Influencia materna en la morfometría larvaria del cangrejo de pinzas pincel Hemigrapsus takanoi (Decapoda: Brachyura)

The morphology of larvae is a key factor influencing their behaviour, performance and ultimately their survival. There is evidence indicating a significant morphological variability among broods, and that this may be related to the size or conditions of the mother. However, this maternal influence is not consistent across decapod crustaceans. Using 35 broods from different mothers of the crab Hemigrapsus takanoi collected in the same locality of inner Tokyo Bay and at the same time, we tested the hypothesis that there is a positive relationship between the size of the mother and the progeny’s morphology. Our results indicate that different patterns in the length of the lateral, rostral and dorsal spines differentiated two distinct morphogroups of larvae. These morphogroups were linked to the size of the mother, showing that larger mothers produced bigger larvae with longer carapace spines. It is possible that larger size and longer spines can influence swimming performance and predator avoidance, respectively. These relationships should be tested in future experimental studies.La morfología larvaria es un factor clave que influencia el comportamiento, rendimiento y en último lugar la supervivencia larvaria. Hay evidencias que indican una variabilidad morfológica significativa entre puestas, y que esto puede estar relacionado con la talla y condición de la madre. Sin embargo, la influencia materna no es consistente para todos los crustáceos decápodos. Usando 35 puestas de diferentes madres del cangrejo Hemigrapsus takanoi, recolectadas en la misma localidad en el interior de la Bahía de Tokio, y al mismo tiempo, testeamos la hipótesis de que hay una relación positiva entre la talla de la madre y la morfología de la progenie. Nuestros resultados indican que diferentes patrones de longitud de las espinas laterales, rostrales y laterales diferencian dos morfogrupos distintos de larvas. Esos morfogrupos se asociaron a la talla de la madre, mostrando que aquellas madres grandes producían larvas de mayor tamaño con espinas más largas. Es posible que un tamaño mayor y espinas más largas puedan influenciar la capacidad natatoria y la evasión de predadores respectivamente. Estas relaciones deberían ser testeadas en futuros estudios experimentales

Diversification of cephalic shield shape and antenna in phyllosoma I of slipper and spiny lobsters (Decapoda: Achelata)

Slipper (Scyllaridae) and spiny (Palinuridae) lobsters show a complex life cycle with a planktonic larval phase, named phyllosoma. This unique larval form within Achelata (Decapoda) is characterized by a transparent dorsoventrally compressed body and a pair of antennae. This conspicuous morphology has been attributed to adaptive specialization of planktonic life. Early studies suggest that phyllosoma morphology has remained constant over the evolutionary history of Achelata, while recent evidence points out large morphological changes and that diversification of phyllosoma larvae is a consequence of radiation and specialization processes to exploit different habitats. Given the ecological and evolutive significance of phyllosoma, we used shape variation of the first phyllosoma stage (phyllosoma I) and a time-calibrated phylogeny of extant Achelata to study how diversification of phyllosoma I shape occurred along with the evolutionary history of Achelata. Our results show a conserved phyllosoma I with a pear-shaped cephalic shield and large antennae in spiny lobsters and older groups of slipper lobsters, yet highly specialized phyllosoma I with wide rounded cephalic shield and short antennae in younger groups of slipper lobsters. Analyses revealed two bursts of lineage diversification in mid and late history without a slowdown in recent times. Both bursts preceded large bursts of morphological disparity. These results joined with the allopatric distribution of species and convergence of phyllosoma I shapes between largely divergent groups suggest that diversification involves nonadaptive radiation processes. However, the correlation of a major direction of shape with the maximum distribution depth of adults and the occurrence of the second burst of diversification post-extinction of competitors within Achelata presuppose some ecological opportunities that might have promoted lineage and morphological diversification, fitting to the characteristic components of adaptive radiations. Therefore, we conclude that diversification of Achelata presents a main signature of nonadaptive radiation with some components of adaptive radiation

Jaderná transplantace u jiker jesetera

The development of reproductive biotechnology is opening a new window for the conservation of threatened wildlife, as a backup when all other protection policies have failed. In this sense, nuclear transfer, also called cloning, is expected to be a useful tool to preserve species that are nearly extinct or to reconstruct extinct species. Interspecific somatic cell nuclear transfer (iSCNT) application to endangered sturgeon species has a great advantage, as the reconstruction of the critically threatened species can be achieved after a single fin-cell is transplanted in the egg-cytoplasmic environment of species whose eggs are easily available in farms. In the present Ph.D. study, the sterlet, considered to be a model species for sturgeon family, has been used as the egg recipient while the Russian sturgeon and the beluga, considered to be mostly favorable for caviar consumption, as well as the albino sterlet, have been used as donor fin cells. Overall, the SCNT methodology was a very delicate multi-step procedure that required optimization of many experimental conditions with precise techniques and skillful manipulations. In this study, the crucial steps of sturgeon cloning have been tested by adjustment of the experimental conditions with intraspecific and interspecific SCNT. The study demonstrated that the iSCNT can be applied to real endangered species. In addition, after the improvement of the iSCNT technique by utilizing the mSCNT, we were able to obtain for the first time a specimen (0.8%) from the donor's origin only, while two specimens (1.6%) showed both the recipient and donor genome. These results were of high significance because the donor DNA was able to integrate into a sturgeon embryo after interspecific cloning. In all, the present Ph.D. study provides evidence that cloning with the multiple donor somatic cells can be feasible in the future. Despite the fact that sturgeon cloning faces limitations, to date it is a promising technique for their preservation

A newly developed cloning technique in sturgeons; an important step towards recovering endangered species

Several steps of sturgeon somatic cell nuclear transfer (SCNT) have been recently established, but improvements are needed to make it a feasible tool to preserve the natural populations of this group of endangered species. The donor cell position inside the recipient egg seems to be crucial for its reprogramming; therefore by injecting multiple donor somatic cells instead of a single cell with a single manipulation, we increased the potential for embryo development. Using the Russian sturgeon Acipenser gueldenstaedtii as a multiple cell donor and sterlet Acipenser ruthenus as the non-enucleated egg recipient, we obtained higher proportion of eggs developing into embryos than previously reported with single-SCNT. Molecular data showed the production of a specimen (0.8%) contained only the donor genome with no contribution from the recipient, while two specimens (1.6%) showed both recipient and donor genome. These findings are the first report of donor DNA integration into a sturgeon embryo after interspecific cloning. In all, we provide evidence that cloning with the multiple donor somatic cells can be feasible in the future. Despite the fact that the sturgeon cloning faces limitations, to date it is the most promising technique for their preservation

Energetic Implications of Morphological Changes between Fish Larval and Juvenile Stages Using Geometric Morphometrics of Body Shape

The fish body shape is a key factor that influences multiple traits such as swimming, foraging, mating, migrations, and predator avoidance. The present study describes the body morphological changes and the growth trajectories during the transformation from 24 to 54 days post-hatching in the golden grey mullet, Chelon auratus, using geometric morphometric analysis (GMA). The results revealed a decrease in morphological variability (i.e., morphological disparity) with the somatic growth. The main changes affected head size, elongation, and widening of the body. Given that this variability could affect the metabolism, some individuals with different morphologies and in different ontogenetic developmental stages were selected to estimate their potential respiration rate using the Electron Transport System (ETS) analysis. Differences were detected depending on the developmental stage, and being significantly smaller after 54 days post-hatching. Finally, a multivariate linear regression indicated that the specific ETS activity was partially related to the fish length and body shape. Thus, our findings emphasized the relevance of larval morphological variability for understanding the physiological processes that occur during the development

First insights on otolith macroevolution

Otoliths are calcified structures located in fishes’ inner ear involved in both hearing and equilibrium functions. Although their shapes are known to be species-specific, we still lack evidence of the evolutionary forces driving their disparity, i.e. their morphological diversity. To better understand the pattern of their shape diversification, we collected otoliths in 697 species from 68 orders and 309 families. We used geometric morphometric methods to quantify the size and the shape of both mesial and dorsal views. Phylogenetic information was recovered from pruning the consensus time-tree from Betancur et al. (2013). First, we found significant but low phylogenetic signal on shape and size variation as well as size being a poor predictor of otolith shape variation across taxa. Next, we revealed strong morphological covariation between lateral and dorsal views. Surprisingly, we also found high covariation between lateral otolith and its sulcus outline suggesting their evolution mirror each other. Finally, we found the accumulation of otolith disparity is unrelated to the age of the taxonomic group when we highlighted a higher lateral shape and dorsal size disparity in clades evolving at faster rates. Our analyses at a very large phylogenetic scale demonstrate how the diversification of otoliths is not random and is probably driven by various morpho-functional constraints. We ask for further studies focusing on eco-morphological hypotheses to reveal more macroevolutionary drivers of inner ear functional morphology

Evolutionary morphology of the saccular otolith at a large phylogenetic scale

To date, we still lack evidence of the evolutionary forces driving the diversity of sagittae. To better understand the pattern of their shape diversification, we collected the largest dataset of teleost fish otoliths, including 697 species from 68 orders and 309 families. We used geometric morphometric methods to quantify the mesial and dorsal faces. Phylogenetic information was recovered from pruning the consensus time-tree from Betancur et al. (2017). First, we found little evidence of phylogenetic signal on size and shape variation across taxa. Then, we fitted various models of continuous trait evolution to decipher the main dynamic of otolith evolution. Among tested models (e.g. Brownian motion, accelerating and decelerating models), the Ornstein-Uhlenbeck model with a single optimal trait value for all taxa was the best supported. Globally, results from tests of phylogenetic signal and trait modeling reveal that species trait value are uncorrelated. Convergence would be a good candidate to explain such an evolutionary pattern. Next, we assessed morphological integration between sulcus and otolith outline and we surprisingly found high morphological covariation. Finally, we found the accumulation of otolith disparity is unrelated to orders’ age but we highlighted a tendency of higher shape (and not size) diversity in clades evolving at faster rates. Our preliminary analyses reveal that the evolution of sagittae is not random. Shape convergence at high taxonomic scales probably highlights morpho-functional constraints. We ask for further studies focusing on eco-morphological hypotheses to reveal more macroevolutionary drivers of in inner ear functional morphology