Anita Giglio

Ultrastructure and Comparative Morphology of Mouth-part Sensilla in Ground Beetle Larvae (Insecta, Coleoptera, Carabidae)

Abstract Labial and maxillary palps in 22 species of ground beetle larvae revealed the presence of four different types of sensilla: sensilla digitiformia, sensilla campaniformia, sensilla basiconica and sensilla chaetica. Using transmission electron microscopy techniques, the role of most of them was defined: sensilla campaniformia and sensilla chaetica are mechanoreceptors; while sensilla basiconica are chemoreceptors. Sensilla digitiformia can be both mechanoreceptors and chemoreceptors, though hygroreception may also be postulated on the basis of their abundance on the mouthparts of some hygrophilous species that depend on damp or wet patchy biotopes/seasons. The number and location of the sensory structures has been found to vary among the investigated taxa. The differences are related to the larval behavioural types, and are an adaptive response to different lifestyles, feeding habits and use of space.

Effects of the pesticide dimethoate on a non-target generalist carabid, Pterostichus melas italicus (Dejean, 1828) (Coleoptera: Carabidae)

Abstract This study draws attention to the toxicity of dimethoate at sub-lethal concentration to beneficial carabid beetles living in olive groves agroecosystem of Calabria, Italy. Short- and long-term effects of dimethoate on a non-target generalist predator in agroecosystems, Pterostichus melas italicus (Dejean, 1828) (Coleoptera, Carabidae) adults, were quantified by toxicity test, total haemocyte counts and morphometric analyses. In laboratory toxicity tests, beetles of both sexes exposed to field concentration of this toxicant showed a reduction of activity and a mortality of 10% after 72 h. Moreover, the impact of dimethoate on the total haemocyte counts (THCs) was recorded as a significantly lower number of circulating haemocytes in treated animals compared to controls at 48 h. Morphometric analyses showed that dimethoate caused long-term sub-lethal effects as a reduction of some morphometric parameters in P. melas italicus populations from two olive groves (treated and natural). In addition, a significant reduction in body size of females from long-term treated olive grove and a sexual dimorphism alteration were observed. As a result, data suggested that dimethoate may cause sub-lethal effects on this non-target carabid species.

The defensive secretion of Carabus lefebvrei Dejean 1826 pupa (Coleoptera, Carabidae): gland ultrastructure and chemical identification

This study documents the defensive function of flavored humor secreted by the abdominal glands of Carabus lefebvrei pupae. The morphology and the ultrastructure of these glands were described and the volatile compounds of glands secretion were identified by gas chromatography/mass spectrometry. The ultrastructure analysis shows an acinose complex formed by about 50 clusters. Each cluster has 20 glandular units and the unit—composed of one secretory and one canal cell lying along a duct—belongs to the class 3 cell type of Quennedey (1998). In the cytoplasm, the secretory cell contains abundant rough endoplasmatic reticula, glycogen granules, numerous mitochondria, and many well‐developed Golgi complexes producing electron‐dense secretory granules. Mitochondria are large, elongated, and often adjoining electronlucent vesicles. The kind and the origin of secretory granules varying in size and density were discussed. The chemical analysis of the gland secretion revealed the presence of a mixture of low molecular weight terpenes, ketones, aldehydes, alcohols, esters, and carboxylic acids. Monoterpenes, especially linalool, were the major products. We supposed that ketones, aldehydes, alcohols, esters, and carboxylic acids have a deterrent function against the predators and monoterpenes provide a prophylaxis function against pathogens. Microsc. Res. Tech., 2009.

Current knowledge on exocrine glands in carabid beetles: structure, function and chemical compounds.

Abstract Many exocrine products used by ground beetles are pheromones and allomones that regulate intra- and interspecific interactions and contribute to their success in terrestrial ecosystems. This mini-review attempts to unify major themes related to the exocrine glands of carabid beetles. Here we report on both glandular structures and the role of secretions in carabid adults, and that little information is available on the ecological significance of glandular secretions in pre-imaginal stages.

The larva of Siagona europaea Dejean, 1826: Morphology and collecting technique for a subterranean blind ‘running ant killer’ (Coleoptera, Carabidae)

The larva of Siagona europaea Dejean, 1826 collected in the field with a new type of trap, the bait trap, is described. As an adult, this is a myrmecophagous beetle; however, until 2003, in ten years of research no larvae had been found in the field when excavating deep holes around Messor nests in clay soils, in which to place the usually employed pit fall traps. Therefore, a new type of trap was adopted, i.e. a subterranean trap positioned where the main soil crevices intersect. One larva of second instar and one of third one were studied. Most larval features are atypical of carabid beetle larvae and, in particular, the form and structure of the head appendages and the form and insertion of the urogomphi are of interest. Moreover, the larva of S. europaea is completely blind, no trace of stemmata being present in either instar. Its morphology, as well as the recording of its behaviour in the lab, point to it being a ‘runner’, exploring the subterranean crack system of clay vertisols.

Hunting Ants in Mediterranean clay soils: life history of Siagona europaea (Coleoptera, Carabidae)

Abstract In southern Italy, Siagona europaea is common on clay soils and occurs up to the 38th parallel. Activity recordings have revealed that the beetles are strictly nocturnal. They are resistant to desiccation and prefer temperatures above 30 °C. Their flat body indicates adaptation to life in clay soils, which, in southern Italy, are deeply fissured from April to September. The behaviour of the beetles was observed in a transparent system of cavities consisting of plastic boxes connected by tubes. The beetles feed exclusively on ants that are caught by surprise attack outside their nests. Ants perceive the beetles as being hostile via chemical cues. Single ants then normally retreat, whereas groups of ants attack immediately. The beetles behave unaggressively against cospecifics and rest in groups of various numbers in flat soil crevices. Copulation takes place from the end of April onwards, whereas egg laying occurs from the end of May onwards. The females produce only a few eggs, which are unusually large, and shift them singly in narrow soil cracks. The larvae develop during the summer deep in the soil; they are blind and can be characterized as cave‐life forms by their extremely long cerci and antennae that have a whip‐like unsclerotized sticky distal part.

Morphometry of eyes, antennae and wings in three species of Siagona(Coleoptera, Carabidae)

Abstract In carabid beetles, physiological and behavioural characteristics reflect specific habitat demands and there is a strong correlation between body form and habit in species with different life style. In this study, we compared the morphometry and compound eye characteristics of three species of the genus Siagona: Siagona jenissoni, Siagona dejeani and Siagona europaea. These carabids have a stenotopic lifestyle in Mediterranean clayey soils, inhabiting the ground fissure system formed during the dry season. All species have a Mediterranean distribution and are nocturnal olfactory hunters, and are strict ant predators. For morphometric measurements, we considered body length (mm), wing length (mm), antenna length (mm), head width (mm), trochanter length (mm), number of ommatidia, eye surface area (mm2), ommatidia density (number of ommatidia/mm2 of eye surface area), head height (mm), thorax height (mm) and abdomen height (mm). The data revealed intersexual and interspecific differences. The three species differ in relative length of the antennae, density and number of ommatidia and relative trochanter length. Significant differences occurred in wing sizes, which are well developed in Siagona europaea, the only species capable of flight. When eye size is compared with other ground beetles of various lifestyles, Siagona shows pronounced “microphthalmy” an adaptation to subterranean life in clayey crevices of tropical and subtropical climates with a marked dry season.

Phenoloxidase activity among developmental stages and pupal cell types of the ground beetle Carabus (Chaetocarabus) lefebvrei (Coleoptera, Carabidae)

In ecological immunology is of great importance the study of the immune defense plasticity as response to a variable environment. In holometabolous insects the fitness of each developmental stage depends on the capacity to mount a response (i.e. physiological, behavioral) under environmental pressure. The immune response is a highly dynamic trait closely related to the ecology of organism and the variation in the expression of an immune system component may affect another fitness relevant trait of organism (i.e. growth, reproduction). The present research quantified immune function (total and differential number of hemocytes, phagocytosis in vivo and activity of phenoloxidase) in the pupal stage of Carabus (Chaetocarabus) lefebvrei. Moreover, the cellular and humoral immune function was compared across the larval, pupal and adult stages to evaluate the changes in immunocompetence across the developmental stages. Four types of circulating hemocytes were characterized via transmission electron microscopy in the pupal stage: prohemocytes, plasmatocytes, granulocytes and oenocytoids. The artificial non-self-challenge treatments performed in vivo have shown that plasmatocytes and granulocytes are responsible for phagocytosis. The level of active phenoloxidase increases with the degree of pigmentation of the cuticle in each stage. In C. lefebvrei, there are different strategies in term of immune response to enhance the fitness of each life stage. The results have shown that the variation in speed and specificity of immune function across the developmental stages is correlated with differences in infection risk, life expectancy and biological function of the life cycle.

Apis mellifera ligustica, Spinola 1806 as bioindicator for detecting environmental contamination: a preliminary study of heavy metal pollution in Trieste, Italy

Honeybees have become important tools for the ecotoxicological assessment of soil, water and air metal contamination due to their extraordinary capacity to bioaccumulate toxic metals from the environment. The level of heavy metal pollution in the Trieste city was monitored using foraging bees of Apis mellifera ligustica from hives owned by beekeepers in two sites strategically located in the suburban industrial area and urban ones chosen as control. The metal concentration in foraging bees was determined by inductively coupled plasma-mass spectrometry. The chemical analysis has identified and quantified 11 trace elements accumulated in two different rank orders: Zn> Cu > Sr > Bi > Ni > Cr > Pb = Co > V > Cd > As in foraging bees from the suburban site and Zn > Cu > Sr > Cr > Ni > Bi > Co = V > Pb > As > Cd in bees from urban site. Data revealed concentrations of Cr and Cu significantly higher and concentration of Cd significantly lower in bees from urban sites. The spatial difference and magnitude order in heavy metal accumulation along the urban-suburban gradient are mainly related to the different anthropogenic activity within sampled sites and represent a risk for the human health of people living in the city. We discussed and compared results with the range of values reported in literature.

Avoiding ant detection in Siagona europaea Dejean 1826 (Coleoptera Carabidae): an evolutionary step towards true myrmecophily

Siagona europaea Dejean 1826, a carabid beetle living in clay soils of Mediterranean open lands, has been found to be an exclusive ant predator. Some morphological variations in body form are evidently adaptations to the habitat, favouring in the meantime the myrmecophagous life style. After capturing an ant, the beetle waves the prey held in its mandibles all around its dorsal forebody by arching its head and pronotum; the ants apparently spray a secretion over the beetle while being waved. The cuticular profile of beetles without contact with ants, beetles after capture and consumption of ants and of two ant species, Tapinoma nigerrimum and Messor capitatus, was recorded. Gas chromatography analyses revealed that more component are present on the carabid cuticle after predation and that they correspond to those of the tested ants. We suggest that this may be an intermediate evolutionary stage towards a true myrmecophilous life style as present in other tropical carabids. Moreover behavioural tests proved the diet (ants) which the beetle was fed triggers different reactions in ants of the same, or of a different, species.