Preserved appendages in a Silurian binodicope: implications for the evolutionary history of ostracod crustaceans.

Ostracod crustaceans originated at least 500 Ma ago. Their tiny bivalved shells represent the most species-abundant fossil arthropods, and ostracods are omnipresent in a wide array of freshwater and marine environments today and in the past. Derima paparme gen. et sp. nov. from the Herefordshire Silurian Lagerstätte (~430 Ma) in the Welsh Borderland, UK, is one of only a handful of exceptionally preserved ostracods (with soft parts as well as the shell) known from the Palaeozoic. A male specimen provides the first evidence of the appendages of Binodicopina, a major group of Palaeozoic ostracods comprising some 135 Ordovician to Permian genera. The appendage morphology of D. paparme, but not its shell, indicates that binodicopes belong to Podocopa. The discovery that the soft-part morphology of binodicopes allies them with podocopes affirms that using the shell alone is an unreliable basis for classifying certain fossil ostracods, and knowledge of soft-part morphology is critical for the task. Current assignment of many fossil ostracods to higher taxa, and therefore the evolutionary history of the group, may require reconsideration.

Behavior and morphology combine to influence energy dissipation in mantis shrimp (Stomatopoda).

Animals deliver and withstand physical impacts in diverse behavioral contexts, from competing rams clashing their antlers together to archerfish impacting prey with jets of water. Though the ability of animals to withstand impact has generally been studied by focusing on morphology, behaviors may also influence impact resistance. Mantis shrimp exchange high-force strikes on each other's coiled, armored telsons (tailplates) during contests over territory. Prior work has shown that telson morphology has high impact resistance. I hypothesized that the behavior of coiling the telson also contributes to impact energy dissipation. By measuring impact dynamics from high-speed videos of strikes exchanged during contests between freely moving animals, I found that approximately 20% more impact energy was dissipated by the telson as compared with findings from a prior study that focused solely on morphology. This increase is likely due to behavior: because the telson is lifted off the substrate, the entire body flexes after contact, dissipating more energy than exoskeletal morphology does on its own. While variation in the degree of telson coil did not affect energy dissipation, proportionally more energy was dissipated from higher velocity strikes and from strikes from more massive appendages. Overall, these findings show that analysis of both behavior and morphology is crucial to understanding impact resistance, and suggest future research on the evolution of structure and function under the selective pressure of biological impacts.

The Sensory Structures of the Carapace of Male Tantulocarida (Crustacea) Are not Homologous to the Lattice Organs of Thecostraca.

Ultrastructural studies on the sensory apparatus of male Tantulocarida (Crustacea) have been conducted for the first time. Comparative morphological analysis with the specialized sensory structures of Thecostraca, known as lattice organs, has allowed for conclusions about possible homologies and further clarification of the phylogenetic position of Tantulocarida.

Mislabeling and nomenclatorial confusion of Typhlotanais sandersi Kudinova-Pasternak, 1985 (Crustacea: Tanaidacea) and establishment of a new genus.

Re-examination of historical collections allowed us to resolve the taxonomic status of Typhlotanais sandersi Kudinova-Pasternak, 1985, originally described based on a single specimen from Great-Meteor Seamount. The holotype of this species was considered lost and the species redescribed based on a second specimen from the type locality by Blazewicz-Paszkowycz (2007a), who placed Ty. sandersi on a newly established genus Typhlamia. Thorough morphological analysis of Typhlamia and Typhlotanais species and recently obtained genetic data of typhlotanaids from N Atlantic and NW Pacific waters allow us to conclude that the redescription of Ty. sandersi by Blazewicz-Paszkowycz (2007a) was based on a wrongly labelled specimen that, rather than a type of Ty. sandersi, represents in fact a new species of Typhlamia. The morphological comparison of the type species of Typhlotanais (Ty. aequiremis) with all 'long-bodied' typhlotanaid taxa with rounded pereonites margins (i.e., Typhlamia, Pulcherella, Torquella), and the use of genetic evidence, support the establishment of a new genus to accommodate: Ty. sandersi, Ty. angusticheles Kudinova-Pasternak, 1989, and a third species from N Atlantic waters, that is described here for the first time. Current knowledge on 'long-bodied' typhlotanaids with rounded pereonites is summarised and a taxonomical key for their identification provided.

Morphological types of male copulatory organs of Bicornucythere bisanensis (Ostracoda, Crustacea) and the description of a new Bicornucythere species.

This study is designed to evaluate the male copulatory organs and carapace size of the inner bay benthic ostracod Bicornucythere bisanensis. The male copulatory organs demonstrate noticeable intraspecific variation in the distal lobe, especially the length of the tip, which shows a gradual variation; whereas the thickness of the distal lobe is conservative within the species. The population from central Japan (Aburatsubo Cove) showed remarkable morphological variations, with four copulatory organ types, each type defined by a combination of four shapes of the right and left distal lobes (Shape R, r, L, and l). While the variety of carapace morphotypes have been previously reported, our findings suggest that one morphotype from western Japan (Misumi-cho) should be treated as a distinct species. Thus, we described it as Bicornucythere misumiensis sp. nov.

In situ determination of the extreme damage resistance behavior in stomatopod dactyl club.

The structure and mechanical properties of the stomatopod dactyl club have been studied extensively for its extreme impact tolerance, but a systematic in situ investigation on the multiscale mechanical responses under high-speed impact has not been reported. Here the full dynamic deformation and crack evolution process within projectile-impacted dactyl using combined fast 2D X-ray imaging and high-resolution ex situ tomography are revealed. The results show that hydration states can lead to significantly different toughening mechanisms inside dactyl under dynamic loading. A previously unreported 3D interlocking structural design in the impact surface and impact region is reported using nano X-ray tomography. Experimental results and dynamic finite-element modeling suggest this unique structure plays an important role in resisting catastrophic structural damage and hindering crack propagation. This work is a contribution to understanding the key toughening strategies of biological materials and provides valuable information for biomimetic manufacturing of impact-resistant materials in general.

How body patterning might have worked in the evolution of arthropods-A case study of the mystacocarid Derocheilocaris remanei (Crustacea, Oligostraca).

Body organization within arthropods is enormously diverse, but a fusion of segments into "functional groups" (tagmatization) is found in all species. Within Tetraconata/Pancrustacea, an anterior head, a locomotory thorax region, and a posterior, mostly limbless tagma known as the abdomen is present. The posterior-most tagma in crustaceans is frequently confused with the malacostracan, for example, decapod pleon often misleadingly termed abdomen, however, its evolutionary and developmental origin continues to pose a riddle, especially the completely limbless abdomen of the "entomostracan morphotype" (e.g., fairy shrimps). Since the discovery of Hox genes and their involvement in specifying the morphology or identity of segments, tagmata, or regions along the anteroposterior axis of an organism, only a few studies have focused on model organisms representing the "entomostracan morphotype" and used a variety of dedicated Hox genes and their transcription products to shine light on abdomen formation. The homeotic genes or the molecular processes that determine the identity of the entomostracan abdomen remain unknown to date. This study focuses on the "entomostracan morphotype" representative Derocheilocaris remanei (Mystacocarida). We present a complete overview of development throughout larval stages and investigate homeotic gene expression data using the antibody FP6.87 that binds specifically to epitopes of Ultrabithorax/Abdominal-A proteins. Our results suggest that the abdomen in Mystacocarida is bipartite (abdomen I + abdomen II). We suggest that the limbless abdomen is an evolutionary novelty that evolved several times independently within crustaceans and which might be the result of a progressive reduction of former thoracic segments into abdominal segments.

Geometric morphometric analysis of morphologic disparity, intraspecific variation and ontogenetic allometry of beyrichitine ammonoids.

Beyrichitine ammonoids of NV Nevada reveal a high taxonomic diversity of Anisian (Middle Triassic). This diversity is, however, in contrast to their relatively low morphologic disparity. Depending on the exact definition, morphologic disparity of a data set is a direct consequence of the sum of all ontogenetic changes. In the past, however, the interplay of both morphological processes has only rarely been addressed. Using geometric morphometric methods, this study aims at a quantification of allometric processes and the morphologic disparity of beyrichitine ammonoids. The multivariate statistical analysis revealed that morphologic disparity, intraspecific variation respectively, within and between the studied species seems to be the result of deviations in the ontogenetic allometric growth pattern (i.e. heterochrony). During deposition of the studied stratigraphic sequence, a general progressive pedomorphism (juvenilization) was observed. The intraspecific variability pattern coincides with the total morphologic disparity of the analyzed species, which suggests that intraspecific variability facilitated morphologic disparity. The comparison of ontogenetic allometric patterns and changes in intraspecific variation and morphologic disparity are likely to refine our understanding of the intrinsic factors influencing the speciation of this group.

Chondrochelia Gutu, 2016 (Crustacea, Peracarida, Tanaidacea, Leptocheliidae) from North America: new species, redescription and distribution using morphological and molecular data.

Until now, four species of the genus Chondrochelia Gutu, 2016 have been recorded from America. Using morphological and molecular data, we were able to recognize and describe two new species, Chondrochelia caribensis sp. nov. from the Mexican Caribbean and Chondrochelia winfieldi sp. nov. from the Gulf of Mexico. We found significant genetic divergence values between species based on the nucleotide sequences of cytochrome oxidase subunit I to support the morphological data. Also, the range of distribution of two species: Chondrochelia mexicana (Jarquín-González, García-Madrigal & Carrera-Parra, 2015) and Chondrochelia ortizi (Jarquín-González, 2016), were expanded within their described geographic regions. In contrast, the supposed distribution of the Brazilian C. dubia in the Mexican Caribbean and the Gulf of Mexico was rejected. Additionally, Chondrochelia algicola (Harger, 1878) was redescribed based upon type material. Minute details and ornamentation of some structures of three species were examined using SEM.

A New Species of Pseudostrandesia Savatenalinton and Martens, 2009 (Ostracoda, Crustacea) Collected from Two Pet Shops in Central Japan: an Alien Species?

An undescribed species of freshwater ostracod belonging to the genus Pseudostrandesia Savatenalinton and Martens, 2009 was collected from two pet shops in the Kanto region of central Japan. This species, herein named Pseudostrandesia tenebrarum sp. nov., is similar to four species previously reported from Southeast Asia, but can be distinguished by carapace and appendage features. It is the second species of the genus for which males are known. Of the nine previously described species in the genus, one is exclusively known from Turkey, and the others are found in Southeast Asia and the vicinity, one of which is also recorded in India and east China. There are two scenarios to explain the existence of Pseudostrandesia tenebrarum sp. nov. in pet shops in Japan: it is either native to Japan but has yet to be discovered in its natural habitat, or it is an alien species, perhaps unwittingly imported with plants or fish for the pet trade. We review the likelihood of both scenarios, and conclude that although there is insufficient evidence to be sure, it is potentially an alien species in Japan. The most likely origin is Southeast Asia, as evidenced by its close morphological resemblance to particular Southeast Asian species. Juveniles as well as adults were recovered, indicating that this species is reproducing in the pet trade, supporting the notion that it has invasive potential to areas outside of its natural range. The description and report of this species highlights a possible introduction of an alien species to Japan, and facilitates further monitoring.

Three new species of Heteromysis (Crustacea: Mysida) from coral reef aquaria in Florida and Central Europe.

Three new species of the genus Heteromysis S.I. Smith, 1873 (tribus Heteromysini), are described from a rich stock of mysids obtained on request from the international community of professional aquarium keepers. The 18S rDNA and COI sequences of the three species were distinct from each other and also from other sequences published in DNA databases. Heteromysis (Olivemysis) schoenbrunnensis sp. nov. is morphologically characterized within the subgenus Olivemysis based on the structure of the first and second antennae, male pleopods, uropods, and telson. Heteromysis (Heteromysis) gulfarii sp. nov. is outstanding within the subgenus Heteromysis by sexually dimorphic modified setae on the antennular trunk. These setae are non-dimorphic in the very similar Heteromysis (Heteromysis) korntalensis sp. nov. Both species H. gulfarii and to a lesser degree also H. korntalensis show modified eyes, subquadrate in dorsal view, eyestalks anteriorly tapering in lateral view; small, well-developed cornea implanted laterally on modified eyestalk. Apart from eye structure H. gulfarii and H. korntalensis clearly fall morphologically within the nominotypical subgenus Heteromysis.

Triassic clam shrimps ("Conchostraca"; Branchiopoda: Diplostraca) from Mallorca: Taxonomic description and interregional comparisons.

We describe four upper Lower Triassic to lower Middle Triassic clam shrimp-bearing intervals from Mallorca, which include the clam shrimp species Hornestheria sp. aff. Hornestheria sollingensis and several other forms of carapace valve morphology: Hornestheria? Morphotype 1, Hornestheria? Morphotype 2, and other undetermined carapace valves. All of this material was obtained from red-bed units cropping out in the Serra de Tramuntana mountains of Mallorca (western Mediterranean). Except for a few morphologically similar carapace valves of Middle Triassic age from China, Hornestheria is known only from the type locality of its type species, Hornestheria sollingensis Kozur et Lepper, in the Solling Formation (Middle Buntsandstein Subgroup) in the German part of the Central European Basin. According to its original definition, the larval carapace valve of Hornestheria Kozur et Lepper is characterized by a radial sculpture, but this characteristic apparently is only variably developed. Due to both a limited number of previously known occurrences of Hornestheria and its poorly known carapace valve morphology, open nomenclature is applied to the taxonomy herein. The studied specimens were freshly collected from outcrop sections composed of greyish-green to greyish-red laminated claystones and siltstones that accumulated in a fluvial facies. The clam shrimp specimens are accompanied by remains of insects and fishes, invertebrate and tetrapod ichnofossils, and micro-/macroplant remains, all of which either have been described by previous workers or are currently part of a separate study.

Optimized Hierarchical Structure and Chemical Gradients Promote the Biomechanical Functions of the Spike of Mantis Shrimps.

The tail spike of the mantis shrimp is the appendage for counteracting the enemy from behind. Here, we investigate the correlations between the chemical compositions, the microstructures, and the mechanical properties of the spike. We find that the spike is a hollow beam with a varying cross section along the length. The cross section comprises four different layers with distinct features of microstructures and chemical compositions. The local mechanical properties of these layers correlate well with the microstructures and chemical compositions, a combination of which effectively restricts the crack propagation while maximizing the release of strain energy during deformation. Finite element analysis and mechanics modeling demonstrate that the optimized structure of the spike confines the mechanical damage in the region near the tip and prevents catastrophic breakage at the base. Furthermore, we use a 3D printing technique to fabricate multiple hollow cylindrical samples consisting of biomimetic microstructures of the spike and confirm that the combination of the Bouligand structure with radially oriented parallel sheets greatly improves the toughness and strength during compression tests. The multiscale design strategy of the spike revealed here is expected to be of great interest for the development of novel bioinspired materials.

Convergent evolution of optic lobe neuropil in Pancrustacea.

A prevailing opinion since 1926 has been that optic lobe organization in malacostracan crustaceans and insects reflects a corresponding organization in their common ancestor. Support for this refers to malacostracans and insects both possessing three, in some instances four, nested retinotopic neuropils beneath their compound eyes. Historically, the rationale for claiming homology of malacostracan and insect optic lobes referred to those commonalities, and to comparable arrangements of neurons. However, recent molecular phylogenetics has firmly established that Malacostraca belong to Multicrustacea, whereas Hexapoda and its related taxa Cephalocarida, Branchiopoda, and Remipedia belong to the phyletically distinct clade Allotriocarida. Insects are more closely related to remipedes than are either to malacostracans. Reconciling neuroanatomy with molecular phylogenies has been complicated by studies showing that the midbrains of remipedes share many attributes with the midbrains of malacostracans. Here we review the organization of the optic lobes in Malacostraca and Insecta to inquire which of their characters correspond genealogically across Pancrustacea and which characters do not. We demonstrate that neuroanatomical characters pertaining to the third optic lobe neuropil, called the lobula complex, may indicate convergent evolution. Distinctions of the malacostracan and insect lobula complexes are sufficient to align neuroanatomical descriptions of the pancrustacean optic lobes within the constraints of molecular-based phylogenies.

The lobula plate is exclusive to insects.

Just one superorder of insects is known to possess a neuronal network that mediates extremely rapid reactions in flight in response to changes in optic flow. Research on the identity and functional organization of this network has over the course of almost half a century focused exclusively on the order Diptera, a member of the approximately 300-million-year-old clade Holometabola defined by its mode of development. However, it has been broadly claimed that the pivotal neuropil containing the network, the lobula plate, originated in the Cambrian before the divergence of Hexapoda and Crustacea from a mandibulate ancestor. This essay defines the traits that designate the lobula plate and argues against a homologue in Crustacea. It proposes that the origin of the lobula plate is relatively recent and may relate to the origin of flight.

What crustaceans can tell us about the evolution of insect wings and other morphologically novel structures.

Acquisition of novel structures often has a profound impact on the adaptation of organisms. The wing of insects is one such example, facilitating their massive success and enabling them to become the dominant clade on this planet. However, its evolutionary origin as well as the mechanisms underpinning its evolution remain elusive. Studies in crustaceans, a wingless sister group of insects, have played a pivotal role in the wing origin debate. Three recent investigations into the genes related to insect wings and legs in crustaceans provided intriguing insights into how and where insect wings evolved. Interestingly, each study proposes a distinct mechanism as a key process underlying insect wing evolution. Here, I discuss what we can learn about the evolution of insect wings and morphological novelty in general by synthesizing the outcomes of these studies.

A developmental perspective of homology and evolutionary novelty.

The development and evolution of multicellular body plans is complex. Many distinct organs and body parts must be reproduced at each generation, and those that are traceable over long time scales are considered homologous. Among the most pressing and least understood phenomena in evolutionary biology is the mode by which new homologs, or "novelties" are introduced to the body plan and whether the developmental changes associated with such evolution deserve special treatment. In this chapter, we address the concepts of homology and evolutionary novelty through the lens of development. We present a series of case studies, within insects and vertebrates, from which we propose a developmental model of multicellular organ identity. With this model in hand, we make predictions regarding the developmental evolution of body plans and highlight the need for more integrative analysis of developing systems.

Exploring the versatility of the perfused crustacean gill as a model for transbranchial transport processes.

The study of transbranchial ion and gas transport of water-breathing animals has long been a useful means of modeling transport processes of higher vertebrate organs through comparative physiology. The molecular era of biological research has brought forward valuable information detailing shifts in gene expression related to environmental stress and the sub-cellular localization of transporters; however, purely molecular studies can cause hypothetical transport mechanisms and hypotheses to be accepted without any direct physiological proof. Isolated perfused gill experiments are useful for testing most of these hypotheses and can sometimes be used outright to develop a well-supported working model for transport processes relating to an animal's osmoregulation, acid-base balance, nitrogen excretion, and respiratory gas exchange as well as their sensitivity to pollutants and environmental stress. The technique allows full control of internal hemolymph-like saline as well as the ambient environmental fluid compositions and can measure the electrophysiological properties of the gill as well as the transport rates of ions and gases as they traverse the gill epithelium. Additives such as pharmaceuticals or peptides as well as the exclusion of ions from the media are commonly used to identify the importance of specific transporters to transport mechanisms. The technique can also be used to identify the penetrance, retention, and localization of pollutants within the gill epithelium or to explore the uptake and metabolism of nutrients directly from the ambient environment. While this technique can be applied to virtually any isolatable organ, the anatomy and rigidity of the decapod crustacean gill make it an ideal candidate for most experimental designs.

Immunohistochemical Localization of a GnRH-Like Peptide in the Nerve Ganglion of Three Classes of Crustaceans, the Tadpole Shrimp Triops longicaudatus (Branchiopoda), the Barnacle Balanus crenatus (Hexanauplia), and the Hermit Crab Pagurus filholi (Malacostraca).

In vertebrates, gonadotropin-releasing hormone (GnRH) regulates gonadal maturation by stimulating the synthesis and release of pituitary gonadotropins. GnRH has also been identified in invertebrates. Crustacea consists of several classes including Cephalocarida, Remipedia, Branchiopoda (e.g., tadpole shrimp), Hexanauplia (e.g., barnacle) and Malacostraca (e.g., shrimp, crab). In the malacostracan crustaceans, the presence of GnRH has been detected in several species, mainly by immunohistochemistry. In the present study, we examined whether a GnRH-like peptide exists in the brain and/or nerve ganglion of three classes of crustaceans, the tadpole shrimp Triops longicaudatus (Branchiopoda), the barnacle Balanus crenatus (Hexanauplia), and the hermit crab Pagurus filholi (Malacostraca), by immunohistochemistry using a rabbit polyclonal antibody raised against chicken GnRH-II (GnRH2). This antibody was found to recognize the giant freshwater prawn Macrobrachium rosenbergii GnRH (MroGnRH). In the tadpole shrimp, GnRH-like-immunoreactive (ir) cell bodies were located in the circumesophageal connective of the deuterocerebrum, and GnRH-like-ir fibers were detected also in the ventral nerve cord. In the barnacle, GnRH-like-ir cell bodies and fibers were located in the supraesophageal ganglion (brain), the subesophageal ganglion, and the circumesophageal connective. In the hermit crab, GnRH-like-ir cell bodies were detected in the anterior-most part of the supraesophageal ganglion and the subesophageal ganglion. GnRH-like-ir fibers were observed also in the thoracic ganglion and the eyestalk. These results suggest that a GnRH-like peptide exists widely in crustacean species.

More than one way to smell ashore - Evolution of the olfactory pathway in terrestrial malacostracan crustaceans.

Crustaceans provide a fascinating opportunity for studying adaptations to a terrestrial lifestyle because within this group, the conquest of land has occurred at least ten times convergently. The evolutionary transition from water to land demands various morphological and physiological adaptations of tissues and organs including the sensory and nervous system. In this review, we aim to compare the brain architecture between selected terrestrial and closely related marine representatives of the crustacean taxa Amphipoda, Isopoda, Brachyura, and Anomala with an emphasis on the elements of the olfactory pathway including receptor molecules. Our comparison of neuroanatomical structures between terrestrial members and their close aquatic relatives suggests that during the convergent evolution of terrestrial life-styles, the elements of the olfactory pathway were subject to different morphological transformations. In terrestrial anomalans (Coenobitidae), the elements of the primary olfactory pathway (antennules and olfactory lobes) are in general considerably enlarged whereas they are smaller in terrestrial brachyurans compared to their aquatic relatives. Studies on the repertoire of receptor molecules in Coenobitidae do not point to specific terrestrial adaptations but suggest that perireceptor events - processes in the receptor environment before the stimuli bind - may play an important role for aerial olfaction in this group. In terrestrial members of amphipods (Amphipoda: Talitridae) as well as of isopods (Isopoda: Oniscidea), however, the antennules and olfactory sensilla (aesthetascs) are largely reduced and miniaturized. Consequently, their primary olfactory processing centers are suggested to have been lost during the evolution of a life on land. Nevertheless, in terrestrial Peracarida, the (second) antennae as well as their associated tritocerebral processing structures are presumed to compensate for this loss or rather considerable reduction of the (deutocerebral) primary olfactory pathway. We conclude that after the evolutionary transition from water to land, it is not trivial for arthropods to establish aerial olfaction. If we consider insects as an ingroup of Crustacea, then the Coenobitidae and Insecta may be seen as the most successful crustacean representatives in this respect.