Ventral Shield Research Articles

Intraspecific variation and growth anomalies in Wenlockian (Silurian) Cyathaspidiformes (Heterostraci, Agnatha) from Canada

Growth anomalies in shields of cyathaspidiforms often take the form of elevated or depressed concentric areasseparated by lines cutting across the predominantly longitudinal direction of ornamental ridges. In addition, such features as the prominence of epitegal areas and the length and pattern of ridges, commonly used as characters in the diagnosis of species and even subfamilies, appear to be affected by growth irregularities. When added to the normal range of variation in ornamental patterns within species, and the common circumstance of having only one dorsal or ventral shield, often incomplete, from which to describe the species, caution must be advised in using such traits as reliable characters. Dorsal and ventral shields of tolypelepidid and poraspidid cyathaspidiforms from biostratigraphically well-constrained Wenlockian horizons in the Mackenzie Mountains of northwestern Canada show that significant ornamental variation as well as growth aberrations existed relatively early in the evolution of cyathaspidiforms and illustrate the difficulties such variation imposes on diagnosis.

Presence and Localization of Vinculin in Giardia

A requisite element of pathogenicity in Giardia infections is the parasites' ability to adhere to the intestinal epithelial brush border. The presence of vinculin in Giardia was studied because this protein is known to link the cytoskeleton to the plasma membrane and is localized at adhesion foci in many cell-cell and cell-substrate contact sites. Actin, alpha-actinin, and vinculin were identified in Giardia by western blot analysis. Giardia trophozoites attached to glass substrates were examined by interference reflection microscopy (IRM) and immunofluorescence. The IRM defined the lateral crest, bare area, and overlap region of the ventral disk, as well as the ventrolateral flange and lateral shields as close contact areas between parasite and substrate. These close contact regions were then correlated with immunofluorescence localization of actin, alpha-actinin, and vinculin. Actin was seen in the lateral crest, while alpha-actinin was observed in the ventral disc periphery and lateral shields. Vinculin was viewed at the bare and overlap areas of the ventral disc and portions of the lateral crest, as well as the ventrolateral flange and lateral shields. The correspondence of close contact sites with vinculin localization suggests a role for vinculin in Giardia attachment and adherence.

Additional information onAlainaspisandBoothiaspis, cyathaspidids (Agnatha: Heterostraci) from the Upper Silurian of Northwest Territories, Canada

New material of the poraspidAlainaspis platyrhinaElliott and Dineley has made it possible to provide a more extensive reconstruction of this animal. It is now clear that an elongated branchial opening was present below the lateral lamina and that a well-developed post-branchial lobe was present. No branchial plate has been identified and this may have been fused to the dorsal shield, forming the ventral lamina. The lateral lamina is now seen to terminate in a rounded angle before the posterior margin of the shield. Several ventral shields with similar ornament are identified as belonging toA. platyrhina. These are broad and deep and are consistent with the original interpretation of this animal as a filter feeder. One similar shield with a coarser ornament is tentatively assigned to the closely related speciesBoothiaspis ovataBroad.

NORTH AMERICAN WATER MITES OF THE FAMILY MOMONIIDAE VIETS (ACARI: ARRENUROIDEA). I. DESCRIPTION OF ADULTS OF CYCLOMOMONIA ANDREWI GEN.NOV., SP.NOV., AND KEY TO WORLD GENERA AND SUBGENERA

AbstractAdults of Cyclomomonia andrewi gen.nov., sp.nov. are described from interstitial habitats in small, cascading streams in western North America. The genus Cyclomomonia and the subfamily Cyclomomoniinae are proposed and diagnosed, based primarily on the distinctive, complex structure of the dorsal and ventral shields and the genital field. Possible relationships between Cyclomomonia and other Momoniidae are discussed, and a new key to the world genera and subgenera of the family is presented.

A world review of the tiliarum species group in the genus Typhlodromus Scheuten (Acari: Phytoseiidae)

The revised tiliarum species group in the genus Typhlodromus Scheuten is defined by the presence of setae Z1, S2, S4, and S5 as well as J2, J5, Z4, and Z5 on the opisthoscutum, excluding sublateral seta R1 which may or may not be inserted on the opisthoscutum. The chaetotaxy on the opisthoscutum of the revised tiliarum group is identical with that of the australicus (in part) and simplex groups. However, the tiliarum group is distinguished from the former by the absence of seta z6 on the podoscutum and from the latter by differences in the nature of the peritreme and of the setae on the dorsal shield and by the shape of the ventrianal shield. The original tiliarum group included only 3 species whereas the revised group comprises 26 species, including one new species: T. comptus Corpuz, Typhlodromus crassipilis (Athias-Henriot and Fauvel) comb, nov., T. aceri Collyer, T. tuberculatus Wainstein, Typhlodromus runiacus (Kolodochka) comb, nov., T. transitans Gupta, T. tiliarum Oudemans, T. perforatus Athias-Henriot, Typhlodromus carmeli (Rivnay and Swirski) comb, nov., Typhlodromus montforti (Rivnay and Swirski) comb. nov., T. elisae Schicha and McMurtry, T. spaini Collyer, T. cassiniae Collyer, T. steveni Schicha, T. myopori Collyer, T. steeli Schicha and McMurtry, T. cottieri Collyer, T. dachanti Collyer, T. novaezealandiae Collyer, T. manukae Collyer, T. glenfieldensis Schicha, T. oleariae Collyer, T. corrugatus Schicha, Typhlodromus ashleyae sp.nov., T. armidalensis Schicha and Elshafie, and T. nesbitti Womersley. Heteroseiulus aceris Lehman is synonymized with T. aceri, Typhloctonus prunus Denmark and Rather with T. transitans, and Seiulus sexapori Karg and Edland with T. tuberculatus. Shiehia multispinosa Tseng and Typhloctonus vollsella Chaudhri are proposed provisionally as junior synonyms of T. comptus and T. transitans, respectively. Four genera, Neoseiulella Muma, Typhloctonus Muma, Pegodromus Athias-Henriot and Fauvel, and Heteroseiulus Lehman are designated as new junior synonyms of the genus Typhlodromus and one genus, Shiehia Tseng, as a provisional junior synonym. Most species in this group are recorded from temperate climates; 16 of the 26 recorded species are limited to the Australian faunal region. Various generic concepts relating to the species in the tiliarum group are reviewed and the general characters of the group are described. A key, descriptions, and illustrations for adult females of each species are provided.

Descriptions of two unusual new species in the genus Amblyseius Berlese (Acari: Phytoseiidae)

Two unusual new species of Amblyseius, Amblyseius tanzaniensis and Amblyseius urquharti, are described. Amblyseius tanzaniensis is unique among phytoseiid species because of the combination of having seta J1 on the opisthoscutum and having both sublateral setae r3 and R1 inserted on the dorsal shield instead of on the lateral integument. Amblyseius urquharti is one of a few species having seta ZV1 inserted on the ventrianal shield instead of on the surrounding integument. Both species were collected in tropical areas: A. tanzaniensis from Tanzania and A. urquharti from Antigua. Descriptions, figures, and comparisons with similar species are provided for each species.

A new species of eastmanosteid arthrodire (Pisces: Placodermi) from Gogo, Western Australia

A new species of Eastmanosteus Obruchev is described from the Upper Devonian Gogo Formation of Western Australia as E. calliaspis sp. nov. It is at the pachyosteomorph level of organization having no contact between the plates of the flank and those of the ventral shield behind the pectoral fin. Well preserved material of the parasphenoid and scapulocoracoid throws further light on the structure of these elements in arthrodires. The genus Eastmanosteus is reviewed.

Neozygites acaridis (Petch) comb. nov.: An entomophthoran pathogen of the mite, Macrocheles peregrinus, in Australia

Empusa acaridis is redescribed from the mite, Macrocheles peregrinus . Infected mites presented a striking appearance, with white fungal outgrowth appearing as a band between the dorsal and ventral shields mainly on the posterior end of the body. The paucinucleate, unitunicate conidia measured 19.8 x 15.4 μm and were formed on simple conidiophores. The verrucose resting spores were darkly pigmented, measuring 16.7μm diam, and appear to form by budding from two spherical hyphal bodies. The taxonomic position of the fungus is discussed and the new combination Neozygites acaridis (Petch) Milner is proposed.

Two new species ofDemonax(Sabellidae: Polychaeta) from Liverpool Bay

Demonax cambrensis sp. nov. resembles the east Pacific Demonax medius (Bush), but is thinner though just as long and has less than 15 axial cells in a radiole cross section. Demonax torulis sp. nov. resembles Demonax japonicus (Moore) in having thoracic tori so small that they do not indent the ventral shields, but differs in having broad-hooded inferior thoracic setae. Both benefit by enrichment of the sediment with sewage sludge.

A pachyosteomorph arthrodire from Gogo, Western Australia

A new monotypic genus of eubrachythoracid arthrodire is described from die Upper Devonian Gogo Formation of Western Australia as Incisoscutum ritchiei gen. et sp. nov. It is at die pachyosteomorph level of organization, having no contact between the plates of die flank and those of the ventral shield behind the pectoral fin. It is interchangeable widi Coccosteus spp. and a number of earlier described Gogo forms in a sketch dadogram for arthrodires, but its phylogenedc relationships are unknown. Well preserved material of die scapulocoracoid throws new light on die structure of this element in arthrodires, particularly widi respect to variations in die pattern of canals and foramina.

MINERAL REGENERATION BY SERPULID POLYCHAETE WORMS

1. The tubes of H. brachyacantha and E. dianthus contained two polymorphs of calcium carbonate, high magnesium calcite and aragonite, whereas the mineral regenerate produced by both species contained only aragonite. The site of initial appearance of the mineral regenerate over the openings of the calcium-secreting glands and the presence of aragonite in the duct of the calcium-secreting gland of E. dianthus indicate that the aragonite of the mineral regenerate and probably also of the tube is secreted by the calcium-secreting glands. The high magnesium calcite fraction of the tube is probably secreted by the ventral shield epithelium.2. At all salinities in which worms were able to produce mineral regenerate the rate of mineral regenerate production was extremely variable.3. Both species of serpulids failed to produce mineral regenerate below a salinity of about 20‰. Above this salinity the rate of mineral regenerate production increased with increasing salinity and environmental calcium concentration. Ho...

A REVISION OF NOSOMMA MONSTROSUM (NUTTALL AND WARBURTON, 1908) IXODOIDEA: IXODIDAE.

Nosomma monstrosum was originally described from a male specimen under the name of Hyalomma monstrosum by Nuttall & Warburton (1908), and the female was described some ten years later by Warburton (1918). Three other males were also seen by him at this time, and he was somewhat hesitant to assign these ticks to the genus Hyalomma. The genus Nosomma was proposed by Schulze (1919) to accommodate this monotypic species, but this appears to have been done without seeing the species and his reasons for establishing the genus appear to be insufficient. Chodziesner (1924) and Sharif (1928) concur on the validity of the genus and the latter defines the genus as follows: ‘eyes flat, scutum, legs and dorsal surface of the capitulum ornate, festoons present, palps short and broad, basis rectangular dorsally in both sexes, coxae I bifid, other coxae with two short spurs on each, ventral shields in the male represented by adanal, accessory and trilobed subanal shields; spiracles short, comma-shaped in the male and subtriangular in the female’. Delpy (1936) agreed in the separation of Cosmiomma and Nosomma from Hyalomma, and in respect of Nosomma stated that ‘Caractérisé par des palpes dont l'article III est plus large que long et par des ecussons subanaux tres volumineux’. Generic status was also accepted by Toumanoff (1944) and Santos Dias (1954).

A New Subfamily, Macroseiinae Nov., of the Family Phytoseiidae (Acarina: Gamasina)

Baker and Wharton (1952) elevated the Phytoseiidae, formerly a subfamily in the Laelaptidae, to family rank and included two subfamilies: the Phytoseiinae and the Podocininae. Evans (1957) subsequently elevated the latter to family rank also, leaving only the subfamily Phytoseiinae in the Phytoseiidae.Both Evans (1958) and Chant (in press) characterized the Phytoseiidae as having a two-tined palpal claw, a single dorsal shield in the adult, not more than 21 pairs of setae on the dorsal shield, and a ventrianal shield, or remnant thereof, in the adults of both sexes. One of the present authors (H.A.D.) recently collected specimens of a mite that has this combination of characters except that the dorsal shield of the adults is divided into two sub-equal parts instead of being single. Most of the features of this mite indicate that it cannot reasonably be separated from the Phytoseiidae and that the presence of two dorsal shields justifies the erection of a new subfamily, described below.

Appendix III.—Note On A New Cyathaspidian Fish From The Upper Downtonian Of Corvedale

The fragments of a Cyathaspidian fish from the Upper Downtonian of Corvedale are remarkable for their peculiar external ornamentation, which necessitates their reference to a new genus, Corvaspis . Closely arranged, smooth, and nearly uniform ridges of dentine (cosmine), as usual, cover the greater portion of shield; but a irregular network of fine grooves divides this ridge-ornament into small areas which have the false appearance of separate plates. Round the periphery, at least of the ventral shield, the smooth dentine forms a dense cluster of tubercles, which are very irregular in size and shape. The most important specimen shows the anterior two-thirds of a ventral shield, which must originally have measured about 3.5 cm. in maximum width and between 5 and 6 cm. in total length. It is broken sharply across behind, and its anterolateral margins are a little imperfect; but its anterior end is clearly hollowed by a rounded excavation. Its lateral borders are flattened, but the greater part of the shield is slightly convex from side to side. Its external ornament is especially well seen in a cellulose impression of the surface prepared by Professor L. J. Wills (PI. XIX, fig. 1). The longitudinal ridges of dentine, though subdivided into short lengths by the network of grooves, are otherwise little disturbed. In general they remain parallel and uniform in width, without any tendency to become concentric with the borders of the several areas. These areas are very irregular, without bilateral symmetry in their arrangement; and the largest are at