Maximum Body Length Research Articles

Warmer temperature decreases the maximum length of six species of marine fishes, crustacean, and squid in New Zealand

As global oceans continue to warm and deoxygenate, it is expected that marine ectotherms will reduce in body size resulting from the interactive effects of temperature and dissolved oxygen availability. A temperature-size response describes how wild populations of ectothermic species grow faster and reach a smaller size within warmer temperatures. While temperature-size responses are well observed in marine ectotherms, the mechanisms underpinning such a reduction in body size remain debated. Here, we analyse the relative influence of temperature, dissolved oxygen concentration, and geographic location (which encompasses multiple latent variables), on the maximum body length of four fish, one crustacean, and one squid species, which inhabit shallow to deep sea (1000 m) New Zealand waters across a temperature gradient of 1.5 to 18 °C. We found that all study species displayed a temperature-size response, with the strongest response exhibited by the largest species, hoki (Macruronus novaezelandiae). We also found that temperature was more important than dissolved oxygen concentration in determining maximum body length, as dissolved oxygen levels were at or near saturation in the study area. Our results suggest that larger-bodied species may experience the strongest temperature-size responses, and support expectations from the gill-oxygen limitation theory (GOLT) and the oxygen and capacity limited thermal tolerance (OCLTT) concept that increases in oxygen demand may be size- and temperature-dependent, thus driving a reduction in maximum body length of marine ectotherms with warming.

New scale type from a small-bodied hadrosaur in the Frenchman Formation of southern Saskatchewan: Potential implications for integumentary diversity in Edmontosaurus annectens

Among non-avian dinosaurs, fossilized skin is most comprehensively represented in the hadrosaurids. Here we provide the first full descriptions of hadrosaurid skin from the Upper Cretaceous (Maastrichtian) Frenchman Formation in southern Saskatchewan. Based on the geological age and associated skeletal material, the specimen is tentatively identified as Edmontosaurus annectens. The fossil record of skin from E. annectens is one of the best represented of any non-avian dinosaur, and the scale structure and patterning have been previously described across nearly the entire body. However, the current specimen, which likely derives from the pelvic region, possesses unique corrugated scales that have not been observed in this species before. Additionally, although its body length is estimated to be approximately 75% of larger, presumably fully-grown individuals, histological evidence suggests that this specimen was somatically mature. This unique specimen expands the morphological diversity of scales observed in E. annectens, demonstrating a higher level of intraspecific variation in hadrosaurid skin than previously recognized. Additionally, this specimen also suggests that there is variability in the maximum body length reached by some adult E. annectens. Although the exact cause of the variation in adult size and scale morphology is yet to be understood, it highlights the potential intraspecific diversity not observable based on skeletal morphology alone. The unique scale morphology seen in this specimen also has potentially important implications for the taxonomic utility of hadrosaurid skin.

Historical connectivity and environmental filtering jointly determine the freshwater fish assemblages on Taiwan and Hainan Islands of China.

The biotas of Taiwan and Hainan Islands are of continental origin, but the manner with which historical and ecological factors shaped these insular species is still unclear. Here, we used freshwater fish as a model to fill this gap by quantifying the phylogenetic structure of the insular faunas and disentangling the relative contribution of potential drivers. Firstly, we used clustering and ordination analyses to identify regional species pools. To test whether the insular freshwater fish faunas were phylogenetically clustered or overdispersed, we calculated the net relatedness index (NRI) and the nearest taxon index (NTI). Finally, we implemented logistic regressions to disentangle the relative importance of species attributes (i.e., maximum body length, climatic niche dissimilarity [ND], and diversification) and historical connectivity (HC) in explaining the insular faunas. Our results showed that the most possible species pools of Taiwan are Zhejiang and Fujian provinces, and those of Hainan are Guangdong and Guangxi provinces. These insular faunas showed random phylogenetic structures in terms of NRI values. According to the NTI values, however, the Taiwanese fauna displayed more phylogenetic clustering, while the Hainanese one was more overdispersed. Both the standard and phylogenetic logistic regressions identified HC and climatic ND as the 2 top explanatory variables for species assemblages on these islands. Our reconstruction of the paleo-connected drainage basins provides insight into how historical processes and ecological factors interact to shape the freshwater fish fauna of the East Asian islands.

Evaluation of the combined effect of elevated temperature and cadmium toxicity on Daphnia magna using a simplified DEBtox model

Thermal discharge and heatwaves under climate change may increase water temperature. In this study, the individual and combined effect of elevated temperature and cadmium (Cd) toxicity on somatic growth and reproduction of Daphnia magna was evaluated using a simplified dynamic energy budget model (DEBtox). The model predicted that the maximum body length (Lm) would be shorter (3.705 mm) at an elevated temperature of 25 °C than at 20 °C (3.974 mm), whereas the maximum reproduction rate (R˙m) would be higher at 25 °C (5.735) than at 20 °C (5.591). The somatic growth and reproduction of D. magna were significantly (p < 0.05) reduced with increasing Cd concentrations, and the reduction was greater at 25 than at 20 °C. Potentiation of Cd toxicity by elevated temperature was correctly simulated by assuming four toxicological modes of action influencing assimilation, somatic maintenance and growth, and reproduction. Overall, the population growth rate of D. magna was expected to decrease linearly with increasing Cd concentrations, and the decrease was expected to be higher at 25 than at 20 °C. These findings suggest a significant ecological risk of toxic metals at elevated temperature, with a mechanistic interpretation of the potentiation effect using a DEBtox modeling approach.

A new species of Pterodrilus (Branchiobdellida: Clitellata) from the upper Yadkin-Pee Dee River Basin of North Carolina

ABSTRACT A new species of branchiobdellidan, Pterodrilus leiteri n. sp., is described from the anterior cephalothorax of the crayfish Cambarus longulus from north-western North Carolina, USA. Like its 10 congener species, P. leiteri n. sp. is diminutive, with a maximum body length < 1 mm. It can be distinguished from other members of Pterodrilus by the number and position of dorsal ridges and projections. Unique to this species are three pairs of twinned dorsal unbranched digitiform projections on segments 3, 4, and 5. Our discovery adds to our understanding of diversity within an unusual and poorly understood genus, Pterodrilus, and more generally, branchiobdellidan fauna in the southeastern USA.

Length‐weight relationships of 6 fish species caught in a Mediterranean lake (Trichonis‐NW Greece)

In the present study the length–weight relationships (LWRs) of 6 fish species which are endemic to Western Greece, caught in the natural Lake Trichonis by experimental gillnets and electrofishing were estimated. Benthic (mesh size 5–55 mm; height 1.5 m; length 30 m) and pelagic (mesh size 6.25–55 mm; height 6 m; length 27.5 m) Nordic type multimesh gillnets were used seasonally, between February 2019 and November 2019, at different depth zones (0-57m). Electrofishing (80 Hz) conducted in the littoral zone of the lake during four samplings (2018, 2019). All the estimated LWRs were highly significant (p < .05) with high correlation coefficient (r2 ≥ 0.962). The estimated b values ranged from 3.058 to 3.344. For five of the studied species (Trichonis spined loach (Cobitis trichonica Stephanidis 1974), Trichonis blenny (Salaria economidisi Kottelat 2004), Trichonis rudd (Scardinius acarnanicus Economidis 1991), Acheloos roach (Leucos panosi (Bogutskaya & Iliadou 2006)) , Hellenic minnowroach (Tropidophoxinellus hellenicus (Stephanidis 1971)) new maximum total body lengths (TL) were recorded, while for two species (T. hellenicus and L. panosi) LWRs are presented for the first time.

Evaluating the size at sexual maturity for 20 fish species (Actinopterygii) in wetland (Gajner Beel) ecosystem, north-western Bangladesh through multi-model approach: A key for sound management

Effective fisheries management depend on having an exact assessment of biological parameters, including growth parameters, reproduction, size at sexual maturity (Lm), and stock assessment. The purpose of this research was to estimate the size at sexual maturity (Lm) for 20 fish species belongs to 14 families from a wetland (Gajner Beel) ecosystem in the north-western (NW) Bangladesh through multi-models such as length (Lmax) based empirical model, gonadosomatic index (GSI)-based model, and logistic model using commercial catches from January to December 2018. Also, we assessed the Lm in other water-bodies worldwide. Specimens’ total length (TL) was noted up to 0.1 cm using measuring board body weight (BW) and gonad weight (GW) weighed by digital electronic balance with 0.01 g accuracy. To assess the Lm, maximum body length (Lmax) based empirical model; the relation between TL (total length in cm) vs. GSI (gonadosomatic index in %); and a logistic model were considered. The minimum Lm was 4.64, 3.90, and 4.15 cm for Chanda nama Hamilton, 1822 and the maximum was 25.33, 24.50, and 24.70 cm for Channa striata (Bloch, 1793) through Lmax, GSI, and logistic-based models, respectively. From these three models, the minimum mean Lm was 4.23 cm for C. nama and the maximum was 24.84 cm for C. striata. The Lm with 50.0% species was in 8.80 cm TL. We also calculated the Lm from different bodies of water based on Lmax. This study was generated data of 17 new Lm among 20 species, which are globally absent. Therefore, the study will help develop sustainable management strategies, conservation through the implementation of mesh size based on the size at sexual maturity (Lm).

Spawning substrate shift associated with the evolution of a female sexual characteristic in a family of fishes

Abstract Because ‘primary’ sexual characteristics (i.e. those directly associated with reproduction) can be extremely variable, evolve quickly, and can be impacted by both natural and sexual selection, they are often considered excellent model systems in which to study evolution. Here, we explore the evolution of the anal sheath, a trait hypothesized to facilitate the release and proper placement of eggs on the spawning substrate, and its relationship to spawning habitat and maximum body size in a family of fish (Fundulidae). In addition to using phylogenetically informed statistics to determine the role of preferred spawning habitat and maximum body size on the evolution of anal sheath length, we reconstruct the evolutionary history of the anal sheath and preferred spawning habitat. We then test for significant phylogenetic signal and evolutionary rate shifts in the size of the anal sheath and the preferred spawning habitat. Our results indicate that preferred spawning habitat, and not maximum body length, significantly influences anal sheath size, which is associated with a significant phylogenetic signal, and an evolutionary rate similar to that of preferred spawning substrate. We discuss these results in terms of potential evolutionary mechanisms driving anal sheath length.

Life History of Mediterranean Horse Mackerel Trachurus mediterraneus (Carangidae) from Crimea (Black Sea)

The sex ratio, body length–age structure, growth rate, maturity dynamics, and mortality are studied in Mediterranean horse mackerel Trachurus mediterraneus from the shelf zone of Crimea. The sex ratio is close to 1 : 1, the maximum body length of the females and males is 22.5 and 20.8 cm, respectively, and the maximum age of the representatives of both sexes is 6 years. The sexual dimorphism in the growth rate is not revealed. The von Bertalanffy growth equation parameters for both sexes are as follows: asymptotic length and weight 19.0 cm and 57.4 g and growth coefficient 0.44 year–1. The females (50%) reach sexual maturity by 10.72 cm, and the males reach maturity by 10.53 cm at the age 1+. The spawning is observed from June to September. The maximum values of gonadosomatic indeces of the males (2.37%) and females (3.84%) are registered in June, and July, respectively. The coefficients of the total, natural, and fishing mortality are 1.41, 0.89, and 0.52 year–1. Within the entire range, the strong positive relationships between maximum body length, linear growth rate index and mean annual surface water temperature are registered. The difference in horse mackerel growth rate between various regions of the Black Sea is small. Nevertheless, the growth rate and maximum body length of the Black Sea individuals are smaller than these parameters in the Mediterranean Sea that is connected with the adaptation of the Black Sea population to climate seasonality.

Максимальная масса тайменя сибирского Hucho taimen (Pallas) в ареале

In most western regions, Siberian taimen has become a rarity in its range. At present, only a few refugiums of the Siberian and Far Eastern rivers still have groups of Siberian taimen, where fish of the maximum size are recorded. In the east of its range, the rivers that flow into the southern part of the Sea of Okhotsk: The Amur, Uda and Tugur, are the few areas where the Siberian taimen groups are still preserved in good condition in uninhabited places. On the example of p. Tugur (Tuguro-Chumikansky district of the Khabarovsk Territory, Sea of Okhotsk), where there are no roads and a small population, the authors studied the local grouping of Siberian taimen, where individuals of maximum size are still not uncommon. The remaining areas of the range are considered according to scientific publications. Fish of the maximum size are very rare, which is logical: the number of extreme values of the size-age range is minimal. In 2007-2018, in the Tugur River, individuals aged 6-10 years were the maximum (27.6%), and 31-35 years – the minimum (0.9%) of the age range. The archives of the sport fishing base in the Tugur River basin for 2008-2020 showed that the maximum body length of the Siberian taimen was 165 cm, and the maximum body weight was 51.12 kg. Neither in the era of black-and-white photography, nor in the era of video, there is no documentary evidence of the Siberian taimen with a body length of more than 170 cm.

The Size–Age Structure, Growth, and Maturation of the Spotted Catfish Arius maculatus (Thunberg, 1792) (Siluriformes: Ariidae) from the Mekong Delta, Vietnam

The size–age structure, growth, and maturation of the spotted catfish Arius maculatus (Thunberg, 1792) from the Hau River estuary, Mekong Delta, Vietnam, were studied for the first time. A total of 460 fish specimens collected from January to March 2019 were examined. The annuli on the otoliths were visualized; their formation may be related with the alternation of the dry and rainy seasons. The male to female ratio in the catches was 1 : 1.81. The proportion of males decreased in the older age groups. The maximum total body length of the females was 21.9 cm; for the males, it was 23.7 cm. The maximum recorded age of females in catches was 7+; for males it was 8+. No inter-gender differences in growth were detected. The parameters of the von Bertalanffy equation for both sexes according to empirical data were as follows: L∞ = 28.3 cm; k = 0.15/yr; t0 = –1.03 yr; growth performance index, φ = 2.08. The coefficients of the relationship between mass and length were as follows: a = 0.0054; b = 3.22. Maturation began at a body length of 13 cm at an age of 3 yr and ended at a body length of 18 cm at an age of 6 yr; 50% of the individuals became mature at a body length of 15 cm at an age of 4 yr. No inter-gender differences in the timing of maturation were found. A. maculatus from the Mekong Delta is characterized by a low growth rate compared to other populations, which may be associated with the labile habitat conditions in the estuary zone.

State of aggregations and biological characteristics for mysid Neomysis awatschensis in the northern Amur Bay (Peter the Great Bay, Japan Sea)

Size and sex structure of estuarine-freshwater mysid Neomysis awatschensis in the northern Amur Bay is considered, time of their aggregations formation is determined, and their biomass is estimated on the data of surveys conducted in 2014–2019. The samples were collected at the depth of 0.5–2.0 m in the daytime in May-July. The catches were recalculated per 1 m3 of water. All collected mysids (2212 ind.) were measured under binocular microscope with accuracy of 0.1 mm, weighted by torsion scales with accuracy of 1 mg, and separated to males, females and juveniles. The females were differentiated by 5 stages of their development: 1) immature females with oostegetic rudiments; 2) oviparous females; 3) females with embryos in the marsupia bags without stalk-eyes with black pigment; 4) females with embryos in marsupia bags with black eyes; 5) spawned females with empty marsupii. Time and duration of N. awatschensis aggregating changed by years in dependence on hydrological and weather conditions; the aggregations were either monospecific or mixed with another mysid species — N. mirabilis. The maximum mysid biomass could exceed 500 g/m3 that was appropriate for commercial fishery. The maximum body length of mysid females was 13.7 mm, of males — 12.0 mm. The average length varied from 6.7 to 10.3 mm, being shorter in summer months than in May. Portion of males in the aggregations was always significant (16.3–50.7 %), portion of females varied from 8.7 to 52.5 %, portion of juveniles was the largest in June (29.9–75.0 %). The females to males ratio was 1 : 1 in May and July of 2014–2017, but males prevailed in June 2015 (1.0 : 1.9), whereas females prevailed in June 2016 (1.8 : 1.0). Spawning of the mysids was the most intensive in May-June, though females had embryos at different stages of development in all samples that indicated an extended period of reproduction.

Identification of Freshwater Zooplankton Functional Groups Based on the Functional Traits of Species

Information on the functional traits of the most widespread species of freshwater zooplankton (Rotifera, Cladocera, and Copepoda) in European Russia was collected and analyzed. Our database includes 355 species described by 4 traits, namely: maximum body length, trophic group, feeding type, and movement type. Cluster analysis based on Gower's functional distances shows that freshwater zooplankton can be classified into 19 groups with different ecological roles. The characteristics of each identified functional group are presented. We believe it to be fundamentally important to build a unified classification using all available data and applicable characters for all three main taxonomic groups of zooplankton. Comparison with the existing ecological zooplankton classification proposed by Yu. S. Chuikov has demonstrated a number of advantages of our approach. Several ecological groups in Yu. S. Chuikov’s classification are represented by more fractional categories in our classification. Our system of functional groups can be used in studies of the structure of zooplanktocoenoses based on direct cluster analysis and ordination or based on functional distances between samples. To calculate the functional similarity between species, one can use our database of features, which is contained in the Appendix. Analysis based on functional groups gives a better unerstanding of the structure of a community than traditional ordination, which takes into account only the taxonomic affiliation of species. The approach used for functional group identification can be useful in assessing functional diversity and identifying patterns of freshwater zooplanktocoenoses dynamics. The database of functional signs of zooplankton can be used to check the relationship of functional signs with environmental factors.

The demersal bathyal fish assemblage of the Central-Western Mediterranean: Depth distribution, sexual maturation and reproduction

This study compiles information on the size distribution and reproductive patterns of five chondrichthyans and 10 bony species dwelling on the continental slope of the Central-Western Mediterranean (south-eastern Sardinian waters, depth 720–1890 m). The abundance of the relatively less numerous chondrichthyans was found to decrease with depth. Almost all chondrichthyan species had a long reproductive period throughout the year at all depths. In bony fishes, the upper bathymetric stratum (<1100 m) was dominated by species with continuous and seasonal (autumn-winter) spawning cycles. At intermediate and lower depths (>1100 m), continuous reproduction was the most common pattern. Both chondrichthyans and bony fishes exhibited large sizes at maturity and at first maturity (>75% and >60% of their maximum body length, respectively), supporting the hypothesis that most deep-sea fish populations are characterized by a delayed maturity, which makes them highly vulnerable to fishing pressure and over-exploitation. In some sharks, population partitioning was observed, according to life stage as a function of depth: adult/mature females occupied deeper habitats than males and juveniles. Conversely, Dipturus nidarosiensis female and male juveniles (>1100 m) were segregated from the adult/mature population, dwelling between 1000 and 1100 m. In four of the 10 bony fishes examined, we found a clear and significant predominance of females, particularly pronounced in Alepocephalus rostratus, which is clearly related to their K-reproductive strategy. The four key-selected species (Galeus melastomus, A. rostratus, Bathypterois mediterraneus and Trachyrincus scabrus), characterized by different reproductive strategies/modalities and feeding behaviours, were differently affected by depth and fluxes of organic matter (Particulate Organic Carbon concentration) from the photic zone towards the sea-bottom as a function of sex and life -stage.

Determinants of establishment success: Comparing alien and native freshwater fishes in Taiwan.

Many parts of Asia, including Taiwan, have suffered severely from freshwater fish invasions. However, few studies using an assemblage approach have been conducted in the region so far that would help to prioritize suitable preventive actions. In this study, we focused on the invasion process from the import stage to the establishment stage, and defined establishment success as the success during this predefined process. We used datasets of freshwater fish assemblages in Taiwan to (1) compare established versus non-established alien species to distinguish the determinants of establishment success, and (2) to use these determinants to test a life history hypothesis which predicts that the magnitudes of the determinants should be significantly different between established alien species and native species. We collated a dataset for freshwater fish species which were imported into Taiwan (n = 118) of which some successfully established (n = 26), and another dataset for freshwater fish species native to Taiwan (n = 77). For each imported species, we collected data for 17 variables, including two phylogenetic, two human-use, two invasion history, and 11 life history variables. We then used decision tree methods, which have advantages in analyzing datasets with many variables of mixed types without the need to make assumptions about data distributions and input data for missing values. Our results showed that aquaculture use and maximum body length were the most important determinants for predicting establishment success of alien freshwater fish in Taiwan. Comparing five important determinants between established alien versus native species showed that the established alien species were significantly more often used in aquaculture, were associated with a higher number of established countries, and had a larger body length and greater highest water temperature tolerance than the native species. We thus conclude that our results provided evidence to support our stated hypothesis. We suggest that aquaculture use, measures of body size, and the number of previously invaded countries may alert researchers and conservation managers to species with a high establishment potential, especially for countries with similar conditions as those in Taiwan.

Ontogeny of the trilobite Elrathia kingii (Meek) and comparison of growth rates between Elrathia kingii and Aulacopleura koninckii (Barrande)

AbstractTrilobites offer almost unparalleled insight into the growth and development of fossil ecdysozoans. Here I use newly collected material of Elrathia kingii (Meek) to estimate growth rates and describe shape change over the ontogeny of E. kingii. Well‐preserved, articulated specimens from all post‐embryonic stages were collected from a 1.5 m interval of the upper Wheeler Formation (Miaolingian Series, Cambrian) in western Utah (USA), and size and landmark‐based shape data were digitized from photographs. Growth rates were estimated and compared with previously published data on the Silurian trilobite, Aulacopleura koninckii (Barrande). Like A. koninckii, the cephalic growth rate in E. kingii was constant and of similar magnitude to the minimum growth rate along the trunk, and growth rates in the trunk were lower during the holaspid (‘adult’) period than during the meraspid (‘juvenile’) period. However, body length at the onset of meraspis was smaller, the growth gradient along the trunk during meraspis was shallower, and the terminal number of thoracic tergites was smaller in E. kingii than in A. koninckii. Despite these differences, these two species had similar maximum body lengths, because higher overall growth rates in E. kingii compensated for other differences. The rate of cephalic shape change in E. kingii decreased at the transition from meraspis to holaspis, while the pygidium became more morphologically distinct from the thorax during holaspis. I also provide an emended diagnosis for E. kingii, descriptions of the ontogeny and ventral morphology, and evidence that E. kingii holaspids had an invariant number of tergites.

Short Communication: The lifecycle of Neocaridina denticulata and N. palmata in aquariums

Abstract. Mahmoud HHA, Sastranegara MH, Kusmintarsih ES. 2020. Short Communication: The lifecycle of Neocaridina denticulata and N. palmata in aquariums. Biodiversitas 21: 2396-2402. The study on the life cycle of Neocaridina spp. is important because it plays a major role in the economy and trade between countries. However, there is a lack of sufficient studies on this particular topic. One of the factors that influence Neocaridina spp. life production is its life cycle and the associated water parameters. The objectives of this study were to conduct, observe, and record the life cycle of Neocaridina denticulata and N. palmata and the associated with water parameters (temperature, pH, ammonia, nitrite, and oxygen) in the aquarium. The results showed that there was no difference in the life cycle stages between the two shrimp species. Both species reached the first sexual maturity stage of the life cycle at 75 days, with the maximum body length of the mature shrimp ranging from 2.30-3.00 cm. The eggs became larvae in 15 days, larvae reached the juvenile stage after 60 days, and the juvenile became mature in 15 days. The number of eggs was influenced by the body size of the female shrimps; smaller females produced fewer eggs. Optimal water quality varies by species and must be monitored to ensure growth and survival. The temperature range in this study was 25-28°C and the pH was 6.5-8.0. The ammonia level was in the range between 1.21 and1.72 mg/L, the nitrate was between 0.06 and 7.91 mg/L, and the oxygen was around 5.5-7.9 mg/L. All of the water quality parameters in this study are within the acceptable range for Neocardina cultivation.

Climate change and spatial distribution shaped the life-history traits of schizothoracine fishes on the Tibetan Plateau and its adjacent areas

Understanding the mechanisms by which the environment shapes the life history of fishes is critical for our ability to predict the responses of species or ecosystems under global environmental change. Although many studies focused on the intraspecific level have been conducted in several regions, rare or threatened fish fauna have been poorly studied because of the inability to obtain sufficient samples for multiple populations; as such, regions such as Asia remain underrepresented in global studies. Here, we explore the role of environmental drivers in shaping the life-history traits of endemic schizothoracine fishes at the interspecific level in the Tibetan Plateau and its adjacent areas. Eight life-history traits of 25 species of schizothoracine fishes and 17 environmental variables, including climatic, spatial and anthropogenic factors, were analysed in our study. Our analysis showed that maximum body length, lifespan, age and size at maturity and egg size were significantly explained by climatic and spatial variables. The key environmental factors for body length and lifespan were precipitation seasonality and annual precipitation for age at maturity. Temperature isothermality was the dominant factor for size at maturity and egg size, and latitude was the principal explanatory variable for egg size as well. Our findings provide empirical evidence that this endemic fauna is highly sensitive to environmental change, especially climate change. The effects of climate change, which are neglected in current conservation efforts, must be incorporated into systematic conservation plans for the Tibetan Plateau and its adjacent areas. Broad-scale interdisciplinary scientific studies should be developed as the first priority to fully clarify the ecological adaptation that has occurred. This study also highlighted that characterizing the role of the environment in determining life-history traits at the interspecific level for rare or threatened fauna is feasible when global environmental change concerns are addressed.

Selecting optimal bin size to account for growth variability in Electronic LEngth Frequency ANalysis (ELEFAN)

Electronic LEngth Frequency ANalysis (ELEFAN) is a widely used method to fit von-Bertalanffy Growth Function (VBGF) using length frequency data for data-poor fisheries. However accuracy of this method depends on diverse assumptions, among which the variability of individual growth may be particularly influential. In addition, the selection of class interval of length frequency data, defined as bin size, is also considerable source of uncertainty. However, rare guidance exists on how to account for the growth variability and to select bin size. In this study, we considered the effects of growth variability and bin size together by testing whether appropriate bin size can reduce estimating bias due to growth variability. We used a Monte Carlo simulation framework to evaluate the performances of ELEFAN under scenarios of different bin size and levels of individual growth variability for 10 fish species. The results indicated that growth variability might result in large variations and biased estimation of growth parameters if the bin size was chosen arbitrarily. On the contrary, there was an optimal bin size for each species, which led to unbiased estimates even in a substantially high level of growth variability. Summarizing the optimal bin sizes of the 10 species, we proposed a rule of thumb to select optimal bin size (OBS) for the future applications of ELEFAN according to the maximum body length (OBS=0.23×Lmax0.6) and age (OBS=1.86×(Lmax/A)0.45) of fish species. The improvement of accuracy of VBGF parameter estimation will help to understand the growth characteristics and reduce the uncertainty for data-limited stock assessment methods.

Microanatomy and growth of the mesosaurs &amp;lt;i&amp;gt;Stereosternum tumidum&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Brazilosaurus sanpauloensis&amp;lt;/i&amp;gt; (Reptilia, Parareptilia)

Abstract. Histology and microanatomy of vertebrae, ribs, haemal arch, and humeri and femora of 10 individuals of Stereosternum and two dorsal ribs of 1 individual of Brazilosaurus were studied. All individuals had achieved a body length of 50 cm (equal to 65 % of the maximum known body length) or larger. All sampled bones are highly osteosclerotic due to the reduction of medullary cavities and the filling of medullary regions by endosteal bone. Calcified cartilage occurs – if at all – only locally in small clusters in the medullary regions of midshaft and in higher amounts only in non-midshaft sections of long bones and towards the medio-distal rib shaft, respectively. The primary bone tissue consists of highly organized parallel-fibred tissue and/or lamellar tissue, which is in most samples relatively lightly vascularized or even avascular. If present, vascular canals are mainly longitudinally oriented; some show a radial orientation. Simple vascular canals as well as primary osteons occur. Some of the latter are secondarily altered, i.e. widened. Remodelling of the periosteal cortex is only documented by few scattered erosion cavities and secondary osteons. The tissue is regularly stratified by lines of arrested growth (LAGs), which usually appear as double or multiple rest lines, indicating strong dependence on exogenous and endogenous factors. Because of the inhibition of periosteal remodelling the growth record is complete and no inner cycles are lost. Individuals of Stereosternum show a poor correlation of body size and number of growth marks, which might be the result of developmental plasticity. Brazilosaurus shows a highly organized, avascular lamellar tissue and a high number of regularly deposited rest lines throughout the cortex of the ribs. The medullary region in the ribs of Brazilosaurus is distinctly larger when compared to ribs of Stereosternum. However, strong osteosclerosis is obvious in both taxa, pointing to a high degree of aquatic adaption. Ribs of Stereosternum, Brazilosaurus, and Mesosaurus are clearly distinguishable from each other by the distribution of the periosteal and endosteal territory. Furthermore, Brazilosaurus differs in its growth pattern (i.e. spacing of rest lines) when compared to Stereosternum and Mesosaurus.