The ontogeny of the cypridid ostracod Eucypris virens (Jurine, 1820) (Crustacea,Ostracoda)

The chaetotaxy (shape, structure and distribution of setae) of appendages and valve allometry during the post embryonic ontogeny of the cyprididine ostracod Eucypris virens are described. It is shown that the basic ontogenetic development of E. virens is very similar to that of other species of the family Cyprididae. During ontogeny, the chaetotaxy shows continual development on all podomeres of the limbs with the exception of the last podomere on the antennulae. The long setae on the exopodite and protopodite of the antennae have a natatory function until the actual natatory setae develop in later instars. Aesthetascs (presumed chemoreceptors) ya and y3 are the first to develop and may have an important function in the first instars. Cyprididae require a pediform limb in the posterior of the body presumably to help them to attach to substrates and this is reflected by the pediform nature of one limb at all times throughout all instars. This study has also shown that the fifth limb is most probably of thoracic origin and hence ostracods have only one pair of maxillae.     

The ontogeny of the entocytherid ostracod Uncinocythere occidentalis (Kozloff & Whitman, 1954) Hart, 1962 (Crustacea)

The Entocytheridae is a cytheroidean family that is known for its commensal mode of life on other crustaceans. However, due to their small size and large sexual dimorphism in the sizes of the carapace, the ontogeny of the entocytherids is poorly understood. This paper documents the basic body plans and pore systems of the entocytherid Uncinocythere occidentalis (Kozloff & Whitman, 1954) Hart, 1962 through ontogeny and compares them with other podocope groups. U. occidentalis has seven juvenile stages, one less than other cytheroidean groups. The general appearance of the limbs during the ontogeny of U. occidentalis is similar to that of other podocope ostracods, such as Limnocythere inopinata (Cytheroidea) Loxoconcha japonica (Cytheroidea),Eucypris virens (Cypridoidea), and Neonesidea oligodentata (Bairdioidea) with the exception of the maxillula. The adult maxillula of U. occidentalis is reduced to just a palp and third masticatory lobe (endite), and the third masticatory lobe and branchial plate of this appendage form later in the ontogeny compared with other podocope species (i.e., these features show post displacemental ontogenetic development). The number of the pore systems of the earliest juvenile (A-7) of U. occidentalis is 10, and is different from that of the corresponding stage of other cytheroidean groups which have 9. This fact, together with the different mode of development of the maxillula, indicates that the entocytherids are not only highly specialized to their commensal mode of life but that they are also phylogenetically distant from most other cytheroidean families, possibly differentiating from the others during the early evolution of the cytherids.     

Experimental assessment of the fecundity of Eucypris virens (Ostracoda, Crustacea) under natural sex ratios

1. The adaptive significance of the observed variations in sex ratios in non‐marine ostracods is unclear. This study quantified the fecundity of females taken from a presumed fully sexual Eucypris virens population that were experimentally combined with different proportions of males (male : female sex ratios: 1 : 1, 1 : 2, 1 : 4, 1 : 8 and 0 : 1). 2. The results yielded no indications that female fecundity is altered by short‐term variations in the proportion of males, at least not within the range of sex ratios that are common in natural ostracod populations. Complete removal of males, however, did strongly reduce hatching success of dried eggs. This suggests the need for multiple mating events during the reproductive lifetime of the female. It also emphasizes the need for a minimum number of males, although this minimum number evidently may be rather low, as we found a high number of spermatozoa in the seminal receptacles after a single mating event. 3. The sex ratio in the source population was strongly female biased (1 : 3.4; n = 514), whereas in the hatchling assemblages reared in the laboratory, males and females were found in equal proportions (1 : 1.0; n = 1516), irrespective of the prevailing sex ratio. This clear discrepancy is intriguing, and points to the importance of epigenetic factors for the determination of field sex ratios.     

Ontogenetic changes in stomatal size and conductance of sunflowers

The ontogenetic changes in stomatal size, frequency and conductance (g_s) on abaxial and adaxial leaf surfaces of sunflower plants (Helianthus annuus L. Russian Mammoth) were examined under controlled environmental conditions. The stomatal frequency on the adaxial and abaxial leaf surfaces decreased with leaf ontogeny and insertion level. The ratio of adaxial to abaxial stomatal frequency did not change with leaf ontogeny and insertion level, and 42–44% of total stomata was apportioned to the adaxial surface. Ontogenetic changes in stomatal pore length were detected and increased with ontogenesis. The stomatal length of both leaf surfaces had linear relationships with leaf area. Ontogenetic changes in g_s were similar between the two surfaces. However the adaxial g_s was lower than abaxial g_s in leaves of higher insertion levels. Conductance had a linear relationship with width x frequency but not with pore area.     

Ilyocypris bradyi的轮廓分析

本文试图通过对若尔盖盆地晚新生代非海相介形类化石Ilyocypris bradyi(Sars)的轮廓分析来介绍几何形态测量法在介形类化石的形态分析中的应用。分析对比后发现,虽然Ilyocypris bradyi(Sars)居群内的个体在形态上存在或多或少的差异,但这些差异之间存在连续过渡的关系,并未出现明显的分异,说明此种的种内变异是连续的。     

Size and shape changes of Ips typographus L. (Coleoptera: Scolytinae) in relation to population level

1 High intraspecific competition is known to occur during Ips typographus outbreaks, and is thought to be the main factor regulating epidemic populations by affecting beetle population productivity. However, little is known about the consequences of intraspecific competition on population quality during outbreaks, although it could have consequences on beetle population dynamics. 2 Ips typographus morphological variations among localities, years and beetle population levels were investigated in 10 Norway spruce (Picea abies) stands having various beetle damage intensities. Beetle size and shape estimators based on wing length, and using isometric size and log‐shape ratios, were employed. Field‐caught beetles were compared with beetles emerging from controlled breeding at different densities, performed in the laboratory. Beetles from this colony were also used to check the influence of breeding densities on the size estimator. 3 Size variations occurred among localities and years and were consistent with the epidemic or latent status of the beetle populations. Controlled breeding confirmed the negative effect of beetle densities encountered in the field on offspring size. Two hypotheses are formulated to explain this increase of intraspecific competition during an outbreak, but our data support the effect of host quality change between latent and epidemic populations. 4 Shape variations also occurred among localities but were unrelated to beetle population levels. No groups consistent with a geographical structure were found, suggesting low genetic variation for I. typographus populations in France.     

The ostracod fauna (Crustacea,Ostracoda) of the profundal benthos of Loch Ness

We report the results of quantitative and qualitative investigations of the ostracod fauna of the profundal benthos of Loch Ness, an oligotrophic lake in Scotland, UK. Six ostracod species were recorded from profundal samples: Candona angulata, C. candida, Cryptocandona reducta, Cypria ophthalmica, Cyclocypris ovum and Potamocypris smaragdina. In addition, Psychrodromus robertsoni was found in fish gut contents. The mean density of profundal ostracods was 262 individuals m², with an average Brillouin's Diversity of 0.7. A weak inverse relationship between fish body weight and the number of ostracods eaten is reported for Arctic charr, Salvelinus alpinus.     

The Pleistocene lake deposits of the NE Baza Basin (Spain): salinity variations and ostracod succession

The Guadix-Baza Basin in Spain covers an area of approximately 3000 km² and yields a sedimentary sequence ranging from Lower Miocene to Pleistocene. Twenty five meters of Lower Pleistocene lacustrine sediments have been located in the NE part of the Basin at about 1000 meters in altitude. This sequence which overlies dolomitic mud flat deposits consists of limestones, calcareous and dolomitic mudstones, dolostones, silty clays, sands and gravels. Salinity fluctuations and short dry episodes, related to lake level oscillations, have been recorded by textural, mineralogical and faunal changes throughout the sequence. Ostracods, which are the most commonly encountered fossils, permit to detect recurrent changes in water salinity and regime, and solute composition. The faunal changes indicate an alternation of slightly saline and bicarbonate-rich water (when ostracods and gastropods occur) with a saline NaCl-dominant water (in which ostracods, Cerastoderma bivalves and non-marine foraminifers are found).The frequent and recurrent hydrochemical changes in the Baza Basin in the Early Pleistocene point to a climate of high contrast like in the Mediterranean region today but with a greater availability of water within the system compared to the present situation in the area.     

Historical distribution patterns of trigonioidids (non-marine Cretaceous bivalves) in Asia and their palaeogeographic significance

The non-marine trigonioidid bivalves show five phases of radiation in the Cretaceous of Pal-Asia: pre-Aptian (?Valanginian/Hauterivian–Barremian), Aptian, Albian, Cenomanian and Turonian–Maastrichtian. Their distribution patterns show two distinct palaeo-river systems feeding trigonioidids. Before the Cenomanian, the river system occupied the southwestern–southern–southeastern Pal-Asian continental margin areas. During the Turonian–Maastrichtian, it extended along the line of southcentral China−eastern China−northeastern China−northern China and Mongolia−northwestern China–eastern Fergana Basin of Kyrgyzstan−western Tajikistan Basin of Tajikistan–Tashkent area of Kazakhstan−central Kyzylkum of northern Uzbekistan–Aral Sea area of Kazakhstan. Furthermore, the general trigonioidid distribution pattern demonstrates that Japan was probably attached to part of eastern China and/or Korea during the ?Valanginian/Hauterivian–Cenomanian stages.     

Ontogenetic differentiation of swimming performance in Gilthead seabream (Sparus aurata, Linnaeus 1758) during metamorphosis

The critical swimming speed (U_crit) of gilthead seabream (Sparus aurata, Linnaeus 1875) was studied in two ontogenetic phases, early (13.7-18.7 mm total length, TL) and late metamorphosis (20.4-34.3 mm TL, after the full development of fin meristics and during squamation ontogeny), under four exercise temperatures (15, 20, 25 and 28 °C). Both the exercise temperature and the ontogenetic stage had a significant effect on the relative U_crit (RU_crit) of S. aurata, with the fish of early metamorphosis phase (E group) presenting significantly higher RU_crit than those of the late metamorphosis stage (L group). This ontogenetic shift in swimming performance was accompanied by significant ontogenetic shifts of body shape and of muscle anatomy. Compared to the L group, S. aurata of the E group were characterized by a streamline body shape and significantly higher relative contribution of the slow-red muscle to the cross-sectional area of the body (31.0 ± 1.3% vs 12.0 ± 1.2% in the L group).     

Ontogenetic changes in temperature preference of Atlantic cod

Final thermal preferendum ( T ) experiments were conducted in a horizontal thermal gradient tank from the beginning of August 2001 to mid‐November 2001 using Atlantic cod Gadus morhua from 6·5 to 79·0 cm fork length ( L _F). The value of T varied significantly ( P  < 0·005) with L _F( T  = 7·23–0·054 L _F), with smaller (younger) fish choosing higher temperatures than larger (older) fish. The preferendum varied from 6·9° C for fish of 6·5 cm to 3·0° C for those of 79·0 cm. Experiments comparing fish positions in the gradient tank between thermal gradients of 0·5–11·0 and 4·5–14·5° C demonstrated that fish positions were determined by temperature selection instead of undesirable tank effects. This study is the first to demonstrate the effect of ontogeny on temperature preferences of a marine fish species.     

The ontogeny of Loxoconcha japonica Ishizaki, 1968 (Cytheroidea, Ostracoda, Crustacea)

The ontogeny of the cytheroidean species Loxoconcha japonica is documented from the earliest instar to the adult. The first instar (instar A-8) of L. japonica is different from that of cypridoidean species in that it has an additional appendage, the furca, present. From instar A-7 onwards, the appearance of the appendages is similar to that of cypridoidean and bairdioidean species. The furca is well developed in instars A-8 to A-5, and is probably an important appendage in these early instars, despite its reduced form in the adults. Some appendages of L. japonica (e.g. the antennae) gain very few setae and claws through ontogeny, compared with species from other superfamilies. This possibly reflects paedomorphic evolution of this species.     

The Ontogeny of Neonesidea oligodentata (Bairdioidea, Ostracoda, Crustacea)

This is the first detailed ontogenetic study of the appendages and carapace of a bairdioidean ostracod. This paper uses the development of the appendages and changes in the pore systems of the carapace through ontogeny to help determine the relationship between the Bairdioidea and other podocope groups. Neonesidea oligodentata has eight post-embryonic stages: one fewer than the Cypridoidea, Cytheroidea and Darwinuloidea. The first instar of N. oligodentata resembles that of the second instar of the Cypridoidea and Cytheroidea in terms of appendages, and it is postulated that there is an additional instar stage of N. oligodentata that molts within the egg. The general sequence of appearance of the limbs from instar A-7 onwards is similar to that of the Cypridoidea and Cytheroidea, but different from that of the Darwinuloidea. Like the Cypridoidea and Cytheroidea, N. oligodentata has a gap in its ontogenetic development during instar A-6, where no new Anlage is added. Pore system analysis of A-7 instars suggests that the Bairdioidea may be more closely related to the Cypridoidea than to the Cytheroidea.     

Otolith shape in juvenile cod (Gadus morhua): Ontogenetic and environmental effects

The objectives of this study were to describe the otolith shape development of cod from post-metamorphosis larvae to juveniles and to examine whether shape development is an ontogenetically determined process. Fish were reared under three different temperature regimes and two feeding levels. I examined shape by the length~width relationship of the otolith as well as the number and size of the lobes formed. Otolith size and crenulation is exclusively linked to fish size, indicating an ontogenetically determined development. Otolith shape is closely associated with the spatial development of the lobes. This process is linked with food consumption. Higher food consumption leads to a higher number of larger lobes, resulting in a more rectangular otolith. In conclusion: Otolith shape development consists of an ontogenetic component in the form of increasing size and crenulation and an environmental component impacting on the size and number of the lobes formed.     

The preservation of ostracod shells in the siliceous chalk of the Danish-Polish Furrow (Baltic Sea)

Summary The number, morphological details and structure of ostracod shells washed from chalk by mechanical disaggregation differ from those in siliceous chalk treated by hydrofluoric acid (HF, conc.). The shells studied are from erratic material (Ger. “Schollen”, “Geschiebe”) of young Quaternary deposits from Nossentin near Malchow/Mecklenburg, NE Germany; Wicko (Vietzig) near Miedzyzdroje (Misdroy), Isle of Wolin/Baltic Sea, NW Poland (Upper Turonian) and from outcropping chalk (Lower Maastrichtian) of the Island of Rügen/Baltic Sea, NE Germany as well as erratic boulders (Upper Maastrichtian), NE Germany. The differences in the number of shells and their state of preservation are primarily caused by biotic and nonbiotic influences after death, e.g. loss of organic substance and shell deformation by low pressure. Greater destruction of the shell and its sculpture is caused by pressure (sedimentary compaction), recrystallization, sparitization and accretine crystallization of the shell calcite during diagenesis. The silification process or origin of flint in chalk is caused by weakly acidic environmental conditions (pH<5) before sedimentary compaction. It is indicated by dispersed pyrite and by well-preserved siliceous radiolarian skeletons. Finely-foliated opal-CT crystals start growing between the crystallites of the ostracod shell, later on forming lepispheres. Silification is early diagenetic, as verified by the well-preserved shell sculpture and structure and the undisturbed bioturbate structure in siliceous nodules.     

Multivariate analyses of shape variation for genetically distinct groups

Many multivariate techniques have been proprosed for the analysis of shape variation. This article discusses several approaches in the context of examining shape similarities and differences for landmark data from two genetically distinct groups. Describing and understanding these variations will help develop insight into how genetically determined differences arise and are maintained. We discuss techniques based on principal component analyses including the use of a «sheared» component as the shape component and the use of a holistic size measure for adjustment of the original log-transformed measurements. Finally we examine a recently developed morphometric technique of analysis of triangles defined by sets of three appropriate landmarks.     

Ontogenetic phenotypic plasticity during the reproductive phase in Arabidopsis thaliana (Brassicaceae)

While phenotypic plasticity has been the focus of much research and debate in the recent ecological and evolutionary literature, the developmental nature of the phenomenon has been mostly overlooked. A developmental perspective must ultimately be an integral part of our understanding of how organisms cope with heterogeneous environments. In this paper I use the rapid cycling Arabidopsis thaliana to address the following questions concerning developmental plasticity. (1) Are there genetic and/or environmental differences in parameters describing ontogenetic trajectories? (2) Is ontogenetic variation produced by differences in genotypes and/or environments for two crucial traits of the reproductive phase of the life cycle, stem elongation and flower production? (3) Is there ontogenetic variability for the correlation between the two characters? I found genetic variation, plasticity, and variation for plasticity affecting at least some of the growth parameters, indicating potential for evolution via heterochronic shifts in ontogenetic trajectories. Within-population differences among families are determined before the onset of the reproductive phase, while among-population variation is the result of divergence during the reproductive phase of the ontogeny. Finally, the ontogenetic profiles of character correlations are very distinct between the ecologically meaningful categories of early- and late-flowering “ecotypes” in this species, and show susceptibility to environmental change.