Juvenile Specimens Research Articles

Gill structure and neurochemical markers in the African bonytongue (Heterotis niloticus): A preliminary study

We have conducted a morphological and immunohistochemical study of the gills of juvenile specimens of the obligate air-breathing fish Heterotis niloticus. The study has been performed under normoxic and hypoxic conditions. The gills showed a reduced respiratory surface area by development of an interlamellar cellular mass (ILCM). The ILCM persisted without changes under both normoxia and hypoxia. Neuroepithelial cells (NECs), the major oxygen and hypoxia sensing cell type, were located in the distal end of the gill filaments and along the ILCM edges. These cells expressed 5HT, the neuronal isoform of the nitric oxide synthase (nNOS) and the vesicular acetylcholine transporter (VAChT). Furthermore, NECs appeared associated with nitrergic nerve fibres. The O2 levels did not modify the location, number or the immunohistochemical characteristics of NECs. Pavement cells covering the ILCM were also positive to nNOS and VAChT. The mechanisms of O2 sensing in the gills of Heterotis appears to involve several cell populations, the release of multiple neurotransmitters and a diversity of excitatory, inhibitory and modulatory mechanisms.

Influence of seasonality on hematological parameters of farmed streaked prochilod (Prochilodus lineatus)

The objective of the present study was to evaluate the influence of seasonality on the hematological aspects of juvenile farmed Prochilodus lineatus, to highlight the changes caused by seasonal variations and to develop reference intervals appropriate for each season. The study of the hematological parameters of farmed species has showed the mechanisms of adaptation to environmental variations, both in the natural environment and in production systems, allowing discernment of the differences between physiological and pathological reactions. Among the environmental factors, temperature and day length are recognized as a key factor in promoting changes in fish physiology, which can be reflected in hematological parameters. The present study analyzed the hematological parameters of juveniles of farmed streaked prochilod (Prochilodus lineatus) considering seasonal features such as temperature and day length, to highlight the changes caused by seasonality and the mechanisms involved in adaptation, and thus, elaborate reference intervals for each season. We found that seasonality has a significant impact on the hematological parameters of juvenile specimens of farmed streaked prochilod (Prochilodus lineatus), as it promotes changes in hematimetry, hemoglobinometry, white blood cells count and in the prevalence of leukocyte types. These findings demonstrate the importance of establishing reference intervals for farmed species, considering the factors responsible for physiological modifications, especially seasonal features.

Cranial osteology of a juvenile specimen of Acratocnus ye (Mammalia, Xenarthra, Folivora) and its ontogenetic and phylogenetic implications.

The present study comprises a description of the skull and jaw anatomy of a juvenile specimen of the Antillean sloth Acratocnus ye, from the Holocene of Haiti. Detailed descriptions and illustrations are provided of the skull bones and their sutural connections, which normally fuse in adults. Descriptions are also provided for the mandible and ear ossicles, as well as endocranial surfaces and sinuses exposed by breaks. The anatomy of our juvenile A. ye is compared to that of adult A. ye to assess ontogenetic changes in the skull. Several of these ontogenetic features are significant new observations that impact the relationships within Xenarthra as a whole, or between Xenarthrans and other placental mammals, most notably, the presence of a separate mesethmoid element, the presence of alveoli for a lower deciduous canine and anterior incisor, and the presence of separate rostral and caudal entotympanic elements. A full list of such changes are provided. In addition, the specimen provides information on phylogenetically relevant characters, including features unique to the genus Acratocnus, and features of the clade Choloepodini, including Acratocnus, the smaller extinct Antillean sloth Neocnus, and the extant two-toed sloth Choloepus. Contrary to previous studies, Acratocnus shares as many features with Choloepus as it does with its fellow Antillean form Neocnus in the present study, which is consistent with current morphology-based phylogenetic hypotheses regarding the relationships within Choloepodini. The current study highlights the need for further anatomical and phylogenetic investigations of Antillean sloths (Megalocnidae/Megalonychidae), and juvenile sloths in general.

Influences of Substrate Grain Size on the Burrowing Behavior of Juvenile Meretrix meretrix.

Simple SummaryMeretrix meretrix lives in substrates at a depth of 1–20 cm; the substrate has an influence on its growth, survival, living habits, and behavioral characteristics. In this study, we investigated the effects of different grain size substrates on substrate preference, burrowing ability, and behavior during the substrate selection process of M. meretrix. These results indicated that juvenile M. meretrix had a significant preference for and a stronger burrowing ability in fine sand. As the substrate grain size increased, the burrowing ability and preference of M. meretrix decreased, and these bivalves showed behavioral characteristics such as a prolonged selection time and an increased percentage of movement. In addition, by observing the substrate selection behavior of M. meretrix, we divided the selection process of the substrate by juvenile M. meretrix into four stages: preparation, selection, burrowing, and end stages.The substrate is the key environmental factor that affects the growth, survival, population and distribution of dwelling mollusks in mudflat settings. To clarify the effect of the substrate grain size on soft substrate preference, burrowing ability and behavior during the selection process of juvenile Meretrix meretrix, four different grain size substrates (coarse sand, medium sand, fine sand, and natural substrate) were set up for comparison. The results indicated that: (1) the burrowing ability of juvenile specimens in fine sand was the strongest; (2) the degree (from high to low) of the juvenile’s preference for the four substrates was in the order of fine sand > natural substrate > medium sand > coarse sand; and (3) the selection process of the substrate by the juveniles could be divided into four stages: preparation, selection, burrowing and end stages. These stages showed the behavioral characteristics of a longer selection time and higher percentage of movement in coarse sand. Therefore, our results demonstrated that sea areas or ponds with fine sand as the main component are more suitable for stock enhancement with M. meretrix. These results provide basic data for habitat selection and suitability evaluations for the aquaculture of M. meretrix.

Body size estimation of Caimaninae specimens from the Miocene of South America

Living crocodylians are frequently regarded as morphologically and ecologically conservative, contrasting with the group's rich fossil record, which reveals a much higher diversity. In particular, Caimaninae is a striking example of such diversity, with only six extant species but a myriad of extinct taxa, exhibiting remarkable morphological variation. Their skulls vary substantially, with robust and flattened shapes, ranging from short to long snouts, and serve as a basis for many evolutionary studies in the group. Previous works have demonstrated that the skull is a good proxy to estimate the body size of extinct crocodylians. In this study, we estimate the body size of large Caimaninae specimens from the Miocene of South America, including Purussaurus and Mourasuchus. For that, we elaborated a comprehensive dataset of body size data collected from living crocodylians to generate regression equations. We performed regression analyses both including and excluding juvenile/subadult specimens, to account for the possible influence of ontogeny on the relationship between cranial measurements and body size. Furthermore, we also employed two different approaches (phylogenetic and non-phylogenetic) for estimating the body size of these Miocene caimanines. Our results indicate a significant influence of ontogeny on the body proportions of crocodylians, suggesting that datasets used for estimating the body size of extinct taxa should not include juvenile specimens. Moreover, the phylogenetic approach provided more conservative estimates, possibly as a result of the phylogenetic position of the analyzed taxa, given that the body size metrics are strongly phylogenetically structured in crocodylians. This is the first study to infer the body size of fossil caimanines using different methods and skeletal measurements, as well as a dataset comprised of solely adult crocodylians. In the light of our results, we also discuss the paleobiological implications of the large size of these Miocene caimanines.

PROBABLE JUVENILE FRONTAL OF DASPLETOSAURUS HORNERI (DINOSAURIA: THEROPODA) FROM THE TWO MEDICINE FORMATION OF MONTANA, WITH IMPLICATIONS FOR TYRANNOSAURID ONTOGENY

A partial left frontal (UCM 55499) of a small tyrannosaurid theropod from the Campanian Two Medicine Formation of Montana is described, and is considered to probably represent a juvenile of Daspletosaurus horneri. UCM 55499 compares favorably with the frontals of other young juvenile tyrannosaurid specimens, and its diminutive size suggests that the element comes from a small juvenile individual. Differences (including width of the nasal process, and degree of expansion of the postorbital buttress and the caudal shelf) between it and frontals of the larger individuals of Daspletosaurus horneri are similar to those between juveniles and adults of other tyrannosaurids such as Tyrannosaurus rex, suggesting that overall ontogenetic trends in the frontal bone of Daspletosaurus horneri are largely consistent with the patterns seen in other tyrannosaurids.

Further description of the Kerguelen sandpaper skate Bathyraja irrasa (Rajiformes: Arhynchobatidae) based on additional specimens, including egg cases and embryos.

Adult specimens, additional juvenile specimens, egg cases and embryos were used to provide a more detailed anatomical description of the Kerguelen sandpaper skate Bathyraja irrasa, a species of skate endemic to the Kerguelen Plateau and listed as Vulnerable by the IUCN Red List of Threatened Species. The morphological and meristic data reveal a relatively high level of intraspecific variation, mostly related to size. Egg cases are described for the first time and were shown to vary in colour and fouling depending on the length of time spent in the marine environment. Embryos removed from egg cases represent all stages of embryonic development in this species and include the largest embryo recorded for this species, i.e., 230 mm total length (LT ), which increases the range of size at hatching of B. irrasa to 178-230 mm LT . A number of morphometric and meristic characters varied ontogenetically in B. irrasa, in particular relative tail length, number of tail thorns in the median row and the size of orbits. This study highlights the importance of describing intraspecific variation in species and the importance of egg cases to taxonomic and biological research on oviparous species.

Two new dionychan spiders from arid western South Africa (Araneae: Prodidomidae, Trochanteriidae)

As part of a biodiversity survey in the arid western interior of South Africa, two new species of dionychan spiders were collected and are described herein. The prodidomid genus Namundra Platnick & Bird, 2007, previously known from arid parts of Namibia and Angola, is recorded from South Africa for the first time, and N. murphyi sp. n. is described from a single female. Scanning electron micrographs, based on juvenile specimens only, detail some aspects of the fine morphology of this enigmatic genus for the first time. A new species of the trochanteriid genus Platyoides O. Pickard-Cambridge, 1891, P. robertsi sp. n., is described from three females. DNA barcodes (cytochrome oxidase subunit I, COI) are provided for all of the specimens included in this paper.

Characteristics of anchoveta (Engraulis ringens) schools in the optimum zone and the physiological stress zone of its distribution between 2011 and 2021

AbstractThis study has considered anchoveta acoustic data from the Pelagic Resources Hydroacoustic Assessment Surveys carried out by the Peruvian Sea Institute (IMARPE) and free access satellite data (HYCOM and MODIS from the USA) of some oceanographic variables between the period 2011 and 2021, to know the oceanographic conditions, characteristics of schools and size structure in the optimum zone (OZ) and in the physiological stress zone (PSZ), of their total distribution. The OZ is determined by the extent of the Cold Coastal Waters (CCW), and the PSZ is determined by the mixing of waters, to the north by the CCW‐ESW (Equatorial Surface Waters) and to the west between the CCW‐SSW (Subtropical Surface Waters). The range of sea surface temperature and salinity in the PSZ (16.1–25.0°C and 34.65–35.29, respectively) was wider than in the OZ (14.5–24.0°C and 34.65–35.20, respectively), where a higher number of schools were recorded. Our analyses showed that the morphometric and energetic acoustic descriptors of anchoveta schools in the summer were higher during summers compared to springs. In terms of positional characteristics, the mean depth of the schools in the PSZ was slightly greater than in the OZ. The total size structure of anchoveta in the OZ consisted mainly of juvenile specimens (less than 12 cm total length) in the summer of 2011 and 2013–2014 and in the spring between 2014–2017 and 2021. In the PSZ, adult specimens (greater than 12 cm total length) predominated in summer between 2011–2013, 2015, 2018, and 2021 and in spring between 2011–2013, 2015, and between 2018–2021. However, specimens greater than 10 cm in total length were found in the PSZ. Knowledge of the location of this zone away from the coast will allow a high probability of anchoveta capture of adult specimens during fishing periods.

Phyllotaxis transition over the lifespan of a palm tree using Magnetic Resonance Imaging (MRI) and Terrestrial Laser Scanning (TLS): the case of Jubaea chilensis

BackgroundJubaea chilensis (Molina) Baillon, is a uniquely large palm species endemic to Chile. It is under threatened status despite its use as an ornamental species throughout the world. This research seeks to identify the phyllotaxis of the species based on an original combination of non-destructive data acquisition technologies, namely Magnetic Resonance Imaging (MRI) in saplings and young individuals and Terrestrial Laser Scanning (TLS) in standing specimens, and a novel analysis methodology.ResultsTwo phyllotaxis parameters, parastichy pairs and divergence angle, were determined by analyzing specimens at different developmental stages. Spiral phyllotaxis patterns of J. chilensis progressed in complexity from parastichy pairs (3,2) and (3,5) in juvenile specimens and (5,3), (8,5) and (8,13) for adult specimens. Divergence angle was invariable and averaged 136.9°, close to the golden angle. Phyllotactic pattern changes associated with establishment phase, the adult vegetative and the adult reproductive phases were observed. Both technologies, MRI and TLS proved to be adequate for the proposed analysis.ConclusionsUnderstanding phyllotactic transitions may assist identification of developmental stages of wild J. chilensis specimens. The proposed methodology may also be useful for the study of other palm species.

Age validation and growth in an exploited but poorly studied tropical fish species, the horse-eye jack (Caranx latus)

In this study, we investigated the size-at-age structure and growth of the horse-eye jack (Caranx latus), a highly mobile neritic species with significant commercial value in many parts of the tropical southwest Atlantic. For this, we combined size (standard length – SL) data and otolith readings from 282 juvenile and adult specimens of the species captured across a range of inshore (estuaries) and offshore habitats spread along the Brazilian coast between 2017 and 2019. Both otolith edge-type interpretation and marginal-increment width analysis suggested that annuli are deposited only once a year for C. latus in this part of the world, the opaque band being formed between May and August. The growth parameters estimated by the growth model that fitted best our size-at-age data (von Bertalanffy) were 782.37 mm for Linf, 0.179 for k and − 0.436 years for t0. Interestingly, fish ages differed between local inshore and offshore habitats: 91.8% of the individuals captured in the estuaries (36–223 mm SL) were age-0 fish, while all age groups (0–13 years) were found in the offshore marine area, where sizes ranged from 155 to 760 mm SL. Growth is apparently the fastest in the first year of life, allowing to reach up to 22.75% of the local maximum size expected for the species at one year. These results can inform fishery and ecosystem management strategies in Brazil but also elsewhere, as the present study provides the first assessment of C. latus growth in the South-Western Atlantic based on detailed size-at-age data for most life stages and lifetime habitats.

Interpopulational variation and ontogenetic shift in the venom composition of Lataste's viper (Vipera latastei, Boscá 1878) from northern Portugal

Lataste's viper (Vipera latastei) is a venomous European viper endemic to the Iberian Peninsula, recognised as medically important by the World Health Organization. To date, no comprehensive characterisation of this species' venom has been reported. Here, we analysed the venoms of juvenile and adult specimens of V. latastei from two environmentally different populations from northern Portugal. Using bottom-up venomics, we produced six venom proteomes (three per population) from vipers belonging to both age classes (i.e., two juveniles and four adults), and RP-HPLC profiles of 54 venoms collected from wild specimens. Venoms from juveniles and adults differed in their chromatographic profiles and relative abundances of their toxins, suggesting the occurrence of ontogenetic changes in venom composition. Specifically, snake venom metalloproteinase (SVMP) was the most abundant toxin family in juvenile venoms, while snake venom serine proteinases (SVSPs), phospholipases A2 (PLA2s), and C-type lectin-like (CTLs) proteins were the main toxins comprising adult venoms. The RP-HPLC venom profiles were found to vary significantly between the two sampled localities, indicating geographic variability. Furthermore, the presence/absence of certain peaks in the venom chromatographic profiles appeared to be significantly correlated also to factors like body size and sex of the vipers. Our findings show that V. latastei venom is a variable phenotype. The intraspecific differences we detected in its composition likely mirror changes in the feeding ecology of this species, taking place during different life stages and under different environmental pressures. SignificanceLataste's viper (Vipera latastei) is a medically important viper endemic to the Iberian Peninsula, inhabiting different habitats and undergoing a marked ontogenetic dietary shift. In the current study, we report the first proteomic analysis of V. latastei venom from two environmentally different localities in northern Portugal. Our bottom-up venomic analyses show that snake venom serine proteinases (SVSPs), phospholipases A2 (PLA2s), and C-type lectin-like (CTLs) proteins are the major components of adult V. latastei venom. The comparative analysis of young and adult venoms suggests the occurrence of ontogenetic shift in toxin abundances, with snake venom metalloproteinases (SVMPs) being the predominant toxins in juvenile venoms. Moreover, geographic venom variation between the two studied populations is also detected, with our statistical analyses suggesting that factors like body size and sex of the vipers are possibly at play in its determination.Our work represents the first assessment of the composition of V. latastei venom, and the first step towards a better understanding of the drivers behind its variability.

Closing in the skull: Drivers of ontogenetic changes in emu skulls, Dromaius novaehollandiae (Palaeognathae: Casuariidae)

In modern birds (Palaeognathae and Neognathae), the adult skull combines tightly sutured and co‐ossified units with kinetic flexion zones, serving as a multitasking ‘second hand’. How the skull osteology changes postnatally in different bird lineages is underexplored, especially regarding the morphological and physiological changes across the altricial‐precocial spectrum. For example, it is unknown to what extent internal (i.e. functional biomechanics) or external (i.e. environmental) drivers influence the morphological changes observed through ontogeny and whether those same drivers persist across different lineages. We hypothesize that different regions of the skull (i.e. braincase, mandible, and face) develop skeletally mature features (e.g. suture closure, braincase shape change, robusticity) through ontogeny at different rates due to varying effects from various drivers. In this study, we qualitatively describe and quantitatively analyze, through 3D geometric‐morphometric (GMM) data, an ontogenetic series of 19 emus (Dromaius novaehollandiae), to examine the timing and rate of morphological changes in cranial elements through growth. We observed a mediolateral widening of the posterior portion of the braincase accompanied by an increase in robusticity of the posterior part of the mandible through development. The frontal‐parietal fontanelle closure time varies, with some midsize juvenile specimens having an almost completely or completely closed skull roof. This is in contrast with the feeding apparatus, where the articular and angular region of the mandible remain largely unfused in midsize specimens. Our GMM analysis showed juvenile, subadult, and adult specimens occupying distinct regions of morphospace, showing clear intraspecies variation during ontogeny. We plan on further using GMM to assess when morphological changes start to accumulate in the different regions of the skull and to compare it to our whole skull analysis for the morphological rate changes. With respect to the drivers of the ontogenetic changes, the effects of external drivers (e.g. food type, food availability) are likely small due to husbrandry consistency across emu farms. Internal drivers relating to functional biomechanics, however, may have a larger influence on the ontogenetic differences seen here in that the muscles of the feeding apparatus anchor onto the cranium, accounting for the observed differences in suturing and fontanelle closure and development of the braincase. The morphological complexity seen by including juveniles and subadults in our study highlights gaps in previous postnatal developmental studies. The universal drivers of postnatal ontogeny can be addressed further by applying this same method to other bird lineages on the altricial‐precocial spectrum, allowing us to investigate the degree to which feeding influences the morphological changes and timing to reach the adult condition.

Buoyancy and Hydrostatic Balance in The West Indian Coelacanth Latimeria chalumnae

Buoyancy and balance are important parameters for static or slow moving low‐metabolic aquatic organisms. The extant coelacanths, a single genus (Latimeria) consisting of two species living at moderate depths (100 – 400 m) in the Western Indian Ocean and off Indonesia and representing an ancient group of lobe finned fishes dating back to the early Devonian (410 Myr), have among the lowest metabolic rates of any living vertebrate, and thus would be predicted to expend precious little energy to maintain buoyancy and balance. Previous observations on living coelacanths support the hypothesis that the coelcanth is neutrally buoyant and is in close to perfect hydrostatic balance in any body posture. Likewise, point‐by‐point measurements of tissue composition have shown a generally high lipid content of coelacanth tissue supporting neutral buoyancy without a gas filled bladder as found in other sarcopterygians (lungs) and in many actinopterygians (swim bladder). However, precise measurements of buoyancy and hydrostatic balance at different depths have never been made in the coelacanth. Here we show using non‐invasive imaging that buoyancy of the coelacanth closely matches its depth distribution and a close‐to‐perfect balance can be used by the animal to change body posture with little effort. We found that the lipid filled “fatty organ” of the coelacanth is well adapted to support neutral buoyancy and simple maneuvers of fins can cause a considerable shift in torque around the pitch axis. This allows the coelacanth to assume and remain in any body posture like horizontal orientation, headstand or tail stand with little physical effort. Our results demonstrate a close match between tissue composition in the extant coelacanth, depth range and behavior (e.g. effortless vertical drift hunting with the electrosensitive rostral organ in close contact with the substrate). We anticipate our non‐invasive technique of mapping tissue components to be a starting point for more sophisticated models of buoyancy and hydrostatic balance in aquatic vertebrates in general. Specifically, we suggest the technique can be used on the few late term and juvenile coelacanth specimens in existence to predict the most likely habitat depth of the juvenile life stage which is currently unknown.

Living in darkness: Exploring adaptation of Proteus anguinus in 3 dimensions by X-ray imaging.

BackgroundLightless caves can harbour a wide range of living organisms. Cave animals have evolved a set of morphological, physiological, and behavioural adaptations known as troglomorphisms, enabling their survival in the perpetual darkness, narrow temperature and humidity ranges, and nutrient scarcity of the subterranean environment. In this study, we focused on adaptations of skull shape and sensory systems in the blind cave salamander, Proteus anguinus, also known as olm or simply proteus—the largest cave tetrapod and the only European amphibian living exclusively in subterranean environments. This extraordinary amphibian compensates for the loss of sight by enhanced non-visual sensory systems including mechanoreceptors, electroreceptors, and chemoreceptors. We compared developmental stages of P. anguinus with Ambystoma mexicanum, also known as axolotl, to make an exemplary comparison between cave- and surface-dwelling paedomorphic salamanders.FindingsWe used contrast-enhanced X-ray computed microtomography for the 3D segmentation of the soft tissues in the head of P. anguinus and A. mexicanum. Sensory organs were visualized to elucidate how the animal is adapted to living in complete darkness. X-ray microCT datasets were provided along with 3D models for larval, juvenile, and adult specimens, showing the cartilage of the chondrocranium and the position, shape, and size of the brain, eyes, and olfactory epithelium.Conclusions P. anguinus still keeps some of its secrets. Our high-resolution X-ray microCT scans together with 3D models of the anatomical structures in the head may help to elucidate the nature and origin of the mechanisms behind its adaptations to the subterranean environment, which led to a series of troglomorphisms.

The Nemesia trapdoor spider fauna of the Maltese archipelago, with the description of two new species (Araneae, Mygalomorphae, Nemesiidae)

Contrary to what its name suggests, Nemesia arboricola is not strictly arboreal in habit. Here we compare female specimens of N. arboricola collected from arboreal and terrestrial nests. We furthermore describe the male of N. arboricola for the first time as well as two recently discovered species of Nemesia (N. maltensis sp. nov. and N. cominensis sp. nov.). Nemesia maltensis is described from both sexes, N. cominensis is described from the female and a juvenile male specimen. For N. cominensis we discuss the sexual dimorphism of juvenile male and female spiders. Field observations and laboratory observations show remarkable features of the Maltese Nemesia fauna that are unknown from Nemesia species found elsewhere. Particularly, the arboreal dwellings of N. arboricola and the absence of a trapdoor to close off the burrow entrance in N. maltensis appear to be exceptional. The composition of the Maltese Nemesia fauna, as located in the central Mediterranean, is finally discussed in relation to the different Nemesia species-complexes occurring in the eastern and western Mediterranean basin.

The effect of captivity on craniomandibular and calcaneal ontogenetic trajectories in wild boar.

Deciphering the plastic (i.e., nonheritable) changes induced by human control over wild animals in the archeological record is challenging. Previous studies detected morphological markers associated with captivity in the cranium, mandible, and calcaneus of adult wild boar (Sus scrofa) but the developmental trajectories leading up to these changes during ontogeny remain unknown. To assess the impact of growth in a captive environment on morphological structures during postnatal ontogeny, we used an experimental approach focusing on the same three structures and taxon. We investigated the form and size differences of captive-reared and wild-caught wild boar during growth using three-dimensional landmark-based geometric morphometrics. Our results provide evidence of an influence of captivity on the morphology of craniomandibular structures, as wild specimens are smaller than captive individuals at similar ages. The food resources inherent to anthropogenic environments may explain some of the observed differences between captive-reared and wild specimens. The calcaneus presents a different contrasted pattern of plasticity as captive and wild individuals differ in terms of form but not in terms of size. The physically more constrained nature of the calcaneus and the direct influence of mobility reduction on this bone may explain these discrepancies. These results provide new methodological perspectives for bioarchaeological approaches as they imply that the plastic mark of captivity can be observed in juvenile specimens in the same way it has been previously described in adults.

Fisheries bycatch and conservation priorities of young sharks (Chondrichthyes: Elasmobranchii) in the Eastern Mediterranean

Sharks are one of the most threatened groups of marine animals because of high exploitation rates coupled with low resilience to fishing pressure. We provide information on the current status of the young sharks caught in fishing nets in Iskenderun and Mersin Bays in the eastern Mediterranean, based on fishery-dependent surveys conducted between 2010 and 2021. Sharks were found in bycatches in trawling nets, trammel nets, bottom longlines and fishing lines. Incidental captures of young-of-the-year or juvenile specimens (n=269) included 15 species and the data indicate that İskenderun and Mersin Bays may serve as a nursery ground for the new-born and young individuals especially for the Blackmouth Catshark (Galeus melastomus), the Lesser Spotted Dogfish (Scyliorhinus canicula), and the Velvet Belly (Etmopterus spinax). If necessary measures are taken, bycatch can be reduced to a certain limit, or even eliminated for shark species in the Mediterranean Sea.

A new species of the productid brachiopod Aseptella from the Lower Carboniferous of the Cantabrian Mountains (Spain)

A new species of Aseptella, A. beetsi, is described fom Lower Carboniferous, Visean (Arundian-Holkerian) to lower Namurian (Arnsbergian) griotte limestones of the Cantabrian Mountains, variously called Alba or Genicera Formation. The new species, with a weakly developed brachia! median septum, seems to be the ancestor of the type species, A. asturica, from the Bashkirian of Cantabrian Mts, which only develops a median septum in its juvenile specimens. The new species shows a peculiar offshoot of the marginal ridge, possibly for better separation of the ears. The systematic position of the genus Aseptella is briefly discussed as are the implications of the occurrence of this genus in Argentina.

Taxonomy and diversity of slit‐band gastropods (Order Pleurotomariida) and some slit bearing Caenogastropoda from the Pennsylvanian of the USA

AbstractPleurotomariida have the longest fossil record among living gastropods and are diverse and abundant in the middle and upper Palaeozoic. Its traditional classification is based on adult shell characters. The early shell morphology has been largely unknown. We describe exceptionally well‐preserved Pleurotomariida from the Pennsylvanian marine shales of Texas, Oklahoma, Kansas and Ohio. In total, 38 species representing 19 genera are described, including 10 new species, one new genus and one new subgenus:Eirlysella buckhornensisgen. et sp. nov.,Shansiella(Oklahomaella)globilineatasubgen. et sp. nov.,Phymatopleura girtyi,Phymatopleura conica,Worthenia(Yochelsonospira)kuesi,Dictyotomaria turrisbabel,Paragoniozona yanceyi,Spiroscala shwedagoniformis,Peruvispira oklahomaensis,Baylea tenera. Replacement names areParagoniozona ornatanom. nov. (forPleurotomaria asperaGirty),Spiroscala quasipulchranom. nov. (forEuconospira pulchraBatten). The early ontogenetic shells including protoconchs and early teleoconchs are reported in detail for the first time for most taxa. Most species have a protoconch of one whorl as that of living Vetigastropoda. Planktotrophic protoconchs (multi‐whorled larval shells with sinusigera) are reported forPlatyzonaandPeruvispira; they are therefore placed in the family Goniasmatidae (Caenogastropoda). Repaired shell scars were found in juvenile Pleurotomariida specimens (c. 1 mm), suggesting exposure to predation from an early stage of ontogeny. Pleurotomariida are strongly dominant in surface samples of the Finis Shale (Texas) but in bulk samples using fine mesh‐sizes, dominance is much less pronounced, indicating a change in clade proportion depending on sampling method. The taxonomic richness and abundance of Pleurotomariida seen in these Carboniferous shales have not been reported from post‐Triassic formations.