The use of time and space by male and female gerbils exploiting a pulsed resource

Foraging theory postulates that interference is a foraging cost and affects patch exploitation and activity times. One such system contains two species of seed-eating gerbils inhabiting sandy habitats in the Negev Desert of Israel. Low population densities of the dominant species allowed us to examine the interaction between males and females of the subordinate species, Gerbillus andersoni allenbyi , as a function of interference and resource renewal. We used giving-up densities (GUDs; the amount of food left in a resource patch when a forager abandons the patch) in seed trays to quantify patch use by gerbils. By placing 6 trays at each foraging station and either presenting all 6 trays at the start of the night (pulse treatment) or presenting one tray at a station 6 times per night (renewal treatment), we were able to manipulate characteristics of resource renewal. We used radio telemetry to obtain an independent assessment of activity. Male and female G. a. allenbyi differed in their timing of activity, with males beginning earlier than females and remaining active later. This was most pronounced for the pulse treatment. For the renewal treatment, female activity in trays was more intense early in the night, but thereafter male activity was more intense. At the same time, telemetry showed that males and females did not differ in their total activity in or out of trays. This suggests that males begin their activity on the renewal treatment by exploiting the richest natural patches of seeds. Only later when these are depleted do they move to dominate the renewing seed trays. Finally, females exploited stabilized sand habitats more than did males, especially during the renewal treatment. Taken together, these findings suggest that male G. a. allenbyi interfere with foraging in females, causing temporal shifts in their use of space and resources.     

Male-biased investment during chick rearing in the Griffon Vulture Gyps fulvus

Capsule: In Griffon Vultures Gyps fulvus both parents take part in all parenting tasks but males take a significantly larger part of the burden.     

Relationships between growth,population dynamics,and environmental parameters in the solitary non-zooxanthellate scleractinian coral <Emphasis Type="Italic">Caryophyllia</Emphasis><Emphasis Type="Italic">inornata</Emphasis> along a latitudinal gradient in the Mediterranean Sea

The ecology of scleractinian corals may be understood through comparisons between population demographic data and environmental parameters. Growth (growth constant and maximum size) and demographic parameters (population structure stability, instantaneous mortality rate, average age of individuals, percentage of immature individuals, age at maximum biomass, and average age of biomass) of the solitary, non-zooxanthellate, and temperate coral Caryophyllia inornata were investigated at six sites along an 8° latitudinal gradient of temperature and solar radiation (SR) on the western Italian coasts. Growth parameters were homogeneous among populations across the investigated latitudinal range. While demographic parameters were not correlated with depth temperature, populations were progressively less stable and showed a deficiency of young individuals with increasing SR, likely as a result of the lowered energetic resources due to reduced zooplankton availability. These results contrast with data from another Mediterranean non-zooxanthellate solitary coral, Leptopsammia pruvoti, investigated along the same gradient, which shows no correlation between population demography and temperature or SR.     

A study of extracellular matrix-cell adhesion peptidic epitopes related to human serum amyloid A (SAA)

Summary Serum amyloid A (SAA), an acute-phase protein, exists normally in the serum while complexed with high-density lipoprotein 3 (SAA-HDL₃). Its levels increase markedly during inflammatory diseases. The pentapeptide Tyr-Ile-Gly-Ser-Asp (YIGSR-like) and the tripeptide Arg-Gly-Asn (RGD-like), related to the cell adhesion domains of laminin and fibronectin, respectively, exist in SAA within close proximity (YIGSDKYFHARGNY; amino acid residues 29–42). A structure-function study of linear and head-to-tail cyclic peptides, related to the amino acid residues 29–42) and 70–76 (GRGAEDS) of human SAA, was performed in order to evaluate their ability to inhibit adhesion of human T-lymphocytes to surfaces coated with extracellular matrix purified from bovine corneal cells.     

Construction and characterization of an NaCl-sensitive mutant of Halomonas elongata impaired in ectoine biosynthesis

Using transposon mutagenesis we generated a salt-sensitive mutant of the halophilic eubacterium Halomonas elongata impaired in the biosynthesis of the compatible solute ectoine. HPLC determinations of the cytoplasmic solute content showed the accumulation of a biosynthetic precursor of ectoine, l-2,4-diaminobutyric acid. Ectoine and hydroxyectoine were not detectable. This mutant failed to grow in minimal medium with NaCl concentrations exceeding 4%. However, when supplemented with organic osmolytes, the ability to grow in high-salinity medium (15% and higher) was regained. We cloned and sequenced the regions flanking the transposon insertion in the H. elongata chromosome. Sequence comparisons with known proteins revealed significant similarity of the mutated gene to the l-2,4-diaminobutyric acid acetyltransferase from the ectoine biosynthetic pathway in Marinococcus halophilus. Analysis of a PCR product demonstrated that the ectoine biosynthetic genes (ectABC) follow the same order as in M. halophilus.     

Photosynthetic inorganic carbon utilization and growth of Porphyra linearis (Rhodophyta)

Photosynthetic (oxygen evolution) and growth (biomass increase) responses to ambient pH and inorganic carbon (Ci) supply were determined for Porphyralinearis grown in 0.5 L glass cylinders in the laboratory, or in 40 L fibreglass outdoor tanks with running seawater. While net photosynthetic rates were uniform at pH 6.0–8.0, dropping only at pH 8.7, growth rates were significantly affected by pH levels other than that of seawater (c. pH 8.3). In glass cylinders, weekly growth rates averaged 76% at external pH 8.0, 13% at pH 8.7 and 26% at pH 7.0. Photosynthetic O₂ evolution on a daily basis(i.e. total O₂ evolved during day time less total O₂ consumed during night time) was similar to the growth responses at all experimental pH levels, apparently due to high dark respiration rates measured at acidic pH. Weekly growth rates averaged 53% in algae grown in fibreglass tanks aerated with regular air (360 mg L_-1 CO₂) and 28% in algae grown in tanks aerated with CO₂-enriched air (750 mg L^-1 CO₂). The pH of the seawater medium in which P. linear is was grown increased slightly during the day and only rarely reached 9.0. The pH at the boundary layer of algae submerged in seawater increased in response to light reaching, about pH 8.9 within minutes, or remained unchanged for algae submerged in a CO₂-free artificial sea water medium. Photosynthesis of P. linearissaturated at Ci concentrations of seawater (K_0.5560 μM at pH 8.2) and showed low photosynthetic affinity for CO₂(K_0.5 61 μM) at pH 6.0. It is therefore concluded that P. linearisuses primarily CO₂ with HCO₃ ^- being an alternative source of Ci for photosynthesis. Its fast growth could be related to the enzyme carbonic anhydrase whose activity was detected intra- and extracellularly. This revised version was published online in August 2006 with corrections to the Cover Date.     

SARS-CoV-2 receptor binding domain fusion protein efficiently neutralizes virus infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. Currently, as dangerous mutations emerge, there is an increased demand for specific treatments for SARS-CoV-2 infected patients. The spike glycoprotein on the virus envelope binds to the angiotensin converting enzyme 2 (ACE2) on host cells through its receptor binding domain (RBD) to mediate virus entry. Thus, blocking this interaction may inhibit viral entry and consequently stop infection. Here, we generated fusion proteins composed of the extracellular portions of ACE2 and RBD fused to the Fc portion of human IgG1 (ACE2-Ig and RBD-Ig, respectively). We demonstrate that ACE2-Ig is enzymatically active and that it can be recognized by the SARS-CoV-2 RBD, independently of its enzymatic activity. We further show that RBD-Ig efficiently inhibits in-vivo SARS-CoV-2 infection better than ACE2-Ig. Mechanistically, we show that anti-spike antibody generation, ACE2 enzymatic activity, and ACE2 surface expression were not affected by RBD-Ig. Finally, we show that RBD-Ig is more efficient than ACE2-Ig at neutralizing high virus titers. We thus propose that RBD-Ig physically blocks virus infection by binding to ACE2 and that RBD-Ig should be used for the treatment of SARS-CoV-2-infected patients.     

The effects of temporal variation in soil carbon inputs on resource allocation in an annual plant

Aims Resource allocation in plants can be strongly affected by competition. Besides plant–plant interactions, terrestrial plants compete with the soil bacterial community over nutrients. Since the bacterial communities cannot synthesize their own energy sources, they are dependent on external carbon sources. Unlike the effect of overall amounts of carbon (added to the soil) on plant performance, the effect of fine scale temporal variation in soil carbon inputs on the bacterial biomass and its cascading effects on plant growth are largely unknown. We hypothesize that continuous carbon supply (small temporal variance) will result in a relatively constant bacterial biomass that will effectively compete with plants for nutrients. On the other hand, carbon pulses (large temporal variance) are expected to cause oscillations in bacterial biomass, enabling plants temporal escape from competition and possibly enabling increased growth. We thus predicted that continuous carbon supply would increase root allocation at the expense of decreased reproductive output. We also expected this effect to be noticeable only when sufficient nutrients were present in the soil.Methods Wheat plants were grown for 64 days in pots containing either sterilized or inoculated soils, with or without slow-release fertilizer, subjected to one of the following six carbon treatments: daily (1.5mg glucose), every other day (3mg glucose), 4 days (6mg glucose), 8 days (12mg glucose), 16 days (24mg glucose) and no carbon control.Important findings Remarkably, carbon pulses (every 2–16 days) led to increased reproductive allocation at the expense of decreased root allocation in plants growing in inoculated soils. Consistent with our prediction, these effects were noticeable only when sufficient nutrients were present in the soil. Furthermore, soil inoculation in plants subjected to low nutrient availability resulted in decreased total plant biomass. We interpret this to mean that when the amount of available nutrients is low, these nutrients are mainly used by the bacterial community. Our results show that temporal variation in soil carbon inputs may play an important role in aboveground–belowground interactions, affecting plant resource allocation.     

Comparative oogenesis in cardinal fishes (Apogonidae,Perciformes), with special focus on the adaptive structures of the egg envelopes

The present study compares gonad structure and oogenesis in 30 species of cardinal fish (Apogonidae) from the Indo-Pacific region. In all of the species studied the ovaries are bilobed, with each lobe possessing ovigerous lamellae whose numbers and dimensions increase concomitantly with growth of the fish and reproductive stage, and correlate with the total dimensions of the particular species. In species of the genus Siphamia, the ovarian lobes are associated with a fat body that is not found in species of the other genera studied. Some of the species studied (Siphamia spp.; Archamia spp.) demonstrate group-synchronized maturation of eggs, possibly with only one spawn per reproduction season. However, most of the Apogon spp., and other genera, have unsynchronized cycles, a characteristic of multiple spawners. The various stages of previtellogenic and vitellogenic development are similar in the different species, but differ in timing and dimensions of the oocytes around which the morphogenesis of the egg envelope (chorion) and follicle begins. Differentiation of the egg envelope and follicle cells parallels the vitellogenic stages of egg development. The number of eggs was found to correlate positively with the length of the body and ovary of the fish, whereas egg diameter was found to correlate negatively with body length. The surface of the egg envelope bears ridges that form patterns of various types, whose structures and dimensions seem to be species-specific, and which in most species converge upon the single micropyle on the animal pole. The exposed ridge mazes include a special fibrous web that anchors in the micropyle. The production and importance of these ridges, as well as the correlations between egg numbers per spawn, egg dimensions, and the oral dimensions of the paternal male, are discussed.     

The effect of intra- and interspecific aggression on patch residence time in Negev Desert gerbils: a competing risk analysis

We observed patch-use behavior by two gerbil species in a fieldsetting and investigated how aggression and intrinsic decision-makinginteract to influence patch residence times. Results were interpretedby using a competing risk analysis model, which uniquely enabledus to estimate the intrinsic patch-leaving decisions independentlyof external interruptions of foraging bouts by aggression. Theexperiment was conducted in two 1-ha field enclosures completelysurrounded by rodent-proof fences and included allopatric (onlyGerbillus andersoni allenbyi) and sympatric (G. a. allenbyiand G. pyramidum) treatments. We predicted that increased foodpatch quality (i.e., habitat quality) should decrease intrinsicpatch-leaving rates and increase rates of aggressive interactionsinvolving the forager feeding in the patch (i.e., the occupantindividual). We also anticipated that increasing populationdensity should result in an increase in the rate of aggressiveinteractions involving the occupant individual. Our resultssupported the first two predictions, indicating a trade-offbetween foraging and aggression. However, the third predictionwas realized only for G. a. allenbyi in allopatry. Furthermore,in allopatry, occupant G. a. allenbyi individuals with highcompetitive ranks were involved in aggressive interactions atlower rates than those with low competitive ranks. However,in sympatry, patch-use behavior of occupant G. a. allenbyi individualswas mainly influenced by aggressive behavior of G. pyramidum,which did not respond to their competitive rank. Thus, it shouldpay less for G. a. allenbyi to be aggressive in sympatric populations.The observed reduction in intraspecific aggression among individualG. a. allenbyi in the presence of G. pyramidum supports thisassertion. We suggest that this reduction likely weakens thenegative effect of intra- and interspecific density on the percapita growth rate of G. a. allenbyi. Because this would changethe slope of the isocline of G. a. allenbyi, it could be animportant mechanism promoting coexistence when habitat selectionis constrained.