The respiratory system of Halarachne halichoeri (Halarachnidae: Gamasida: Anactinotrichida)

Halarachne halichoeri Allman (Halarachnidae: Anactinotrichida), a parasitic mite occuring in the nasal cavities of the grey seal, Halichoerus grypus , has an unusual apneustic respiratory system, which is described in detail. The main functions of this system are to facilitate gaseous (tracheal) respiration and prevent foreign material being forced into the tracheae under increased pressure experience when the host seal dives. Possible responses of the system to the rapidly changing pressure regimes are described.     

Integrative functional morphology of the gekkotan adhesive system (reptilia: gekkota)

Climbing assisted by adhesive subdigital pads in gekkotan lizardshas been the subject of intrigue and study for centuries. Manyhypotheses have been advanced to explain the mechanism of adhesion,and recently this phenomenon has been investigated at the levelof individual setae. The ability to isolate, manipulate andrecord adhesive forces from individual setae has provided newinsights, not only into the mechanism of attachment, but alsointo the physical orientation of these structures necessaryto establish attachment, maximize adhesive force, and effectsubsequent release. This, in turn, has enabled a reassessmentof the overall morphology and mode of operation of the adhesivesystem. Digital hyperextension has often been noted as a behavioralcharacteristic associated with the deployment of the gekkotanadhesive system—this is now understandable in the contextof setal attachment and release kinematics, and in the contextof the evolution of this pattern of digital movement from theprimitive pattern of saurian digital kinematics. The perpendicularand parallel preloads associated with setal attachment are nowreconcilable with other morphological aspects of the gekkotanadhesive system—the lateral digital tendon complex andthe vascular sinus network, respectively. Future investigationsof the integrated adhesive system will help to further elucidatethe interdependence of its structural and functional components.     

On the ultrastructure and functional morphology of the male chelicerae (gonopods) in Parasitina and Dermanyssina mites (Acari: Gamasida)

Males of Parasitina and Dermanyssina (Gamasida = Mesostigmata) have chelicerae modified to function as gonopods. The slit-like spermatotreme in the movable digit of the chela in males of Parasitina was studied in three species: in Pergamasus quisquiliarum and Holoparasitus sp. a rather simple slit is indeed present, whereas in Vulgarogamasus kraepelini the structure is represented by a fine duct traversing the movable digit. The spermatodactyl studied in two phytoseioid species (Phytoseiulus persimilis, Blattisocius dentriticus) of Dermanyssina is a slender process arising from the movable digit and containing a fine duct which is formed by cuticular folds. The spermatodactyl of these species thus differs remarkably from that described in Veigaia sp. The diversity of these structures seen in the few taxa studied up to now is discussed under functional and systematic aspects.     

Comparative morphology, homologies, and functions of the male system in oribatid mites (Arachnida: Acari)

The penis is basically a double-walled oval cone. The weak type penis (only 2 species) has a weak tongue, lacks a bridge, and is elongate. The strong type (all others) has a bridge, a strong tongue, thicker walls, and is short. An accessory gland and a common vas deferens always open into the inner cup lumen (= ejaculatory duct). The massive tongue muscles may open the penal orifice. A pair of penal retractor muscles originate on the body wall. Penal protrusion and perhaps partial extrusion of stalk substance is by hemolymph pressure. The penis is completely homologous to the ovipositor. The genital discs are cuticular cups containing glandular tissue and are retractible by muscles originating on the body wall. The minute, rod-like, immobile sperm are mixed with seminal fluid and stalk material secreted by seminal vesicle cells. This mixture is carried via the vase deferentia by peristalsis to the penis. Semen and stalk substance (protein) are somehow separated in the ejaculatory duct into separate pools, with stalk substance nearest the penal orifice. Upon penal protrusion, a bit of stalk material is extruded and fastened to the ground, and upon raising of the mite's body the stalk is “drawn out.” Finally, the ball of semen, adhering to the stalk tip, is pulled through the penal orifice.     

Life-cycle of Suidasia medanensis (=pontifica) (Acari: Suidasiidae) under laboratory conditions in a tropical environment

The life cycle of Suidasia medanensis (= pontifica) was studied under laboratory conditions at 26°C and 86% relative humidity. Freshly laid eggs were observed until they developed into adults and the periods between stages were recorded. Production of eggs by mated females was monitored until they died. The eggs required an average of 12.6 ± 0.6 days to develop into adults. Mean longevity of mated females and males was similar (48.6 ± 13 and 49.1 ± 20 days, respectively). The conditions used in this study may be considered optimal for in vitro culture of S. medanensis.     

The effect of temperature on the functional response of Phytoseiulus persimilis (Acari: Phytoseiidae)

Environmental variables, such as temperature, are important in determining the efficiency of biological control in ornamental crops. This paper examines the effect of temperature on the functional response of adult female Phytoseiulus persimilis to eggs of the spider mite, Tetranychus urticae. The functional response was determined using a new functional response assay technique with plant stems as an arena, rather than leaf discs. The use of plant stems allows the influence that plant structure has on predation to be incorporated into the assay. Control assays were also used (without predators) to estimate natural losses of prey. The data were analysed using a binomial model, with the use of Abbot's formula to correct for the losses in the controls. A combined equation to describe the effect of temperature and prey density on the predation rate of Phytoseiulus persimilis was derived. The results showed that more prey are eaten as the temperature increases from 15 degrees C to 25 degrees C, but the number of prey eaten then declines at 30 degrees C, although not to the levels seen at 20 degrees C. The implication of these results for biological control in ornamental crops, where the temperature can often exceed 30 degrees C, is discussed.     

Ultrastructure and functional morphology of a nematalycid mite (Acari: Actinotrichida: Endostigmata: Nematalycidae): adaptations to mesopsammal life*

Nematalycid mites have undergone extreme changes of body shape in adaptating to life in tiny spaces between grains of fine sand. Because of their minute size, the morphology of these organisms can only be reconstructed from ultrathin serial sections. The cuticle forms regular alternating palettes on the surface; such a structure may also function as a plastron. Movement of the body is effected by a continuous secondary muscle layer beneath the epidermis which operates in connection with the cuticular palettes. This movement represents a hitherto unknown mode of reptation, which can be understood as an adaptation to moving among sand particles. The appendages have been reduced to a minute size. The morphology of the digestive tract is described and conclusions are drawn concerning nutrition.     

Mating and spermatophore morphology of water mites (Acari: Parasitengona)

In this paper I synthesize original and published studies of sperm transfer behaviour of 23 genera of water mites from 15 families. The morphology of spermatophores from 16 genera (12 families) is described. Behaviour and/or spermatophores are described for the first time for the following species: Hydrachna magniscutata Marshall, Hydrachna hesperia Lundblad, Hydrachna sp. nr. leegei Koenike, Limnochares americana Lundblad, Limnesia undulata (Müller), Neumania distincta Marshall, Unionicola (three species in the U. crassipes-complex), Thyas slolli Koenike, Lebertia annae Habeeb, Lebertia sp., Piona sp. nr. debilis (Wolcott), Tiphys vernalis (Habeeb), Arrenurus dentipetiolatus Marshall, Arrenurus marshalli Piersig and Arrenurus birgei Marshall. On the basis of proximity of male and female during sperm transfer, I divide water mites into four groups: complete dissociation, involving no physical or chemical contact between the sexes (nine genera); incomplete dissociation, requiring distance-or contact-chemoreception but not involving pairing behaviour (five genera); pairing with indirect transfer, involving pairing behaviour with females controlling sperm uptake (three genera); pairing with direct transfer (=copulation), involving pairing behaviour and male placement of sperm in the receiving structure of the female (12 genera). Four genera have representative species in more than one category of sperm transfer. Factors possibly leading to the diversity of water mite mating behaviour include an evolutionarily flexible mode of sperm transfer in the ancestral water mite, and the development of planktonic and endoparasitic habits in many mites. Morphological features of spermatophores that improve physical stability, probability of females taking up sperm and resistance against osmotic stress are discussed. Finally, I present implications of mating behaviour and spermatophore morphology for phylogenetic relationships within water mites and between this group and terrestrial Acari.     

The Aristotle's lantern of the sea-urchin Stylocidaris affinis (Echinoida,Cidaridae): functional morphology of the musculo-skeletal system

Summary The Aristotle's lantern, or masticatory apparatus, of regular sea-urchins is a complex musculo-skeletal system which is thought to have contributed significantly to the evolutionary success of these animals. This paper gives an account of the antomical relationships and functional morphology of both skeletal and soft tissue components in the lantern and related structures of the sea-urchin Stylocidaris affinis (Cidaridae), and compares these features with their equivalent in the previously described lantern of the sea-urchin Paracentrotus lividus (Echinidae, Camarodonta). There are major differences in the skeletons of these lanterns which involve mostly the arrangement and morphology of elements participating in movement, i.e. joints and articular surfaces, and which highlight the generally heavier and less mobile nature of the lantern in the Cidaridae. There are remarkably few differences, however, in the microstructure of the skeletal stereom. Significant dissimilarities were found in the anatomical arrangement of muscles and ligamentous structures and in their macro- and microstructure. The implications of these morphological features for the functioning of the lantern of the Cidaridae are discussed in the context of an integrated model of lantern biomechanics.     

The functional morphology of the praying mantis forelimb (Dictyoptera: Mantodea)

The structure and function of the forelimbs of praying mantids are discussed. A large spine on the femur and the spine on the end of the tibia were shown experimentally to be important in the capture of unrestrained flies. These spines may function to narrow the gap through which a fly may escape while the tibia is closing on the femur. Some of the spines on the femur are hinged at their base; the structure, properties and possible functions of these spines are discussed.
Similar hinged spines are reported on the lorelimbs of Stomatopoda (CrustaceaI but were not found in the Mantispidac (Neuroptera:Insecta). The variation of forelimb structure within the Mantodea is briefly discussed. The theory that the optimum prev size can be predicted from the geometry of the mantid forelimb is critically discussed.     

The water vascular system and functional morphology of Paleozoic asteroids

Asteroids of all geologic ages share a single basic body form, surficial skeletal arrangement, and aspects of water vascular construction. In almost all described Paleozoic species, however, either podial pores to the interior of the arm were lacking, or they are directed laterally, above the adambulacrals. They are internal and above the ambulacrals in known post-Paleozoic species and the Pennsylvanian Calliasterella. Certain features of the ambulacral skeletal arrangement also differ. Calliasterella is the closest known Paleozoic relative of post-Paleozoic asteroids. Classifications of asteroids that stress only overall form and surticial skeletal arrangement erroneously include Paleozoic and Holocene species in common ordinal or even lower level groupings. Taxonomic revision is premature: however, most known Paleozoic asteroids represent primitive lineages. Transitional forms allow reconstruction of events leading to the modern arrangement. Ampullar and skeletal arrangements of post-Paleozoic asteroids appear to offer some functional advantages over those of their precursors, but as early as the Ordovician, diverse feeding habits had evolved and ecological roles paralleled those of Holocene species.     

Internal and external morphology of the deutonymph of Caloglyphus boharti (Arachnida: Acari)

A band of flexible cuticle encircles the deutonymph, separating the dorsal and ventral plates. The coxae are large, flat and fused with one another to form most of the ventor. Individual coxal margins are redefined as sternites, epimerites or simply apodemes according to which margins fuse with which others. A given area of cuticle may have patches of dark or light cuticle not corresponding to particular structures or cuticular contours; this is a source of confusion to taxonomists. Each leg has a dicondylic coxal-trochantal (adduction-abduction) and trochantal-femoral (promotion-remotion) joint with opposing muscles. The three more distal monocondylic joints (flexion-extension) have only flexor muscles; extension is by increased haemolymph pressure. The five apodemes of the sucker plate provide rigidity; the four suckers attach by a flexible cuticular ring to a solid flange or socket in the sucker plate. The sucker muscles attach to the center of each sucker. The flat, external face of the sucker plate apodemes may complement sucker action by adhesion. Coxal discs and sucker plate discs are identical, contain birefringent cuticular elements, and are considered modified setae. Functional mouthparts and a pharynx are lacking, but a cheliceral anlage is present. The esophagus, midgut and caecae, and malpighian tubules are lumenless and the cells small. The hindgut has a lumen, larger cells and opens externally via the anus. Whereas the digestive tract is regressed, the reproductive system is yet incompletely developed. In older deutonymphs anlagen of ducts, accessory glands and gonads are discernible. The nature of the haemocoel and peritoneum remains nuclear. The central nerve mass is conspicuously large for the size of the deutonymph. The supraesophageal ganglion gives rise to the cheliceral nerves; all other nerves arise from the subesophageal ganglion. Most major nerves were traced to the effector organs. The muscles are divided into leg, dorso-ventral (derived from coxal muscles), dorsal, sucker, and anogenital muscles. The trochantal adductor muscles originate on an endosternite, which is supported by muscles running to the dorsal hysterosoma. The dorso-ventral and propodosomal retractor muscles affect haemolymph pressure. The massive sucker retractor muscles are unique to this instar. Anogenital muscles are not well developed.     

The functional morphology of the alimentary tract of barnacles (Cirripedia: Thoracica)

The alimentary tract of barnacles is made up of cuticle-lined foregut and hindgut with an intervening U-shaped midgut associated anteriorly with a pair of pancreatic glands and perhaps midgut caeca. Epithelial salivary glands secrete acid mucopolysaccharide, glycoprotein or both. Cells of all the midgut regions are capable of absorption which is carried out mainly by the anterior midgut and caeca. Midgut cells of Balanus balanoides (L.) show a seasonal variation in the distribution of intracellular lipid droplets. Midgut cells rest on an elastic basal lamina and secrete a peritrophic membrane which contains mucopolysaccharide and protein. Cells of the stratum perintestinale connect with the midgut epithelial cells via cell processes which probably translocate absorbed materials. Glycoprotein globules and lipid droplets accumulate in the body parenchyma of B. balanoides and are transported to the ovaries to form yolk (glycolipovitellin). The pancreatic gland cells of all barnacles are active secretory cells secreting proteinaceous material (probably digestive enzymes).     

Scanning electron microscopy of the respiratory surfaces of Saccobranchus (=Heteropneustes) fossilis (Bloch)

Summary The gill secondary lamellae are generally covered with epithelial cells whose outer surfaces form numerous microvilli. The surface of the primary lamellae is characterised by microridges. A particular type of surface sculpturing seems to be associated with given cell boundaries.Further evidence for the derivation of the air tube and fans which guard its entrance by modification of the basic gill structure has been obtained from both the gross surface architecture and microstructure of the individual cell surfaces. Secondary lamellae are represented by stubby projections which generally have a biserial arrangement. The outer surfaces of the epithelia overlying the capillaries of these respiratory islets are coated with microvilli as in the secondary lamellae. On the other hand, the relatively smooth-surfaced lanes between groups of respiratory islets have a microridged surface similar to that of the primary gill lamellae.It is suggested that previous estimates of surface area, and consequently diffusing capacities of the air-breathing organ, have been low in view of the increased surface, due to both their gross and microstructure. Estimates for gill surface area may need very little correction as the spaces between the microvilli and microridges are probably filled with mucus under normal conditions.We thank Mr. John Clements for his excellent technical assistance and the Department of Botany, Bristol University for the use of their scanning electron microscope     

The morphology of the juvenile stages of two Oribatid species of the family Hermanniidae (Acari)

The morphology of all the juvenile stages of Hermannia gibba Koch, 1839 and nymphs of Phyllhermannia gladiata Aoki, 1965 (Oribatida, Hermanniidae) is described and illustrated. A key to Phyllhermannia nymphs and new diagnoses of the juvenile stages of the family Hermanniidae, and also of the genera Hermannia and Phyllhermannia are given.