Does the frontal sensory organ in adults of the hoplonemertean Quasitetrastemma stimpsoni originate from the larval apical organ?

Background The apical organ is the most prominent neural structure in spiralian larvae. Although it has been thoroughly investigated in larvae of the class Pilidiophora in phylum Nemertea, studies on its structure in other nemertean larvae are limited. Most adult hoplonemertean worms have a frontal organ located in a position corresponding to that of the larval apical organ. The development and sensory function of the frontal organ has not been thoroughly characterized to date. Results The apical organ in the early rudiment stage of Quasitetrastemma stimpsoni larvae consists of an apical plate enclosed by ducts of frontal gland cells and eight apical neurons. The apical plate is abundantly innervated by neurites of apical neurons. During the late rudiment stage, the larval apical organ has external innervation from below by two subapical-plate neurons, along with 11 apical neurons, and its plate contains serotonin-like immunoreactive (5-HT-lir) cells. In the vermicular stage (free-swimming juvenile), the number of apical neurons is reduced, and their processes are resorbed. Serotonin is detected in the apical plate with no visible connection to apical neurons. In adult worms, the frontal organ has a small apical pit with openings for the frontal gland ducts. The organ consists of 8 to 10 densely packed 5-HT-lir cells that form the roundish pit. Conclusions Although the ultrastructure of the Q. stimpsoni larval apical organ closely resembles that of the apical organ of Polycladida larvae, the former differs in the presence of flask-shaped neurons typical of Spiralia. Significant differences in the structure of the apical organs of hoplonemertean and pilidia larvae point to two different paths in the evolutionary transformation of the ancestral apical organ. Ultrastructural and immunoreactive analyses of the apical organ of a hoplonemertean larva in the late rudiment and vermicular stages and the frontal organ of the adult worms identified common morphological and functional features. Thus, we hypothesize that the larval apical organ is modified during morphogenesis to form the adult frontal organ, which fulfills a sensory function in the hoplonemertean worm. This unique developmental trait distinguishes the Hoplonemertea from other nemertean groups.

A new genus and species of freshwater crab (Decapoda, Pseudothelphusidae) from the Tapajós River, a southern tributary of the Amazon River in Brazil

A new genus and species of pseudothelphusid crab of the tribe Kingsleyini Ortmann, 1897, from the Tapajós River, a southern tributary of the Amazon River basin in the state of Pará, Brazil, is described and illustrated.Michaelthelphusa tuerkayigen. et sp. nov. is characterized by the male first gonopod possessing marginal and lateral sutures fused at the distal third of the stem and the merged portion strongly twisted towards the lateral side; an apex transversally expanded along caudal-cephalic axis, with a well-developed, but low, somewhat depressed, apical plate; apical plate with spine-like outgrowth cross overlapping the spine-like projection of the mesial process. Moreover, the relationship of the new genus and species with other pseudothelphusid genera from the Amazon basin is discussed.

Practical fertilization procedure and embryonic development of the New Zealand geoduck clam (Panopea zelandica)

Cultivation of the geoduck Panopea zelandica (Quoy & Gaimard, 1835) requires knowledge on embryonic development to produce spat in hatcheries. This study investigated the development of P. zelandica embryos at 15°C and 35 ppt and the optimal sperm:egg ratios for fertilization under hatchery conditions. Panopea zelandica broodstock were induced to spawn by serotonin injection. Sperm and eggs were collected and fertilization was conducted at sperm:egg ratios of: 50:1, 100:1, 500:1, 1000:1 and 10,000:1 over 40 min. The optimal sperm:egg ratio was <500:1 and the normal embryo yield at 3 and 18 h post-fertilization (hpf) ranged from 83–96%. Panopea zelandica eggs (~80 μm diameter) developed the first and second polar bodies within 15–20 and 50–55 min post-fertilization, respectively. The blastula appeared at ~8 hpf, including the XR and XL cells and the presumptive shell field depression. Gastrulation occurred at 12–18 hpf with organic material apparent at the shell field depression. The mid-stage trochophore, which appeared at around 35 hpf had an apical plate with an apical tuft. The shell field spread to form the periostracum, which expanded and folded into right and left segments covering the late trochophore. The early D-stage veliger appeared at 45 hpf with the soft body being enclosed by two valves and the appearance of the velum. These observations will serve as the basis for future analyses of P. zelandica embryogenesis and for optimization of commercial production of D-veliger larvae.

Empirical and theoretical study of atelostomate (Echinoidea, Echinodermata) plate architecture: using graph analysis to reveal structural constraints

Describing patterns of connectivity among organs is essential for identifying anatomical homologies among taxa. It is also critical for revealing morphogenetic processes and the associated constraints that control the morphological diversification of clades. This is particularly relevant for studies of organisms with skeletons made of discrete elements such as arthropods, vertebrates, and echinoderms. Nonetheless, relatively few studies devoted to morphological disparity have considered connectivity patterns as a level of morphological organization or developed comparative frameworks with proper tools. Here, we analyze connectivity patterns among apical plates in Atelostomata, the most diversified clade among irregular echinoids. The clade comprises approximately 1600 fossil and Recent species (e.g., 25% of post-Paleozoic species of echinoids) and shows high levels of morphological disparity. Plate connectivity patterns were analyzed using tools and statistics of graph theory. To describe and explore the diversity of connectivity patterns among plates, we symbolized each pattern as a graph in which plates are coded as nodes that are connected pairwise by edges. We then generated a comparative framework as a morphospace of connections, in which the disparity of plate patterns observed in nature was mapped and analyzed. Main results show that apical plate patterns are both highly disparate between and within atelostomate groups and limited in number; overall, they also constitute small, compact, and simple structures compared to possible random patterns. Main traits of the evolution of apical plate patterns reveal the existence of strong morphogenetic constraints that are phylogenetically determined. In contrast, evolutionary radiations within atelostomates were accompanied by a clear increase in disparity, suggesting a release of some constraints at the origin of clades.

Encoding regulatory state boundaries in the pregastrular oral ectoderm of the sea urchin embryo

By gastrulation the ectodermal territories of the sea urchin embryo have developed an unexpectedly complex spatial pattern of sharply bounded regulatory states, organized orthogonally with respect to the animal/vegetal and oral/aboral axes of the embryo. Although much is known of the gene regulatory network (GRN) linkages that generate these regulatory states, the principles by which the boundaries between them are positioned and maintained have remained undiscovered. Here we determine the encoded genomic logic responsible for the boundaries of the oral aspect of the embryo that separate endoderm from ectoderm and ectoderm from neurogenic apical plate and that delineate the several further subdivisions into which the oral ectoderm per se is partitioned. Comprehensive regulatory state maps, including all spatially expressed oral ectoderm regulatory genes, were established. The circuitry at each boundary deploys specific repressors of regulatory states across the boundary, identified in this work, plus activation by broadly expressed positive regulators. These network linkages are integrated with previously established interactions on the oral/aboral axis to generate a GRN model encompassing the 2D organization of the regulatory state pattern in the pregastrular oral ectoderm of the embryo.

The Cenozoic gonyaulacacean dinoflagellate generaOperculodiniumWall, 1967 andProtoceratiumBergh, 1881 and their phylogenetic relationships

To clarify the systematic positions of the important gonyaulacacean generaOperculodiniumWall, 1967 emend. Matsuoka et al., 1997 andProtoceratiumBergh, 1881, we present in detail the tabulation of the Oligocene–Pleistocene, thermophilic, cyst-defined speciesOperculodinium bahamenseHeadinHead and Westphal, 1999 emend., and the extant, cosmopolitan, theca-defined speciesProtoceratium reticulatum(Claparède and Lachmann, 1859) Bütschli, 1885. Both species have a sexiform hyposomal tabulation, and L-type (Protoceratium reticulatum) or modified L-type (Operculodinium bahamense) ventral organization.Protoceratium reticulatumhas dextral torsion of the hypotheca, requiring assignation of the genus to the subfamily Cribroperidinioideae Fensome et al., 1993, whereasOperculodinium bahamensehas neutral torsion requiring assignation to the subfamily Leptodinioideae Fensome et al., 1993. The stratigraphic range of this subfamily is now extended upwards to the lower Pleistocene. Paradoxically,Protoceratium reticulatumproduces a cyst whose morphology is circumscribed by the cyst-defined genusOperculodinium, either implying polyphyletic origins for this genus or that combinations of ventral organization and torsion used to subdivide the family Gonyaulacaceae cannot always be applied rigidly. In detail,Operculodinium bahamenseis shown to have an unusual ventral tabulation in which the first apical plate contacts the apical pore complex but not the sulcus. The new term “episert” is proposed to describe this plate relationship, which appears to have evolved independently in several lineages of the suborder Gonyaulacineae.

Deliberations on the External Morphology and Modification of the Labial Segments in the Nepomorpha (Heteroptera: Insecta) with Notes on the Phylogenetic Characteristics

The present study provides new data concerning the external morphology of the labial segments of 46 species from nine Nepomorpha families using the scanning electron microscope. The labial segments are described in detail and images of their structures are presented for the systematic groups. Subsequent segments of the labium (I, II, III, and IV) are shaped similarly in all investigated taxa but carry individual characters in some (sub-)families. Five morphologically distinct forms of the apical plate and five intercalary sclerites have been identified. Additionally, three types of the articulation on the dorsal side between the third and second segments are interpreted as the new characters. The presence of the midventral condyle on the distal edge of the first segment and the third segment has been reanalyzed. New position of the midventral condyle on the proximal edge of the fourth labial segment has been distinguished in several groups. The new set of characters has been estimated from the plesiomorphic taxa of the Nepoidea (Nepidae and Belostomatidae) and subsequently through the more advanced taxa in the relation to the outgroup (Gerromorpha). The evaluation of these characters has revealed twenty-seven new apomorphies for the labium in the Nepomorpha.

Revision of the Mecodema curvidens species group (Coleoptera: Carabidae: Broscini)

The flightless carabid genus Mecodema Blanchard 1843 is restricted to New Zealand and presently contains 64 species. In this study, we examine species in the newly constituted curvidens group (sulcatum and curvidens are synonymised), reducing the Mecodema species groups to seven. They share two synapomorphies (rounded apical lobe of the aedeagus and lack of microsculpture on the vertex of the head) and are distributed in Northland, south along the east coast of the North Island and the northeast portion of the South Island. Adult specimens of the curvidens and sulcatum groups, along with exemplars of the other Mecodema groups (alternans, costellum, ducale, infimate, laterale and spiniferum), and an outgroup Oregus Putzeys 1868 were examined for cladistic analysis using a data matrix composed of a 63 characters and 21 terminal taxa. The analysis resulted in 18 most parsimonious trees. The following new species in the curvidens group are described: M. aoteanoho sp. n., M. haunoho sp. n., M. manaia sp. n., M. parataiko sp. n., M. ponaiti sp. n., and M. tenaki sp. n. Mecodema exitiosus was wrongly sysnonymised under M. occiputale and we propose a new synonymy M. curvidens (=M. exitiosus). We consider the parts of the male genitalia in detail with special attention to the structures of apical plate once everted from the endophallus.

Morfologia Externa de Triatoma carcavalloi Jurberg, Rocha & Lent (Hemiptera: Reduviidae: Triatominae) Através da Microscopia Ótica e Microscopia Eletrônica de Varredura

Resumo. Triatoma carcavalloi Jurberg, Rocha & Lent é uma espécie com distribuição geográfica restrita ao Estado do Rio Grande do Sul, hábitos silvestres, vivendo em simpatria com Triatoma rubrovaria (Blanchard) e Triatoma circummaculata (Stal). Diferenças morfo-estruturais na região cefálica de adultos foram ilustradas. Na análise morfológica das antenas de T. carcavalloi foi verificado em machos e fêmeas a ocorrência de 14 tricobótrias no terceiro e quarto segmento antenal. Na cabeça a presença de 1+1 manchas pós-ocelares. Nos fêmures das pernas de ambos os sexos foi encontrado um par muito pequeno de dentículos subapicais. As fossetas esponjosas foram encontradas somente nos machos, nas tíbias das pernas anteriores e medianas. O estudo do rostro é importante para a caracterização da subfamília Triatominae, assim como o sulco estridulatório e a búcula. A búcula possui borda grossa, superfície granular e forma de “U”. O rostro é similar em ambos os sexos. A placa apical tem forma de diamante na lamela inferior e forma digitiforme na lamela superior. No ápice do rostro duas fendas laterais 1+1 foram observadas. O sulco estridulatório desta espécie tem a forma de "V" e é mais largo nas fêmeas do que nos machos. Esta é a primeira descrição morfológica destas estruturas em adultos de T. carcavalloi usando a microscopia eletrônica de varredura. Estes resultados relacionados aos estudos morfológicos realizados em T. carcavalloi evidenciam a importância destas estruturas para caracterização específica. External Morphology of Triatoma carcavalloi Jurberg, Rocha & Lent (Hemiptera: Reduviidae: Triatominae) by Optical and Scanning Electron Microscopy Abstract. Triatoma carcavalloi Jurberg, Rocha & Lent is specie with restricted geographic distribution to the State of Rio Grande do Sul, rupestrial habits, living currently in simpatry with Triatoma rubrovaria (Blanchard) and Triatoma circummaculata (Stal). Morpho-structural differences in the cephalic region of the adults had also been illustrated. In the morphological analysis of the antennas of T. carcavalloi it was verified the occurrence in both, male and females, more than 14 trichobotrium, in the third and fourth antennal articles. In the head the presence of 1+1 post-ocelares spots. In the legs, a pair of sub-apical dentices in femures of both male and female was found. Spongy fossette had been found only in the males, in the tibias of the previous and medium legs. The study of rostrum is important to the characterization of the subfamily Triatominae, as well as the stridulatory sulcus and buccula. The buccula possess a thick edge, granular surface and “U” shape. The rostrum is similar in both sexes. The apical plate has a diamond shaped inferior lamella and the superior one has a digit form. In the apex of the rostrum two lateral rifts 1+1 are observed. The stridulatory sulcus of these specie is "V" shaped and is more larger in the females than in males. This is the first morphologic description of these structures in the adults of T. carcavalloi using the scanning electronic microscopy. The results related to the morphological studies carried out in T. carcavalloi, showed evidences that some structures are important for the specific characterization.

Morphology, systematics, and evolution of Middle Devonian Ambocoeliidae (Brachiopoda), western New York

The internal morphology of ambocoeliid brachiopods from the Middle Devonian Hamilton Group of western New York indicates a need for several taxonomic revisions. “Ambocoelia” praeumbona is transferred to Emanuella. “Ambocoelia” spinosa and “A.” nana represent Crurispina n. gen. Specimens of species belonging to Crurispina have moderately well developed crural plates, and, accordingly, they are assigned to the subfamily Rhynchospiriferinae. Crural plates are small and obscure but clearly present in Ambocoelia umbonata, the type species of Ambocoelia. Thus, the diagnosis of the subfamily Ambocoeliinae is emended to include species with tiny crural plates.Ambocoeliid specimens from the Levanna Shale Member of the Skaneateles Formation, formerly referred to Echinocoelia, reveal several elaborate features in the pedicle valve, including an apical plate and a hollow tube supported by a median septum. These specimens represent a new genus and species, Mucroclipeus eliei. The homeomorphy found in the shape and size of these ambocoeliids may be the result of paedomorphosis. Additionally, their pattern of occurrence and minute size suggest that they attained their paedomorphic state through progenesis. The taxa Ambocoelia tuberculata n. sp., Crurispina n. gen., and Mucroclipeus eliei n. gen. and sp. are established.