Shopping cartNetherlands Journal of Zoology
Volumes & issues:
-
SEASONAL DEVELOPMENT AND DORMANCY OF INSECTS AND MITES FEEDING ON OLIVE: A REVIEW
- + Show Description - Hide Description
-
This review of literature includes an introduction on the origin of the olive tree and lists of 116 species of insects and 30 of mites known to infest it, then the geographic distribution, host plants, feeding habits, voltinism and seasonal history of each of 34 species of phytophagous insects and seven of mites, for which there is sufficient information to justify such treatment. Most of them are monophagous or oligophagous and closely associated with the olive tree, while the remainder have many to a few host plants in addition to olive, but have populations adapted to olive. Of the species covered, 16 are Homoptera, one Hemiptera, one Thysanoptera, five Coleoptera, four Diptera, seven Lepidoptera, six Eriophyoidea and one Tetranychoidea. The review shows that all species, except one, have a seasonal dormancy and for most of them diapause is certain or reasonably suspected to occur. Seasonal displacement does occur in a number of species, especially shortly before or after dormancy. Differences between authors in seasonal history are pointed out and conclusions drawn based on the most convincing papers. Further research on important yet neglected aspects of the life history of olive arthropods is suggested.
-
A COUPLED OSCILLATOR MODEL DESCRIBES NORMAL AND STRANGE ZOOPLANKTON SWIMMING BEHAVIOUR
- + Show Description - Hide Description
-
"Normal" swimming in marine and freshwater zooplankton is often intermittent with active upward and more passive downward displacements. In the freshwater cladoceran Daphnia, the pattern is sometimes regular enough to demonstrate the presence of a rhythm. Abnormal swimming patterns were also described. For example, large amplitude oscillations occur or animals may stay for a long time at the lighted side of a tube and then move suddenly away from light. A model, consisting of a coupled oscillator, was developed, that describes these "normal" and abnormal swimming patterns. This could be achieved by varying the strength of the coupling only.
-
THE TEMPORAL AND SPATIAL RELATIONSHIP BETWEEN STENOTOPIC DWARF SPIDERS (ERIGONINAE: ARANEAE) AND THEIR PREY (ISOTOMIDAE: COLLEMBOLA) IN COASTAL GREY DUNES: A NUMERICAL AGGREGATIVE RESPONSE OR COMMON MICROHABITAT PREFERENCE?
- + Show Description - Hide Description
-
During 1999-2001, we investigated the spatial and temporal relationship between stenotopic dwarf spiders and their springtail prey in coastal grey dunes. This habitat is characterised by severe microclimatological fluctuations that influence the spatial and temporal distribution of epigeic invertebrates. In three types of grey dune vegetation, where springtails showed different temporal abundance patterns, a positive relationship was observed between the phenology of the palatable springtails and stenotopic dwarf spiders. In particular, the relationship with female spiders, which depend highly on prey for reproduction, was very significant. A similar spatial aggregation exists for both prey and predator. Their presence was influenced by the same soil and vegetation characteristics. Two mechanisms are assumed to be responsible for this similar distribution; a common, independently developed habitat preference or a numerical response from the spiders in the presence of prey. After correction for intra-correlations, the relationship between prey and predator was nonsignificant and hence more likely to be the result of common microhabitat preferences.
-
SURVIVAL DIFFERENCES OF THE TWO MALE MORPHS IN THE DWARF SPIDER OEDOTHORAX GIBBOSUS BLACKWALL, 1841 (ERIGONINAE, LINYPHIIDAE, ARANEAE)
- + Show Description - Hide Description
-
Oedothorax gibbosus is a rare dwarf spider species in Flanders bound to oligo- and mesotrophic alder carrs. This dwarf spider is characterised by the appearance of a male dimorphism; there is a gibbosus male morph with a hunch on the last third of the carapace, anterior to which is a hairy groove, and a tuberosus morph without these features. Earlier studies have already indicated some differences between both male morphs. According to VANACKER et al. (2001) the juvenile phase (the period between the emergence of the spiders and the last moult) of the gibbosus morph is significantly longer than the juvenile phase of the tuberosus morph, and this is presumably necessary for the production of the hunch and the hairy groove. This hairy groove probably secretes a fluid that is important for the gustatoric courtship behaviour and gibbosus would therefore have a reproductive advantage (HEINEMANN & UHL, 2000). In this paper we report another interesting difference between both morphs. To examine if the male morphs also differ in survival, some survival experiments, in normal food and moisture conditions and in two extreme conditions, namely in foodless and low moisture environments, were set up. The gibbosus male is significantly more susceptible to foodless conditions than the tuberosus male, and also in normal conditions tuberosus lives significantly longer than gibbosus. This is demonstrated by means of survival curves. In low moisture conditions, however, we could not prove that survival rate differs between both male morphs. The higher survival rate of tuberosus is a possible explanation for the morph ratio in favour of tuberosus in the studied field population.
-
NO NOCTURNAL ENERGETIC SAVINGS IN RESPONSE TO HARD WORK IN FREE-LIVING GREAT TITS
- + Show Description - Hide Description
-
We measured energy expenditure in free-living great tits (Parus major) during the active (day) and the inactive period (night) with the aim of determining whether great tits compensate for energy costs made during periods of high activity in periods of low activity. If such compensation occurs, inferences from measurements of energy expenditure over a 24 h period, with regard to the energy costs of the different behavioural elements, may obscure relations between parental effort and energy expenditure. Also, energy budgets, based on estimates of time budgets combined with a fixed cost for each behavioural category observed, may be unreliable if animals are able to compensate for energy costs made during periods of high activity in periods of low activity. Laboratory studies have revealed a reduction in resting metabolic rate (RMR) when birds are forced to work harder during the day, but it has not yet been investigated whether such nocturnal savings are also made under natural conditions. We manipulated brood size in a free-living population of great tits to create a difference in the demands of the nest, measured effort (feeding visits) and daily energy expenditure (DEE). In order to test whether compensation occurred we measured both DEE over 24 h, and resting metabolic rates (RMR) of female great tits at night. DEE and feeding rate differed between the experimental groups, being higher in females rearing enlarged broods, but we did not find evidence of nocturnal saving.
-
REPRODUCTIVE STRATEGIES OF TWO SYMPATRIC 'SMALL BARBS' (BARBUS HUMILIS AND B. TANAPELAGIUS, CYPRINIDAE) IN LAKE TANA, ETHIOPIA
- + Show Description - Hide Description
-
The reproductive strategies of two species of 'small barbs' (<100 mm forklength, LF) from Lake Tana (Ethiopia), the benthic-littoral Barbus humilis and the pelagic B. tanapelagius, were investigated. Monthly samples were collected from five different habitats over a 1 year period (>12,000 fish). Both species have a long breeding period (from March to September), and the distinct bimodal size-frequency distributions of eggs suggest multiple spawning for both species. Absolute fecundity increased exponentially with fish size, and was significantly higher for B. humilis than for B. tanapelagius. Egg size was similar. Relative fecundity was significantly higher in B. humilis. In most habitats B. tanapelagius reached first maturity at a smaller size (58.5 mm) than B. humilis (64.5 mm). However, in shallow habitats with clear water B. humilis females are much smaller at first maturity (48.3 mm), possibly due to high tapeworm infection rates. The range of fecundity in small barbs from Lake Tana (172-339 eggs per gram) was low compared with small lacustrine cyprinids and clupeids from other African lakes. The reproductive strategies of the two barbs were discussed in relation to their feeding potential, food availability, parasite infection rate and risk of predation.
back to top