Flocking and predator surveillance in house sparrows: Test of an hypothesis

The argument that individuals benefit from foraging in flocks through spending less time in predator surveillance and hence more time foraging and feeding, has been formalized in terms of a mathermatical relationship (Pulliam 1973). We have tested the model using house sparrows (Passer domesticus), and our results support its prediction of an inverse relationship between the time spent in predator surveillance and the flock size. The data did not fit the model exactly, and we attribute this to an unrealistic assumption.     

A new species of Grillotia Guiart, 1927 (Cestoda: Trypanorhyncha) from the spotted skate,Raja straeleni Poll,in South Africa

A new species of Grillotia Guiart, 1927 was recovered from the spotted skate (Raja straeleni Poll) from the south coast of the Western Cape, South Africa. Grillotia sasciae n. sp. is described based on morphological and molecular data. This species most closely resembles species in the subgenus Grillotia (viz., Grillotia borealis Keeney and Campbell, 2001, Grillotia brayi Beveridge and Campbell, 2007, Grillotia dollfusi Carvajal, 1971, Grillotia erinaceus Dollfus, 1969, Grillotia musculara Hart, 1936 and Grillotia patagonica Menoret and Ivanov, 2012) in having four hooks per principal row and intercalary hook rows in the metabasal region of the tentacular armature, a band of hooks on the external tentacular surface, numerous proglottids, and the presence of an uterine pore, a hermaphroditic sac, and internal and external seminal vesicles. The molecular phylogenetic analysis of the partial 28S rDNA gene, confirms the morphological data as it also groups Grillotia sasciae n. sp. within the G. erinaceus species complex. Grillotia sasciae n. sp. is distinctive among all other valid species in the complex by having two enlarged, uncinate hooks in the basal armature, of a different shape and size from the remaining hooks 1(1′) in the metabasal armature. In addition, the retractor muscle of Grillotia sasciae n. sp. attaches at the posterior region of the tentacular bulb rather than the middle portion, continuing posteriorly as seen in most congeners (viz., G. erinaceus, G. borealis, G. brayi, G. musculara and G. pantagonica). The new species is the seventh species within the subgenus Grillotia and the first record of a species of Grillotia from southern African waters.     

Formation of the ventral hooks on the sperm head of the plains mouse,Pseudomys australis

The sperm head of the plains mouse, Pseudomys australis, has three curved hooks projecting from its anterior margin. The two ventral hooks have previously been shown to consist largely of an extension of the subacrosomal material. To characterize further the structure and composition of the ventral hooks, we have examined their formation during spermiogenesis using transmission electron microscopy, silver staining, and actin localization with NBD-phallacidin. The ventral hooks develop as an extension of the perinuclear space and postacrosomal dense lamina on the anteroventral margin of the sperm head. Bundles of 6-nm-thick filaments appear in the core of each hook; these are probably actin filaments based on staining of the hooks with NBD-phallacidin. Just prior to spermiation, electron-dense material condenses in the core of the ventral hooks and concurrently in the perinuclear space in the remainder of the sperm head. The two ventral hooks thus appear to consist of a core of perinuclear material and actin filaments, which is enclosed by a continuation of the postacrosomal dense lamina.     

Functional Analysis of the Larval Feeding Circuit in Drosophila

The serotonergic feeding circuit in Drosophila melanogaster larvae can be used to investigate neuronal substrates of critical importance during the development of the circuit. Using the functional output of the circuit, feeding, changes in the neuronal architecture of the stomatogastric system can be visualized. Feeding behavior can be recorded by observing the rate of retraction of the mouth hooks, which receive innervation from the brain. Locomotor behavior is used as a physiological control for feeding, since larvae use their mouth hooks to traverse across an agar substrate. Changes in feeding behavior can be correlated with the axonal architecture of the neurites innervating the gut. Using immunohistochemistry it is possible to visualize and quantitate these changes. Improper handling of the larvae during behavior paradigms can alter data as they are very sensitive to manipulations. Proper imaging of the neurite architecture innervating the gut is critical for precise quantitation of number and size of varicosities as well as the extent of branch nodes. Analysis of most circuits allow only for visualization of neurite architecture or behavioral effects; however, this model allows one to correlate the functional output of the circuit with the impairments in neuronal architecture.     

Effect of the Hypocotyl Hook on Chlorophyll Accumulation in Excised Cotyledons of Cucumis sativus L

Hypocotyl hooks have been shown to influence greening in excised cucumber (Cucumis sativus) cotyledons. The properties of the lag phase are greatly affected by the presence or absence of the hook tissue. A 45-second light pretreatment followed by 4 hours of darkness is sufficient to remove the lag phase from cotyledons with hooks, while hookless cotyledons require 2 hours of continuous illumination followed by 1 hour of dark incubation to break the lag phase. The effect of hooks on cotyledon greening is enhanced if the hooks are shielded from light. Cutting off the hooks after lag phase removal caused a marked decrease in chlorophyll accumulation in the cotyledons. These observations may indicate that the hypocotyl hooks produce a substance or substances needed in the greening process, which are translocated to the cotyledons. Indoleacetic acid, abscisic acid, gibberellin A₃, 6-benzylamino purine and δ-aminolevulinic acid do not show any activity; on the other hand, ethylene appears to replace partially the hypocotyl hooks.     

The bothridial hooks of Acanthobothrium quadripartitum Williams, 1968 (Cestoda: Tetraphyllidea): Their growth and use in taxonomy

McVicar A. H. 1977. The bothridial hooks of Acanthobothrium quadripartitum Williams, 1968 (Cestoda: Tetraphyllidea): their growth and use in taxonomy. International Journal for Parasitology7: 439–442. Bothridial hooks are absent from juvenile Acanthobothrium quadripartitum in Raja naevus but develop to full size before there is much growth of the bothridia and strobila. There is a linear relationship between the lengths of the different components of the hooks during their development and it is suggested that the ratios of these lengths to the total hook length may be useful parameters in dstinguishing between species of Acanthobothrium. Principal component analysis of published hook dimensions gave good separation of most species of Acanthobothrium.     

Development of secondary sexual characters and their relationship to ontogeny and seasonal reproductive period in Hyphessobrycon igneus (Ostariophysi: Characiformes)

Sexual dimorphism in size, anal‐fin shape and coloration of Hyphessobrycon igneus, Characidae, were examined. Males were more frequent at larger body sizes, confirming body size as a sexually dimorphic trait. Anal‐fin shape and the colour of all fins were the same for females and juveniles, differing only in adult males. Likewise, only adult males had bony hooks on fin rays; larger and more sexually mature males had the most numerous and developed hooks and hooks were most developed in degree and number during peak reproductive periods. Fin hooks regressed in number and developmental degree after the reproductive period, but restarted development with the beginning of the new reproductive period without completely disappearing. Results show that bony hooks have a development and regression cycle related to reproductive seasonality.     

Seabird bycatch in the Southwest Atlantic: interaction with the Uruguayan pelagic longline fishery

This paper analyzes the spatiotemporal variation and the causes of seabird bycatch by the Uruguayan pelagic longline fleet in a region of the Atlantic Ocean where the world’s highest historical rates of seabird bycatch were recorded. The study is based on data obtained by the Uruguayan Observers Program in 29 trips, conducted from 1998 to 2004, totalling about 648,000 hooks. The bird capture per unit of effort (BCPUE) for the studied period was 0.42 birds/1,000 hooks. The highest BCPUE values were recorded in the period May–November. Three zones were identified, with BCPUEs of 2.50 birds/1,000 hooks (very high); 0.78 birds/1,000 hooks (high) and 0.04 birds/1,000 hooks (low). Though these BCPUE values are lower than those historically reported, some are still high in global terms. Night setting was found to be effective in reducing seabird bycatch, but it is necessary to implement additional measures as seabirds have access to bait also by night, especially during the more luminous moon phases.     

Two new species of Macrobothridium (Cestoda: Diphyllidea) from rhinobatid elasmobranchs in the Gulf of Gabès, Tunisia, with notes on the status of the genus.

As a result of an investigation of metazoan parasites of elasmobranch fishes in the Gulf of Gabès, Tunisia, we discovered 2 new species of diphyllidean cestodes. Macrobothridium euterpes n. sp. is described from the spiral intestine of Rhinobatos rhinobatos, and Macrobothridium syrtensis n. sp. from the spiral intestine of Rhinobatos cemiculus. Macrobothridium euterpes is distinguished from the only other species in the genus (Macrobothridium rhynchobati) by the number of rostellar hooks, size, genital pore position, vagina position, and ovary shape. Macrobothridium syrtensis is distinguished from M. rhynchobati by the hook morphology, testis number, and overall size, and from M. euterpes by the number of rostellar hooks, testis number, genital pore position, vagina position, and ovary shape. These are the first 2 species added to the genus since its establishment in 1989. A standardized formula for representing the number and arrangement of rostellar hooks in diphyllidean species is presented.     

Morphological and molecular data reveal a new species of Neoechinorhynchus (Acanthocephala: Neoechinorhynchidae) from Dormitator maculatus in the Gulf of Mexico

Neoechinorhynchus (Neoechinorhynchus) mexicoensis sp. n. is described from the intestine of Dormitator maculatus (Bloch 1792) collected in 5 coastal localities from the Gulf of Mexico. The new species is mainly distinguished from the other 33 described species of Neoechinorhynchus from the Americas associated with freshwater, marine and brackish fishes by having smaller middle and posterior hooks and possessing a small proboscis with three rows of six hooks each, apical hooks longer than other hooks and extending to the same level as the posterior hooks, 1 giant nucleus in the ventral body wall and females with eggs longer than other congeneric species. Sequences of the internal transcribed spacer (ITS) and the large subunit (LSU) of ribosomal DNA including the domain D2 + D3 were used independently to corroborate the morphological distinction among the new species and other congeneric species associated with freshwater and brackish water fish from Mexico. The genetic divergence estimated among congeneric species ranged from 7.34 to 44% for ITS and from 1.65 to 32.9% for LSU. Maximum likelihood and Bayesian inference analyses with each dataset showed that the 25 specimens analyzed from 5 localities of the coast of the Gulf of Mexico parasitizing D. maculatus represent an independent clade with strong bootstrap support and posterior probabilities. The morphological evidence, plus the monophyly in the phylogenetic analyses, indicates that the acanthocephalans collected from intestine of D. maculatus from the Gulf of Mexico represent a new species, herein named N. (N.) mexicoensis sp. n.     

A comparative study of the structure of the oncomiracidia of the monogenean gill parasites Diclidophora merlangi,D. luscae and D. denticulata

The structure of the oncomiracidia of gill parasites Diclidophora merlangi, D. luscae and D. denticulata is described. The three larvae differ in body length and in the size and arrangement of the hooks but the glandular components and excretory systems are similar. There is some evidence that glandular secretions aid hatching. In newly hatched larvae of D. merlangi marginal hook III is displaced and a pouch of tissue occurs between hooks II and IV. The pouches are presumptive clamp tissue. Many larvae fail to hatch in vitro but form one pair of clamps while within the egg capsule.     

Flagellar hook structures of Caulobacter and Salmonella and their relationship to filament structure

Native flagellar hooks from a polarly flagellated bacterium, Caulobacter crescentus, and polyhooks from a peritrichously flagellated bacterium, Salmonella typhimurium. have been studied by densitometry of electron micrographs of negatively stained specimens, followed by computerized Fourier analysis and three-dimensional reconstruction. The two structures are remarkably similar. In both cases, the subunits are arranged along a right-handed basic helix of 2.3 nm pitch with successive subunits separated by an azimuthal angle of 64 to 65 °, and there is a pronounced system of continuous 6-start grooves and ridges on the surface of the structures. The subunit of Salmonella (M_r 42,000, versus 70,000 for Caulobacter) is somewhat thinner and yields a smaller overall hook diameter. The “bent finger” subunit shape and orientation in both cases suggests that the hook could bend readily by a sliding motion in the 11-start direction at inner radii, with the 6-start groove preventing collision at outer radii. The basic helical pitch of the Salmonella hook structure, and the number of subunits per basic helical turn (5.56) makes it highly compatible with the Salmonella flagellar filament (2.6 nm pitch. 5.51 subunits per turn); so also does the elongated shape and tilt angle of the hook and flagellin subunits in the respective structures. The two structures may therefore conjoin directly in the intact flagellum, although participation of a minor protein is not ruled out by the data.     

Mitigating Seabird Bycatch during Hauling by Pelagic Longline Vessels

Bycatch in longline fisheries threatens the viability of some seabird populations. The Hawaii longline swordfish fishery reduced seabird captures by an order of magnitude primarily through mitigating bycatch during setting. Now, 75% of captures occur during hauling. We fit observer data to a generalized additive regression model with mixed effects to determine the significance of the effect of various factors on the standardized seabird haul catch rate. Density of albatrosses attending vessels during hauling, leader length and year had largest model effects. The standardized haul catch rate significantly increased with increased albatross density during hauling. The standardized catch rate was significantly higher the longer the leader: shorter leaders place weighted swivels closer to hooks, reducing the likelihood of baited hooks becoming available to surface-scavenging albatrosses. There was a significant linear increasing temporal trend in the standardized catch rate, possibly partly due to an observed increasing temporal trend in the local abundance of albatrosses attending vessels during hauling. Swivel weight, Beaufort scale and season were also significant but smaller model effects. Most (81%) haul captures were on branchlines actively being retrieved. Future haul mitigation research should therefore focus on reducing bird access to hooks as crew coil branchlines, including methods identified here of shorter leaders and heavier swivels, and other potentially effective methods, including faster branchline coiling and shielding the area where hooks becomes accessible. The proportion of Laysan albatross (Phoebastria immutabilis) captures that occurred during hauling was significantly, 1.6 times, higher than for black-footed albatrosses (P. nigripes), perhaps due to differences in the time of day of foraging and in daytime scavenging competitiveness; mitigating haul bycatch would therefore be a larger benefit to Laysans. Locally, findings identify opportunities to nearly eliminate seabird bycatch. Globally, findings fill a gap in knowledge of methods to mitigate seabird bycatch during pelagic longline hauling.     

Design and evaluation of the crimping of a hooked self-expandable caval valve stent for the treatment of tricuspid regurgitation

To design a hooked self-expandable caval valve stent and determine the best crimping scenario for its percutaneous implantation in the Superior and Inferior Vena Cava (SVC & IVC) for the treatment of tricuspid regurgitation (TR). A hooked, Nitinol based stent design was modeled using SOLIDWORKS and finite element analysis (FEA) was carried out using ABAQUS. The Nitinol material used in this study was modeled in ABAQUS as superelastic-plastic. Two cases were simulated. In case A, the stent model was crimped to 18?F by compressing the stent main body and then: (i) bending both the proximal and distal hooks; (ii) straightening the proximal hooks and bending the distal hooks. In case B, the stent model was crimped to 18?F by: (i) bending the proximal and distal hooks and then compressing the stent main body; (ii) straightening the proximal hooks and bending the distal hooks and then compressing the stent main body. The maximum strain after crimping was used to evaluate the best crimping scenario. Hook straightening produced strains of 10.7% and 10.96% as opposed to 12.6% and 13.0% produced by hook bending. From comparison of results of both cases simulated, it was found that straightening the hooks gave lower strain and thus was the best crimping procedure. The analysis performed in this paper may help understand the critical issue of crimpability of the new stent design. The best crimping scenario can be found based on finite element modeling and simulation. Identifying the best crimping way will also help the design team to optimize the delivery system that will eventually be used to deploy this caval valve stent.     

Three-dimensional reconstruction of the flagellar hook from Caulobacter crescentus

The structure of the bacterial flagellar hook produced by a mutant of Caulobacter crescentus was studied by electron microscopy, optical diffraction, and digital image processing techniques. The helical surface lattice of the hook is defined by a single, right-handed genetic helix having a pitch of about 23 Å, an axial rise per subunit of 4 Å and an azimuthal angle between subunits of 64·5 °. The lattice is also characterized by intersecting families of 5-start, 6-start and long-pitch 11-start helices. These helical parameters are remarkably similar to those determined for the flagellar filaments from several strains of gram-negative bacteria. The technique of three-dimensional image reconstruction (DeRosier & Klug, 1968) was applied to nine of the better preserved specimens and the diffraction data from five of these were correlated and averaged and used to generate an average three-dimensional model of the hook. The pattern of density modulations in the three-dimensional model is suggestive of an elongated, curved shape for the hook subunit (100 Å × 25 Å × 25 Å). The subunits are situated in the lattice of the polyhook such that their long axes are tilted about 45 ° with respect to the hook axis. The subunits appear to make contact with each other along the 6-start helices at a radius of 80 Å and also along the 11-start helices at a radius of 65 Å. Few structural features are revealed at radii between 15 å and 45 Å and, therefore, we are unable to decide to what extent the hook subunits extend into this region. The most striking characteristic of the model is the presence of deep, broad, continuous 6-start helical grooves extending from an inner radius of about 50 Å to the perimeter of the particle at 105 Å radius. Normal hooks usually appear curved in electron micrographs and sometimes so are the mutant hooks; the prominent 6-start grooves appear to allow for bending with minimal distortion of matter in the outer regions of the hook. A round stain-filled channel about 25 Å in diameter runs down the center of the polyhook. Such a channel supports a model for flagellar assembly in which flagellin subunits travel through the interior of the flagellum to the growing distal end of the filament.     

Distribution and food habits of the slender smoothhound,Gollum attenuatus,from the waters around New Zealand

Three hundred and seventy-three females and 385 malesof Gollum attenuatus were caught with bottom longlines from the Challenger Plateau, Wanganella Bank and Three Kings Ridge around New Zealand. The sharks ranged in size from 440 to 1092 mm TL for females and 442 to 1067 mm TL for males. Catch rates (number of fish per 100 hooks) were 0.41 for the Challenger Plateau, 0.14 for the Wanganella Bank, and 4.52 for the Three Kings Ridge. The sex ratio was 1:1. In terms of 100-m depth intervals,G. attenuatus was most abundant in 500 to 599 m depths. There was a marked decrease in catch rates with increased distance of the hooks from the bottom. Stomachs contained such varied items as sharks, teleost fishes, gastropods, squids, octopi, decapods, isopods, brittle stars, and human garbage. The data in this study suggest thatG. attenuatus consumed, in order of importance, fishes and crustaceans.