The breeding biology of equatorial vertebrates: reproduction in the fruit bat, Eidolon helvum, at latitude 0°20'N

The African fruit bat, Eidolon helvum Kerr, is known to occur only south of the Sahara where its distribution is localized. At 0°20' N, this bat exhibits seasonal and synchronized breeding the rhythm of which appears to correspond with the two rainfall peaks typical of Uganda. Quite unexpectedly and unprecedently, this bat exhibits delayed implantation lasting about three months. Evidence for this phenomenon comes from the histological examination of the adult female genital tracts which indicate that mating occurs only in April-June, but implanted embryos are only in evidence in October-November. The male sexual cycle corresponds to such a rhythm and shows a maximum testicular weight at the mating time. Births take place in February-March thus giving a gestation period of about four months. Only one young is born at a time and births occur just before the onset of the higher of the two rainfall peaks, presumably creating favourable conditions for the maximum survival of the young bats when weaned.     

Coral and sea urchin assemblage structure and interrelationships in Kenyan reef lagoons

Patterns of hard coral and sea urchin assemblage structure (species richness, diversity, and abundance) were studied in Kenyan coral reef lagoons which experienced different types of human resource use. Two protected reefs (Malindi and Watamu Marine National Parks) were protected from fishing and coral collection, but exposed to heavy tourist use. One reef (Mombasa MNP) received protection from fishermen for one year and was exploited for fish and corals prior to protection and was defined as a transitional reef. Three reefs (Vipingo, Kanamai, and Diani) were unprotected and experienced heavy fishing and some coral collection. Protected and unprotected reefs were distinct in terms of their assemblage structure with the transitional reef grouping with unprotected reefs based on relative and absolute abundance of coral genera. Protected reefs had slightly higher (p<0.01) coral cover (23.6 ± 8.3 % ± S.D.) than unprotected reefs (16.7 ± 8.5), but the transitional reef had the highest coral cover (30.8 ± 6.4) which increased by 250% since measured in 1987: largely attributable to a large increase inPorites nigrescens cover. Protected reefs had higher coral species richness and diversity and a greater relative abundance ofAcropora, Montipora andGalaxea than unprotected reefs. The transitional reef had high species richness, but lower diversity due to the high dominance ofPorites. Sea urchins showed the opposite pattern with highest diversity in most unprotected reefs. Coral cover, species richness, and diversity were negatively associated with sea urchin abundance, but the relative abundance ofPorites increased with sea urchin abundance to the point wherePorites composed >90% of the coral cover at sites with the highest sea urchin abundance. Effects of coral overcollection was only likely for the genusAcropora (staghorn corals). A combination of direct and indirect effects of human resource use may reduce diversity, species richness, and abundance of corals while increasing the absolute abundance of sea urchins and the relative cover ofPorites.     

Formation of Levan from Raffinose by Levansucrase of Zymomonas mobilis

Levansucrase (EC 2.4.1.10.) of Zymomonas mobilis 113S can perform the polymerisation of fructose moiety from raffinose to levan concomitantly with a release of non‐catabolised melibiose into the medium. The kinetic parameters of the levansucrase‐catalysed reaction provide even higher reaction velocities on raffinose as compared to sucrose, particularly at low substrate concentrations. A decreased value in the number of the average molecular mass (M_n = 1693 kDa), an increased intrinsic viscosity (η = 49.47 cm³/g), and a diminished Huggin's constant (K^' = 0.67) are intrinsic to the levan synthesis from raffinose, indicating certain structural peculiarities compared to a polysaccharide obtained from sucrose (M_n = 1851 kDa, [η] = 42.47 cm³/g, K' = 1.21).