DOCSLIB.ORG

Effects of Waterborne Cadmium Exposure on Its Internal Distribution in Meretrix Meretrix and Detoxification by Metallothionein and Antioxidant Enzymes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Effects of Waterborne Cadmium Exposure on Its Internal Distribution in Meretrix Meretrix and Detoxification by Metallothionein and Antioxidant Enzymes fmars-07-00502 July 7, 2020 Time: 19:35 # 1 ORIGINAL RESEARCH published: 09 July 2020 doi: 10.3389/fmars.2020.00502 Effects of Waterborne Cadmium Exposure on Its Internal Distribution in Meretrix meretrix and Detoxification by Metallothionein and Antioxidant Enzymes Yao Huang1†, Hongchao Tang1†, Jianyu Jin2, Meng bi Fan1, Alan K. Chang1 and Xueping Ying1* 1 College of Life and Environmental Sciences, Wenzhou University, Wenzhou, China, 2 College of Education, Wenzhou University, Wenzhou, China Edited by: Andrew Stanley Mount, Clemson University, United States Cadmium (Cd), one of the most toxic metals found in inshore sediments of China, is Reviewed by: a persistent environmental contaminant capable of exerting irreversible toxic effects Mirza Hasanuzzaman, on aquatic organisms and their associated ecosystems. Although Cd is known to Sher-e-Bangla Agricultural University, be toxic to marine animals, the underlying mechanism of this toxicity is not clear. Bangladesh Kamrun Nahar, In this study, Meretrix meretrix, a commercially and ecologically important species of Sher-e-Bangla Agricultural University, clam, was exposed to different concentrations of cadmium chloride (0, 1.5, 3, 6, and Bangladesh 12 mg L−1) for 5 days, and the levels of Cd accumulation, antioxidant enzyme activity, *Correspondence: Xueping Ying and expression of metallothionein (MT) in the hepatopancreas, gill, foot, and mantle [email protected]; were evaluated. The results revealed a sharp increase in Cd accumulation in the tissues [email protected]; in response to increased Cd2C concentrations in the water, and significant differences [email protected] in Cd accumulation were observed among the different tissues. Increased Cd2C level †These authors have contributed equally to this work in the tissues also led to a significant increase in malondialdehyde content, caused by increased lipid peroxidation. The activities of superoxide dismutase and catalase Specialty section: 2C This article was submitted to also increased, peaking at different Cd concentrations, depending on the tissue. Marine Molecular Biology Glutathione peroxidase (GPx) activity in the gill and mantle initially increased but then and Ecology, decreased with increasing external Cd2C concentration. In the hepatopancreas and a section of the journal 2C Frontiers in Marine Science foot, GPx activity was inhibited by Cd , even at low concentrations. Furthermore, 2C Received: 06 March 2020 Cd also stimulated the expression of MT in all four tissues. However, the levels of Accepted: 03 June 2020 reduced glutathione (GSH) and oxidized glutathione (GSSG) in the gill and mantle, as Published: 09 July 2020 well as the GSH/GSSG ratios in all four tissues, decreased with increasing external Cd2C Citation: Huang Y, Tang H, Jin J, Fan M, concentrations. Taken together, the results suggested that in M. meretrix, response C Chang AK and Ying X (2020) Effects to the toxic effect of Cd2 might occur through a combination of mechanisms, of Waterborne Cadmium Exposure on which involve both enhanced antioxidant enzyme activities and the ability to bind and Its Internal Distribution in Meretrix 2C meretrix and Detoxification by sequester Cd via cysteine-rich molecules such as GSH and MT, both of which would Metallothionein and Antioxidant eventually lead to the reduction of heavy metal-induced oxidative stress. Enzymes. Front. Mar. Sci. 7:502. doi: 10.3389/fmars.2020.00502 Keywords: cadmium, Meretrix meretrix, oxidative damage, metallothionein, glutathione, antioxidant enzyme Frontiers in Marine Science | www.frontiersin.org 1 July 2020 | Volume 7 | Article 502 fmars-07-00502 July 7, 2020 Time: 19:35 # 2 Huang et al. Cadmium Exposure on Meretrix meretrix and Detoxification by Antioxidants HIGHLIGHTS where it is involved in the protection of cell membrane from −· lipid peroxidation by scavenging oxygen radicals (O2 ,H2O2, - Cd2C accumulation in different tissue of M. meretrix is and OH). This function plays a key role in the complexation concentration dependent. and detoxification of heavy metal ions (Lavradas et al., 2014; - Cd2C induces a significant increase in MDA level in Bouzahouane et al., 2018; Chan and Wang, 2018). Glutathione different M. meretrix tissues. can exist in a thiol-reduced state (GSH) or in an oxidized state - MT response significantly correlates with Cd2C (GSSG), which consists of two GSH molecules that are linked bioaccumulation. together by a disulfide bond (Fraternale et al., 2017). The content - CAT and SOD activities vary according to external of GSH and GSH/GSSG ratio can act as an important indicator of Cd2C concentrations. the body’s antioxidant capacity (Nair et al., 2015). In the cytosol, −· - Antioxidant enzymes, GSH and MT, might act hydroxyl (·OH) and superoxide (O2 ) radicals are preferably cooperatively against oxidative stress. scavenged by metallothioneins (MTs), which are low-molecular- weight (6–7 kDa) cysteine-rich metal-binding proteins involved in multiple physiological activities, such as metal homeostasis and INTRODUCTION detoxification (Amiard et al., 2006; Min et al., 2016). Moreover, MT can protect cells from metal toxicity not only by acting as Toxic metal pollution, which can seriously threaten the biological an oxyradical scavenger but also through metal-binding/release sustainability of coastal ecosystems, has now become a major dynamics (Gu et al., 2019; Ohta et al., 2019). Metallothioneins can problem for the aquatic environment (Liu et al., 2018). Among participate directly in antioxidative defenses, and the synthesis the toxic metals, cadmium (Cd) is considered to be one of the of MT mRNA is correlated with the extent of metal stress (Zhu most dangerous, and it is usually found in marine environments et al., 2018; Chen et al., 2019; Gu et al., 2019). In addition, MT (Liu et al., 2015; Gu et al., 2019). In normal water, the level can be excreted from the cells and absorbed by the cells via of dissolved Cd generally ranges from 10 to 500 ng L−1, but a receptor-mediated mechanism, in which MT remains in an levels that exceed 10 mg L−1 have also been recorded in some endocytotic compartment while the metal is transported to the industrialized areas in China (Hu et al., 2011; Meng et al., 2013; cytosol (Amiard et al., 2006; Ohta et al., 2019). Chan and Wang, 2018). Cadmium has a long half-life and can Meretrix meretrix is a clam that is widely found along the be bioaccumulated in organisms through the food chain. The coastal areas of China, and it is an economically and ecologically accumulation of Cd within living aquatic animals would exert a important bivalve mollusk. It has low-metabolism and high filter- wide range of toxicological effects on the various tissues of the feeding activity, and it lives mainly in sandy or muddy substrates animals and their human consumers (Liu et al., 2015; García- in estuarine lower intertidal and shallow subtidal areas, and Navarro et al., 2017). Cadmium can induce the body to produce therefore it is vulnerable to environmental pollutants (Zhang a large number of reactive oxygen species (ROS) (Sandbichler et al., 2011; Xia et al., 2016). M. meretrix is known to have a and Höckner, 2016; Jing et al., 2019). The ROS in turn can cause strong capacity to accumulate metals (Zhang et al., 2011; Wang oxidative damage, which is often linked to lipid peroxidation, et al., 2013) and is therefore widely used as a biological tool protein denaturation, and inactivation of enzymes as well as for monitoring toxic metal pollution in the marine environment DNA replication errors (Chandurvelan et al., 2015; Xia et al., (Hamad et al., 2011; Meng et al., 2013; Liu et al., 2018). While 2016; Lin et al., 2017). Malondialdehyde (MDA), a final product research has focused on the effect of Cd2C toxicity on mollusks, of the decomposition of lipid peroxidation, has recently been there is a lack of data with regard to the effect of Cd2C exposure considered as a sensitive biomarker of oxidative damage. It can on MT and other antioxidants in the different tissues of the be used to determine the extent of lipid peroxidation and the clam. Our objectives were to determine the toxicological and accumulation of ROS in an organism (Liu and Wang, 2016; Lin biochemical responses of M. meretrix to acute Cd exposure and et al., 2017; Haque et al., 2018). to investigate the bioaccumulation of Cd in different tissues as a In general, aquatic organisms have independently evolved function of exposure concentration. This could allow us to better an antioxidant defense mechanism to protect biomolecules understand how the antioxidant defense system of these bivalves from oxidative stress caused by ROS, in which both enzymatic might respond to Cd2C stress. Furthermore, the relationships antioxidants and non-enzymatic antioxidants are functionally between Cd accumulation in the tissues and MT as well as involved (Lavradas et al., 2014; Xia et al., 2016; Cui et al., the antioxidants examined were also investigated. Our findings 2020). A clear understanding of the link between antioxidants’ highlight the potential application of Cd toxicity-associated defense systems and metal bioconcentrations may help to identify biomarkers in clam in the future selection of biomarkers and markers that can reflect the status of aquatic ecosystems (Haque bioindicator species for aquatic environmental monitoring. et al., 2018). Superoxide dismutase (SOD) is considered to be −· the first line of defense against oxidative stress, since O2 is converted to O2 and H2O2, and H2O2 is subsequently converted MATERIALS AND METHODS to O2 and H2O by catalase (CAT) present in the peroxisomes or by glutathione peroxidase (GPx) present in the mitochondria Animals and Treatments and cytosol (Chen et al., 2019; Gu et al., 2019). Glutathione is an Meretrix meretrix clams (shell length, 64.36 ± 2.85 mm; shell important sulfhydryl non-protein compound found in the tissue, width, 31.69 ± 1.42 mm; shell height, 53.57 ± 2.45 mm; Frontiers in Marine Science | www.frontiersin.org 2 July 2020 | Volume 7 | Article 502 fmars-07-00502 July 7, 2020 Time: 19:35 # 3 Huang et al.
Load more

Recommended publications
  • Clam Dissection Guideline
    Clam Dissection Guideline BACKGROUND: Clams are bivalves, meaning that they have shells consisting of two halves, or valves. The valves are joined at the top, and the adductor muscles on each side hold the shell closed. If the adductor muscles are relaxed, the shell is pulled open by ligaments located on each side of the umbo. The clam's foot is used to dig down into the sand, and a pair of long incurrent and excurrent siphons that extrude from the clam's mantle out the side of the shell reach up to the water above (only the exit points for the siphons are shown). Clams are filter feeders. Water and food particles are drawn in through one siphon to the gills where tiny, hair-like cilia move the water, and the food is caught in mucus on the gills. From there, the food-mucus mixture is transported along a groove to the palps (mouth flaps) which push it into the clam's mouth. The second siphon carries away the water. The gills also draw oxygen from the water flow. The mantle, a thin membrane surrounding the body of the clam, secretes the shell. The oldest part of the clam shell is the umbo, and it is from the hinge area that the clam extends as it grows. I. Purpose: The purpose of this lab is to identify the internal and external structures of a mollusk by dissecting a clam. II. Materials: 2 pairs of safety goggles 1 paper towel 2 pairs of gloves 1 pair of scissors 1 preserved clam 2 pairs of forceps 1 dissecting tray 2 probes III.
    [Show full text]
  • CHAPTER 10 MOLLUSCS 10.1 a Significant Space A
    PART file:///C:/DOCUME~1/ROBERT~1/Desktop/Z1010F~1/FINALS~1.HTM CHAPTER 10 MOLLUSCS 10.1 A Significant Space A. Evolved a fluid-filled space within the mesoderm, the coelom B. Efficient hydrostatic skeleton; room for networks of blood vessels, the alimentary canal, and associated organs. 10.2 Characteristics A. Phylum Mollusca 1. Contains nearly 75,000 living species and 35,000 fossil species. 2. They have a soft body. 3. They include chitons, tooth shells, snails, slugs, nudibranchs, sea butterflies, clams, mussels, oysters, squids, octopuses and nautiluses (Figure 10.1A-E). 4. Some may weigh 450 kg and some grow to 18 m long, but 80% are under 5 centimeters in size. 5. Shell collecting is a popular pastime. 6. Classes: Gastropoda (snails…), Bivalvia (clams, oysters…), Polyplacophora (chitons), Cephalopoda (squids, nautiluses, octopuses), Monoplacophora, Scaphopoda, Caudofoveata, and Solenogastres. B. Ecological Relationships 1. Molluscs are found from the tropics to the polar seas. 2. Most live in the sea as bottom feeders, burrowers, borers, grazers, carnivores, predators and filter feeders. 1. Fossil evidence indicates molluscs evolved in the sea; most have remained marine. 2. Some bivalves and gastropods moved to brackish and fresh water. 3. Only snails (gastropods) have successfully invaded the land; they are limited to moist, sheltered habitats with calcium in the soil. C. Economic Importance 1. Culturing of pearls and pearl buttons is an important industry. 2. Burrowing shipworms destroy wooden ships and wharves. 3. Snails and slugs are garden pests; some snails are intermediate hosts for parasites. D. Position in Animal Kingdom (see Inset, page 172) E.
    [Show full text]
  • Annelids, Arthropods, Molluscs 2. Very Diverse, Mostly Marine B. Characteristics 1
    Molluscs A. Introduction 1. Three big Protostome Phyla - Annelids, Arthropods, Molluscs 2. Very diverse, mostly marine B. Characteristics 1. Bilateral symmetrical, unsegmented with definite head 2. Muscular foot 3. Mantle - mantle cavity a. Secretes shell - Calcium carbonate 4. Ciliated epithelium 5. Coelom reduced - around heart 6. Open circulatory system 7. Gaseous exchange by gills, lung, or just body surface 8. Metanephridia - empty into mantle cavity C. Body Plan 1. Generalized mollusc a. Mantle - secreted shell b. Mantle - cavity has gills - posterior - location important 2. Head-foot a. Head - 1. Radula - rasping tongue a. Mostly for scraping - snails b. Some (Cone shells) modified to a dart and poison b. Foot - Variously modified 1. Ventral sole-like structure - movement 2. May be shaped for burrowing 3. Shell 1. Made of Calcium Carbonate Molluscs 2. Three layers a. Periostracum - organic layer - not always visible b. Prismatic layer - prim-shaped crystals of calcium carbonate 1. Secreted by gladular margin of mantle 2. Grows as animal grows c. Nacreous layer 1. Continuously secreted by mantle on interior of shell 2. Pearls 4. Reproduction a. Larval stages 1. Trochophore - first stage to hatch from egg 2. Veliger - planktonic larva of most marine snails and bivalves a. Beginnings of foot, shell and mantle D. Classes - problem of segmentation - is it the original body plan - have molluscs lost segementation? 1. Monoplacophora - genus Neopilina a. Serial repetition in body form b. Single shell c. Interesting story of discovery 2. Polyplacophora - chitons a. Segmented shell - plates b. Multiple gills down side of body - not like generalized plan c. Rock dwellers that use radula to scrape algae off rocks 3.
    [Show full text]
  • Mollusca, Archaeogastropoda) from the Northeastern Pacific
    Zoologica Scripta, Vol. 25, No. 1, pp. 35-49, 1996 Pergamon Elsevier Science Ltd © 1996 The Norwegian Academy of Science and Letters Printed in Great Britain. All rights reserved 0300-3256(95)00015-1 0300-3256/96 $ 15.00 + 0.00 Anatomy and systematics of bathyphytophilid limpets (Mollusca, Archaeogastropoda) from the northeastern Pacific GERHARD HASZPRUNAR and JAMES H. McLEAN Accepted 28 September 1995 Haszprunar, G. & McLean, J. H. 1995. Anatomy and systematics of bathyphytophilid limpets (Mollusca, Archaeogastropoda) from the northeastern Pacific.—Zool. Scr. 25: 35^9. Bathyphytophilus diegensis sp. n. is described on basis of shell and radula characters. The radula of another species of Bathyphytophilus is illustrated, but the species is not described since the shell is unknown. Both species feed on detached blades of the surfgrass Phyllospadix carried by turbidity currents into continental slope depths in the San Diego Trough. The anatomy of B. diegensis was investigated by means of semithin serial sectioning and graphic reconstruction. The shell is limpet­ like; the protoconch resembles that of pseudococculinids and other lepetelloids. The radula is a distinctive, highly modified rhipidoglossate type with close similarities to the lepetellid radula. The anatomy falls well into the lepetelloid bauplan and is in general similar to that of Pseudococculini- dae and Pyropeltidae. Apomorphic features are the presence of gill-leaflets at both sides of the pallial roof (shared with certain pseudococculinids), the lack of jaws, and in particular many enigmatic pouches (bacterial chambers?) which open into the posterior oesophagus. Autapomor- phic characters of shell, radula and anatomy confirm the placement of Bathyphytophilus (with Aenigmabonus) in a distinct family, Bathyphytophilidae Moskalev, 1978.
    [Show full text]
  • Structure and Function of the Digestive System in Molluscs
    Cell and Tissue Research (2019) 377:475–503 https://doi.org/10.1007/s00441-019-03085-9 REVIEW Structure and function of the digestive system in molluscs Alexandre Lobo-da-Cunha1,2 Received: 21 February 2019 /Accepted: 26 July 2019 /Published online: 2 September 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The phylum Mollusca is one of the largest and more diversified among metazoan phyla, comprising many thousand species living in ocean, freshwater and terrestrial ecosystems. Mollusc-feeding biology is highly diverse, including omnivorous grazers, herbivores, carnivorous scavengers and predators, and even some parasitic species. Consequently, their digestive system presents many adaptive variations. The digestive tract starting in the mouth consists of the buccal cavity, oesophagus, stomach and intestine ending in the anus. Several types of glands are associated, namely, oral and salivary glands, oesophageal glands, digestive gland and, in some cases, anal glands. The digestive gland is the largest and more important for digestion and nutrient absorption. The digestive system of each of the eight extant molluscan classes is reviewed, highlighting the most recent data available on histological, ultrastructural and functional aspects of tissues and cells involved in nutrient absorption, intracellular and extracellular digestion, with emphasis on glandular tissues. Keywords Digestive tract . Digestive gland . Salivary glands . Mollusca . Ultrastructure Introduction and visceral mass. The visceral mass is dorsally covered by the mantle tissues that frequently extend outwards to create a The phylum Mollusca is considered the second largest among flap around the body forming a space in between known as metazoans, surpassed only by the arthropods in a number of pallial or mantle cavity.
    [Show full text]
  • Lab 5: Phylum Mollusca
    Biology 18 Spring, 2008 Lab 5: Phylum Mollusca Objectives: Understand the taxonomic relationships and major features of mollusks Learn the external and internal anatomy of the clam and squid Understand the major advantages and limitations of the exoskeletons of mollusks in relation to the hydrostatic skeletons of worms and the endoskeletons of vertebrates, which you will examine later in the semester Textbook Reading: pp. 700-702, 1016, 1020 & 1021 (Figure 47.22), 943-944, 978-979, 1046 Introduction The phylum Mollusca consists of over 100,000 marine, freshwater, and terrestrial species. Most are familiar to you as food sources: oysters, clams, scallops, and yes, snails, squid and octopods. Some also serve as intermediate hosts for parasitic trematodes, and others (e.g., snails) can be major agricultural pests. Mollusks have many features in common with annelids and arthropods, such as bilateral symmetry, triploblasty, ventral nerve cords, and a coelom. Unlike annelids, mollusks (with one major exception) do not possess a closed circulatory system, but rather have an open circulatory system consisting of a heart and a few vessels that pump blood into coelomic cavities and sinuses (collectively termed the hemocoel). Other distinguishing features of mollusks are: z A large, muscular foot variously modified for locomotion, digging, attachment, and prey capture. z A mantle, a highly modified epidermis that covers and protects the soft body. In most species, the mantle also secretes a shell of calcium carbonate. z A visceral mass housing the internal organs. z A mantle cavity, the space between the mantle and viscera. Gills, when present, are suspended within this cavity.
    [Show full text]
  • 128 Freiberg, 2012 Protoconch Characters of Late Cretaceous
    Freiberger Forschungshefte, C 542 psf (20) 93 – 128 Freiberg, 2012 Protoconch characters of Late Cretaceous Latrogastropoda (Neogastropoda and Neomesogastropoda) as an aid in the reconstruction of the phylogeny of the Neogastropoda by Klaus Bandel, Hamburg & David T. Dockery III, Jackson with 5 plates BANDEL, K. & DOCKERY, D.T. III (2012): Protoconch characters of Late Cretaceous Latrogastropoda (Neogastropoda and Neomesogastropoda) as an aid in the reconstruction of the phylogeny of the Neogastropoda. Paläontologie, Stratigraphie, Fazies (20), Freiberger Forschungshefte, C 542: 93–128; Freiberg. Keywords: Latrogastropoda, Neogastropoda, Neomesogastropoda, Cretaceous. Addresses: Prof. Dr. Klaus Bandel, Universitat Hamburg, Geologisch Paläontologisches Institut und Museum, Bundesstrasse 55, D-20146 Hamburg, email: [email protected]; David T. Dockery III, Mississippi Department of Environmental Quality, Office of Geology, P.O. Box 20307, 39289-1307 Jackson, MS, 39289- 1307, U.S.A., email: [email protected]. Contents: Abstract Zusammenfassung 1 Introduction 2 Palaeontology 3 Discussion 3.1 Characters of protoconch morphology among Muricoidea 3.2 Characteristics of the protoconch of Buccinidae, Nassariidae, Columbellinidae and Mitridae 3.3 Characteristics of the protoconch morphology among Toxoglossa References Abstract Late Cretaceous Naticidae, Cypraeidae and Calyptraeidae can be recognized by the shape of their teleoconch, as well as by their characteristic protoconch morphology. The stem group from which the Latrogastropoda originated lived during or shortly before Aptian/Albian time (100–125 Ma). Several groups of Latrogastropoda that lived at the time of deposition of the Campanian to Maastrichtian (65–83 Ma) Ripley Formation have no recognized living counterparts. These Late Cretaceous species include the Sarganoidea, with the families Sarganidae, Weeksiidae and Moreidae, which have a rounded and low protoconch with a large embryonic whorl.
    [Show full text]
  • Adaptive Radiation in Molluscs
    Adaptive Radiation in Molluscs Class: Monoplacophora shell: forms a single dorsal conical shell head: reduced mantle: covers undersurface of shell gills: 5 or 6 pairs foot: broad flat ventral, for creeping radula: present larva: Classes: Caudofoveata & Solanogastres (formerly Cl. Aplacophora) shell: none, but with calcareous scales and spicules in mantle head: reduced mantle: encloses animal gills: absent, or present in cloaca foot: reduced to small ridge within ventral groove radula: present in some, for piercing larva: trochophore Class: Polyplacophora (Chitons) shell: modified into eight overlappingdorsal plates head: present mantle: greatly enlarged, modified into "girdle" around base of shells gills: present foot: broad flat ventral, for gliding movement radula: present larva: trochophore Class: Scaphapoda (Tusk Shells or Tooth Shells) shell: anteroposteriorly elongated into tapering tusk-like tube open at both ends head: reduced to short proboscis mantle: lines inside of shell, used for respiration instead of gills gills: none; oxygen diffuses across mantle foot: conical, elongated ventrally and used for burrowing radula: present larva: trochophore & veliger Class: Bivalvia (Clams) shell: two lateral, usually symmetrical, hinged valves head: absent mantle: lines inside of both shells; forms siphons for water flow gills: most with pair of large gills; also used for feeding and as marsupium foot: ventral, wedge-shaped, very muscular, used for burrowing radula: absent larva: marine forms with trochophore & veliger; fw - glochidia Class:
    [Show full text]
  • Periostracal Mineralization in the Gastrochaenid Bivalve Spengleria Antonio G
    Acta Zoologica (Stockholm) doi: 10.1111/azo.12019 Periostracal mineralization in the gastrochaenid bivalve Spengleria Antonio G. Checa1 and Elizabeth M. Harper2 Abstract 1Departamento de Estratigrafıa y Paleonto- Checa, A.G. and Harper, E.M. 2012. Periostracal mineralization in the logıa, Universidad de Granada, Avenida gastrochaenid bivalve Spengleria.—Acta Zoologica (Stockholm) 00: 000–000. Fuentenueva s/n, Granada, 18071, Spain; 2Department of Earth Sciences, University We investigated the spikes on the outer shell surface of the endolithic gastrochae- of Cambridge, Downing Street, Cam- nid bivalve genus Spengleria with a view to understand the mechanism by which bridge, CB2 3EQ, UK they form and evaluate their homology with spikes in other heterodont and pal- aeoheterodont bivalves. We discovered that spike formation varied in mecha- Keywords: nism between different parts of the valve. In the posterior region, spikes form biomineralization, molluscs, aragonite, peri- within the translucent layer of the periostracum but separated from the calcare- ostracum ous part of the shell. By contrast those spikes in the anterior and ventral region, despite also forming within the translucent periostracal layer, become incorpo- Accepted for publication: 20 November 2012 rated into the outer shell layer. Spikes in the posterior area of Spengleria mytiloides form only on the outer surface of the periostracum and are therefore, not encased in periostracal material. Despite differences in construction between these gastrochaenid spikes and those of other heterodont and palaeoheterodont bivalves, all involve calcification of the inner translucent periostracal layer which may indicate a deeper homology. Antonio G. Checa, Departamento de Estratigrafıa y Paleontologıa, Universidad de Granada, Avenida Fuentenueva s/n, 18071, Granada, Spain.
    [Show full text]
  • RESPIRATORY ORGANS of MOLLUSCA Dr
    RESPIRATORY ORGANS OF MOLLUSCA Dr. Sunita Kumari Sharma Associate Professor and Head P.G. Department of Zoology Maharaja College, Ara Molluscs are familiar to man from prehistoric times as the food and for ornamental shell. Molluscs are the unsegmented animals with the soft body and covered with the hard calcareous shell as the exoskeleton. They are mostly aquatic and possess radula and Organ of Bojanus. This shell is secreted by a thin sheet of tissue called as a mantle, which encloses the internal organs. They are distributed in all possible environments and exhibit many adaptive features. As a consequence of living in the diverse environmental conditions, their respiratory organs are modified accordingly as described below: A. Skin and Mantle Specialised respiratory structures are lacking in some Scaphopoda. Respiration is carried by the internal surface of the mantle, particularly the antero-ventral side in Dentalium, Antalis. In nudibranchs (Gastropoda) the entire dorsum of the body acts as the site of gas exchange. Integumentary gas exchange occurs in parasitic Entoconcha, Conia, Limpontia sp. etc. The outer covering of the body (skin) and mantle usually act as accessory respiratory organs. In most of the members of Aeolididae the dorsal surface of the body is provided with papillae. The papillae are variable in size and communicate with the heart by veins. The respiration is known as pallial respiration. Most of the Nudibranchia, Entoconcha, Unio etc. respire through skin. In some forms (e.g., Neomenia, Chaetoderma, Aplysia, Dentalium, etc.), the mantle is used for respiration. B. Ctenidium Aquatic molluscs respire through ctenidia. These are the comb-like outgrowths of the mantle and are located within the mantle cavity.
    [Show full text]
  • Pinnocaris and the Origin of Scaphopods
    Pinnocaris and the origin of scaphopods JOHN S. PEEL Peel, J.S. 2004. Pinnocaris and the origin of scaphopods. Acta Palaeontologica Polonica 49 (4): 543–550. The description of a tiny coiled protoconch in the Ordovician Pinnocaris lapworthi Etheridge, 1878 indicates that this ribeirioid rostroconch mollusc cannot be the ancestor of scaphopods, resolving recent debate concerning the role of Pinnocaris in scaphopod evolution. The sense of coiling of the scaphopod protoconch is opposite to that of Pinnocaris. Scaphopod protoconchs resemble helcionelloid molluscs (Cambrian–Early Ordovician) in terms of their direction of coiling, although the scaphopod shell is strongly modified by the extreme anterior component of growth. Convergence is identified between scaphopods and two helcionelloid lineages (Eotebenna and Yochelcionella) from the Early–Middle Cambrian. The large stratigraphical gap between helcionelloids and the first undoubted scaphopods (Devonian or Car− boniferous) supports the notion that the scaphopods were derived from conocardioid rostroconchs rather than directly from helcionelloids. However, the protoconch of conocardioid rostroconchs closely resembles the helcionelloid shell, suggesting that conocardioids in turn were probably derived from helcionelloids. Key words: Mollusca, Rostroconchia, Scaphopoda, Helcionelloida, Pinnocaris, Ordovician. John S. Peel [[email protected]], Department of Earth Sciences (Palaeobiology) and Museum of Evolution, Uppsala University, Norbyvägen 22, SE−751 36, Uppsala, Sweden. Introduction dorsal
    [Show full text]
  • Final Report, the Xerces Society, Blue Mountains Terrestrial Mollusks Surveys
    1 Final Report to the Interagency Special Status / Sensitive Species Program (ISSSSP) from The Xerces Society for Invertebrate Conservation SPRING 2012 BLUE MOUNTAINS TERRESTRIAL MOLLUSK SURVEYS Assistance agreement L08AC13768, Modification 7 Robust lancetooth (Haplotrema vancouverense) from land adjacent to the North Fork Umatilla River, May 15, 2012. Photo by Alexa Carleton. Field work, background research, and report completed by Sarina Jepsen, Alexa Carleton, and Sarah Foltz Jordan, The Xerces Society for Invertebrate Conservation Species Identifications and Appendices III and IV completed by Tom Burke, Certified Wildlife Biologist September 28, 2012 2 Table of Contents Introduction…………………………………………………………………………………………………………………….. 3 Survey Protocol……………………………………………………………………………………………………………….. 3 Sites Surveyed and Survey Results…………………………………………………………………………………… 7 Potential Future Survey Work………………………………………………………………………………………….. 17 Acknowledgements…………………………………………………………………………………………………………. 17 References Cited……………………………………………………………………………………………………………… 17 Appendix I: Table of sites surveyed and species found…………………………………………………….. 19 Appendix II: Maps of sites surveyed and special status species found……………………………… 24 Appendix III: Discussion of taxa in families: Oreohelicidae and Polygyridae (by T. Burke)… 30 Appendix IV: Descriptions of mollusks collected (by Tom Burke)……………………………………… 47 3 Introduction Sarina Jepsen and Alexa Carleton (Xerces Society) conducted surveys for terrestrial mollusks in May of 2012 in the Blue Mountains on land managed by the Umatilla National Forest (Walla Walla and North Fork John Day Ranger Districts) and the Bureau of Land Management (Vale District). Tom Burke (Certified Wildlife Biologist) identified all specimens. The surveys targeted four special status snail species: Blue mountainsnail (Oreohelix strigosa delicata ‐ STR), Umatilla megomphix (Megomphix lutarius ‐ STR), Humped coin (Polygyrella polygyrella ‐ OR‐STR, WA‐ SEN), and Dryland forestsnail (Allogona ptychophora solida ‐ WA‐STR). Two of the four target species were found: O.
    [Show full text]