Group size and stability: Why do gibbons and spider monkeys differ?

Gibbons and spider monkeys have similar diets, body size, and locomotor patterns. They are therefore expected to be subject to similar socioecological rules. However their grouping patterns differ. Gibbons live in small stable groups, whereas spider monkey form unstable sub-groups that vary from small to large during different seasons. If similar principles apply to the two species, food abundance should vary more for spider monkeys than for gibbons; food density should be similar for the two species when spider monkey sub-groups are the same size as gibbon groups; and the highest level of food abundance should be higher for spider monkeys than for gibbons. These predictions are upheld for a comparison of particular populations ofHylobates muelleri andAteles geoffroyi.     

Resource sharing among ramets in the clonal herb,Fragaria chiloensis

Summary The herbaceous perennial, Fragaria chiloensis, reproduces vegetatively on coastal sand dunes in California by growth of stolons that bear rosettes. Movement of water and photosynthates through stolons integrates water and carbon metabolism of rosettes both before and after they root. New, unrooted rosettes import sufficient water and nitrogen to maintain levels near those of established rosettes; yet support of an unrooted rosette did not decrease growth of a connected, rooted sibling given abundant light, water, and soil nutrients. Under such conditions strings of unrooted rosettes with the associated stolon appeared self-sufficient for carbon; shade and drought induced import of photosynthates. New rosettes produced and maintained a limited root mass upon contact with dry sand, which could increase probability of establishment. Rooting did not induce senescence of stolons. Connection between two established rosettes prevented death by drought and shade, even when neither rosette could have survived singly. Results suggest that physiological integration of connected rosettes may increase total growth of clones of F. chiloensis through sharing of resources among ramets, especially when resource availability is changeable or patchy.     

Defense reactions of mosquitoes to filarial worms: potential mechanism for avoidance of the response by Brugia pahangi microfilariae

The melanization response of Aedes trivittatus and the black-eyed Liverpool (LVP) and Rocke-feller (RKF) strains of Aedes aegypti against intrathoracically inoculated Brugia pahangi microfilariae (mff) that previously had penetrated LVP, RKF, or A. trivittatus midguts in vitro was assessed at 1, 3, and 5 days postinoculation (PI). LVP and RKF midgut-derived mff almost totally avoided the melanization response and developed normally in LVP strain A. aegypti, and although over 90% of these mff died by 5 days PI in RKF mosquitoes, the majority of these were not melanized. A. aegypti midgut-derived mff also were able to avoid the response of A. trivittatus in 33–43% of the cases. Penetration through A. trivittatus midguts, however, did not significantly affect the ability of mff to avoid the melanization response in any of the mosquitoes examined. Allogeneic and xenogeneic tissue inplants were accepted by all three mosquito species examined. Data presented support the hypothesis that mff avoid immune recognition in compatible mosquitoes by coating themselves with midgut material(s) during penetration of the midgut in their migration to the hemocoel.     

Some aspects of the natural history and food selection ofAvahi laniger

Two groups ofAvahi laniger were studied in the Forêt de Analamozoatra near Perinet in the eastern rainforest of Madagascar from August to October 1984. Overlap between the home ranges of neighbouring groups ofA. laniger was minimal. Group size ranged from one to four individuals with a median group size of two. In four out of ten groups a baby was born between August and September.A. laniger were most active after dusk and before dawn. They had an extended resting period around midnight. Their diet consisted mostly of leaves from at least 17 different plant species. They also ate flowers. Fruit eating was recorded twice. Leaves eaten had high contents of protein and sugar but did not contain alkaloids. The concentration of condensed tannins did not differ between food items and non-food items. There was no indication of competition with other prosimians that might explain their nocturnality.     

Experimental dissociation of food intake and plasma beta-endorphin following 2-deoxy-D-glucose in rats

The present studies were undertaken to further assess the role of plasma beta-endorphin (beta-EP) in the hyperphagia induced by the glucose antimetabolite, 2-deoxy-D-glucose (2-DG). Plasma concentrations of immunoreactive beta-EP (ir-beta-EP) were measured at the end of the first hour of feeding in all animals treated with 400 mg/kg 2-DG. Previous studies had shown a consistent, positive association between 2-DG hyperphagia and plasma ir-beta-EP concentrations, but the present data revealed dissociations between hyperphagia and plasma ir-beta-EP. Dexamethasone administration blocked the 2-DG-induced rise in plasma ir-beta-EP, but had no effect on the 2-DG hyperphagia measured at 1 hour. Forced drinking of a 2% NaCl solution decreased 2-DG hyperphagia, but not the 2-DG induced rise in plasma ir-beta-EP. Thus, elevations in plasma ir-beta-EP are not necessary for the full expression of 2-DG-induced hyperphagia in dexamethasone-treated rats. Furthermore, decreased feeding responses to 2-DG could coexist with increased levels of plasma ir-beta-EP in NaCl-treated normal rats. Elevations in plasma ir-beta-EP do not appear to be the critical opiate link in 2-DG induced hyperphagia.     

Distribution,biology and hybridization of Scaphirhynchus albus and S. platorynchus in the Missouri and Mississippi rivers

Synopsis Scaphirhynchus albus and S. platorynchus were studied in Missouri during 1978–1979 to assess their distribution and abundance, to obtain information on their life histories, and to identify existing or potential threats to their survival. S. platorynchus was collected in substantial numbers (4355 specimens) at all 12 sampling stations in the Missouri and Mississippi rivers, while only 11 S. albus were captured from 6 stations. Twelve specimens identified in the field as hybrids between the two species were captured from 4 stations. Morphometric and meristic comparisons of presumed hybrids with the parent species, using cluster and principal components analyses, demonstrated intermediacy of most specimens identified in the field as hybrids. Aquatic insects comprised most of the diet of S. platorynchus and S. albus, but S. albus and the hybrids had consumed considerable quantities of fish. S. albus grew more rapidly than S. platorynchus, while the growth of hybrids was intermediate. Hybridization appears to be a recent phenomenon, resulting from man-caused changes in the big-river environment. Hybridization may be a threat to survival of S. albus in the study streams.     

Glucagon-related peptides in the rat hypothalamus

Summary Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism.     

Growth and production of O+ bream (Abramis brama), O+ roach (Rutilus rutilus) and O+ carp (Cyprinus carpio) in 10 drainable 0.1 Ha ponds

In ten 0.1 ha drainable ponds O⁺ cyprinids were stocked to assess their impact on the aquatic community. Bream and roach were stocked in early June, 1986, and carp in early July, 1986. The ponds were drained mid November, 1986. The relationship between the fish community and its food resource was estimated in terms of production and consumption with use of the data on growth and mortality of the fish. The average gross production of the fish species in the ten ponds (48.4 kg during the experiment) was dominated by the carp (58.5%). A minimum estimate of the food consumption of the O⁺ cyprinids is 760 kJ.m^–2. The average production of bream and roach was much lower than that of carp due to a higher mortality and a more specialized feeding pattern. The gross productions of carp, bream and roach in the ten ponds were not significantly related, although stomach analysis showed diet overlap between the carp and the bream.     

Food habits and prey selection of three species of groupers from the genus Cephalopholis (Serranidae: Teleostei)

Synopsis This paper describes a study performed in the Gulf of Aqaba on food selectivity and hunting behaviour of three species of sympatric fish from the genusCephalopholis. These fishes occur in the shallow-water coral habitats of the Red Sea and feed on fishes and invertebrates. Of these,C. argus andC. miniata prefer selected fish species (95 and 86% of their diet respectively), whereasC. hemistiktos consumes more invertebrates (36%) and is less selective with respect to fish species. All three species employ various techniques to catch their prey and in situations where their elected food is absent they readily switch to substitute prey species.     

Feeding habits of Japanese butterfyfishes (Chaetodontidae)

Synopsis Stomach content data from 32 species of Japanese butterflyfishes of the family Chaetodontidae were used to classify them into feeding groups and to determine their important food resources. Four major feeding groups were distinguished: (1) obligative coral feeders which prey exclusively or mostly on Scleractinian corals, (2) facultative coral feeders that take both corals and other benthic organisms, (3) noncoralline invertebrate feeders which consume benthic invertebrates other than corals, and (4) zooplankton feeders. Ten species representing 31% of the butterflyfishes belong to the first category. The second and third categories include 13 (41%) and 8 (25%) species, respectively. The fourth category is represented by only one species which picks individual zooplankters, especially calanoid copepods, in midwater above the reefs. Facultative coral feeders consumed varying quantities of scleractinians (from 2 to 74% of food volume), along with a variety of benthic organisms including algae, alcyonarians, sea anemones, sedentary polychaetes, sponges, hydroids, etc. Noncoralline invertebrate feeders, on the other hand, tend to have low diversified diets, predominated by one prey item such as sea anemones, zoanthideans, polychaetes, or colonial ascidians. These dietary data suggest that scleractinian corals are the most important food resource for the Japanese butterflyfishes, and next important are sea anemones, sedentary polychaetes, alcyonarians, and algae.