A modified thermal convection drying technique for herbarium preservation

A simple and efficient installation for drying plants that is both rapid and preserves colour, and which works on the principle of autonomous thermal convection, is presented. The described apparatus offers significant advantages including: uniform heat distribution and short drying times; a system for applying pressure to prevent shrinkage, which uses polyurethane foam sheets and elastic straps; a compact, space-saving system suitable for field or laboratory applications; absorbent materials which can be re-used immediately; ability to run off differing power supplies (110/220 V) and to use infra-red lamps of varying specifications; low cost and ease of use.     

Bluetongue epidemiology in the Caribbean region: serological and entomological evidence from a pilot study in Barbados

Variation in the percentage of lambs seroconverting to bluetongue viruses was seen between sites and years in Barbados. Transmission at some sites was nearly absent whereas all lambs at one site became seropositive. The agar gel immunodiffusion test for bluetongue gave consistent results in series of serum samples from 112 of 121 sentinel lambs. Collections of biting midges in association with sheep yielded six species: Culicoides insignis Lutz, C. pusillus Lutz, C. phlebotomus (Williston), C. furens (Poey), C. jamaicensis Edwards and C. trilineatus Fox. The first two species comprised 92% of those caught during a sentinel lamb study and were the predominant species trapped for virus isolation. No viruses were recovered from 5517 C. insignis, 614 C. pusillus, three C. trilineatus and two C. furens placed into pools during two brief intensive trapping operations.     

A new crangonid shrimp, Pontocheras arafurae gen. et sp.n., from the Arafura Sea

A new genus of crangonid shrimp from the Arafura Sea is described and illustrated. Pontocheras amfurae sp.n. occurs in shallow silty waters off northern Australia. The new genus is closely related to the genus Pontocaris Bate, 1888, hut it is remarkable in the modifications of the dactyls of the fifth pereiopods, a mechanism attaching the branchiostogite to the thoracic sternites and the presence of a probable stridulating mechanism on the carpus of the third pereiopod.     

New or little-known species of exotic Tipulidae (Diptera). XIX

Four new species of Antocha, one new species of Gonomyia, two new species of Trentepohlia and one new species of Erioptera are described from stations in Sikkim and Assam. Additional illustrations of previously described species of Antocha and Trentepohlia are included.     

Elastic properties of structures in the tails of cetaceans (Phocaena and Lagenorhynchus) and their effect on the energy cost of swimming

A swimming whale must do work against hydrodynamic forces, to move its fluke through the water. In addition, it must do positive work at some stages of the swimming cycle and negative work at others, to accelerate and decelerate the fluke. The energy cost of swimming could be reduced by means of elastic elements in the tail.
A mathematical model predicts the work required of the muscles, when they have elastic compliances in series with them. It is shown that there is an optimum compliance that minimizes the energy cost of swimming, for any given ratio of peak hydrodynamic force to peak inertial force.
Anatomical measurements have been made on flukes, tail muscles and tendons of Phocaena and Lagenorhynchus . Mechanical tests have been made on the tendons, fluke and vertebral column. It is shown that the important compliances are those of the tendons, and the axial compliance of the vertebral column, and that these compliances should be regarded as being in series with the muscles.
Calculations using these data, and Lang & Daybell's (1963) observations of a Lagenorhynchus swimming at 5 m/s, seem to show that the compliances greatly exceed the optimum value for this swimming speed. They increase the energy cost of swimming, rather than decreasing it.     

The response of invertebrates to a gradient of flow reduction – an instream channel study in a New Zealand lowland river

1. The impacts of low flows on invertebrates were assessed in six experimental channels placed in a lowland stream. Each channel consisted of replicate stacked gravel‐filled baskets (buried 0–7, 8–14 and 15–21 cm deep) from which invertebrates were sampled. Samples were collected before, and 1 and 2 months after flows were reduced by varying amounts. We predicted that invertebrate communities would change most with the lowest flows that persisted longest. The effects of reduced flow on channel and intragravel‐velocities, temperature, dissolved oxygen and algal biomass were also monitored. 2. Mean velocity (17 cm s⁻¹) and depth (20 cm) were similar in all channels prior to flow reduction, but were reduced in five channels by 25% to 98%, a sixth channel serving as a control. Mean intragavel velocity prior to flow reduction (1.7 mm s⁻¹) was also reduced from 17% to 51%. Flow reduction had no effect on temperature, which ranged from 11.2 °C (night) to 19.6 °C (day). Dissolved oxygen was generally high (mean = 94% saturation) but variable (range from 50% to 145%), and did not differ between channels after flow reduction. Periphyton biomass (chlorophyll a and AFDM_algae) increased over time and was positively related to velocity after 1 month of flow reduction. After 2 months, however, this relationship reversed, with higher chlorophyll and AFDM_algae in lower velocity channels. Organic matter biomass (AFDM_total) was significantly higher in channels with lower velocities, and did not change with time. There was no relationship between AFDM_total and velocity in baskets from different depths. 3. Greater than 85% of animals were found in the upper baskets (0–7 cm deep), and flow reduction had no influence on the vertical distribution of invertebrates. After 1 month, invertebrate density had declined roughly in proportion to the magnitude of flow reduction in all channels where flows were reduced more than 25%. Densities recovered to pre‐reduction levels within 2 months. The amphipod, Paracalliope fluviatilis dominated all channels numerically prior to flow reduction, but its density declined markedly during the study. Densities of Ostracoda, Oxyethira albiceps and Cladocera increased dramatically after 2 months of flow reduction, especially in the lowest flow channels. Of the physical variables measured, chlorophyll a biomass and discharge best explained the temporal changes in the invertebrate community. 4. The effects of increased duration and magnitude of flow reduction on invertebrate communities were restricted to changes in the relative abundances of just a few taxa. Our results suggest that invertebrates in this lowland stream were resistant to the experimental flow reduction, presumably because of their broad ecological tolerances. We also found that more prolonged low flows did not result in predictable changes. This finding may have implications in terms of using hydraulic‐habitat models to set minimum flows in lowland streams if invertebrates can persist at flows much lower than their supposed optima.     

Extracellular Matrix Augments Mechanical Properties of Pseudopodia in the Carnivorous Foraminiferan Astrammina rara: Role in Prey Capture

The seemingly delicate, strand-like pseudopodia of Astrammina rara , a carnivorous benthic foraminiferan, adhere to and withstand the rigorous movements of meiofaunal prey. Previous electron microscopic studies identified two novel structures that might account for the unusual tensile properties of these pseudopodia: 1) an extensive, coiled microtubule cytoskeleton and 2) a fibrous extracellular matrix vesting the pseudopodial surface. In the present study, we found that pseudopodial networks microsurgically removed from A. rara's cell body captured Artemia metanauplii as efficiently as intact organisms, and therefore used them to test the role of microtubules and extracellular matrix components in augmenting pseudopodial strength. Agents that specifically disassemble micro-tubules (1 mM colchicine or 20 μM nocodazole) or generally disrupt pseudopodial integrity (heat, 10 mM formaldehyde, 1 mg/ml saponin) failed to inhibit prey capture. All of these treatments left the extracellular matrix intact as revealed by immunofluorescence and scanning electron microscopy. The elastic and tensile properties of the extracellular matrix, isolated by solubilization of pseudopodial cytonhsm using the nonionic detergent Triton X-100, were similar to those of intact pseudopodial networks when assayed with calibrated microneedles or a flexible rubber substrate. These observations indicate that A. rara uses a fibrous extracellular matrix to augment cytoplasmic tensile properties.     

Why Mammals Gallop

SYNOPSIS: Most mammals use symmetrical gaits (such as the trot)at moderate speeds but change to asymmetrical gaits (gallops)at high speeds. A mathematical model of quadrupedal gaits failedto show any advantage in this change: it seemed to show that,even at high speeds, there was always a symmetrical gait thatwas at least as economical as galloping. That model treatedthe back as rigid, but another model seemed to show that backmovements such as occur in galloping could only increase theenergy cost. However, metabolic measurements on horses showedthat galloping is more economical than trotting at high speeds.The explanation seems to be that kinetic energy fluctuations,due to backward and forward swinging of the legs, become verylarge at high speeds. Galloping makes it possible for kineticenergy associated with leg movements to be stored briefly asstrain energy in elastic structures in the back, and returnedin an elastic recoil. The most important of the strain energystores in the back, that have been discovered so far, is theaponeurosis of the longissimus muscle.     

Effects of Initial Size and of Shading on the Quantitative Growth of Seedlings of the Citrus Rootstock Carrizo citrange

An 18 months' analysis of the effects of shading and of initialsize on the growth of Carrizo citrange revealed large effectson growth-rates but relatively small effects on distributionof growth to leaf, stem, thorn, and root. Shade reduced the relative growth-rate in the same proportionas the average reduction in light intensity but initial sizewas without effect. The only significant effect on proportionwas a reduction of root in shade. These effects are contrasted with species effects reported earlier.