Federica Talarico

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.

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.

Impact of agrochemicals on non-target species: Calathus fuscipes Goeze 1777 (Coleoptera: Carabidae) as model

Carabid beetles are important in the biological control of arable crop pests. Agricultural practices can produce over time a delayed toxic effect at the organismal and population levels and can compromise the survival on these species. In this research, we quantified the cumulative sublethal effect on body size, Malpighian tubules and immune responses in Calathus fuscipes adults living in the potato field and exposed to lambda-cyhalothrin and cymoxanil-based commercial formulates. Reductions of morphological parameters such as body, pronotum and elytron in both males and females from the potato field indicated that the pre-imaginal stages (larvae and pupae) suffer the sublethal effects of exposure to the larvicide control action of lambda-cyhalothrin. Ultrastructural alterations recorded in Malpighian tubules at the level of plasma membrane, mitochondria and nucleus indicated the reduction of the detoxification capability. The basal phenoloxidase and lysozyme-like enzyme activities have measured as markers of immune competence. Spectrophometric analyses showed that the chronic exposure in field causes an increase of basal phenoloxidase enzyme activity, while the lytic activity of haemolymph was not affected. As a result, the use of larvicides and fungicides have a harmful effect on beneficial species such C. fuscipes living in the soil of potato fields. These morphological and physiological results recorded at the organismal level can provide useful information of effects at the population and community levels to preserve the biodiversity of agroecosystem.

Electrophysiological and behavioural analyses on prey searching in the myrmecophagous carabid beetle Siagona europaea Dejean 1826 (Coleoptera Carabidae)

In the present study, electrophysiological and behavioural tests were performed on Siagona europaea Dejean 1826 adults to investigate the importance of chemical cues in ant location. Olfactory responses of labial palp to terpenoids (citral, limonene and geraniol), carboxylic acids (acetic and formic acids), aliphatic ketones (heptanone) and aldehydes (hexanal) were tested by means of an electropalpogram (EPG) bioassay. Our electrophysiological results showed that only acetic and formic acids evoked EPG responses. Y-shape olfactometer bioassays showed that adults were attracted by acetic and formic acids. The role of these chemicals on prey detection is discussed.