Why study planaria

While one study found that extended exposure to simulated microgravity is generally detrimental to planarian health Adell et al. Notably, while Adell et al. It is also worth noting that lethality in the simulated microgravity experiments only occurred under specific rotation conditions i. Furthermore, the planarian species differed in each of the three studies, complicating direct comparisons of the results, especially since species-specific sensitivities to spatial confinement have been reported Carter et al.

Adell et al. While neither study on board the ISS found planarians incapable of regeneration, differences in the findings nevertheless exist. Gorgiladze reported no regeneration defects monitoring 60 planarians. In contrast, Morokuma et al. Similarly, we have never observed such a phenotype in our toxicology screens Hagstrom et al. Furthermore, Morokuma et al showed long-term behavioral and microbiotic changes that were attributed to space travel Morokuma et al.

Taken together, the discrepancies in the existing studies call for further experiments to determine the effects of microgravity on planarian regeneration and physiology.

However, these experiments are expensive and difficult to realize. The SSEP, thus, provides a unique opportunity to address these kinds of intriguing questions by facilitating and engaging aspiring young scientists in the scientific process.

In this paper, we report our experiences conducting a planarian regeneration experiment within SSEP. Because of the lack of published SSEP experiments, we could not build upon prior work to optimize our experimental protocol. Because our experiment was similarly unsuccessful, our goal is to explain why it failed and how it could be improved to allow for future successful studies within the experimental constraints imposed by the SSEP program.

Asexual planarians of the species D. Planarians were maintained in bulk in Instant Ocean IO -water, fed organic chicken or beef liver once a week and cleaned twice a week, as previously described Hagstrom et al. Animals were starved for at least 5 days before being used for an experiment. Animals used for experiments were 6. To induce regeneration, intact animals were amputated between the auricles and pharynx with an ethanol-sterilized razor blade as in Hagstrom et al.

The heads were returned to the animal stocks and the tails were allowed to heal for 1 h before loading into the tubes. The silicone tube is mm long with an outer diameter of 13 mm and an inner diameter of 9. The Type 2 FME tube can be subdivided into two or three separate compartments through the use of clamps. The total volume of sample the Type 2 FME can hold is 9. Three were reserved for the selected flight 1 tube and ground 2 tubes truth experiments.

This test was performed using 5 ml plastic culture tubes Falcon, Corning, NY , since FME tubes were not available prior to proposal approval. Ten D. A second set of 10 D. After 2 weeks, both samples were compared using a Leica S6 trinocular stereo microscope Wetzlar, Germany equipped with a Basler Af camera Basler, Germany. Figure 1. Pre-flight experiments on planarian viability and regeneration.

A Representative image of a regenerated planarian, from an original tail piece, stored in a sealed 5 ml culture tube for 2 weeks at RT. C Representative image of a planarian which failed to regenerate during this time as no blastema has formed. D Representative image of a successfully regenerated planarian. While some planarians were fixed extended E , others curled up F.

Scale bars: 0. During the experimental design phase, one FME tube was prepared with 5 tails and one FME tube was prepared with 10 tails to determine how many worm pieces could survive in a single FME tube. A critical difference from the actual flight experiment was that formaldehyde was not placed in the second volume of the FME tube, since only the effect of lack of oxygen on worm viability was tested.

After 2 more weeks at ambient temperature, the tube containing 5 worms was emptied and the worms evaluated Figures 1C—E. In this tube, 4 worms were found alive with 3 out of the 4 regenerating normal.

The 4th worm had a closed wound but no blastema Figure 1C. The worms in the second FME tube were fixed by adding 1 ml formaldehyde.

All 10 worms were still present. Six of them had regenerated 2 eyes and 4 had no eyes. Thus, while lack of oxygen appeared to affect their ability to regenerate properly, planarians were able to survive 5 weeks in the FME tube without formaldehyde in the second chamber.

On July 24, , 30 D. The animals were allowed to close the wound for 1 h. CG-water was used instead of IO-water because it was commercially available. This allowed the experiment to be kept in a dormant state until arrival on the ISS.

The two ground truth experiments in the laboratory were transferred to ambient temperature in the dark on the same day. After 3 weeks in microgravity, an ISS crew member performed the Ud interaction on September 4, by opening the clamp that separated the planarians and formaldehyde, and shaking vigorously for 5 s to release the formaldehyde, thus terminating and preserving the experiment in microgravity.

The two ground truth experiments in the laboratory were treated using similar actions on the same day. On the day of harvesting, the liquid was poured into Petri dishes for analysis. All planarians in both ground truth and flight experiments had disintegrated. To assay which factors may have contributed to worm death during the experiment, additional post-flight experiments were performed. New FME tubes were set up as described in Table 1.

Specifically, we assayed the effects of the presence of formaldehyde, presence of air, and tube type. Of note, due to the high cost of FME tubes, when possible and appropriate, certain conditions were tested repeatedly in the same FME tube, with extensive washing before loading new worms.

When repeating conditions which contained formaldehyde, the original formaldehyde compartment was left intact. For the tube type experiments, we used 5 ml culture tubes VWR International, Radnor, PA containing 6 tails and 5 ml of CG spring water and 9 ml glass borosilicate tubes Corning, Corning, NY containing 10 tails and 9 ml spring water to keep the worm:volume ratio relatively constant.

Planarian viability was checked by eye every 3—4 days. The goal of this study was to analyze the effect of microgravity on planarian head regeneration.

Ideally, planarians would be amputated on board the ISS and then their regeneration documented. This, however, was not possible within the constraints of the SSEP, which only allowed a single interaction of the astronauts with the experiment.

While it was expected that regeneration would be delayed at colder temperatures Brondsted and Brondsted, , it was uncertain whether we could sufficiently delay it for such a long time. Furthermore, the regenerating planarians needed to be able to survive without oxygen for 2. First, we evaluated how long the regenerating worms were able to survive without oxygen.

While some studies have shown limited survival in enclosed conditions, with worms disintegrating within 5 days at a density of 0. InterPro enables protein sequence analysis, predicting domain and categorising into families and predicting domains. TreeFam is a gene family database and gene ontology GO is a database to predict ontology. Despite studies on the immune responses and injury induced repair, the immune system in Planarians remains poorly understood.

Studies encompassing strategies of comparative genomic analysis and data mining has made it possible to decipher that Planarian immune system houses homologs of the innate immune system common to all Bilateria which are activated as a result of injury thereafter leading to its repair [ 18 ]. Receptor mining and gene curration approaches has enabled the identification of the G protein-coupled receptors GPCRs , comprising families of Rhodopsin, Glutamate, Adhesion, Secretin and Frizzled which play role in eukaryotic signal transduction, in Planarian Schmidtea mediterranea.

The mining strategy and formal schemes of analytical processes is discussed in detail [ 12 ]. Such strategies has also made possible the identification of novel receptors, including a large and highly-diverged Platyhelminthes specific Rhodopsin subfamily PROF1 , a Planarian-specific Adhesion-like family PARF1 , and a typical Glutamate-like receptor [ 12 ].

With the help of ImagePlane high-throughput image analysis and information extraction tool based on novel self-parameterizing adaptive thresholding algorithm and automated pipeline, written in Python, identification of morphology of Planaria through observation of wild phenotype and those with morphological alterations mediated by RNAi induced methods has been possible. We refer the reader to the multiresolution algorithm capable of segmenting the image into anterior-posterior and or left-right quadrants ab initio for detailed discussion in the cited article [ 13 ].

Perhaps the most important challenge in computational biology is the development of a tool in a quantitative approach to infer the regulatory networks from experimental data on morphology of Planaria. An in vitro simulation approach aided by a machine learning module is used to build regulatory networks from experimental data [ 14 ].

Virtual worms and simulated experiments are tested by network model to understand pattern formation and algorithm is designed to compare the resultant phenotypes from the simulation studies with real data from planarian database.

We refer the readers to the cited article [ 14 ] for a detailed discussion on the analytical processes and algorithms. In another study the pattern formation during development is studied [ 15 ] from experimental phenotypic morphological data to determine the regulatory networks based on published results in Planarian regeneration [ 14 ], [ 15 ]. PlanformDB provides information on experiments on Planarian morphologies, regeneration and manipulations.

It enables a graphical interface with interactive graphs that enable easy to query and user friendly study of Planaria biology [ 15 ], [ 16 ]. The Schmidtea mediterranea Genome Database SmedGD is designed by integrating data associated with the Planarian genome, including predicted and annotated genes, expressed sequence tags ESTs , protein and gene expression patterns and RNA interference RNAi phenotypes in a single web portal and is a powerful tool to enable the study of Planaria biology [ 17 ].

SmedGD provides data structures compatible with other model organism databases and thus is instrumental in the study of developmental and evolutionary biology, comparative genomics, stem cell biology and regeneration and comparative genomics with other databases like Flybase and Wormbase [ 17 ]. The study of regulatory networks in the development and regeneration of Planaria, is a complex dynamic process that is self-regulated and has been modelled for identifying the underlying control mechanisms responsible for the dynamic regulation in regeneration and growth [ 14 ].

Computational tools have undoubtedly helped immensely in documenting, analysing and recording of high throughput data in biological sciences.

Application of computational tools [ 2 ], [ 3 ], [ 8 ], [ 9 ], [ 10 ], [ 11 ], [ 12 ], [ 13 ], [ 14 ], [ 15 ], [ 16 ], [ 17 ], [ 18 ] in the understanding of the Planaria biology is but a very recent approach developed in the last decade Figure 1. Even at its infancy, the strategies immensely promise at better understanding of Planaria biology analysing the experimental data.

The era of transcriptomics has generated huge data in all sphere of biology and also in Planaria biology, however, their analysis through efficient computational tools and resources are being helpful in deciphering the complexity in Planaria. Still there are many questions in Planaria related to its entire network of functioning of the stem cells, immune system and neurobiology which are not yet understood in a holistic approach in Planaria. The challenge for either experimental or computational biology still remains at targeting these vital questions to understand completely the Planaria biology.

Scope remains in designing of the biochemical pathways in Planarians to understand the role in regeneration. The future of this article remains at the designing of an integrated approach of experimental and computational resources towards the understanding of complex biology of Planaria. We propose a unique model, to understand the genes and proteins involved in the regeneration pathway comprising the signalling cascades Table 2 in the Planarian stem cell or neoblast and their structural-functional correlation with biochemical pathways involved and their comparison with the normal somatic cells, through both experimental and computational approaches, so that the information is not only restricted to the genes and proteins involved in the regeneration but also bears direct correlation of the signalling pathways downstream controlling the Planarian regeneration.

Such biomolecules recorded from neoblast cells when compared with the somatic cells would help in the understanding of the uniqueness of pathways in Planarian stem cell. We also propose to incorporate the information on homology of such proteins reported from other known organisms so as to decode the uniqueness of Planarian regeneration biology in structure and function in a systems biology approach.

Conflict of interest statement: Authors state no conflict of interest. A new higher classification of planarian flatworms Platyhelminthes, Tricladida. J Nat Hist ;— Stem cell systems and regeneration in planaria. Dev Genes Evol. Scientists want to better understand the process of regeneration. And all of these processes need to be carefully coordinated in order for regeneration to go on properly.

Many of the same genes and developmental processes that drive regeneration in planarians are present in humans as well. We recently reached out to Dr. From Quarks to Quasars: In your opinion, what is it that makes planarians so unique and worthy of study? We know more of what goes on at the center of a star than about what makes life tick.

In this sense, every single species that we can look at on Earth is unique. Recently, planarians are being rediscovered as useful organisms to try to better understand aspects of fundamental biology.

And do you think that there are any specific ways that the renewed focus on planarians could be particularly useful to humanity or to the sciences in general? OP: Traditionally, planarians were a favorite research subject on regeneration and developmental biology. These are the little critters that we usually associate with regeneration. Many planarian species display this ability.

You can cut them up in several pieces and each piece can regenerate into a complete animal. Other organisms have this capacity, but very few of them are more proficient at that than planarians. Moreover, these guys possess a relatively complex nervous system, which can get fully regenerated.