Inducing metamorphosis in the irukandji jellyfish Carukia barnesi

Here we utilize chemical ecology as a tool to manipulate the biological system of a small, but highly venomous to humans, cubozoan jellyfish, Carukia barnesi. We trialled a range of chemical reagents including indole compounds, 9-cis-retinoic acid and lugols solution to induce metamorphosis between the polyp and medusa life stages. An optimum method was determined resulting in a 90% metamorphosis rate to healthy medusa by exposing the polyps to 1 μM of 5-methoxy-2-methylindole for 24 h. Of note is that chemical exposure time significantly impacts health and metamorphosis rates in this species. We also present a theoretical mechanism for the chemical/biological interactions occurring during metamorphosis. This is a significant methodological advancement which now enables rearing of this animal en mass in aquaria-a world first for this species-which will subsequently supply and facilitate venom research into this understudied jellyfish.

The influence of ecological factors on cnidarian venoms

Venom research is often focussed on medical relevance, novel compounds and venom evolution, whilst studying the relationship between a venom and its environment – venom ecology - has been conducted to a lesser extent. Given the projected environmental changes envisioned to occur with global warming, it is pertinent now more than ever, to highlight this topic. Here we review literature examining the influence of ecological factors such as environmental temperature, salinity, ontogeny, geographic location and diet on cnidarian venoms. This review provides an exclusive focus on the cnidarian phylum and encompasses all available published, peer-reviewed literature to our knowledge regarding the ecological factors influencing venom. We find a startling lack of research into the effects of both environmental and biological factors on venoms, with very few to no studies available per category. Importantly, research does exist that suggest these ecological processes may influence other marine or terrestrial venoms, thus we recommend future research is needed to explore this concept in cnidarians.

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Cnidarian toxins are significantly affected by environment and biology, yet literature on the subject is scarce.

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Temperature, ontogeny, geographic location and diet can influence cnidarian venoms.

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Salinity can influence other marine toxins, but literature is lacking for cnidarians.

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More venom ecology research is needed in medically important species, if medical treatments are to advance.

Targeted ribozymes reveal a conserved function of the Drosophila paired gene in sensory organ development

The Drosophila paired (prd) gene, the founding member of the PAX gene family, is required for normal embryonic segmentation and is re-expressed later in development in the head and developing CNS. As for most embryonically active genes, global defects resulting from loss of early prd function obscure an analysis of the role of later expression phases. We used inducible targeted ribozymes to functionally 'knock-out' prd at late stages. When prd protein levels in the head are reduced in this fashion, the maxillary chemosensory ventral organs fail to develop and dorsal-lateral cirri rows are disrupted. These studies reveal a role for prd in sensory organ development that appears to be conserved in PAX genes throughout the animal kingdom.

Distal-less is a downstream gene of Deformed required for ventral maxillary identity

The homeotic selector (HOM) proteins are required for the diversification of the anterior-posterior axis of the Drosophila body plan, assigning unique identities to regional domains of cells comprising one or a few parasegments or segments. The HOM proteins apparently accomplish this task by the transcriptional regulation of numerous downstream genes. At present few downstream genes are known, so models of how downstream genes mediate HOM functions are based more on intuition than information. Our results indicate that Distal-less is a downstream gene of the HOM gene Deformed, and Distal-less function is required for the elaboration of a subset of the maxillary epidermal identities specified by Deformed. The regulatory effect of Deformed on Distal-less is mediated by a ventral maxillary-specific enhancer located 3′ of the Distal-less transcription unit. We propose that Deformed and Distal-less, both of which encode homeodomain transcription factors that are persistently expressed in ventral maxillary cells, combinatorially specify a subsegmental code required for a group of cells to differentiate maxillary cirri.

Ethological isolation and mating experience in Drosophila paulistorum

With few exceptions, previously published experiments documenting ethological isolation between Drosophila populations have used young virgin females. We have observed directly females of Drosophila paulistorum semispecies in choice experiments with both homogamic and heterogamic males. Aged females' sexual selection did not differ from that of young females. Previous heterogamic copulatory experience did not change the degree of sexual isolation; however, females with homogamic copulatory experience showed a significantly higher preference for homogamic males.