Showing papers in "Acta Zoologica in 2007"
107 citations
TL;DR: Fusion of cervical and caudal neural arches and centra, complete ossification of thoracic ribs and ilium, possible co-ossification of tibia and fibula, fused pubes, complete meta-and acropodial elements, together with small portions of unossified epiphyses of long bones suggest an advanced precociality of these embryos.
Abstract: Exceptionally complete, in ovo dinosaur embryos from the Upper Cretaceous of China are analysed. Ossification patterns of these embryos suggest that they died during the final third of their development. The therizinosauroid identity of the embryos follows from: (1) an edentulous premaxilla with a sharp downturned edge; (2) dentary with a lateral shelf; (3) teeth with fan-shaped crowns, with a few marginal cusps; (4) humerus with a massive deltopectoral crest extending proximally, with a pointed proximomedial tuberosity; (5) ilium with an expanded and hooked preacetabular process; (6) strongly curved hypertrophied manual unguals tapering to sharp points. These embryos are closest to two Chinese therizinosauroids, Neimongosaurus yangi Zhang et al. 2001 and Erliansaurus bellamanus Xu et al. 2002. An elongated narial opening, reduced basipterygoid process, low cervical neural spines, a transversely narrow pubic apron, and a pubic foot expanded anteriorly are found in these embryos and are synapomorphies uniting the Therizinosauroidea and the Oviraptorosauria. Fusion of cervical and caudal neural arches and centra, complete ossification of thoracic ribs and ilium, possible co-ossification of tibia and fibula, fused pubes, complete meta-and acropodial elements, together with small portions of unossified epiphyses of long bones suggest an advanced precociality of these embryos.
73 citations
58 citations
TL;DR: The development of the early anlagen of the circular body wall muscles does not show the anterior‐ posterior mode of formation that is typical for annelids, thus strengthening the hypothesis of a non-segmented ancestry of Mollusca.
Abstract: Nielsen, C., Haszprunar, G., Ruthensteiner, B. and Wanninger A. 2007. Early development of the aplacophoran mollusc Chaetoderma . — Acta Zoologica (Stockholm) 88 : 231‐247 The early development of the trochophore larva of the aplacophoran Chaetoderma nitidulum (Mollusca: Caudofoveata = Chaetodermomorpha) is described using scanning and transmission electron microscopy and using fluorescence staining and confocal laser scanning microscopy of the muscle system. The most important features include the presence of a prototroch and a telotroch, serially arranged glandular cells (spiculoblasts) at the dorsal mantle, the occurrence of a ventral suture as a possible remnant of a former foot sole, and the presence of a pair of protonephridia. The development of the early anlagen of the circular body wall muscles does not show the anterior‐ posterior mode of formation that is typical for annelids, thus strengthening the hypothesis of a non-segmented ancestry of Mollusca.
54 citations
TL;DR: Many aspects of spermatophore formation in C. quadricarinatus differ from those of other Astacida, and the applied aspects of this study for aquaculture purposes are discussed.
Abstract: Lopez Greco, L.S., Vazquez, F. and Rodriguez, E.M. 2007. Sperm production and spermatophore formation in the freshwater ‘red claw’ crayfish Cherax quadricarinatus (Von Martens 1898) (Decapoda, Parastacidae). — Acta Zoologica (Stockholm) 88 : 223‐229. The morphology of the male reproductive system was studied in Cherax quadricarinatus . The testes and vasa deferentia were dissected, fixed, cut and stained. Testes appear as two parallel and opalescent strands; they present many testicular lobes, each lobe containing cells in the same stage of the spermatogenic cycle. A vas deferens arises from the external side of each testis and three parts were clearly distinguished: proximal vas deferens (PVD), middle vas deferens (MVD) and distal vas deferens (DVD). The PVD is opalescent and highly convoluted, the MVD is pale white in colour and convoluted, but wider in diameter than the PVD, while the DVD shows the widest diameter, is straight and is white in colour. A single-layered epithelium is recognized in the vas deferens; with cylindrical cells in the PVD and cuboid cells in the MVD and DVD. The formation of the spermatophore starts at the PVD, while the secondary layer of the spermatophore seems to be added at the MVD. At the DVD, the highly coiled spermatophore is surrounded by the periodic acid Schiff-positive sticky components of the secondary layer. Many aspects of spermatophore formation in C. quadricarinatus differ from those of other Astacida. The applied aspects of this study for aquaculture purposes are discussed.
54 citations
TL;DR: Production of male gametes was continuous throughout the study period, indicating that males of this species are physiologically capable of reproducing all year long.
Abstract: Castilho, G G, Ostrensky, A, Pie, M R and Boeger, W A 2007 Morphology of the male reproductive system of the mangrove land crab Ucides cordatus (L) (Crustacea, Brachyura, Ocypodidae) —Acta Zoologica (Stockholm) 88: 000–000
This study provides a detailed description of the macro- and microscopic anatomy of the male reproductive system and the spermatogenesis of the mangrove land crab, Ucides cordatus A total of 64 adult males were collected between December 2002 and February 2005 in mangroves of the Baia de Antonina, State of Parana, Southern Brazil (25°25′08″S, 48°42′33″W) The reproductive system of this species is composed of the following paired symmetrical structures: testes, vasa deferentia (distal, medial and proximal portions), ejaculatory ducts and penises During spermatogenesis, which takes place in the testes, the following developmental stages are observed: primary and secondary spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoids Production of male gametes was continuous throughout the study period, indicating that males of this species are physiologically capable of reproducing all year long
49 citations
TL;DR: The present results and previous findings, in particular the chitinous, non-moulted cuticle, the sinus circulatory system, and a number of neural features shared by Kamptozoa and Mollusca, provide substantial evidence for a direct sister-group relationship between these phyla.
Abstract: The creeping larva of the kamptozoan (entoproct) Loxosomella murmanica was investigated using transmission electron microscopy. The late larva exhibits a prominent apical organ connected to the ‘cerebral’ commissure of large cerebral ganglia, which supply the paired frontal organ. From the cerebral ganglia two paired nerve cords project backwards, closely resembling the tetraneuralian pattern of basal molluscs. In addition, a neural ring supplying the prototroch is present. The epidermis is composed of myoepithelial cells. Dorsally its cuticle is covered by granules of unknown composition. The prototroch consists of two ciliary rings; a downstream collecting system is not present. Although there is a one-way gut with a lumen throughout, the larva obviously does not feed. A single pair of protonephridia is present. The foot sole shares distinct similarities with basic molluscs, particularly with those of the aplacophoran Solenogastres: The anterior part shows a huge, subepidermal pedal gland and several bundles of cirri consisting of compound cilia. The posterior part is ciliated with intraepithelial mucous cells interspersed. The dorsoventral muscle fibres show the mollusc-like ventral intercrossing. The present results and previous findings, in particular the chitinous, non-moulted cuticle, the sinus circulatory system, and a number of neural features shared by Kamptozoa and Mollusca, provide substantial evidence for a direct sister-group relationship between these phyla. In addition, the basal position of the Solenogastres (Neomeniomorpha) within the Mollusca is corroborated.
44 citations
TL;DR: This ultrastructural study on the regenerating feathers of quail describes the cellular organization of the barb ridges responsible for the ramification of adult feathers and speculation on the evolution and diversification of feathers is presented.
Abstract: This ultrastructural study on the regenerating feathers of quail describes the cellular organization of the barb ridges responsible for the ramification of adult feathers. Bilateral symmetry of the barb ridges determines the organization of feather cells into feather branching. The length of the barb ridges, derived from the number of cells associated to form the barbule plates, determines the length of the barbule branching. Long chains of barb cells form long barbs that branch from the rachis with an increase of feather size. Supportive cells function as spacers between the barbule cells. New cells derive from stem cells localized in the collar region of the feather follicle, as indicated from the re-organization of collar cells into barb ridges (a morphogenetic process inherited from that of embryonic feathers), production of an embryonic type of keratin (feather keratin), permanence of periderm granules (typical embryonic organelles) in barb vane ridge cells. Variations in the process of barb ridge morphogenesis allow the fusion of ridges into a rachis. The differentiation of hooklets contributes to the origin of planar feathers. Separation between rachis and merging barb ridges is by supportive cells, derived from the marginal plates of the barb ridges. Speculations on the evolution and diversification of feathers are presented.
34 citations
TL;DR: The aim of this study was to characterize the morphology of the reproductive system and the type of sexuality of Parastacus defossus, an intersexed, freshwater crayfish that occurs in the southeast of Brazil and Uruguay.
Abstract: The aim of this study was to characterize the morphology of the reproductive system and the type of sexuality of Parastacus defossus, an intersexed, freshwater crayfish that occurs in the southeast of Brazil and Uruguay. The specimens were examined for the appearance of the genital pores, and the gonads were macroscopically analysed by size and colour. The histology of some gonads was examined. Males and females have two pairs of genital ducts: one anterior (oviduct) and one posterior (vas deferens). The gonads are located in the thorax and consist of one pair of lobules. Through macroscopic and histological analyses of the female gonads, six stages of ovarian development could be distinguished. The histological description of the testis was made only from adult males. Through analyses of the genital pores and gonads, three sexual forms were distinguished in P. defossus: intersexed females (246), intersexed males (259), and individuals with an ootestis (7). Individuals with an ootestis had a gonad that produced male and female reproductive cells simultaneously. Parastacus defossus can be classified as a partially protandric hermaphrodite species.
34 citations
TL;DR: Cloacal features provide interesting information that is useful as a source of morphological characters for phylogenetic studies in Squamata and contributes evidence that defines the relationships within Scleroglossa.
Abstract: Sanchez-Martinez, P.M., Ramirez-Pinilla, M.P. and Miranda-Esquivel, D.R. 2007. Comparative histology of the vaginal‐cloacal region in Squamata and its phylogenetic implications. — Acta Zoologica (Stockholm) 88 : 289‐307 We described the histology and morphology of the vaginal‐cloacal region in 18 species from 12 Squamata families. This comparative study revealed a wide variation in the cloacal morphology. Fifteen morphological characters were considered to be primary homology hypotheses and were optimized over the topology derived from the parsimony analysis of the available soft morphological evidence, including the characters described in this study. The synapomorphies optimized for Squamata are bifid urodaeum, common urodaeal cavity with similar histological features of the urodaeal horns, and presence of glands in the anterior urodaeum; for Scleroglossa the synapomorphy is the lateral position of the vaginal intrusion into the anterior urodaeal chamber, for Nyctisaura + Scincomorpha the synapomorphy is the presence of a bifid posterior urodaeum; and for Xantusidae + Annulata it is the presence of simple glands in the anterior urodaeum. The central position of the vaginal intrusion into the urodaeal chamber and the intraepithelial position of the glandular unit in the anterior urodaeum behave as autapomorphies for Iguanidae. This study contributes evidence that defines the relationships within Scleroglossa. Cloacal features provide interesting information that is useful as a source of morphological characters for phylogenetic studies in Squamata.
TL;DR: The morphology of Magadictyon cf.
Abstract: Liu, J., Shu, D., Han, J., Zhang, Z. and Zhang, X. 2007. Morpho-anatomy of the lobopod Magadictyon cf. haikouensis from the Early Cambrian Chengjiang Lagerstatte, South China. — Acta Zoologica (Stockholm) 88 : 279‐288 Magadictyon haikouensis (Luo and Hu, 1999) from the Early Cambrian Chengjiang Lagerstatte, an incomplete specimen of a large lobopod with strong appendages, has been regarded as related to the lobopods Microdictyon and Onychodictyon . Newly discovered complete specimens of Magadictyon cf. haikouensis (found by the Early Life Institute field team) show that the taxon, in addition to its strong appendages with appendicules, also had a head bearing similar caecum-like structures to those of the arthropod Naraoia and Chelicerate, ‘ Peytoia ’-like mouthparts and frontal appendages. Because of their similarity, the caecum-like structures of Magadictyon cf. haikouensis are considered to be homologous with those of stem-group arthropods. The ‘ Peytoia ’-like mouthparts and the frontal appendages are similar to those of the AOPK ( Anomalocaris‐Opabinia‐Pambdelurion‐Kerygmachela ) group. In addition, the appendages with appendicules show that Magadictyon cf. haikouensis is closely related to Onychodictyon . Therefore, Magadictyon cf. haikouensis is regarded here as a rare transitional form between lobopods and arthropods. Besides, together with other lobopods, the morphology of Magadictyon cf. haikouensis demonstrates that the Cambrian lobopods appear to have been diverse and not particularly closely related to one another, and do not seem to represent a monophyletic clade.
TL;DR: The inner/middle mantle fold of A. noae, possibly representative of simpler, more primitive conditions, may have differentiated into distinct folds in other recent representatives of the Bivalvia.
Abstract: In the Croatian Adriatic, Arca noae occurs from the low intertidal to a depth of 60 m; it can live for > 15 years and is either solitary or forms byssally attached clumps with Modiolus barbatus. The shell is anteriorly foreshortened and posteriorly elongate. The major inhalant flow is from the posterior although a remnant anterior stream is retained. There are no anterior but huge posterior byssal retractor muscles and both anterior and posterior pedal retractors. The ctenidia are of Type B(1a) and the ctenidial–labial palp junction is Category 3. The ctenidia collect, filter and undertake the primary sorting of potential food in the inhalant water. The labial palps are small with simple re-sorting tracks on the ridges of their inner surfaces. The ciliary currents of the mantle cavity appear largely concerned with the rejection of particulate material. The mantle margin comprises an outer and an (either) inner or middle fold. The outer fold is divided into outer and inner components that secrete the shell and are photo-sensory, respectively. The latter bears a large number of pallial eyes, especially posteriorly. The inner/middle mantle fold of A. noae, possibly representative of simpler, more primitive conditions, may have differentiated into distinct folds in other recent representatives of the Bivalvia.
TL;DR: It is proposed that both manipulation by the female and hydration are the mechanisms involved in the release of the spermatozoa from the spermatophore.
Abstract: Lopez Greco, L.S. and Lo Nostro, F.L. 2007. Structural changes in the spermatophore of the freshwater ‘red claw’ crayfish Cherax quadricarinatus (Von Martens, 1898) (Decapoda, Parastacidae). —Acta Zoologica (Stockholm) 88: 000–000
The structure of the spermatophore was studied in Cherax quadricarinatus. Pieces of the distal vas deferens and transferred spermatophore from the females were fixed, cut and stained. Within the distal vas deferens, the primary layer and the secondary layer of the spermatophore were distinguishable. In the latter, two components were detected: cytoplasmic droplets and a homogeneous matrix. During the first 10 minutes post-extrusion the cytoplasmic droplets drastically changed from looking like ‘empty droplets’; at this time the spermatophore changed from a liquid stage to a sticky one. One hour after extrusion the spermatophore began to harden and within the first 24–48 h post-mating it was a solid and intense white structure tightly attached to the female; after 72 h it acquired a softer aspect, completely dehiscing between 96 and 120 h post-mating. Histologically, the primary layer maintained its integrity surrounding the spermatozoa while the secondary layer lost the cytoplasmic droplets. The spermatophore began to hydrate between 24 and 48 h and by 72–96 h many sections of the sperm cord began to coalesce. From 48 h post-mating some fissures appeared within the matrix that enlarged between 72 and 120 h. We propose that both manipulation by the female and hydration are the mechanisms involved in the release of the spermatozoa from the spermatophore.
TL;DR: Comparative anatomical and ontogenetic data show many similarities between the head organization of chelicerates and that of mandibulates, and lead to conclusions that contradict some of the hypotheses deduced from recent studies on developmental biology, but favour more traditional views.
Abstract: The present paper is a critical review of data and hypotheses on the head segmental composition in chelicerates and in extinct non-mandibulate arthropods. It successively takes into account data from morphology and embryology, from the structure of the nervous system, from palaeontology and from developmental genetics. Discussion focuses on possible homologies between the head segments and appendages in arachnomorphs and those in mandibulates. The comparative anatomical and ontogenetic data, especially those concerning the central nervous system, its connections with the stomatogastric system, and head innervation, show many similarities between the head organization of chelicerates and that of mandibulates, and lead to conclusions that contradict some of the hypotheses deduced from recent studies on developmental biology, but favour more traditional views. In particular they support the presence of a deutocerebral segment in the head region of the ground pattern of arthropods and its loss in all extant chelicerates. They also support the homology of the cheliceral ganglia with the tritocerebral ganglia of mandibulates. The possible existence of a precheliceral segment and of a presegmental acron remains open to question.
TL;DR: The unusual morphology of the Eurasian bullfinch spermatozoon, resembling that of a spermatid, is the result of the progressive suppression of the final stages of spermiogenesis and is associated with the likelihood that sperm competition is infrequent in this species.
Abstract: Birkhead, T.R., Giusti, F., Immler, S., Jamieson, B.G.M. 2007. Ultrastructure of the unusual spermatozoon of the Eurasian bullfinch ( Pyrrhula pyrrhula ). — Acta Zoologica (Stockholm) 88 : 119-128 The Eurasian bullfinch spermatozoon differs from typical passeridan spermatozoa in several major respects. The mature acrosome consists of a concavo-convex vesicle differing from the typical passeridan acrosome, which is a helical structure, is usually longer than the nucleus and has a prominent helical keel. The nucleus differs from that of other oscines in not showing a twisted cylindrical form, in being shorter, and in tending to be an elongate ellipsoid in shape. The chromatin often appears in an uncondensed form reminiscent of a spermatid and consists of discrete fascicles. A small proportion of the mature sperm population however, is characterized by marked chromatin condensation. The midpiece comprises a small group of mitochondria clustered around the nuclear-axonemal junction in contrast to the single, long mitochondrion wound helically around the axoneme that is found in typical Passerida. The presence of a proximal centriole (in addition to the distal one) is a notable difference from all other oscine passerines. We suggest that the unusual morphology of the Eurasian bullfinch spermatozoon, resembling that of a spermatid, is the result of the progressive suppression of the final stages of spermiogenesis and is associated with the likelihood that sperm competition is infrequent in this species.
TL;DR: Observations show that lizard claws derive from the modification of the last scale or scales of the digit, probably under the influence of the growing terminal phalanx.
Abstract: Morphogenesis of claws in the lizard Lampropholis guichenoti has been studied by light and electron microscopy. Claws originate from a thickening of the epidermis covering the tips of digits under which mesenchymal cells aggregate. Mesenchymal cells are in continuity with perichondrial cells of the last phalange, and are connected to the epidermis through numerous cell bridges that cross an incomplete basement membrane. The dense lamella is completed in non-apical regions of the digit where also collagen fibrils increase. The dorsal side of the developing claw derives from the growth of the outer scale surface of the last scale of the digit. The corneous layer, made of beta-keratin cells, curves downward by the tip of the growing claw. The epidermis of the ventral side of the claw contains keratohyaline-like granules and alpha-keratinocytes like an inner scale surface. The thickness of the horny layer increases in the elongating unguis while a thinner and softer corneous layer remains in the subunguis. These observations show that lizard claws derive from the modification of the last scale or scales of the digit, probably under the influence of the growing terminal phalanx. Some hypotheses on the evolution of claws in reptiles are presented.
TL;DR: Results indicate that skull shape in this species changes little during postnatal growth relative to the only cryptodire taxa for which comparable datasets are available, which results in the paedomorphic retention of a largely juvenile appearance in the adult form of P. texana.
Abstract: Bever, G.S. 2007. Comparative growth in the postnatal skull of the extant North American turtle Pseudemys texana (Testudinoidea: Emydidae). —Acta Zoologica (Stockholm) 88: 000–000
Postnatal growth is one of the many aspects of developmental morphology that remains distinctly understudied in reptiles. Variation and ontogenetic scaling within the skull of the extant emydid turtle, Pseudemys texana is described based on 25 continuous characters. Results indicate that skull shape in this species changes little during postnatal growth relative to the only cryptodire taxa for which comparable datasets are available (Apalone ferox and Sternotherus odoratus). This relative lack of change results in the paedomorphic retention of a largely juvenile appearance in the adult form of P. texana. The skulls of males and females, despite the presence of distinct sexual dimorphism in size, grow with similar scaling patterns, and the few observed differences appear to reflect alteration of the male growth trajectory. Comparisons with A. ferox and S. odoratus reveal a number of similarities and differences that are here interpreted within a phylogenetic context. These preliminary hypotheses constitute predictive statements that phylogenetically bracket the majority of extant cryptodire species and provide baseline comparative data that are necessary for the future recognition of apomorphic transformations. Plasticity of ontogenetic scaling as a response to the homeostatic needs and behaviour of individuals commonly is evoked as a limitation of ontogenetic scaling as a means to inform phylogenetic studies. These evocations are largely unfounded considering that variability itself can evolve and thus be phylogenetically informative.
TL;DR: It is hypothesized that this population has the capacity to copulate and deposit another brood even before the release of the larvae from the previous one, intensifying the reproductive effort of these hermit crabs as a strategy of adaptation in a region considered the northern limit of the geographical distribution of this species.
Abstract: The aim of the present work was to characterize the egg production of Loxopagurus loxochelis. A total of 71 ovigerous females were obtained, 28% of which were simultaneously incubating eggs at different developmental stages. This phenomenon can be the result of incomplete fertilization, or may represent a rapid gonadal cycle by this species in this area, which is, to our understanding, the best explanation of this phenomenon. Egg volume decreased 25.6% during the incubation period. The reproductive output based on dry and wet weight was 6.8 and 19.3%, respectively. Water was the prevailing component of the eggs, representing 86.0% of the total weight at initial stage, increasing to 95.1% at the final stage. Ash content increased at the same time as a decrease in the organic content occurred, indicating the consumption of yolk and absorption of salts from the water medium. In conclusion, we hypothesized that this population has the capacity to copulate and deposit another brood even before the release of the larvae from the previous one, intensifying the reproductive effort of these hermit crabs as a strategy of adaptation in a region considered the northern limit of the geographical distribution of this species.
TL;DR: In this article, the carpal and tarsal anatomy of chelid and pelomedusoid species was studied based on the observation of dry skeletons of adult specimens representing 25 species in 15 genera and on data taken from the literature.
Abstract: Carpal and tarsal anatomy was documented based on the observation of dry skeletons of adult specimens representing 25 species in 15 genera and on data taken from the literature. In addition, histological sections and cleared and double-stained autopodia of recently hatched and juvenile specimens representing seven chelid and pelomedusoid species were studied. There is much more morphological diversity in the manus than in the pes. Variation in autopodial skeletons includes: the astragalus and calcaneum are either separated or fused; fusion of distal carpals 3–4−5 or just 4–5; number of centralia in the carpus; and presence/absence of a pisiform and of an accessory radial element. The widespread and probably basal phalangeal formula for Pleurodira is 2.3.3.3.3. Deviations are Pelomedusa subrufa, exhibiting a reduction to 2.2.2.2.2, Pelusios spp. with one phalanx less in digit I and for one species in digit V as well, and Acanthochelys pallidipectoris with an additional phalanx in the fourth finger. Six discrete characters itemizing some of the morphological variation observed were plotted on a composite pleurodire phylogeny, revealing not only homoplastic patterns but also the utility of some characters in supporting the monophyly of several clades. The pisiform is the last carpal element to ossify in Chelus fimbriatus. We hypothesize that the so-called fifth hooked metatarsal represents the fusion of distal tarsal 5 with metatarsal V. The accessory radial element that was occasionally present in the turtles examined may represent an atavism of the otherwise lost radiale of turtles.
TL;DR: New morphological characters that are specific to Pseudomyrmex, are valuable synapomorphies of the genus and can be used in taxonomic characterization of the Pseudmyrmecinae subfamily and in phylogenetic analyses in Formicidae family.
Abstract: Moya, J., Mancini, K., Lino-Neto, J., Delabie, J. and Dolder, H. 2007. Sperm ultrastructure of five species of the Neotropical ant genus Pseudomyrmex (Hymenoptera: Formicidae). — Acta Zoologica (Stockholm) 88 : 181‐187 The seminal vesicles of adult males of five species of Pseudomyrmex were prepared for light and transmission electron microscopy. The Pseudomyrmex spermatozoa are long and slender with similar morphology. The head region has an acrosome and a nucleus. In all the studied species, two morphologically distinct types of acrosomal vesicles were observed, a long structure, as observed in all known ants, and a pear-shaped one, never before observed in ants. The nucleus is elongated and both condensed and loose chromatin are present. The flagellum has an axoneme, a centriolar adjunct, two mitochondrial derivatives and two accessory bodies. The centriolar, the mitochondrial derivatives and the accessory bodies are similar to observations in most ant species that have been studied. The axoneme presents an uncommon 9 + 9 + 1 microtubule arrangement and the central microtubule has 13 protofilaments. The acrosomal dimorphism and the different levels of chromatin organization are exclusive characteristics of Pseudomyrmex . Furthermore, the 9 + 9 + 1 microtubule arrangement is different from all Hymenoptera, as well as from most insects, which present a 9 + 9 + 2 arrangement. These new morphological characters that are specific to Pseudomyrmex , are valuable synapomorphies of the genus and can be used in taxonomic characterization of the Pseudomyrmecinae subfamily and in phylogenetic analyses in Formicidae family.
TL;DR: Spermiophagy by the efferent ductules is reported here for the first time in a reptile.
Abstract: Light microscopy histology of efferent ductules and the ultrastructural organization of their epithelium were studied in the fan-throated lizard Sitana ponticeriana Cuvier. The ductules of this lizard are extra-testicular and arise from an extra-testicular rete testis. A major portion of the ductules is intra-epididymal and occupies the cephalic end of the epididymis. The ductules differentiate histologically into proximal and distal portions. The epithelium is formed of two major tall columnar cell types, the non-ciliated and ciliated, and one minor cell type, the basal cells. Dark cells were also identified. The non-ciliated cells possess microvilli towards the luminal end, tubular coated pits at the bases of the microvilli, coated vesicles in the apical cytoplasm and multivesicular bodies, lysosomes and mitochondria in the supranuclear and perinuclear cytoplasm, which reflects their role in the uptake of the material they are processing. These cells also participate in spermiophagy. The ciliated cells reflect their role in mixing the luminal content and/or its transport to the distal parts of the male tract. The lizard efferent ductules share many features in common with those of mammals and a crocodile and several other features with birds and a turtle. Spermiophagy by the efferent ductules is reported here for the first time in a reptile.
TL;DR: In two species of Heterodontus, the first scales to develop form two opposing rows along the caudal fin axis on both the left and right sides of the fin, which contrast with previous suggestions that chondrichthyan scale development is entirely random.
Abstract: In two species of Heterodontus, H. portusjacksoni and H. galeatus, the first scales to develop form two opposing rows along the caudal fin axis on both the left and right sides of the fin. The opposing rows originate from an initial scale located on either side of the posterior tip of the caudal fin, with subsequent scales erupting in a posterior to anterior direction along the tail axis. These scale rows may strengthen tail movements, providing aeration in the egg case, but are lost later in ontogeny. Development of subsequent body scales shows a more irregular origin and arrangement, from anterior to posterior, to cover the dorsal and ventral lobes of the caudal fin. Although the early developmental pattern of the scale associated with the Heterodontus caudal fin has not been previously described, several chondrichthyan taxa, including chimeroids, likewise possess ordered rows of flank scales early in ontogeny that are subsequently lost. These ordered scales contrast with previous suggestions that chondrichthyan scale development is entirely random. Instead, regulated and sequential development of scales may be a plesiomorphic character for both chondrichthyans and osteichthyans, with the less organized arrangement in later ontogenetic stages being a derived condition within Chondrichthyes.
TL;DR: Invertebrate and ciliate protozoan epibionts of velvet swimming crabs collected near Millport (Scotland) were analysed and indicated a significant differential distribution of eachEpibiont species on the anatomical units of the crab.
Abstract: Invertebrate and ciliate protozoan epibionts of velvet swimming crabs collected near Millport (Scotland) were analysed. The ecdysis peak for male crabs was at the time of collection while that for female crabs was 2 months later. The epibionts were: the polychaetes Pomatoceros triqueter and Hydroides norvegica, the cirriped Balanus crenatus, the entoproct Barentsia matsushimana, the hydroids Leuckartiara sp. and Clytia sp., and the ciliate protozoans Ephelota plana, Ephelota gemmipara, Chilodochona quennerstedti and Cothurnia longipes. The polychaetes, cirripeds, entoprocts and hydroids, all of them with comparatively larger size, were distributed on the carapace, ventral surface of the cephalothorax and the pereiopods; meanwhile the protozoans, with smaller size, were attached also on pleopods, antennae, eyes and buccal appendages. Chilodochona quennerstedti was the epibiont most abundant on the crab, followed by Ephelota plana. Cothurnia longipes was, in contrast, the least abundant epibiont, followed by Barentsia matsushimana. The anatomical unit most colonized was the left third maxilliped, followed by the left first maxilliped and the ventral surface. The less colonized anatomical units were the left antenna and the ocular orbits. Epibionts on this crab have not been described before. Statistical analyses of the epibiont distribution on the crab were carried out. There were significant correlations between right and left appendages in 66.67% of the cases. Males and females differed significantly with respect to the distribution of epibionts on their anatomical units. The comparison analysis indicated a significant differential distribution of each epibiont species on the anatomical units of the crab. Principal component analysis grouped the epibiont species according to their colonization pattern in three clusters: (1) Ephelota plana, Ephelota gemmipara and Chilodochona quennerstedti; (2) Leuckartiara sp., Clytia sp., Barentsia matsushimana and Cothurnia longipes; and (3) Pomatoceros triqueter, Balanus crenatus and Hydroides norvegica. The hierarchical cluster analysis grouped the anatomical units of the crab in relation to their colonization in five clusters.
TL;DR: The morphology of the MTG of Dolycoris baccarum (Linnaeus 1758) was studied and the biological functions of the glandular secretions were discussed and the compounds identified were investigated.
Abstract: One of the general defining characters of the Heteroptera is the presence of metathoracic scent glands (MTG). Using scanning electron microscopy, the morphology of the MTG of Dolycoris baccarum (Linnaeus 1758) (Heteroptera: Pentatomidae) was studied. The MTG belong to the diastomian type. The two glandular pores located between the mesothoracic and metathoracic coxae are associated with ‘mushroom-like’ structures. The MTG are composed of a reservoir and a pair of lateral glands is connected to the reservoir by a duct. A groove-like structure extends downwards from the ostiole. While this structure is long and wide, its ostiole is oval. Extracts of the volatile fractions from male and female MTG secretions were analysed by capillary gas chromatography–mass spectrometry (GC-MS) and exhibited a typical pentatomid composition. Seventeen chemical compounds were detected in female secretions, whereas 13 chemical compounds were detected in the male secretions. Most chemical compounds were similar between the sexes but were different in their quantities. In this regard, the compounds identified were investigated and the biological functions of the glandular secretions were discussed. In the analyses of the MTG of females of D. baccarum, tridecane (50.97%) was a major odour component and (Z,Z)-4,16-octadecadien-1-ol acetate (0.02%) was a minor odour component. In males, tridecane (50.80%) was a major odour component and 1,2-benzenedicarboxylic acid (0.02%) was a minor odour component.
TL;DR: The results re-confirm that to understand the full dynamics of the evolution of development, studies need to implement comparative embryological approaches, and include phylogenetically relatively closely related taxa.
Abstract: We describe the development of the cranial neural crest cell streams relative to embryonic events such as neural tube formation and somite appearance in two Eurasian frog species belonging to the Ranidae, Rana temporaria and Sylvirana nigrovittata, and demonstrate developmental heterochronies. The mandibular stream appeared well developed in R. temporaria at a time when the embryo was still spherical, the neural folds were elevated, and the neural plate was wide open, thus earlier than known from any frog species so far. The appearance of the second stream and its division into hyoid and branchial portions was clearly accelerated in R. temporaria relative to other embryonic events when compared to S. nigrovittata. For example, in R. temporaria, the hyoid and branchial portions of the cranial neural crest cell streams were separated before the neural folds had started to fuse, whereas in S. nigrovittata this event took place only after the neural folds had fused completely. Such ostentatious heterochronies related to the characters used herein have formerly only been reported from comparisons between species belonging to different higher taxa. Our results re-confirm that to understand the full dynamics of the evolution of development, studies need to implement comparative embryological approaches, and include phylogenetically relatively closely related taxa.
TL;DR: Polymerase chain reaction-RAPD markers revealed strikingly different molecular profiles between coastal and continental samples and indications of a high degree of genetic variation in Mimagoniates microlepis.
Abstract: Chromosome and random amplified polymorphic DNA (RAPD) markers of samples of Mimagoniates microlepis were studied to test the hypothesis that a vicariant event occurred as the result of the orogeny of the coastal mountain range (Serra do Mar; southeastern and southern Brazil). Conventional karyotypes and nucleolar organizer region (Ag-NOR) phenotypes of two samples of M. microlepis from the headwaters of the Iguacu River (southern Brazil) were compared both with each other and with other local populations of the species in the coastal drainage of southeastern Brazil. Additional molecular data (RAPD markers and genetic diversity) were obtained from specimens from coastal and continental regions of southern Brazil. The same diploid number (52 chromosomes), karyotypic formula and Ag-NOR phenotype were found for both analysed samples from the Iguacu River. A genetic discontinuity was discovered in the comparison of the karyotypical formula of the Iguacu samples with those from coastal drainages of the region. Polymerase chain reaction-RAPD markers revealed strikingly different molecular profiles between coastal and continental samples and indications of a high degree of genetic variation. Based on these results, we provide some comments on the biogeographical patterns and evolutionary trends for M. microlepis from coastal and continental regions of southeastern/southern Brazil.
TL;DR: The present analysis confirms that syrnolopsines possess a spermatophore-forming organ – a synapomorphy of the Paludomidae – corroborating their placement in this family.
Abstract: The minute syrnolopsine gastropods endemic to Lake Tanganyika have been allied to a number of freshwater, marine and terrestrial groups as a consequence of superficial conchological similarity. Although early anatomical studies confirmed the cerithioid organization of this clade, their close relationship to other lake species was not consistently recognized. In several recent cladistic analyses based on molecular data, the higher taxonomic placement and sister group relationships of syrnolopsines have been unstable. The present analysis confirms that syrnolopsines possess a spermatophore-forming organ – a synapomorphy of the Paludomidae – corroborating their placement in this family. Consistent with the molecular data, syrnolopsine monophyly is supported by two characters that occur exclusively in this group (salivary gland ducts that bypass the nerve ring and a linear albumen gland). Several characters in Martelia tanganyicensis– the most diminutive syrnolopsine – are only evident in the smallest lake species thus far investigated (Bridouxia, Stormsia) namely reduction of ctenidial leaflets, sorting area, intestine length and number of statoconia. These features are interpreted as being correlated with reduction in size. Nevertheless, close examination reveals differences in detail that allow more refined hypotheses of homology and are consistent with their independent origin.
TL;DR: Data is presented on the haemolymph vascular system (HVS) in four representatives of the major amphipod lineages Gammaridea, Hyperiidea and Caprellidea based on corrosion casting and three-dimensional reconstructions of histological semi-thin sections.
Abstract: We present data on the haemolymph vascular system (HVS) in four representatives of the major amphipod lineages Gammaridea, Hyperiidea and Caprellidea based on corrosion casting and three-dimensional reconstructions of histological semi-thin sections. In all these species the HVS comprises a dorsal pulsatile heart, which is continued in the body axis by the anterior and posterior aortae. The heart is equipped with three pairs of incurrent ostia. The number of cardiac arteries that lead off the heart varies among species: in the studied Gammaridea four pairs occur, in Hyperia galba only the three posterior pairs of cardiac arteries occur, while in Caprella mutica cardiac arteries are absent. In all the studied species the posterior aorta leads as a simple tube into the pleon attached to the dorsal diaphragm. The anterior aorta runs from its origin in the anterior part of the second thoracic segment into the cephalothorax. Both pairs of antennae have an arterial supply off the anterior aorta. An overview of previously studied species including our present findings shows the amphipod HVS to be relatively uniform and the gammarid form is discussed as being closest to the ground pattern of Amphipoda.
TL;DR: Light and electron microscopy methods were used to characterize the epithelial cells in the mid-intestine of Aplysia depilans and found that intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.
Abstract: To improve the current knowledge about the digestive system in opisthobranchs, light and electron microscopy methods were used to characterize the epithelial cells in the mid-intestine of Aplysia depilans. This epithelium is mainly formed by columnar cells intermingled with two types of secretory cells, named mucous cells and granular cells. Columnar cells bear microvilli on their apical surface and most of them are ciliated. Mitochondria, multivesicular bodies, lysosomes and lipid droplets are the main components of the cytoplasm in the region above the nucleus of these cells. Peroxisomes are mainly found in middle and basal regions, usually close to mitochondria. Mucous cells are filled with large secretory vesicles containing thin electron-dense filaments surrounded by electron-lucent material in which acidic mucopolysaccharides were detected. The basal region includes the nucleus, several Golgi stacks and many dilated rough endoplasmic reticulum cisternae containing tubular structures. The granular cells are characterized by very high amounts of flat rough endoplasmic reticulum cisternae and electron-dense spherical secretory granules containing glycoproteins. Enteroendocrine cells containing small electron-dense granules are occasionally present in the basal region of the epithelium. Intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.