DOCSLIB.ORG

Arthropod Structure and Systematics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Arthropod Structure and Systematics chapter 2 Arthropod structure and systematics Niels P. Kristensen† and Jens Böcher Discussions about the composition and interrelationships lineages. The most anterior tagma bears the mouth open- of the principal arthropod taxa have been as vigorous in ing and a series of adjacent mouth appendages which the 21st century as ever in zoological history, but while because of their role in food uptake are more or less pro- these subjects are a significant scientific challenge in their foundly modified relative to the following locomotory own right, they are of little consequence for the purpose limbs. This anterior tagma similarly bears the visual of an identification manual. Suffice it here to note that organs, and in myriapods and hexapods moreover a pair while there has long been near-universal agreement that of antennae, on which numerous sensory organs (chemo- the Arachnida are a ‘natural group’, in as much as they are receptors in particular) are located. The opening of the considered to be monophyletic in the strict modern sense gut is morphologically located on the hind end of the ani- (i.e., the group comprises all known descendants of its mal, but can topographically appear shifted more or less members’ last common ancestor), the monophyly of the extensively forward. The location of the genital opening is Myriapoda has been continuously debated, and the also diagnostic of major arthropod lineages. monophyly of the Hexapoda has recently become so too. Small protuberances of the exoskeleton come in many A comprehensive account of arthropod structure, func- forms and may contribute significantly to the appearance tion and phylogeny is evidently outside the scope of the of more or less extensive body regions. Of special note are present work; reference must be made to a text of inverte- the ʻsensillaʼ, comprising, together with the visual organs, brate zoology such as Ruppert et al. (2004) or Brusca & the principal receptors of external stimuli. A basic sensil- Brusca (2003), as well as to the recent information-rich lum type is the socketed hair or ʻsetaʼ, which arises from a treatise edited by Minelli et al. (2013). flexible socket. Setae may be innervated and respond to mechanical or chemical stimuli, but chemoreceptors can also have other shapes (cones, plates etc.), and they may Arthropod body design be elevated or sunk in depressions; their surfaces have single (larger) or numerous (minute) pores permitting Few zoologists will contest the notion that the extant arthro- access for molecules of external substances. Additional pod groups descended from an ancestor with many overall sensillum types exist, but it is mostly chemoreceptors on similar segments, most if not all of which bore one pair of seg- antennae and (particularly) the larger mechanoreceptive mented limbs. The arthropod body wall comprises a single cell setae on certain trunk and limb regions that have taxo- layer (ʻepidermisʼ) which secretes an outer covering cuticle nomic importance (with respect to number, size, position mainly composed of chitin in a protein matrix. It is the shape etc.) in many groups. Broad and flat (ʻlamellarʼ) setae are and pigmentation of the cuticle that primarily determines the referred to as ʻscalesʼ. They are particularly well known external appearance of an arthropod. The cuticle forms an from the wings of moths and butterflies, but also form outer skeleton (ʻexoskeletonʼ) on which most of the animalʼs dense covers on some springtails, and occur in scattered muscles are attached (other muscles surround inner organs members of other groups as well (e.g., along wing veins of such as the gut and genital ducts). Most of the muscle attach- mosquitoes). Most scales are not innervated and this also ments are located on little-flexible parts of the body wall applies to some ʻordinaryʼ (hair-like) setae, particularly in (ʻscleritesʼ), where the cuticle is hardened and usually dark- cases where they form dense coverings. ened; the intervening flexible (and often unpigmented) body The ground plan configuration of the paired segmental wall areas are referred to as ‘membranesʼ. A generalized arthro- appendages has been much debated (for a recent review pod segment is equipped with a dorsal and ventral sclerite see Boxhall 2013). A subunit in an appendage is referred (ʻtergumʼ and ʻsternumʼ, respectively) with the segmental to as a ʻpodomere1ʼ, or as a ʻsegmentʼ (like the units in limbs arising from the lateral soft-bodied ʻpleuralʼ areas, which may bear sclerotizations between the limbs and the tergum. 1 The termination -mere (from Greek méros, part, portion) is also The patterns of ʻtagmosisʼ (or ʻtagmatizationʼ), i.e., encountered in terms such as 'antennomeres' (=subunits of the the integration of adjacent segments into functional antenna), 'flagellomeres' (=subunits of the antennal flagellum of units, ʻtagmataʼ are diagnostic of the principal arthropod Insecta s.str.) and 'tarsomeres' (=subunits of the tarsus of the leg). 4 2. Arthropod structure and systematics – Kristensen and Böcher the trunk); it is typically moved by antagonistic muscles In most arachnids the prosoma is covered by a solid arising in the podomere proximad from it. The number dorsal carapace, while its ventral surface has one or more of immediately identifiable podomeres varies across the sternal plates or is covered by the coxae of the append- principal arthropod lineages. ages. Appendages are borne on the prosoma (and its mite For obvious reasons most internal organ systems play homologues). They comprise an anterior pair called little role for practical identification of arachnids and ʻcheliceraeʼ followed by the ʻpedipalpsʼ (or just ‘palps’) and hexapods. Suffice it to note that the external openings the locomotory legs. Most arachnids are carnivores that (ʻspiraclesʼ) of the invaginated, branching tracheal (respi- capture and kill the prey (usually small arthropods) with ratory) systems of many taxa are often easily discernible the chelicerae. The pedipalps perform a variety of func- and their location, structure and/or the modification of tions related to food uptake and in some taxa (male spi- adjacent body regions is occasionally taxonomically infor- ders being an important example) to sperm transfer. mative. Similarly, the regions surrounding (or immedi- Seven podomeres are usually recognizable in arachnid ately inside) the openings of the genital systems in both locomotory legs; they are here referred to (from base to sexes are often characteristically modified. tip) as coxa, trochanter, femur, patella/genu (mite work- ers’ term), tibia, tarsus and pretarsus/metatarsus. While compound eyes as found in insects (and crusta- Systematization ceans) are entirely absent from arachnids, simple eyes may occur in variable numbers and arrangements. Mainstream zoological systematics endeavours to classify Invaginations to cuticle-lined respiratory cavities (book animals according to their phylogeny, i.e., into a hierarchy lungs and/or tracheae) are variably located. Some mites reflecting their relationships in terms of relative recency lack special respiratory organs, and gas exchange then of common ancestry. The ʻmaturityʼ of contemporary takes place through the general body wall. The genital ori- taxonomy varies considerably across the arthropods, and fice of both sexes is found on ventral side of the second it is practically certain that some of the current concepts abdominal segment except in some mites. Indirect sperm of higher taxa (e.g., families) adopted in the present work transmission is characteristic of most arachnids and in will eventually prove to refer to entities that are not mono- many cases the male produces a spermatophore; fre- phyletic in the strict sense, i.e., not including all descen- quently a more or less complex courtship behaviour pre- dants of their membersʼ last common ancestor. While cedes copulation. reference is here made, conservatively, to ʻordersʼ of Arachnid juveniles are overall similar to adults (leg arthropods, it must be emphasized that these like all other numbers in 1st instar mites excepted), but characters nec- supraspecific taxa are not in any sense ʻequivalentʼ evolu- essary for species identification are often undeveloped tionary entities, and no formal ranks are here ascribed to before sexual maturation. other higher taxa, which are above family-group rank and Currently about ten ‘orders’ are recognized in the hence not covered by naming conventions required in the Arachnida; just three of these are represented in International Code of Zoological Nomenclature. Greenland: Araneae (18.1), Opiliones (18.2) and Acari (18.3). Arachnida The myriapods Arachnids are immediately distinguishable from other extant terrestrial/limnic arthropods by the absence of The myriapods are an assemblage (perhaps indeed antennae and by presence of four pairs of locomotory monophyletic) of arthropods which all have an elongate limbs (early-instar mite juveniles excepted, they have just trunk comprising numerous leg-bearing segments, hence three). Tagmosis is also characteristic, with the body they are ʻmany-leggedʼ, as the scientific name implies. typically divided into an anterior prosoma and a posterior Like the crustaceans and hexapods they are ʻmandibulate abdomen, alternatively called opisthosoma (Fig. 18.1–1).2 arthropodsʼ in as much as their most anterior paired mouth Again the mites are aberrant in lacking this kind of body appendages are biting/chewing mandibles. They moreover division; their tagmosis patterns come in different forms resemble hexapods in having a single pair of antennae (Figs 18.3.1–1&2). and the segment between the latter and the mandibles being devoid of appendages. Most myriapod visual 2 Emboldened numerals refer to other chapters. organs are aggregations of simple eyes. The segmental .
Load more

Recommended publications
  • Hox Gene Duplications Correlate with Posterior Heteronomy in Scorpions
    Downloaded from http://rspb.royalsocietypublishing.org/ on February 17, 2015 Hox gene duplications correlate with posterior heteronomy in scorpions Prashant P. Sharma1, Evelyn E. Schwager2, Cassandra G. Extavour2 and Ward C. Wheeler1 rspb.royalsocietypublishing.org 1Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA 2Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA Research The evolutionary success of the largest animal phylum, Arthropoda, has been attributed to tagmatization, the coordinated evolution of adjacent metameres Cite this article: Sharma PP, Schwager EE, to form morphologically and functionally distinct segmental regions called Extavour CG, Wheeler WC. 2014 Hox gene tagmata. Specification of regional identity is regulated by the Hox genes, of duplications correlate with posterior which 10 are inferred to be present in the ancestor of arthropods. With six heteronomy in scorpions. Proc. R. Soc. B 281: different posterior segmental identities divided into two tagmata, the bauplan of scorpions is the most heteronomous within Chelicerata. Expression 20140661. domains of the anterior eight Hox genes are conserved in previously surveyed http://dx.doi.org/10.1098/rspb.2014.0661 chelicerates, but it is unknown how Hox genes regionalize the three tagmata of scorpions. Here, we show that the scorpion Centruroides sculpturatus has two paralogues of all Hox genes except Hox3, suggesting cluster and/or whole genome duplication in this arachnid order. Embryonic anterior expression Received: 19 March 2014 domain boundaries of each of the last four pairs of Hox genes (two paralogues Accepted: 22 July 2014 each of Antp, Ubx, abd-A and Abd-B) are unique and distinguish segmental groups, such as pectines, book lungs and the characteristic tail, while main- taining spatial collinearity.
    [Show full text]
  • Online Dictionary of Invertebrate Zoology Parasitology, Harold W
    University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Armand R. Maggenti Online Dictionary of Invertebrate Zoology Parasitology, Harold W. Manter Laboratory of September 2005 Online Dictionary of Invertebrate Zoology: S Mary Ann Basinger Maggenti University of California-Davis Armand R. Maggenti University of California, Davis Scott Gardner University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/onlinedictinvertzoology Part of the Zoology Commons Maggenti, Mary Ann Basinger; Maggenti, Armand R.; and Gardner, Scott, "Online Dictionary of Invertebrate Zoology: S" (2005). Armand R. Maggenti Online Dictionary of Invertebrate Zoology. 6. https://digitalcommons.unl.edu/onlinedictinvertzoology/6 This Article is brought to you for free and open access by the Parasitology, Harold W. Manter Laboratory of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Armand R. Maggenti Online Dictionary of Invertebrate Zoology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Online Dictionary of Invertebrate Zoology 800 sagittal triact (PORIF) A three-rayed megasclere spicule hav- S ing one ray very unlike others, generally T-shaped. sagittal triradiates (PORIF) Tetraxon spicules with two equal angles and one dissimilar angle. see triradiate(s). sagittate a. [L. sagitta, arrow] Having the shape of an arrow- sabulous, sabulose a. [L. sabulum, sand] Sandy, gritty. head; sagittiform. sac n. [L. saccus, bag] A bladder, pouch or bag-like structure. sagittocysts n. [L. sagitta, arrow; Gr. kystis, bladder] (PLATY: saccate a. [L. saccus, bag] Sac-shaped; gibbous or inflated at Turbellaria) Pointed vesicles with a protrusible rod or nee- one end. dle. saccharobiose n.
    [Show full text]
  • Zootaxa,Crustacean Classification
    Zootaxa 1668: 313–325 (2007) ISSN 1175-5326 (print edition) www.mapress.com/zootaxa/ ZOOTAXA Copyright © 2007 · Magnolia Press ISSN 1175-5334 (online edition) Crustacean classification: on-going controversies and unresolved problems* GEOFF A. BOXSHALL Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom E-mail: [email protected] *In: Zhang, Z.-Q. & Shear, W.A. (Eds) (2007) Linnaeus Tercentenary: Progress in Invertebrate Taxonomy. Zootaxa, 1668, 1–766. Table of contents Abstract . 313 Introduction . 313 Treatment of parasitic Crustacea . 315 Affinities of the Remipedia . 316 Validity of the Entomostraca . 318 Exopodites and epipodites . 319 Using of larval characters in estimating phylogenetic relationships . 320 Fossils and the crustacean stem lineage . 321 Acknowledgements . 322 References . 322 Abstract The journey from Linnaeus’s original treatment to modern crustacean systematics is briefly characterised. Progress in our understanding of phylogenetic relationships within the Crustacea is linked to continuing discoveries of new taxa, to advances in theory and to improvements in methodology. Six themes are discussed that serve to illustrate some of the major on-going controversies and unresolved problems in the field as well as to illustrate changes that have taken place since the time of Linnaeus. These themes are: 1. the treatment of parasitic Crustacea, 2. the affinities of the Remipedia, 3. the validity of the Entomostraca, 4. exopodites and epipodites, 5. using larval characters in estimating phylogenetic rela- tionships, and 6. fossils and the crustacean stem-lineage. It is concluded that the development of the stem lineage concept for the Crustacea has been dominated by consideration of taxa known only from larval or immature stages.
    [Show full text]
  • Fossils from South China Redefine the Ancestral Euarthropod Body Plan Cédric Aria1 , Fangchen Zhao1, Han Zeng1, Jin Guo2 and Maoyan Zhu1,3*
    Aria et al. BMC Evolutionary Biology (2020) 20:4 https://doi.org/10.1186/s12862-019-1560-7 RESEARCH ARTICLE Open Access Fossils from South China redefine the ancestral euarthropod body plan Cédric Aria1 , Fangchen Zhao1, Han Zeng1, Jin Guo2 and Maoyan Zhu1,3* Abstract Background: Early Cambrian Lagerstätten from China have greatly enriched our perspective on the early evolution of animals, particularly arthropods. However, recent studies have shown that many of these early fossil arthropods were more derived than previously thought, casting uncertainty on the ancestral euarthropod body plan. In addition, evidence from fossilized neural tissues conflicts with external morphology, in particular regarding the homology of the frontalmost appendage. Results: Here we redescribe the multisegmented megacheirans Fortiforceps and Jianfengia and describe Sklerolibyon maomima gen. et sp. nov., which we place in Jianfengiidae, fam. nov. (in Megacheira, emended). We find that jianfengiids show high morphological diversity among megacheirans, both in trunk ornamentation and head anatomy, which encompasses from 2 to 4 post-frontal appendage pairs. These taxa are also characterized by elongate podomeres likely forming seven-segmented endopods, which were misinterpreted in their original descriptions. Plesiomorphic traits also clarify their connection with more ancestral taxa. The structure and position of the “great appendages” relative to likely sensory antero-medial protrusions, as well as the presence of optic peduncles and sclerites, point to an overall
    [Show full text]
  • Segmentation and Tagmosis in Chelicerata
    Arthropod Structure & Development 46 (2017) 395e418 Contents lists available at ScienceDirect Arthropod Structure & Development journal homepage: www.elsevier.com/locate/asd Segmentation and tagmosis in Chelicerata * Jason A. Dunlop a, , James C. Lamsdell b a Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, D-10115 Berlin, Germany b American Museum of Natural History, Division of Paleontology, Central Park West at 79th St, New York, NY 10024, USA article info abstract Article history: Patterns of segmentation and tagmosis are reviewed for Chelicerata. Depending on the outgroup, che- Received 4 April 2016 licerate origins are either among taxa with an anterior tagma of six somites, or taxa in which the ap- Accepted 18 May 2016 pendages of somite I became increasingly raptorial. All Chelicerata have appendage I as a chelate or Available online 21 June 2016 clasp-knife chelicera. The basic trend has obviously been to consolidate food-gathering and walking limbs as a prosoma and respiratory appendages on the opisthosoma. However, the boundary of the Keywords: prosoma is debatable in that some taxa have functionally incorporated somite VII and/or its appendages Arthropoda into the prosoma. Euchelicerata can be defined on having plate-like opisthosomal appendages, further Chelicerata fi Tagmosis modi ed within Arachnida. Total somite counts for Chelicerata range from a maximum of nineteen in Prosoma groups like Scorpiones and the extinct Eurypterida down to seven in modern Pycnogonida. Mites may Opisthosoma also show reduced somite counts, but reconstructing segmentation in these animals remains chal- lenging. Several innovations relating to tagmosis or the appendages borne on particular somites are summarised here as putative apomorphies of individual higher taxa.
    [Show full text]
  • Metamerism & Tagmatization
    Phylum Arthropoda Pt. I Arthropoda Phylogeny Miller and Harley Chap. 14 Fig. 14.2 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function Arthropoda Taxonomy Metamerism & Tagmatization ● Sub-phylum Trilobitomorpha – Marine, all extinct, 3 longitudinal lobes ● Sub-phylum Chelicerata – 2 tagma (prosoma & opisthosoma), 1st pair of appendages modified into feeding chelicera ● Sub-phylum Myriapoda – Body divided into head and trunk, 4 pairs of head appendages, uniramous appendages ● Sub-phylum Crustacea – Mostly aquatic, head with 2 pairs of antennae, one pair of mandibles, 2 pairs of maxillae, biramous appendages ● Sub-phylum Hexapoda – Body divided into head, thorax and abdomen; 5 pairs of appendages on head, 3 pairs uniramous appendages on thorax only BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function Arthropod Exoskeleton Modifications & Articulations Fig. 14.4 Fig. 14.3 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function 1 Ecdysis Ecdysis Fig. 14.5 Fig. 14.5 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function Ecdysis Spider Molting Fig. 14.5 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function Crab Molting Class Merostomata Fig. 14.8 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function 2 Class Arachnida Book Lung Order Aranea Fig. 14.12 Fig. 14.9 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function Excretion Sense Organs Fig. 28.13 & 28.14 Fig. 14.10 & 14.13 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function Venomous Spiders Brown Recluse Haemolytic Venom Black Widow Brown Recluse Fig. 14.14 BIO2135 – Animal Form and Function BIO2135 – Animal Form and Function 3 Class Arachnida Class Arachnida Order Scorpionida Order Acarina Fig.
    [Show full text]
  • Arthropod Origins
    Bulletin of Geosciences, Vol. 78, No. 4, 323–334, 2003 © Czech Geological Survey, ISSN 1214-1119 Arthropod origins Jan Bergström 1 – Hou Xian-Guang 2 1 Swedish Museum of Nature History, Box 50007, S-104 05 Stockholm, Sweden. E-mail: [email protected] 2 Yunnan University, Yunnan Research Center for Chengjiang Biota, Kunming 650091, Peoples’ Republic of China. E-mail: [email protected] Abstract. Reconsideration of the position of trilobite-like arthropods leads to an idea of the last shared ancestor of known (eu)arthropods. The ancestry and morphological evolution is traced back from this form to a hypothetical ciliated and pseudosegmented slug-like ancestor. Evolution logically passed through a lobopodian stage. Extant onychophorans, Cambrian xenusians, and perhaps anomalocaridids with their kin (the Dinocaridida) may represent probable offshoots on the way. As such, these groups are highly derived and not ancestral to the arthropods. Results of molecular studies indicate a rela- tionship to moulting worms, which at first could seem to be in conflict with what was just said. However, if this is correct, the arthropod and moulting worm lineages must have diverged when some “coelomate” features such as specific vascular and neural systems were still present. The moulting worms would therefore have lost such characters, either only once or several times. Key words: arthropod origins, Anomalocaris, Tardigrada, Cambrian arthropods, Cycloneuralia, trilobitomorphs, eye ridge Introduction immediate ancestors might have looked like, and what they could not have been like. For instance, if the first arthro- Most of our important information on early arthropods co- pods were completely primitive in certain respects, they mes from such deposits as the Lower Cambrian Chengji- cannot be traced back to animals that are highly derived in ang beds, the Middle Cambrian Burgess Shale, and the Up- these respects.
    [Show full text]
  • Tagmatization in Stomatopoda
    Haug et al. Frontiers in Zoology 2012, 9:31 http://www.frontiersinzoology.com/content/9/1/31 RESEARCH Open Access Tagmatization in Stomatopoda – reconsidering functional units of modern-day mantis shrimps (Verunipeltata, Hoplocarida) and implications for the interpretation of fossils Carolin Haug1*, Wafaa S Sallam2, Andreas Maas3, Dieter Waloszek3, Verena Kutschera3 and Joachim T Haug1 Abstract Introduction: We describe the tagmatization pattern of the anterior region of the extant stomatopod Erugosquilla massavensis. For documentation we used the autofluorescence capacities of the specimens, resulting in a significant contrast between sclerotized and membranous areas. Results: The anterior body region of E. massavensis can be grouped into three tagmata. Tagma I, the sensorial unit, comprises the segments of the eyes, antennules and antennae. This unit is set-off anteriorly from the posterior head region. Ventrally this unit surrounds a large medial sclerite, interpreted as the anterior part of the hypostome. Dorsally the antennular and antennal segments each bear a well-developed tergite. The dorsal shield is part of tagma II, most of the ventral part of which is occupied in the midline by the large, partly sclerotized posterior part of a complex combining hypostome and labrum. Tagma II includes three more segments behind the labrum, the mandibular, maxillulary and maxillary segments. Tagma III includes the maxillipedal segments, bearing five pairs of sub-chelate appendages. The dorsal sclerite of the first of these tagma-III segments, the segment of the first maxillipeds, is not included in the shield, so this segment is not part of tagma II as generally thought. The second and third segments of tagma III form a unit dorsally and ventrally.
    [Show full text]
  • Crustacean Phylogeny…? Nauplius • First Larva Stage of Most “It Can Be Concluded That Crustacean Crustaceans
    Bio 370 Crustacea Main arthropod clades (Regier et al 2010) Phylum Arthropoda http://blogs.discoverm • Trilobita agazine.com/loom/201 0/02/10/blind-cousins- Subphylum (or Class) Crustacea to-the-arthropod- • Chelicerata superstars/ Mostly aquatic, with calcified exoskeleton. • Mandibulata – Myriapoda (Chilopoda, Diplopoda) Head derived from acron plus next five segments- so primitively has 5 pairs of appendages: – Pancrustacea • Oligostraca (Ostracoda, Branchiura) -2 pair antennae • Altocrustacea - 1 pair of jaws – Vericrustacea - 2 pair of maxillae » (Branchiopoda, Decapoda) - usually a median (cyclopean) eye and – Miracrustacea one pair of compound eyes » Xenocarida (Remipedia, Cephalocarida) » Hexapoda Tagmosis of trunk varies in different taxa Crustacean phylogeny…? Nauplius • first larva stage of most “It can be concluded that crustacean crustaceans. phylogeny remains essentially unresolved. • three pairs of appendages • single median (naupliar) eye Conflict is rife, irrespective of whether one compares different morphological studies, molecular studies, or both.” Appendages: Jenner, 2010: Arthropod Structure & Development 39:143– -1st antennae 153 -2nd antennae - mandibles 1 Bio 370 Crustacea Crustacean taxa you should know Remipede habitat: a sea cave “blue hole” on Andros Island. Seven species are found in the Bahamas. Class Remipedia Class Malacostraca Class Branchiopoda “Peracarida”-marsupial crustacea Notostraca –tadpole shrimp Isopoda- isopods Anostraca-fairy shrimp Amphipoda- amphipods Cladocera- water fleas Mysidacea- mysids Conchostraca- clam shrimp “Eucarida” Class Maxillopoda Euphausiacea- krill Ostracoda- ostracods Decapoda- decapods- ten leggers Copepoda- copepods Branchiura- fish lice Penaeoidea- penaeid shrimp Cirripedia- barnacles Caridea- carid shrimp Astacidea- crayfish & lobsters Brachyura- true crabs Anomura- false crabs “Stomatopoda”– mantis shrimps Class Remipedia Remipides found only in sea caves in the Caribbean, the Canary Islands, and Western Australia (see pink below).
    [Show full text]
  • The Stem Crustacean Oelandocaris Oelandica Re−Visited
    The stem crustacean Oelandocaris oelandica re−visited MARTIN STEIN, DIETER WALOSZEK, ANDREAS MAAS, JOACHIM T. HAUG, and KLAUS J. MÜLLER Stein, M., Waloszek, D., Maas, A., Haug, J.T., and Müller, K.J. 2008. The stem crustacean Oelandocaris oelandica re−visited. Acta Palaeontologica Polonica 53 (3): 461–484. The arthropod Oelandocaris oelandica from the upper Middle Cambrian “Orsten” of Sweden was recently recognized as a member of the early phase of crustacean evolution based on additional morphological detail from new specimens. Here we present a detailed investigation of all available material. It includes the description of a 400 μm long specimen proba− bly representing an early developmental stage. Variation in size correlated with variation of trunk−segment numbers al− lowed recognition of different instars. The largest specimens do not exceed an estimated length of about 1 mm, indicating that our material may consist only of immature specimens. The characteristic, extremely long antennula of O. oelandica branches into three long rods. It may have served as the major structure to sweep in food, aided by the two subsequent ap− pendages. These and the more posterior limbs were also responsible for locomotion. Minute pores on the outer edges of the posterior limbs and on the trunk tergites possibly contained sensilla originally, which may have served as water−cur− rent detectors. The presence of a minute proximal endite only on the third head appendage suggests a rather basal position of this species within Crustacea, because comparable developmental stages of other known stem crustaceans have such an endite on more of their appendages. Reconstruction of O.
    [Show full text]
  • The Sejugal Furrow in Camel Spiders and Acariform Mites
    Arachnologische Mitteilungen 43 Nuremberg, July 2012 The sejugal furrow in camel spiders and acariform mites Jason A. Dunlop, Jessica Krüger & Gerd Alberti doi: 10.5431/aramit4303 Abstract: Camel spiders (Arachnida: Solifugae) are one of the arachnid groups characterised by a prosomal dorsal shield composed of three distinct elements: the pro-, meso- and metapeltidium. These are associated respectively with prosomal appendages one to four, five, and six. What is less well known, although noted in the historical literature, is that the coxae of the 4th and 5th prosomal segments (i.e. walking legs 2 and 3) of camel spiders are also separated ventrally by a distinct membranous region, which is absent between the coxae of the other legs. We suggest that this essentially ventral division of the prosoma specifically between coxae 2 and 3 is homolo- gous with the so-called sejugal furrow (the sejugal interval sensu van der Hammen). This division constitutes a fundamental part of the body plan in acariform mites (Arachnida: Acariformes). If homologous, this sejugal furrow could represent a further potential synapomorphy for (Solifugae + Acariformes); a relationship with increasing morphological and molecular support. Alternatively, outgroup comparison with sea spiders (Pycnogonida) and certain early Palaeozoic fossils could imply that the sejugal furrow defines an older tagma, derived from a more basal grade of organisation. In this scenario the (still) divided prosoma of acariform mites and camel spiders would be plesiomorphic. This interpretation challenges the textbook arachnid character of a peltidium (or ‘carapace’) covering an undivided prosoma. Key words: Acariformes, morphology, outgroups, phylogeny, Solifugae, tagmosis Camel spiders (Arachnida, Solifugae) are a fascinating In camel spiders, schizomids (Schizomida) and pal- group of arachnids which, as their name implies, pre- pigrades (Palpigradi) the peltidium is not a single dominantly occur in arid habitats.
    [Show full text]
  • Canada Archives Canada Published Heritage Direction Du Branch Patrimoine De I'edition
    THE BURGESS SHALE: A CAMBRIAN MIRROR FOR MODERN EVOLUTIONARY BIOLOGY by Keynyn Alexandra Ripley Brysse A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Institute for the History and Philosophy of Science and Technology University of Toronto © Copyright by Keynyn Alexandra Ripley Brysse (2008) Library and Bibliotheque et 1*1 Archives Canada Archives Canada Published Heritage Direction du Branch Patrimoine de I'edition 395 Wellington Street 395, rue Wellington Ottawa ON K1A0N4 Ottawa ON K1A0N4 Canada Canada Your file Votre reference ISBN: 978-0-494-44745-1 Our file Notre reference ISBN: 978-0-494-44745-1 NOTICE: AVIS: The author has granted a non­ L'auteur a accorde une licence non exclusive exclusive license allowing Library permettant a la Bibliotheque et Archives and Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par telecommunication ou par Plntemet, prefer, telecommunication or on the Internet, distribuer et vendre des theses partout dans loan, distribute and sell theses le monde, a des fins commerciales ou autres, worldwide, for commercial or non­ sur support microforme, papier, electronique commercial purposes, in microform, et/ou autres formats. paper, electronic and/or any other formats. The author retains copyright L'auteur conserve la propriete du droit d'auteur ownership and moral rights in et des droits moraux qui protege cette these. this thesis. Neither the thesis Ni la these ni des extraits substantiels de nor substantial extracts from it celle-ci ne doivent etre imprimes ou autrement may be printed or otherwise reproduits sans son autorisation.
    [Show full text]