Cage Wall Research Articles

Synthesis of macro-mesoporous alumina with yeast cell as bio-template

Macro-mesoporous alumina materials were synthesized by using yeast cell as bio-template and triethanolamine (TEA) as precipitator. The synthesized samples were characterized by various means such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption method and X-ray diffraction (XRD). The effect of both the mass ratio of yeast/Al(NO3)3·9H2O and the synthesized temperature on the properties of samples was investigated in detail. The SEM and TEM results showed that the synthesized alumina possessed macroporous structure with sizes of 1.5–3μm, where the interconnected wormlike mesopores with sizes of 3–4.5nm were within the walls of the macroporous cages. XRD patterns and BET results revealed that the synthesized alumina had a higher formation temperature of γ-Al2O3 crystal phase, as well as better thermal stability.

AC Conductors' Corona-Loss Calculation and Analysis in Corona Cage

Corona loss generated from conductors is one of the important design factors of extremely high-voltage ultra-high voltage (EHV/UHV) ac transmission lines. The charge simulation method was adopted to calculate conductor corona loss in the corona cage. Every corona cage wall is equivalent to the ground plane and, therefore, the calculation model is more complicated than the power-line model above the ground surface. Two corona cages-UHV corona cage and small corona cage-were adopted in the tests. The cages are both square sections. Single conductors and bundle conductors were tested in the corona cages to verify the corona cage calculation model. And the same type of conductor was tested in the small corona cage and in the UHV corona cage to check the measuring system and the simulation program of corona loss further. Since the artificial rain rates were from 12 to 20 mm/h, corona losses were measured and calculated. The results indicate that the fundamental frequency component is the most main component of corona loss. The corona cage corona-loss calculation model is appropriate. And for single conductor LGJ-500/35 and bundle conductors, 8 LGJ-500/35, under heavy rain conditions, with the rain rate being from 12 to 20 mm/h, the roughness coefficient range is from 0.4 to 0.5 approximately.

Hierarchically ordered meso/macroporous γ-alumina for enhanced hydrodesulfurization performance

The facile synthesis of three-dimensionally ordered macroporous (3DOM) γ-alumina with high thermal stability and the performance test in hydrodesulfurization (HDS) of dibenzothiophene (DBT) were investigated. The synthesis strategy in this work is based on a sol–gel process using a colloidal crystal template method in which a triblock copolymer F127 is employed as the mesoporous structure-directing agent. The as-prepared samples were characterized by means of techniques such as thermogravimetric analysis, XRD measurement, nitrogen adsorption and desorption, SEM and TEM investigations. These results showed that all the synthesized alumina samples possess a highly ordered macroporous structure. The sample calcined at 800°C with a surface area of 79m2g−1 exhibited the ordered mesopores within the walls of the macroporous cages. The co-existence of the interconnected macroporous and mesoporous structure of the prepared γ-alumina enables it to be an effective catalyst support with favorable accessibility of the reactants to the active sites. HDS of DBT was chosen to test the catalytic performance of the 3DOM γ-alumina supported CoMo-based catalyst which displayed a higher desulfurization ratio of 98.23% in striking contrast to 70.60% with commercial mesoporous alumina support under the reaction temperature of 300°C.

QM/MM non-adiabatic decay dynamics of formamide in polar and non-polar solvents

Non-adiabatic on-the-fly dynamics simulations of the photodynamics of formamide in water and n-hexane were performed using a QM/MM approach. It was shown that steric restrictions imposed by the solvent cage do not have an influence on the initial motion which leads to the lowest energy conical intersection seam. The initial deactivation in water is faster than in n-hexane and in the gas phase. However, most of the formamide molecules in water do not reach the ground state. The reason for the deactivation inefficiency in water is traced back to a decrease of close CO···HOH and NH···OH(2) contacts which fall in the range of hydrogen bonds. The energy deposition into H-bond breaking events leaves molecules with less energy for surmounting the CN dissociation barrier. In both solvents, after hopping to the ground state, the solvent cage keeps the HCO and NH(2) fragments or CO and NH(3) products in close proximity. Consequently, the number of trajectories where fast recombination happens is augmented with delayed recombinations that start when the dissociation fragments hit the cage wall and return back. The hot ground state formamide is formed in an internal conversion process identical to the path leading to CN photodissociation. In the case of aqueous formamide, good agreement with experimental results is achieved by combining dynamics simulations starting from the S(1) and the S(2) excited states collecting high and low energy trajectories, respectively.

Modifying Cage Structures in Metal–Organic Polyhedral Frameworks for H2 Storage

Three isostructural metal-organic polyhedral cage based frameworks (denoted NOTT-113, NOTT-114 and NOTT-115) with (3,24)-connected topology have been synthesised by combining hexacarboxylate isophthalate linkers with {Cu(2)(RCOO)(4)} paddlewheels. All three frameworks have the same cuboctahedral cage structure constructed from 24 isophthalates from the ligands and 12 {Cu(2)(RCOO)(4)} paddlewheel moieties. The frameworks differ only in the functionality of the central core of the hexacarboxylate ligands with trimethylphenyl, phenylamine and triphenylamine moieties in NOTT-113, NOTT-114 and NOTT-115, respectively. Exchange of pore solvent with acetone followed by heating affords the corresponding desolvated framework materials, which show high BET surface areas of 2970, 3424 and 3394 m(2) g(-1) for NOTT-113, NOTT-114 and NOTT-115, respectively. Desolvated NOTT-113 and NOTT-114 show high total H(2) adsorption capacities of 6.7 and 6.8 wt%, respectively, at 77 K and 60 bar. Desolvated NOTT-115 has a significantly higher total H(2) uptake of 7.5 wt% under the same conditions. Analysis of the heats of adsorption (Q(st)) for H(2) reveals that with a triphenylamine moiety in the cage wall, desolvated NOTT-115 shows the highest value of Q(st) for these three materials, indicating that functionalisation of the cage walls with more aromatic rings can enhance the H(2)/framework interactions. In contrast, measurement of Q(st) reveals that the amine-substituted trisalkynylbenzene core used in NOTT-114 gives a notably lower H(2)/framework binding energy.

Clinging to royalty: Ropalidia marginata queens can employ both pheromone and aggression

Queens of the primitively eusocial wasp Ropalidia marginata are behaviourally docile and maintain their reproductive monopoly by rubbing their abdomen and applying a pheromone to the nest surface. We argued that the queen should be overthrown if she is prevented from applying her pheromone. To test this prediction we introduced the queen and her workers into a cage without the nest, thereby removing the substrate for pheromone application. Contrary to our expectation, queens maintained their status (in six out of seven experiments), by continuing to rub their abdomens (and presumably applying pheromone) to cage walls even in absence of the nest. Such attempts to apply pheromone to the cage are expected to be relatively inefficient as the surface area would be very large. Thus we found that the queens were aggressively challenged by the workers and they in turn reciprocated with aggression toward their workers. Such aggressive queen-worker interactions are almost nonexistent in natural colonies and were also not recorded in the control experiments (with nests present). Our results reinforce the idea that pheromone helps R. marginata queens maintain their status and more importantly, they also show that, if necessary, queens can also supplement the pheromone with physical aggression.

Behavioural trait covaries with immune responsiveness in a wild passerine

Immune system is highly integrated with the nervous and endocrine systems, which is thought to result in covariation between behavioural syndromes and stress- and immune-associated diseases. Very little is known about the associations between behaviour and immune traits in wild animals. Here we describe such an association in passerine birds, the greenfinches (Carduelis chloris). When wild-caught greenfinches are brought into captivity, some individuals damage their tail feathers against cage walls due to excited behaviour, while others retain their feathers in intact condition. We show that damage to tail feathers was associated with flapping flight movements and the frequency of such flapping bouts was individually consistent over 57 days. Birds with intact tails, i.e., relatively 'calm' individuals mounted stronger antibody response to a novel Brucella abortus antigen and their circulating phagocytes were capable of producing stronger oxidative burst in response to stimulation with bacterial lipopolysaccharide in vitro. As the behavioural trait was assessed 13-25 days before measuring immune responsiveness, our results demonstrate that individuals' coping styles with captivity predicted how these individuals would respond to forthcoming immune challenges. This is a novel evidence about covariation between immune responsiveness and a behavioural trait in a wild-caught animal.

Molecular dynamics simulation of replacement of CH 4 in hydrate with CO 2

Molecular dynamics simulations are used to study the mechanism of guest replacement of CH 4 hydrate with CO 2. The well-known OPLS-AA and TIP4P potential models are used for the interactions between guest–guest and water–water species, respectively. The simulations are performed on a combination of 4 × 4 × 4 unit cell replica of fully-occupied structure I hydrate and CO 2 gas phase. The simulation results confirm that CH 4 is released from its hydrate and enter into the gas phase by the replacement with CO 2, which has been testified by in situ Raman spectroscopic experiments. Without the hydrate dissociation, CH 4 molecules are difficult to run out of while CO 2 to penetrate into the interior cages of the hydrate block because of the barrier of the cage walls constructed by hydrogen-bonding network of water. It is conjectured that the replacements of CH 4 hydrate with CO 2 will spend long time without the dissociation, or at least slightly melting of the hydrate crystals once time. The replacement process may be divided into three steps: the cages are broken firstly, then CH 4 molecules run out of the cages and meanwhile CO 2 molecules enter into the void cages and occupy them in stead.

A new method to estimate energy expenditure from abdominal and rib cage distances

The aim of this paper is to validate a new method of energy expenditure (EE) estimation stemming solely from the measurement of rib cage, abdominal and chest wall distances. We set out to prove that the variations of these distances, measured by two pairs of electromagnetic coils, lead to the estimation of the ventilation (VE) and the EE. Eleven subjects were recruited to take part in this study (27.6 ± 5.4 years; 73.7 ± 9.7 kg). Each subject participated in two tests. The objective of Test 1 was to determine the individual and group equations between the VE and EE during light to moderate activities while Test 2 compared the two pairs of electromagnetic coils with the indirect calorimetry so as to estimate EE in upright sitting and standing positions and during walking exercises. During Test 2, we compared EE measured by indirect calorimetry (EE(IC-Val-REF)) with EE estimated by the two pairs of electromagnetic coils through the application of: (1) the individual equation (EE(mag-Val-INDIV)) and (2) the group equation (EE(mag-val-GROUP)). The results show that there is no significant difference between EE(IC-Val-REF) and EE(mag-Val-INDIV) and between EE(IC-Val-REF) and EE(mag-val-GROUP) for each activity. Furthermore, the mean difference seems to show that the estimation of EE is better with the group equation. In conclusion, on the proven basis of this study we are able to validate this new method which permits the estimation of EE from abdominal and rib cage distances. This study also highlights the advantage of using a group equation to the estimate EE.

Imitating trumpet shells: Möbius container molecules

Mobius container molecules C64H8, C60N4H4, and C58N6H2 with topological one-sided characteristics were constructed at the first time by imitating natural trumpet shells. The structure is an open cage with an inner hexagonal bridge. The bridge joints the outer and inner surfaces of the cage to form a new one-sided Mobius structure. The optimized structures of the three molecules in the singlet (the ground state), triplet and quintet states are obtained using the density functional theory (B3LYP). For the ground state structures of the three Mobius molecules, their oxidizabilities are weaker than that of the C60 and reducibilities are close to that of the stable C80 cage and slightly stronger than that of the C60. These may show that the unusual Mobius structures have some stability. Their potential properties were predicted, for example, the special aromaticity of the bridge ring due to the unique interaction between the bridge and the cage wall. These findings enlarge the knowledge of Mobius molecules. The idea of bionic and topological imitating in chemistry may promote the design of new complex-shaped nano-molecules and molecular devices.

Synthesis of Au and Au–CuO cubic microcages via an in situ sacrificial template approach

The controllable synthesis of hollow polyhedral hetero-structures composed of metallic and metallic–semiconductor nanograins has aroused great attention not only for the synthetic challenge, but also for the novel functions offered by their unique micro-/nanostructures. Herein, both Au and Au–CuO hierarchical heterostructured cubic microcages have been prepared using Cu2O cubes as sacrificial templates in aqueous solution. The micro-sized Au cubic cages are composed of Au nanograins about 20 nm in size with abundant pores inside the cage walls. Each individual Au–CuO hetero-structured cubic cage is assembled with both gold nanoparticles and CuO nanoneedles. A growth mechanism for the formation process of these delicate hierarchical cubic architectures is presented. Furthermore, the reflection loss (dB) spectra measured in the frequency range 2–18 GHz showed that the Au–CuO hollow hetero-structured cubic cages have an improved electromagnetic interference (EMI) shielding effectiveness (SE) compared to that of both Au hollow cubic microcages and conventional Au hollow microspheres. Moreover, these Au cages and Au–CuO cubic cages might find novel applications in sensing and catalysis due to their hierarchically assembled structures.

Protein Folding and Confinement: Inherent Structure Analysis of Chaperonin Action

A coarse-grained model of the action of a chaperonin cage of tunable hydrophobicity, h, upon a protein with the possibility of misfolding is studied with inherent structure (IS) analysis and statistical temperature molecular dynamics (STMD) simulation. Near the folding temperature, the equilibrium properties of the system may be understood in terms of <10 IS. The known phenomenon of an optimal cage hydrophobicity for productive folding, found at h = 0.25, is seen to arise from a striking suppression of the occupations of IS in the misfolding funnel, which in turn arises from a decrease in translational entropy due to confinement to the region of the cage wall. The kinetics of folding is correspondingly fastest at h = 0.25, where a minimum is found in the h-dependent barrier height. While true kinetics is determined by conventional MD, it is shown that the accelerated dynamics of STMD provide a valuable quantitative perspective.

Influence of periphyton substrates and rearing density on Liza aurata growth and production in marine nursery ponds

The main objectives of this investigation were to test the effects of (i) the presence of periphyton substrates, (ii) rearing density and (iii) supplemental feeding with dry feed on the growth and production of golden mullet ( Liza aurata) juveniles. Twenty-six 1 m 2-cages were installed in a French marine pond from April till June 2008. Mullets were stocked in cages with or without substrate at a density of 0, 20, 40 or 60 individuals per cage. Each treatment was carried out in triplicate. In addition, 20 fish were put in three tanks and fed ad libitum with dry feed. The results showed that (i) although mullets were seen to graze on periphyton substrates, their presence did not affect mullet growth and production. In future studies, meshed substrates could be attached on hard structures to improve the efficiency of mullet grazing; (ii) individual growth was higher at low density due to a lower competition for space and food. Production increased with rearing density reflecting that food availability was not limiting in control cages; (iii) growth and net yield of mullets were lower in fed tanks than in natural ponds where food seemed to be more appropriate for wild mullet juveniles and where stress factors were lower. Finally, in contrast to the individual growth rate, the net fish yield in this experiment was greater than that recorded in other extensive and semi-intensive systems. It was equivalent to yields observed in other periphyton-based systems. Periphyton developed on the meshed walls of cages probably increased the natural productivity of the pond. As part of sustainable aquaculture development, the effluents of intensive farms could be exploited to produce periphyton on inflexible substrates and to rear mullet adults, which are more herbivorous than juveniles. This type of integrated system could be developed with other mullet species, such as Chelon labrosus or Mugil cephalus, whose growth rates are higher than L. aurata. Mullet production could be exploited by the sale of fillets and dried roe.

A lightweight field cage for a large TPC prototype for the ILC

We have developed and constructed the field cage of a prototype Time Projection Chamber for research and development studies for a detector at the International Linear Collider. This prototype has an inner diameter of 72 cm and a length of 61 cm. The design of the field cage wall was optimized for a low material budget of 1.21% of a radiation length and a drift field homogeneity of ΔE/E≲10−4. Since November 2008 the prototype has been part of a comprehensive test beam setup at DESY and used as a test chamber for the development of Micro Pattern Gas Detector based readout devices.

Chaperonin-Catalyzed Rescue of Kinetically Trapped States in Protein Folding

GroEL and GroES form a chaperonin nano-cage for single protein molecules to fold in isolation. The folding properties that render a protein chaperonin dependent are not yet understood. Here, we address this question using a double mutant of the maltose-binding protein DM-MBP as a substrate. Upon spontaneous refolding, DM-MBP populates a kinetically trapped intermediate that is collapsed but structurally disordered. Introducing two long-range disulfide bonds into DM-MBP reduces the entropic folding barrier of this intermediate and strongly accelerates native state formation. Strikingly, steric confinement of the protein in the chaperonin cage mimics the kinetic effect of constraining disulfides on folding, in a manner mediated by negative charge clusters in the cage wall. These findings suggest that chaperonin dependence correlates with the tendency of proteins to populate entropically stabilized folding intermediates. The capacity to rescue proteins from such folding traps may explain the uniquely essential role of chaperonin cages within the cellular chaperone network.

Physiological and behavioural responses of laboratory rats housed at different tier levels and levels of visual contact with conspecifics and humans

Laboratory rats are typically housed in clear or opaque cages on multi-tiered racks. Clear-walled cages allow a view of the room and facilitate visual social contact with neighbouring rats but may induce anxiety due to lack of visual cover. We hypothesized that degree of visibility of humans and conspecifics affects anxiety in individually housed rats. We evaluated physiological and behavioural responses of adult male Sprague–Dawley rats ( N = 54 pairs housed in adjacent cages with the same cover treatment) to three cover levels: (1) no visual cover (clear cage walls); (2) partial cover (opaque stripes covering 60% of the wall area); (3) solid cover (100% opaque walls), and three tier levels: (1) lower; (2) middle; (3) upper, located 61, 101, and 141 cm above the floor, respectively. Chromodacryorrhea, an indicator of acute stress, was recorded following weekly body weight measurement and cage cleaning. Faecal corticosteroid, an indicator of chronic stress, was measured in Weeks 1 and 7. Behaviour during Anticipatory Reaction to Handling (ARH), Elevated Plus Maze (EPM) and Cat Odor (CAT) tests was assessed during Weeks 4 and 8. Growth rate, chromodacryorrhea, and behaviour in ARH tests were not affected by treatments. Rats housed in cages with partial cover on upper tiers tended to have lower faecal corticosteroid levels than those in clear cages on lower tiers ( P = 0.08). In the CAT test, rats housed on lower tiers spent more time rearing ( P = 0.046), and tended to make more visits to a cloth impregnated with cat odour ( P = 0.051), suggesting that they were less anxious in this context than those housed on higher tiers. Rats in cages positioned further from the main area of human activity within the housing room showed a tendency towards increased anxiety in the EPM. When individually housed for 24 h in three interconnected cages varying in cover, rats ( N = 8) spent more time resting in the opaque, than clear or partially-covered, cage units during the photoperiod ( P < 0.05), and were more likely to remain in the opaque than the clear unit when people were present ( P < 0.05), but otherwise used the three cage units equally. We found no evidence that rats preferentially used the discontinuous cover as a ‘Venetian blind’ for monitoring events outside their cage. The results confirm the value of an opaque-walled hiding/sleeping area for rat welfare, and suggest that controlling for levels of human exposure within rodent rooms could improve the external validity of biomedical research.

Classical to Nonclassical Transition of Ether−HCN Clathrate Hydrates at Low Temperature

Guest molecules of typical clathrate hydrates are stabilized by weak nonspecific interactions with the cage walls of the host lattice. Despite their ability to form hydrogen bonds, this description also generally applies to encaged ether and other moderately strong proton acceptor molecules. However, on the basis of infrared spectroscopic and molecular dynamics results, an altered structure is indicated when guests such as HCN or SO2, capable of binding to oxygen lattice sites, occupy the small cages. During cooling from 140 to 60 K, structure-II clathrate hydrates, with HCN in the small cages and either tetrahydrofuran or trimethylene oxide as the large-cage guests, convert to nonclassical structures in which most “guest” molecules establish hydrogen bonds to water. The nonclassical structure is stable at even higher temperatures for the dimethyl ether−HCN double clathrate hydrate.

Nitriding in cathodic cage of stainless steel AISI 316: Influence of sample position

Cathodic cage plasma nitriding is a new growth technique based on multiple hollow cathode effects. The samples are kept at a floating potential inside a cage that acts as a cathode and shields the samples from the cathodic potential. The aim of this work is to perform a systematic study of the properties of nitrided layers as a function of the distance from the nitriding sample surface to the cage wall using this technique. Cylindrical austenitic stainless steel AISI 316 samples were placed in different positions on an alumina plate inside the cathodic cage. The nitrided samples were characterized by optical microscopy, X-ray diffraction and microhardness measurements. The results show that the temperature inside the cage is nearly uniform and that the nitrided layers possess good physical properties and uniformity. Therefore, the differences in the nitrided layer thicknesses obtained at different positions must be due to particle flow reaching the sample surface, depending on how far the sample is from the cage walls.

Pre‐release feeding on yeast hydrolysate enhances sexual competitiveness of sterile male Queensland fruit flies in field cages

AbstractRecent laboratory studies of mass‐reared flies in small cages have found that periods of just 24‐ or 48‐h access to yeast hydrolysate can substantially enhance mating performance of mass‐reared male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (‘Q‐flies’). Using field cage tests that provide a better approximation of nature, we here investigated whether access to yeast hydrolysate for 48 h after adult emergence improves the ability of male and female mass‐reared, sterile Q‐flies to compete sexually with wild‐type flies that had been provided continuous access to yeast hydrolysate. Mating probability of sterile males was significantly increased by 48‐h access to yeast hydrolysate; sterile males provided 48‐h access to yeast hydrolysate had mating probability similar to that of wild males provided continuous access to yeast hydrolysate, whereas sterile males deprived of access to yeast hydrolysate had much lower mating probability. Unlike males, access to yeast hydrolysate for 48 h did not increase mating probability of sterile female Q‐flies. We instead found that wild females provided continuous access to yeast hydrolysate had higher mating probability than sterile females that did or did not have 48‐h access to yeast hydrolysate. This result raises the possibility that a bisexual Q‐fly strain might operate essentially as a male‐only release when the flies are given access to yeast hydrolysate during a 48‐h pre‐release holding period. Sterile males given access to yeast hydrolysate for 48 h mated significantly earlier in the evening than wild males and, as in other recent studies, this tendency was associated with an increased tendency to mate on the trees rather than the cage walls. There was no evidence of sexual isolation in this study, as wild and sterile mass‐reared flies showed no evidence of preferential mating with their own kind. Further studies are now needed to assess the potential for pre‐release access to yeast hydrolysate to improve sexual performance and longevity of sterile, mass‐reared, Q‐flies in the field.

The feeding mechanisms ofLynceus(Crustacea: Branchiopoda: Laevicaudata), with special reference toL. simiaefaciesHarding

Although generally assumed to be filter feeders, branchiopod crustaceans of the laevicaudatan genus Lynceus O.F. Muller, 1776 possess no filters and do not collect food by filtration. Investigated species of these bivalved, multi-limbed animals have basically benthic habits and collect particulate food, mostly detritus, by scraping or sweeping it from surfaces with suitably armed trunk limbs. L. simiaefacies Harding, 1941, known only from a desert pool in Yemen, has trunk limbs that are armed with particularly robust scrapers and much of the complexity of these limbs and their armature is related to the collection and manipulation of detrital food by mechanical means. Material collected by scrapers borne distally on the more anterior limbs – although the anteriormost is very lightly armed – is swept posteriorly and dorsally, assisted by the armature of the more proximal endites, towards the posterior end of a deep food groove, whence it is passed anteriorly by the substantial gnathobases of the trunk limbs. The necessary movements of the trunk limbs are facilitated by a system of intrinsic muscles that enable individual endites to be moved independently – a remarkable specialized feature of a phyllopodial appendage. Before it enters the food groove, collected material is at all times confined to a narrow median chamber, or cage, between the two sets of opposed trunk limbs that extends over most of the anterior limbs – which are the largest. Each cage wall serves as a screen, covering the limbs of its side and is made up of long setose screening setae that superficially resemble coarse filter setae, and arise from the more proximal endites of most of the anterior trunk limbs. The screens prevent collected material from entering the inter-limb spaces into which water flows during each cycle of trunk limb movements, where its presence would be disastrous. They do not interfere with the spines of the proximal endites that can protrude between them. The screens do not extend to the extreme posterior end of the trunk limb series where a complex and dense array of specialized spines of the short posterior trunk limbs completes the task of sweeping food material into the food groove. Material is passed anteriorly along the food groove by the trunk limb gnathobases and the small but robustly armed maxillules to the mandibles. Although constructed on the basic, boat-like, branchiopod plan, in contrast to those of most particle-feeding branchiopods whose mandibles have a broad masticatory surface, those of Lynceus have a masticatory surface that is narrow and elongate in the antero-posterior plane. Interestingly, while the number of ‘teeth’ into which this surface is elaborated is few in most species of the genus, inviting comparison with a similar attribute in the Notostraca, L. simiaefacies has more numerous, smaller teeth. Although following the branchiopod plan, the mandibular musculature appears to have its own distinctive features but remains to be investigated in properly fixed material. At its distal extremity the oesophagus is differentiated into a small but complex gizzard, of which there appears to be no parallel in any other branchiopod order. This is described for the first time. Although provided with natatory antennae, species of Lynceus also employ their trunk limbs as organs of propulsion. In L. gracilicornis (Packard, 1871) the carapace valves can gape to more than 90°, which allows the trunk limbs to make a contribution to propulsion in a manner akin to that of the Anostraca. In this respect the Laevicaudata appears to stand in contrast to the Spinicaudata, in most species of which the trunk limbs contribute little or nothing to locomotion. More information is needed on representatives of both orders, which have received little study as living animals. Brief comments are made on the systematic position of the Laevicaudata, about which much remains to be resolved. © 2009 The Natural History Museum. Journal compilation © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 513–541.