The eye-movements of the mantis shrimp Odontodactylus scyllarus (Crustacea: Stomatopoda)

Summary Odontodactylus scyllarus makes discrete spontaneous eye-movements at a maximum rate of 3/s. These movements are unpredictable in direction and timing, and there is no detectable co-ordination between the two eyes. The eye-movements were measured with a computer-aided video method, and from 208 of these the following picture of a typical movement emerges. It has roughly equal horizontal and vertical components of 7–8°, taking the eye-stalk axis about 12° around a great circle, and also a rotational component of about 8°. The 3 components can occur independently of each other and are thus separately driven by the brain (Fig. 6). The average duration is 300 ms, and average velocity is 40° s (Fig. 5). Most movements are made in a direction approximately at right angles to the orientation of the specialised central band. It is shown that the slow speed of the eye-movements is compatible with scanning, that is, the uptake of visual information during the movement rather than its exclusion as in conventional saccades.Mantis shrimps also make target-acquiring and tracking eye-movements which tend to be somewhat larger and faster than other spontaneous movements. Rotating a striped drum around the animal induces a typical optokinetic nystagmus whose slow phases are smooth, unlike target tracking which is jerky (Fig. 7). Eye-movements may therefore be conveniently grouped into 3 classes: targetting/tracking, scanning, and optokinetic.     

Structure and mineralization of the spearing mantis shrimp (Stomatopoda; Lysiosquillina maculata) body and spike cuticles

Stomatopoda is a crustacean order including sophisticated predators called spearing and smashing mantis shrimps that are separated from the well-studied Eumalacotraca since the Devonian. The spearing mantis shrimp has developed a spiky dactyl capable of impaling fishes or crustaceans in a fraction of second. In this high velocity hunting technique, the spikes undergo an intense mechanical constraint to which their exoskeleton (or cuticle) has to be adapted. To better understand the spike cuticle internal architecture and composition, electron microscopy, X-ray microanalysis and Raman spectroscopy were used on the spikes of 7 individuals (collected in French Polynesia and Indonesia), but also on parts of the body cuticle that have less mechanical stress to bear. In the body cuticle, several specificities linked to the group were found, allowing to determine the basic structure from which the spike cuticle has evolved. Results also highlighted that the body cuticle of mantis shrimps could be a model close to the ancestral arthropod cuticle by the aspect of its biological layers (epi- and procuticle including exo- and endocuticle) as well as by the Ca-carbonate/phosphate mineral content of these layers. In contrast, the spike cuticle exhibits a deeply modified organization in four functional regions overprinted on the biological layers. Each of them has specific fibre arrangement or mineral content (fluorapatite, ACP or phosphate-rich Ca-carbonate) and is thought to assume specific mechanical roles, conferring appropriate properties on the entire spike. These results agree with an evolution of smashing mantis shrimps from primitive stabbing/spearing shrimps, and thus also allowed a better understanding of the structural modifications described in previous studies on the dactyl club of smashing mantis shrimps.     

Geographical distribution,dispersal and genetic divergence of the mantis shrimp Oratosquilla oratoria (Stomatopoda: Squillidae) in China Sea

The period of Cenozoic Himalayan orogeny was the developmental stage of the marginal seas and islands adjacent to the western Pacific. In the study, the molecular divergence dating between the northern and southern groups by fossil calibration was approximately 10.9 Myr, which was earlier than the time of the formation of Taiwan Island. Statistical-Dispersal Vicariance Analysis (S-DIVA) suggested that mantis shrimp of the China seas originated from two different ancestral regions (i.e., the Yellow Sea and South China Sea). However, the fluctuation of the Taiwan Strait in the late glacial period further influenced the phylogeographic structure of the mantis shrimp. In addition, the opposite ocean currents of the northern and southern seas of China, driving the planktonic larvae of marine species in opposite directions in the reproductive season, further accelerated their genetic divergence. In contrast, there were weak differences among the three northern seas due to their sharing one common ancestral region and then facing the dispersal event in the Cenozoic era and later sudden population expansion in the late Quaternary interglacial (54–75 ka). In conclusion, geological and climatic changes in past geological periods have greatly influenced the geographical distribution, dispersal and genetic divergence of the mantis shrimp.     

Ultrastructure of spermiogenesis and the distribution of spermatozoal nuclear histones in the Japanese mantis shrimp,Oratosquilla oratoria (Crustacea: Stomatopoda)

The Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda; Crustacea) is one of the most economically important aquatic species of Pacific shrimp and it is distributed from Japan to the coast of China, the Philippines, the Malay Peninsula, and the Hawaiian Islands. Early studies described certain characteristics of spermatogenesis and the sperm ultrastructure in Stomatopoda, but the composition of sperm basic nuclear proteins (SBNPs) remains completely unknown. We studied the sperm ultrastructure of O. oratoria using transmission electron microscopy and the histone composition using immunofluorescence and immunoelectron microscopy. We found that the spherical nucleus is adjacent to the electron translucent external coat, which occurs in early spermatids. The acrosomal structure begins to form at the junction of the nucleus and the external coat. At the mid-spermatid stage, part of the chromatin appears to be more electron-dense than the external coat side. The aflagellate sperm of O. oratoria, are rounded or slightly ovoid in shape and have a consistent granular nucleus, an acrosome structure of pushpin shape and a spherical vesicular body in which faintly granular material is scattered. The acrosome consists of an acrosomal vesicle, perforatorium, and subacrosomal material. The sperm contains histones H2A, H2B, H3, H4, H3.3, H2AX, and H2AZ as well as some histone modifications, that is, H3K9me3, H3K4me2, H3S10ph, H4Kac, and H2A + H4S1ph. Histones are localized not only in the nucleus of the sperm but also in other structures outside the nucleus. The results may provide new perspectives for systematic studies of crustaceans and their sperm chromatin components. These findings extend the study of the sperm structure of Stomatopoda and provide basic data to elucidate the epigenetic mechanism of fertilization.     

On display behaviour and courtship in the praying mantis Ephestiasula amoena (Bolivar)

Display behaviour in a small species of Indian praying mantis, Ephestiasula amoena , is described and the possible role of this display in courtship is discussed. The display involves exposure of the bright pattern on the inside face of the expanded plate-like profemora. The profemoral patterns found in closely related species are discussed and it is suggested that the display may also play a role in species recognition. The courtship behaviour of E. amoena is contrasted and compared with the courtship of other species of praying mantis.     

The use of different eye regions in the mantis shrimp Hemisquilla californiensis Stephenson, 1967 (Crustacea: Stomatopoda) for detecting objects

A behavioral assay was used to assess the ability of the stomatopod Hemisquilla californiensis to perceive and respond to a moving target under different wavelengths and intensities of light illumination. Subjects responded to targets rotating horizontally across their visual field by a brief startle response of their eyes or antennules but did not track the targets. Under white light responses were elicited down to a light intensity of 0.9 μW cm^− 2. Responses were seen in blue light at intensities as low as 0.5 μW cm^− 2, and in green light down to 1.0 μW cm^− 2. The animals were less sensitive to red light, with no responses seen at intensities below 3.0 μW cm^− 2. Subjects did not respond to the targets at all under infrared light. This response pattern mirrors the computed sensitivity spectrum of ommatidia in the species' peripheral hemispheres but not that in most of the central bands. We conclude that this species uses the monochromatic vision in the peripheral hemispheres of its eyes to recognize objects and that the sharply tuned color receptors of the central band serve to add supplemental information if light conditions allow.     

Deception with honest signals: signal residuals and signal function in snapping shrimp

Animals in competitive interactions often assess the competitiveability of opponents using signals. Signals used in competitiveinteractions are generally predicted to be honest, but opento low levels of deceit. Such "incomplete honesty" in signalscan be studied by using signal residuals, the residuals fromthe regression of a measure of signal structure on competitiveability. Specifically, individuals with positive signal residualsproduce signals that exaggerate their competitive ability; deceptive use of these signals may occur if signalers for whom the signalexaggerates their apparent competitive ability use the signalmore frequently. I used this framework to examine the use ofthe open chela display by big-clawed snapping shrimp (Alpheusheterochaelis). Competitive interactions between snapping shrimpare resolved primarily on the basis of body size, and the open chela display is used by males to assess body size. I foundthat the production of the open chela display by males respondingto superior competitors depends on chela residuals, such thatindividuals for whom the display exaggerates their apparentsize produce the display more often. This effect can be seenboth in response to isolated chelae and in staged competitiveinteractions. Interactions involving shrimp with larger chela residuals are long and highly escalated, suggesting that chelaresiduals affect assessment of competitive ability. Thus, theincreased use of the open chela display by males for whichthe display exaggerates apparent body size is an example ofdeceptive use of an otherwise honest signal.     

Evidence for hemocyanin formation in the compound eye of Squilla mantis (Crustacea,Stomatopoda)

Summary In the retina and in the subretinal space of the compound eye of Squilla mantis a special kind of pigment cell is present. The crystalline inclusions of this cell have been identified as hemocyanin, as determined (i) by the dimensional congruence of the crystalline substructure with the dimensions of isolated, purified hemocyanin, and (ii) by the immunofluorescence reaction using anti-hemicyanin antibodies. The ultrastructure of these cells, their location and the presence of crystalline bodies in their cytoplasm suggest that they are sites of hemocyanin synthesis and homologous to the cyanocytes or cyanoblasts of Limulus.Supported by grant No. 3,012-0.76 of the Swiss National Science Foundation     

Virus diseases of farmed shrimp in the Western Hemisphere (the Americas): a review

Penaeid shrimp aquaculture is an important industry in the Americas, and the industry is based almost entirely on the culture of the Pacific White Shrimp, Litopenaeus vannamei. Western Hemisphere shrimp farmers in 14 countries in 2004 produced more than 200,000 metric tons of shrimp, generated more than $2 billion in revenue, and employed more than 500,000 people. Disease has had a major impact on shrimp aquaculture in the Americas since it became a significant commercial entity in the 1970s. Diseases due to viruses, rickettsial-like bacteria, true bacteria, protozoa, and fungi have emerged as major diseases of farmed shrimp in the region. Many of the bacterial, fungal and protozoan caused diseases are managed using improved culture practices, routine sanitation, and the use of chemotherapeutics. However, the virus diseases have been far more problematic to manage and they have been responsible for the most costly epizootics. Examples include the Taura syndrome pandemic that began in 1991-1992 when the disease emerged in Ecuador, and the subsequent White Spot Disease pandemic that followed its introduction to Central America from Asia in 1999. Because of their socioeconomic significance to shrimp farming, seven of the nine crustacean diseases listed by the World Animal Organization (OIE) are virus diseases of shrimp. Of the seven virus diseases of penaeid shrimp, five are native to the Americas or have become enzootic following their introduction. The shrimp virus diseases in the Americas are increasingly being managed by exclusion using a combination of biosecurity and the practice of culturing domesticated specific pathogen-free (SPF) stocks or specific pathogen-resistant (SPR) stocks. Despite the significant challenges posed by disease, the shrimp farming industry of the Americas has responded to the challenges posed by disease and it has developed methods to manage its diseases and mature into a sustainable industry.     

Recombinant shrimp (Litopenaeus vannamei) trypsinogen production in Pichia pastoris

Shrimp (Litopenaeus vannamei) trypsinogen has never been isolated from its natural source. To assess the production of L. vannamei trypsinogen, we engineered Pichia pastoris strains and evaluated two culture approaches with three induction culture media, to produce recombinant shrimp trypsinogen for the first time. The trypsinogen II cDNA was fused to the signal sequence of the Saccharomyces cerevisiae alpha mating factor, placed under the control of the P. pastoris AOX1 promoter, and integrated into the genome of P. pastoris host strain GS115. Using standard culture conditions for heterologous gene induction of a GS115 strain in shake flasks, recombinant shrimp trypsinogen was not detected by SDS‐PAGE and Western blot analysis. Growth kinetics revealed a toxicity of recombinant shrimp trypsinogen or its activated form over the cell host. Thus, a different culture approach was tested for the induction step, involving the use of high cell density cultures, a higher frequency of methanol feeding (every 12 h), and a buffered minimal methanol medium supplemented with sorbitol or alanine; alanine supplemented medium was found to be more efficient. After 96 h of induction with alanine supplemented medium, a 29‐kDa band from the cell‐free culture medium was clearly observed by SDS‐PAGE, and confirmed by Western blot to be shrimp trypsinogen, at a concentration of 14 μg/mL. Our results demonstrate that high density cell cultures with alanine in the induction medium allow the production of recombinant shrimp trypsinogen using the P. pastoris expression system, because of improved cell viability and greater stability of the recombinant trypsinogen. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Photoreceptor projection and termination pattern in the lamina of gonodactyloid stomatopods (mantis shrimp)

The apposition compound eyes of gonodactyloid stomatopods are divided into a ventral and a dorsal hemisphere by six equatorial rows of enlarged ommatidia, the mid-band (MB). Whereas the hemispheres are specialized for spatial vision, the MB consists of four dorsal rows of ommatidia specialized for colour vision and two ventral rows specialized for polarization vision. The eight retinula cell axons (RCAs) from each ommatidium project retinotopically onto one corresponding lamina cartridge, so that the three retinal data streams (spatial, colour and polarization) remain anatomically separated. This study investigates whether the retinal specializations are reflected in differences in the RCA arrangement within the corresponding lamina cartridges. We have found that, in all three eye regions, the seven short visual fibres (svfs) formed by retinula cells 1–7 (R1–R7) terminate at two distinct lamina levels, geometrically separating the terminals of photoreceptors sensitive to either orthogonal e-vector directions or different wavelengths of light. This arrangement is required for the establishment of spectral and polarization opponency mechanisms. The long visual fibres (lvfs) of the eighth retinula cells (R8) pass through the lamina and project retinotopically to the distal medulla externa. Differences between the three eye regions exist in the packing of svf terminals and in the branching patterns of the lvfs within the lamina. We hypothesize that the R8 cells of MB rows 1–4 are incorporated into the colour vision system formed by R1–R7, whereas the R8 cells of MB rows 5 and 6 form a separate neural channel from R1 to R7 for polarization processing.This research was supported by the Swiss National Science Foundation (PBSKB-104268/1), the Australian Research Council (LP0214956) and the American Air Force (AOARD/AFOSR) (F62562-03-P-0227).     

Spermatozoa ultrastructure of the pink shrimp Farfantepenaeus paulensis (Decapoda: Dendrobranchiata)

Braga, A.L., Nakayama, C.L., Suita de Castro, L.A. and Wasielesky, W. 2011. Spermatozoa ultrastructure of the pink shrimp Farfantepenaeus paulensis (Decapoda: Dendrobranchiata). —Acta Zoologica (Stockholm) 00 : 1–6. The spermatozoa ultrastructure of the pink shrimp Farfantepenaeus paulensis was investigated in this morphological study. Spermatophores and spermatozoa were analyzed by electron microscopy. The pink shrimp spermatophore is divided into two regions: the appendage and the spermatophore main body, where spermatozoa are grouped in a spermatic mass. Pink shrimp spermatozoa are unistellate and are composed of main body and single spike. The spermatozoa body comprises a perinuclear cytoplasmic band, nucleus, acrosomal cap, and subacrosomal region. The spermatozoa cell mean total length was 10.71 μm, the mean body diameter was 5.56 μm, and the mean spike length and diameter were 5.15 μm and 0.85 μm, respectively.     

Cyst development in the conchostracan shrimp,Eulimnadia texana (Crustacea: Spinicaudata)

The fertilized egg (or cyst) of branchiopods is a highly resistant stage in the life cycle of these aquatic crustaceans. Previous examinations of these cysts have determined that early embryonic development arrests at a late blastula stage, resulting in a small, crescent-shaped body within the egg shell of these shrimp. Herein, we examine the early development of these embryos by sectioning eggs in the ovotestis, brood chamber, and several time periods after exit from the brood chamber in the clam shrimp Eulimnadia texana Packard. The early sections find no evidence of internal fertilization in the ovotestis. Eggs in the ovotestis showed no signs of cell division, whereas eggs sectioned from the brood chamber were found to be undergoing early embryonic development. A number of empty egg shells and the lack of unfertilized eggs in the brood chamber suggested that egg yolks quickly degrade after egg extrusion from the ovotestis. Cysts that were allowed to develop for 24, 48, 72, and 96 h, 1 week and 1.5 years were sectioned, and embryonic development did not change after the 48 h time period. Thus, embryos appear to arrest development somewhere between 24 and 48 h after exiting the brood chamber.     

Diversity in the weapons of sexual selection: horn evolution in the beetle genus Onthophagus (Coleoptera: Scarabaeidae)

Both ornaments and weapons of sexual selection frequently exhibit prolific interspecific diversity of form. Yet, most studies of this diversity have focused on ornaments involved with female mate choice, rather than on the weapons of male competition. With few exceptions, the mechanisms of divergence in weapon morphology remain largely unexplored. Here, we characterize the evolutionary radiation of one type of weapon: beetle horns. We use partial sequences from four nuclear and three mitochondrial genes to develop a phylogenetic hypothesis for a worldwide sample of 48 species from the dung beetle genus Onthophagus (Coleoptera: Scarabaeidae). We then use these data to test for multiple evolutionary origins of horns and to characterize the evolutionary radiation of horns. Although our limited sampling of one of the world's most species-rich genera almost certainly underestimates the number of evolutionary events, our phylogeny reveals prolific evolutionary lability of these exaggerated sexually selected weapons (more than 25 separate gains and losses of five different horn types). We discuss these results in the context of the natural history of these beetles and explore ways that sexual selection and ecology may have interacted to generate this extraordinary diversity of weapon morphology.     

宽网叶肢介属重要分类特征的发现

通过扫描电镜重新研究了产自俄罗斯维特奴河流域下三叠统维特奴宽网叶肢介(Loxomegaglypta wetlugiana Novo-jilov, 1958)的正模标本。扫描电镜成像揭示了光学照相无法分辨的重要分类学新特征, 其中包括: 生长带饰有圆形、角状或椭圆形小筛坑状装饰(直径15–25 μm), 筛坑被不同形状的隆起包围。均匀分布的针孔(直径4–6 μm)不但出现在筛坑里, 而且布满了筛坑周围的隆起。这种装饰与该属建立时描述的多角状大网格装饰区别较大。在此基础上,本研究修订了宽网叶肢介属生长带的装饰特征。     

Morphological study for understanding the sexual pattern in ghost shrimp Callichirus major (Crustacea: Axiidea)

Callichirus major is a species of ghost shrimp that has burrowing habits, building underground galleries in the intertidal region of beaches. This study aimed to analyse some morphological parameters to verify its type of sexual pattern. A sample of 79 individuals, collected at the beach of Corujão, Espírito Santo, Brazil, was used. Data on the external morphology, presence of gonopores, carapace length (CL) and cheliped lengths (Lch) were obtained. In addition, the gonads were processed for histological analysis. The animals were divided into three categories: A, individuals with male characteristics; B, those presenting exclusively female characteristics; C, animals with characteristics of intersex, which presented supernumerary gonopores. Positive allometries were found for Lch versus CL only for category A, characterizing the group's marked heterochely. Histologically, it was possible to observe the presence of oocytes in category A and one case of male tissue in an intersex individual (category C). However, no genital ducts of both sexes were found in that individual. Callichirus major presents controversial sexual characters, which makes it difficult to understand the reproductive parameters and sexual pattern. However, maybe that species can develop a sexual system of hermaphroditism.     

Isolation and characterization of 13 polymorphic microsatellite loci from the clam shrimp Eulimnadia texana (Crustacea: Spinicaudata)

Thirteen polymorphic microsatellite loci were isolated and characterized from the clam shrimp Eulimnadia texana. In analyses of 20–50 individuals from two populations the number of alleles ranged from two to seven with observed heterozygosity ranging between 0.00 and 0.37. The low values for heterozygosity were not unexpected for a group characterized by its unusual androdioecious mating system, in which males compete with self‐compatible hermaphrodites for offspring production. These microsatellites are likely to be useful for further evolutionary investigations of this rare mating system in these crustaceans.