Abstract
The ability to make transgenic Hydra lines has allowed for quantitative in vivo studies of Hydra regeneration and physiology. These studies commonly include excision, grafting and transplantation experiments along with high-resolution imaging of live animals, which can be challenging due to the animal’s response to touch and light stimuli. While various anesthetics have been used in Hydra studies, they tend to be toxic over the course of a few hours or their long-term effects on animal health are unknown. Here, we show that the monoterpenoid alcohol linalool is a useful anesthetic for Hydra. Linalool is easy to use, non-toxic, fast acting, and reversible. It has no detectable long-term effects on cell viability or cell proliferation. We demonstrate that the same animal can be immobilized in linalool multiple times at intervals of several hours for repeated imaging over 2–3 days. This uniquely allows for in vivo imaging of dynamic processes such as head regeneration. We directly compare linalool to currently used anesthetics and show its superior performance. Linalool will be a useful tool for tissue manipulation and imaging in Hydra research in both research and teaching contexts.
Highlights
Abraham Trembley’s careful and systematic studies on Hydra regeneration, published in his Memoires in 1744, brought this freshwater cnidarian into the spotlight of biological research [1]
This anatomical simplicity, continuous cell turnover in the adult [3], and the ability to regenerate from small fragments of the body column or even from aggregates of cells [4,5] render Hydra a powerful system for studies of development [6], stem cell biology [7,8], and regeneration [9,10,11,12]
Intact polyps in Hydra Medium (HM) continuously exhibit body shape changes such as contractions, extensions, bending, as well as tentacle movements [19,52], which complicates in vivo manipulations and imaging
Summary
Abraham Trembley’s careful and systematic studies on Hydra regeneration, published in his Memoires in 1744, brought this freshwater cnidarian into the spotlight of biological research [1]. Hydra is an optically transparent polyp a few millimeters in length It consists of a hollow cylindrical body column with a head on one end, consisting of a ring of tentacles and a domeshaped hypostome, and an adhesive basal disk on the other end. Hydra is composed of only a small number of cell types originating from three (ectodermal, endodermal and interstitial) stem cell lineages [2] This anatomical simplicity, continuous cell turnover in the adult [3], and the ability to regenerate from small fragments of the body column or even from aggregates of cells [4,5] render Hydra a powerful system for studies of development [6], stem cell biology [7,8], and regeneration [9,10,11,12]. Hydra has a relatively simple nervous system [13,14], consisting of a few thousand cells [15] that are organized in three neuronal networks
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