Larval Tissues Research Articles

The stoichiometry of larval anuran development in natural wetlands

Understanding the influence of growth and development on the stoichiometry of organisms with complex lifecycles is necessary to understand the spatial and temporal extent of consumer-driven nutrient dynamics. This can be particularly challenging in temporally variable habitats, such as geographically isolated wetlands (GIW), which dry down seasonally. Larval anurans (tadpoles) are excellent model organisms for studies within the framework of ecological stoichiometry because they undergo major anatomical changes during metamorphosis that likely require a shift in body stoichiometric demands. To examine stoichiometry of larval anurans in GIWs, we measured larval Lithobates sphenocephalus tissue carbon (C), nitrogen (N), phosphorus (P) and calcium (Ca) content, excretion NH4-N, TDN and TDP, and egestion C, N and P across three developmental stage categories (no limbs, hind limbs only, and four limbs). We found that tissue P content increased significantly during later stages when bone development was occurring, which significantly reduced tissue C:P and N:P. Tissue C also increased across stages. Mass-specific excretion of TDN and N:P decreased across stages. Per capita NH4-N excretion rate had a positive relationship with body size, and per capita excretion N:P had a negative relationship with body size. Mass specific bulk egestion and C egestion varied across stages, as well as C:N and C:P, but we could not distinguish which stages were different from one another. Per capita egestion rates of N and P were positively correlated with body size, and both C:N and C:P were negatively related to body size. We found that development stage of larval anurans was an important indicator of tissue, excretion, and egestion stoichiometry and these differences may influence their functional role in aquatic ecosystems throughout their development.

Infection with Spodoptera litura NPV Reduces Food Consumption and Weight Gain of Spodoptera litura Larvae

Insect-pathogenic baculoviruses have established potential as biological insect pest control agents. However, slow speed of kill relative to chemicals and continued feeding following application limit their effectiveness in preventing crop losses. Here we studied the food consumption and weight gain of the cotton leafworm Spodoptera litura following application of two viral doses of Spodoptera litura nucleopolyhedrovirus (Pakistan isolate SpltNPV-Pak-BNG). Infected larvae with final polyhedrosis (disease resulting in dissolution of larval tissues and accumulation of viral occlusion bodies) exhibited reduced food intake and weight gain relative to uninfected larvae. The unexposed larvae and the larvae that were exposed but survived exhibited the same food consumption and weight gain. This study did thus not reveal any sub-lethal effects of exposure to the virus on food consumption and weight gain. There was no viral dose dependency observed in food intake or weight gain by infected larvae, suggesting there is no increased crop damage upon virus treatment but rather a decrease to be expected.

Lactate dehydrogenase and glycerol-3-phosphate dehydrogenase cooperatively regulate growth and carbohydrate metabolism during Drosophila melanogaster larval development.

The dramatic growth that occurs during Drosophila larval development requires rapid conversion of nutrients into biomass. Many larval tissues respond to these biosynthetic demands by increasing carbohydrate metabolism and lactate dehydrogenase (LDH) activity. The resulting metabolic program is ideally suited for synthesis of macromolecules and mimics the manner by which cancer cells rely on aerobic glycolysis. To explore the potential role of Drosophila LDH in promoting biosynthesis, we examined how Ldh mutations influence larval development. Our studies unexpectedly found that Ldh mutants grow at a normal rate, indicating that LDH is dispensable for larval biomass production. However, subsequent metabolomic analyses suggested that Ldh mutants compensate for the inability to produce lactate by generating excess glycerol-3-phosphate (G3P), the production of which also influences larval redox balance. Consistent with this possibility, larvae lacking both LDH and G3P dehydrogenase (GPDH1) exhibit growth defects, synthetic lethality and decreased glycolytic flux. Considering that human cells also generate G3P upon inhibition of lactate dehydrogenase A (LDHA), our findings hint at a conserved mechanism in which the coordinate regulation of lactate and G3P synthesis imparts metabolic robustness to growing animal tissues.

Tissue-dependent induction of antimicrobial peptide genes after body wall injury in house fly (Musca domestica) larvae.

Injury of the insect body wall, which enables environmental microorganisms to invade into insect tissues, induces innate immune responses including the induction of antimicrobial peptides (AMPs) in flies and silkworms. Here, house fly (Musca domestica) larvae and pupae were injured using a needle and the effects on the expression of genes encoding AMPs were examined. The expression of AMP genes including defensin, attacin, diptericin, and sarcotoxin II dramatically increased in both larvae and pupae after injury of the body wall, indicating that innate immune responses were induced. Furthermore, the injury-dependent expression of AMP genes was examined in larval tissues including fat bodies, hemocytes, salivary glands, and digestive tracts. Injury-dependent AMP gene expression was observed in salivary glands, hemocytes, and fat bodies, but not in digestive tracts. The degree of the transcriptional induction of each gene differed among tissues, suggesting that their expression is governed by complex regulatory machinery and that AMPs have tissue-specific functions. To further examine the properties of the AMPs, we examined the antimicrobial activities of partial synthetic peptides corresponding to portions of the predicted AMP proteins deduced from the AMP genes. A synthetic peptide exhibited antimicrobial activity, indicating that these injury-inducible genes are potential medicinal resources.

A tissue communication network coordinating innate immune response during muscle stress.

Complex tissue communication networks function throughout an organism's lifespan to maintain tissue homeostasis. Using the genetic model Drosophila melanogaster, we have defined a network of immune responses that are activated following the induction of muscle stresses, including hypercontraction, detachment and oxidative stress. Of these stressors, loss of the genes that cause muscle detachment produced the strongest levels of JAK-STAT activation. In one of these mutants, fondue (fon), we also observe hemocyte recruitment and the accumulation of melanin at muscle attachment sites (MASs), indicating a broad involvement of innate immune responses upon muscle detachment. Loss of fon results in pathogen-independent Toll signaling in the fat body and increased expression of the Toll-dependent antimicrobial peptide Drosomycin. Interestingly, genetic interactions between fon and various Toll pathway components enhance muscle detachment. Finally, we show that JAK-STAT and Toll signaling are capable of reciprocal activation in larval tissues. We propose a model of tissue communication for the integration of immune responses at the local and systemic level in response to altered muscle physiology.

Analysis of neural activity with fluorescent protein biosensors.

Fluorescent calcium sensors provide a means of detecting and analyzing cytoplasmic calcium levels in embryos and larvae. Conventional RNA injection of eggs results in expression of protein sensors throughout larval tissues. Larvae are immobilized for wide field or confocal recordings and video records reveal recurrent fluctuations in cytoplasmic calcium levels in several cell types. Neurons can be identified by location and form, and continuous records made of their activity. Confocal image stacks are registered and Z-axis, fluorescence intensity profiles of individual neurons generated to provide time/activity plots. These optogenetic methods enable analysis in intact larvae of the activity of identified neurons or effectors, such as muscles or ciliary band cells.

Parameters of oxidative stress, cholinesterase activity, Cd bioaccumulation in the brain and midgut of Lymantria dispar (Lepidoptera: Lymantriidae) caterpillars from unpolluted and polluted forests

Cadmium (Cd) can display a variety of different effects on living organisms. The objectives of the present study were to investigate Cd bioaccumulation and differences in parameters of oxidative stress (activities of the enzymes: superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase, glutathione S-transferase, and amounts of non-enzymatic free sulfhydryl groups and total glutathione) and cholinesterase activity in larval brain and midgut tissues of the polyphagous forest insect Lymantria dispar collected from unpolluted and polluted oak forests. Fourth instar L. dispar caterpillars from the unpolluted forest had higher body mass but accumulated more Cd in comparison to caterpillars from the polluted forest. In both populations the midgut was more sensitive than the brain to the prooxidative effects of Cd. Enzyme activities and amounts of non-enzymatic parameters tended to be greater in midgut tissues than in the brain, except for cholinesterase activity. Parameters of oxidative stress had higher values in caterpillar tissues from the polluted than from the unpolluted oak forest. The observed differences between the two natural populations point to the importance of knowing the history of population exposure to environmental pollution when monitoring forest ecosystems.

Nutrition and water temperature regulate the expression of heat-shock proteins in golden pompano larvae (Trachinotus ovata, Limmaeus 1758).

Understanding fish larval development is of a great interest for aquaculture production efficiency. Identifying possible indicators of fish larvae stress could improve the production and limit the mortality rate that larval stage is subjected to. Heat-shock proteins (HSPs) and heat-shock factors (HSFs) are well known as indicators of response to many kinds of stressor (e.g., environmental, morphological, or pathological changes). In this study, golden pompano larvae were raised at different temperatures (23°C, 26°C, and 29°C), as well as three different diets (Artemia nauplii unenriched, Artemia nauplii enriched with Nannochloropsis sp., and Artemia nauplii enriched with Algamac 3080), and the expression of HSP60, HSP70, HSF1, HSP2, and GRP94 were monitored. While stress genes were widely expressed in the larval tissues, HSP60 and HSP70 were principally from the gills and heart; HSF1 principally from the muscle, brain, and heart; and GRP94 principally from the head kidney and spleen. Golden pompano larvae were found to be more sensitive to thermal changes at later larval stage, and 29°C was showed to likely be the best condition for golden pompano larval development. Nannochloropsis sp.-enriched Artemia nauplii treatment was found to be the most appropriate feed type with moderate relative expressions of HSP60, HSP70, HSF1, HSF2, and GRP94.

Influence of salinity and linoleic or α-linolenic acid based diets on ontogenetic development and metabolism of unsaturated fatty acids in pike perch larvae (Sander lucioperca)

Combinations of nutritional requirements and husbandry rearing conditions during early ontogeny are poorly studied in pikeperch (Sander lucioperca). The substitution of marine oils with vegetable oils has reduced stress tolerance and caused neurophysiological changes in pike perch larvae, but effects of environmental cues are limited. Saline water influences on a range of physiological functions during early fish larval ontogeny and may affect FA metabolism, − elongation and desaturation - activity when given diets limited in LC PUFAs, but rich in shorter chain n-3 or n-6 PUFAs. Consequently, live Artemia differing in 18:2n-6 (LA) and 18:3n-3 (ALA) content by enrichment with sunflower oil (SFO) or linseed oil (LO) were fed to 10 days post hatch (DPH) larvae and reared up to isosmotic salinities (0, 5, 10 ppt) until 30 DPH. Larval tissue FA composition was examined at 15, 25 and 30 DPH. Besides, an in vivo assay was performed on 20 DPH larvae with 14C labelled FA including LA; ALA; 20:4n-6 (ARA); 20:5n-3 (EPA) or 22:6n-3 (DHA) to establish FA incorporation and metabolism. At 30 DPH, performance, digestive enzymatic activity, eicosanoid activity, skeletal anomalies and stress sensitivity were further evaluated. Results on larval FA profiles suggest a low desaturation and elongation capability over LA and ALA, with no significant effects of salinity or larval age on modulation of unsaturated fatty acid metabolism. In vivo assays revealed that regardless of salinity or diet, pikeperch possess a marked specificity to incorporate ARA and EPA compared to a poorer incorporation of DHA. Larvae exposed to a confinement stress test caused high acute mortality in all experimental groups except for a control group fed with Artemia enriched by a commercial DHA Selco emulsion. Growth performance was not significantly affected by salinity or dietary enrichment with SFO or LO, but influenced on larval enzymatic activity of pepsin, aminopeptidase, trypsin and alkaline phosphatase, while lipase activity was not significantly affected. Increased saline conditions significantly decreased hormonal prostaglandin eicosanoid PGE2, PGE3 activity with the highest activity at 0 ppt. The prevalence of severe skeletal anomalies was generally high, affecting over 75% of the larval population with negative effects by increase in salinity. The incidence of anomalies was higher on endochondral bones, namely maxillary, ranging from 58 to 83% of the population. These results agree well with those from expression of sox 9 and twist2 genes; involved in chondrocyte ossification and differentiation.

Characterization of cell lines derived from the southern armyworm, Spodoptera eridania.

Spodoptera eridania (southern armyworm) is a polyphagous pest of many plants, including field crops, vegetables, fruits, and ornamentals. Larvae are leaf feeders, defoliating many crops in the tropics and subtropics of the western hemisphere. In this study, cell lines from S. eridania were established to support research focused on the development of advanced pest management technologies. We generated seven cell lines from larval tissues: three from nervous tissues, two from testes, and two from fat bodies. These cell lines have been passaged 18-57 times, indicating they are established lines. They are maintained in EX-CELL 420 or a combination of L15 + EX-CELL 420 media. The identities of the cell lines were confirmed by DAF-PCR and their doubling times ranged from 42 to 110h. Microscopy indicated the presence of one or more morphologically distinct cell types in each cell line. We identified a catalase gene in all seven cell lines. H2O2 treatment suppressed the expression of catalase and led to a reduction in catalase activity. This is the first report of cell lines established from S. eridania, and these cell lines are now available to researchers worldwide on request.

Multiple functions of miR-8-3p in the development and metamorphosis of the red flour beetle, Tribolium castaneum.

The microRNA miR-8-3p is conserved among insects and closely involved in development and immunity, but its functions in vivo are unexplored in the red flour beetle, Tribolium castaneum. Here, we show that miR-8-3p was highly expressed in late larva and early adult stages, as determined by quantitative real-time PCR. It was enriched in the fat body and cuticle in late larval tissues and abundant in the head and cuticle in early adult tissues, indicating this microRNA plays important roles during T.castaneum development. Specific inhibition of miR-8-3p in late larvae led to metamorphosis defects in the development of wings, eyes, legs and embryo. Moreover, a series of genes related to organism development were identified as miR-8-3p targets by computational prediction and microRNA-messenger RNA interaction validation, including Wingless, Eyg, Fpps and Sema-1a. These genes were critical for the regulation of the larva-to-adult transition. Eyg, as a functional target of miR-8-3p, participates in eye development, which was further confirmed by luciferase assay and loss-of-function analyses. In brief, miR-8-3p is broadly involved in the development of wings, eyes and legs through its target genes and has extensive regulatory roles during T.castaneum development.

Identification and expression analysis of the Spodoptera exigua neuropeptidome under different physiological conditions.

Neuropeptides are small signalling molecules acting as neurohormones, neurotransmitters and neuromodulators. Being part of the chemical communication system between cells within an organism, they are involved in the regulation of different aspects of animal physiology and behaviour such as feeding, reproduction, development and locomotion. Transcriptomic data from larval and adult tissues have been obtained and mined to generate a comprehensive neuropeptidome for the polyphagous insect pest Spodoptera exigua. Sixty-three neuropeptides have been identified and described based on their tissue specificity and their regulation in response to different abiotic perturbations. Expression analyses have identified those neuropeptides involved in ingestive and digestive behaviour of S.exigua larvae and revealed a general pattern of upregulation in the midgut during larval starvation. Our results represent a comprehensive neuropeptidome of a lepidopteran species that will be highly relevant to future studies and provide novel information of the insect's perception of its environment.

Validation of reference gene(s) for quantitative gene expression profiling using rice moth, Corcyra cephalonica as a model

Many techniques are available for the quantification of specific mRNA from various tissues of an organism. Among them qRT-PCR is a widely used method, as this is a rapid and requires low quantity of mRNA. The reliability of the data depends on accurate normalization using appropriate internal control(s). The use of constitutively expressed genes (house-keeping genes, HKGs) such as α-actin, β-tubulin and GAPDH as internal controls or reference genes is a widely accepted method for qRT-PCR data normalization. However, expression of HKGs may vary at different developmental stages or during hormone manipulation studies. The present study was carried out using a holometabolous lepidopteran stored grain pest Corcyra cephalonica (rice moth). Seven different constitutively expressed genes α-actin, β-tubulin, 18S rRNA, TBP, rS7, GAPDH, and EF1α were analysed as internal reference genes in various larval tissues. Further the stable gene was characterized during various conditions like ontogeny, hormonal depletion and exogenous hormone application. Gene expression stability was obtained by measuring the M-value for HKGs. The findings indicate that 18S rRNA was suitable as reference gene under normal physiological conditions, tissue distribution and also upon methoprene (JH analog) treatment. On the other hand rS7 was suitable for ecdysteroid treatment related analysis. Present study once again reinforces that, reference genes cannot be universal and need to be validated not only for a given organism but also during various conditions.

The role of macroinvertebrates in the distribution of lead (Pb) within an urban marsh ecosystem

Environmental risk from contaminated aquatic sediments requires an understanding of its spatial distribution, bioavailability and rate of transfer to resident aquatic and terrestrial biota. We hypothesized that macroinvertebrates play a role in the sequestration, distribution, and dispersal of lead from lead shot contaminated sediments. To assess this, we sampled the predominant aquatic macroinvertebrate, Leptocerus americanus, from sites within the La Crosse River Marsh (La Crosse, Wi) identified to contain high levels of lead contamination. We measured lead content in larval cases, larval tissues and emergent adult tissues. Lead concentrations within whole larvae correlated with levels of lead within sediments, and lead was differentially partitioned between larval tissue and their silk cases. Over 90% of the lead was retained in larval cases, while the rest was distributed to the body tissue, which was largely conserved during the process of metamorphosis. Our models support that L. americanus emerging from the marsh in the contaminated area transfer as much as 160 mgPb out of the aquatic habitat each year. Our work demonstrates that macroinvertebrates affect the mobilization and dispersal of contaminants within aquatic sediments, and this role should be evaluated when making management decisions regarding contaminated ecosystems.

Dissection of Nidogen function in Drosophila reveals tissue-specific mechanisms of basement membrane assembly.

Basement membranes (BMs) are thin sheet-like specialized extracellular matrices found at the basal surface of epithelia and endothelial tissues. They have been conserved across evolution and are required for proper tissue growth, organization, differentiation and maintenance. The major constituents of BMs are two independent networks of Laminin and Type IV Collagen in addition to the proteoglycan Perlecan and the glycoprotein Nidogen/entactin (Ndg). The ability of Ndg to bind in vitro Collagen IV and Laminin, both with key functions during embryogenesis, anticipated an essential role for Ndg in morphogenesis linking the Laminin and Collagen IV networks. This was supported by results from cultured embryonic tissue experiments. However, the fact that elimination of Ndg in C. elegans and mice did not affect survival strongly questioned this proposed linking role. Here, we have isolated mutations in the only Ndg gene present in Drosophila. We find that while, similar to C.elegans and mice, Ndg is not essential for overall organogenesis or viability, it is required for appropriate fertility. We also find, alike in mice, tissue-specific requirements of Ndg for proper assembly and maintenance of certain BMs, namely those of the adipose tissue and flight muscles. In addition, we have performed a thorough functional analysis of the different Ndg domains in vivo. Our results support an essential requirement of the G3 domain for Ndg function and unravel a new key role for the Rod domain in regulating Ndg incorporation into BMs. Furthermore, uncoupling of the Laminin and Collagen IV networks is clearly observed in the larval adipose tissue in the absence of Ndg, indeed supporting a linking role. In light of our findings, we propose that BM assembly and/or maintenance is tissue-specific, which could explain the diverse requirements of a ubiquitous conserved BM component like Nidogen.

Embryonic development of thecate hydrozoan Gonothyraea loveni (Allman, 1859).

Progress of Evo-Devo requires broad phylogenetic sampling providing the data for comparative analysis as well as new objects suitable for experimental investigation. Representatives of the early-branching animal phylum Cnidaria and particularly hydrozoans draw great attention due to the high diversity of embryonic and post-embryonic development and life-cycles in general. Most detailed studies on embryonic development in hydrozoans were performed on the species shedding their gametes with subsequent embryo development in the water column. Widely distributed thecate hydrozoan Gonothyraea loveni broods its embryos within reduced medusae attached to the colony until development of a free-swimming metamorphosis competent planula-larva. In the current essay we present a detailed description of G.loveni embryonic development based on in vivo observations, histology, immuno-cytochemistry, and electron microscopy. Starting from early cleavage, the embryo becomes a morula without any sign of blastocoele. Gastrulation proceeds as mixed delamination and ends with parenchymula formation. The first morphological sign of primary body axis appears only in the beginning of parenchymula-preplanula transition. In mature metamorphosis competent planula only the cells of the oral two-thirds of endoderm retain proliferative activity resulting in accumulation of great number of i-cells and nematoblasts, which can be used during metamorphosis accompanied with essential reorganization of larval tissues. G.loveni demonstrates the diversity as well as evolutionary plasticity of hydrozoans development: in brooding hydrozoans embryonic and larval development is highly embryonized in comparison with the spawning species with free-swimming embryos.

Hyperspectral Imaging of Macroinvertebrates—a Pilot Study for Detecting Metal Contamination in Aquatic Ecosystems

The applicability of spectral analysis in detection of freshwater metal contamination was assessed by developing and testing a novel hyperspectral imaging (HSI) application for aquatic insect larvae (Trichoptera: Hydropsychidae). Larvae were first exposed to four different cadmium (Cd) concentrations: 0, 1, 10, and 100 μg L−1 for 96 h. Individual larvae were then preserved in ethanol, inspected with microscopy for the number of anomalies in larval gills, and imaged by hyperspectral camera operating with wavebands between 500 and 850 nm. Three additional larvae from each exposure were analyzed for tissue Cd concentration. Although the larval tissue Cd concentrations correlated positively with actual water concentrations, the toxicity response of larvae, i.e., frequency of gill abnormalities, did not differ among the Cd concentrations. In contrast, hyperspectral imaging data indicated some concentration-response relationship of larval spectral properties to the Cd exposure, but it was too weak for reliable automatic distinction between exposed and unexposed larvae. In this pilot study a workflow for data processing for a novel application of hyperspectral imaging was developed. Based on the results of this preliminary study, the workflow in the imaging process will be optimized and its potential for detecting metal contamination of aquatic environments reassessed.

Single transcript imaging to assay gene expression in wholemount Drosophila melanogaster tissues

Single molecule Fluorescence in situ Hybridization (smFISH) for mRNA provides a powerful quantitative handle on expression from endogenous gene loci. While the method has been widely applied in cells in culture, applications to primary tissue samples remain fewer, and often use involved cryosectioning. Even apart from quantitative access to absolute transcript counts in specific tissue volumes, many other advantages of smFISH can be envisaged in tissue samples. Primary among these are the ability to report on subtle differences in expression among different cell types within a tissue, and the ability to correlate the expression from different target genes. Here, we present a modified method of smFISH applicable on various primary wholemount tissues from the fruit fly Drosophila melanogaster, and show the efficacy of the method in a variety of larval and adult tissue, and embryos. We also combine smFISH in tissue with immunofluorescence to demonstrate the possibility of capturing transcriptional and translational aspects of gene expression in the same tissue. Given the widespread use of Drosophila melanogaster as a model system in Developmental Biology and Genetics, such methods are likely to be of wide interest and could yield rich information about gene expression in tissues from this organism.

20-Hydroxyecdysone-upregulated proteases involved in Bombyx larval fat body destruction.

During insect larval-pupal metamorphosis, the obsolete larval organs and tissues undergo histolysis and programmed cell death to recycle cellular materials. It has been demonstrated that some cathepsins are essential for histolysis in larval tissues, but the process of tissue destruction is not well documented. Fat body, the homologous organ to mammalian liver and adipose tissue, goes through a distinct destruction process during larval-pupal transition. Herein, we found that most of the Bombyx proteases - including Bombyx cathepsin B (BmCatB) (BmCatLL-2), Bombyx cathepsin D (BmCatD), Bombyx cathepsin L like-1 (BmCatLL-1) and -2(BmCatLL-2), Bombyx fibroinase (BmBcp), Bombyx matrix metalloprotease (BmMmp), Bombyx A disintegrin and metalloproteinase with thrombospondin motifs 1 (BmAdamTS-1), Bombyx A disintegrin and metalloproteinase with thrombospondin motifs like (BmAdamTS L) and Bombyx cysteine protease inhibitor (Bmbcpi)- were expressed highly in fat body during feeding and metamorphosis, with a peak occurring during the nonfeeding moulting or prepupal stage, as well as being responsive to 20-hydroxyecdysone (20E). The aforementioned protease genes expression was upregulated by injection of 20E into the feeding larvae, while blocking 20E signalling transduction led to downregulation. Western blotting and immunofluorescent staining of BmCatB and BmBcp confirmed the coincident variation of their messenger RNA (mRNA) and protein level during the development and after the treatments. Moreover, BmCatB, BmBcp, BmMmp and BmAdamTS-1 RNA interference all led to blockage of larval fat body destruction. Taken together, we conclude that 20E regulates larval fat body destruction by upregulating related protease gene expression and protein levels during larval-pupal transition.

Mechanical Mapping of Spinal Cord Growth and Repair in Living Zebrafish Larvae by Brillouin Imaging

The mechanical properties of biological tissues are increasingly recognized as important factors in developmental and pathological processes. Most existing mechanical measurement techniques either necessitate destruction of the tissue for access or provide insufficient spatial resolution. Here, we show for the first time to our knowledge a systematic application of confocal Brillouin microscopy to quantitatively map the mechanical properties of spinal cord tissues during biologically relevant processes in a contact-free and nondestructive manner. Living zebrafish larvae were mechanically imaged in all anatomical planes during development and after spinal cord injury. These experiments revealed that Brillouin microscopy is capable of detecting the mechanical properties of distinct anatomical structures without interfering with the animal’s natural development. The Brillouin shift within the spinal cord remained comparable during development and transiently decreased during the repair processes after spinal cord transection. By taking into account the refractive index distribution, we explicitly determined the apparent longitudinal modulus and viscosity of different larval zebrafish tissues. Importantly, mechanical properties differed between tissues in situ and in excised slices. The presented work constitutes the first step toward an in vivo assessment of spinal cord tissue mechanics during regeneration, provides a methodical basis to identify key determinants of mechanical tissue properties, and allows us to test their relative importance in combination with biochemical and genetic factors during developmental and regenerative processes.