Human activities accelerated the degradation of saline seepweed red beaches by amplifying top‐down and bottom‐up forces

Salt marshes dominated by saline seepweed (Suaeda heteroptera) provide important ecosystem services such as sequestering carbon (blue carbon), maintaining healthy fisheries, and protecting shorelines. These salt marshes also constitute stunning red beach landscapes, and the resulting tourism significantly contributes to the local economy. However, land use change and degradation have led to a substantial loss of the red beach area. It remains unclear how human activities influence the top‐down and bottom‐up forces that regulate the distribution and succession of these salt marshes and lead to the degradation of the red beaches. We examined how bottom‐up forces influenced the germination, emergence, and colonization of saline seepweed with field measurements and a laboratory experiment. We also examined whether top‐down forces affected the red beach distribution by conducting a field survey for crab burrows and density, laboratory feeding trials, and waterbird investigations. The higher sediment accretion rate induced by human activities limited the establishment of new red beaches. The construction of tourism facilities and the frequent presence of tourists reduced the density of waterbirds, which in turn increased the density of crabs, intensifying the top‐down forces such as predators and herbivores that drive the degradation of the coastal red beaches. Our results show that sediment accretion and plant–herbivory changes induced by human activities were likely the two primary ecological processes leading to the degradation of the red beaches. Human activities significantly shaped the abundance and distribution of the red beaches by altering both top‐down and bottom‐up ecological processes. Our findings can help us better understand the dynamics of salt marshes and have implications for the management and restoration of coastal wetlands

The crab Neohelice (=Chasmagnathus) granulata: An emergent animal model from emergent countries

Neohelice granulata (previously known as Chasmagnathus granulata and C. granulatus) is a burrowing semiterrestrial crab found in the intertidal zone of estuaries, salt marshes and mangroves of the South-western Atlantic Ocean. Beginning in the late 1989s, an explosion of publications appeared in international journals dealing with its ecology, physiology, toxicology and behavior. A bibliometric analysis using the Scopus database allowed detecting 309 papers that deal with this species during the period 1986–2009. The number of papers per year increased continuously, reaching a mean annual value of 22.6 during the last 5 years; a great majority of them were authored by researchers from Argentina and Brazil. Neohelice granulata has become now one of the most studied crab species, after Carcinus maenas, Callinectes sapidus, Scylla serrata and Cancer pagurus and C. magister, and it can be considered as an emergent animal model for biochemical, physiological and ecological research.Fil: Spivak, Eduardo Daniel. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Population structure of the grapsid crab, Helice tridens latimera (PARISI) in the Taiho mangrove, Okinawa, Japan

Grapsid crab Helice tridens latimera inhabiting mangroves, seashores as well as muddy and rocky areas. Ovigerous females were observed from December to May. Juveniles appeared in July and from December to April. In the laboratory they reached 9.50 mm in carapace width 4 months after hatching. It is likely that spawning of this crab occurs throughout the year

ON 15-TH SMARANDACHE'S PROBLEM

Studying the 15-th Smarandache's problem

Larval development of a semi terrestrial mangrove sesarmine crab Chasmagnathus convexus (Crustacea: Decapoda: Brachyura: Grapsidae) reared in laboratory

Four zoeal stages and one megalopal stage were identified in laboratory reared semiterrestrial mangrove sesarmine crab Chasmagnathus convexus. At an average salinity and temperature of 20±1% and 19.2±0.2°C, the megalopa was attained 24 days after hatching. Morphologically, the first zoae of C. convexz1s is very similar to those of other species of the genus Chasmagnathus as well as species of the genus Helice, in that view all share the following characteristics: lateral spine on the carapace, three pairs of setae on the posterior margin of the telson furca, one plus five setae on the endopod of the maxillule, and two plus two setae on the endopod of the maxilla. The differences between the first zoea and megalopa of and those of its congeners are discussed

The highly rearranged mitochondrial genomes of the crabs Maja crispata and Maja squinado (Majidae) and gene order evolution in Brachyura

Abstract We sequenced the mitochondrial genomes of the spider crabs Maja crispata and Maja squinado (Majidae, Brachyura). Both genomes contain the whole set of 37 genes characteristic of Bilaterian genomes, encoded on both \u3b1- and \u3b2-strands. Both species exhibit the same gene order, which is unique among known animal genomes. In particular, all the genes located on the \u3b2-strand form a single block. This gene order was analysed together with the other nine gene orders known for the Brachyura. Our study confirms that the most widespread gene order (BraGO) represents the plesiomorphic condition for Brachyura and was established at the onset of this clade. All other gene orders are the result of transformational pathways originating from BraGO. The different gene orders exhibit variable levels of genes rearrangements, which involve only tRNAs or all types of genes. Local homoplastic arrangements were identified, while complete gene orders remain unique and represent signatures that can have a diagnostic value. Brachyura appear to be a hot-spot of gene order diversity within the phylum Arthropoda. Our analysis, allowed to track, for the first time, the fully evolutionary pathways producing the Brachyuran gene orders. This goal was achieved by coupling sophisticated bioinformatic tools with phylogenetic analysis

El sistema compresor-turbina. Su cálculo y aplicaciones

En esta Memoria trataremos del sistema compresor-tuibina trabajando en el ciclo de Braylon, o> de combustión a presión constante con expansión hasta la presión inicial. El motor así formado se conoce generalmente con la denominación de «Turbina de gas»; aplicándose también este nombre a la turbina propiam'ente dicha del motor. Para evitar confusiones, hemos seguido las denominaciones consagradas con el uso, y ya prácticamente en vías de reconocimiento oficial. Designamos «turborreactores» u los motores de avión humados por una turbina de gas, en la que se aprovecha directamente la energía cinética residual de la turbina como choiro propulsor. Por «turbohélice» entendemos el sis'ema moto-propulsor formado por una turbina de gas en la que se aprovecha la energía residual de la turbina para el accionamiento de una hélice, puliendo ayudar también a la propulsión la energía cinética que aún resta después de la turbina. Aunque no muy de acuerdo con el nombre, designamos «motores de reacción» a todo aquel sistema moto-propulsor que se vale direclamen e de la energía cinélica de un chorro de gases procedente de la combustión para realizarla pi opulsión. Por la falta material de tiempo hemos tenido que tratar muy brevemente algunas cuestiones, a las que hubiéramos querido dedicar mayor espacio, como, por ejemplo, acontece con las vibraciones de los alabes en los com'presores y turbinas, problemas de regulación, incremen'adores de empuje y algunas "otras cuestiones. Por último, hemos de destacar el agradecimiento que debemos a algunos alumnos de 5.° curso de la Academia de Ingenieros Aeronáuticos, a quienes recientemente tuvimos el gusto de darles un curso en la Academia sobre Motores de reacción. Los señores Sácnz Insausti y Ramírez Gómez han extractado de nuestros apuntes la paríe correspondiente al estudio termodinámico de la turbina de gas (Capítulos III y IV), con inclusión de algunas aportaciones propias. Al señor Gómez Moreno se debe gran parte del Capítulo VI, y el señor Salas Larrazábal ha sido el verdadero autor y redactor de la parte que trata de los ciclos industriales de la turbina de gas

Importance of allochthonousmaterial in benthicmacrofaunalcommunityfunctioning in estuarinesaltmarshes

Allochthonous input provides important food and spatial resources for estuarinebenthic fauna. While it is known that autochthonous materials are important for fauna occupying small marshes, here, we present the significance of allochthonousmaterials for benthic fauna inhabiting a large saltmarsh. To assess the effects of allochthonous input on benthicmacrofaunalcommunities in estuarinesaltmarshes, we determined the source of substrate sediments and food resource utilisation patterns of benthic invertebrates in 2 temperate estuaries (the Tama River and the Obitsu River estuarine outlets into Tokyo Bay) by using stable carbon and nitrogen isotope analyses. In the Tama River estuary, which has small patches of marsh vegetation upstream of the river mouth, there was an input of sedimentary organic matter from autochthonous sources (i.e. common reed and microphytobenthos). In the Obitsu River estuary saltmarsh, which is situated immediately upstream of the river mouth and is well connected to the sea, sediment consists of allochthonous sources (i.e. imported phytoplankton), along with microphytobenthos. Isotope analysis indicated that most benthic invertebrates in the Tama River estuary depend on benthic microalgae (autochthonous) as a food resource, whereas the macrofauna in the Obitsu River estuary are supported by drift macroalgae (allochthonous), in addition to microphytobenthos or phytoplankton. Our results indicated that allochthonousmaterial provides a food resource and potential habitat for benthic macrofauna in extensive saltmarshes that have a strong connection to the sea but is not substantial in smaller marshes with limited connectivity to coastal water