Dorsal Projection Research Articles

Potentially Neomorphic Cranial Bone Revealed in First Micro‐CT Study of Southern Cassowary Casque Development

Modern cassowaries are a group of flightless birds that possess unusual cranial ornamentation. These bony and keratinous dorsal skull projections, referred to as casques, have been of interest to anatomists for the past two centuries. The osteological configuration of cassowary casques has been described by numerous authors during that period; however, interpretations have differed widely. This ambiguity, arising from purely direct observational studies has prompted the need to redescribe the osteology of cassowary casques across an extensive developmental series (n = 54) using micro-computed tomography (μCT) imaging, digital visualization, and gross dissection. Tracking cranial elements from embryo to adult form in southern cassowaries (Casuarius casuarius) and comparing those bones to non-casqued ratites (Dromaius novaehollandiae and Struthio camelus)revealed that eight distinct cranial bones comprise the casques of adult C. casuarius. The cranial pattern of three paired (nasals, lacrimals, frontals) and two unpaired elements (median casque element, mesethmoid) is unique among the bony ornaments of extant avians. Our analysis documents the median casque element as being distinct from the mesethmoid and absent in other, closely related flightless birds, suggesting this bone is neomorphic in modern cassowaries. This research sets an anatomical baseline for future studies regarding comparative ornament ontogeny and casque function in these poorly-understood birds, as well as the evolutionary and developmental origins of cranial ornamentation across vertebrates.

Coordination of escape and spatial navigation circuits orchestrates versatile flight from threats

Naturalistic escape requires versatile context-specific flight with rapid evaluation of local geometry to identify and use efficient escape routes. It is unknown how spatial navigation and escape circuits are recruited to produce context-specific flight. Using mice, we show that activity in cholecystokinin-expressing hypothalamic dorsal premammillary nucleus (PMd-cck) cells is sufficient and necessary for context-specific escape that adapts to each environment's layout. In contrast, numerous other nuclei implicated in flight only induced stereotyped panic-related escape. We reasoned the dorsal premammillary nucleus (PMd) can induce context-specific escape because it projects to escape and spatial navigation nuclei. Indeed, activity in PMd-cck projections to thalamic spatial navigation circuits is necessary for context-specific escape induced by moderate threats but not panic-related stereotyped escape caused by perceived asphyxiation. Conversely, the PMd projection to the escape-inducing dorsal periaqueductal gray projection is necessary for all tested escapes. Thus, PMd-cck cells control versatile flight, engaging spatial navigation and escape circuits.

Whole-Brain Mapping the Direct Inputs of Dorsal and Ventral CA1 Projection Neurons.

The CA1, an important subregion of the hippocampus, is anatomically and functionally heterogeneous in the dorsal and ventral hippocampus. Here, to dissect the distinctions between the dorsal (dCA1) and ventral CA1 (vCA1) in anatomical connections, we systematically analyzed the direct inputs to dCA1 and vCA1 projection neurons (PNs) with the rabies virus-mediated retrograde trans-monosynaptic tracing system in Thy1-Cre mice. Our mapping results revealed that the input proportions and distributions of dCA1 and vCA1 PNs varied significantly. Inside the hippocampal region, dCA1 and vCA1 PNs shared the same upstream brain regions, but with distinctive distribution patterns along the rostrocaudal axis. The intrahippocampal inputs to the dCA1 and vCA1 exhibited opposite trends, decreasing and increasing gradually along the dorsoventral axis, respectively. For extrahippocampal inputs, dCA1 and vCA1 shared some monosynaptic projections from certain regions such as pallidum, striatum, hypothalamus, and thalamus. However, vCA1, not dCA1, received innervations from the subregions of olfactory areas and amygdala nuclei. Characterization of the direct input networks of dCA1 and vCA1 PNs may provide a structural basis to understand the differential functions of dCA1 and vCA1.

Buestanmyia chiriboga gen. nov. et sp. nov. (Diptera: Tabanidae: Diachlorini) from the Ecuadorian Andes.

Buestanmyia gen. nov., is described from Pichincha Province, Ecuador with one included species, with B. chiriboga sp. nov. It is characterized by very short and scarce ommatrichia, frons wide and slightly divergent below, basal callus subquadrate with median dorsal projection reaching half the height of the frons, ocellar triangle and ocelli absent, scape 3.5x the length of the pedicel, scape and pedicel with strong and erect hairs, proboscis less than the length of the head, basicosta bare, wings slightly smoky, with clouds on the cells costal and subcostal, vein R4 with a short appendix; cell cup with short appendix.

Two new species and two new country records for Meriania (Melastomataceae) from northern Peru

Two new species of Meriania (Melastomataceae, Merianieae) and two new records from northern Peru are described and illustrated here. Meriania penningtonii is clearly different from all other species of Meriania by its quadrangular and 4‐winged internodes, calyx with whitish callose dorsal projections and spreading reddish‐purple corollas; Meriania dazae differs from the other species by the combination of the calyx with claw‐shaped dorsal projections, campanulate reddish‐orange corollas and petals 19.5–24.0 mm long. The two new species are endemic to the department of Amazonas. Meriania drakei, from Ecuador and Colombia, and Meriania franciscana, from Ecuador, are recorded for the first time for the Andean forests of the departments of Amazonas and Cajamarca, respectively. We also propose the second step lectotypification for Meriania drakei.

Spinoparabrachial projection neurons form distinct classes in the mouse dorsal horn.

Projection neurons in the spinal dorsal horn relay sensory information to higher brain centres. The activation of these populations is shaped by afferent input from the periphery, descending input from the brain, and input from local interneuron circuits. Much of our recent understanding of dorsal horn circuitry comes from studies in transgenic mice; however, information on projection neurons is still based largely on studies in monkey, cat, and rat. We used viral labelling to identify and record from mouse parabrachial nucleus (PBN) projecting neurons located in the dorsal horn of spinal cord slices. Overall, mouse lamina I spinoparabrachial projection neurons (SPBNs) exhibit many electrophysiological and morphological features that overlap with rat. Unbiased cluster analysis distinguished 4 distinct subpopulations of lamina I SPBNs, based on their electrophysiological properties that may underlie different sensory signalling features in each group. We also provide novel information on SPBNs in the deeper lamina (III-V), which have not been previously studied by patch clamp analysis. These neurons exhibited higher action potential discharge frequencies and received weaker excitatory synaptic input than lamina I SPBNs, suggesting this deeper population produces different sensory codes destined for the PBN. Mouse SPBNs from both regions (laminae I and III-V) were often seen to give off local axon collaterals, and we provide neuroanatomical evidence they contribute to excitatory input to dorsal horn circuits. These data provide novel information to implicate excitatory input from parabrachial projection neuron in dorsal horn circuit activity during processing of nociceptive information, as well as defining deep dorsal horn projection neurons that provide an alternative route by which sensory information can reach the PBN.

Dorsal and ventral mossy cells differ in their axonal projections throughout the dentate gyrus of the mouse hippocampus.

Glutamatergic hilar mossy cells (MCs) have axons that terminate both near and far from their cell body but stay within the DG, making synapses primarily in the molecular layer. The long‐range axons are considered the primary projection, and extend throughout the DG ipsilateral to the soma, and project to the contralateral DG. The specificity of MC axons for the inner molecular layer (IML) has been considered to be a key characteristic of the DG. In the present study, we made the surprising finding that dorsal MC axons are an exception to this rule. We used two mouse lines that allow for Cre‐dependent viral labeling of MCs and their axons: dopamine receptor D2 (Drd2‐Cre) and calcitonin receptor‐like receptor (Crlr‐Cre). A single viral injection into the dorsal DG to label dorsal MCs resulted in labeling of MC axons in both the IML and middle molecular layer (MML). Interestingly, this broad termination of dorsal MC axons occurred throughout the septotemporal DG. In contrast, long‐range axons of ventral MCs terminated in the IML, consistent with the literature. Taken together, these results suggest that dorsal and ventral MCs differ significantly in their axonal projections. Since MC projections in the ML are thought to terminate primarily on GCs, the results suggest a dorsal–ventral difference in MC activation of GCs. The surprising difference in dorsal and ventral MC projections should therefore be considered when evaluating dorsal–ventral differences in DG function.

Phylogeny of the stink bug tribe Chlorocorini (Heteroptera, Pentatomidae) based on DNA and morphological data: the evolution of key phenotypic traits

ABSTRACTPentatomidae is the third largest family of true bugs, comprising over 40 tribes. Few tribes have been studied in a phylogenetic context, and none of them have been examined using molecular data. Moreover, little is known about the evolution of key morphological characters widely used in taxonomic and phylogenetic studies at multiple levels. Here, we conduct a phylogenetic study of the tribe Chlorocorini (Pentatominae) combining 69 morphological characters and five DNA loci. We use the inferred phylogeny to reconstruct the evolution of key morphological characters such as the spined humeral angles of the pronotum, a dorsal projection on the apices of the femora and characters of male genitalia. We provide solid evidence that the tribe as currently recognized is not monophyletic based both on DNA and morphological data. The genera Arvelius Spinola and Eludocoris Thomas were consistently placed outside of the Chlorocorini, whereas the remaining genera were found to form a monophyletic group. We also show that nearly all morphological diagnostic characters for the tribe are homoplastic. The only exception is the development of the hypandrium, which contrary to expectations for genital traits, showed the slowest evolutionary rates. In contrast, the most rapidly evolving trait is the length of the ostiolar ruga, which may be attributed to selection favouring anti‐predatory behaviour and other functions of its associated scent glands. Lastly, we also provide a preliminary glimpse of the main phylogenetic relationships within the Pentatomidae, which indicates that most of the included subfamilies and tribes are not monophyletic. Our results suggest that the current subfamily‐level classification of Pentatomidae is not adequate to reflect its evolutionary history, and we urge for a more complete phylogeny of the family.

More Than Words: Extra-Sylvian Neuroanatomic Networks Support Indirect Speech Act Comprehension and Discourse in Behavioral Variant Frontotemporal Dementia.

Indirect speech acts—responding “I forgot to wear my watch today” to someone who asked for the time—are ubiquitous in daily conversation, but are understudied in current neurobiological models of language. To comprehend an indirect speech act like this one, listeners must not only decode the lexical-semantic content of the utterance, but also make a pragmatic, bridging inference. This inference allows listeners to derive the speaker’s true, intended meaning—in the above dialog, for example, that the speaker cannot provide the time. In the present work, we address this major gap by asking non-aphasic patients with behavioral variant frontotemporal dementia (bvFTD, n = 21) and brain-damaged controls with amnestic mild cognitive impairment (MCI, n = 17) to judge simple question-answer dialogs of the form: “Do you want some cake for dessert?” “I’m on a very strict diet right now,” and relate the results to structural and diffusion MRI. Accuracy and reaction time results demonstrate that subjects with bvFTD, but not MCI, are selectively impaired in indirect relative to direct speech act comprehension, due in part to their social and executive limitations, and performance is related to caregivers’ judgment of communication efficacy. MRI imaging associates the observed impairment in bvFTD to cortical thinning not only in traditional language-associated regions, but also in fronto-parietal regions implicated in social and executive cerebral networks. Finally, diffusion tensor imaging analyses implicate white matter tracts in both dorsal and ventral projection streams, including superior longitudinal fasciculus, frontal aslant, and uncinate fasciculus. These results have strong implications for updated neurobiological models of language, and emphasize a core, language-mediated social disorder in patients with bvFTD.

Morphological ontogeny of Punctoribates astrachanicus (Acari: Oribatida: Punctoribatidae), and comments on Punctoribates Berlese

The morphological ontogeny of Punctoribates astrachanicus Shaldybina, 1973 is described and illustrated. This species was rarely investigated since its description, including its ecological and biological aspects. The adult has fusiform bothridial seta, straight anterior tectum of notogaster, four pairs of saccules, and notogastral setae mostly alveolar, except for short p-series. Tarsus I has a short dorsal projection. Juveniles of this species are light brown, with short and thin prodorsal seta ex, and relatively large humeral organ. The gastronotal setae of larva are of medium size and pointed, in nymphs they are short.

Increased glutamate transmission onto dorsal striatum spiny projection neurons in Pink1 knockout rats

Loss-of-function PTEN Induced Kinase 1 (PINK1) mutations cause early-onset familial Parkinson's disease (PD) with similar clinical and neuropathological characteristics as idiopathic PD. While Pink1 knockout (KO) rats have mitochondrial dysfunction, locomotor deficits, and α-synuclein aggregates in several brain regions such as cerebral cortex, dorsal striatum, and substantia nigra, the functional ramifications on synaptic circuits are unknown. Using whole cell patch clamp recordings, we found a significant increase in the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) onto striatal spiny projection neurons (SPNs) in Pink1 KO rats at ages 4 and 6 months compared to wild-type (WT) littermates, suggesting increased excitability of presynaptic neurons. While sEPSC amplitudes were also increased at 2 and 4 months, no changes were observed in AMPAR/NMDAR ratio or receptor expression. Further analysis revealed increased glutamate release probability and decreased recovery of the synaptic vesicle pool following a train of stimulation in Pink1 KO rats. Ultrastructural analysis revealed increased excitatory and inhibitory synapse number and increased levels of presynaptic α-synuclein, while the number and structure of striatal mitochondria appeared normal. Lastly, we found that Pink1 KO rats have altered striatal dopamine tone, which together with the abnormal α- synuclein distribution and dysfunctional mitochondria, could contribute to the increase in excitatory transmission. Together, these studies show that PINK1 is necessary for normal glutamatergic transmission onto striatal SPNs and reveal possible mechanisms underlying striatal circuit dysfunction in PD.

Coordination of Escape and Spatial Navigation Circuits Orchestrate Versatile Flight from Threats

Naturalistic escape requires versatile context-specific flight, with rapid evaluation of local geometry to identify and use efficient escape routes. It is unknown how spatial navigation and escape circuits are recruited to produce context-specific flight. We show activity in cholecystokinin-expressing hypothalamic dorsal premammillary cells (PMd-cck) is sufficient and necessary for context-specific escape that adapts to each environment’s layout. Contrastingly, numerous other nuclei implicated in flight only induced stereotyped panic-related escape. We reasoned the PMd is unique in its ability to induce context-specific escape because it projects to both escape and spatial navigation nuclei. Indeed, activity in PMd-cck projections to thalamic spatial navigation circuits are only necessary for context-specific escape induced by moderate threats, but not panic-related stereotyped escape caused by perceived asphyxiation. Conversely, the PMd projection to the escape-inducing dorsal periaqueductal gray projection is necessary for all escapes. Thus, PMd-cck controls versatile flight engaging spatial navigation and escape circuits.

Anatomy of the coelomic system in Novocrania anomala (Brachiopoda, Craniiformea) and relationships within brachiopods

Brachiopoda is a relict phylum of marine benthic animals that have not been adequately studied with modern microscopy methods. Microscopic study may provide useful information on the evolution of the brachiopod body plan and brachiopod phylogeny. Understanding the organisation of the coelomic system is important because of its role in body form and compartmentalisation. Most brachiopods are considered to have a bipartite coelomic system; the only known exception is Lingulida, which have a tripartite coelomic system. In the present study, we provide the first complete 3D reconstruction of the coelomic system in the craniide brachiopod Novocrania anomala (Müller, 1776). Its coelomic system consists of the following five main parts, which are entirely separated from each other: 1) a pair of large brachial canals; 2) a complex system of paired small brachial canals and a perioesophageal coelom; 3) frontal coelomic chambers; 4) a main trunk coelom, which includes several semi-detached muscular chambers and mantle sinuses; and 5) a pair of posterior adductors chambers. These results indicate that the coelomic system of N. anomala (and perhaps of other craniides) is complex and cannot be considered to be bipartite or tripartite. The frontmost part of the coelomic system is represented by a pair of frontal chambers, which are considered to be a part of the lophophore but which are derived from dorsal mantle fold extensions and thus may be a part of the trunk coelomic system. A number of similarities were discovered between craniiformean and rhynchonelliformean coelomic systems, including the prominent dorsal projections of the large brachial canals and the morphological features of the perioesophageal coelom. The complex subdivision of the N. anomala trunk coelom is explained by the location and function of muscles, and by the location of several mesenteries.

AKH-FOXO pathway regulates starvation-induced sleep loss through remodeling of the small ventral lateral neuron dorsal projections.

Starvation caused by adverse feeding stresses or food shortages has been reported to result in sleep loss in animals. However, how the starvation signal interacts with the central nervous system is still unknown. Here, the adipokinetic hormone (AKH)—Fork head Box-O (FOXO) pathway is shown to respond to energy change and adjust the sleep of Drosophila through remodeling of the s-LNv (small ventral lateral neurons) dorsal projections. Our results show that starvation prevents flies from going to sleep after the first light-dark transition. The LNvs are required for starvation-induced sleep loss through extension of the pigment dispersing factor (PDF)-containing s-LNv dorsal projections. Further studies reveal that loss of AKH or AKHR (akh receptor) function blocks starvation-induced extension of s-LNv dorsal projections and rescues sleep suppression during food deprivation. FOXO, which has been reported to regulate synapse plasticity of neurons, acts as starvation response factor downstream of AKH, and down regulation of FOXO level considerably alleviates the influence of starvation on s-LNv dorsal projections and sleep. Taking together, our results outline the transduction pathways between starvation signal and sleep, and reveal a novel functional site for sleep regulation.

Morphology of sting apparatus of Chrysidoidea (Hymenoptera, Aculeata)

The main synapomorphy for Aculeata is the sting apparatus, which allows the female to envenom potential prey or hosts. The sting is the modified ovipositor which is not used for laying eggs anymore. Here, we explore the morphology of the sting apparatus within the families of Chrysidoidea. 27 skeletal structures were recognized, including three (dp1vf, dorsal projection of first valvifer; ppa, projection of posterior area of the second valvifer; vl9, ventral lap of tergite 9) that have not been observed previously, and 13 pairs of muscles, including four (superior dorsal T9-2vf (M5); inferior dorsal T9-2vf (M6); postero-lateral T9-2vf/mbr (M9); anterolateral 2vf/bl-2vv/fu (M11)) that have not been observed previously. Very conserved morphological patterns were observed; character support in the sting apparatus was found at the subfamily level, and within three families at the genus level. In addition, we describe the variation within the sting apparatus structures and musculature, propose evolutionary hypotheses about the function and evolution of the structures, and summarize phylogenetic conclusions for Chrysidoidea.

An Early Cretaceous theropod dinosaur from Brazil sheds light on the cranial evolution of the Abelisauridae

Abelisaurid theropods dominated the predator role across Gondwana during the Late Cretaceous. They are characterized by highly reduced forelimbs and one of the most specialized cranial morphologies among carnivorous dinosaurs, exemplified by a broad skull, short rostrum, high occipital region, and highly kinetic intramandibular joint, suggestive of a specialized feeding strategy. Late Cretaceous abelisaurids are known from some remarkably complete taxa with well-preserved skulls. However, little is known about the pattern of character transformation that led to their highly modified condition because there are no well-preserved abelisaurids before the Late Cretaceous. Here we report a basal abelisaurid from the Early Cretaceous of Brazil that preserves a complete skull and reveals an early stage in the cranial evolution of the group. It lacks the specialized temporal and mandibular features characteristic of derived abelisaurids, including the kinetic intramandibular joint and knob-like dorsal projection of the parietals.

Deconstructing the Direct Reciprocal Hippocampal-Anterior Thalamic Pathways for Spatial Learning.

The hippocampus is essential for normal memory but does not act in isolation. The anterior thalamic nuclei may represent one vital partner. Using DREADDs, the behavioral consequences of transiently disrupting anterior thalamic function were examined, followed by inactivation of the dorsal subiculum. Next, the anterograde transport of an adeno-associated virus expressing DREADDs was paired with localized intracerebral infusions of a ligand to target specific input pathways. In this way, the direct projections from the anterior thalamic nuclei to the dorsal hippocampal formation were inhibited, followed by separate inhibition of the dorsal subiculum projections to the anterior thalamic nuclei. To assay spatial working memory, all animals performed a reinforced T-maze alternation task, then a more challenging version that nullifies intramaze cues. Across all four experiments, deficits emerged on the spatial alternation task that precluded the use of intramaze cues. Inhibiting dorsal subiculum projections to the anterior thalamic nuclei produced the severest spatial working memory deficit. This deficit revealed the key contribution of dorsal subiculum projections to the anteromedial and anteroventral thalamic nuclei for the processing of allocentric information, projections not associated with head-direction information. The overall pattern of results provides consistent causal evidence of the two-way functional significance of direct hippocampal-anterior thalamic interactions for spatial processing. At the same time, these findings are consistent with hypotheses that these same, reciprocal interactions underlie the common core symptoms of temporal lobe and diencephalic anterograde amnesia.SIGNIFICANCE STATEMENT It has long been conjectured that the anterior thalamic nuclei might be key partners with the hippocampal formation and that, respectively, they are principally responsible for diencephalic and temporal lobe amnesia. However, direct causal evidence for this functional relationship is lacking. Here, we examined the behavioral consequences of transiently silencing the direct reciprocal interconnections between these two brain regions on tests of spatial learning. Disrupting information flow from the hippocampal formation to the anterior thalamic nuclei and vice versa impaired performance on tests of spatial learning. By revealing the conjoint importance of hippocampal-anterior thalamic pathways, these findings help explain why pathology in either the medial diencephalon or the medial temporal lobes can result in profound anterograde amnesic syndromes.

New specimen of Dinodontosaurus (Therapsida, Anomodontia) from west-central Argentina (Chañares Formation) and a reassessment of the Triassic Dinodontosaurus Assemblage Zone of southern South America

The Chañares Formation is known worldwide for its diverse tetrapod assemblage, including representatives of proterochampsid archosauromorphs, early offshoots of the crocodilian lineage, precursors of the dinosaurian lineage, and dicynodont and cynodont therapsids. The dicynodont Dinodontosaurus, originally described nearly 80 years ago, is the most common dicynodont therapsid in the assemblage. Here we present a new specimen of this taxon, focusing on the basicranium structure using 3D modeling and digital segmentation of the individual bones to provide a novel description of this region of the skull. Among the newly-recognized anatomical structures are a rod-like pila antotica in the prootic, the presence of a dorsal conical projection of the parasphenoid, and the anterior extension of the supraoccipital between the prootic and the parietal. The Chañares tetrapod assemblage was historically correlated with the Dinodontosaurus Assemblage Zone of Southern Brazil, originally due to the presence of this large dicynodont, as well as the cynodont Massetognathus, and more recently by absolute dates of the fossil-bearing strata. Both assemblages are similar in diversity and taxonomy, particularly in their non-mammalian therapsids; however their body-size distributions are very different. These differences in body-size are likely not reflecting a taphonomic bias but local variations in climate that promoted more open landscapes in southern Brazil in contrast to western Argentina, where more humid conditions prevailed during the early Late Triassic.

An Osteo‐Developmental Baseline for Cranial Casque Anatomy of Southern Cassowaries Better Informs Functional Interpretations

Seemingly bizarre cranial ornaments can be found among most major tetrapod groups. The casques (i.e., dorsal skull projections of bone surrounded by keratin sheathing) of modern cassowaries (Casuarius) are perhaps the most enigmatic of modern Aves. Both the biological role(s) and anatomical configuration of this headgear has been debated for the past 150 years, limiting our understanding of the life history of these unique birds as well as the selective conditions under which cranial elaborations appear in archosaurs. Because these structures are poorly understood, it is essential to set an osteo‐developmental foundation from which biomechanical, behavioral, physiological, and functional studies can radiate from. To address the commonly proposed roles of cassowary casques (e.g., ramming, vocalization, thermoregulation, display), we conducted μCT analyses of cranial anatomy in a developmental series of southern cassowaries (C. casuarius). This allowed us to describe details of both external and internal anatomy as well as timings of sutural fusions and inflations of casque elements. We compared the developmental timing of casques to physical, behavioral, and reproductive maturity to determine the plausibility of each function. Our sample (n = 130) indicates the majority of casque growth occurs prior to sexual maturity; although, casque morphology changes substantially throughout adulthood. Deviation from midline is particularly common in the casques of C. casuarius and such asymmetries appear to be primarily dextral. Form does not support functions for either physical ramming or vocalization; however, thermoregulation and display are not refuted by ontogeny nor adult phenotype, necessitating more focused future study.Support or Funding Information2019 New York Institute of Technology College of Osteopathic Medicine (Akinobu Watanabe)2019 Western Interior Paleontological Society ‐ Karl Hirsch Memorial Grant (Todd L. Green)2018 American Association of Anatomists ‐ Visiting Scholarship (Todd L. Green)2017 National Science Foundation ‐ Major Research Instrumentation Grant (Paul M. Gignac)2016 Western Interior Paleontological Society ‐ Karl Hirsch Memorial Grant (Todd L. Green)2015 National Science Foundation ‐ Early‐concept Grant for Exploratory Research (Paul M. Gignac)2015 National Science Foundation ‐ Division of Environmental Biology (Paul M. Gignac)

A new caprellid genus and species (Crustacea: Amphipoda: Caprellidae) from Australia

Abstract A new genus and new species of caprellid, Parapseudaeginella n. gen., and Parapseudaeginella australiensis n. sp., is described from shallow water of Ningaloo Reef, south of Tantabiddy, reef front, Western Australia. The new genus is very similar to Pseudaeginella Mayer, 1890, but can be easily distinguished by the pereonites 6 and 7 being clearly fused (separated in Pseudaeginella) and by the absence of a pair of proximal grasping spines on the propodus of pereopods 5-7 (present in Pseudaeginella). The new species is characterised by acute dorsal projections on head, pereonite 1 and 2, and acute lateral projections near the coxa of gnathopod 2 in males. The new taxon has probably been overlooked in the past due to its tiny size. Further efforts to sample and describe the smaller caprellids is needed to fully understand the global diversity and relationships of caprellids.