Isolation and characterization of microsatellites in Pachygrapsus marmoratus (Grapsidae; Decapoda; Brachyura)

Seven polymorphic microsatellite loci were isolated and characterized from the grapsid crab Pachygrapsus marmoratus using FIASCO (fast isolation by AFLP of sequences containing repeats) protocol. Twenty‐seven primer pairs were designed, 14 of which worked well in polymerase chain reaction (PCR), amplifying a fragment of the expected size. Variability was tested in 18 specimens collected along the coast of Tuscany (Italy). Five loci were discarded due to stutter products during their amplification, and two resulted to be monomorphic. The remaining seven loci, showed a number of alleles ranging from two to 14 and an observed heterozygosity ranging from 0.12 to 0.67.     

Phylogeny of the shore crab family Grapsidae (Decapoda: Brachyura: Thoracotremata) based on a multilocus approach

The Grapsidae are a thoracotreme crab family with 40 species in eight genera (in their strict definition), and possess a number of morphological and molecular synapomorphies. Previous phylogenetic studies based on mitochondrial DNA markers established the monophyly of this family, but suggested possible paraphyly or polyphyly of some of the constituent genera. To test the validity of previous hypotheses, the present study reconstructed a molecular phylogeny of the grapsid crabs based on five molecular markers, including mitochondrial DNA markers and the first use of nuclear protein‐coding markers to address this issue. Monophyly of Grapsidae was confirmed, with the exception of the position of the monotypic genus Leptograpsodes. The polyphyly of the genus Pachygrapsus is consistent with previous molecular phylogenies, as members from this genus are dispersed throughout our gene tree. Grapsus and Planes were shown to be paraphyletic, with species of Pachygrapsus nested within them. Our study found incongruences between the currently adopted classification of the family, and hence taxonomic revisions will be needed. We hereby demonstrate the use of nuclear protein‐coding markers for high confidence reconstruction of decapod phylogenies, resolving most of the early splits that mitochondrial DNA markers alone are unable to tackle. © 2015 The Linnean Society of London     

Monsoon-dependent breeding in the field crab Paratelphusa hydrodromous (Herbst)

The reproductive cycle of the field crab Paratelphusa hydrodromous (Herbst) was determined by direct field observations as well as by calculating the percentage of ovigerous females in a Madras population for a period of three years. The females breed annually in a single spawning. These observations, corroborated by histological studies on the nature of the ovary, indicate that gametogenic activity starts in December and vitellogenesis is completed during January-May. Spawning commences in the last week of June or first week of July with the release of brood in the month of September (1979), October (1978) or November (1980) during northeast monsoon. The smallest female crab showing spawning had a carapace width of 3.1 cm and the largest spawning crabs measured 5.5 mm. The mean number of eggs spawned in the smallest crab was 247 and that in the largest crab was 417. Mean incubation was 41 ± 12.388 days. Vitellogenesis and spawning occurred at peak temperature conditions. Though the time taken for vitellogenesis and commencement of spawning were constant for the study period, the duration of retention of the juveniles in the brood varied with the onset of monsoon.     

Seasonal growth and reproduction in a highly fecund brachyuran crab, Metopograpsus messor (Forskal) (Grapsidae)

The annual cycle of a Metopograpsus population (Muzhupilangad estuary) had three distinct periods: (1) growth-reproduction (January–May), when crabs were involved in moult and reproduction; (2) inactive period (June–July), and (3) reproductive period (August–December). Usually, spawning was immediately followed by another vitellogenic cycle, paralleled by the embryogenesis of prehatch eggs in the brood. Moulting was seemingly an annual event. In the programming of moult and reproduction, the species deviated from the common brachyuran pattern, inasmuch as the postmoult females engaged in active vitellogenesis. The synchrony in the stages of maturation and spawning, and the precision with which the physiological events are programmed, make this highly fecund species an ideal model for an integrated study of the physiology of growth and reproduction.     

A microstructural study of the pleon‐holding mechanism in Carcinus maenas (Decapoda,Brachyura, Portunoidea,Carcinidae) of different sizes

Within the Brachyura there are a variety of specialized holding mechanisms, which facilitate the close attachment of the highly reduced pleon underneath the cephalothorax. The most common mechanism in eubrachyurans, known as the press‐button, consists of a sternal protrusion and a corresponding pleonal socket. Reports on the microstructural properties of the surface of these holding structures are scarce and patchy. In this study, the European Green Crab Carcinus maenas , is used as model to describe the microstructure of a typical press‐button mechanism with the use of scanning electron microscopy and light microscopic histology. A highly tuberculate cuticle and an apical ridge on the sternal knob are found in juveniles of both sexes. The microstructures are lost in adult males. In adult females, the holding structures themselves are reduced, but never completely lost. These findings show that C. maenas does not undergo a single “final puberty moult,” after which all juvenile characteristics are lost, as previously assumed. Further comparison of the morphology of juveniles to another species indicates a close resemblance of the holding structures at this stage. Therefore, the use of the microstructure of the pleon‐holding mechanism for phylogenetic analysis is restricted to adult specimens.     

Dynamic expressions of hypothalamic genes regulate seasonal breeding in a natural rodent population

Seasonal breeding is a universal reproductive strategy in many animals. Hypothalamic genes, especially type 2 and 3 iodothyronine deiodinases (Dio2/3), RFamide‐related peptide 3 (Rfrp‐3), kisspeptin (Kiss‐1) and gonadotropin‐releasing hormone (GnRH), are involved in a photoperiodic pathway that encodes seasonal signals from day length in many vertebrate species. However, the seasonal expression patterns of these genes in wild mammals are less studied. Here, we present a four‐year field investigation to reveal seasonal rhythm and age‐dependent reproductive activity in male Brandt's voles (Lasiopodomys brandtii) and to detect relationships among seasonal expression profiles of hypothalamic genes, testicular activity, age and annual day length. From breeding season (April) to nonbreeding season (October), adult male voles displayed a synchronous peak in gonadal activity with annual day length around summer solstice, which was jointly caused by age structure shifts and age‐dependent gonadal development patterns. Overwintered males maintained reproductive activity until late in the breeding season, whereas most newborn males terminated gonadal development completely, except for a minority of males born early in spring. Consistently, the synchronous and opposite expression profiles of Dio2/3 suggest their central function to decode photoperiodic signals and to predict the onset of the nonbreeding season. Moreover, changes in Dio2/3 signals may guide the actions of Kiss‐1 and Rfrp‐3 to regulate the age‐dependent divergence of reproductive strategy in wild Brandt's vole. Our results provide evidence on how hypothalamic photoperiod genes regulate seasonal breeding in a natural rodent population.     

Patterns of morphological and genetic variability in UK populations of the shore crab, Carcinus maenas Linnaeus, 1758 (Crustacea: Decapoda: Brachyura)

Previous research has identified extensive inter-population variability in the morphology of the shore crab (Carcinus maenas L.). To determine the source of this variation (genetic or environmental), morphological and genetic data were analysed from crabs collected from eight sites around the coast of the UK. Ten morphometric traits were measured from over 800 crabs and the degree of morphological similarity among sites was calculated using multivariate techniques. Allozyme electrophoresis was used to investigate patterns of genetic similarity. Extensive morphological variability was detected: eight out of the ten morphometric traits analysed were useful when discriminating between crabs from each site. Discriminant function analysis revealed that over 35% of individuals could be classified to their site of origin on the basis of their morphology. In contrast, the allozyme analysis revealed low levels of genetic variability, both within the meta-population and among the crab population at each site. Pairwise comparisons revealed a moderate correlation between the degree of morphological and genetic similarity of crabs at each site, which suggests that the observed phenotypic variability has a genetic component. However, only around 20% of the phenotypic variability detected was associated with the patterns of genetic similarity. This means that patterns of morphological variability in this species are largely determined by the local environmental conditions: local factors could have a within-generation selective influence on mean trait values or C. maenas may exhibit phenotypic plasticity.     

Histochemistry of the cuticle of the crab Menippe rumphii (Fabricius) (Crustacea: Brachyura) in relation to moulting

Histological and histochemical methods have been employed to study the formation and growth of the exoskeleton in relation to the moulting cycle of the crab Menippe rumphii (Fabricius). In the premoult condition the epidermal cells secrete a two-layered cuticle. Later these layers are widened by the secretions coming from the reserve cells, tegumental glands, and the Leydig cells. The fully formed cuticle of the intermoult crab is divisible into four layers, epicuticle, exocuticle, mesocuticle, and endocuticle.Histochemical observations on different cells have revealed that the tegumental glands secrete both neutral and acid mucopolysaccharides. The reserve cells are positive to PAS, BPB, Sudan Black B and Alizarin Red S techniques indicating the presence of carbohydrates, proteins, lipids, and mineral calcium. The Leydig cells are loaded with enzymes, including alkaline phosphatase, acid phosphatase, lipase, and phenoloxidase. Other histochemical tests have been employed to investigate the formation of different layers of the cuticle.     

Anti-predator responses of the intertidal crab Heterozius rotundifrons (Brachyura: Belliidae) in air and water

The intertidal crab Heterozius rotundifrons responds to tactile input, as occurs during a predation attempt, by hyper-extending all of its limbs and remaining in that posture for a variable length of time. We compared the duration of this anti-predator response: (1) in the day versus night (2) in two fluid media (air versus water) (3) after exposure to additional predator cues in one medium (air or water) and testing in the other medium (4) for crabs from different parts of the tidal range and (5) for females with and without eggs on their pleopods.?Crabs showed the posture at night as well as during the day. They also executed the posture when tested in air and extended the duration of the posture in air when they detected an additional predation-risk cue, shadows passing overhead. When crabs experienced input in one medium there was no effect on the duration of behavior shown in the other medium. Crabs from the lower portion of the intertidal showed a markedly longer duration of the limb-extended posture compared to crabs from the higher end of the tidal range of this crab. Berried females responded the same as females without eggs in both air and in water. Thus, crabs show this anti-predator behavior under a wide variety of conditions, but do not appear to transfer information received in one medium to behavior shown in the other media.     

Prevalence of bacteria in the spermathecae of female snow crab, Chionoecetes opilio (Brachyura: Majidae)

The spermathecal contents of primiparous, multiparous and barren female snow crabs were observed by a scanning electron microscope. Bacteria colonies were observed with a significantly higher frequency in the spermathecae of primiparous and old barren females. Bacteria infect the spermathecae and destroy the spermatophores and spermatozoa inside. These observations suggest that bacteria in the spermathecae do not exclude opportunistic microbes by modifying pH of the medium as suggested in the literature. The prevalence of bacteria in primiparous and old barren females suggests that they infect individuals with a weak anti-microbial protection. The absence of bacteria in the highly acidic seminal fluid derived from males upon copulation suggests that it may provide anti-microbial protection. Bacteria do not seem to be able to survive in an anaerobic environment for a long period.     

A molecular method for the detection of sally lightfoot crab larvae (Grapsus grapsus, Brachyura, Grapsidae) in plankton samples

The decapod Grapsus grapsus is commonly found on oceanic islands of the Pacific and Atlantic coasts of the Americas. In this study, a simple, quick and reliable method for detecting its larvae in plankton samples is described, which makes it ideal for large-scale studies of larval dispersal patterns in the species.     

Pharmacokinetic and metabolic study of itanoxone in the crab Pachygrapsus marmoratus (Decapoda, Brachyura): comparative study with clofibric acid

The LD50 of itanoxone injected i.v. in the crab Pachygrapsus marmoratus is 144 mg/kg. Hypolipidemic drug distribution is distinct according to organ and sex. The fixation power of muscle is comparatively low. Ovary radioactivity is higher than in the testicles. Itanoxone storage is large in the hepatopancreas. Metabolism, increasing over time, is not noticeably different according to sex. Two metabolites, chlorobiphenylcarboxylic acid and chlorobiphenylacetic acid, found in crab, are also identified in rat and man. The pharmacokinetic and metabolic study of itanoxone and clofibric acid in the crab shows a difference between the two drugs. Itanoxone metabolism and fixation is higher than clofibric acid.     

Seasonal variation in a low shore Fucus serratus (Fucales,Phaeophyta) population and its epiphytic fauna

Seasonal variation in a Fucus serratus assemblage was studied on the Isle of Man, UK over a 13-month period. Algal cover varied greatly, related to shedding reproductive fronds and winter storms. Peak reproduction was recorded in the autumn. There was little change in density of plants, the population was dominated by a bank of germlings (<20 cm) and an adult mode between 50–70 cm. An indistinct third component of recruiting juveniles was present when gaps in the canopy formed. Seasonal variation in the algae was reflected in the population dynamics of the mobile epiphytes such as Littorina mariae and Lacuna pallidula, which exhibited annual life histories. Sessile species (such as bryozoans) utilized the algae year round, dominating the perennial stipes and lower fronds, which were not shed. Other species utilized the algae in a transient fashion: some feeding on the algae (e.g. Idotea), or other epiphytic animals (e.g. Nucella). Fucus serratus, therefore, provides a variety of spatially and temporally variable niches that explain the diversity of epiphytic animal species that exploit this alga.     

印度加尔各答市区外围一地的露尾甲物种组成、多度和季节性发生(英文)

【目的】印度大部分露尾甲在腐烂的水果和蔬菜上大量发生,其种群在一年中表现出明显的季节性波动。据推测,露尾甲种群很大程度上依赖于温度、湿度和降雨之类的环境因子。【方法】本研究调查了2013-2015年印度加尔各答市区外围一地Garia的露尾甲物种组成、季节性发生和种群结构,记录了其活跃时期、季节性多度和影响其发生的因素。【结果】调查期间在调查地共发现数目不等的6个物种。其中最常见露尾甲为Urophorus humeralis,它是个体数量最多的物种且在一年中几乎所有月份均有发生;其他常见物种为Epuraea ocularis和E. luteola。不同物种在食物发酵的连续阶段进入诱捕器中。最初12 h被捕获的是Epuraea 属的种类,而在诱捕器中食物严重腐烂的后续阶段发现最多的是U. humeralis。在合适范围的气温(22~29℃)和相对湿度(82.5%~86%)下,物种丰富度最高,表明这些环境变量对露尾甲种群具有重要影响。【结论】加尔各答主要水果和蔬菜在季风后季节种植,在季风后季节取食这些作物的露尾甲发生量(物种丰富度和多度)最高。这一研究结果可能有助于制定针对这些甲虫的有效田间治理策略。     

Insights of the life history in the porcellanid crab Petrolisthes armatus (Gibbes, 1850) (Crustacea: Anomura: Porcellanidae) from the Southwestern Atlantic coast

Petrolisthes armatus (Gibbes, 1850) life history was evaluated based on growth and reproduction. Specimens were captured at Ubatuba (Brazil), identified, sexed and measured: carapace (CL, length; CW, width), larger cheliped propodus (PL, length; PW, width; and PH, height), and 2th and 5th abdominal somite (AW₂ and AW₅, width). Relative growth was studied using CL as independent variable and its relation with other variables (dependents), to estimate puberty size and morphological maturity. Fecundity was represented by number of eggs vs. body size CL, with a better fit using a power function. Considering the 257 specimens analyzed, males were larger than females, and the overall sex ratio was 1:1, with some differences among size classes. Maturity (puberty size) was revealed by: AW₂ × CL (males: 8.6 mm CL; females: 7.6 mm CL); and AW₅ × CL (7.1 and 7.6 mm CL, respectively). Reproduction was continuous, but more intense in rainy season and recruitment occurring in dry season. Fecundity of this species was 228 ± 163 eggs, with better fit by a power function (R² = 0.72). Maturity size and growth differed when a pristine area (Ubatuba) was compared with a polluted area (São Sebastião), in the same Brazilian area (São Paulo State).     

Population density,microhabitat use,and size characteristics of Pseudothelphusa dugesi,a threatened species of freshwater crab from Mexico (Brachyura: Pseudothelphusidae)

The brachyuran crab Pseudothelphusa dugesi, or cangrejito barranqueño, is an endangered species endemic to Cuernavaca, Morelos, in central Mexico. Individuals of P. dugesi inhabit freshwater springs, which are affected by human actions through wastewater drainage, eutrophication, exploitation, and invasive predators such as rainbow trout (Oncorhynchus mykiss). In this study, we evaluated the population density, microhabitat use, and size characteristics of P. dugesi. Sampling was conducted in May, July, and December of 2018 and March of 2019, during the dry and rainy seasons in a natural protected area, the Barranca de Chapultepec. Population density was 0.082 crabs/m², female density was 0.052 crabs/m², and male density was 0.112 crabs/m²; ovigerous females were not observed. Males were more abundant than females; the female: male ratio was 1:2.14. Males and females had similar carapace widths and lengths, left and right chelae lengths, and mass. Individuals of P. dugesi were found mostly under or between rocks and under leaf litter. Individuals were more active at night. An understanding of the biology and population characteristics of P. dugesi will help conservationists to develop protective measures and a conservation strategy for this endangered Mexican freshwater crab species.