Sodium and potassium concentrations in floral nectars in relation to foraging by honey bees

Sodium and potassium concentrations have been measured in nectar from a variety of flowering plants visited by honey bees (Apis mellifera capensis). In 18 plant species the mean sodium concentration was 9,8 ± 1,4 mmol (± S.E.), and the mean potassium concentration was 18,7 ± 4,3 mmol. These results are compared with nectar ion concentrations in carpenter bee and hummingbird flowers. Analysis of honey bee body fluids showed that, although haemolymph ion concentrations were closely regulated, the levels of sodium and potassium in the urine did not necessarily reflect those in the nectar being gathered

Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters

Nectarivores face a constant challenge in terms of water balance, experiencing water loading or dehydration when switching between food plants or between feeding and fasting. To understand how whitebellied sunbirds and New Holland honeyeaters meet the challenges of varying preformed water load, we used the elimination of intramuscular-injected [14C]-L-glucose and 3H2O to quantify intestinal and renal water handling on diets varying in sugar concentration. Both sunbirds and honeyeaters showed significant modulation of intestinal water absorption, allowing excess water to be shunted through the intestine when on dilute diets. Despite reducing their fractional water absorption, both species showed linear increases in water flux and fractional body water turnover as water intake increased (both afternoon and morning), suggesting that the modulation of fractional water absorption was not sufficient to completely offset dietary water loads. In both species, glomerular filtration rate was independent of water gain (but was higher for the afternoon), as was renal fractional water reabsorption (measured in the afternoon). During the natural overnight fast, both sunbirds and honeyeaters arrested whole kidney function. Evaporative water loss in sunbirds was variable but correlated with water gain. Both sunbirds and honeyeaters appear to modulate intestinal water absorption as an important component of water regulation to help deal with massive preformed water loads. Shutting down glomerular filtration rate during the overnight fast is another way of saving energy for osmoregulatory function. Birds maintain osmotic balance on diets varying markedly in preformed water load by varying both intestinal water absorption and excretion through the intestine and kidneys

Sucrose digestion capacity in birds shows convergent coevolution with nectar composition across continents

The major lineages of nectar-feeding birds (hummingbirds, sunbirds, honey-eaters, flowerpiercers, and lorikeets) are considered examples of convergentevolution. We compared sucrose digestion capacity and sucrase enzymatic activ-ity per unit intestinal surface area among 50 avian species from the New World,Africa, and Australia, including 20 nectarivores. With some exceptions, nectari-vores had smaller intestinal surfaces, higher sucrose hydrolysis capacity, andgreater sucrase activity per unit intestinal area. Convergence analysis showedhigh values for sucrose hydrolysis and sucrase activity per unit intestinal surfacearea in specialist nectarivores, matching the high proportion of sucrose in thenectar of the plants they pollinate. Plants pollinated by generalist nectar-feedingbirds in the Old and New Worlds secrete nectar in which glucose and fructose arethe dominant sugars. Matching intestinal enzyme activity in birds and nectarcomposition in flowers appears to be an example of convergent coevolution be-tween plants and pollinators on an intercontinental scale.Todd J. McWhorter, Jonathan A. Rader, Jorge E. Schondube, Susan W. Nicolson, Berry Pinshow, Patricia A. Fleming, Yocelyn T. Gutie, rrez-Guerrero, and Carlos Martı, nez del Ri

The SARAO MeerKAT 1.3 GHz Galactic Plane Survey

We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251○ ≤l ≤ 358○ and 2○ ≤l ≤ 61○ at |b| ≤ 1 5). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8″ and a broadband RMS sensitivity of ∼10–20 μJy beam−1. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908–1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE H II region candidates are not true H II regions; and a large sample of previously undiscovered background H I galaxies in the Zone of Avoidance

Sex differences in space use, body condition and survivorship during the breeding season in the Namaqua rock mouse, Aethomys namaquensis

Although the determinants of sex differences in territoriality have been addressed for many species, the consequences of such differences in space use, particularly in southern hemisphere taxa, have received limited attention. The Namaqua rock mouse, Aethomys namaquensis, is a medium-sized, omnivorous, nocturnal murid with a wide distribution throughout southern Africa. Sex differences in space use behaviour were found: female captures were described by non-overlapping contiguous areas, whereas males were caught over 50% larger areas that overlapped spatially and temporally. Movements during breeding were characteristic of scramble-competition polygyny: a transient influx of non-resident males (coinciding with an increase in perforate females) skews the sex ratio towards males early in the breeding season. Whereas female condition improved with time, male body condition declined significantly over the breeding period (r262 = 0.134, P = 0.002) and males had lower persistence in the trappable population. This study may therefore document a link between mobility (associated with a polygynous mating system) and reduced male survivorship and body condition for this murine rodent

Arthropod fauna of mammal-pollinated Protea humiflora: Ants as an attractant for insectivore pollinators?

Protea humiflora Andrews inflorescences are cryptic, but strongly scented and borne close to the ground (geoflorous) for ready access by small, non-flying mammals. During a study of P. humiflora pollination, we found that insectivorous elephant shrews (Macroscelididae: Elephantulus edwardii (A. Smith)) carried higher pollen loads on their snouts than simultaneously-trapped rodent species. Elephant shrews seem to be acquiring pollen while foraging for insects in the inflorescences. Compared with the larger bird-pollinated inflorescences of P. repens (L.) L., P. humiflora inflorescences have a substantially lower mass of arthropods, relatively fewer beetles (12% of arthropod dry mass) and more ants (13%). The large numbers of ants in these inflorescences may attract insectivore pollinators, suggesting an indirect, mutualistic relationship between plant, insect and insectivore

Role of insects in the pollination of Acacia nigrescens (Fabaceae)

We examined pollination biology of Acacia nigrescens Oliver, flowering at the end of the dry season in Kruger National Park, South Africa. A. nigrescens produces small quantities of concentrated nectar, and has abundant pollen resources available to potential pollinators. We recorded large numbers of insect visitors and most fruit set on the tops of trees, beyond the reach of ungulate browsers such as giraffes (which consume a substantial proportion of A. nigrescens flowers). Wasps, flies and solitary bees were the most numerous visitors and are likely to play a significant role in pollination

Are giraffes pollinators or flower predators of Acacia nigrescens in Kruger National Park, South Africa?

We examined the relationship between giraffes (Giraffa camelopardalis) and Acacia nigrescens in Kruger National Park, South Africa, to determine whether these tall ungulates may be providing a pollination service for the trees, or are simply flower predators. We quantified florivory and subsequent fruit set in the presence and absence of giraffes. Acacia nigrescens flowers are clearly a substantial dietary component for giraffes. Although A. nigrescens flowers contain almost three times as much condensed tannin as leaves, giraffes consume large quantities of flowers (∼85% of flowers within reach), resulting in distinct browse lines on the trees. This substantial florivory is detrimental to the overall fecundity of A. nigrescens, with significantly reduced fruit set at heights on trees that are accessible to giraffes. Fruit set increased above the reach of giraffes, suggesting successful pollination by insects. Giraffes were effectively flower predators of A. nigrescens in the season we examined