Morphometric measurements throughout ontogeny of selected planktic foraminiferal test species

Development plays an important part in shaping adult morphology and morphological disparity, yet its influence on evolutionary processes is seldom explored because of a lack of preservation of ontogenetic stages in the fossil record. By preserving their entire ontogenetic history within their test, and with the advent of high-resolution imaging techniques, planktic foraminifera allow us to investigate the influence of developmental constraints on disparity. Using Synchrotron radiation X-ray tomographic microscopy (SRXTM), we reconstruct the ontogenetic progression of seven species across several of the major morphotypic groups of planktic foraminifera, including morphotypes of a species exhibiting high phenotypic plasticity and closely related pseudo-cryptic sister-taxa. We show differences in growth patterns between the globigerinid species, which appear more tightly regulated within the framework of isometry from the neanic stage, and the globorotaliid species, whose adult stages present allometric trends. Morphological change through ontogeny results in a change in surface area to volume ratios. Different metabolic processes therefore dominate at different stages of ontogeny, changing the vulnerability of the organism to environmental influences over growth, from factors affecting diffusion rates in the juvenile to those affecting energy supply in the adult. These findings identify some of the parameters within which evolutionary mechanisms have to act.

Haemolymph inorganic ion composition, physiology and behaviour dependent on temperature and ambient magnesium concentration in early life history stages of Paralomis granulosa (Decapoda, Anomura, Lithodidae)

Marine brachyuran and anomuran crustaceans are completely absent from the extremely cold (-1.8 °C) Antarctic continental shelf, but caridean shrimps are abundant. This has at least partly been attributed to low capacities for magnesium excretion in brachyuran and anomuran lithodid crabs ([Mg2+]HL = 20-50 mmol/L) compared to caridean shrimp species ([Mg2+]HL = 5-12 mmol/L). Magnesium has an anaesthetizing effect and reduces cold tolerance and activity of adult brachyuran crabs. We investigated whether the capacity for magnesium regulation is a factor that influences temperature-dependent activity of early ontogenetic stages of the Sub-Antarctic lithodid crab Paralomis granulosa. Ion composition (Na+, Mg2+, Ca2+, Cl-, [SO4]2-) was measured in haemolymph withdrawn from larval stages, the first and second juvenile instars (crabs I and II) and adult males and females. Magnesium excretion improved during ontogeny, but haemolymph sulphate concentration was lowest in the zoeal stages. Neither haemolymph magnesium concentrations nor Ca2+:Mg2+ ratios paralleled activity levels of the life stages. Long-term (3 week) cold exposure of crab I to 1 °C caused a significant rise of haemolymph sulphate concentration and a decrease in magnesium and calcium concentrations compared to control temperature (9 °C). Spontaneous swimming activity of the zoeal stages was determined at 1, 4 and 9 °C in natural sea water (NSW, [Mg2+] = 51 mmol/L) and in sea water enriched with magnesium (NSW + Mg2+, [Mg2+] = 97 mmol/L). It declined significantly with temperature but only insignificantly with increased magnesium concentration. Spontaneous velocities were low, reflecting the demersal life style of the zoeae. Heart rate, scaphognathite beat rate and forced swimming activity (maxilliped beat rate, zoea I) or antennule beat rate (crab I) were investigated in response to acute temperature change (9, 6, 3, 1, -1 °C) in NSW or NSW + Mg2+. High magnesium concentration reduced heart rates in both stages. The temperature-frequency curve of the maxilliped beat (maximum: 9.6 beats/s at 6.6 °C in NSW) of zoea I was depressed and shifted towards warmer temperatures by 2 °C in NSW + Mg2+, but antennule beat rate of crab I was not affected. Magnesium may therefore influence cold tolerance of highly active larvae, but it remains questionable whether the slow-moving lithodid crabs with demersal larvae would benefit from an enhanced magnesium excretion in nature.

Mg/Ca ratios in planktonic foraminifera

The primary Mg/Ca ratio of foraminiferal shells is a potentially valuable paleoproxy for sea surface temperature (SST) reconstructions. However, the reliable extraction of this ratio from sedimentary calcite assumes that we can overcome artifacts related to foraminiferal ecology and partial dissolution, as well as contamination by secondary calcite and clay. The standard batch method for Mg/Ca analysis involves cracking, sonicating, and rinsing the tests to remove clay, followed by chemical cleaning, and finally acid-digestion and single-point measurement. This laborious procedure often results in substantial loss of sample (typically 30-60%). We find that even the earliest steps of this procedure can fractionate Mg from Ca, thus biasing the result toward a more variable and often anomalously low Mg/Ca ratio. Moreover, the more rigorous the cleaning, the more calcite is lost, and the more likely it becomes that any residual clay that has not been removed by physical cleaning will increase the ratio. These potentially significant sources of error can be overcome with a flow-through (FT) sequential leaching method that makes time- and labor-intensive pretreatments unnecessary. When combined with time-resolved analysis (FT-TRA) flow-through, performed with a gradually increasing and highly regulated acid strength, produces continuous records of Mg, Sr, Al, and Ca concentrations in the leachate sorted by dissolution susceptibility of the reacting material. Flow-through separates secondary calcite from less susceptible biogenic calcite and clay, and further resolves the biogenic component into primary and more resistant fractions. FT-TRA reliably separates secondary calcite (which is not representative of original life habitats) from the more resistant biogenic calcite (the desired signal) and clay (a contaminant of high Mg/Ca, which also contains Al), and further resolves the biogenic component into primary and more resistant fractions that may reflect habitat or other changes during ontogeny. We find that the most susceptible fraction of biogenic calcite in surface dwelling foraminifera gives the most accurate value for SST and therefore best represents primary calcite. Sequential dissolution curves can be used to correct the primary Mg/Ca ratio for clay, if necessary. However, the temporal separation of calcite from clay in FT-TRA is so complete that this correction is typically <=2%, even in clay-rich sediments. Unlike hands-on batch methods, that are difficult to reproduce exactly, flow-through lends itself to automation, providing precise replication of treatment for every sample. Our automated flow-through system can process 22 samples, two system blanks, and 48 mixed standards in <12 hours of unattended operation. FT-TRA thus represents a faster, cheaper, and better way to determine Mg/Ca ratios in foraminiferal calcite.

Trace element ratios of Globigerina bulloides from the southwest Pacific Ocean

We present Mg/Ca data for Globigerina bulloides from 10 core top sites in the southwest Pacific Ocean analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Mg/Ca values in G. bulloides correlate with observed ocean temperatures (7°C-19°C), and when combined with previously published data, an integrated Mg/Ca-temperature calibration for 7°C-31°C is derived where Mg/Ca (mmol/mol) = 0.955 * e**(0.068 * T) (r**2 = 0.95). Significant variability of Mg/Ca values (20%-30%) was found for the four visible chambers of G. bulloides, with the final chamber consistently recording the lowest Mg/Ca and is interpreted, in part, to reflect changes in the depth habitat with ontogeny. Incipient and variable dissolution of the thin and fragile final chamber, and outermost layer concomitantly added to all chambers, caused by different cleaning techniques prior to solution-based ICPMS analyses, may explain the minor differences in previously published Mg/Ca-temperature calibrations for this species. If the lower Mg/Ca of the final chamber reflects changes in depth habitat, then LA-ICPMS of the penultimate (or older) chambers will most sensitively record past changes in near-surface ocean temperatures. Mean size-normalized G. bulloides test weights correlate negatively with ocean temperature (T = 31.8 * e**(-30.5*wtN); r**2 = 0.90), suggesting that in the southwest Pacific Ocean, temperature is a prominent control on shell weight in addition to carbonate ion levels.

Temperature and photoperiod effects on sex determination in Leuresthes tenuis (fish)

In some gonochoristic species, sex is influenced not only by genotype at conception but also by the environment that offspring experience during early ontogeny (termed environmental sex determination or ESD). ESD is thought to be adaptive when seasonal variations in environmental conditions provide a sex-specific fitness advantage. In vertebrates, temperature is the most common determinant of sex, and seasonal variation in temperature serves as a temporal cue of environmental quality such as length of the growing season. Some environments, however, lack strong seasonal temperature fluctuations and other cues, particularly photoperiod, may provide a more reliable indicator of the environment offspring enter. We tested this hypothesis by rearing the offspring of the California grunion (Leuresthes tenuis, Ayres), which experiences low seasonal temperature variation in nature, under common garden conditions at three temperature and two photoperiod treatments. Our experiments revealed that both temperature and photoperiod significantly affected sex ratios in L. tenuis. More females were produced at cooler temperatures and longer day lengths, which is consistent with female biased sex ratios early in the breeding season, and likely adaptive through increased female size and fecundity. To our knowledge, this is the first documented case of photoperiod-dependent sex determination in a gonochoristic vertebrate.

Trace metals in shells of mussels and clams from deep-sea hydrothermal vent fields of the Mid-Atlantic Ridge and East Pacific Rise

Bioaccumulation of trace metals in carbonate shells of mussels and clams was investigated at seven hydrothermal vent fields of the Mid-Atlantic Ridge (Menez Gwen, Snake Pit, Rainbow, and Broken Spur) and the Eastern Pacific (9°N and 21°N at the East Pacific Rise and the southern trough of Guaymas Basin, Gulf of California). Mineralogical analysis showed that carbonate skeletons of mytilid mussel Bathymodiolus sp. and vesicomyid clam Calyptogena m. are composed mainly of calcite and aragonite, respectively. The first data were obtained for contents of a variety of chemical elements in bivalve carbonate shells from various hydrothermal vent sites. Analyses of chemical compositions (including Fe, Mn, Zn, Cu, Cd, Pb, Ag, Ni, Cr, Co, As, Se, Sb, and Hg) of 35 shell samples and 14 water samples from mollusk biotopes revealed influences of environmental conditions and some biological parameters on bioaccumulation of metals. Bivalve shells from hydrothermal fields with black smokers are enriched in Fe and Mn by factor of 20-30 relative to the same species from the Menez Gwen low-temperature vent site. It was shown that essential elements (Fe, Mn, Ni, and Cu) more actively accumulated during early ontogeny of the shells. High enrichment factors of most metals (n x 100 - n x 10000) indicate efficient accumulation function of bivalve carbonate shells. Passive metal accumulation owing to adsorption on shell surfaces was estimated to be no higher than 50% of total amount and varied from 14% for Fe to 46% for Mn.

Appendix 1: List of cladistic characters published on ammonites

The file here provided, is the list of all characters that have been used in cladistic analysis on ammonoids published so far. It constitutes the base of a study which investigates practices in characters establishment. Find here after the abstract of the article that is associated to this file. Cladistics appears as one of the most useful method to reconstruct phylogeny of fossil taxa. However, ammonoids workers tend to sulk this method. The capital step of cladistic analysis is the recognition of homology hypothesis as clue to reconstruct monophyletic clades based on the sharing of derived traits. Previous authors have suggested that coding schemes are usually direct transcription of original taxa description. However, establishing a list of characters (i.e. a matrix taxa /characters) is a very different work compared to a compilation of diagnoses. How morphology is coded in ammonoids? How coding schemes are influenced by traditional descriptions / characters? Here, we review all cladistic analyses of ammonoids published in the literature to compare characters and the way authors have dealt with the treatment of continuous characters, polymorphism and ontogeny. Several barriers are usually invoked to justify that cladistics cannot be applied to reconstruct ammonoids phylogenies. We show that an appropriate use of improvements both on ammonoids' knowledge and cladistics methodology may overcome limitations usually invoked to perform cladistic analysis on ammonoids.

Points and dates of tagging and recapture of mature cod in the southern Barents Sea in 1937-1955

Barents cod spawn in the Motovsky Bay during the periods of warming in the Arctic when proportion of mature fish in the population is high enough. Cod spawning is most likely to occur in the Motovsky Bay when large cod forage in southeastern waters, and prespawning fish migrate close by the Murmansk coast. Under such conditions cod spawn in the Motovsky Bay, but low water temperature and slow egg drift toward Murmansk coastal waters delay development of cod eggs. As a result the eggs remain at the first stage for a long time; this causes high egg mortality before hatching. Larvae that survive and become pelagic and then bottom juveniles nevertheless have little chance to survive in winter because they are not biologically ready for overwintering. Thus, delay in egg development at the first stage delays subsequent stages of fish ontogeny, and strongly impairs survival of cod juveniles from the Motovsky Bay.

Localization of ion-regulatory epithelia in embryos and hatchlings of two cephalopods

The tissue distribution and ontogeny of Na+/K+-ATPase has been examined as an indicator for ion-regulatory epithelia in whole animal sections of embryos and hatchlings of two cephalopod species: the squid Loligo vulgaris and the cuttlefish Sepia officinalis. This is the first report of the immunohistochemical localization of cephalopod Na+/K+-ATPase with the polyclonal antibody alpha (H-300) raised against the human alpha1-subunit of Na+/K+-ATPase. Na+/K+-ATPase immunoreactivity was observed in several tissues (gills, pancreatic appendages, nerves), exclusively located in baso-lateral membranes lining blood sinuses. Furthermore, large single cells in the gill of adult L. vulgaris specimens closely resembled Na+/K+-ATPase-rich cells described in fish. Immunohistochemical observations indicated that the amount and distribution of Na+/K+-ATPase in late cuttlefish embryos was similar to that found in juvenile and adult stages. The ion-regulatory epithelia (e.g., gills, excretory organs) of the squid embryos and paralarvae exhibited less differentiation than adults. Na+/K+-ATPase activities for whole animals were higher in hatchlings of S. officinalis (157.0 ± 32.4 µmol/g FM/h) than in those of L. vulgaris (31.8 ± 3.3 µmol/g FM/h). S. officinalis gills and pancreatic appendages achieved activities of 94.8 ± 18.5 and 421.8 ± 102.3 µmol ATP/g FM/h, respectively. High concentrations of Na+/K+-ATPase in late cephalopod embryos might be important in coping with the challenging abiotic conditions (low pH, high pCO2) that these organisms encounter inside their eggs. Our results also suggest a higher sensitivity of squid vs. cuttlefish embryos to environmental acid-base disturbances.

(Appendix) Stable carbon and oxygen isotopes, and Mg/Ca ratios of foraminifera from ODP Hole 154-925A

To better understand the links between the carbon cycle and changes in past climate over tectonic timescales we need new geochemical proxy records of secular change in silicate weathering rates. A number of proxies are under development, but some of the most promising (e.g. palaeoseawater records of Li and Nd isotope change) can only be employed on such large samples of mono-specific foraminifera that application to the deep sea sediment core archive becomes highly problematic. "Dentoglobigerina" venezuelana presents a potentially attractive target for circumventing this problem because it is a typically large (> 355 ?m diameter), abundant and cosmopolitan planktic foraminifer that ranges from the early Oligocene to early Pliocene. Yet considerable taxonomic and ecological uncertainties associated with this taxon must first be addressed. Here, we assess the taxonomy, palaeoecology, and ontogeny of "D." venezuelana using stable isotope (oxygen and carbon) and Mg/Ca data measured in tests of late Oligocene to early Miocene age from Ocean Drilling Program (ODP) Site 925, on Ceara Rise, in the western equatorial Atlantic. To help constrain the depth habitat of "D." venezuelana relative to other species we report the stable isotope composition of selected planktic foraminifera species within Globigerina, Globigerinoides, Paragloborotalia and Catapsydrax. We define three morphotypes of "D." venezuelana based on the morphology of the final chamber and aperture architecture. We determine the trace element and stable isotope composition of each morphotype for different size fractions, to test the validity of pooling these morphotypes for the purposes of generating geochemical proxy datasets and to assess any ontogenetic variations in depth habitat. Our data indicate that "D." venezuelana maintains a lower thermocline depth habitat at Ceara Rise between 24 and 21 Ma. Comparing our results to published datasets we conclude that this lower thermocline depth ecology for the Oligo-Miocene is part of an Eocene-to-Pliocene evolution of depth habitat from surface to sub-thermocline for "D." venezuelana. Our size fraction data advocate the absence of photosymbionts in "D." venezuelana and suggest that juveniles calcify higher in the water column, descending into slightly deeper water during the later stages of its life cycle. Our morphotype data show that d18O and d13C variation between morphotypes is no greater than within-morphotype variability. This finding will permit future pooling of morphotypes in the generation of the "sample hungry" palaeoceanographic records.

Size-related isotopic trends in Maastrichtian planktic foraminifera of DSDP Core 44-390A (Appendix B)

Stable isotope analyses were performed on ontogenetic dissections of four taxa of low latitude Late Cretaceous planktonic foraminifera from DSDP Hole 390A. The species studied include Planoglobulina acervulinoides, Planoglobulina multicamerata, Pseudoguembelina palpebra, and Racemiguembelina fructicosa. Delta18O and delta13C data indicate a deeper surface water paleohabitat for P. multicamerata than the other three taxa, and ontogenetic increases in delta18O values suggest all these taxa underwent vertical migrations from shallow to deeper surface waters. Changes in delta13C values through ontogeny include sharp increases in delta13C composition in the juvenile size intervals, a decrease in the rate of delta13C change through intermediate size intervals, and reversals to a negative trend in delta13C values in terminal size intervals. The intermediate and terminal growth changes in delta13C signals are similar to ontogenetic trends observed in some extant and Paleogene planktonic foraminifera and may result from decreasing metabolic rates through ontogeny or endosymbiont digestion prior to gametogenesis. The ontogenetic delta13C increases of 1.04?, 0.76?, 0.83?, and 0.77? in R. fructicosa, P. palpebra, P. acervulinoides, and P. multicamerata, respectively, may indicate the presence of photosymbionts. However, our review and critique of the current literature discussing photosymbiont effects on stable isotope values in living and fossil planktonic foraminifera suggests that conclusions regarding the presence of photosymbionts in fossil taxa may be more equivocal than previously thought.