Brain Structure in Calamoichthys calabaricus Smith 1865 (Polypteridae,Brachiopterygii)

The brain of Calamoichthys calabaricus is reconstructed including the arrangement of the parts of the brain and the cranial nerves and their nuclei. Histologically, the analysis includes structure of the rhombencephalon with its cranial and tegmental nuclei, and the cerebellum.     

Notes on the Midbrain and Forebrain of Calamoichthys calabaricus Smith, 1865 (Polypteridae,Brachiopterygii)

The rostral parts of the brain in Calamoichtkys calabaricus, a brachiopterygian fish, show some similarities with actinopterygians, as well as with lungfishes and amphibians. This study includes a histological analysis of the optic tectum, pretectum, diencephalon and the olfactory system.     

Distribution and Structure of the Adrenocortical Homolog in the Reed-Fish (Calamoichthys calabaricus Smith)

The adrenocortical homolog (AH) was identified in the reed-fish ( Calamoichthys calabaricus Smith) using histochemistry for the enzyme δ⁵-3β-hydroxysteroid dehydrogenase (3β-HSD) and its distribution and structure were examined with both light and electron microscopy. AH appears as yellow corpuscles which extend as isolated bodies throughout the length of both kidneys in close apposition to the posterior cardinal veins. The yellow corpuscles are composed of convoluted cords of epithelial cells and tortuous sinusoids which empty directly into the cardinal veins. Wide lateral intercellular spaces and accompanying microvilli give the impression of pseudotubules or pseudofollicles to the cords of epithelial cells. The extensive network of tubules of smooth endoplasmic reticulum, the many mitchondria with tubulo-vesicular cristae, the conspicuous Golgi apparatus, lipid droplets, many pleomorphic granules and the presence of 3β-HSD are indicative of the steroidogenic nature of the cells. Large, pleomorphic mitochondria and gap junctions are also typical of most cells. The fine structure of the cells in the AH of the reed-fish most closely resembles that of other Polypteriformes, but the tissue is more widely distributed in the kidneys than in any osteichthylian so far reported.     

Ultrastructural data on the scales of the dipnoan Protoptems annectens (Sarcopterygii, Osteichthyes)

The structure and the mineralization of the scales of the living dipnoan (lungfish) Protoptems annectens have been investigated by transmission electron microscopy (TEM). The thin and imbricated scales are composed of two layers: the squamulae and the basal plate. At the outer surface, the squamulae form isolated plates superficially ornamented with spines and concretions and made up of acellular bone. After demineralization, the squamulae show a heterogeneous organic matrix composed of thin randomly oriented collagen fibrils forming a loose network within which the concretions appear as electronlucent circular areas. Abundant and aggregated concretions are located within the spines. The crystallites are oriented by the collagen fibrils except in the concretions. Anchoring bundles composed of parallel collagen fibrils arise from the squamulae and connect the scales to the overlying dermis.
The basal plate, the most developed part of the scale, is made up of isopedine. Its main component consists of thick, closely packed collagen fibrils organized in a 'double twisted plywood-like structure'. Fibroblasts are present in the basal plate. Mineralization occurs only in few plies located beneath the squamulae. Mandl's corpuscles are found in front of the mineralization front. The mineral deposit is oriented by the collagen fibrils.
The scales of Protoptems annectens differ from the typical elasmoid scales of the teleosts by the peculiar structure of the squamulae, nevertheless they show enough structural characteristics to support the hypothesis that they can be considered as scales of the elasmoid grade, which have retained some plesiomorphic characteristics.     

Immunocytochemical demonstration of somatotropin-like and prolactin-like activity in the brain of Calamoichthys calabaricus (Actinopterygii)

Summary Cellular binding of anti-bSTH and anti-oPRL IgG is demonstrated in the brain and the pituitary gland of the African freshwater fish Calamoichthys calabaricus by means of the unlabeled antibody enzyme method at the light microscopic level. In the brain, somatotropin and prolactin are demonstrated in separate neurons in the preoptic area. The somatotropinergic and prolactinergic perikarya are distinct from those of the hypothalamic-hypophysial neurosecretory neurons, i.e., those stainable with aldehyde fuchsin presumed to be vasotocinergic and isotocinergic. The somatotropinergic and prolactinergic neuronal perikarya give rise to separate beaded axons which pass either ventroposteriorly into the infundibulum, terminating in the neurohypophysis, or ventro-laterally through the wall of the preoptic recess, terminating near the superficial capillary bed covering this part of the brain surface. Moreover, coarse dendrite-like processes of both kinds of immuno-reactive neurons extend towards, and end in, the third ventricle. Binding sites in the brain to antisera against hLH, hFSH, hTSH and anti-(1–24) ACTH IgG, all reactive in the pituitary, are not observed in the neurons confined to the preoptic area.Supported by the Danish Natural Sciences Research CouncilThe authors wish to thank Professor Dr K.G. Wingstrand, University of Copenhagen, Denmark, for placing two series of C. calabaricus at their disposal. They would also like to thank the National Institute of Arthritis, Metabolism and Digestive Diseases, Bethesda, USA, for the generous gift of antisera against the subunits of human LH, TSH and FSH, and likewise Dr L. Hummer, Glostrup Hospital, Copenhagen, Denmark, for the gift of the anti-(1-24)ACTH IgG     

Characteristics of the reparative regeneration of fins in the polypterid fish (Polypteridae, Actinopterygii)

Epimorphic regeneration of fins was studied in different ray-finned fishes (Actinopterygii), but species representing the phylogenetically basal lineages of the taxon have remained outside the attention of researchers. Information on the regenerative abilities of these groups is important both for understanding the evolutionary origins of the epimorphic regeneration phenomenon and for assessing the universality of regenerative potencies in Actinopterygii. Addressing this problem, we studied for the first time fin regeneration in two members of the archaic family Polypteridae: the ropefish (Erpetoichthys calabaricus) and the Senegal bichir (Polypterus senegalus). Along with the ability to regenerate the bony rays of fins, widespread among Actinopterygii, polypterids show the ability to effectively regenerate the endoskeleton and musculature of their fins. This unusual feature allows us to suggest polypterids as new model organisms for the study of the mechanisms of vertebrate limb regeneration.     

Characteristics of the reparative regeneration of fins in the polypterid fish (Polypteridae,Actinopterygii)

Epimorphic regeneration of fins was studied in different ray-finned fishes (Actinopterygii), but species representing the phylogenetically basal lineages of the taxon have remained outside the attention of researchers. Information on the regenerative abilities of these groups is important both for understanding the evolutionary origins of the epimorphic regeneration phenomenon and for assessing the universality of regenerative potencies in Actinopterygii. Addressing this problem, we studied for the first time fin regeneration in two members of the archaic family Polypteridae: the ropefish (Erpetoichthys calabaricus) and the Senegal bichir (Polypterus senegalus). Along with the ability to regenerate the bony rays of fins, widespread among Actinopterygii, polypterids show the ability to effectively regenerate the endoskeleton and musculature of their fins. This unusual feature allows us to suggest polypterids as new model organisms for the study of the mechanisms of vertebrate limb regeneration.     

Formation and structure of scales in the Australian lungfish,neoceratodus forsteri (Osteichthyes: Dipnoi)

The large elasmoid scales of the Australian lungfish, Neoceratodusforsteri, are formed within the dermis by unpigmented scleroblasts, growing within a collagenous dermal pocket below a thick glandular epidermis. The first row of scales, on the trunk of the juvenile lungfish, appears below the lateral line of the trunk, single in this species, at around stage 53. The scales, initially circular in outline, develop anteriorly and posteriorly from the point of initiation in the mid‐trunk region, and rows are added alternately below the line, and above the line, until they reach the dorsal or ventral midline, or the margins of the fins. Scales develop later on the ventral surface of the head, from a separate centre of initiation. Scales consist of three layers, all produced by scleroblasts of dermal origin. The outermost layer of interlocking plates, or squamulae, consists of a mineralised matrix of fine collagen fibrils, covered by unmineralised collagen and a single layer of cells. Squamulae of the anterior and lateral surfaces are ornamented with short spines, and the mineralised tissue of the posterior surface is linked to the pouch by collagen fibrils. The innermost layer, known as elasmodin, consists of bundles of thick collagen fibrils and cells arranged in layers. An intermediate layer, made up of collagen fibrils, links the outer and inner layers. The elasmoid scales of N. forsteri can be compared with scale types among other osteichthyan groups, although the cellsand canaliculi in the mineralised squamulae bear littleresemblance to typical bone. J.Morphol., 2012. © 2011 Wiley Periodicals, Inc.     

On the habitat and isolation of Gymnocharacinus bergi (Osteichthyes: Characidae)

Synopsis Gymnocharacinus bergi is a rare Paranensean fish which is the only characiform almost lacking scales in the adult. It is endemic and the only species in a peculiar spot — a tributary of the Valcheta creek — in the Somuncurá plateau in northern Patagonia, Argentina, over 300 km from the nearest place with a paranensean fish fauna. Besides its geographical isolation, G. bergi occurs within an area with climatic features drastically different from those currently associated with fishes from Neotropical temperate zones. We tested the assumption that water temperature in the naked characin habitat do not agree with the northern Patagonia climate. We also considered the isolation of G. bergi within the framework of an increasing inpoverishment of the paranensean ichthyofauna along a NE-SW axis in the Buenos Aires province. For this we applied a decrement equation used in island biogeography. Our findings demonstrate that the existence of G. bergi in its isolated habitat is possible because of the thermal traits of the water at the sources of the creeks, its temperature being independent of the climate of the area. The chemical composition of water was found to be within the range of common environments in the Buenos Aires pampas inhabited by several species of Paranensean fishes. Geographically, G. bergi lives in the last of a series of habitats which show a decreasing number of species correlated with the increasing distance from the La Plata River. Conservation status of the species is briefly discussed.     

Occurrence of Lobotes surinamensis (Osteichthyes: Lobotidae) in the Mediterranean: Historical and recent data

This paper provides a review of the current status and historical distribution of Lobotes surinamensis in the Mediterranean Sea. Thirty two records were compiled for the period between 1968 and 2016, which shows that the species is in the Mediterranean much more abundant than previously understood.     

Karyotypic characterization and genomic organization of the 5S rDNA in <Emphasis Type="Italic">Polypterus senegalus</Emphasis> (Osteichthyes,Polypteridae)

Polypteridae (Cladistia) is a family of archaic fishes, confined to African freshwaters. On account of their primitiveness in anatomical and morphological characters and mosaic relationships among lower Osteichthyans fishes, they constitute an important subject for the study of evolution in vertebrates. Very little is known about the karyological structure of these species. In this article, a cytogenetic analysis on twenty specimens of Polypterus senegalus (Cuvier, 1829) was performed using both classical and molecular techniques. Karyotype (2n = 36; FN = 72), chromosome location of telomeric sequences (TTAGGG) _n , (GATA)₇ repeats and ribosomal 5S and 18S rRNA genes were examined by using Ag-NOR, classical C-banding, CMA₃ staining and FISH. Staining with Ag-NOR showed the presence of two GC rich NORs on the p arm of the chromosome pair no. 1. CMA₃ marked all centromerical and some (no. 1 and no. 14) telomeric regions. FISH with 5S rDNA marked the subtelomeric region of the q arm of the chromosome pair no. 14. FISH with 18S rDNA marked the telomeric region of the p arm of the chromosome pair no. 1, previously marked by Ag-NOR. (GATA)₇ repeats marked the subtelomeric regions of all chromosome pairs, with the exclusion of the no. 1, 3 and 14. Hybridization with telomeric probes (TTAGGG) _n showed bright signals at the end of all chromosomes. After cloning, the 5SrDNA alignment revealed an organization of sequences made up of two different classes of tandem arrays (5S type I and 5S type II) of different lengths.     

The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation,pelvic fin loss,and craniofacial morphology in Osteichthyes

Background  

The family Polypteridae, commonly known as "bichirs", is a lineage that diverged early in the evolutionary history of Actinopterygii (ray-finned fish), but has been the subject of far less evolutionary study than other members of that clade. Uncovering patterns of morphological change within Polypteridae provides an important opportunity to evaluate if the mechanisms underlying morphological evolution are shared among actinoptyerygians, and in fact, perhaps the entire osteichthyan (bony fish and tetrapods) tree of life. However, the greatest impediment to elucidating these patterns is the lack of a well-resolved, highly-supported phylogenetic tree of Polypteridae. In fact, the interrelationships of polypterid species have never been subject to molecular phylogenetic analysis. Here, we infer the first molecular phylogeny of bichirs, including all 12 recognized species and multiple subspecies using Bayesian analyses of 16S and cyt-b mtDNA. We use this mitochondrial phylogeny, ancestral state reconstruction, and geometric morphometrics to test whether patterns of morphological evolution, including the evolution of body elongation, pelvic fin reduction, and craniofacial morphology, are shared throughout the osteichthyan tree of life.     

Ejaculatory duct of the migratory grasshopper,Melanoplus sanguinipes (fabr.) (Orthoptera : Acrididae): A histological and ultrastructural analysis

The ejaculatory duct of the migratory grasshopper (Melanoplus sanguinipes [Fabr.]) (Orthoptera : Acrididae) is divisible into 3 regions: upper ejaculatory duct (UED) into whose anterior end the accessory glands and vasa deferentia empty; the funnel characterized by its slit-like lumen; and the lower ejaculatory duct (LED). Anteriorly, the UED has a keyhole-shaped lumen surrounded by a thin intima and highly columnar epithelial cells whose most conspicuous feature is massive aggregations of microtubules. More posteriorly, the UED lumen differentiates into dorsal and ventral chambers, the former having a thick cuticular lining armed with spines. In the hindmost part of the UED, the ventral chamber expands to obliterate the dorsal chamber; its cuticular lining thickens, and conspicuous lateral evaginations develop. The thick cuticle includes 3 distinct layers and on its surface carries numerous spatulate processes. In this region, the epithelial cells develop numerous short microvilli beneath which are many mitochondria. As the funnel is reached, the intima becomes extremely thick, and the epithelial cells lack microvilli and most microtubules. Within the funnel, a new, very distinct form of cuticle appears, which is in “units”, each associated with an epithelial cell and having a rounded epicuticular cap. The new cuticle arises ventrally but rapidly spreads to encircle the entire lumen, at which point the LED is considered to begin. Beneath this new cuticle, the epithelial cells are columnar, have long microvilli, numerous mitochondria in the apical cytoplasm, and rough endoplasmic reticulum basally. Apically, adjacent cells are tightly apposed; however, prominent intercellular channels develop more basally. The ejaculatory duct's features are briefly discussed in terms of its role in spermatophore formation.     

Revision of Phymatolithon purpureum (Hapalidiales,Rhodophyta) based on ultrastructural and molecular data

ABSTRACT

To elucidate the taxonomy and phylogeny of Phymatolithon purpureum (P. Crouan & H. Crouan) Woelkerling & L.M. Irvine, we observed the type specimens and fresh samples using SEM (ultra-morphology) and analysed DNA sequences. Phymatolithon purpureum was originally described as Lithothamnion purpureum P. Crouan & H. Crouan from Mingant, Brittany, France. Our molecular phylogenetic analyses using psbA and COI–5P regions placed our collections from Ireland, UK and France in a clade with ‘P. borealis W.H. Adey, J.J. Hernandez-Kantun & P.W. Gabrielson (MH252286)’ from Iceland and ‘uncultured Corallinales (GQ917711 and GQ917512)’ from Roscoff, Brittany, France, near the type locality of P. purpureum. We show that P. purpureum is conspecific with P. borealis and P. polymorphum f. papillatum (Foslie) Foslie based on morphology and molecular data. Also, although P. purpureum has been often confused with P. laevigatum (Foslie) Foslie because of their similar morphology (e.g. smooth surface and sunken tetra/bisporangial conceptacles), our molecular phylogenetic analyses indicate that P. purpureum and P. laevigatum are sister taxa. Our sequences from lectotype material of P. laevigatum and syntype material of Lithothamnion emboloides Heydrich are identical.     

Sperm aggregations in female Agkistrodon piscivorus (Reptilia:Squamata): a histological and ultrastructural investigation

Upon copulation in female Agkistrodon piscivorus, sperm migrate up the oviduct to sperm storage tubules (SSTs) in the posterior infundibulum. The epithelium of the SSTs is composed of ciliated and secretory cells and differs ultrastructurally from that of the epithelium lining the lumen of the posterior infundibulum. Sperm pass through an area composed primarily of ciliated cells at the opening of each gland before aligning themselves in parallel arrays with their nuclei facing an area composed primarily of secretory cells at the base of the tubules. Sperm are also found embedded inter- and intracellularly in the SSTs. The secretory vacuoles in the SSTs become highly electron dense after the start of the fall mating season along with the synthesis of lipid droplets. Histochemical analysis reveals that the alteration in secretory material density is caused by the production of neutral carbohydrates. Some sperm remain in aggregates in the nonglandular section of the posterior uterus until the time of ovulation. However, ultrastructural evidence indicates these sperm degrade before ovulation. Therefore, sperm in posterior aggregates have no role in fertilization of ovulated ova. The data presented here support the hypothesis that infundibular sperm storage is the mode that snakes utilize to sequester viable sperm until ovulation.     

Pleistocene effects on the European freshwater fish fauna: double origin of the cobitid genus Sabanejewia in the Danube basin (Osteichthyes: Cobitidae)

Biogeographical hypotheses of European freshwater fishes were inferred using phylogeographic analysis of the complete cytochrome b and ATP synthase 8 and 6 mitochondrial genes (1982bp). To test the relative importance of drainage origin versus Pleistocene glaciations in the origin of primary freshwater fishes in Europe, we reconstructed the phylogenetic relationships of the genus Sabanejewia which is distributed in European waters. The phylogenetic relationships recovered for the genus Sabanejewia (n=75) provide support for the monophyly of six main evolutionary mtDNA lineages: Sabanejewia larvata, Sabanejewia romanica, Sabanejewia aurata/Sabanejewia caucasica, Sabanejewia kubanica, Sabanejewia baltica, and the Danubian-Balkanian complex. The Caucasian-Caspian mtDNA lineages, S. kubanica, S. aurata/S. caucasica, and the Northern European S. baltica represents the sister group of the Danubian-Balkanian complex mtDNAclade, supporting a Caucasian-Northern European origin of most of mtDNA lineages of the Central European freshwater fish fauna. The mtDNA divergence observed between the Danubian Sabanejewia species is too dissimilar to support their contemporary origin. Rather, the mtDNA data suggest that the Danubian Sabanejewia lineages most likely have a double origin, indicating that the European Sabanejewia lineages have experienced different historical processes for the following reasons. First, the origin of the S. larvata and S. romanica mtDNA clades predates the origin of the Danubian-Balkanian complex, and our results showed that the completion of the Alps and the origin of the Danube drainage seem to have promoted the speciation of the earliest Sabanejewia clades in the Miocene. Second, small genetic distances and the geographical pattern found within the Danubian-Balkanian complex clade indicate that the lineages included in this clade spread recently across the Danube and Greek river drainages. The inclusion of the S. balcanica species within all mtDNA lineages suggests that cyclical cold periods during the Pleistocene glaciations have favoured its rapid expansion and genetic homogenisation across Central European and Greek waters.     

An ultrastructural study of shell regeneration in Mytilus edulis (Mollusca: Bivalvia)

Female budgerigars, provided with nest-boxes and exposed to male vocalizations, lay more rapidly under a 14 L: 10 D photoregime than under regimes involving shorter light periods, though some birds will lay even when kept under continuous darkness. The photoperiod affects principally the interval between nest-box entry and egg-laying. Birds with previous breeding experience lay sooner than naive birds.     

Taxonomic revision of Dictyochales (Dictyochophyceae) based on morphological,ultrastructural, biochemical and molecular data

The taxonomy of the siliceous members of Dictyochales has been based exclusively on the structure of their silica skeletons. In this study, other morphological, ultrastructural, pigment and molecular characters, in addition to the silica skeletons, were used in the systematics of the siliceous members of this group. As very little is known about the ultrastructure of Dictyocha octonaria, cells of both the skeleton‐bearing and naked forms were also studied. A cladistic analysis based on morphological data and a molecular phylogeny based on nuclear coded small subunit ribosomal DNA retrieved a well‐supported monophyletic Dictyochales. D. octonaria and D. speculum were resolved together with strong support. There was no support for a clade for the three species currently placed in Dictyocha; D. fibula is clearly distinct from the other two Dictyocha taxa, D. speculum and D. octonaria. It is highly likely there are two or three undescribed species within D. octonaria/D. speculum clade and two undescribed genera within the Dictyochales, based on the positions of sequences from uncultured eukaryotes present in GenBank. These findings necessitate a taxonomic revision of the three siliceous, skeleton‐bearing species. Because D. fibula is the type species of Dictyocha, we propose that D. octonaria and D. speculum be reassigned respectively to the genus Octactis as O. octonaria Hovasse and O. speculum (Ehrenberg) F. H. Chang, J. M. Grieve & J. E. Sutherland, comb. nov.