Host choice in the phoretic mite Parasitellus fucorum (Mesostigmata: Parasitidae): which bumblebee caste is the best?

Host caste recognition may be important for the dispersal of phoretic mites associated with social insects. All developmental stages of the mite Parasitellus fucorum (Acari: Mesostigmata: Parasitidae) live in the nests of bumblebees (Hymenoptera: Apidae: Bombus). Dispersal occurs by specialised phoretic instars, deutonymphs, which attach to adult bumblebees. Since bumblebee colonies are annual and only young queens overwinter, deutonymphs that are able to discriminate between bumblebee castes and preferentially attach to queens should be favoured by selection. In the field, deutonymphs of P. fucorum were found to be phoretic on bumblebee workers and queens, and in behavioural experiments all castes proved to be attractive as carriers for the mites. However, they preferred queens that had hibernated as carriers when they could choose between workers and queens. In a further experiment, when given a choice, deutonymphs switched from males to young queens but never transferred from a queen to a male. These results suggest that deutonymphs preferentially attach to queens but may also use other castes for transport. Those dispersing on workers and males may try to switch to queens later. Host-switching is possible during copulation and on flowers, where bees of all castes forage. Received: 14 November 1997 / Accepted: 16 February 1998     

The origin of mentha — gracilis (Lamiaceae). II. essential oils

Essential oils were eamined in nine clones of Mentha arvensis, four clones of M. spicata, and 20 clones of M. gracilis. An F₁ hybrid of M. arvensis M. spicata, selected on the basis of morphology and chromosome number, was matched with one clone of M. Gracilis. Genes for the inheritance of limonene, 1,8-cineole, linalool, isomenthone, carvone, and piperitenone oide were identified in one clone of M. arvensis and two clones of M. spicata. The range of essential oil compounds detected indicates that no one character can be used to identify M. gracilis, but the critical compounds of the oil of M. gracilis can be derived from crosses of M. arvensis M. spicata.     

Maintenance of clonal diversity in Dipsa bifurcata (Fallén, 1810) (Diptera: Lonchopteridae). II. Diapause stabilizes clonal coexistence

We analyze a selection model analogous to a one-locus, two-allele haploid system that can explain recurrent seasonal changes in diversity for communities with diapausing species or populations with diapausing clones. The model demonstrates the potential influence of differential diapause on the stability of species and clonal coexistence and, by extension, on the maintenance of genetic polymorphism in general. Using estimates of clonal fitness values from populations of the parthenogenetic spear-winged fly Dipsa bifurcata (Fallén, 1810) (Diptera: Lonchopteridae), the model explains the long-term stable oscillation of clonal frequencies exhibited by these populations. In general, clones or species that share the same spatial habitat can persist in stable coexistence if there are differences not only in their temporarily fluctuating fitness values but also in their dormancy patterns.     

Studies in Bacidia sensu lato (lichenized Ascomycetes: Lecanorales). II. Six new combinations inFellhanera Vězda

Abstract:In the framework of ongoing studies on tropical representatives of Bacidia sensu lato, six species so far included in that genus are transferred to Fellhanera: Fellhanera africana (Vězda) Lücking comb. nov. (Bas.: Bacidia africana Vězda), Fellhanera albidocincta (Vain.) Lücking comb. nov. (Bas.: Bilimbia albidocincta Vain.), Fellhanera fragilis (Vězda) Lücking & Kalb comb. nov. (Bas.: Bacidia fragilis Vězda), Fellhanera mastothallina (Vain.) Lücking & Sérus. comb.nov. (Bas.: Bacidia mastothallina Vain.), Fellhanera naevia (Vain.) Lücking & Cáceres comb. nov. (Bas.: Bacidia naevia Vain.), and Fellhanera submicrommata (Vězda) Lücking & Kalb comb. nov. (Bas.: Bacidia submicrommata Vězda). Fellhanera angustispora Lücking is reduced into synonymy with F. naevia.     

The biological standard of living in Suriname,c. 1870–1975

The physical stature of Surinamese soldiers is estimated to have increased by more than 3 cm between 1870 and 1909. In the subsequent four decades, the increase in adult male and female height amounted to 0.3–0.5 cm and 0.9–1.0 cm per decade, respectively. This increase in height continued and accelerated during the second half of the twentieth century. Height increase among African and Hindustani Surinamese males and females was similar. Height differences between African and Hindustani Surinamese were therefore fairly constant over time, at 4–5 cm. Other indicators of nutritional and health status, such as infant mortality, showed continuous improvement, whereas per capita calorie and protein availability improved in the twentieth century.     

Distribution,abundance and food of commercial fish in the Black Volta and the Volta Man-made Lake in Ghana during the filling period (1964–1968). II. Characidae.

The characids Alestes and Hydrocynus are common fish of the Black Volta River in Ghana. In Lake Volta, which formed in 1964 after damming the Volta River, Alestes formed a large percentage of commercial fish landings since the beginning of impoundment. However, this genus has been gradually changing its areas of distribution in the lake, and from the third year on it has been occupying mainly the upper end of the new lake. This area with large inflowing rivers has been found to favour Alestes baremose, which has been congregating there in large numbers. The strictly lacustrine environment of the south was poor in Alestes for some time. This was evidently due to overfishing, natural mortality, emigration of the fish from this area, and possibly to small recruitment because of the poorly oxygenated waters during the first two years of impoundment. With time, however, the numbers of Alestes baremose, Alestes dentex senthente, and especially Alestes macrolepidotus have increased in commercial landings in the south. The distribution of Alestes in the lake does not seem to be determined by the abundance and easy availability of food. The rich supply of the ephemeropteran Povilla and other food items has not prevented the withdrawal or rapid decrease in numbers of Alestes in some areas. The abundance of the predatory Hydrocynus in Lake Volta seems to be directly related to the distance from the inflowing rivers. More distant areas have less Hydrocynus than areas close to the rivers. The distribution of Hepsetus odoe seems to be just the opposite.     

Comparative studies of the carotenoids in some fauna of the gullmar fiord (Bohuslän,Sweden). IV-Ascidiella aspersa (O. F. Müller), (Tunicata).

The author investigated the presence of various carotenoids in Ascidiella aspersa (O. F. Müller), (Tunicata) by means of columnar and thin-layer chromatography.The investigations revealed the presence of the following carotenoids: cynthiaxanthin (2.9%), capsanthin (32.6%), capsorubin (4.8%), capsorubin-like (15.2%), astaxanthin (4.7%) and astacene (39.8%).     

Binuclear metal complexes. 59. Synthesis and magnetism of dicopper(II) and copper(II)-nickel(II) complexes with N,N′-ethylenedisalicylamidatocuprate(II)

The complexes [Cu(samen)Cu(L)] and [Cu(samen)Ni(L)₂] (Lbpy, phen) have been synthesized by the reaction of sodium N,N′-ethylenedisalicylamidatocuprate(II) pentahydrate (Na₂- [Cu(samen)]·5H₂O), a divalent metal ion, and 2,2′- dipyridyl or 1,10-phenanthroline. Cryomagnetic data for the CuCu complexes did not fit the Bleaney- Bowers equation; but the data did fit a modified Bleaney-Bowers equation

with a large negative J and a significant negative θ, suggesting that a considerable magnetic interaction operates between essentially planar [Cu(samen)Cu(L)] molecules. The magnetisms of the CuNi complexes were well interpreted in terms of the susceptibility equation based on the Heisenberg model. An antiferromagnetic spin-exchange interaction (J= −13∼−14 cm⁻¹) was suggested between the metal ions.     

The general biology of Verruca stroemia (O.F. Müller). II. Reproductive cycle,population structure,and factors affecting release of nauplii

The reproductive cycle of Verruca stroemia (O. F. Müller) has been investigated. From an examination of the percentage of animals with egg masses it is shown that there is a major brood, virtually synchronous throughout the whole population, and which is released at about the time of the spring diatom increase: subsequently, smaller broods are produced during the summer, ≈ 20 % of the population carrying egg masses at any one time. The relation of these broods to the size — frequency composition of the oocytes throughout the year has been examined.Sexual maturity is reached at a size of ≈ 2.0 mm basal diameter.Animals maintained on a raft and kept free from other organisms have a greater breeding potential; this is ascribed to the better nutrient conditions.No egg masses are present during the autumn. It is suggested that the poor nutrient conditions allow all the animals in the population to bring the female gonads to the same state by late winter and so give marked synchrony of the spring brood.Most size-classes are present throughout the year.Release of nauplii is stimulated by extracts of V. stroemia itself, Balanus balanoides, B. balanus, and Chthamalus stellatus.     

An ultrastructural investigation of Hrabeiella Pizl & Chalupský, 1984 (Annelida). II. The spermatozoon

The mature spermatozoa of the terrestrial non-clitellate annelid Hrabeiella periglandulata Pizl & Chalupsky, 1984 s.l. were examined using light and electron microscopy. They are about 150 mum long, filiform and extremely slender (maximum diameter, 450-475 nm). The acrosome is very elongate (about 25 mum), tapering and conical. Its transverse section is circular apically but shows an evident six-rayed symmetry in its basal region. The nucleus appears convex at both ends; apically, it extends laterally into the acrosome, and basally, it plugs into the centriolar region. The nucleus is about 23 mum long and has a rounded, tri- to pentalobed, slightly helical profile. The midpiece contains one elongate, free (paraxonemal) mitochondrion, 27 accessory tubules, which are slightly larger and more opaque than the axonemal microtubules; and seven electron-dense, non-membrane-bounded rods distributed around the axoneme. The flagellum tapers rapidly posteriorly. None of the observed similarities to the sperm (introsperm) of questids, protodrilids or other polychaetes seems to represent an immediate synapomorphy. None of the spermatozoal autapomorphies of the Euclitellata is shared by Hrabeiella.     

Vitellogenesis in Acanthoscelides obtectus (Coleoptera: Bruchidae). II—The conditions of vitellogenesis in a strain from Colombia. Comparative study and adaptive significance

The reproductive activity of an Acanthoscelides obtectus strain originating in the high Colombian plateau (altiplanos) was compared to that of a European strain. Colombian females exhibited greater individual variations than their European counterparts. Some females did not synthesize vitellogenin during the 140-day period of observation, while others performed synthesis but not incorporation into oocytes. Under these conditions, 40–50% of the females could form a limited number of oocytes. The presence of Phaseolus vulgaris seeds stimulated vitellogenin synthesis and incorporation by most females. This initiation of ovarian activity enabled mating to occur, which in turn led to maximal stimulation of oogenesis. This host plant—mating interaction leads to the production and release of a large number of eggs. The observed variability of reproductive activity and its dependence on stimulatory factors probably reflect an adaptation to the ecological conditions prevailing in the high-altitude environment of these insects.