The fine structure of lamellate cells in the brain of amphioxus (Branchiostoma lanceolatum,Cephalochordata)

Summary The lamellate cells of amphioxus have round nuclei, and cytoplasm with many mitochondria and a large amount of glycogen. Each of these cells projects a highly modified, branched cilium into the central canal, where it characteristically forms lamellar structures. Primary branches and secondary lamellae often contain accessory microtubules that are not derived from the axonema. The functional and evolutionary significance of this cell type is discussed in relation to the ciliary photoreceptors found in other chordates.This work is dedicated to Professor A. Carrato, Universidad Complutense, on the occasion of his 80th birthday     

The club‐shaped gland of amphioxus: export of secretion to the pharynx in pre‐metamorphic larvae and apoptosis during metamorphosis

In amphioxus larvae, the club‐shaped gland is a tube connecting the pharyngeal lumen with the external environment. The functions of the gland and its fate during the larva‐to‐juvenile metamorphosis have long been controversial. Here we use a fixative including ruthenium red to preserve extracellular secretions (presumably glycoproteins) in late pre‐metamorphic larvae. This procedure reveals reddish, fibrogranular material in the lumen of the club‐shaped gland and in the pharynx adjacent to the gland's inner opening. This finding strengthens the idea that secretions of the club‐shaped gland are exported to the pharyngeal lumen to help form a mucous trap for capturing food particles entering the mouth. We also use the terminal desoxynucleotidyl transferase‐mediated dUTP nick end labelling (TUNEL) assay to study apoptosis in the tissues of metamorphosing larvae. One of the earliest events of metamorphosis is the massive apoptotic destruction of the club‐shaped gland. Therefore, despite some previous opinions to the contrary, the cells of the gland do not survive to participate in the genesis of the definitive endostyle or any other post‐larval structures.     

The natural hosts for larvae and nymphs of Amblyomma neumanni and Amblyomma parvum (Acari: Ixodidae)

Based on the hypothesis that birds and rodents are important hosts for subadults of the Neotropical Amblyomma neumanni and Amblyomma parvum ticks, a survey of these type of hosts was carried out from July 2004 to March 2006, in Quilino (A. parvum) and Dean Funes (A. neumanni), Córdoba province, Argentina. Additionally, monthly tick counts were performed on cattle and goats with occasional tick search in other domestic hosts. Records of questing height of subadult ticks on vegetation were also carried out monthly. Rodents (n = 123) and birds (n = 122) captured in Dean Funes showed no infestation with A. neumanni. Apart of few nymphs found on horses, all larvae and nymphs of A. neumanni were on cattle with a larval prevalence and mean number of 22.2%, and 7.7 ± 22.52, respectively, and a prevalence of nymphs of 47.8% with a mean of 7.9 ± 18.49. The average questing height of larvae and nymphs of A. neumanni was 23.5 ± 17.1 cm and 30.7 ± 26.7 cm, respectively. A total of 138 rodents and 130 birds were captured in Quilino but the Caviidae rodent Galea musteloides carried 99.3% of larvae and 99.8% of nymphs of A. parvum, and no immature stages were detected on cattle, goat or vegetation. Tick counts on G. musteloides (n = 74) showed a prevalence of 42% and a mean number of 9.9 ± 24.83 for larvae, while nymphal infestation had a prevalence of 56.5% and a mean of 8.7 ± 11.31. Cattle appear to be suitable hosts to sustain the complete cycle of A. neumanni in nature (adult ticks infest cattle too) and questing height of subadults indicates that they are expecting to feed on medium and large-sized mammals, such as cattle and other ungulates. At least in the study site, G. musteloides is the principal host for the survival strategy of A. parvum subadults; adult ticks are common on cattle and goats. These hosts are introduced in the Neotropics but A. neumanni was able to develop a surrogate cycle independent of native hosts while A. parvum still depends on probably primeval hosts to sustain their larvae and nymphs.     

Morphology, anatomy, and taxonomic position of Pagameopsis (Rubiaceae-Rubioideae)

Morphological and anatomical features (including wood anatomy and pollen morphology) of the small neotropical genusPagameopsis (Rubiaceae-Rubioideae) are discussed and illustrated. The fused ovaries, fenestrate corolla tube, basally attached anther filaments, and absence of raphides are especially noteworthy.Pagameopsis is definitely not a member of the Psychotrieae because of significant differences in wood anatomy and gynoecial and fruit structure. A close affinity with Gaertnereae seems doubtful for similar reasons. The taxonomic affinities ofPagameopsis remain obscure. The genus shows similarities with several taxa of the Rubioideae, such as Coccocypseleae, Morindeae, Hedyotideae, andMetabolos. The absence of raphides, on the other hand, makes a position in the Rubioideae doubtful.     

Characterization and developmental expression of AmphiNk2-2, an NK2 class homeobox gene from amphioxus (Phylum Chordata; Subphylum Cephalochordata)

 The genome of amphioxus includes AmphiNk2-2, the first gene of the NK2 homeobox class to be demonstrated in any invertebrate deuterostome. AmphiNk2-2 encodes a protein with a TN domain, homeodomain, and NK2-specific domain; on the basis of amino acid identities in these conserved regions, AmphiNk2-2 is a homolog of Drosophila vnd and vertebrate Nkx2–2. During amphioxus development, expression of Amph- iNk2-2 is first detected ventrally in the endoderm of late gastrulae. In neurulae, endodermal expression divides into three domains (the pharynx, midgut, and hindgut), and neural expression commences in two longitudinal bands of cells in the anterior neural tube. These neural tube cells occupy a ventrolateral position on either side of the cerebral vesicle (the probable homolog of the vertebrate diencephalic forebrain). The dynamic expression patterns of AmphiNkx2-2 suggest successive roles, first in regionalizing the endoderm and nervous system and later during differentiation of specific cell types in the gut (possibly peptide endocrine cells) and brain (possibly including axon outgrowth and guidance). Received: 24 November 1997 / Accepted: 2 February 1998     

The Wheel Organ and Hatschek's Groove in the Lancelet,Branchiostoma lanceolatum (Cephalochordata)

The wheel organ is a specialized epithelium in the roof and sides of the adult lancelet oral cavity. It borders the oral epithelium proper, separated by a thin strip of margin cells which are not ciliated but contain a few large dense-cored vesicles apically. The wheel organ cells are tall and strongly ciliated and have dark, heterochromatin-rich nuclei. Dorsally, and slightly paramedially, the organ is further specialized, forming the so-called Hatschek's groove (pit), which consists of two ciliated cell types. The first type synthesizes a dense granular material, the granules being approximately 95 nm in diameter. This is stored basally and apparently it is also released through the basal cell membrane into the blood cavities. The cells at the bottom of Hatschek's groove have peculiar rod-shaped apical cellular regions. Each cell bears one tall cilium surrounded by microvilli and it is apparently involved in the production of secretory material into the groove. It is evident that the histology, and probably also the function, of the wheel organ and its groove is much more complex than hitherto believed.     

Luthrobium (Tetartopeus): natural history, phylogeny and revision of the nearctic species (Coleoptera, Staphylinidae)

Abstract. The eleven species of Lathrobium subgenus Tetartopeus from the Nearctic Region are revised. Thirteen specific names are placed in synonymy, Lconvolutum sp.n. is described, and Deratopeus Casey is synonymized with Tetartopeus . A cladistic analysis suggests that Tetartopeus is monophyletic, and that five monophyletic species-groups are represented in the Nearctic Region.     

The taxonomic value of leaf anatomy and trichome morphology of the genus Cyclotrichium (Lamiaceae) in Turkey

The genus Cyclotrichium (Boiss.) Manden. & Scheng. is represented by six species in Turkey: C. glabrescens, C. leucotrichum, C. longiflorum, C. niveum, C. origanifolium and C. stamineum. They are aromatic perennial subshrubs used as spices or herbal teas in traditional Turkish medicine. The leaf anatomy and tomentum morphology of leaves and calyces of Cyclotrichium species in Turkey was investigated by scanning electron microscopy (SEM) and light microscopy (LM). The investigated species have equifacial (C. niveum, C. origanifolium) or bifacial leaves (C. glabressens, C. leucotrichum, C. longiflorum, C. stamineum). All species have peltate and capitate glandular, and simple (all species) or branched (C. niveum) eglandular trichomes and diacytic stomata. Peltate trichomes consist of a basal cell embedded in the epidermis, a stalk cell, and a broad 12 (–13)‐celled secretory head arranged in two concentric circles. The capitate trichomes observed in Cyclotrichium can be grouped into five types, differing in structure and size. They consist of either a pear‐shaped or globose unicellular head and uni‐or bicellular stalk, or a bicellular head and bicellular stalk. The density of peltate, capitate and eglandular trichomes differs between species. Peltate trichomes are densely spaced only on the calyx and on the leaf surface of C. niveum and C. origanifolium and on the abaxial leaf surface of C. longiflorum and C. stamineum. The significance of trichome architecture for taxonomy in Cyclotrichium and Lamiaceae in general is discussed.     

Parasitism (Trematoda,Digenea) in medusae from the southwestern Atlantic Ocean: medusa hosts,parasite prevalences,and ecological implications

Digenean are important endoparasites of fish with complex life cycles; some genera include medusae as secondary hosts. Their transmission to fish occurs when fish prey on these jelly hosts. Fish predation on jellyfish is a widespread phenomenon, even though predation by fish on jellyfish has not been determined through parasitism yet. We hypothesized that medusae with high prevalences of digeneans could be important for their transmission to fish. A total of 48,900 specimens of 50 medusa species were analyzed; 2,181 harbored digeneans. Opechona sp. and Monascus filiformis were the most frequent and abundant parasites with the widest range of hosts. Hemiuridae gen. sp. and Bacciger sp. were found in few specimens of some medusa species. Prevalences were unevenly distributed in the region. Three groups with high prevalence values were identified mainly related to frontal areas: Río de la Plata, Bahía Blanca, and North Patagonian tidal front. Eucheilota ventricularis, Clytia hemisphaerica, Proboscidactyla mutabilis, Liriope tetraphylla, and Aequoerea spp. were the medusae that contributed the most as secondary hosts to M. filiformis and Opechona sp. The high prevalences found in these medusae suggest that may be a fundamental part of the life cycles of both parasites in these areas.     

Sigmodontinae rodents as hosts for larvae and nymphs of Ixodes loricatus Neumann, 1899 (Acari: Ixodidae)

Larvae and nymphs of Ixodes loricatus Neumann, 1899 ticks (confirmed by morphological characters and by comparison of 16S mitochondrial rDNA sequences) were collected from Sigmodontinae Wagner, rodents in central and northern Argentina and Uruguay. A total of 100 larvae and 38 nymphs of I. loricatus were collected on the genera Akodon Meyen (n = 36 individuals), Calomys Waterhouse (n = 2), Oligoryzomys Bang in = 12), Oxymycterus Waterhouse (n = 9), and Scapteromys Waterhouse (n = 13). 72 larvae and 18 nymphs were collected on Akodon. Adults of I. loricatus were found in central Argentina and Uruguay on Didelphimorphia of the genera Didelphis Linnaeus and Lutreolina Thomas. Ixodes loricatus has been considered a species with strict total specificity to Didelphimorphia. Our results show that this statement may not be justified. Sigmodontinae rodents are sympatric and share habitats with the phylogenetically distant Didelphimorphia; infestation with I. loricatus seems to be its consequence. We tentatively consider I. loricatus moderately specific to Didelphimorphia.     

The myosepta in Branchiostoma lanceolatum (Cephalochordata): 3D reconstruction and microanatomy

Zoomorphology - Myosepta have been subject to comparative and evolutionary studies in aquatic groups of the Craniata, because they are likely to play a role in transmission of muscular forces to...     

Bulb tunic anatomy and its taxonomic implication in Allium L. (Amaryllidaceae: Allioideae)

Abstract

Allium is taxonomically a difficult genus with blurred taxonomic borders at all taxonomic ranks. In this research, anatomy and morphology of bulb tunics in 42 species of the genus representing its 16 currently recognized sections and 6 subgenera (Allium, Cepa, Reticulatobulbosa, Amerallium, Polyprason and Melanocrommyum) were investigated. Our results indicated the following characters to be most informative at sectional and subgeneric levels: features of calcium oxalate crystals and subepidermal cell layer of the outermost bulb tunic, type of tracheids, and bulbils presence. Three main types of crystals, i.e. prismatic, sand and druses, were fairly common among the investigated species except for the members of A. sect. Acanthoprason (A. subg. Melanocrommyum) that often lack crystals. The subepidermal layers of outer tunics were mostly composed of hexagonal, rectangular, or elongated cells but A. paradoxum (A. subg. Amerallium, sect. Briseis) showed the pentagonal type and A. longisepalum (A. subg. Amerallium, sect. Molium) the elliptic type of subepidermal cells. The members of A. sub. Melanocrommyum showed various types of tunic cells and crystals.     

Electrophoretic identification of larvae and adults of Anisakis (Ascaridida:Anisakidae)

The relationships between larvae and adults of Anisakis from the Mediterranean Sea and North-East Atlantic Ocean were analysed by multilocus electrophoresis. The correspondence of type I larvae with the A. simplex complex, including the sibling species A. simplex A and B, and of type II larvae with A. physeteris is confirmed. 19 of the 22 loci studied discriminated between the two larval types. Biochemical keys are given for the electrophoretic identification of A. simplex A, A. simplex B and A. physeteris, at both the larval and adult stages.     

Structure of the testis and genital duct of freshwater stingray, Himantura signifer (Elasmobranchii: Myliobatiformes: Dasyatidae)

The light microscopic structure of the testis and genital duct system of the freshwater stingray Himantura signifer was observed. The testis is composed of lobes having numerous spermatocysts in a dorsoventral zonated arrangement. The germinal papilla at the middorsal surface of the testicular lobe is the origin site of spermatocyst development, where mesenchymal-like cells are predominantly found. The association of a Sertoli cell precursor with a spermatogonium marks the onset of spermatocyst formation and development. The newly formed spermatocysts at the dorsal end of the germinal zone replace the older ones, which are sequentially moved to the ventral side and are termed spermatogonial, spermatocyte, spermatid, spermatozoal, and degenerate zones. In the degenerate zone, the spermatocysts deteriorate after releasing the spermatozoa into the intratesticular duct, where they are further transported through the extratesticular duct system and finally stored at the seminal vesicle. The epithelial lining of the genital duct is a pseudostratified ciliated columnar with no muscular layer underneath; thus, sperm are conveyed through ciliary activity. The interesting features of the present study are the finding of mesenchymal-like cells in the germinal papilla and the nonaggregated formation of sperm in the seminal vesicle.     

Metazoan parasite infracommunities of Florida pompano (Trachinotus carolinus) from the coast of the Yucatan Peninsula,Mexico

Metazoan parasite infracommunities of the Florida pompano (Trachinotus carolinus) were studied in terms of species composition, species richness, diversity, numerical dominance, and similarity. Seventy-five fishes were collected from 4 localities along the Yucatan Peninsula coast and 24 parasite species recovered. Most were digeneans (8 species) and nematodes (7). Other species were monogeneans (3). aspidogastreans (2), cestodes (1), acanthocephalans (1), and crustaceans (2). Only 4 species were common in at least I locality. Mean values for species richness, abundance, diversity, numerical dominance, and similarity in total (all species in the individual fish), gastrointestinal, and ectoparasite infracommunities were within ranges observed for most helminth infracommunities of marine fishes from temperate and tropical latitudes. These infracommunities had low species richness, abundance, diversity, and predictability (except ectoparasite infracommunities) and high dominance. Within the predictable element (common species), the specialist monogenean Pseudobicotylophora atlantica was the main reason for the increase in predictability because it was the only common species at all 4 localities. Host feeding habits, the distribution of intermediate hosts and infective stages, the local species pool, and a phylogenetic component seem to be determining the characteristics of these metazoan parasite infracommunities.     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

The identification of British limnephilid larvae (Trichoptera: Limnephilidae) which have single-filament gills

SUMMARY. Keys are provided to identify those British limnephilid larvae which are characterized by having gill sites occupied solely by single filaments at the final instar. Most species can be identified at the final instar but many species can also be identified at the earlier instars. A key is also supplied to distinguish the early instar larvae as a group from other limnephilid larvae. Brief notes on distribution and habitat are given. The species identified at least at the final instar are:- Apatania wallengreni, A. auricula, A. muliebris, Drusus annulatus, Ecclisopteryx guttulata, Potamophylax latipennis, P. cingulatus, P. rotundipennis, Melampophylax mucoreus, Allogamus auricollis, Hydatophylax infumatus, Chaetopteryx villosa . It was not possible to segregate Halesus radiatus from H. digitatus, Stenophylax permistus from S. vibex , or S. lateralis from S. sequax .