Eye Structure and Vision in the Freshwater Pulmonate Mollusc Planorbarius corneus

The structure of the mollusc Planorbarius corneus eye was studied using light and electron microscopy. The eye consists of the cornea, eye lens of non-spherical shape, and the vitreous body tightly bound to it, as well as of a monolayer non-inverted retina composed of photoreceptor and supporting (pigmented) cells. Its inner surface has two invaginations. The apices of several hundreds of photoreceptors directed to the vitreous body have groups of microvilli with a parallel orientation to each other. The eye optic system places the image into the base of the retinal microvillar layer. Its angle resolution provided by density of distribution of photoreceptor cells and the value of the index F = 1.71 is to be about 2.06° with a correction for the light spreading between microvilli of neighbor cells. Under conditions of a V-shaped labyrinth, the P. corneus molluscs show positive phototaxis by moving to the light source. The angular acuity of vision was assessed from differences in the choice by the molluscs of direction of movement to the pattern of vertical black bands with different periods of alternation. The differential threshold obtained is within an interval of 1.43–1.91°, which is close to the calculated value of angular resolution of the retina.     

Gravity reception in the walking fly, Calliphora erythrocephala: Tonic and modulatory influences of leg afferents on the head position

The proprioceptive gravity receptor system of the fly, Calliphora erythrocephala, is functionally organized in a manner similar to the statocyst system in vertebrates, molluscs and crustaceans. It includes one system in which excitation is modulated by the gravitational stimulus, and another which exerts a tonic excitation on the neurones of the reflex arc between the leg receptors and the neck muscles. While the modulating system for the compensatory head movement of the walking flies is located only in the forelegs and the middle legs, the tonic excitation is mediated by receptors of all legs.     

Vertical segregation of holoplanktonic molluscs in the epipelagic layer, southern Gulf of Mexico

The small-scale vertical distribution of five genera of holoplanktonic molluscs inhabiting the upper oceanic layer (0–105 m) was analysed to test whether evident distribution patterns could be attributed to habitat partitioning. Zooplankton samples were taken over neritic waters during the day and night using a 505-μm multiple closing net at five levels (0–6, 6–12, 12–18, 45–55 and 95–105 m) of the water column. Flowmeters were placed in each net to estimate the amount of filtered water. From the 55,654 identifiable specimens of holoplanktonic molluscs, only 6.2 % were in juvenile stage, and Cavolinia, Diacavolinia, Diacria, Oxygyrus and Clio were the most abundant genera. Adults of these genera comprised 3 % of the total abundance. The abundance data were examined using a spatial segregation index, and its significance was tested with null model methods based on Monte Carlo randomizations. Results indicated that adults showed a much more overlapped distribution in the water column than the in the earlier stages. Indeed, juveniles of Cavolinia, Diacavolinia and Oxygyrus were mainly found in the 0–18-m layer, whereas Diacria and Clio were recorded in the 45–105-m stratum. Null model arguments revealed a significant vertical segregation among them. Potential ecological factors involve preferential spawning areas of adults, avoidance of competition for feeding and spatial resources, use of visual capabilities in searching prey, brood protection and avoidance of strong turbulence conditions.     

Effect of habitat and motor activity of molluscs on fatty acid composition of triglycerides and phospholipids

A comparative analysis of fatty acids (FA) in neutral lipids and phospholipids of digestive gland and pedal muscle has been performed in molluscs from various ecological groups differing by belonging to sea or fresh water, trophic types or the associated motor activity. In freshwater pulmonary gastropods Lymnaea stagnalis and Lymnaea ovalis and marine prosobranchial molluscs Buccinum undatum and Littorina littorea the total content of ω3-acids in phospholipids of the studied tissues differed more than twice, predominantly due to the combined effect of temperature and salinity of the habitat. The lower viscosity of cell membranes in marine species (ω3/ω6 < 1) is determined to the greatest degree by the presence of eicosapentaenoic acid that accounts for 22–25% of the FA sum in marine species. Comparison of the molluscs by their trophic belonging has revealed the presence of linoleic acid in triglycerides in digestive glands of phytophages (8–12%), but the practically complete absence of this acid in the predator B. undulatum (< 0.8%). By mobility, L. littorea inhabiting the high-low tide littoral was inferior to freshwater pulmonary gastropods and to the marine predator, as it stops moving twice a day during the low tide. In phospholipids of pedal muscle of this mollusc the amount of long-chain polyunsaturated C: 22 FA was 3–6 times lower than that in other studied species, which might possibly indicate the role of these acids in functioning of the pedal muscle contractile tissue. On the whole, use of the FA characteristics as the parameters determining belonging to certain ecological group requires a certain caution due to a complex action of biotic and abiotic factors on the animal metabolism. The exception is the ω3/ω6 ratio in total phospholipids of fresh water and marine gastropods.     

Different Level of Intraspecific Variation of the Bony Labyrinth Morphology in Slow- Versus Fast-Moving Primates

The vestibular system of the inner ear detects the motions of the head and is involved in maintaining balance. For this reason, this organ has been deeply studied and several scientists have tried to link its morphology with the locomotor behavior of an animal. Via high-resolution computed microtomography and geometric morphometric methods, we analyzed the intraspecific variation of the 3D morphology of the bony labyrinth (inner ear) in four species of primates differing in their locomotor adaptations: two being slow-moving taxa (Nycticebus and Perodicticus), and two being fast-moving taxa (Callithrix and Microcebus). Basically, there are very few analyses of the inter-individual variation of this organ in mammals in general, and this approach has never been attempted in primates thus far. Our results show that variation of the bony labyrinth morphology is expressed by the same ways in the different species (e.g., differences in the size, shape, and orientation of the semicircular canals, and in the width and height of the cochlea), but that slow-moving taxa exhibit a higher amount of intraspecific variation than do fast-moving taxa. Our results strengthen support for a previously published hypothesis, according to which a relaxation of the selective pressure applied to the morphology of the bony labyrinth is the likely reason for this higher amount of intraspecific variation in slow-moving taxa, and that it may be related to a reduced functional demand for rapid postural adjustments.     

Fungal depsidones – an inducible or constitutive defence against herbivores in the lichen Lobaria pulmonaria?

Herbivore-deterrent depsidones in the epiphytic lichen Lobaria pulmonaria were quantified after a 104-day exposure to indigenous lichen-feeding mollusc communities in broadleaved deciduous forests in southeastern Norway. Controls and acetone-rinsed living thalli were transplanted under open and shaded tree canopies. Rinsed thalli had their depsidone concentration reduced to 36% of the pre-rinsing level, which is below the level needed to deter grazing molluscs. Grazing did not raise the concentration of depsidones beyond the level occurring in control to which molluscs had no access. Inducible responses were not detected in controls nor in acetone-rinsed thalli. Depsidone resynthesis was negligible in acetone-rinsed thalli regardless of grazing and/or light regimes. Our results suggest that C-based depsidones represent a constitutive type of herbivore defence in L. pulmonaria. A constitutive defence is probably an advantage for stress-tolerant slow-growing lichens inhabiting habitats with a constant presence of generalist invertebrate herbivores.     

The inner ear of <Emphasis Type="Italic">Protungulatum</Emphasis> (Pan-Euungulata,Mammalia)

We present new anatomical details about the bony labyrinth of Protungulatum based on micro CT-scan investigation of an isolated petrosal bone retrieved at the Puercan locality of Bug Creek Anthills and referred to Protungulatum sp. The exceptional state of preservation of the specimen allowed us to reconstruct the very fine details of the inside of the petrosal bone, including the bony labyrinth, the innervation of the vestibule and the innervation and vasculature of the cochlea. Estimation of the auditory capability of Protungulatum based on cochlear morphology indicate that Protungulatum was specialized for high-frequency hearing, with estimated low frequency limits above 1 KHz. Comparisons with Late Cretaceous non-placental eutherians and with early Tertiary pan-euungulates indicate that the bony labyrinth of Protungulatum is closer in general morphology to Mesozoic forms (low coiling and low aspect ratio of the cochlea, posterior orientation of the common crus, dorsal outpocketing of the cochlear fossula), and shares only a few characters with pan-euungulate and euungulate taxa. Interestingly, the bony labyrinth of Protungulatum also shares some morphological features with South American notoungulates and litopterns recently described from Itaboraí, Brazil. These new observations provide new morphological features of potential phylogenetic interest.     

Zonal migration and trail‐following of an intertidal gastropod analyzed by led tracking in the field

A new technique is described for the continuous recording of the movements of intertidal molluscs in the field. Photographic monitoring of snails equipped with LEDs powered by small batteries revealed that the prosobranch gastropod Nerita textilis adopts a hybrid (zonal‐homing) pattern including a definite trail‐following behaviour. The method allowed the study of individual feeding migrations in terms of speed and orientation of the snails at different moments of the tidal cycle. The application of the LED technique to other molluscs and nocturnal animals is discussed. Nocturnal arena tests performed to complete the field observations confirmed the presence of interindividual and self‐trailing in N. textilis but not in the related sympatric species N. plicata. The behaviour of N. textilis is compared to that of other intertidal molluscs.     

Omemeea maxbassiensis n. gen., n. sp. (Nematoda: Aphelenchoididae) from Galleries of the Bark Beetle Lepersinus californicus Sw. (Coleoptera: Scolytidae) in North Dakota

Omemeea maxbassiensis n. gen., n. sp. was found inhabiting galleries of a bark beetle, Lepersinus californicus Sw., in green ash, Fraxinus pennsylvanica Marsh. The genus differs from all other genera in the subfamily in its uniquely shaped umbrella-like head, distinctive stylet, and location of excretory pore.     

Richness,systematics, and distribution of molluscs associated with the macroalga Gigartina skottsbergii in the Strait of Magellan,Chile: A biogeographic affinity study

Knowledge about the marine malacofauna in the Magellan Region has been gained from many scientific expeditions that were carried out during the 19th century. However, despite the information that exists about molluscs in the Magellan Region, there is a lack of studies about assemblages of molluscs co-occurring with macroalgae, especially commercially exploitable algae such as Gigartina skottsbergii, a species that currently represents the largest portion of carrageenans within the Chilean industry. The objective of this study is to inform about the richness, systematics, and distribution of the species of molluscs associated with natural beds in the Strait of Magellan. A total of 120 samples from quadrates of 0.25 m² were obtained by SCUBA diving at two sites within the Strait of Magellan. Sampling occurred seasonally between autumn 2010 and summer 2011: 15 quadrates were collected at each site and season. A total of 852 individuals, corresponding to 42 species of molluscs belonging to Polyplacophora (9 species), Gastropoda (24), and Bivalvia (9), were identified. The species richness recorded represents a value above the average richness of those reported in studies carried out in the last 40 years in sublittoral bottoms of the Strait of Magellan. The biogeographic affinity indicates that the majority of those species (38%) present an endemic Magellanic distribution, while the rest have a wide distribution in the Magellanic-Pacific, Magellanic-Atlantic, and Magellanic-Southern Ocean. The molluscs from the Magellan Region serve as study models for biogeographic relationships that can explain long-reaching patterns and are meaningful in evaluating possible ecosystemic changes generated by natural causes or related to human activities.     

Phenotypes of Phosphoglucose isomerase,phosphoglucose mutase and general protein in some freshwater molluscs from Basrah,Iraq

Electrophoretic variants of phosphoglucose isomerase (EC.5.3.1.9) and phosphoglucose mutase (EC.2.7.5.1) have been studied in eight species of freshwater molluscs. Two phenotypes of phosphoglucose isomerase were observed in Melanopsis nodosa and one phenotype was observed in the rest of the species. One phenotype of phosphoglucose mutase was observed in all the species of molluscs studied. Phosphoglucose isomerase is inferred to be a dimer encoded at a single polymorphic locus in Melanoides nodosa. There are two alleles at this locus. Phosphoglucose mutase is inferred to be a monomer encoded at a single monomorphic locus in all species. The electrophoretic analysis revealed that phosphoglucose isomerase enzyme cannot be considered a good taxonomic criterion to differentiate the different members of the six families studied but, on the other hand, it is considered a good taxonomic criterion to differentiate Melanopsis nodosa and Theodoxus jordani. Phosphoglucose mutase is considered a good taxonomic criterion to differentiate the family Melanidae from the remaining five families studied. General protein can be considered a good taxonomic criterion to differentiate the family Corbicullidae from Melanidae, Viviparidae and Neritidae but, on the other hand, it seems to be a less useful taxonomic criterion to differentiate between the Viviparidae and Neritidae.     

A new species of Ceylonitermellus Emerson, 1960 (Blattodea: Termitidae: Nasutitermitinae) from India with a key to the genus

Ceylonitermellus Emerson is a rarely collected soil inhabiting nasute termite endemic to Oriental region with three known species. A fourth species, Ceylonitermellus sahyadriensis sp. nov. is described and illustrated based on morphological characters of soldier and gut morphology of workers. Both the castes have poorly sclerotized body and paler in colour. This is the second species from India and fourth species of the genus from world. The species can be distinguished from the closely related C. periyarensis by the pyriform and shorter head capsule and with other two species of the genus by its larger head capsule as compared to C. kotuae and smaller head capsule as compared to C. hantanae. The new species was collected from tropical evergreen forest from a small colony near the base of a tree.LSID: urn:lsid:zoobank.org:pub:34616357-2CC9-46B2-8B8D-3CFD984CED89.     

Nitroxidergic elements in the digestive system of Mactra chinensis and Spisula sachalinensis (Mollusca: Bivalvia: Mactridae)

Localization and morphology of NO-ergic elements in the digestive system of bivalve molluscs Mactra chinensis and Spisula sachalinensis were studied using histochemical technique [1] for detection of NADPH-diaphorase (EC 1.6.99.1) [1]. The NO-producing elements were revealed in all parts of the digestive system of the studied animals. NADPH-diaphorase was found in cells of several morphological types as well as in nerve plexuses. The most abundant in the digestive tract parts of the studied molluscs were intraepithelial nerve cells of the “open” type, whose thin apical process is directed towards the gut lumen. Subepithelial NO-ergic neurons were revealed in stomach and crystalline style sac of Mactra chinensis. Besides, diformazan granules are present in brush-border epitheliocytes of the major and secondary ducts of the digestive gland as well as in cells of digestive tubules of this gland. All studied parts were found to contain basiepithelial and subepithelial NO-ergic nerve fibers forming networks of various densities from, most commonly, loose to dense plexuses particularly developed in labia, esophagus, and gut of the studied molluscs.     

Trace metals in Caprella (Crustacea: Amphipoda). A new tool for monitoring pollution in coastal areas?

The main objective of the present study was to evaluate the concentration of trace metals in eight species of Caprella from sites of different degree of pollution along Southern Spain, and compare them with nine additional species of peracaridean crustaceans (5 gammarids, 3 isopods and 1 tanaid) and three molluscs. This is the first comprehensive study of trace metals in caprellids and other peracaridean crustaceans as a baseline work for future research. For most of the metals, values are higher in caprellids than in the rest of peracarideans and molluscs, as Mytilus or Patella, traditionally used as biomonitor in previous studies. Caprellids showed a significant higher range for Cr, Hg and Zn, while molluscs were better biomonitors for Pb; non-caprellid peracarids showed lower range of Fe and Ni than caprellids and molluscs. Besides the wider ranges shown by caprellids for trace metals in comparison with other invertebrates, Caprella spp. is especially abundant in intertidal and shallow waters ecosystems worldwide; this genus includes species characterised by a short generation time, and a sedentary way of life as a consequence of direct development and low capacity of swimming. Consequently, the use of Caprella spp. could be an interesting tool in monitoring programmes of heavy metal pollution.     

Molecular Identification of Haemadipsa rjukjuana (Hirudiniformes: Haemadipsidae) in Gageo Island,Korea

There are 60 species of blood-feeding land leeches, 50 species belonging to the family Haemadipsidae and 10 species belonging to the family Xerobdellidae. Despite recent papers on the land leeches, their taxonomic identification is not fully understood, especially at a species level. In Korea, there have been no historical records of the terrestrial leeches, but recently an unrecorded blood-feeding land leech was discovered at Gageo-do (Island), Korea. Molecular analysis was used to identify the species of 29 leeches collected from Mt. Dock-Sil in Gageo-do. Conventional PCR was conducted using nuclear 18S rRNA and mitochondrial cytochrome c oxidase subunit 1 (CO1) genetic marker. The 18S rRNA sequences revealed that the leeches share 99.9% identity with Haemadipsa rjukjuana (inhabiting Taiwan), and the CO1 sequences revealed that the leeches are very close to H. rjukjuana (inhabiting Taiwan). The CO1 sequences were separated into 2 categories, 1 with 94.6% and the other with 94.3% similarity to the H. rjukjuana L00115A (inhabiting Taiwan). This new finding of the land leech is the first record in Korea. In addition, the north range of the distribution of the blood-feeding leech (Hirudiniformes: Haemadipisidae) should be reconsidered including Korea.     

Effects of thyroid hormone level alterations on the Weberian apparatus ontogeny of cyprinids (Cyprinidae; Teleostei)

Effects of thyroid hormone (TH) level alterations on the development and definitive morphology of the Weberian apparatus (WA, morphofunctional complex, providing transmission of sound signals from the gas bladder to the labyrinth of inner ear) were experimentally assessed in cyprinid fishes (Labeobarbus intermedius and Danio rerio). Alterations of TH-level were shown to lead to heterochronies, changes of timing and rates of ontogenetic events resulting in changes of definitive morphology of some structures as well as of the WA as a whole. Differences in reaction of WA structures to the TH-level alterations, and inter- and intraspecific variability of TH-responsiveness were revealed.     

Three-dimensional head angular velocity detection from otolith afferent signals

Afferent signals from the otolith organs can produce compensatory eye position and velocity signals which has been described as linear vestibulo-ocular reflex (LVOR). The afferent otolith signals carry information about head orientation and changes of head orientation relative to gravity. A head orientation (tilt) related position signal can be obtained from population vector coding of tonic otolith afferent signals during static or dynamic head tilts, which in turn could produce compensatory eye position signals in the LVOR. On the other hand, eye angular velocity signals may be extracted, as proposed in this study, from the population response of tilt-velocity sensitive otolith afferents. Such afferents are shown to encode instantaneous head orientation relative to gravity at onset of a head movement and, as the movement continues, the projection of head angular velocity onto the earth-horizontal plane, indicating the instantaneous direction of movement relative to gravity. Angular velocity components along the earth-vertical direction which are not directly encoded by otolith afferents can be detected by central signal processing. Central reconstruction of 3D head angular velocity allows to obtain information about absolute head orientation in space even in the absence of semicircular canal related information. Such information is important for generating compensatory eye movements as well as for dynamic control of posture.     

Ostracoda and Mollusca biodiversity and hydrochemical features in Late Miocene brackish basins of Italy

Late Miocene brackish ostracods and molluscs collected in three Italian basins show noticeable differences in their taxonomic composition, despite their capability of dispersing across wide geographic areas. In the Venetian-Friulian Basin (northern Italy), the upper Tortonian sediments contain oligotypic ostracod assemblages including Hemicyprideis dacica dacica, Hemicytheria pejinovicensis, and Loxoconcha cf. L. josephi and few gastropods referable to Planorbidae and Stenothyroides, which are typical of the central Paratethys. In central Italy, the brackish ostracods and molluscs recovered from upper Tortonian-lower Messinian deposits from four Tuscan basins (Volterra-Radicondoli, Velona, Baccinello-Cinigiano, and Valdelsa) display high affinity at a generic level but strong endemicity at a specific level. At Cessaniti (southern Italy), the upper Tortonian unit contains oligotypic brackish ostracods and molluscs: Mediocytherideis (Sylvestra) posterobursa, Cyprideis ruggierii, Loxoconcha cf. L. biformata, and Zonocypris membranae quadricella characterise the ostracod fauna, while Granulolabium bicinctum and Hydrobia frauenfeldi are the dominant molluscs. The recovered ostracods have a strong affinity with brackish species from central and eastern Palaeo-Mediterranean areas, whereas the molluscs present a Paratethyan origin. Despite the fact that the basins are all brackish and partly coeval, the systematics of these assemblages highlights the absence of common species among the three studied areas. Geochemical analyses (stable isotopes and trace elements) are performed on ostracods, and ⁸⁷Sr/⁸⁶Sr ratios are established in molluscs and echinoids. The results suggest brackish environments with different compositions and origins of solutes in the three different areas. The Tuscan basins are characterised by brackish waters, with NaCl-enriched waters coming from aquifers of Triassic evaporite bedrock. The brackish deposits of the Venetian-Friulian Basin and Cessaniti are true marginal marine environments, although the northern basin may have been influenced by both the Paratethyan Sava Basin and the northern portion of the Palaeo-Mediterranean water bodies.     

Factors influencing codling moth larval response to α-farnesene

Behavioral responses of newly-emerged codling moth (Cydia pomonella L.) larvae to α-farnesene were compared for a laboratory-reared strain (‘lab’, 160 generations inbred) and a recently collected strain (‘wild’, 3 generations). Video recordings of single larvae placed 20 mm from Bond papers releasing a range of seven α-farnesene concentrations were scored for head turning, head lifting, head direction, and movement across a Petri dish. The laboratory strain was significantly less successful at finding the treated papers than the wild strain. The lab strain was also significantly less active, shown by more random orientation, slower walking speed, less head turning and less head lifting. Both strains showed lower response to α-farnesene concentrations less than 10⁻⁶ (w/v) α-farnesene. Orientation, walking speed, and head turning rate were significantly higher in the presence of α-farnesene concentrations >10⁻⁷ w/v, for both strains. Head lifting did not show any effect from α-farnesene. Head turning was associated with both head lifting and walking speed and this association improved with the presence of α-farnesene. Increased attraction to odour source was correlated with improved direction finding at concentrations above 10⁻⁷ w/v. Activity factors such as head turning and walking speed influenced time to locate odour source more than orientation factors. Odour-guided orientation to α-farnesene in codling moth larvae was composed of both locomotory, and to a lesser extent, orientation responses, which increased in a directed fashion to the stimulus.     

The Bony Labyrinth in Diprotodontian Marsupial Mammals: Diversity in Extant and Extinct Forms and Relationships with Size and Phylogeny

The shape of the bony labyrinth of the inner ear was quantified using geometric morphometrics in a sample of 16 species of living marsupial diprotodontians, the extinct Diprotodon and Thylacoleo, and four outgroups. X-ray micro-computed tomography (μCT) and conventional computed tomography (CT) were used to acquire 3D data. The analyses of 22 landmarks revealed a strong body-mass related allometric pattern. A discriminant analysis on allometry-free labyrinthine shape served to evaluate the phylogenetic signal portion of the labyrinth for Macropodiformes, Phalangeroidea, Petauroidea, and Vombatiformes. The inner shape of Thylacoleo is consistent with its phylogenetic placement as a vombatiform.