Unveiling biases in soft‐tissue phosphatization: extensive preservation of musculature in the Cretaceous (Cenomanian) polychaete Rollinschaeta myoplena (Annelida: Amphinomidae)

The process of soft‐tissue phosphatization (the replication of labile tissues by calcium phosphate) is responsible for many instances of high‐resolution soft tissue preservation, often revealing anatomical insights into the animals that so preserved. However, while much work has gone into exploring key issues such as biases and micro‐controls, phosphatization remains poorly understood as a taphonomic process. Here, using camera lucida, plain‐light microscopy and SEM imagery, we address this issue by describing the taphonomy and fidelity of the musculature of Rollinschaeta myoplena Parry et al., a phosphatized annelid from the Cretaceous Konservat‐Lagerstätten of Hakel and Hjoula, Lebanon, with an unprecedented quantity of three‐dimensional soft‐tissue preservation. Analysis highlights two strong, previously recognized biases affecting the process of phosphatization: (1) a taxonomic bias restricted to R. myoplena that triggers unusually extensive phosphatization; and (2) a tissue bias whereby longitudinal and parapodial musculature show markedly higher fidelity in comparison to the musculature of the intestine and body wall circular muscles. Potential explanations for these biases include internal phosphate‐enrichment by relative muscle density, the relative rate of decay and the physiology of musculature. Incongruence between experimental decay series for polychaetes and the prevalence of labile tissue preservation over recalcitrant tissues in R. myoplena exposes the limits of decay experiments for understanding exceptional preservation.     

Effects of food quality on tissue-specific isotope ratios in the mussel <Emphasis Type="Italic">Perna perna</Emphasis>

Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis. The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months. Although not all results were significant, overall δ¹³C ratios in adductor, mantle and gill tissues gradually approached food source signatures in both diets. PERMANOVA analyses revealed significant changes over time in tissue δ¹³C (mantle and gill) with both diets and in δ¹⁵N (all tissues) and C:N ratios (mantle and gill) for one diet only. The percentage of replaced carbon isotopes were calculated for the 3 month period and differed among tissues and between diets. The tissue with the highest and lowest amount of replaced isotopes over 81 days were mantle tissue on the kelp diet (33.89%) and adductor tissue on the fish food diet (4.14%), respectively. Percentages could not be calculated for any tissue in either diet for δ¹⁵N due to the lack of significant change in tissue nitrogen. Fractionation patterns in tissues for both diets can be linked to nutritional stress, suggesting that consumer isotopic signatures are strongly dependent on food quality, which can significantly affect the degree of isotopic enrichment within a trophic level.     

First Record of Soft Tissue Preservation in the Upper Devonian of Poland

Soft tissue preservation is reported from Upper Devonian deposits of the Holy Cross Mountains, central Poland, for the first time. The preserved soft tissues are muscles associated with arthropod cuticle fragments. The muscles are phosphatized with variable states of preservation. Well-preserved specimens display the typical banding of striated muscles. Other muscle fragments are highly degraded and/or recrystallized such that their microstructure is barely visible. The phosphatized muscles and associated cuticle are fragmented, occur in patches and some are scattered on the bedding plane. Due to the state of preservation and the lack of diagnostic features, the cuticle identification is problematic; however, it may have belonged to a phyllocarid crustacean. Taphonomic features of the remains indicate that they do not represent fossilized fecal matter (coprolite) but may represent a regurgitate, but the hypothesis is difficult to test. Most probably they represent the leftover remains after arthropod or fish scavenging. The present study shows that soft tissues, which even earlier were manipulated by scavenger, may be preserved if only special microenvironmental conditions within and around the animal remains are established.     

Umbonal musculature and relationships of the Late Triassic filibranch unionoid bivalves

Exceptionally well‐preserved Late Triassic unionoids from Silesia, Poland, show prominently ornamented juvenile shells and umbonal muscle attachments that are similar to Margaritifera, which are anatomically the least derived among extant unionoids. Their phosphatized (originally chitinous and impregnated with calcium phosphate) gill supports lacked transverse connections, and occasionally some of them were separated from others, being thus at the filibranch grade, like their trigonioid ancestors. Several separate small foot elevator attachments in these unionoids indicate Trigonodidae adaptation to marine or brackish water, in which the original trigonioid strong single attachment was already split into two in the Early Triassic. The ribbing of juvenile shells suggests a change to deeper infaunal life for juvenile stages, and generally less efficient near‐surface locomotion, with a wedge‐like foot, in adults. Much later the unionoids became eulamellibranchial, which promoted the brooding of the fish that their larvae parasitize. To accomodate the classification of the order under this scenario of evolutionary changes, a new suborder Silesunionina is proposed for its filibranch members. It includes the Silesunionidae fam. nov. , with the location of umbonal muscles similar to that in the extant underived unionoids, and the Unionellidae fam. nov. , with umbonal muscles attached to the external wall of the umbonal cavity. The early Late Triassic (Carnian) Silesunio parvus gen. et sp. nov. and latest Triassic (Rhaetian) Tihkia(?) silesiaca sp. nov. are proposed. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 863–883.     

Development of cranial muscles in the actinopterygian fish Senegal bichir,Polypterus senegalus Cuvier, 1829

Polypterus senegalus Cuvier, 1829 is one of the most basal living actinopterygian fish and a member of the Actinopterygii. We analyzed the spatial and temporal pattern of cranial muscle development of P. senegalus using whole‐mount immunostaining and serial sectioning. We described the detailed structure of the external gill muscles which divided into dorsal and ventral parts after yolk exhaustion. The pattern of the division is similar to that of urodeles. We suggest that, the external gill muscles of P. senegalus are involved in spreading and folding of the external gill stem and the branches. The fibers of the external gill muscles appear postero‐lateral to the auditory capsule. In addition, the facial nerve passes through the external gills. Therefore, the external gill muscles are probably derived from the m. constrictor hyoideus dorsalis. In contrast to previous studies, we described the mm. interhyoideus and hyohyoideus fibers as independent components in the yolk‐sac larvae. The m. hyohyoideus fibers appear lateral to the edge of the ventral portion of the external gill muscles, which are probably derived from the m. constrictor hyoideus dorsalis. These findings suggest that the m. hyohyoidues is derived from the m. constrictor hyoideus dorsalis in P. senegalus . In other actinopterygians, the m. hyohyoideus is derived from the m. constrictor hyoideus ventralis; therefore, the homology of the m. hyohyoidues of P. senegalus and other actinopterygians remains unclear. J. Morphol. 278:450–463, 2017. © 2017 Wiley Periodicals, Inc.     

Decay and mineralization of soft tissue in Early Devonian boring ctenostome bryozoans

The Early Devonian of Podolia, Ukraine, has yielded phosphatized colonies of the boring ctenostome bryozoan Podoliapora doroshivi with 3‐D preservation of soft tissues. However, the feeding zooids are not anatomically complete, their preserved soft tissues comprising decay‐resistant structures such as the protective cuticular polypide sacs with presumed parietal muscles inside the wall of the sacs, the setigerous collars, the membranous orificial walls and remains of the muscle tissues. Early diagenetic apatite mineralization occured in numerous feeding zooids of Podoliapora at different stages of decay and may be important for the interpretation of decay processes in these colonial soft‐bodied fossil organisms. A setigerous collar, which is a characteristic of extant ctenostomes, occurs in P. doroshivi in several stages of decay showing progressive collapse and eventual complete loss. This study indicates that the morphological changes of collars induced by decay often resulted in connection with the membranous orificial wall, producing false anatomical structures, unrelated to structures observed in the earlier stages of decay or to the anatomical structures of extant ctenostomes. The most decay‐resistant cuticular polypide sacs mineralized as cryptocrystalline apatite in early stage of decay became degraded in later stages of decay. These data provide evidence that the anatomical interpretation of soft‐bodied fossils preserved only in the later stages of decay may have led to imprecise morphological interpretations.     

Exceptionally preserved tadpoles from the Miocene of Libros,Spain: ecomorphological reconstruction and the impact of ontogeny upon taphonomy

McNamara, M.E., Orr, P.J., Kearns, S.L., Alcalá, L., Anadón, P. & Peñalver‐Mollá, E. 2010: Exceptionally preserved tadpoles from the Miocene of Libros, Spain: ecomorphological reconstruction and the impact of ontogeny upon taphonomy. Lethaia, Vol. 43, pp. 290–306. The Libros exceptional biota from the Upper Miocene of NE Spain includes abundant frog tadpoles (Rana pueyoi) preserved in finely laminated lacustrine mudstones. The tadpoles exhibit a depressed body, short tail, low tail fins, dorso‐laterally directed eyes and jaw sheaths; these features identify the Libros tadpoles as members of the benthic lentic ecomorphological guild. This, the first ecomorphological reconstruction of a fossil tadpole, supports phylogenetic evidence that this ecology is a conserved ranid feature. The soft‐tissue features of the Libros tadpoles are characterized by several modes of preservation. The space occupied previously by the brain is defined by calcium carbonate, the nerve cord is defined by calcium phosphate, and jaw sheaths and bone marrow are preserved as organic remains. Gut contents (and coprolites adjacent to specimens) comprise ingested fine‐grained sedimentary detritus and epiphyton. The body outline and the eyespots, nares, abdominal cavity, notochord, caudal myotomes and fins are defined by a carbonaceous bacterial biofilm. A similar biofilm in adult specimens of R. pueyoi from Libros defines only the body outline, not any internal anatomical features. In the adult frogs, but not in the tadpoles, calcium phosphate and calcium sulphate precipitated in association with integumentary tissues. These differences in the mode of preservation between the adult frogs and tadpoles reflect ontogenetic factors. □Anuran, ecology, soft‐tissue, tadpoles, taphonomy.     

Assessment of the state of the Japanese scallopMizuhopecten yessoensis in Alekseeva Bight (Peter the Great Bay, Sea of Japan) based on morphological and biochemical parameters

The results of an integrated examination of the state of the scallopMizuhopecten yessoensis in Alekseeva Bight (Peter the Great Bay, Sea of Japan) are presented. In mollusks of different ages, shell height was measured; in animals of commercial size (over 100 mm), some size and weight characteristics (annual increment of shell and adductor muscle and soft tissue weight) were determined. The morphology of the digestive gland and gills was studied. In the adductor muscle and digestive gland, the concentration of heavy metals (HMs) (Hg, Cu, Zn, Mn, Pb, Cd, Ni, Co, and Cr) was determined. In the digestive gland, metallothionein and reduced glutathione concentration was also determined, as was the activity of glutathione-dependent enzymes (glutathione peroxidase and glutathione reductase). In scallops collected outside Alekseeva Bight, the linear growth rate and adductor muscle weight were on average 1.3 and 1.7 times greater, respectively, than in those collected in the bight. In scallop organs, numerous histomorphological alterations were revealed: digestive cell vacuolization and hemocyte infiltration of the digestive gland, hyperplasia and vacuolization of the respiratory epithelium, and connective tissue hypertrophy in gill filaments. The biochemical parameters of scallops from Alekseeva Bight differed substantially from those of mollusks collected outside the bight. We conclude that one of the factors negatively affecting the state of theM. yessoensis population in Alekseeva Bight is the contamination of the bight with HMs, especially mercury. This is consistent with the results of chemical analysis of bottom sediments and tissues of two mytilid species,Modiolus kurilensis andCrenomytilus grayanus, specimens of which were collected in the bight together with the scallops [3].     

Structure and formation of the adventitious tube of the Japanese watering-pot shell Stirpulina ramosa (Bivalvia, Anomalodesmata, Clavagellidae) and a comparison with that of the Penicillidae

Abstract. Stirpulina ramosa is the only extant endobenthic representative of the Clavagellidae and is restricted to the waters of Japan. A single intact adventitious tube of this species has been obtained and its structure is described. The right valve is 16 mm long and located within the adventitious tube. It has an opisthodetic ligament located on resilifers. There are anterior and posterior adductor muscle scars, a thick pallial line, and pallial and pedal gape (right valve only) sinuses. The left shell valve is but 9 mm long and is united into the fabric of the adventitious tube via the intermediary of a shelly saddle. Internally, only the anterior adductor muscle scar and a small element of the pallial line scar are identifiable on the left valve. The posterior adductor and the rest of the pallial line scar (including a pallial sinus) are, remarkably, located on the adventitious tube beyond the shell valve margin. The adventitious tube of S. ramosa is formed in a manner wholly dissimilar from that of Brechites vaginiferus (Penicillidae). In B. vaginiferus, the tube is secreted as a single entity from the general outer mantle surface, including the siphons, covering the body. As a consequence, both shell valves are incorporated into the structure of the tube and the watering pot is bilaterally symmetrical. In S. ramosa, the tube and watering pot are secreted from the mantle margin and surface surrounding and extending from the left shell valve, so that only the left valve is incorporated into its structure. A dorsally derived mantle element is progressively extended over to the right side of the body, meeting a ventrally derived counterpart that passes beneath it, forming a pleat in the calcareous structure of the right side of the tube that they secrete. This pleat extends into the complex of watering‐pot tubules and forms the pedal gape. The watering pot is thus Ω shaped. The ventrally derived mantle element forms a sinusoidal crest on the right‐hand base of the watering pot, creating a pedal gape sinus scar on the right valve. The Clavagellidae radiated widely in the Mesozoic, leaving behind a rich fossil record for Stirpulina. Only S. ramosa, however, has survived until the present. In contrast, the Cenozoic Penicillidae has a poor fossil record, but there is a rich variety of extant endobenthic watering‐pot shells. It has been argued hitherto that the two families represent a remarkable example of convergent evolution. In view of the success of the Penicillidae and thus the endobenthic, tube‐dwelling lifestyle, however, it is hard to understand why Stirpulina has largely died out—even S. ramosa being known by but one or two specimens. A study of the anatomy of S. ramosa might one day answer this question.     

Comparative myology of the mandibular and hyoid arches of sharks of the order hexanchiformes and their bearing on its monophyly and phylogenetic relationships (Chondrichthyes: Elasmobranchii)

The order Hexanchiformes currently comprises two families, Chlamydoselachidae (frilled sharks) and Hexanchidae (six‐ and seven‐gill sharks), but its monophyly and relationships with other elasmobranchs are still discussed. Previous studies of hexanchiforms addressing these issues were based mainly on external morphology, teeth, skeletal features, and molecular data, whereas the employment of characters derived from variations in muscles has not been significantly explored. Dissections of four species of Hexanchiformes (including Chlamydoselachus anguineus) are reported here describing the mandibular (musculus adductor mandibulae dorsalis, m. adductor mandibulae ventralis, m. levator labii superioris, m. intermandibularis, and m. constrictor dorsalis) and hyoidean (m. constrictor hyoideus dorsalis and ventralis) arch muscles. Our results provide new data concerning the relationships of hexanchiforms to other elasmobranchs. The m. adductor mandibulae superficialis is described and illustrated in C. anguineus, contradicting previous accounts in which is was considered absent. The anteroposterior orientation of the m. adductor mandibulae superficialis in Chlamydoselachus is similar to the pattern found in hexanchids, squaloids, and hypnosqualeans (including batoids), suggesting it was secondarily lost in Echinorhinus. This muscle therefore provides further support for the inclusion of the Chlamydoselachidae and Hexanchidae in the Squalomorphi, and not basal to all other elasmobranchs or nested within an all‐shark collective, as has been previously proposed. However, the m. adductor mandibulae superficialis originating at the jaw joint and with an aponeurotic insertion in hexanchids, squaliforms, and hypnosqualeans, may be a separate derived feature uniting these taxa. The insertion of the m. constrictor dorsalis is restricted to the postorbital articulation in hexanchids, whereas it extends farther anteriorly in C. anguineus. The insertion of the m. constrictor hyoideus dorsalis solely on the palatoquadrate is found exclusively in the Hexanchidae. We conclude that no specific pattern of mandibular or hyoid arch muscles support the monophyly of hexanchiforms (i.e., including Chlamydoselachus). J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

CADMIUM, LEAD AND COPPER IN FRESHWATER MUSSELS FROM THE ASSINIBOINE RIVER, MANITOBA, CANADA

Cadmium, lead and copper levels were examined in adductor muscle,foot, gonad, mantle, gill, and heart of 9 species of freshwatermussels from the Assini-boine River, using anodic strippingvoltametry. Metal levels in most organs were lower than in bottomsediments. The metals generally showed significantly higherconcentrations in heart and hemolymph samples than in the othertissues examined. However in four species, gill tissues showedthe highest values forcopper, and Quadrula quadnda and Ligumiarecta accumulated the greatest amounts of copper overall. Cadmiumconcentrations were particularly high in heart and hemolymphof Lampsilis radiata sili-quoidea, L. vcntricosa, and Ligumiarecta. Metal concentrations in tissues of a given species showedvarious relationships to weight of soft parts, shell length,and shell weight, but inverse correlations predominated, indicatingthat metals in many organs were less concentrated in older individuals.In L. radiatasiliquoidea and L. vcntricosa, copper concentrationswere higher in males than in females. Lead levels were alsohigher in L. vcntricosamales. (Received 24 June 1994; accepted 8 September 1994)     

Fossil reptiles from the Spanish Muschelkalk (mont‐ral and alcover,province Tarragona)

The marine tetrapods from the late Ladinian Spanish Muschelkalk deposits located between the towns of Mont‐ral and Alcover (province Tarragona) are reviewed. The fauna comprises an undetermined thalattosaur, a small cyamodontoid placodont probably referrable to Psephoderma, a possible pachypleurosaur with (if any) affinities to the Serpianosaurus‐Neusticosaurus clade, lariosaur specimens currently referred to Lariosaurus balsami, an incomplete specimen of Lariosaurus calcagnii, an endemic nothosaur (Nothosaurus cymatosauroides), and a possible pistosaur. Collectively, the faunal mix comprises endemic taxa as well as elements with affinities to the fauna of the Alpine and/or Germanic Triassic. The fauna suggests faunal interchange through the Burgundy Gate linking the southern branch of the developing Neotethys to the Germanic Basin.     

In vitro transformation of paralytic shellfish toxins in the clams Mya arenaria and Protothaca staminea

Dissected tissues of two clam species, the Pacific littleneck, Protothaca staminea, and soft-shell, Mya arenaria, were evaluated for in vitro conversion of paralytic shellfish poisoning (PSP) toxins. Tissue homogenates were incubated with purified PSP toxins to determine the time-course of toxin conversion. The effects of boiling and addition of a natural reductant (glutathione) on toxin conversion were also assessed. For P. staminea, the digestive gland showed the greatest capacity for biotransformation, followed by gill, but mantle, adductor muscle, and siphon tissues exhibited very low conversion. In this species, the production of decarbamoyl derivatives was much greater from low potency N-sulfocarbamoyl toxins than from carbamate analogues. Decarbamolyation exhibited apparent specificity for α-epimers of all toxin substrates and this reaction was inhibited by boiling. Glutathione-mediated desulfation was tissue specific and had apparent specificity for β-epimers. These observations on P. staminea suggest that the above reactions are enzyme-mediated. In contrast, there was little toxin conversion in M. arenaria homogenates, but even this low activity was heat-labile and thus likely enzyme-mediated.     

Comparative morphology of changeable skin papillae in octopus and cuttlefish

A major component of cephalopod adaptive camouflage behavior has rarely been studied: their ability to change the three‐dimensionality of their skin by morphing their malleable dermal papillae. Recent work has established that simple, conical papillae in cuttlefish (Sepia officinalis) function as muscular hydrostats; that is, the muscles that extend a papilla also provide its structural support. We used brightfield and scanning electron microscopy to investigate and compare the functional morphology of nine types of papillae of different shapes, sizes and complexity in six species: S. officinalis small dorsal papillae, Octopus vulgaris small dorsal and ventral eye papillae, Macrotritopus defilippi dorsal eye papillae, Abdopus aculeatus major mantle papillae, O. bimaculoides arm, minor mantle, and dorsal eye papillae, and S. apama face ridge papillae. Most papillae have two sets of muscles responsible for extension: circular dermal erector muscles arranged in a concentric pattern to lift the papilla away from the body surface and horizontal dermal erector muscles to pull the papilla's perimeter toward its core and determine shape. A third set of muscles, retractors, appears to be responsible for pulling a papilla's apex down toward the body surface while stretching out its base. Connective tissue infiltrated with mucopolysaccharides assists with structural support. S. apama face ridge papillae are different: the contraction of erector muscles perpendicular to the ridge causes overlying tissues to buckle. In this case, mucopolysaccharide‐rich connective tissue provides structural support. These six species possess changeable papillae that are diverse in size and shape, yet with one exception they share somewhat similar functional morphologies. Future research on papilla morphology, biomechanics and neural control in the many unexamined species of octopus and cuttlefish may uncover new principles of actuation in soft, flexible tissue. J. Morphol. 275:371–390, 2014. © 2013 Wiley Periodicals, Inc.     

Seasonal change and prolonged anoxia affect the kinetic properties of phosphofructokinase and pyruvate kinase in oysters

The effects of seasonal change, November versus July, and prolonged anoxia (96 h under N₂ gas) on the properties of phosphofructokinase and pyruvate kinase from five tissues (gill, mantle, hepatopancreas, phasic adductor, catch adductor) of the oyster, Crassostrea virginica, were investigated. Both enzymes showed tissue-specific and season-specific changes in kinetic properties; for pyruvate kinase this correlated with seasonal differences in enzyme elution patterns on hydroxylapatite chromatography. Kinetic properties of both enzymes in winter were consistent with primarily catabolic roles in glycolysis with responsiveness to cellular energy demands, whereas in summer these enzymes may be more closely regulated with respect to the biosynthetic and gluconeogenic functions of the tissues. Anoxia-induced changes in phosphofructokinase properties were relatively minor but anoxia stimulated changes in pyruvate kinase properties and elution profiles on hydroxylapatite in all tissues except mantle, with much greater effects seen for the enzyme from winter versus summer animals. For example, anoxia-induced changes in pyruvate kinase from winter gill included a fourfold rise in the substrate affinity constant for phosphoenolpyruvate, a sevenfold increase in the concentration of fructose-1,6-bisphosphate needed to activate the enzyme by 50%, and a 50% decrease in the concentration of L-alanine that inhibits activity by 50%. Changes in pyruvate kinase kinetics and hydroxylapatite elution patterns during prolonged anoxia are consistent with covalent modification of pyruvate kinase but contrary to results for many other mollusc species, anoxia exposure appears to induce a dephosphorylation of the enzyme. Accepted: 17 February 2000     

Ontogeny of the jaw and maxillary barbel musculature in the armoured catfish families Loricariidae and Callichthyidae (Loricarioidea,Siluriformes), with a discussion on muscle homologies

The neotropical loricarioid catfishes include six families, the most species‐rich of which are the Callichthyidae and the Loricariidae. Loricariidae (suckermouth armoured catfishes) have a highly specialized head morphology, including an exceptionally large number of muscles derived from the adductor mandibulae complex and the adductor arcus palatini. Terminology of these muscles varies among the literature, and no data exist on their ontogenetic origin. A detailed examination of the ontogeny of both a callichthyid and a loricariid representative now reveals the identity of the jaw and maxillary barbel musculature, and supports new hypotheses concerning homologies. The adductor mandibulae muscle itself is homologous to the A1‐OST and A3′ of basal catfishes, and the A3′ has given rise to the newly evolved loricariid retractor veli as well. The A2 and A3″ have resulted in the retractor tentaculi of Callichthyidae and the retractor premaxillae of Loricariidae. Thus, these two muscles are shown to be homologous. In Loricariidae, the extensor tentaculi consists of two separate muscles inserting on the autopalatine, and evidence is given on the evolutionary origin of the loricariid levator tentaculi (previously and erroneously known as retractor tentaculi) from the extensor tentaculi, and not the adductor mandibulae complex. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 76–96.     

Fossilized intestine casts located within closed bivalve shells: implications for palaeoecological and sedimentological studies

Marine organisms inhabiting soft‐bottom sediment are particularly susceptible to rapid sedimentation and erosion events. This article presents a novel example of fossilized intestine casts located within closed bivalve shells in relation to rapid sedimentation event from the Pleistocene sediment of the Oga Peninsula, Akita Prefecture, northern Japan. The mollusc shells were loosely packed in well‐sorted medium‐grained to coarse‐grained sandstone associated with low‐angle trough cross‐stratification. The closed shells of Glycymeris yessoensis were present in the shell concentration. The internal parts of the shells were almost hollow, being partially filled with yellow fine‐grained clay minerals (median grain size = 30.63 μm). The characteristic material within the shells clearly differed from the surrounding sediment, which consisted of coarse‐grained felsic minerals (median grain size = 449.73 μm). Furthermore, the yellow fine‐grained clay minerals within the shells were tube‐shaped, and located near the posterior adductor scar. On the basis of anatomical observation of living Glycymeris, we confirmed that part of the intestine and the anus are also placed near the posterior adductor muscle. Therefore, the yellow fine‐grained clay minerals within the shells represent the fossil remains of particles ingested by the G. yessoensis individual through suspension‐feeding, and the tube‐shaped material is interpreted as being fossilized intestine cast. These results suggest that G. yessoensis individuals were buried alive, as rapid sedimentation prevented ejection and destruction of the filling material of intestine. The presence of intestine cast within the mollusc fossils can be used for recognizing rapid sedimentation.     

Inferring internal anatomy from the trilobite exoskeleton: the relationship between frontal auxiliary impressions and the digestive system

Lerosey‐Aubril, R., Hegna, T.A. & Olive, S. 2011: Inferring internal anatomy from the trilobite exoskeleton: the relationship between frontal auxiliary impressions and the digestive system. Lethaia, Vol. 44, pp. 166–184. The digestive system of trilobites is rarely preserved. As a result, many aspects of its organization remain unknown. Fortunately, the exoskeleton sometimes preserves evidence of soft‐tissue attachment sites that can be used to infer internal anatomy. Among them are the frontal auxiliary impressions (FAIs), probable soft‐tissue insertion sites located on the fronto‐median glabellar lobe of some trilobites. FAIs are herein described in the Carboniferous trilobite Phillipsia belgica Osmólska 1970 – representing the only known example of such structures in the Proetida and their youngest occurrence. A taphonomic scenario is proposed to explain their variable preservation. Although particularly common in the Phacopina, FAIs or FAI‐like structures are also found in several orders that differ greatly. Comparisons with modern analogues suggest that FAIs might represent attachment sites for extrinsic muscles associated with a differentiated crop within the foregut. A review of purported remains of the trilobite digestive system indicates that it usually consisted of a tube‐like tract flanked by a variable number of metamerically paired diverticulae. Its anterior portion is not particularly individualized, except in a few specimens that might hint at the presence of a crop. This differentiation of a crop might have constituted a secondarily evolution of the foregut in trilobites, occurring independently in different clades. Accompanied by a strengthening of associated extrinsic muscles, this modification of the foregut might explain the presence of more conspicuous muscle insertion sites on the glabella. Study of FAIs might therefore provide new data on the anatomy of the foregut in trilobites and evidence of diverse feeding habits. □Arthropoda, digestive system, ecology, muscle scars, Proetida, Trilobita.     

Effects of light-emitting diodes on thermally-induced oxidative stress in the bay scallop Argopecten irradians

ABSTRACT

Water temperature is an important stressor that affects the physiological and biochemical responses of scallops. In this study, we investigated the effect of different light-emitting diodes (LEDs; red, green and blue) on oxidative stress in Argopecten irradians. PCR revealed MnSOD mRNA expression in the digestive diverticula, gill, adductor muscle and eye. CAT and HSP70 mRNA were expressed in the digestive diverticula, gill and adductor muscle. Additionally, we measured the changes in the expression of HSP70, MnSOD and CAT as well as H₂O₂ levels during thermal/laboratory stress. In the digestive diverticula, gill and adductor muscle, the mRNA expressions and activities and H₂O₂ levels significantly increased in response to thermal changes. The gene expressions and activities and H₂O₂ levels were significantly lower in scallops that received green LED light than in those that received no mitigating treatment. A comet assay revealed that thermal change groups had increased rates of nuclear DNA damage; however, treatment with green LED reduced the frequency of damage. The results indicated that low or high water temperature conditions induced oxidative stress in A. irradians but that green LED significantly reduced this stress.     

Comparative anatomy of the cheek muscles of Korean cobitid fishes (Ostariophysi: Cypriniformes), with the comments on their phylogenetic relationships

Cheek muscles of 16 species of all Korean cobitid species belong to six genera were examined and described in detail, with comments on their phylogenetic relationships made on the basis of characteristics of cheek muscles. Korean cobitids were divided into two groups, the Cobitis and Misgurnus groups, by five characters related to three cheek muscles (adductor mandibulae, preorbitalis, and retractor arcus palatine). The former group, comprising Cobitis, Iksookimia, Kichulchoia, Koreocobitis, and Niwaella, is defined by four apomorphies, and the latter, including Misgurnus, by a single apomorphy.