The dual role of sclerites in a gorgonian coral: Conflicting functions of support and defence

Sclerites in the gorgonian coral Briareum asbestinum perform the dual role of skeletal support against wave action and structural defence against predators. Local populations of B. asbestinum vary along gradients of decreasing water movement and decreasing predator abundance with increasing depth, such that sclerite length increases and sclerite density decreases with depth. Based on this pattern, I explored a possible trade-off between the sclerite composition that is most resistant to tearing versus most deterrent to predatory gastropods. Feeding assays revealed that artificial foods containing longer sclerites and those containing higher volume fractions of sclerites are less palatable to the gastropod Cyphoma gibbosum. However, real colonies appear constrained, in that they do not contain both long sclerites and high volume fractions at the same time. Given a choice among real colonies, snails prefer shallow-water colonies with shorter sclerites e ven though the sclerite volume fractions are high. Although least deterrent to snails, shallow-water colonies are 56% more resistant to tearing than their deep-water counterparts. Hence, variation in sclerite composition among local populations of B. asbestinum may be maintained by opposing selection for support versus defense.     

Comparative biometry and isotopy of three dominant pennatulacean corals in the Northwest Atlantic

Spatial and temporal shifts in biometric features were examined in three common deep‐water pennatulacean corals (sea pens) from the Northwest Atlantic: Anthoptilum grandiflorum, Halipteris finmarchica and Pennatula aculeata. These three species show different morphological characters and adaptations to their environment. Analyses of colony length, ratio of peduncle to colony length, weight/length ratio, polyp size and density as well as sclerite shape, location and abundance indicate that their phenotype is modulated by environmental factors (e.g. food availability, currents and sediment type) and antipredator strategies. Moreover, the three species had different carbon and nitrogen stable isotope signatures that could be explain primarily by their different polyp diameters and colony shapes, suggesting that they rely on slightly different food sources (varying proportions of phytodetritus and zooplankton). Finally, sclerites were found only in H. finmarchica and P. aculeata and are not known to occur in A. grandiflorum, except for minute oval bodies inside the peduncle. The Mg/Ca ratio of sclerites differed between the two species and, for P. aculeata, among types of sclerites, evoking different biomineralization pathways related to their functional roles (structural support or defence). Overall, this study provides new information on the ecology of poorly known species, which are ubiquitous and suspected to play an important ecological role in deep‐water ecosystems.     

Lipid content in the early life stages of three mesopelagic fishes

Changes in lipid concentration during early ontogenetic stages were determined in three mesopelagic fish species, Benthosema glaciale , Hygophum benoiti and Maurolicus muelleri . Total lipid content per larva was related to size and mass and increased over the course of development. In all three species, the dry mass : total lipid ratio displayed a better fit than the standard length : total lipid ratio. Larvae of B. glaciale had a higher amount of lipid content, at a given mass, than the other two species. The rate of lipid accumulation with increasing larval development was similar in B. glaciale and H. benoiti , and both were higher than in M. muelleri larvae. Furthermore, total lipid concentration values, as a proportion of dry mass, increased significantly from the larval to the juvenile stages in B. glaciale (from 16 to 55%) and M. muelleri (from 9 to 20%). The present study has allowed comparisons to be drawn of the ability on the early developmental stages of deep‐sea fishes to accumulate energy reserves, both within and among species.     

Breeding systems of Australian Ranunculus in the alpine region

The breeding systems of five species of Ranunculus that co-occur in the Australian alpine region were investigated in the field and glasshouse. Ranunculus muelleri, R.dissectifolius, R.graniticola, R.millanii and R.niphophilus are all facultatively xenogamous. Flowers appear to promote outcrossing by incomplete protogyny (flowers are female for 1–3 days, then bisexual for 3–10 days). Hand pollinations on plants in the field demonstrate that R.muelleri, R.graniticola, R.niphophilus and R.millanii are fully self-compatible, while R.dissectifolius is only partly self-compatible. However, low index of self-incompatibility values for R.graniticola indicate that this species may also be only partly self-compatible. Moderate levels of seed set from bagged flowers indicate that autogamous seed set due to automatic and/or possible thrips mediated intrafloral pollination may be common in all five species. Polled ovule ratios ranged from 992 to 3045 for these species of Ranunculus which are consistent with facultative xenogamy. The breeding systems of the Australian Ranunculus species in the alpine region are compared to that of other Ranunculus and examined in relation to the alpine environment.     

PROTEIN EXPRESSION DURING HEAT STRESS IN THERMO-INTOLERANT AND THERMO-TOLERANT DIATOMS

To better understand how diatoms are capable of responding to environmental stress, protein expression during heat treatment of a thermo-intolerant ( Phaeodactylum tricornutum ) and thermo-tolerant ( Chaetoceros muelleri ) diatom (Chrysophyta) was investigated. The stress response is a universal and conserved mechanism of cell survival to unfavorable conditions. Typically, a 10 to 15° C temperature elevation above cell growth optimal causes constitutively expressed proteins to decrease and heat shock proteins (HSPs) to increase. HSPs are categorized by molecular weight among five classes with each apparently specialized for a particular function that enhances cell survival. One-dimensional SDS-PAGE of diatoms subjected to heat treatment revealed that P. tricornutum exhibited a typical stress response, but C. muelleri did not exhibit a characteristic response even at a greatly elevated temperature (50° C). This result was confirmed by total soluble protein assays. Chaetoceros muelleri may contain higher basal levels of HSPs than P. tricornutum allowing C. muelleri to better tolerate elevated temperatures. Western blot analysis using pea HSP70 (70 kDa) antisera of heat-treated P. tricornutum and C. muelleri validated the hypothesis that thermo-tolerant cells contain higher levels of constitutively expressed HSPs. Two-dimensional gel electrophoresis of heat-treated cells indicate that the small HSPs (17–30 kDa) played a role in the stress response similar to that found in vascular plants. Ongoing work is focused on the manipulation of the stress response through over-expression of key hsp genes.     

The ionic composition of the plasma and erythrocytes of deep sea fish

Summary This paper reports measurements of the plasma osmolarities, the main inorganic ions and the concentrations of plasma proteins in nine species of deep sea fish from depths of 900–4,000 m. Chloride and magnesium values are high compared to those of shallow water fish. These ions may be contaminants from sea water either contributing to, or resulting from, the animals' moribund condition. They may also contribute to the failure of isolated erythrocytes to show ionic regulation even after being restored to their normal high pressure.     

Hydrological characteristics of three North African coastal lagoons: insights from the MELMARINA project

Hydrological and hydrodynamic characteristics are important controls in all wetlands including coastal lagoons. Enhanced understanding of lagoon functioning can be obtained through the acquisition and interpretation of hydrological, meteorological and related data. The MELMARINA Project investigated links between hydrological and ecological conditions within North African coastal lagoons. It employed three primary sites: Merja Zerga in Morocco, Ghar El Melh in Tunisia and Lake Manzala in Egypt. Hydrological, meteorological and related data were acquired for these lagoons. Data included precipitation, evaporation, wind speed and direction, freshwater discharges into the lagoons, tides beyond the lagoons in the open sea, lagoon bathymetry and time series of lagoon water levels/depths. Data were acquired from secondary sources (including online archives) and targeted field survey and monitoring programmes. Interpretation of these data provides insights into the hydrological functioning of the lagoons and contributed to the modelling requirements of MELMARINA. The functioning of Merja Zerga is dominated by the exchange of water between the Atlantic and the lagoon. Large, tidally induced oscillations in water level are responsible for the inundation of extensive inter-tidal mudflats whilst the rapid replacement of water by exchanges with the sea diminishes the influence of freshwater inflows and winter rainfall. The smaller Mediterranean tides reduce the magnitude of lagoon–sea exchanges and result in much smaller water level oscillations within Ghar El Melh. As a result, this lagoon lacks the inter-tidal environments found within the Moroccan site and hydrodynamic conditions are more likely influenced by wind set up. Although freshwater inflows to Ghar El Melh are smaller than those in Merja Zerga, their effects, coupled with heavy winter rainfall, can persist due to longer residence times of water within the lagoon. Freshwater inflows are central to the functioning of Lake Manzala. Large discharges of relatively freshwater are provided by major drains which cross the Nile Delta. These influence lake water levels and are responsible for the freshwater conditions within large parts of the lake. The small tidal range of the eastern Mediterranean, coupled with constricted connections with the sea, reduces the influence of lake–sea exchanges and tidally induced water level oscillations within Lake Manzala. Guest editors: J. R. Thompson & R. J. Flower Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons     

The evolution of male genitalia: patterns of genetic variation and covariation in the genital sclerites of the dung beetle Onthophagus taurus

Three main hypotheses, have been invoked to explain divergent genital evolution, the lock and key, pleiotropy, and sexual selection hypotheses, each of which make different predictions about how genital traits are inherited. Here we used a half-sib breeding design to examine the patterns of genetic variation and covariation between male genital sclerites, and their covariance with general body morphology in the dung beetle Onthophagus taurus. We found CV(A)'s and CV(P)'s were similar for both genital and general morphological traits and that CV(R)'s were large for both trait types. We found that male genital sclerites were negatively genetically correlated with general morphological traits. Variation in male genital morphology has direct implications for a male's fertilization success and the resulting sexual selection acting on male genitalia is predicted to maintain high levels of additive genetic variance. Contrary to this prediction, we found that individual genital sclerites all had low levels of additive genetic variance and large maternal and environmental sources of variation. Our data suggest that the genital sclerites in O. taurus are not inherited independently but as a genetically integrated unit. More importantly, the way the different sclerites function to influence male fertilization success reflects this genetic integration. Even though levels of V(A) in individual genital sclerites may be low, there may still be sufficient V(A) in multivariate trait space for selection to generate evolutionary change in the overall morphology of male genitalia.     

Bottom or midwater: alternative foraging behaviours in adult female loggerhead sea turtles

Intrapopulational polymorphism in habitat use is widely reported in many animal species. The phenomenon has recently also been recognized in adult female loggerhead sea turtles Caretta caretta , with small females tending to inhabit oceanic areas (where water depths are >200 m) while presumably feeding pelagically and large females tending to inhabit neritic areas (where depths are <200 m) while presumably feeding benthically. In this study, dive recording satellite telemetry units were used to verify their foraging and diving behaviours in these habitats. Two females that nested on Yakushima Island, Japan, were tracked for 124 and 197 days. The small female wandered in the oceanic Pacific, and spent most of the time at 0–25 m depths regardless of day or night, implying that she foraged pelagically at the surface and shallow depths. Her mean dive durations were significantly longer at night than during the day. The large female moved into the neritic East China Sea, and spent most of the time over the continental shelf at 100–150 m depths during the day and at 0–25 m depths at night, suggesting that she alternated between diurnal benthic foraging and nocturnal resting within the depths where she could attain neutral buoyancy. Her mean dive durations were not significantly different between day and night. The increase in dive duration for both turtles coincided with a seasonal decrease in water temperature. The small female sometimes showed midwater dormancy at 0–25 m depths with a duration of >5 h that was in contrast with bottom dormancy by sea turtles inhabiting other regions. The diving behaviours observed during this study were consistent with their estimated main feeding habits, which demonstrated resource polymorphism in a marine reptile.     

Evidence of dietary feedback in a facultative association between deep-sea gastropods and sea anemones

While epibiotic associations between macrobenthic invertebrates are common, the role they play in the feeding ecology of intervening species is often incompletely understood. The diets of epibiotic sea anemones Allantactis parasitica and their gastropod hosts were analyzed using digestive tract contents, lipid biomarkers and observations of live specimens in an attempt to detect dietary feedback from the facultative association. Comparisons were made using symbiotic individuals and asymbiotic counterparts collected at depths of 191-627 m from three neighbouring areas in the northwest Atlantic. Gastropods carrying one or two epibionts had higher stomach indices than those harbouring three epibionts or no epibiont. The diet of symbiotic gastropods was also more diversified based on stomach contents and lipid analysis. Among other things, symbiotic gastropods contained four times more lipids and a greater proportion of Σn−3 fatty acids. Gastrovascular cavity content indices of asymbiotic sea anemones were generally lower than those of symbiotic counterparts. Their cavities were more often empty, and their diet less diversified with fewer benthic items, suggesting that foraging of gastropods through the sediments makes more food available to sea anemones living as epibionts. Lipid analysis showed some disparities between symbiotic and asymbiotic sea anemones at the regional scale, including in percent phospholipids and in the proportion of certain fatty acids. Together these findings indicate that mutual protection against predators leads to prolonged and more efficient foraging for gastropods and increased time spent deployed (feeding) in food-rich areas for sea anemones, thus enabling both partners to fully exploit food resources that may be limited at bathyal depths.     

Patterns of distribution of calcite crystals in soft corals sclerites

The gross morphology of soft coral surface sclerites has been studied for taxonomic purposes for over a century. In contrast, sclerites located deep in the core of colonies have not received attention. Some soft coral groups develop massive colonies, in these organisms tissue depth can limit light penetration and circulation of internal fluids affecting the physiology of coral tissues and their symbiotic algae; such conditions have the potential to create contrasting calcifying conditions. To test this idea, we analyzed the crystal structure of sclerites extracted from different colony regions in selected specimens of zooxanthellate and azooxanthellate soft corals with different colony morphologies, these were: Sarcophyton mililatensis, Sinularia capillosa, Sinularia flexibilis, Dendronephthya sp. and Ceeceenus levis. We found that the crystals that constitute polyp sclerites differ from those forming stalk sclerites. We also observed different crystals in sclerites located at various depths in the stalk including signs of sclerite breakdown in the stalk core region. These results indicate different modes of calcification within each colonial organism analyzed and illustrate the complexity of organisms usually regarded as repetitive morphological and functional units. Our study indicates that soft corals are ideal material to study natural gradients of calcification conditions. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Parallelisms in the evolution of sea cucumbers (Echinodermata: Holothuroidea)

The importance of taking into account parallelisms in the evolution of morphological characters is analyzed for the taxonomy of the class Holothuroidea. The establishment of the order Dactylochirotida and classification of the order Elasipodida serve as examples to illustrate insufficient appreciation of parallelisms in Holothuroidea. The following characters, evolving independently in different groups of sea cucumbers, are considered: a stout skeleton, reduction of the calcareous ring and the body wall sclerites; similarity of body shape; similarity in the shape of tentacles; reduction in the number of tentacles from 12 to 10 in different fam-ilies and subfamilies of the order Synaptida. Based on the analysis of morphological and molecular data, the family Deimatidae is transferred from the order Elasipodida to the order Aspidochirotida. It is hypothesized that the concave cup-shaped sclerites with three to five rays occurring in the family Laetmogonidae (order Elasipodida) are of paedomorphic origin and correspond to the early growth stages of the laetmogonid wheels; the concave cross-shaped sclerites of the families Elpidiidae and Psychropotidae may have originated from laetmogonid concave cup-shaped sclerites. Emended diagnosis of the order Elasipodida is proposed. The family Vaneyellidae previously synonymized by the author with the family Cucumariidae is reestablished, and its emended diagnosis is also proposed.     

Chemical and structural defenses in the sea fan Gorgonia ventalina: effects against generalist and specialist predators

Cyphoma gibbosum is an ovulid predatory gastropod that specializes on gorgonians, many of which contain secondary metabolites and calcified sclerites that serve as antipredator defenses. In field and shipboard feeding assays, we examined the role of gorgonian crude extracts and sclerites as feeding deterrents to generalist predators and to C. gibbosum. Crude extracts and sclerites were isolated from Gorgonia ventalina, a Caribbean sea fan on which C. gibbosum feeds, and incorporated into a carrageenan-based artificial diet. In shipboard feeding experiments, artificial diet containing G. ventalina crude extracts was consumed 49% less by C. gibbosum, than artificial diet lacking extracts. The addition of G. ventalina sclerites to the diet also reduced feeding by Cyphoma by about one half. The addition of extracts to the artificial diet reduced feeding by natural assemblages of tropical fishes at Cross Harbor, Great Abaco Island, Bahamas by 87%; sclerites reduced feeding by fishes by 95%. Gorgonia ventalina extracts were composed of at least a dozen nonpolar terpenoids. Fractions containing these compounds were feeding deterrents towards fishes in the field. Unlike many terrestrial oligophagous specialists, C. gibbosum is not immune to the defenses produced by its prey.     

Internal wave turbulence near a Texel beach

A summer bather entering a calm sea from the beach may sense alternating warm and cold water. This can be felt when moving forward into the sea ('vertically homogeneous' and 'horizontally different'), but also when standing still between one's feet and body ('vertically different'). On a calm summer-day, an array of high-precision sensors has measured fast temperature-changes up to 1 °C near a Texel-island (NL) beach. The measurements show that sensed variations are in fact internal waves, fronts and turbulence, supported in part by vertical stable stratification in density (temperature). Such motions are common in the deep ocean, but generally not in shallow seas where turbulent mixing is expected strong enough to homogenize. The internal beach-waves have amplitudes ten-times larger than those of the small surface wind waves. Quantifying their turbulent mixing gives diffusivity estimates of 10(-4)-10(-3) m(2) s(-1), which are larger than found in open-ocean but smaller than wave breaking above deep sloping topography.     

Delphinid brain development from neonate to adulthood with comparisons to other cetaceans and artiodactyls

Why do neonatal and adult delphinids have much larger brains than artiodactyls when they have common ancestors? We explore relationships between neonatal brain size, gestation duration, maternal body mass, and body growth. Cetacean brains grow fast in the womb and longer gestation results in a larger brain. Allometry shows that the larger the mother's body mass, the larger the neonatal brain. After birth, delphinid bodies grow much faster than brains, and the index of encephalization decreases even as brains grow beyond maturity. Delphinids’ larger brain growth during life at sea may be explained by at least three differences from artiodactyls’ life on land. First, the sea offers high calorie prey to support growth of a large brain. Second, life in water offers relief from gravity, allowing for a large head to contain a large brain. Third, sound in water may pass through an immersed body. This allows sounds from the water to reach the fetus, driving early development of delphinoid auditory brain parts. As an example of this, the dolphin ear bone is very large at birth. Furthermore, the auditory nervous system appears mature well before birth. Compared with artiodactyls, these three differences likely result in a larger delphinid brain.     

The Early Cambrian tommotiid Micrina, a sessile bivalved stem group brachiopod

The tannuolinid Micrina belongs to the tommotiids-a common and widely distributed, but poorly understood, group of Early Cambrian fossil metazoans with multiple external organophosphatic sclerites. Recent findings of sessile articulated tommotiid scleritomes indicate that previous reconstructions of tommotiids as slug-like bilaterians with a dorsal cover of sclerites require detailed re-evaluation. Comparative ultrastructural work has already indicated that the tommotiids might be a sister group to the Brachiopoda, with Micrina representing the most derived and brachiopod-like bimembrate tommotiid. Here we further develop and strengthen this controversial phylogenetic model with a new reconstruction of Micrina, where the two types of sclerites--mitral and sellate--belong to a near bilaterally symmetrical bivalved sessile organism. This new scleritome configuration was tested by recreating an articulated bivalved Micrina from isolated mitral and sellate sclerites; both sclerites have muscles that would have enabled movement of the sclerites. The mitral and sellate sclerites of Micrina are considered to be homologous with the ventral and dorsal valves, respectively, of organophosphatic linguliform brachiopods, indicating that a simple type of filter-feeding within an enclosed bivalved shell had started to evolve in derived tannuolinids. The new reconstruction also indicates that the phylogenetic range of 'bivalved', sessile lophophorates is larger than previously suspected.     

Ontogeny of the jaws of monogonont rotifers: the malleate trophi of Rhinoglena and Proalides (Ploima,Epiphanidae)

Information on the embryonic development of the malleate trophi in Epiphanidae (Rotifera, Monogononta, Ploima) is presented, based on scanning electron microscopy observations in Rhinoglena fertoeensis, R. frontalis, R. kutikovae, R. tokioensis, and Proalides tentaculatus, to contribute to the understanding of this structure of high evolutionary and functional relevance in Rotifera. The first observable and distinctly sclerotized structures were a double row of median transversal sclerites along the longitudinal axis, wherein the future unci, rostellar scleropili, cristae rami, and basal apophyses became recognizable. Fulcrum and manubria arose subsequently; the fulcrum sclerites were longitudinally ordered in a double layer. The rami chambers developed last as lamellar structures. Unci appeared as separate thin, elongate elements, the primary uncini, developing to uncus plates by transversal growth and apposition of sclerite material on the shafts of the uncini. The heads of the uncini showed their greatest development after fusion of their shafts into uncus plates. The interjacent spaces between the heads functioned as a mold, organizing bundles of sclerites which developed into the uniseriate, zigzag‐shaped cristae rami. The fulcrum attained its definite shape by elongation of the double layer of rod‐shaped sclerites into appressed sclerofibrillae. Manubria became visible as a proximal ridge of sclerites, whereupon a triangular lamella composed of crisscross‐oriented sclerites developed distally, growing out to the manubrial chambers. Ramus chambers originated from two longitudinal amorphous lamellae incorporating the median rami sclerites and closing from distal to proximal; subbasal chambers were formed before the basal chambers.     

Intra-specific variation in the morphology and the benefit of large genital sclerites of males in the adzuki bean beetle (Callosobruchus chinensis)

Rapid evolution has led to a large diversity in the sizes and morphology of male genitals across taxa, but the mechanisms driving this evolution remain controversial. In this study, we investigated the function of male genital sclerites in the adzuki bean beetle (Callosobruchus chinensis) and compared the length and morphology of genital sclerites between two populations that vary in their degree of polyandry. We found that the length of male genital sclerites was negatively correlated with copulation duration but positively correlated with the speed of matings with multiple females. Additionally, we found that the average length and number of genital sclerite spines of males from the more polyandrous population were larger than those from the less polyandrous population. We suggest that the genital sclerite of male adzuki bean beetles evolved by sexual selection, and a larger genital sclerite has a selective advantage because it allows for rapid copulations with multiple females.     

The pennatulacean genus Cavernularia Valenciennes (Octocorallia: Veretillidae)

Two new species of sea pens referable to the genus Cavernularia Valenciennes are described from Natal and Transkei, east coast of southern Africa, at depths of 24 and 190 to over 300 m. The two new species are distinguished from other members of the genus by unique combinations of features regarding the axis, colonial growth form, autozooid size, as well as the size, shape, and distribution of sclerites. A comparative review of the genus is included. The 13 presently recognized worldwide species are differentiated and a key for their separation, together with a table of comparative characters, is provided. Of these, ten (77%) are Indo-Pacific in distribution whilst the remainder (23%) are presumably restricted to the eastern Atlantic. Four species are presently recorded from southern Africa. The deepest known bathymetric stations for the genus are here recorded from northern Namibia at 274 m, and from northern Natal at 310/320 m. Relationships to members of the related genus Cavernulina Kükenthal & Broch are discussed.     

Quantitative differences among the brains of cephalopods

The relative sizes of 30 lobes of the brains of 63 species of cephalopods have been compared. Some of the observed differences could be related to the way of life of the animal and others to the taxonomic relationships. The octopods are separated from the decapods by their larger brachial and other suboesophageal lobes, larger inferior frontal systems and smaller optic lobes. Vampyroteulhis lies somewhat between these two main groups. The vertical lobe system is large in sepioids and loliginids, smaller in decapods from deeper water, but large in Vampyroteuthis. In octopods, it is large in the typical epibenthic forms but smaller in those from deeper water and very small in cirrates. The inferior frontal system is very large in epibenthic octopods and Benthoctopus and in cirrates, but smaller in epipelagic and bathypelagic forms. The optic lobes are larger in decapods than in octopods from comparable depths and are especially large in deep-sea decapods. They are larger in epipelagic octopods than in the typical benthic forms. The photosensitive vesicles vary by nearly two orders of magnitude. They are very small in squids living in surface waters, larger in mesopelagic forms and enormous in some cranchiids and in Balhyteuthis. In Histioteulhis , the side with the larger eye had an optic lobe twice as big as that on the side of the smaller eye, but with only slight differences in other parts of the brain. In the octopods, the inferior frontal system was generally large, being concerned with the tactile memory system, and tends to be inversely related to the size of the optic lobe.