Variation In Body Length Research Articles

Habitat alters biogeographical and evolutionary patterns of body size in freshwater crayfishes

Abstract Biogeographical patterns explain variation in body size, although the strength and directions of these patterns vary. When researchers account for the micro- or macrohabitats that species inhabit, they often find that biogeographical relationships with body size are modified, especially in taxa that inhabit diverse environments. Freshwater crayfishes are an ideal group in which to study the interaction between habitat, biogeography, and body size, because there are >700 crayfishes that inhabit aquatic environments, semi-terrestrial burrows, and caves. Here, we explore evolution of body size across 452 species of crayfish by considering the interaction between their habitats (aquatic, semi-terrestrial/aquatic, semi-terrestrial, and cave-dwelling) and the mean temperature of their geographical range. We documented 64-fold variation in body length. Aquatic species were the largest and had the greatest variation in body size. Crayfishes that inhabit both semi-terrestrial and aquatic habitats exhibit a weak negative relationship between body size and environmental temperature; solely aquatic species reverse this relationship. Evolutionarily, our ancestral reconstruction suggests that the ancestral crayfish was an aquatic species with a body length of 81.1 mm, which aligns with data from fossil crayfish. Overall, our study highlights how uniting biogeographical and evolutionary approaches improves our ability to explore patterns of animal body size and unearth explanatory mechanisms.

A novel mathematical model and application software for estimating the age of necrophagous fly larvae

The change in larval body length of necrophagous flies during their development is a key indicator for estimating larval age. However, existing forensic entomological models have limitations in this regard. In this study, a logistic algorithm was used to establish a general model for estimating the minimum postmortem interval (PMImin) using larval body length. The new model was used to simulate the relationship between larval body length and developmental time of eight species of necrophagous flies. The model parameters of body length variation with developmental time of the different species were calculated. Computer software was developed based on the established logistic model. The advantage of the new model is that each parameter has a biological meaning and can be used to estimate the age of larvae at any temperature and any larval body length. Cross-validation of the model showed that the overall mean accuracy of the fitted growth curves for the eight necrophagous fly larvae was 82.7%, the mean accuracy of age extrapolations for seven necrophagous fly species ranged from 76.8% to 92.9%, while the accuracy of age extrapolations for only one species was lower (i.e., 63.3%). This study provides a new method to estimate the PMImin based on larval body length, and the developed computer software will facilitate its application in forensic entomology.

Forest conversion into pasture selects dung beetle traits at different biological scales depending on species pool composition.

The conversion of forests into open areas has large effects on the diversity and structure of native communities. The intensity of these effects may vary between regions, depending on the existence of native species adapted to open habitats in the regional pool or the time since habitat change.We assess the differences in species richness and functional diversity of dung beetle communities (Coleoptera: Scarabaeinae) between native forests and novel pasturelands of the Atlantic Forest and the Cerrado, two biomes with contrasting histories of human occupation in Brazil. We conducted standardized surveys in seven forest fragments and adjacent pastures in each region and measured 14 traits in individuals collected in each type of habitat at each particular site. We calculated functional richness, functional evenness, functional divergence, and community-weighted mean of traits for each area, and analyzed individual variation through nested variance decomposition and Trait Statistics.Communities were richer and more numerous at the Cerrado. We did not find any consistent relationship between functional diversity and forest conversion beyond the changes in species diversity. Although landscape changes were more recent at the Cerrado, the colonization of the new habitat by native species already adapted to open habitats lessens the functional loss in this biome. This indicates that habitat change's effects on trait diversity depend on the regional species pool rather than on time since land conversion.Forest conversion effects were primarily due to internal filtering. The effects of external filtering only appear at the intraspecific variance level, with contrasting differences between the Cerrado, where traits related to relocation behavior and size are selected, and the Atlantic Forest, where selection operates for traits related to relocation behavior and flight. These results evidence the importance of considering individual variance to address the responses of dung beetle communities to forest conversion.

Preprocessing for Keypoint-Based Sign Language Translation without Glosses

While machine translation for spoken language has advanced significantly, research on sign language translation (SLT) for deaf individuals remains limited. Obtaining annotations, such as gloss, can be expensive and time-consuming. To address these challenges, we propose a new sign language video-processing method for SLT without gloss annotations. Our approach leverages the signer's skeleton points to identify their movements and help build a robust model resilient to background noise. We also introduce a keypoint normalization process that preserves the signer's movements while accounting for variations in body length. Furthermore, we propose a stochastic frame selection technique to prioritize frames to minimize video information loss. Based on the attention-based model, our approach demonstrates effectiveness through quantitative experiments on various metrics using German and Korean sign language datasets without glosses.

Strongly exclusive distribution with putative character displacement in two flying stag beetles

Character displacement is considered a key driver of evolutionary divergence and adaptation. Few examples of reproductive character displacement with a narrow contact zone have been identified. We examined the genetic structure, body length variation, and genital morphology in the contact and allopatric areas of Platycerus takakuwai and P. viridicuprus to investigate character displacement and gene flow. In the contact area, the species identifications based on endophallic morphology and nuclear genes were identical, whereas mitochondrial gene did not exhibit a perfect match. This incongruence suggests that interspecific hybridization followed by the mitochondrial introgression has likely occurred during historical secondary contact. The species are essentially parapatric in contact area, co-occurring at only one of 28 adjacent sampling sites despite being flying species, and no hybrids based on morphology have been found, which indicates a strongly exclusive distribution. The results showed that the body length variation was consistent with character displacement after controlling for variation along geographic and environmental gradients. Interspecific body size differentiation may have evolved to reduce incorrect mating between the species. Moreover, selective pressure caused by reproductive interference between the two species may act on body size that have likely resulted in strongly exclusive distribution at the edge of their ranges.

Variation in Body Length, Length-Weight Relationship, and Condition Factor of Lionfish (Pterois volitans) Between Years in a Mesophotic Coral Ecosystem in Alacranes Reef, Southern Gulf of Mexico

Desde hace más de 30 años el pez león del Indo-Pacífio (Pterois volitans, P. miles) fue introducido en el Atlántico Oeste, donde P. volitans ya ha alcanzado el nivel de invasión biológica que amenaza al ecosistema marino. El objetivo de este trabajo fue describir las variaciones en longitud corporal, relaciones peso-longitud (RPL) y factor de condición de P. volitans entre años en un ecosistema coralino mesofótico (ECM), en el sureste del Golfo de México, para proporcionar una línea base de datos de historia de vida. De septiembre 2014 a septiembre 2017, arponeamos 94 peces león en el mismo ECM en el Arrecife Alacranes, frente a la costa norte de la península de Yucatán, México. Hubo diferencias en longitud, con peces león más grandes en 2014 y también diferencias enre las relaciones RPLs. La RPL para todos los peces león indicó un crecimiento alométrico positivo. No hubo diferencias en la longitud entre las hembras y los machos. Los machos mostraron un factor de condición de Fulton mayor, en 2015 y 2016, en comparación con las hembras. Este estudio reveló que P. volitans ha adquirido una longitud mayor y un buen factor de condición en el ECM. Las limitaciones humanas para buceo en áreas profundas impiden la remoción mecánica de pez león por sacrificio. Se requiere de análisis más amplios para cuantificar su densidad y entender el potencial que el pez león tendría para impactar los ECMs en la región.

Paramonostomum deseado n. sp. (Digenea: Notocotylidae) parasitizing the South American Black Oystercatcher and their atypical life cycle from the Patagonian coast.

By way of morphological and molecular analysis we describe a new species of notocotylid, Paramonostomum deseado n. sp., parasitizing Haematopus ater from Argentina and we contribute to elucidate its life cycle. Within this genus, 4 groups can be morphologically distinguished according to body shape: ‘Oval’, ‘Pyriform’, ‘Elongate’, ‘Overlong’. The new species belongs to the ‘Elongate group’, which presents a wide variation in body length (597–4500 μm). The new species, Paramonostomum caeci from Australia, Paramonostomum actitidis from the Caribbean and Paramonostomum alveoelongatum from Russia share the smallest range of body size in this group (<1130 μm). The new species more closely resembles P. actitidis but differs from it by cirrus-sac length, which is shorter in the new species (97–146 vs 280–430 μm in P. actitidis), and egg size which is larger in the new species (25–33 vs 18–20 μm in P. actitidis). Paramonostomum deseado n. sp. uses the limpet Nacella magellanica as both first and second intermediate hosts in which metacercariae encyst inside the redia. This is the first abbreviated cycle described for notocotylid species. Ribosomal RNA sequences provided for adults (ITS1, ITS2 and 28S) and metacercariae inside the rediae (ITS1) support the species identification and the correspondence among stages. Phylogenetic analysis based on 28S placed P. deseado n. sp. close to other Notocotylus spp. and Paramonostomum anatis. Molecular results demonstrate that the hosts involved in the life cycles and the habitat more than morphological differences are determining the phylogenetic relationships in members of Notocotylidae.

Distinct body-size responses to warming climate in three rodent species.

In mammals, body-size responses to warming climates are diverse, and the mechanisms underlying these different responses have been little investigated. Using temporal and spatial datasets of three rodent species distributed across different climatic zones in China, we investigated temporal and spatial trends of body size (length and mass), identified the critical drivers of these trends, and inferred the potential causes underlying the distinct body-size responses to the critical drivers. We found that body mass of all species remained stable over time and across space. Body length, however, increased in one species over time and in two species across space. Generally, body-length variation was predicted best by minimum ambient temperature. Moreover, in two species, body length changed linearly with temperature differences between ancestral and colonization areas. These distinct temperature-length patterns may jointly be caused by species-specific temperature sensitivities and experienced magnitudes of warming. We hypothesize that species or populations distributed across distinct temperature gradients evolved different intrinsic temperature sensitivities, which affect how their body sizes respond to warming climates. Our results suggest that size trends associated with climate change should be explored at higher temporal and spatial resolutions, and include clades of species with similar distributions.

Proteomic Analysis of Spore Surface Proteins and Characteristics of a Novel Spore Wall Protein and Biomarker, EhSWP3, from the Shrimp Microsporidium Enterocytozoon hepatopenaei (EHP).

Enterocytozoon hepatopenaei, a spore-forming and obligate intracellular microsporidium, mainly infects shrimp and results in growth retardation and body length variation, causing huge economic losses to the Asian shrimp aquaculture industry. However, the lack of a full understanding of the surface proteins of spores associated with host infection has hindered the development of technologies for the detection of EHP. In this study, the surface proteins of EHP spores were extracted using the improved SDS method, and 130 proteins were identified via LC-MS/MS analysis. Bioinformatic analysis revealed that these proteins were enriched in biological processes (67), cellular components (62), and molecular functions (71) based on GO terms. KEGG pathway analysis showed that 20 pathways, including the proteasome (eight proteins) and the fatty acid metabolism (15 proteins), were enriched. Among 15 high-abundance surface proteins (HASPs), EhSWP3 was identified as a novel spore wall protein (SWP), and was localized on the endospore of the EHP spores with an indirect immunofluorescence and immunoelectron microscopy assay. Polyclonal antibodies against EhSWP3 showed strong species specificity and high sensitivity to the hepatopancreas of EHP-infected shrimp. As a specific high-abundance protein, EhSWP3 is therefore a promising target for the development of immunoassay tools for EHP detection, and may play a crucial role in the invasion of EHP into the host.

Resource heterogeneity but not inbreeding affects growth and grouping behaviour in socially foraging juvenile cichlid fish

Abstract Spatial food distribution determines resource profitability, defensibility and encounter rate of foragers. Clumped food distribution can promote aggressiveness and resource monopolisation, in turn increasing within‐group variation in food intake and growth. However, the effects of food distribution may depend on foraging strategies. Little is known about the impact of spatial food heterogeneity on growth and grouping behaviour in social foragers in the absence of monopolisation. Social foraging is present in many fishes, particularly at early juvenile life stages when fish are especially sensitive to environmental variation. Here, a heterogeneous food distribution may impair foraging success and growth and juveniles may increase sociability to attain social information about food resources. We examined the impact of the spatial distribution of food as well as inbreeding on growth and social behaviour in juveniles of the cichlid fish Pelvicachromis pulcher. Inbred individuals often show poorer performance than outbred individuals (inbreeding depression), but inbreeding effects can be environment dependent. In the experiment, inbred and outbred fish were reared in a split‐clutch design either under homogeneously distributed or spatially clumped food conditions for 8 weeks starting 1 week after juveniles could actively feed. We documented growth and performed a shoaling assay and a sociality test (choice between a large vs. a small shoal) after 6 weeks. Spatial food distribution did not affect within‐group body length variation, but individuals reared under clumped food conditions were smaller. Shoals of the different feeding conditions differed in social behaviour. Shoals of the clumped treatment group showed higher variation in inter‐individual distances compared to shoals of the homogeneous treatment group. Furthermore, focal fish of the clumped treatment adjusted their association preference to the position of the groups' largest individual. We did not find significant inbreeding or environment‐dependent inbreeding effects regarding growth or social behaviour. Our study suggests that a clumped food distribution can impede localisation of food resources and thus growth in juvenile social foragers. Accordingly, in heterogeneous environments, the use of social information may be highly relevant to increase individuals' foraging success potentially explaining orientation on successful foragers, that is, large individuals. Inter‐individual variation in juvenile’s social behaviour may precede variation in food monopolisation capability and in growth emerging at later life stages. A free Plain Language Summary can be found within the Supporting Information of this article.

Morphometrics and processing yield of Cucumaria frondosa (Holothuroidea) from the St. Lawrence Estuary, Canada.

Sea cucumber Cucumaria frondosa have highly variable whole body mass and length, and are usually sold to Asian markets as dried gutted body wall. Understanding the relation between size and yield of dry product is essential for resource conservation and for economic purposes. In this study, stock-specific mass and length recovery rates were estimated for C. frondosa captured by dredging or diving at various depths and seasons on the South shore of the St. Lawrence Estuary, along Gaspé Peninsula, and processed in a commercial plant. The processing yield in dry product mass per sea cucumber was more than 1.5 times larger for sea cucumbers collected at 26–47 m depth compared to those collected at 9–16 m depth. Within each strata, there was little variation in the processed body mass, seasonally or spatially. Recovery rates based on gutted mass for this stock (13.4─14.5%) varied little among depths and seasons, despite observed seasonal and bathymetric variation in reproductive status. In contrast, recovery rates based on whole body mass and length were highly variable both seasonally and spatially. Stress related to dredging or post-capture handling induced important variable body contraction and water content, leading to variation in body length, mass and shape of sea cucumbers having the same processed body mass. Gutted mass was the best metric to predict processed body mass and to estimate size whereas whole body length was the least reliable. New stock-specific information on variability of body mass, length, and recovery rates induced by capture, and on seasonal and bathymetric variation in reproductive status and processing yields will be used for the design of future stock assessment surveys, and for stock conservation.

Allometric relationships in morphological traits associated with foraging, swimming ability, and predator defense reveal adaptations toward brackish and freshwater environments in the threespine stickleback.

Freshwater colonization by threespine stickleback has led to divergence in morphology between ancestral marine and derived freshwater populations, making them ideal for studying natural selection on phenotypes. In an open brackish–freshwater system, we previously discovered two genetically distinct stickleback populations that also differ in geometric shape: one mainly found in the brackish water lagoon and one throughout the freshwater system. As shape and size are not perfectly correlated, the aim of this study was to identify the morphological trait(s) that separated the populations in geometric shape. We measured 23 phenotypes likely to be important for foraging, swimming capacity, and defense against predation. The lateral plate morphs in freshwater displayed few significant changes in trait sizes, but the low plated expressed feeding traits more associated with benthic habitats. When comparing the completely plated genetically assigned populations, the freshwater, the hybrids, the migrants and the lagoon fish, many of the linear traits had different slopes and intercepts in trait‐size regressions, precluding our ability to directly compare all traits simultaneously, which most likely results from low variation in body length for the lagoon and migrant population. We found the lagoon stickleback population to be more specialized toward the littoral zone, displaying benthic traits such as large, deep bodies with smaller eyes compared to the freshwater completely plated morph. Further, the lagoon and migrant fish had an overall higher body coverage of lateral plates compared to freshwater fish, and the dorsal and pelvic spines were longer. Evolutionary constraints due to allometric scaling relationships could explain the observed, overall restricted, differences in morphology between the sticklebacks in this study, as most traits have diversified in common allometric trajectories. The observed differences in foraging and antipredation traits between the fish with a lagoon and freshwater genetic signature are likely a result of genetic or plastic adaptations toward brackish and freshwater environments.

Adaptive changes in morph and preference induced by novel host plants mediate host specialization of the cotton–melon aphid

Flexibility and variations in morphological and physiological traits are the key for insect herbivores to adapt to environments. The cotton–melon aphid Aphis gossypii Glover is a polyphagous insect which populations exhibit host specialization. Feeding experience on specific host plants converted host specialization in this aphid. However, adaptive changes of this aphids during the host conversion are still unclear. Here, we examined variations in body length, leg segments, and host preference of the cotton-specialized and cucurbit-specialized aphids, A. gossypii, induced by novel host plants. We found that on the original host plants, body, femur, tibia, and tarsus of the cucurbit-specialized aphids were significantly longer than these of the cotton-specialized aphids. However, feeding on zucchini or cowpea resulted in the short body and leg segments in the cucurbit-specialized aphids, whereas led to the long body and leg segments or no changes in the cotton-specialized aphids, and consequently, the tarsus lengths became equal between the cotton- and cucurbit-specialized aphids. Interestingly, the change trends of the relative lengths of leg segments to body length with the increase of reared generation on zucchini were almost different between the cucurbit-specialized and cotton-specialized aphids, especially the relative length of tarsus, but on cowpea, the trends were similar. Meanwhile, feeding on zucchini altered host preference of the cotton-specialized aphids, but not of the cucurbit-specialized aphids. Novel host plants induce adaptive changes in leg segments and host preference of aphids, suggesting the conversion of host specialization.

Scaling of swimming performance in baleen whales.

The scale dependence of locomotor factors has long been studied in comparative biomechanics, but remains poorly understood for animals at the upper extremes of body size. Rorqual baleen whales include the largest animals, but we lack basic kinematic data about their movements and behavior below the ocean surface. Here, we combined morphometrics from aerial drone photogrammetry, whale-borne inertial sensing tag data and hydrodynamic modeling to study the locomotion of five rorqual species. We quantified changes in tail oscillatory frequency and cruising speed for individual whales spanning a threefold variation in body length, corresponding to an order of magnitude variation in estimated body mass. Our results showed that oscillatory frequency decreases with body length (∝length-0.53) while cruising speed remains roughly invariant (∝length0.08) at 2 m s-1 We compared these measured results for oscillatory frequency against simplified models of an oscillating cantilever beam (∝length-1) and an optimized oscillating Strouhal vortex generator (∝length-1). The difference between our length-scaling exponent and the simplified models suggests that animals are often swimming non-optimally in order to feed or perform other routine behaviors. Cruising speed aligned more closely with an estimate of the optimal speed required to minimize the energetic cost of swimming (∝length0.07). Our results are among the first to elucidate the relationships between both oscillatory frequency and cruising speed and body size for free-swimming animals at the largest scale.

Sexual behaviour and morphological variation in the millipede Megaphyllum bosniense (Verhoeff, 1897)

Sexual selection can be a major driving force that favours morphological evolution at the intraspecific level. According to the sexual selection theory, morphological variation may accompany non-random mating or fertilization. Here both variation of linear measurements and variation in the shape of certain structures can significantly influence mate choice in different organisms. In the present work, we quantified sexual behaviour of the millipede Megaphyllum bosniense (Verhoeff, 1897) as characterized by several sequences. These are: mating latency, duration of copulation, contact to copulation time, duration of contact without copulation, time from entrance (time-point when individuals were placed in boxes in which tests occurred) to contact with copulation, and time from entrance to contact without copulation. Further, we analysed the influence of morphological variation (both variation of linear measurements and variation in the shape of several structures) on mating success. Variation of body length, antennal length, length of the walking legs, trunk width, and trunk height was analysed by traditional morphometrics, while variation in size and shape of the antennae, walking legs, head, and gonopods (promeres, opisthomeres) was analysed using geometric morphometrics. More than half of all physical contacts detected among the millipedes resulted in copulation. Based on the value of sexual selection coefficients, preferences toward the previous partner were found to be prevalent in both female and male choice tests. Individuals with different mating status significantly differed in some morphological traits (body mass, head centroid size, head shape, and promere shape). Our study yielded new information about the sexual behaviour of millipedes and variation of morphological traits as a potential basis for mate preferences.

Heritability of body size in the polar bears of Western Hudson Bay.

Among polar bears (Ursus maritimus), fitness is dependent on body size through males' abilities to win mates, females' abilities to provide for their young and all bears' abilities to survive increasingly longer fasting periods caused by climate change. In the Western Hudson Bay subpopulation (near Churchill, Manitoba, Canada), polar bears have declined in body size and condition, but nothing is known about the genetic underpinnings of body size variation, which may be subject to natural selection. Here, we combine a 4449-individual pedigree and an array of 5,433 single nucleotide polymorphisms (SNPs) to provide the first quantitative genetic study of polar bears. We used animal models to estimate heritability (h2 ) among polar bears handled between 1966 and 2011, obtaining h2 estimates of 0.34-0.48 for strictly skeletal traits and 0.18 for axillary girth (which is also dependent on fatness). We genotyped 859 individuals with the SNP array to test for marker-trait association and combined p-values over genetic pathways using gene-set analysis. Variation in all traits appeared to be polygenic, but we detected one region of moderately large effect size in body length near a putative noncoding RNA in an unannotated region of the genome. Gene-set analysis suggested that variation in body length was associated with genes in the regulatory cascade of cyclin expression, which has previously been associated with body size in mice. A greater understanding of the genetic architecture of body size variation will be valuable in understanding the potential for adaptation in polar bear populations challenged by climate change.

Environmental calcium and variation in yolk sac size influence swimming performance in larval lake sturgeon (Acipenser fulvescens).

In many animal species, performance in the early life stages strongly affects recruitment to the adult population; however, factors that influence early life history stages are often the least understood. This is particularly relevant for lake sturgeon, Acipenser fulvescens, living in areas where environmental calcium concentrations are declining, partly due to anthropogenic activity. As calcium is important for muscle contraction and fatigue resistance, declining calcium levels could constrain swimming performance. Similarly, swimming performance could be influenced by variation in yolk sac volume, because the yolk sac is likely to affect drag forces during swimming. Testing swimming performance of larval A. fulvescens reared in four different calcium treatments spanning the range of 4-132 mg l-1 [Ca2+], this study found no treatment effects on the sprint swimming speed. A novel test of volitional swimming performance, however, revealed reduced swimming performance in the low calcium environment. Specifically, volitionally swimming larvae covered a shorter distance before swimming cessation in the low calcium environment compared with the other treatments. Moreover, sprint swimming speed in larvae with a large yolk sac was significantly slower than in larvae with a small yolk sac, regardless of body length variation. Thus, elevated maternal allocation (i.e. more yolk) was associated with reduced swimming performance. Data suggest that larvae in low calcium environments or with a large yolk sac exhibit reduced swimming performance and could be more susceptible to predation or premature downstream drift. Our study reveals how environmental factors and phenotypic variation influence locomotor performance in a larval fish.

Two new species of the genus Laena Dejean (Coleoptera: Tenebrionidae: Lagriinae) from Hong Kong.

Two new species of the genus Laena Dejean, 1821 (Coleoptera: Tenebrionidae: Lagriinae) are described from Hong Kong: Laena hongkongica sp. n. and Laena walkeri sp. n. These constitute the first record of the genus from Hong Kong, as a species previously described from nearby area Laena ovipennis Schuster, 1926, in fact originated from Zhejiang province nearby Shanghai. Both species from Hong Kong possess a wide variation in body length, which is quite unusual for this genus.

Development of the Forensically Important Beetle Creophilus maxillosus (Coleoptera: Staphylinidae) at Constant Temperatures.

Creophilus maxillosus (L., 1758) is a common and widely distributed beetle species found on corpses, and its development duration is far longer than species belonging to the genus Calliphoridae and Sarcophagidae. Therefore, C. maxillosus can be used as a supplementary indicator to estimate minimum postmortem interval (PMImin), and could greatly extend the range of PMImin when the primary colonizers are no longer associated with the corpse or have emerged from pupae. Better descriptions of C. maxillosus development are needed to apply this species for forensic investigations. In this study, the development of C. maxillosus at seven constant temperatures ranging from 17.5-32.5 °C was studied. Through regression analyses, the simulation equations of larval body length variation with time after hatching were obtained. Isomegalen diagrams of the changes of larval body length over time at specific temperatures, and the isomorphen diagrams on the duration of different developmental milestones at specific temperatures were generated. In addition, thermal summation models of different developmental stages and the overall development process of C. maxillosus were generated through regression analysis, by estimating the development threshold temperatures (D0) and the thermal summation constants (K). These results provide important tools for forensic investigations to generate a long-range of PMImin estimation based on the development of C. maxillosus.

Expression of Hox paralog group 13 genes in adult and developing Megalobrama amblycephala

Hox genes encode transcription factors that play a key role in specifying the body plan in most metazoans. HoxPG13 genes most probably played an important role in body length variation during the evolution of animals. This is the first report of the mRNA expression patterns of the entire Hox paralog group 13 (HoxA13a, HoxA13b, HoxB13a, HoxC13a, HoxC13b, HoxD13a) in fish. Expression was studied by qPCR in five tissues of adult Megalobrama amblycephala specimens (spleen, liver, kidney, intestine and gills) and during development (17 stages: fertilised egg to 90 days-old juveniles). Expression in tissues (for all six genes) was generally very low in gills (0.0006–0.05), spleen (0.006–0.09) and kidney (0.02–0.39); the highest in intestine (from 2.28 for HoxC13b to 244.29 for HoxC13a). During the development, a peak in expression around the hatching was observed for all six genes. Results suggest a high maternal expression of HoxA13a, and low for HoxA13ab. HoxD13a paralog exhibited the lowest expression: 0.0006–2.63 in tissues and 0.0005–1.7 during development, suggesting the possibility of a gradual loss of functionality. Expression of HoxC13 paralogs corroborates the findings in zebrafish: HoxC13b is maternally expressed and more important during the development. In adults, it was the opposite: expression was low for HoxC13b and very variable for HoxC13a (0.06–244.29). Differences in expression levels between both pairs of paralogs (Aa/Ab and Ca/Cb) indicate the possibility of the existence of some redundancy afforded by maintaining both paralogs.