Biology subjects

van der Burg, C. A.

Publications and source records attributed to van der Burg, C. A..

6 recordsLinked to original sources

bioRxiv2026

Gonadal remodelling in socially driven sex change is associated with novel and known sex genes, epigenetic reprogramming, and inflammation-mediated apoptosis.

Many fish undergo dramatic, socially cued female-to-male sex change, yet the events that initiate and then regulate gonadal reprogramming and reorganisation during this phenomenal metamorphosis are broadly unknown. The New Zealand spotted wrasse, Notolabrus celidotus, is a temperate fish species that displays the extraordinary ability to undergo protogynous sex change. Removal of a terminal-phase male from a social group triggers the most dominant female to change sex and become a male. To characterise the molecular changes associated with gonadal metamorphosis in spotty, we used genomic and transcriptomic approaches, generating a high-quality genome and a transcriptomic time-series that captures the sex change process from start to finish. These data, together with paired histological data, reveal distinct transcriptional profiles that characterise the process of sex change. As expected, the expression of masculinising genes steadily increases, while feminising genes steadily decrease, throughout the transition. We further identify novel candidate genes, including genes involved in immune signalling and tissue remodelling through inflammation-mediated apoptosis, whose expression strongly correlates with key events in sex change, while also confirming the roles of known sex determination and differentiation genes in this process. Collectively these data give us new insights into how a normally committed developmental process remains plastic and is reversed to completely alter organ structures, and also sheds light on the evolution of sex determination in other animals. This work furthers the development of the spotty as a new tractable model for sex change research.

genomics↗

bioRxiv2026

Loser effects orchestrate dominance hierarchies in socially-controlled sex change

Socially-controlled sex changing fishes provide powerful model systems for investigating sexual development and phenotypic plasticity in both behavior and physiology. The remarkable sexual transformation these fishes undertake is strongly influenced by their position in dominance hierarchies. However, the behavioral mechanisms underlying hierarchical formation remain understudied, particularly among female groups. Here, we investigated the role of winner-loser effects among females in establishing social dominance in a female-to-male sex changing fish. Individuals with prior losing experiences were more likely to lose subsequent size-matched fights, demonstrating clear loser effects, while there was no evidence for winner effects. Initial mirror aggression and some prior fighting behaviors, particularly submission, significantly and positively correlated with aggression in size-matched fights and subsequent mirror aggression; however, contest outcomes were not altered by these factors. Additionally, mirror aggression increased significantly only in subjects that drew size-matched fights. These findings demonstrate complex fighting dynamics in female-female competition and confirm the presence of loser effects in a sequential hermaphroditic species. These effects may represent evolutionarily advantageous mechanisms underlying sex change, thereby offering further context for examining how social rank advantages drive sexual transition.

animal behavior and cognition↗

bioRxiv2024

A comparative analysis of toxin gene families across diverse sea anemone species

All species from order Actiniaria (sea anemones) are venomous, even though most are of no threat to humans. Currently, we know very little about the toxin gene complement of highly venomous members of this order. To address this gap in knowledge, we sequenced the transcriptome of the highly venomous and medically significant Hells Fire sea anemone, Actinodendron plumosum, as well as five distantly related species, Cryptodendrum adhaesivum, Epiactis australiensis, Heteractis aurora, Isactinia olivacea and Stichodactyla mertensii. We used bioinformatic approaches to identify their toxin gene complements and performed a comparative evolutionary analysis of seven understudied toxin families. Of the 16 toxin families identified, 12-40 candidate toxins were found in the six new sea anemone transcriptomes, with only 12 candidates in eight toxin families identified in A. plumosum. Across 26 sea anemone species, six neurotoxin families showed evidence of taxonomic restriction, whereas the phospholipase A2 toxin family was ubiquitously distributed. Additionally, we identified two alternative forms for the phospholipase A2 toxin family, a 10- and 14-cysteine framework, which warrant further structural and functional characterisation. Overall, we have identified a comprehensive list of toxins from a wide diversity of sea anemone species that provides the basis for future research to structurally and functionally characterise novel candidates for use as therapeutics or for agricultural applications.

genetics↗

bioRxiv2024

Behavioral and neural correlates of social hierarchy formation in a sex-changing fish

Social hierarchies in sex-changing fish determine which fish will change sex, yet the complexities of hierarchy formation at the neurobehavioral level are still being unraveled. Here, we investigate the formation of social hierarchies within groups of New Zealand spotty wrasse, integrating behavioral observations with neural activation patterns upon social disruption. We find that dominance hierarchies form linearly based on size, with larger fish displaying more dominant behaviors and smaller fish displaying more submissive behaviors. Disruption of the social hierarchy induced rapid behavioral changes, particularly in second-ranked fish, highlighting that second-ranked fish will opportunistically adopt a dominant position. Analysis of neural activation patterns reveals that the social decision-making network is deeply involved in the establishment of dominance, with the fish attaining dominance showing significant differences to all other ranked fish. Overall, this study underscores the complexity of social relationships and their neural underpinnings in the spotty wrasse, providing a foundation for further research into the cellular and molecular mechanisms of socially-controlled sex change, and demonstrates that disruption of the social hierarchy triggers rapid changes in both behavior and the social decision-making regions of the brain.

animal behavior and cognition↗

bioRxiv2022

Genomic, Functional and Structural Analyses Reveal Mechanisms of Evolutionary Innovation within the Sea Anemone 8 Toxin Family

ShK from Stichodactyla helianthus has established the therapeutic potential of sea anemone venom peptides, but many lineage-specific toxin families in actinarians remain uncharacterised. One such peptide family, sea anemone 8 (SA8), is present in all five sea anemone superfamilies. We explored the genomic arrangement and evolution of the SA8 gene family in Actinia tenebrosa and Telmatactis stephensoni, characterised the expression patterns of SA8 sequences, and examined the structure and function of SA8 from the venom of T. stephensoni. We identified ten SA8 genes in two clusters and six SA8 genes in five clusters for T. stephensoni and A. tenebrosa, respectively. Nine SA8 T. stephensoni genes were found in a single cluster and an SA8 peptide encoded by an inverted SA8 gene from this cluster was recruited to venom. We show that SA8 genes in both species are expressed in a tissue-specific manner and the inverted SA8 gene has a unique tissue distribution. While functional activity of the SA8 putative toxin encoded by the inverted gene was inconclusive, its tissue localisation is similar to toxins used for predator deterrence. We demonstrate that, although mature SA8 putative toxins have similar cysteine spacing to ShK, SA8 peptides are distinct from ShK peptides based on structure and disulfide connectivity. Our results provide the first demonstration that SA8 is a unique gene family in actiniarians, evolving through a variety of structural changes including tandem and proximal gene duplication and an inversion event that together allowed SA8 to be recruited into the venom of T. stephensoni.

genetics↗

bioRxiv2019

The rapid regenerative response of a model sea anemone species Exaiptasia pallida is characterised by tissue plasticity and highly coordinated cell communication

Regeneration of a limb or tissue can be achieved through multiple different pathways and mechanisms. The sea anemone Exaiptasia pallida has been observed to have excellent regenerative proficiency but this has not yet been described transcriptionally. In this study we examined the genetic expression changes during a regenerative timecourse and report key genes involved in regeneration and wound healing. We found that the major response was an early upregulation of genes involved in cellular movement and cell communication, which likely contribute to a high level of tissue plasticity resulting in the rapid regeneration response observed in this species. We find the immune system is only transcriptionally active in the first eight hours post-amputation and conclude, in accordance with previous literature, that the immune system and regeneration have an inverse relationship. Fifty-nine genes (3.8% of total) differentially expressed during regeneration were identified as having no orthologues in other species, indicating that regeneration in E. pallida may rely on the activation of species-specific novel genes. Additionally, taxonomically-restricted novel genes, including species-specific novels, and highly conserved genes were identified throughout the regenerative timecourse, showing that both may work in concert to achieve complete regeneration. We conclude that E. pallida behaves similarly to other anemone species such as Nematostella vectensis and Calliactis polypus but with some notable novel differences.

evolutionary biology↗