Unfortunately, Table 1 was incorrectly published in the original version and the same is corrected here in this erratum. The original article was corrected.

The use of volume data and digital three-dimensional (3D) surface models in biology has increased quickly and steadily. Various methods are available to acquire 3D data, among them episcopic imaging techniques. Based on the episcopic microscopy with on-block staining protocol of Weninger et al. (Anat Embryol 197:341–348, 1998), we describe a simple and versatile setup for episcopic microtomy. It is composed of a consumer DSLR digital camera combined with standard histology equipment. The workflow of block surface staining and imaging, image processing, stack alignment, surface generation (including a custom Amira® macro), and 3D model editing is described in detail. For our sample specimen (Alytes obstetricans; Amphibia: Anura) we obtained images with a pixel size of 5.67 × 5.67 µm2. The generated image stacks allowed distinguishing different tissues and were well-suited for creating a 3D surface model. We analyzed the alignment quality achieved by various selections of specimen and fiducial marker spots. The fiducial spots had a significant positive effect on the alignment quality with the best alignment having a maximum mean alignment error of about 44.7 µm. We further tested the APS-C camera with combinations of macro lens, extension tube or teleconverter. The macro lens and extension tube yielded the smallest pixel size of 2.53 × 2.53 µm2. Considering data quality and resolution, and depending on object sizes and research goals, DSLR captured episcopic microtomy can be an alternative to other techniques, such as traditional histological sectioning or micro-computed tomography.

The microturbellarian Prorhynchus stagnalis quells prey with a venom apparatus that also serves as its copulatory organ when the animal is mature. While it has long been known to comprise a tubular, sharp-pointed stylet surrounded concentrically by two mantles of longitudinally aligned rods, our examination of it by electron microscopy and confocal microscopy reveal unexpected details of its structure and mode of operation. The stylet actually has two distinct pieces, of two kinds of extracellular matrix (ECM): a sheet rolled into a tube with a sharp-pointed tip, and a sheet folded into a torus that fits into the proximal end of the tube to create a broadened base on which muscles and the male canal insert. The supporting rods are yet other phases of ECM in the mesenchyme. The six inner ones merge distally to ensheath the stylet, and that sheath bears five channels conducting the secretions of gland cells flanking the stylet to minute pores around the stylet tip. Confocal microscopy of the stylet apparatus in different phases of protrusion show that the outer rods are retracted from a protective position around the tip as the apparatus is protruded by protractors. The stylet is likely then protruded farther by contraction of the penis bulb, so that the stylet pore is exposed to allow the flow of secretions from the prostatic vesicle. The venom could be those secretions, as has been assumed, or secretions of the newly discovered gland cells of the inner mantle.

Eye lens of 196 Loligo vulgaris and 205 Loligo forbesii collected by trawl surveys from 2013 to 2015 in Sardinian waters (Mediterranean Sea) were analysed for age determination. In an alternative to the technique previously used in Sepia officinalis and Enteroctopus megalocyatus, in this study, we proposed the elimination of decalcification and dehydration steps to reduce the time of lens processing. In addition, lenses were included in epoxy resin, which was then subject to lapping, to ensure clear reading and counting of the increments. The number of increments counted in L. vulgaris (59–520) and in L. forbesii (51–543) was strongly related to mantle length and weight of the animals, with no statistical differences between the sexes. Assuming daily growth increments, L. vulgaris was estimated to have a life span of 17 months for males and 14 months for females, while L. forbesii males had an estimated life span of 18 and 16.5 months for females. The exponential model was the best fit for growth data for both species and sexes, showing higher growth for males in comparison with females. These results preliminarily indicate that the eye lens is a valid tool for age determination of the two Loliginidae species, but it would benefit from validation by additional studies.

The tree shrew has been used as a primate animal model in neuroscience studies but it has only rarely been employed in the study of reproductive systems. This is mainly because we know very little about the histological features of reproductive organs of the tree shrew. In this study, we have systematically analyzed the histology of reproductive organs of tree shrew, in comparison with human organs. The uterus of female tree shrew is uterus biomes unicolis, which is connected with an enveloped ovary through a thin fallopian tube. Histologically, the fallopian tube consists of folded mucosa, muscularis and serosa. Like other mammalian animals, the different developmental stages (primordial, primary, secondary and Graafian follicles) of ovarian follicles including inner oocyte and outer granulosa cells are embedded in the cortex. The luminal endometrium, middle muscular myometrium and serosa constitute the wall of uterus of tree shrew. The uterine endometrium contains simple columnar ciliated cells and goblet cells, and there are rich uterine glands in underlying stroma. Furthermore, these glands of tree shrew are round and smaller during anestrus, and become much longer when they are in estrus. The uterine endometrium in younger animals was less developed when compared to a mature tree shrew. Compared to human uterine endometrium, the histological features of tree shrew are very similar, indicating that it could potentially be good primate animal model for studying the diseases in reproductive system.

The general and fine morphology of the buccal armature and concomitant epithelia in Flabellina verrucosa were examined using light microscopy, cLSM, TEM, and SEM. A 3D-reconstruction of the radular sheath terminal end was constructed as well. Based on the obtained data, we suggest the mechanisms of jaw and radula syntheses for this species. The jaw plate’s growth is provided by the apocrine secretion of the gnathoblasts. There are two primary areas of jaw synthesis: the anterior area is responsible for growth formation of the jaw portion used in the masticatory process, and the posterior area provides the growth of the jaw plate. These types of synthesis (common for both areas) were described in detail for the first time for Gastropoda. The radula growth is provided by the microvillar activity of odontoblasts and membranoblasts. The rachidian tooth is synthesised by a single cell, and the lateral teeth are synthesised by group of 3–5 cells. The tooth formation includes four main stages: (1) tooth mould formation; (2) 90° turn of the tooth mould; (3) chitin accumulation, and (4) tooth maturation. The wide range of synthesis mechanisms is provided by a combination of two factors: the type of secretion and the amount of cells.

Reptilian sperm morphology studies are continually increasing, and sperm biology is presently being utilized in other areas of study such as sexual selection, evolution, and phylogenetic analysis. The numbers of studies concerning sperm morphology in Squamata, however, are still limited compared to the diversity and number of lizard and snake species and the taxonomic distribution of these studies is widespread and random. Comparisons between closely related taxa are not feasible until further spermatozoal studies investigating designated comparative taxa are completed; therefore, this study aims to add a description of the mature spermatozoa of Agkistrodon contortrix (Linnaeus, 1766) and compare these data to the mature spermatid morphology of its related taxon, Agkistrodon piscivorus (Lacepede, 1789). Although the general architecture of the mature spermatozoa in A. contortrix is consistent with previous reports of mature sperm morphology in snakes, minor differences are noted including the location of the fibrous sheath starting at mitochondrial tier 4, a location that has not yet been reported for snakes. These data further suggest that minute differences in sperm ultrastructure can be observed in closely related taxa and may be beneficial in future phylogenetic and evolutionary analyses.

The nictitating membrane is an anatomic structure exclusively exhibited by Carcharhiniformes, the largest order among sharks. Here we present a detailed description of morphological characteristics of the nictitating membrane through light microscopy (LM) and scanning electron microscopy (SEM) in the following shark species: Carcharhinus limbatus, Galeocerdo cuvier, Prionace glauca, Rhizoprionodon lalandii, R. porosus, Sphyrna lewini and S. zygaena. Differences in the microscopic aspects of dermal denticles from the species studied were observed. P. glauca, a pelagic shark, showed a well-developed protection apparatus when compared with other pelagic species, while coastal sharks showed even higher structural complexity. In the blue shark the denticles are enameled, presenting an extensive pulp cavity and a base inserted in a connective tissue. Moreover, the species exhibits the higher number of ridges (up to nine) of varied size and shape and the muscular tissue is inserted in the ventral region of the connective tissue. Dermal denticles from C. limbatus, R. lalandii, R. porosus, S. zygaena and G. cuvier exhibit up to five ridges with hexagonal ornamentations in the crown. In S. lewini and S. zygaena, the denticles are rounded shaped and glandular cells are present. The patterns observed in the present study suggest a high level of specialization and evolutionary conservation shaped by the function of the structure. In addition, we hypothesize that the morphological simplification observed in the membrane when compared to the dermal denticles from the skin, is an evolutionary trait that evolved to improve the dynamic and biomechanics of this highly mobile structure allowing this way, a rapid and efficient protection against abrasion, mainly during predation events.

Nematodes are a large and diverse monophyletic taxon with about 20,000 known species. They are part of the taxon Ecdysozoa, some of which possess a characteristic type of brain called the cycloneuralian brain. Because animals with a cycloneuralian brain likely are not a monophyletic group, it is important to describe and understand the structure of cyloneuralian brains and associated nervous system structures. With respect to nematodes, most studies focus on model organisms, such as Caenorhabditis elegans and immunohistochemical data in general, are rare. To expand the knowledge, we investigated two species of the family Plectida, Plectus acuminatus and Plectus aquatilis by immunohistochemical experiments combined with confocal laser-scanning microscopy. In comparison with C. elegans and further nematodes, our results reveal a conserved architecture of the nervous system and several structures can be homologized with known counterparts. Nevertheless, in detail, some striking differences can be demonstrated, which become visible in the arrangement of longitudinal and transverse neurites as well as in specialized neurons, such as the neurosecretory motor neurons within the pharynx. Compared to C. elegans, the branching pattern of these neurons in Plectus spp. is more complex. Overall, there are indications that the nervous system among nematodes is more diverse in structure than originally expected and further studies on taxonomically basal, free-living nematodes needs to be in focus on future investigations.

Fil: Garese, Agustin. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina