The Casparian Strip of Clivia miniata Reg. Roots: Isolation,Fine Structure and Chemical Nature*

The root endodermis of Clivia miniata Reg. was successfully isolated using the cell wall degrading enzymes cellulase and pectinase. The enzymes did not depolymerize those regions of the primary cell walls of anticlinal endodermal root cells where the Casparian strips were located. Since the endodermis of C. miniata roots remained in its primary developmental state over the whole root length, endodermal isolates essentially represented Casparian strips. Thus, sufficient amounts of isolated Casparian strips could be obtained to allow further detailed investigations of the isolates by microscopic, histochemical and analytical methods. Scanning electron microscopy revealed the reticular structure of the Casparian strips completely surrounding the central cylinder of the roots. Whereas in younger parts of the root only the anticlinal cell walls of the endodermis remained intact in the isolates, in older parts of the root the periclinal walls also restricted enzymatic degradation due to the deposition of lignin. Extracts of the isolates with organic solvents did not reveal any wax-like substances which might have been deposited within the cell wall forming a transport barrier, as is the case with cutin and suberin. However, several histochemical and analytical methods (elemental analysis and FTIR spectroscopy) showed that the chemical nature of the Casparian strips of C. miniata roots can definitely be a lignified cell wall. These findings are in complete agreement with studies carried out at the beginning of this century on the chemical nature of the Casparian strips of several other plant species. The implications of these results concerning apoplasmatic transport of solutes and water across Casparian strips are discussed.     

Metapopulation dynamics in a regional population of the blue-winged grasshopper (Oedipoda caerulescens; Linnaeus, 1758)

For two consecutive years we registered the presence (or absence) of blue winged grasshoppers (Oedipoda caerulescens; Linnaeus, 1758) on 312 habitat patches of differing size in a region of more than 3000 ha. The data show that presence of grasshoppers on a habitat patch is dependent on patch size as well as on patch isolation. We used an ecological incidence model to describe the metapopulation dynamics of the regional population and derived the parameters for this model from presence-absence data and observations of Oedipoda dispersion. The analysis shows that local extinction of grasshopper populations is influenced by strong fluctuations of environmental conditions and that for a number of small patches in our region recolonization is important for the presence of O. caerulescens. Colonization probability, as derived using the incidence model, is in good agreement with estimates from a population genetical analysis.     

Habitat Use and Mobility of Two Threatened Coastal Dune Insects: Implications for Conservation

We studied the habitat use and mobility of the Grayling butterfly (Hipparchia semele) and the Blue-Winged Grasshopper (Oedipoda caerulescens), two threatened insects within spatially structured blond and grey dunes in a nature reserve along the Belgian coast. Although both species occur in the same biotope, H. semele were more abundant in open, dynamic sites with a relatively high amount of bare sand, while O. caerulescens preferred sheltered, more stable environments with a lower amount of bare sand. Unlike H. semele, substrate use varied in accordance to body colouration in O. caerulescens, especially on cold days, with light-coloured animals being more abundant on sand and dark-coloured animals more abundant on moss. During a mark-recapture-study, we marked 493 Grayling butterflies and 1289 Blue-Winged Grasshoppers. On average, both sexes of H. semele were equally mobile (about 150 m/day; maximum recorded distance of about 1700 m) while male O. caerulescens were significantly more mobile than females (daily average 47 vs. 5 m; maximum distances observed for O. caerulescens were about 800 m). The importance of habitat heterogeneity (within and among patches) and the consequences of habitat use and mobility of both species for the conservation of typical coastal dune habitats are discussed. The complementary use of species-specific information to site-based management measures is advocated.     

Breeding systems in Clivia (Amaryllidaceae): late‐acting self‐incompatibility and its functional consequences

Late‐acting (ovarian) self‐incompatibility, characterized by minimal or zero seed production following self‐pollen tube growth to the ovules, is expected to show phylogenetic clustering, but can otherwise be difficult to distinguish from early‐acting inbreeding depression. In Amaryllidaceae, late‐acting self‐incompatibility has been proposed for Narcissus (Narcisseae) and Cyrtanthus (Cyrtantheae). Here, we investigate whether it occurs in the horticulturally important genus Clivia (Haemantheae) and test whether species in this genus experience ovule discounting in wild populations. Seed‐set results following controlled hand pollinations revealed that Clivia miniata and C. gardenii are largely self‐sterile. Self‐ and cross‐pollinated flowers of both species had similar proportions of pollen tubes entering the ovary, and those of C. gardenii also did not differ in the proportions of pollen tubes that penetrated ovules, thus ruling out classical gametophytic self‐incompatibility acting in the style, but not early inbreeding depression. Flowers that received equal mixtures of self‐ and cross‐pollen set fewer seeds than those that received cross‐pollen only, but it was unclear whether this effect was a result of ovule discounting or interactions on the stigma. The prevention of self‐pollination by the emasculation of either single flowers or whole inflorescences in wild populations did not affect seed set, suggesting that ovule discounting is not a major natural limitation on seed production. Flowers typically produce one to three large fleshy seeds from approximately 16 available ovules, even when supplementally hand pollinated, suggesting that fecundity is mostly resource limited. The results of this study suggest that Clivia spp. are largely self‐sterile as a result of either a late‐acting self‐incompatibility system or severe early inbreeding depression, but ovule discounting caused by self‐pollination is not a major constraint on fecundity. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 155–168.     

Water balance and rectal absorption in the grasshopper Oedipoda

ABSTRACT. The xeric grasshopper Oedipoda germanica pyrenaica (Uvarov, 1936) has a daily cycle of water-gain from feeding during the afternoon and water-loss at night. The afternoon peak of water-gain in laboratory animals is correlated with a short-term rise in the osmotic pressure of the haemolymph in field animals. It is estimated that starved large animals would deplete their water reserves within 8–11 days. Water loss in faeces production is a major component of total water loss only during the late afternoon to early evening; at all other times transpiratory water losses are considerably greater. Overall, 23% of the daily water loss occurs through the faeces. From hindgut cannulation experiments, c. 80% of water entering the rectum is reabsorbed. A comparison of transpiratory water losses of xeric and mesic Orthoptera and some xeric Coleoptera revealed that water losses are some 6–7 times higher in Orthoptera than in similar sized Coleoptera.     

Active military training areas as refugia for disturbance-dependent endangered insects

Oedipoda caerulescens (blue-winged grasshopper) and Cicindela hybrida (northern dune tiger beetle) are protected insects in Germany and elsewhere. They are known to occur on sparsely vegetated, sandy soil. Populations of the two insects were evaluated in relation to physical soil disturbance on four military training areas in Germany to determine if the military disturbance regime occurring there is conducive to the survival of the species and to provide insight into the nature of the disturbance that may be necessary as conservationists seek ways to maintain, establish or re-establish suitable habitat. Adults of O. caerulescens exhibited statistically significant preference for areas with between 60% and 100% surface disturbance, corresponding to 50–70% plant cover, depending on the location. C. hybrida adults preferentially occupied areas with >40% disturbance resulting in an average of 61% plant cover. The results confirm suggestions that both species are disturbance-dependent. Military training areas represent some of the last, large remnants of sparse, dry, sandy grasslands in Europe. The nature of land-based military training creates suitable habitat patches as well as habitat connectivity needed for the maintenance of metapopulations. As a result, military training areas represent some of the last remaining vestiges of a habitat and disturbance regime that are highly favored by O. caerulescens and C. hybrida and other species with similar habitat requirements.     

Age-dependent response of adults of a homochrome grasshopper, Oedipoda miniata, to the dark-colour-inducing neurohormone (DCIN) of locusts

Abstract The effect of the dark-colour-inducing neurohormone (DCIN = [His⁷]-corazonin) of locusts was investigated in field-collected young and old adults of the grasshopper, Oedipoda miniata (Pallas) (Orthoptera: Acrididae). This species shows homochromy, but neither green-brown, nor phase-dependent colour polymorphism. By injecting graded doses of synthetic DCIN in 2 µL of olive oil, young adults were tested within a week of their last moult, and old adults 3.5 months later, a few weeks before natural termination of their reproductive summer diapause. Colour changes were followed for 28 days after injection. Darkening of the young adults was considerable, but their response to DCIN is more moderate than that of conspecific nymphs, by exhibiting a higher threshold, slower response and weaker maximal response. Old adults also show a clear effect, but their response is even slower and less marked than the response of the young adults. It is concluded that the response to DCIN decreases from nymphs to young adults and it is further decreasing with ageing of the adults.     

The effect of translocation on movement behaviour—A test of the assumptions of behavioural studies

Animal movement behaviour is intensively investigated with capture-mark-recapture studies. For the analysis of such experiments, the influence of marking technique, handling and translocation of marked animals on movement pattern is of crucial importance since it may mask or overrule the effects of the main research question. Here we present a capture-mark-recapture experiment on the movement behaviour of the blue-winged grasshopper Oedipoda caerulescens. We analyzed the influence of translocation of individuals from familiar to unfamiliar sites. Our study clearly demonstrates a significant influence of translocation to unfamiliar sites on the movement behaviour of O. caerulescens. Translocated individuals moved longer distances, showed smaller daily turning angles, and thus movements were more directed than those of resident individuals. The effect of translocation on daily moved distances was most pronounced on the first day of the experiment. We thus conclude that at least for the first day after translocation, movement behaviour is significantly influenced by translocation itself. Data ignoring this influence will be unsuitable for the prediction of dispersal behaviour, habitat detection capability or habitat preference.