Acoustic concomitants of the defensive discharges of a primitive bombardier beetle (Metrius contractus)

Summary. Metrius contractus, a primitive paussoid bombardier beetle, emits its defensive quinonoid froth with accompanying sound (a faint “hiss”), but the sound is not pulsed, indicating that the secretory emission itself is not pulsed. Pulsed secretory delivery in bombardier beetles appears to occur in Brachinini only. Received 8 July 2001; accepted 23 July 2001.     

Chemical trail communication in the amblyoponine species Mystrium rogeri Forel (Hymenoptera, Formicidae, Ponerinae)

Summary. Workers of the amblyoponine species Mystrium rogeri employ trail communication during recruitment to food sources and new nest sites. The trail pheromone originates from a hitherto unknown sternal gland located in the 7th abdominal sternite. The recruiting ant deposits the gland secretions by a special gaster-dragging behavior. The recruitment behavior can be complemented by a rapid vertical body shaking performed by some recruiting ants inside the nest. M. rogeri workers possess a large pygidial gland, the secretion of which elicits a repellent response in other ant species. Received 25 May 1998; accepted 15 June 1998.     

Seminal fluid enhances sperm viability in the leafcutter ant Atta colombica

The seminal fluid that accompanies sperm in ejaculates has been shown or suggested to affect sperm competition and paternity success of insects by preventing female remating, inducing oviposition, and forming mating plugs. In Atta leafcutter ants, queens have multiple mates but never remate later in life, although they may live and produce fertilized eggs for several decades. The mating biology and life history of these ants therefore suggests that the major function of seminal fluid is to maximize sperm viability during copulation, sperm transfer, and initial sperm storage. We tested this hypothesis by comparing the viability of testis sperm and ejaculated sperm (mixed with seminal fluid) and found a significant positive effect of seminal fluid on sperm viability. We further quantified this positive effect by adding accessory gland secretion (a major component of seminal fluid) in a dilution series, to show that minute quantities of accessory gland secretion achieve significant increases in sperm viability. Sperm stored by queens for 1 year benefited in a similar way from being exposed to accessory gland compounds after dissection in control saline solution. Our results provide the first empirical evidence that seminal fluid is important for the production of viable ejaculates and that the accessory glands of Atta males—despite their small size—are functional and produce a very potent secretion.     

Chemical ornaments of male lizards <Emphasis Type="Italic">Psammodromus algirus</Emphasis> may reveal their parasite load and health state to females

Evidence for parasite-mediated sexual selection has been found in many species that use visual ornaments to attract females. However, in many animals, variation in female responses to scents of parasitized males suggests that parasitic infections might also affect information conveyed by pheromones (i.e., chemical ornaments). Thus, pheromones might also function in parasite-mediated sexual selection. We show here that female lizards Psammodromus algirus responded differently to femoral gland secretions of males according to the parasite load and health of these males. Scents of healthier males elicited more tongue flicks (a chemosensory behavior) by females, suggesting that these scents were more attractive. Chemical analyses showed that parasite load and the T-cell-mediated immune response were related to the variability in the proportions of some lipids in secretions of males. Further trials testing the chemosensory responses of females to chemical standards indicated that females actually discriminated the chemicals related to males’ health from other chemicals found in secretions. We suggest that these chemical ornaments may provide reliable information on the health and degree of parasitic infection of a male.     

Structure and function of the eversible glands of the aquatic firefly <Emphasis Type="Italic">Luciola leii</Emphasis> (Coleoptera: Lampyridae)

Summary. When attacked or otherwise disturbed, larvae of the aquatic firefly Luciola leii display fork-shaped glands laterally from the meso- and metathorax as well as each abdominal segment. Glandular eversion is accompanied by a strong pine oil-like odour, thanatosis and glowing from paired larval light organs. Observations by SEM and TEM revealed that there are numerous, almost spherical protuberances, measuring 9 μm in diameter on the surface of each gland. Each protuberance is connected to a well developed secretory cell via a 0.1 μm thick and 0.2 μm long stalk and bears three to six 7 μm long spines on its apex. The convoluted glandular walls measure 0.2 μm. The cytoplasm of the secretory cells is characterized by the presence of numerous mitochondria and an extensive system of cisternae and tubular endoplasmic reticulum. Preliminary GC-MS analysis of the glandular secretion revealed two volatile terpenoids: terpinolene and γ-terpinene. Choice and no-choice bioassays involving fish and ants as well as other predators demonstrate that the secretions serve as an effective deterrent against a range of ecologically relevant enemies. The larval postural adjustments, light emission, everted glands, and glandular release of distasteful or repellent compounds, appear to function as a multi-modal, aposematic larval defence. The tandem evolution of glandular secretions and conspicuousness in larval fireflies could partially explain their successful radiation into both aquatic and terrestrial habitats.     

Complexity of seminal fluid: a review

The seminal fluid is a complex medium containing a great variety of molecules, mainly produced by sex accessory glands, and also cells other than spermatozoa (e.g. leucocytes). In this paper, I review current knowledge on composition of seminal fluid in both vertebrates (mainly mammals) and invertebrates (mainly insects) with internal fertilisation, in the light of possible benefits of seminal fluid components to males (e.g. sperm capacitation, sperm competition and fertilisation), possible costs to males (e.g. autoimmunity, antigenic effects), potential benefits to females being inseminated (e.g. food, immunostimulation and antibiotic effects) and potential costs to females (e.g. transmission of venereal diseases). The diversity of microorganismal, cellular and molecular components of seminal fluids can be interpreted in the light of emergence of co-adapted complexes, host–parasite coevolution, male–female arms races, sperm competition, pleiotropy and redundancy of function.     

A trail pheromone component of the African stink ant, Pachycondyla (Paltothyreus) tarsata Fabricius (Hymenoptera: Formicidae: Ponerinae)

Summary. The African stink ants (Pachycondyla tarsata) lay recruitment trails with secretions from sternal glands. The glandular secretions consist of 10 compounds, 9 of which have been chemically identified. One of the substances, 9-heptadecanone, elicits trail following behavior in P. tarsata workers that have before been stimulated by a sucessful scout ant. Received 7 August 1998; accepted 24 November 1998.     

Genotoxic effects of metals on human salivary gland tissue and lymphocytes as detected by the Comet assay

The etiology of salivary gland malignancies still remains unclear. Metal compounds are of special interest since they show ubiquitous presence in the environment, are present in many working places, and are accepted (co-)carcinogens in some other malignancies. Metals enter the body as xenobiotics by inhalation or ingestion. This study investigated the genotoxic potential of sodium dichromate (Na₂Cr₂O₇), nickel sulfate (NiSO₄), cadmium sulfate (CdSO₄) and zinc chloride (ZnCl₂) on human salivary gland cells and lymphocytes. Macroscopically healthy tissue of salivary glands was harvested from 46 patients during surgery and isolated to single cells by enzymatic digestion. The cells were incubated with Na₂Cr₂O₇, NiSO₄, CdSO₄ or ZnCl₂. Na₂Cr₂O₇ was also incubated in combination with the other metal compounds listed. Carcinogenic and co-carcinogenic effects of cadmium were tested by incubation with Na₂Cr₂O₇ and consecutive repair intervals. DNA damage and repair were evaluated by the Comet assay, determining DNA-strand breaks. The extent of damage was quantified using a digital analysis system. Na₂Cr₂O₇ produced significantly enhanced DNA-strand breaks in human salivary gland tissue and lymphocytes. All other metal compounds exerted no damaging effect on both cell types. Co-incubation of Na₂Cr₂O₇ with the other metals revealed a significant additive effect only for CdSO₄. Specific analysis of the influence of cadmium showed a reduction of DNA-repair after Na₂Cr₂O₇-induced strand breaks in salivary gland cells. This study provides evidence that exposure to distinct metals may significantly contribute to malignant salivary gland tumors. In consequence, further studies as epidemiological and toxicological data are warranted to determine the role of distinct metals as potential (co-) carcinogens.     

Aggressive reproductive competition among hopelessly queenless honeybee workers triggered by pheromone signaling

In the honeybee, Apis mellifera, the queen monopolizes reproduction, while the sterile workers cooperate harmoniously in nest maintenance. However, under queenless (QL) conditions, cooperation collapses and reproductive competition among workers ensues. This is mediated through aggression and worker oviposition, as well as shifts in pheromones, from worker to queen-like composition. Many studies suggest a dichotomy between conflict resolution through aggression or through pheromonal signaling. In this paper, we demonstrate that both phenomena comprise essential components of reproductive competition and that pheromone signaling actually triggers the onset of aggression. We kept workers as QL groups until first aggression was observed and subsequently determined the contestants' reproductive status and content of the mandibular (MG) and Dufour's glands (DG). In groups in which aggression occurred early, the attacked bee had consistently more queen-like pheromone in both the MG and DG, although both contestants had undeveloped ovaries. In groups with late aggression, the attacked bee had consistently larger oocytes and more queen-like pheromone in the DG, but not the MG. We suggest that at early stages of competition, the MG secretion is utilized to establish dominance and that the DG provides an honest fertility signal. We further argue that it is the higher amount of DG pheromone that triggers aggression.     

Oily substances from gastral intersegmental glands of the antPachycondyla tridenta (Ponerinae): Lack of pheromone function in tandem running and antibiotic effects but further evidence for lubricative function

Summary Gas chromatographic analyses of volatizable material from gaster intersegmental complex glands ofP. tridentata revealed the presence of linoleic acid, palmitic acid, methyl oleate, and several long-chain hydrocarbons as major constituents, which form an oily fluid mixture. The nest relocation communication ofP. tridentata is tandem running. Tandem following is mediated by pheromones as demonstrated by dummy experiments with isolated gasters and thoraces and with glass balls. The secretions of all gaster complex glands, as well as hind gut contents and metapleural gland secretions, were unable to evoke tandem following. Morphology and position of the glands, lack of pheromonal function, oily properties, low volatility, and lack of antibiotic effects of these secretions strongly suggest a function as lubricants for the ants' gastral segments.