the direction that midwifery education and midwifery practice must take by underpinning these frameworks.
The revised midwifery curriculum and reaccreditation that supported the immersion of Indigenous knowledge throughout the midwifery degree at Wintec is currently in its fifth year. It was identified that there needed to be a more explicit focus of cultural safety and responsiveness, therefore in support of this Mātauranga Māori (Māori knowledge) was carefully embedded and linked to learning outcomes. This is in direct support of Te Tiriti o Waitangi and a move towards a Te Tiriti honouring programme. Topics that relate to tikanga Māori (customs), Te Ao Māori (Māori worldview) and Te Reo Māori (language) are respectfully taught, providing opportunities for understanding and growing competencies for midwifery tauira.  
Understanding colonisation in its global context alongside its role in the history of Aotearoa supported by Te Tiriti o Waitangi knowledge, is vital in the process of decolonisation. Tauira are encouraged to explore and reflect on these factors throughout their degree, supporting their growing cultural safety and awareness of relationships.  An anti-racism workshop in the final year of the degree adds another layer to the work of decolonisation and equips tauira with tools to be active in their allyship.
This personal and curricula journey empowers tauira to become culturally safe and responsive midwives, positively impacting the health of whānau Māori.
Through a case study approach the effectiveness of the interweaving of indigenous knowledge, Te Tiriti o Waitangi and Anti-Racism praxis will be explored, with the purpose of unpacking the learnings as a tool for social transformation within the process of decolonisation.
These changes promote the professional development of educators and the empowerment of tauira to uphold Indigenous rights, while providing care in partnership that is respectful. Decolonising Midwifery Education in Aotearoa: A Case Study approach’ will be explored and unpacked.

text: Decolonising Midwifery Education in Aotearoa: A Case Study Approach The bicultural nature of Aotearoa (New Zealand) creates a strong foundation for the unique environment that supports the weaving of indigenous knowledge throughout midwifery education, and in turn creating a platform for decolonisation. Te Tiriti o Waitangi/ The Treaty of Waitangi serves to inform the direction that midwifery education and midwifery practice must take by underpinning these frameworks.
The revised midwifery curriculum and reaccreditation that supported the immersion of Indigenous knowledge throughout the midwifery degree at Wintec is currently in its fifth year. It was identified that there needed to be a more explicit focus of cultural safety and responsiveness, therefore in support of this Mātauranga Māori (Māori knowledge) was carefully embedded and linked to learning outcomes. This is in direct support of Te Tiriti o Waitangi and a move towards a Te Tiriti honouring programme. Topics that relate to tikanga Māori (customs), Te Ao Māori (Māori worldview) and Te Reo Māori (language) are respectfully taught, providing opportunities for understanding and growing competencies for midwifery tauira.  
Understanding colonisation in its global context alongside its role in the history of Aotearoa supported by Te Tiriti o Waitangi knowledge, is vital in the process of decolonisation. Tauira are encouraged to explore and reflect on these factors throughout their degree, supporting their growing cultural safety and awareness of relationships.  An anti-racism workshop in the final year of the degree adds another layer to the work of decolonisation and equips tauira with tools to be active in their allyship.
This personal and curricula journey empowers tauira to become culturally safe and responsive midwives, positively impacting the health of whānau Māori.
Through a case study approach the effectiveness of the interweaving of indigenous knowledge, Te Tiriti o Waitangi and Anti-Racism praxis will be explored, with the purpose of unpacking the learnings as a tool for social transformation within the process of decolonisation.
These changes promote the professional development of educators and the empowerment of tauira to uphold Indigenous rights, while providing care in partnership that is respectful. Decolonising Midwifery Education in Aotearoa: A Case Study approach’ will be explored and unpacked.

year: 2023