Carapace formation of the podocopid ostracode Semicytherura species (Crustacea: Ostracoda)

Details of ostracode carapace structures were examined by SEM and TEM. The podocopine ostracode Semicytherura kazahana has major ridges on the carapace surface and develops its prismatic layer inside the adult carapace. Electron microscopy at the final molt reveals that the major ridges arise from the highly dense formation of pits within the underlying swollen epidermis, and that disappearance of the epidermis in the presumptive area of the prismatic layer occurs after the calcification of the outer lamella cuticle, and just before synthesis of the membranous layer. These facts suggest that the formation of the carapace in Semicytherura takes place via a more complex process than that of the other podocopid ostracodes.     

Homology of Holocene ostracode biramous appendages with those of other crustaceans: the protopod, epipod, exopod and endopod

Unambiguously biramous appendages with a proximal precoxa, well-defined coxa and basis, setose plate-like epipod originating on the precoxa, and both an endopod and exopod attached to the terminal end of the basis are described from several living Ostracoda of the order Halo-cyprida (Myodocopa). These limbs are proposed as the best choice for comparison of ostracode limbs with those of other crustaceans and fossil arthropods with preserved limbs, such as the Cambrian superficially ostracode-like Kunmingella and Hesslandona. The 2nd maxilla of Metapolycope (Cladocopina) and 1st trunk limb of Spelaeoecia, Deeveya and Thaumatoconcha (all Halocypridina) are illustrated, and clear homologies are shown between the parts of these limbs and those of some general crustacean models as well as some of the remarkable crustacean s.s. Orsten fossils. No living ostracodes exhibit only primitive morphology; all have at least some (usually many) derived characters. Few have the probably primitive attribute of trunk segmentation (two genera of halocyprid Myodocopa, one order plus one genus of Podocopa, and the problematic Manawa); unambiguously biramous limbs are limited to a few halo-cyprids. Homologies between podocopid limbs and those of the illustrated primitive myodocopid limbs are tentatively suggested. A setose plate-like extension, often attached basally to a podocopid protopod, is probably homologous to the myodocopid epipod, which was present at least as early as the Triassic. Somewhat more distal, less setose, and plate-like extensions, present on some podocopid limbs (e.g., mandible), may be homologous instead to the exopod (clearly present on myodocopid mandibles). The coxa (or precoxa) is by definition the most basal part of the limb. A molar-like tooth is present proximally on the mandibular protopod of many ostracodes; it is the coxal endite and projects medially from the coxa (or proximal protopod). The Ostracoda is probably a monophyletic crustacean group composed of Myodocopa and Podocopa. All have a unique juvenile (not a larva) initially with three or more limbs. Except that juveniles lack some setae and limbs, they are morphologially similar to the adult. Thus the following suite of characters in all instars may be considered a synapomorphy uniting all Ostracoda: (1) Each pair of limbs is uniquely different from the others. (2) The whole body is completely enclosed within a bivalved carapace that lacks growth lines. (3) No more than nine pairs of limbs are present in any instar. (4) The body shows little or no segmentation, with no more than ten dorsally defined trunk segments. No other crustaceans have this suite of characters. A probable synapomorphy uniting the Podocopa is a 2nd antenna with exopod reduced relative to the endopod.     

Ultrastructure and cuticle formation of the carapace in the myodocopan ostracod exemplified by Euphilomedes japonica (Crustacea: Ostracoda)

The ultrastructure and formation of the cuticle of a myodocopan ostracod, Euphilomedes japonica, are investigated utilizing scanning and transmission electron microscopy. The outer lamella cuticle consists of four layers; epicuticle, exocuticle, endocuticle, and membranous layer like in the cuticle of other arthropods. The exocuticle and endocuticle are well-calcified and the organic matrix develops within the both cuticles. The outermost layer of new cuticle (epicuticle) is secreted first and the inner layers (exocuticle, endocuticle and membranous layer) are added proximally in the pre-, and postmoult stages. The calcification takes place in the whole area of carapace at the same time together with the synthesis of organic matrix within the endocuticle. This study demonstrates that the ultrastructure and formation of the cuticle in myodocopans are different from those in podocopans, and that the myodocopan carapaces have achieved a structural diversity for adaptation to different lifestyles.     

Experiences of a Non-Governmental Organisation (NGO) dedicated to the conservation of Arctic char <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> in Ireland

Podocopid ostracods have a calcified carapace encasing their uncalcified body parts like an envelope. A marginal infold (calcified inner lamella) develops along the free margin of both valves, notably in the adult stage. Radial pore canals, which often exhibit a distinct branched shape, can be seen in the free margin and they connect to the space between the outer and inner calcified cuticles called “vestibule.” These characters associated with the marginal infold have been recognized as important criteria both taxonomically and anatomically, but the calcification process of the marginal infold has never been investigated. In this study, we observed the calcification process of the anterior free margin in Leptocythere species. The free margin of the adult specimen starts its calcification just after ecdysis, but the degree of calcification remains the same as in the juvenile until approximately 35 h after ecdysis. The marginal infold of the adult specimen then begins to calcify from its distal part around 40 h postecdysis, and short simple pore canals can still be observed in the free margin. Marginal pore canals become more branched and narrower as calcification proceeds beyond 100 h postecdysis. These results indicate that the calcification of the free margin in a podocopid carapace occurs in two steps, and needs much time to complete the process even in small species of Leptocythere. In addition, these observations provide a basis for discussion on the correlation of the carapace size, environmental factors of the habitat, and the development of the vestibule in some Krithe species, “Krithe problem.”     

Electron microscopical localization of chitin in the cuticle of Halicryptus spinulosus and Priapulus caudatus (Priapulida) using gold-labelled wheat germ agglutinin: phylogenetic implications for the evolution of the cuticle within the Nemathelminthes

 The ultrastructure of the cuticle of adult and larval Priapulus caudatus and Halicryptus spinulosus is investigated and new features of cuticle formation during moulting are described. For the localization of chitin by TEM wheat germ agglutinin coupled to colloidal gold was used as a marker. Proteinaceous layers of the cuticle are revealed by digestion with pronase. The cuticle of larval and adult specimens of both species consists of three main layers: the outer, very thin, electron-dense epicuticle, the electron-dense exocuticle and the fibrillar, electron-lucent endocuticle. Depending on the body region, the exocuticle comprises two or three sublayers. The endocuticle can be subdivided into two sublayers as well. In strengthened parts such as the teeth, the endocuticle becomes sclerotized and appears electron-dense. Only all endocuticular layers show an intense labelling with wheat germ agglutinin-gold conjugates in all investigated specimens. Additional weak labelling is observed in the exocuticle III layer of the larval lorica of P. caudatus. All other cuticular layers remain unlabelled. Chitinase dissolves the unsclerotized endocuticular layers almost completely, but also exocuticle II and partly the loricate exocuticle III. The epicuticle, the homogeneous exocuticle I and the sclerotized endocuticle are not affected by chitinase. The labelling is completely prevented in all layers after incubation with chitinase. Pronase dissolves all exocuticular layers, but not evenly. The presumably sclerotized regions of exocuticle I are not affected as well as the complete epicuticle and the endocuticle. All cuticular features of the Priapulida are compared with the cuticle of each high-ranked taxon within the Nemathelminthes with special regard to the occurrence of chitin. Based on this out-group comparison it can be concluded that: (1) a two-layered cuticle with a trilaminate epicuticle and a proteinaceous basal layer represents an autapomorphic feature of the Nemathelminthes, (2) the stem species of the Cycloneuralia have already evolved an additional basal chitinous layer, (3) such a three-layered cuticle is maintained as a plesiomophy in the ground pattern of the Scalidophora and (4) in the Nematoida, the chitinous basal layer is replaced by a collagenous one at least in the adults; the synthesis of chitin is restricted to early developmental phases or the pharyngeal cuticle. Accepted: 12 March 1998     

Development of the mouthparts in embryos of Haplothrips verbasci (Osborn) (Insecta,Thysanoptera, Phlaeothripidae)

The asymmetric “punch and suck” mouthparts of larval Haplothrips verbasci develop from paired appendages in the late, post-anatrepsis embryo similar to those of other insects. Later, the labrum flexes ventrally over the stomodaeum, the right mandibular appendage degenerates, the maxillary appendages divide into inner (lacinial) and outer (stipital) lobes, and the hypopharynx arises from the venters of the mandibular and maxillary segments. All cephalic segments consolidate anteriorly prior to katatrepsis, their appendages flex ventrally, and the labial appendages fuse medially to form the labium and the primordia of the salivary glands and valve. The left mandible and the lacinial lobes of the maxillae invaginate into the head during and after katatrepsis to form the mandibular and maxillary stylet-secreting organs and these later deposit the cuticle of their respective stylets. Cuticle of the mandibular lever is deposited by labral cells at the apex of the mandibular sheath during and after hatching. That of each maxillary lever is secreted simultaneously into the lumen of a ventrally-directed diverticulum developing from stipital cells at the apex of each maxillary sheath. Shortly after katatrepsis, the maxillary and labial palpi originate respectively from cells in the outer wall of each stipital lobe and at the apex of the labium. Muscles of the mouthparts arise after katatrepsis from cephalic mesoderm and are fully-differentiated before cuticle of the mandibular and maxillary levers has been deposited. Gnathal morphogenesis in embryos of H. verbasci resembles that occurring in bug embryos and provides additional evidence that Thysanoptera and Hemiptera evolved from a common psocopteroid stem species having small, paired, biting and chewing mandibles and well developed lacinial stylets.     

Catechols involved in sclerotization of cuticle and egg pods of the grasshopper,Melanoplus sanguinipes,and their interactions with cuticular proteins

N‐Acetyldopamine (NADA) is the major catechol in the hemolymph of nymphal and adult grasshoppers, Melanoplus sanguinipes (F.), and mainly occurs as an acid‐labile conjugate indicated to be a sulfate ester. Its concentration increases in last instar nymphs and peaks during adult cuticle sclerotization. Dopamine (DA), the precursor of NADA and melanic pigments, is about 10 times lower in concentration than NADA, but shows a similar pattern of accumulation. NADA also predominates in cuticle, but its concentration is lowest during the active period of sclerotization, reflecting its role as a precursor for quinonoid tanning agents. Two other catechols, 3,4‐dihydroxybenzoic acid (DOBA) and 3,4‐dihydroxyphenylethanol (DOPET), also occur in hemolymph and cuticle, and their profiles suggest a role in cuticle stabilization. Solid‐state NMR analysis of sclerotized grasshopper cuticle (fifth instar exuviae) estimated the relative abundances of organic components to be 59% protein, 33% chitin, 6% catechols, and 2% lipid. About 99% of the catechols are covalently bound in the cuticle, and therefore are involved in sclerotization of the protein‐chitin matrix. To determine the types of catechol covalent interactions in the exocuticle, samples of powdered exuviae were heated in Hcl under different hydrolytic conditions to release adducts and cross‐linked products. 3,4‐Dihydroxyphenylketoethanol (DOPKET) and 3,4‐dihydroxyphenylketoethylamine (arterenone) are the major hydrolysis products in weak and strong acid, respectively, and primarily represent NADA oligomers that apparently serve as cross‐links and filler material in sclerotized cuticle. Intermediate amounts of norepinephrine (NE) are released, which represent N‐acetylnorepinephrine (NANE), a hydrolysis product of NADA bonded by the b‐carbon to cuticular proteins and possibly chitin. Small quantities of histidyl‐DA and histidyl‐DOPET ring and side‐chain C‐N adducts are released by strong acid hydrolysis. Therefore, grasshopper cuticle appears to be sclerotized by both o‐quinones and p‐quinone methides of NADA and dehydro‐NADA, which results in a variety of C‐O and C‐N covalent bonds linked primarily through the side‐chain carbons of the catechol moiety to amino acid residues in cuticular proteins. The primary catechol extracted from both the female accessory glands/calyx and the proteinaceous frothy material of the egg pod is DOBA, which also commonly occurs in cockroach accessory glands and oothecae, presumably as a tanning agent precursor. 3,4‐Dihydroxyphenylalanine (DOPA) was also detected in extracts of the accessory glands/calyx of grasshoppers, and may serve as a precursor for DOBA synthesis. Arch. Insect Biochem. Physiol. 40:119–128, 1999. © 1999 Wiley‐Liss, Inc.     

Ultrastructure of the nymphal integument in the camel tick Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae)

The ultrastructure of the nymphal integument in the ixodid tick Hyalomma (Hyalomma) dromedarii is compared for stages of development during and after feeding, and up to the first step of molting, apolysis. The integument comprises a cuticular layer and underlying epidermal cells. The body cuticle, which consists of both sclerotized and non-sclerotized parts, is divided into an outer, thin epicuticle, and an inner, thick, fibrillar procuticle. Pore canals in the procuticle are continuous with wax canals which traverse the epicuticle. As feeding progresses, the parallel, extensible epicuticular folds disappear due to the gut filling with ingested blood. The procuticular zone, however, becomes subdivided into an exocuticle, similar to the previously seen procuticle, and a lamellate endocuticle. Pore canals lose their parallel pattern and appear to have become deformed by stretching of the cuticle. The flat epidermal cells grow asynchronously during feeding; their cytoplasm becomes packed with well-developed rough endoplasmic reticulum (RER), while the cell apices project long microvilli extending deep into the procuticle. The RER undergoes ultrastructural changes indicating synthetic activity. Dense material released through the microvilli may serve to lyse the endocuticle and thus cause separation of the cuticle from the epidermis during apolysis. The lysed area, the exuvial cavity, is filled with lysed components which are probably withdrawn by endocytosis into the apical coated vesicles which appear in epidermal cells. Two types of integumental glands, which may participate in wax production, are observed in this study. The ultrastructure of their previously undescribed cuticular ducts is described, in addition to other hypodermal structures including epidermis-muscle attachments and sensory receptors.     

Ultrastructure of the body wall of three species of Grania (Annelida: Clitellata: Enchytraeidae)

De Wit P., Erséus C. and Gustavsson L.M. 2011. Ultrastructure of the body wall of three species of Grania (Annelida: Clitellata: Enchytraeidae). —Acta Zoologica (Stockholm) 92 : 1–11. The body wall of three species of Grania, including the cuticle, epidermis and the musculature, are studied using TEM. The cuticle is similar to previously studied enchytraeids, with an orthogonal grid pattern of collagen fibers. This pattern is also seen in Crassiclitellata, which has been suggested as the sister taxon of Enchytraeidae. Variation of epicuticular and fiber zone patterns seen in Naididae (formerly Tubificidae and Naididae) seem to be lacking in Enchytraeidae. The fiber thickness, however, varies between Grania species and may be a phylogenetically informative character. The epidermis consists of supporting cells, secretory cells and sensory cells. Basal cells, typical for Crassiclitellata, were not observed. The clitellum of Grania seems to consist of two types of gland cells, which develop from regular epidermal tissue. It is possible that more cell types exist in different regions of the clitellum, however. The body wall musculature is arranged somewhat differently from that of closely related taxa; this refers to the reduction of circular and outer, triangular longitudinal muscle fibers, while the inner, ribbon‐shaped longitudinal muscle fibers are well‐developed. A search was conducted for the cause of the peculiar green coloration of Grania galbina De Wit and Erséus 2007, and it was concluded that neither cyanobacteria nor epidermal pigment granules were present in the fixed material.     

The basicoxal gland, a new exocrine structure in poneromorph ants (Hymenoptera, Formicidae)

The tegumental epithelium of the outer dorsolateral region in the proximal part of the coxae in the mid‐ and hindlegs of both workers and queens of the ants Odontomachus rixosus and O. simillimus is differentiated into a conspicuous and hitherto unknown exocrine gland. The glandular cells display a clear microvillar differentiation of their apical cell membrane, and are lined with the tegumental cuticle, which in this part contains crack‐like channels perpendicular to its surface, that carry the glandular secretions to the outside. Apical microvilli support the transport of substances, and contain an extension of tubular smooth endoplasmic reticulum in their centre. The function of the gland may be that of providing lubricant substances to the articulation region of the generally heavily sclerotized ponerine ant species. The gland is also found in several other ponerine and amblyoponine species, but not in the ectatommine species studied. The foreleg coxae lack a basicoxal gland in all species examined, which may be explained by the more limited articulation between the thorax and the coxae in the forelegs compared to the mid‐ and hindlegs.     

An ultrastructural analysis of the cuticle,epidermis and esophageal epithelium of Eisenia foetida (Oligochaeta)

The epidermis of Eisenia is covered by a cuticle and rests on a basement lamella. The cuticle, which is resistant to a variety of enzymes, is composed of non-striated, bundles of probable collagen fibers that are orthogonally oriented and are embedded in a proteoglycan matrix. The basement lamella consists of striated collagen fibers with a 560 Å major periodicity. Proximity and morphology suggest that the epidermis may contribute to both the cuticle and the basement lamella — that is, the single tissue may synthesize at least two types of collagen. The epidermis is a pseudostratified epithelium containing three major cell types (columnar, basal and gland) and a rare fourth type with apical cilia. The esophagus is lined by a simple cuticulated epithelium composed predominantly of a single cell type, which resembles the epidermal columnar cell. Rare gland cells occur in the esophageal epithelium, but basal cells are lacking.     

Effect of gland extracts on digging and residing preferences of red imported fire ant workers (Hymenoptera: Formicidae)

There is evidence that ant‐derived chemical stimuli are involved in regulating the digging behavior in Solenopsis invicta Buren. However, the source gland(s) and chemistry of such stimuli have never been revealed. In this study, extracts of mandibular, Dufour's, postpharyngeal, and poison glands were evaluated for their effect on ant digging and residing preferences of S. invicta workers from three colonies. In the intracolonial bioassays, workers showed significant digging preferences to mandibular gland extracts in 2 of 3 colonies and significant residing preferences in 1 of 3 colonies; significant digging preferences to Dufour's gland extracts in 1 of 3 colonies and significant residing preferences in 2 of 3 colonies. No digging and residing preferences were found for postpharyngeal and poison gland extracts. In intercolonial bioassays, significant digging and residing preferences were found for mandibular gland extracts in 3 of 6 colony combinations. Significant digging preferences to Dufour's gland extracts were found in 4 of 6 colony combinations and significant residing preferences in all 6 colony combinations. For postpharyngeal gland extracts, significant digging preferences were found only in 1 of 6 colonial combinations and no significant residing preferences were found. For poison gland extracts, no significant digging preferences were found; significant residing preferences were found in 1 of 6 colony combinations. However, a significant residing deterrence (negative residing preference index) was found for 2 of 6 colony combinations. Statistical analyses using data pooled from all colonies showed that mandibular and Dufour's gland extracts caused significant digging and residing preferences in both intracolonial and intercolonial bioassays but not postpharyngeal and poison gland extracts. By analyzing the data pooled from the same three colonies used for gland extract bioassays, it was found that, in no cases, workers showed significant digging and residing preferences to 2‐ethyl‐3,6‐dimethylpyrazine, an alarm pheromone component from mandibular gland.     

The jaw apparatuses of Cretaceous Phylloceratina (Ammonoidea)

The jaw apparatuses of two species of Late Cretaceous Phylloceratina (Ammonoidea), Hypophylloceras subramosum and Phyllopachyceras ezoensis, are described on the basis of well‐preserved in situ material from Hokkaido, Japan. Gross morphological and X‐ray CT observations reveal that the upper and lower jaws of the two species are essentially similar in their overall structure. Their upper jaws consist of a shorter outer lamella and a pair of larger, wing‐like inner lamellae that become narrower and join together in the anterior portion, as in those of other ammonoids. The upper jaws of the two phylloceratid species are, however, distinguishable from those of other known ammonoids by the presence of a thick, arrowhead‐shaped calcified rostral tip. The lower jaws of the two species consist of a short, reduced inner lamella and a large, gently convex outer lamella covered with a thin calcareous layer, the features of which are common with the rhynchaptychus‐type lower jaws of the Cretaceous Lytoceratina. In the presence of a sharply pointed, thick calcareous tip on upper and lower jaws, the jaw apparatuses of the Phylloceratina resemble those of modern and fossil nautilids, suggesting that they were developed to serve a scavenging predatory feeding habit in deeper marine environments. This and other studies demonstrate that at least some Mesozoic rhyncholites and conchorhynchs are attributable to the Phylloceratina and Lytoceratina.     

The cuticle of the enigmatic arthropod Phytophilaspis and biomineralization in Cambrian arthropods

Lin, J.‐P., Ivantsov, A.Y. & Briggs, D.E.G. 2011: The cuticle of the enigmatic arthropod Phytophilaspis and biomineralization in Cambrian arthropods. Lethaia, Vol. 44, pp. 344–349. Many non‐trilobite arthropods occur in Cambrian Burgess Shale‐type (BST) biotas, but most of these are preserved in fine‐grained siliciclastics. Only one important occurrence of Cambrian non‐trilobite arthropods, the Sinsk biota (lower Sinsk Formation, Botomian) from the Siberian Platform, has been discovered in carbonates. The chemical compositions of samples of the enigmatic arthropod Phytophilaspis pergamena Ivantsov, 1999 and the co‐occurring trilobite Jakutus primigenius Ivantsov in Ponomarenko, 2005 from this deposit were analysed. The cuticle of P. pergamena is composed of mainly calcium phosphate and differs from the cuticle of J. primigenius, which contains only calcium carbonate. Phosphatized cuticles are rare among large Cambrian arthropods, except for aglaspidids and a few trilobites. Based on recent phylogenetic studies, phosphatization of arthropod cuticle is likely to have evolved several times. □arthropod cuticle, Burgess Shale‐type preservation, fossil‐diagenesis, phosphatization.     

Ultrastructure of an integumental organ with probable sensory function in Paragordius varius (nematomorpha)

The cuticle of late parasitic stages of Paragordius varius (Leidy, 1851) is composed of a layer with large fibres and a second layer (often named the areolar layer) distal from it. In this paper, organs are described that start at the basal side of the epidermis, pass the epidermis and the fibrous layer of the cuticle and merge with large, cushion‐like structures in the distal layer of the cuticle. The epidermal part of the organs is composed of darkly stained cells, which are probably in contact with the basi‐epidermal nervous system. Up to four processes of this cell traverse the cuticle. These processes might include cilia, because they contain microtubule‐like structures. The probable connection to nerve cells and the connection to the cushion‐like structures in the outer cuticular layer make it likely that the organs described here are sensory in function.     

The Ultrastructure of the Compound Eye of Two Species of Marine Ostracodes (Crustacea: Ostracoda: Cypridinidae)

Ultrastructurally, the compound eyes of the luminescent marine ostracodes Vargula graminkola and V. tsujii are similar. These ostracodes have two lateral compound eyes, with relatively few ommatidia (13 and 20 respectively). They exhibit apposition type compound eyes as seen in many other arthropods. Each ommatidium includes: a flat, ectodermal cuticular covering, corneagen cells, two long cone cells that give rise to a large conspicuous crystalline cone, retinular cells, pigment cells, a microvillar rhabdom and proximal axonal neurons. The axons merge to form an optic nerve that extends into the brain through a short, muscular stalk that is surrounded externally by a cuticle. The number of retinular cells is typically six per ommatidium in V. graminicola and eight per ommatidium in V. tsujii. Screening pigment cells surround each ommatidium forming a layer that is about 5–15 pigment granules thick. In addition to pigment cells, the cytoplasm of the retinular cells includes numerous screening pigment granules. In light/dark adaptation, there are no obvious morphological differences in the orientation of the rhabdom or in the organization of the screening pigments. Both Vargula species studied are nocturnally active and bioluminescent suggesting that these eyes are capable receptors of the bright conspecific luminescence.     

Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea)

Tanabe, K., Landman, N.H. & Kruta, I. 2011: Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea). Lethaia, Vol. 45, pp. 191–199. Based on the differences in their relative size, overall shape, structure and the degree of development of an outer calcified covering, lower jaws of the Ammonoidea have been classified into four morphotypes: normal, anaptychus, aptychus and rhynchaptychus types. However, detailed microstructural and mineralogical comparison of these morphotypes has not yet been addressed. This article documents the results of SEM and XRD observations of the lower jaws of three Late Cretaceous ammonoid species belonging to the Tetragonitoidea (Anagaudryceras limatum) and Desmoceratoidea (Pachydiscus kamishakensis and Damesites aff. sugata), based on excellent material preserved in situ within the body chamber, and retaining an aragonitic shell wall. The lower jaws of the three species are assigned to an intermediate form between anaptychus and aptychus types for the first two species and the rhynchaptychus type for the third species. Their black, presumably originally chitinous outer lamella is wholly covered with a calcareous layer. The calcareous layer is composed of aragonite in D. aff. sugata and A. limatum, and calcite in P. kamishakensis. The microstructure of the outer calcareous layer differs among the three species, i.e. granular in A. limatum, spherulitic prismatic in D. sugata, and prismatic in P. kamishakensis, all of which can be distinguished from the lamellar and spongy structure of the outer‐paired calcitic plates of the typical aptychus‐type lower jaws in some Jurassic and Cretaceous Ammonitina and Ancyloceratina. Our study suggests that most Jurassic and Cretaceous ammonoids possessed an outer calcareous layer in their lower jaws, although its mineralogy, microstructure and relative thickness vary among different taxa. □Ammonoidea, Cretaceous, Desmoceratoidea, lower jaw, microstructure, Tetragonitoidea.     

New insights into the buccal apparatus of the Goniatitina: palaeobiological and phylogenetic implications

Exceptionally well‐preserved radulae and lower jaws found both inside the body chamber of Cravenoceras fayettevillae (Mississippian) and in isolated nodules (Mississippian and Pennsylvanian) were analysed using CT scan and synchrotron propagation phase‐contrast tomography. This approach reveals new anatomical details allowing us to investigate wear, preservation and muscle insertion in the buccal mass of the Goniatitina. For comparison, Recent cephalopod radulae were also investigated. The radula in the Goniatitina consists of nine elements per row, and its morphology is conservative in the group. The shape of the teeth is similar to that in some Recent coleoids. The lower jaw is morphologically closer to that of Recent Nautilus, consisting of a wide outer lamella and a reduced inner lamella. The morphology of the inner lamella reflects the outer lamella in smaller dimensions and does not protrude posteroventrally. The space between the inner and outer lamellae allows for muscle insertion. Our morphological data indicate that a mosaic of characters is present in the buccal mass of Goniatitina with some parts of the buccal mass being more primitive than others. This implies that different parts of the buccal mass may have followed different evolutionary histories.     

The integumental ultrastructure of Lamippe rubra Bruzelius and Enalcyonium rubicundum Olsson (Copepoda,Poecilostomatoida)

The integument of Lamippe rubra Bruzelius and of Enalcyonium rubicundum Olsson has been studied with the electron microscope.Most of the cuticle covering the body of Lamippe is represented by the epicuticle, which shows an average thickness of about 2.0 µm, but in sclerified zones it consists of a thin epicuticle (0.2 µm) and a stratified laminated procuticle (0.5–1.5 µm) without bow-shaped structure. A complex system of epithelial microvilli or a well-developed system of membranes running parallel to the cuticle is also present.The cuticle of Enalcyonium consists of a thin procuticle (0.4–0.5 µm) covered with a uniform fibrillar coat (0.5 µm), whereas in sclerotized areas it is composed of a stratified procuticle (0.7–3.5 µm) with bow-shaped structures.In both species, cuticular hairs and gland vents occur at the dorsal and ventral surfaces. Some of the hairs are considered to be sensory in nature.The cuticular ultrastructure of L. rubra and of E. rubicundum is compared with that of some other copepods.