Morphological comparison of the ampullae of Lorenzini of three sympatric benthic rays.

This study investigated and compared the morphology of the electrosensory system of three species of benthic rays. Neotrygon trigonoides, Hemitrygon fluviorum and Maculabatis toshi inhabit similar habitats within Moreton Bay, Queensland, Australia. Like all elasmobranchs, they possess the ability to detect weak electrical fields using their ampullae of Lorenzini. Macroscopically, the ampullary organs of all three species are aggregated in three bilaterally paired clusters: the mandibular, hyoid and superficial ophthalmic clusters. The hyoid and superficial ophthalmic clusters of ampullae arise from both dorsal and ventral ampullary pores. The dorsal pores are typically larger than the ventral pores in all three species, except for the posterior ventral pores of the hyoid grouping. Ampullary canals arising from the hyoid cluster possessed a quasi-sinusoidal shape, but otherwise appeared similar to the canals described for other elasmobranchs. Ultrastructure of the ampullae of Lorenzini of the three species was studied using a combination of light, confocal and electron microscopy. All possess ampullae of the alveolar type. In N. trigonoides and M. toshi, each ampullary canal terminates in three to five sensory chambers, each comprising several alveoli lined with receptor and supportive cells and eight to 11 sensory chambers in H. fluviorum. Receptor cells of all three species possess a similar organization to those of other elasmobranchs and were enveloped by large, apically nucleated supportive cells protruding well into the alveolar sacs. The luminally extended chassis of supportive cells protruding dramatically into the ampullary lumen had not previously been documented for any elasmobranch species.

The urticating setae of Ochrogaster lunifer, an Australian processionary caterpillar of veterinary importance.

The bag-shelter moth, Ochrogaster lunifer Herrich-Schaffer (Lepidoptera: Notodontidae), is associated with a condition called equine amnionitis and fetal loss (EAFL) on horse farms in Australia. Setal fragments from O. lunifer larvae have been identified in the placentas of experimentally aborted fetuses and their dams, and in clinical abortions. The gregarious larvae build silken nests in which large numbers cohabit over spring, summer and autumn. The final instars disperse to pupation sites in the ground where they overwinter. Field-collected O. lunifer larvae, their nests and nearby soil were examined using light and electron microscopy to identify setae likely to cause EAFL and to determine where and how many were present. Microtrichia, barbed hairs and true setae were found on the exoskeletons of the larvae. True setae matching the majority of setal fragments described from equine tissue were found on third to eighth instar larvae or exuviae. The number of true setae increased with the age of the larva; eighth instars carried around 2.0-2.5 million true setae. The exuvia of the pre-pupal instar was incorporated into the pupal chamber. The major sources of setae are likely to be nests, dispersing pre-pupal larvae and their exuviae, and pupal chambers.

The movement and distribution of Helicoverpa armigera (Hübner) larvae on pea plants is affected by egg placement and flowering.

The distribution and movement of 1st instar Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae on whole garden pea (Pisum sativum L.) plants were determined in glasshouse trials. This economically-important herbivore attacks a wide variety of agricultural, horticultural and indigenous plants. To investigate the mechanisms underlying larval intra-plant movement, we used early-flowering and wild-type plant genotypes and placed eggs at different vertical heights within the plants, one egg per plant. Leaf water and nitrogen content and cuticle hardness were measured at the different plant heights. Of 92 individual larvae, 41% did not move from the node of eclosion, 49% moved upwards and 10% moved downwards with the distance moved being between zero and ten plant nodes. Larvae from eggs placed on the lower third of the plant left the natal leaf more often and moved further than larvae from eggs placed in the middle or upper thirds. The low nutritive value of leaves was the most likely explanation for more movement away from lower plant regions. Although larvae on flowering plants did not move further up or down than larvae on non-flowering plants, they more often departed the leaflet (within a leaf) where they eclosed. The final distribution of larvae was affected by plant genotype, with larvae on flowering plants found less often on leaflets and more often on stipules, tendrils and reproductive structures. Understanding intra-plant movement by herbivorous insects under natural conditions is important because such movement determines the value of economic loss to host crops. Knowing the behaviour underlying the spatial distribution of herbivores on plants will assist us to interpret field data and should lead to better informed pest management decisions.

Hardness in arthropod exoskeletons in the absence of transition metals.

The arthropod cuticle is a remarkable and versatile biological material commonly composed of chitin and proteins. Lessons can be learned from the way it is adapted to fit its functions. The larval jewel beetle, Pseudotaenia frenchi, demonstrates hardness in the cutting edge of the mandibles in excess of the mineralized carapace of stone crabs and compares favourably with some stainless steels. Yet this is a form of cuticle which is devoid of transition metals or mineralization. In seeming contradiction, the similarly dark coloured adult beetle mandibles contain the transition metal manganese, but are significantly softer. Energy dispersive X-ray analysis and infrared spectroscopy have been used to investigate the differences in composition of mandible cuticle of the adult and larval beetles.

Structure, composition and properties of naturally occurring non-calcified crustacean cuticle.

Crustaceans are known for their hard, calcified exoskeleton; however some regions appear different in colour and opacity. These include leg and cheliped tips in the grapsid crab, Metopograpsus frontalis. The chelipeds and leg tips contain only trace levels of calcium but a significant mass of the halogens, chlorine (Cl) and bromine (Br). In contrast, the carapace is heavily calcified and contains only a trace mass of Cl and no Br. In transverse section across the non-calcified tip regions of cheliped and leg the mass percent of halogens varies with position. As such, the exoskeleton of M. frontalis provides a useful model to examine a possible correlation of halogen concentration with the physical properties of hardness (H) and reduced elastic modulus (E(r)), within a chitin-based matrix. Previously published work suggests a correlation exists between Cl concentration and hardness in similar tissues that contain a metal (e.g. zinc). However, in M. frontalis H and E(r) did not vary significantly across cheliped or leg tip despite differences in halogen concentration. The non-calcified regions of M. frontalis are less hard and less stiff than the carapace but equivalent to values found for insect cuticle lacking metals. Cheliped tips showed a complex morphological layering that differed from leg tips.

Discrepancy between antennal and behavioral responses for enantiomers of alpha-pinene: electrophysiology and behavior of Helicoverpa armigera (Lepidoptera).

The ability of adult cotton bollworm, Helicoverpa armigera (Hübner), to distinguish and respond to enantiomers of alpha-pinene was investigated with electrophysiological and behavioral methods. Electroantennogram recordings using mixtures of the enantiomers at saturating dose levels, and single unit electrophysiology, indicated that the two forms were detected by the same receptor neurons. The relative size of the electroantennogram response was higher for the (-) compared to the (+) form, indicating greater affinity for the (-) form at the level of the dendrites. Behavioral assays investigated the ability of moths to discriminate between, and respond to the (+) and (-) forms of alpha-pinene. Moths with no odor conditioning showed an innate preference for (+)-alpha-pinene. This preference displayed by naive moths was not significantly different from the preferences of moths conditioned on (+)-alpha-pinene. However, we found a significant difference in preference between moths conditioned on the (-) enantiomer compared to naive moths and moths conditioned on (+)-alpha-pinene, showing that learning plays an important role in the behavioral response. Moths are less able to distinguish between enantiomers of alpha-pinene than different odors (e.g., phenylacetaldehyde versus (-)-alpha-pinene) in learning experiments. The relevance of receptor discrimination of enantiomers and learning ability of the moths in host plant choice is discussed.

Mechanism of adhesion and detachment at the anterior end of Merizocotyle icopae (Monogenea: Monocotylidae) including ultrastructure of the anterior adhesive matrix.

The anterior adhesive mechanism was studied for Merizocotyle icopae (Monogenea: Monocotylidae). Adult anterior apertures can open and close. In addition, duct endings terminating within the apertures are everted or retracted depending on the stage of attachment. Adhesive in adults is synthesized from all 3 secretory types (rod-shaped, small and large spheroidal bodies) found within anterior apertures. All exit together and undergo mixing to produce the adhesive matrix, a process that depletes duct contents. A greater number of ducts carrying rod-shaped bodies is depleted than ducts containing spheroidal bodies which changes the ratio of secretory types present on detachment. Detachment involves elongation of duct endings and secretion of additional matrix as the worm pulls away from the substrate. The change in secretory type ratio putatively modifies the properties of the secreted matrix enabling detachment. Only after detachment do ducts refill. During attachment, individual secretory bodies undergo morphological changes. The larval and adult adhesive matrix differs. Anterior adhesive in oncomiracidia does not show fibres with banding whereas banded fibres comprise a large part of adult adhesive. The data suggest that this is the result of adult spheroidal secretions modifying the way in which the adult adhesive matrix forms.

Mechanism of adhesion and detachment at the anterior end of Neoheterocotyle rhinobatidis and Troglocephalus rhinobatidis (Monogenea: Monopisthocotylea: Monocotylidae).

The anterior adhesion and detachment mechanisms observed for Neoheterocotyle rhinobatidis and Troglocephalus rhinobatidis (Monogenea: Monocotylidae) appear similar to those observed for the two other monopisthocotylean monogenean species with anterior apertures for which published data are available. This supports the theory that monogeneans with apertures may utilise a common mechanism. Adult anterior apertures can open and close and duct endings can evert during the adhesion phase and retract during detachment and searching behaviour. The adhesive is comprised of two secretory types, rod-shaped and spheroidal bodies, found within anterior apertures. These exit together and undergo mixing to produce the adhesive matrix in which elongate membranes from rod-shaped bodies are seen intermixed with a granular electrondense matrix. The morphology of the adhesive matrix differs from that found for some other monogenean taxa. Anterior detachment by these monocotylids appears to involve a depletion of rod-shaped bodies in ducts and mechanical withdrawal of the anterior end.

A comparison of the anterior adhesive system in the oncomiracidium and adult of the monogenean parasite Menizocotyle icopae (Monocotylidae).

The anterior adhesive system of the oncomiracidium and adult of Merizocotyle icopae (Monogenea: Monocotylidae) were compared. The oncomiracidium has one ventrally placed aperture on either side of the head near the anterior extremity. In the adult, there are three ventrally placed apertures on either side of the head region. Both systems have three types of electron-dense secretory bodies opening into each aperture. A rod-shaped secretion (S1) and a small electron dense ovoid secretion (S2) are common to larvae and adults. The third secretion type differs: in adults, it is a large, spherical (S3) type but in larvae, it is an ovoid (S4) body. S4 bodies do occur in adults, but appear to be secreted as a general body secretion. An additional anteromedian secretion (S5) is also present in the oncomiracidium, but is not secreted into the anterior apertures. Homology and function of secretions are discussed.

Olfaction in the Queensland fruit fly, Bactrocera tryoni. I: Identification of olfactory receptor neuron types responding to environmental odors.

The electroantennogram method was used to investigate the number of distinct olfactory receptor neuron types responding to a range of behaviorally active volatile chemicals in gravid Queensland fruit flies, Bactrocera tryoni. Three receptor neuron types were identified. One type responds to methyl butyrate, 2-butanone, farnesene, and carbon dioxide; a second to ethanol; and a third to n-butyric acid and ammonia. The receptor neuron type responding to methyl butyrate, 2-butanone, farnesene, and carbon dioxide consists of three subtypes. The presence of a limited number of receptor neuron types responding to a diverse set of chemicals and the reception of carbon dioxide by a receptor neuron type that responds to other odorants are novel aspects of the peripheral olfactory discrimination process.

Olfaction in the Queensland fruit fly, Bactrocera tryoni. II: Response spectra and temporal encoding characteristics of the carbon dioxide receptors.

Single-unit electrophysiology was used to record the nerve impulses from the carbon dioxide receptors of female Queensland fruit flies, Bactroera tryoni. The receptors responded to stimulation in a phasic-tonic manner and also had a period of inhibition of the nerve impulses after the end of stimulation. at high stimulus intensities. The cell responding to carbon dioxide was presented with a range of environmental odorants and found to respond to methyl butyrate and 2-butanone. The coding characteristics of the carbon dioxide cell and the ability to detect other odorants are discussed, with particular reference to the known behavior of the fly.

Adhesive secretions in the Platyhelminthes.

This review is the first to draw together knowledge about bioadhesives secreted by a group of parasites. Mechanisms of mechanical attachment are well known among parasites, but some can also attach to host surfaces by chemical means using a thin layer of adhesive material secreted at the parasite-host interface. Attachment by adhesives to living surfaces has not been studied in detail previously. A significant volume of research has determined much about the chemistry and nature of bioadhesives secreted by various marine macroinvertebrates from different phyla for attachment to inert substrates. Mussels and barnacles are sessile and adhere permanently, whereas starfish display temporary but firm adhesion during locomotion, feeding and burrowing. We focus on the Platyhelminthes that comprises the largely free-living Turbellaria and the wholly parasitic Monogenea, Cestoda, Digenea and Aspidogastrea. The term tissue adhesion is introduced to describe attachment by adhesives to epithelial surfaces such as fish epidermis and the lining of the vertebrate gut. These living layers regenerate rapidly, secrete mucus, are a site for immune activity and are therefore especially hostile environments for organisms that inhabit them, presenting a significant challenge for adhesion. Not all platyhelminths adhere to living surfaces and types of adhesion to inert substrates by the free-living turbellarians are also reviewed. Tissue adhesion is particularly well exemplified by monopisthocotylean monogeneans, parasites that are especially mobile as larvae, juveniles and adults on the epidermis of the body and gill surfaces of fish. These monogeneans secrete adhesives from the anterior end when they move from site to site, but some have secondarily developed adhesives at the posterior end to supplement or replace mechanical attachment by hooks and/or by suction. The temporary but tenacious anterior adhesives of monogeneans display remarkable properties of instant attachment to and detachment from their host fish surfaces. In contrast to the mobility of turbellarians and monopisthocotylean monogeneans and the simplicity of their direct life cycles, the largely endoparasitic Cestoda and Digenea are considered to be less mobile as adults. The complex cestode and digenean life cycles, involving intermediate hosts, place different demands on their various stages. Diverse, mostly anterior, gland cells in larvae, metacestodes and adults of the true tapeworms (Eucestoda), and in larval and adult Gyrocotylidea and Amphilinidea are reviewed. Conspicuous gland cells, mostly but not exclusively at the anterior end, in miracidia, cercariae and adults of digeneans and in cotylocidia and adults of aspidogastreans are also reviewed. Unlike turbellarians and monogeneans, accounts of unequivocal adhesive secretions in the Cestoda, but especially in the Digenea and Aspidogastrea, are relatively rare. The primary purpose of many conspicuous glands in the different stages of these mostly endoparasitic flatworms is for penetration into, or escape from, different hosts in their life cycle. We provide a detailed review of current knowledge about adhesion (in the sense of a thin layer of chemical material) in the Platyhelminthes including uses among eggs, larval, juvenile and adult stages. Information on structure, morphology and ultrastructure of the various adhesive systems that have been described is reviewed. Application of the 'duo gland' model is discussed. Comparisons are made between the little that is known about the chemistry of flatworm adhesives and the significant knowledge of the chemical nature of other invertebrate bioadhesives, especially those from marine macroinvertebrates. The potential importance of adhesives in parasitism is discussed. (ABSTRACT TRUNCATED)

Host-specificity of monogenean (platyhelminth) parasites: a role for anterior adhesive areas?

Monogeneans (flatworms) are among the most host-specific of parasites in general and may be the most host-specific of all fish parasites. Specificity, in terms of a restricted spatial distribution within an environment, is not unique to parasites and is displayed by some fungi, insects, birds, symbionts and pelagic larvae of free-living marine invertebrates. The nature of cues, how "habitats" are recognised and how interactions between partners are mediated and maintained is of interest across these diverse "associations". We review some experiments that demonstrate important factors that contribute to host-specificity at the level of infective stages (larvae of oviparous monogeneans; juveniles of viviparous gyrodactylids) and adult parasites. Recent research on immune responses by fish to monogenean infections is considered. We emphasise the critical importance of host epidermis to the Monogenea. Monogeneans live on host epidermis, they live in its products (e.g. mucus), monopisthocotyleans feed on it, some of its products are "attractants" and it may be an inhospitable surface because of its immunological activity. We focus attention on fish but reference is made to amphibian hosts. We develop the concept for a potential role in host-specificity by the anterior adhesive areas, either the specialised tegument and/or anterior secretions produced by monogeneans for temporary but firm attachment during locomotion on host epithelial surfaces. Initial contact between the anterior adhesive areas of infective stages and host epidermis may serve two important purposes. (1) Appropriate sense organs or receptors on the parasite interact with a specific chemical or chemicals or with surface structures on host epidermis. (2) A specific but instant recognition or reaction occurs between component(s) of host mucus and the adhesive(s) secreted by monogeneans. The chemical composition of fish skin is known to be species-specific and our preliminary analysis of the chemistry of some monogenean adhesives indicates they are novel proteins that display some differences between parasite families and species.

Oviposition and maintenance of Forcipomyia (Lasiohelea) townsvillensis (Diptera: Ceratopogonidae) in the laboratory.

Fecundity, oogenesis, oviposition, and percentage egg hatch were quantified for the blood-feeding midge Forcipomyia (Lasiohelea) townsvillensis (Taylor). Data are similar to that reported for other species of blood-feeding Forcipomyia. Eggs rarely developed from a partial blood meal but invariably developed after a single, complete blood meal. Results suggest that this species is anautogenous. Oviposition media were investigated and a successful medium and holding chamber type identified. Longevity of adults in the laboratory was studied and indicates the possibility for >1 gonotrophic cycle to occur. Adult survival at different relative humidities showed midges can survive 35-98% RH. Rearing of larvae in the laboratory and culture media are discussed. The data supplied in this paper provide the basis for the laboratory culture of F. (L.) townsvillensis.

Morphology and ultrastructure of the anterior adhesive areas of the capsalid monogenean parasites Benedenia rohdei from the gills and B. lutjani from the pelvic fins of Lutjanus carponotatus (Pisces: Lutjanidae).

The anterior adhesive areas of Benedenia rohdei from the gills and B. lutjani from the pelvic fins of Lutjanus carponotatus at Heron Island, Australia, were studied using scanning and transmission electron microscopy. All specimens were fixed when detached from host tissue. Both monogenean species have two disc-like anteroventral attachment organs, each of which has an anterolateral adhesive area divided into three adjacent zones by tegument from the ventral surface of the attachment organ. A rod-shaped secretion and a smaller, roughly spherical secretion are associated with the anterior adhesive areas in both species; a third type of secretion occurs anteriorly but outside these adhesive areas. The electron-dense spherical secretory bodies released onto the anterior adhesive zones in these Benedenia spp. are of a single type and differ ultrastructurally from those previously reported in monogeneans living on teleost hosts. A correlation, therefore, between secretion morphology and host type is not supported. No relationship was found between parasite microhabitat and secretion morphology.

Observations on the ultrastructure of the anterior adhesive areas and other anterior gland cells in the monogenean Merizocotyle australensis (Monocotylidae) from the nasal fossae of Himantura fai (Dasyatididae).

The anterior adhesive areas of a monocotylid monogenean, Merizocotyle australensis (Merizocotylinae), were investigated. They comprise 6 ventral apertures in 2 groups of 3 arranged at the anterolateral margins of the head. These regions are also well supplied with groups of cilia. Each aperture is 13.8 to 15.8 microm wide and contains multiple tubular projections that are covered with microvilli through which open 2 types of secretory cell ducts that carry either rod-shaped or spherical secretory bodies. The gland cell bodies that produce these 2 types of secretions co-occur at the anterior end. The 2 types of secretory bodies occur adjacent to one another and both are present in the extruded adhesive. The membranes of rod-shaped bodies are retained in the extruded glue. Rod-shaped bodies are 390 +/- 18 nm wide, at least 10.9 microm long, and show 2 types of internal periodic banding: 10.6 nm and 143 +/- 3 nm. The spherical vesicles are 130 +/- 6 nm in diameter and are electron-dense. A third secretion is present in separate ducts that also open anteriorly but emerge through the tegument between the ventral apertures. This secretion does not appear to be part of the adhesive secretion. The bodies of the third secretion are elongate, electron-dense, and 374 +/- 23 nm long. Inside the "lip" of the aperture, general body tegument abuts tegument specific to the aperture. The general body tegument is thicker, contains electron-dense vesicles, and has a ridged surface devoid of microvilli. Where the 2 kinds of tegument meet, they are connected by septate desmosomes.

Glands associated with the anterior adhesive areas of the monogeneans, Entobdella sp. and Entobdella australis (Capsalidae) from the skin of Himantura fai and Taeniura lymma (Dasyatididae).

Using scanning and transmission electron microscopy, investigations were carried out on the anterior adhesive areas of Entobdella sp. from the skin of Himantura fai and Entobdella australis from the skin of Taeniura lymma at Heron Island, Australia. All studies were of parasites detached from either host tissue or a substrate. Both species of monogeneans have two characteristic anteroventral adhesive pads, one on either side of the head, subdivided to a "diadem". Two types of gland cells are associated with the anterior adhesive areas in both species and each cell type produces a different secretion: a rod-shaped secretion and a smaller, roughly spherical secretion. Each secretion type differs in electron-density, with those putatively in the process of formation being less electron-dense. Both types of secretory bodies are membrane-bound. Microtubules are evident around forming rod-shaped bodies. The bounding membranes of the rods of both species show a periodic banding of approximately 12 nm. Both types of secretion are present at the surface of the adhesive pads in specimens of Entobdella sp. fixed when detached from the host. The secretory bodies observed in Entobdella sp. and E. australis from rays show some differences to those reported from Entobdella soleae, a parasite of a flatfish teleost. Other ultrastructural differences also exist. We conclude that the types of adhesive secretory bodies may remain constant within genera providing the hosts are similar.

Ultrastructure of the eggs of Culicoides molestus (Diptera: Ceratopogonidae).

The eggs of Culicoides molestus (Skuse) are described and illustrated by scanning and transmission electron microscopy. Eggs are elongate with a slight dorsoventral curvature. No outer chorionic tubercles are present. Aeropyles are present in large numbers at the anterior end and in lower numbers at the posterior end and lateral regions. The chorion has 5 layers. An outer, rough, proteinaceous layer covers a smoother inner surface, which in turn encloses a layer of columns and meshwork that appears capable of containing air. These columns are underlain by an additional 2 layers. The aeropylar region, in combination with the chorionic meshwork, appears to provide a plastron that may aid in the survival and development of inundated eggs.

Observations on ultrastructure of the anterior adhesive areas and other anterior glands in the monogenean, Monocotyle spiremae (Monocotylidae), from the gills of Himantura fai (Dasyatididae).

Observations with the light microscope and the scanning and transmission electron microscopes have shown that the anterior end of Monocotyle spiremae has 8 slit-like apertures on the ventrolateral margins at each side of the mouth. Gland cells located next to the pharynx produce rod-shaped secretory bodies that are conveyed in ducts that open on to the surfaces of rounded lobes inside "reservoirs" behind each ventral, slit-like aperture. Rod-shaped secretory bodies are extruded into the "reservoirs" and appear to combine and form a homogeneous secretion which may bond the ventrolateral regions of the head of the parasite to a substrate. At no stage, however, were intact rods observed outside the duct endings. Gland cells that produce an ovoid secretory body also supply the head of M. spiremae, but ducts from these open dorsal and anterior to the mouth in a region where the parasite is not known to attach. There appears to be little or no chance for the ventral rods and the dorsal ovoid secretion to mix. This is the first record of a monogenean parasite with a single type of secretion supplying the ventral surfaces of the anterior end. The rods in M. spiremae differ in some respects from the rod-shaped bodies recorded previously among gyrodactylid, dactylogyrid, capsalid and acanthocotylid monogeneans.

Reappraisal of the pore channel system in the grooved pegs of Aedes aegypti.

Pore channels occur along the grooves of lactic acid-receptive grooved pegs on the antennae of female Aedes aegypti. There are about 38 pore openings per groove or about 456 per peg. This finding is in conflict with the previous report that pore channels were extremely rare. The pore channels are of a similar electron density to the cuticle of the peg, making them difficult to see. For this reason many of the pore channels were probably overlooked in the previous study. We could not find a terminal pore in the grooved peg as has been reported. Scanning electron microscopy and negative staining of the pegs revealed a tip of variable shape, usually without a pore. It is possible that 'edge effect' (more secondary electrons escape from edges of objects, making them appear brighter than central regions) leads to an apparent terminal pore. Occasionally pegs have a number of small (20-40 nm) pores in the tip region and these might also have been misinterpreted as a terminal pore. Pore channels appear to be the primary means of entry for air-borne stimuli in these grooved pegs.