Proprioceptors of the thoracic limbs of Squilla mantis (Crustacea,Stomatopoda)

Summary The distribution and morphology of the internal proprioceptive organs in the thoracic appendages of the stomatopod crustacean, Squilla mantis, are described. Five distinct types of proprioceptor are recognised; connective chordotonal organ, myochordotonal organ, cuticular stress detector, multiterminal stretch receptor and apodeme stretch receptor. The connective chordotonal organs and multiterminal receptors exhibit a wide variety of structural and functional complexity. The stomatopods resemble the decapods in that the basic proprioceptive unit of the thoracic appendages appears to be the connective chordotonal organ, but differs in the higher occurrence of multiterminal stretch receptors. As described for decapods, the pereiopods of stomatopods possess the largest number and greatest variety of proprioceptors, suggesting that locomotion exerts greater selective pressure on proprioceptor development than do the other thoracic limb functions, including the raptorial strike.     

Adaptive Mechanisms in the compound eye of Squilla mantis (Crustacea,Stomatopoda)

Summary Light and dark adaptations were studied in the eye of Squilla mantis. Light adaptation is characterized by (1) a proximal shift of the distal pigment sheath (DPS) surrounding the proximal portion of the crystalline cone above its zone of contact with the rhabdom; (2) flattening of the distal pigment sheath; (3) lengthening of the crystalline cone correlated with shortening of the rhabdom; (4) a migration of screening pigment granules in retinula cells in the protoplasmic bridges crossing the perirhabdomal space. In animals kept in constant darkness, longitudinal displacements of the distal pigment sheath were found to be subject to a circadian rhythm characterized by a maximal light adaptation state at about 5 p.m. and a minimal one at 5 a.m. Screening pigment granule translocation in retinula cells does not show such rhythmic activity.Abbreviations a, b maximal incidence angles in L.A., and D.A., respectively - Cc crystalline cone - Dps distal pigment sheath - I extreme incident light beam - Prs perirhabdomal space - Rh rhabdom - Rp reflecting pigment This research has been supported by grant 3.012-76 of the Swiss National Science Foundation     

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     

A model for the architecture of the hemocyanin from the arthropod Squilla mantis (Crustacea, Stomatopoda)

Squilla mantis hemocyanin is composed of two hexameric subunits but has electron microscopic profiles different from other bis-hexameric hemocyanins, e.g. Astacus and Homarus. We distinguished three different electron microscopic profiles of S. mantis hemocyanin: two sideviews and a topview. These profiles were studied using computer image alignment and correspondence analysis [Van Heel, M. and Frank, J. (1981) Ultramicroscopy 6, 187 - 194]. With the results of this analysis we were able to build a three-dimensional model for the quaternary structure of this hemocyanin. In this model the two hexamers are stacked in such a way that their hexagonal surfaces overlap to about 60% of their width. In the overlap area four subunits are arranged in two different interhexameric pairs, each forming a bridging area between the two hexamers.     

A comparison of the spermatozoa of OratosquiMa stephensoni and Squilla mantis (Crustacea, Stomatopoda) with comments on the phylogeny of the Malacostraca

Each stomatopod sperm, aflagellate and obovoid, is surrounded by an electron dense coat. A spermatophore is absent. The discus-shaped acrosome vesicle is penetrated and underlain by a straight, slender acrosome rod (perforatorium) ensheathed, below the vesicle, in subacrosomal material. Feulgen-positive granular material, indicating chromatin, fills most of the length of the cell but there is no certain nuclear membrane. Two centrioles, consisting of doublets each with a radial “foot” as in decapods and peracarids, occur near the acrosome and like it are embedded in the chromatin. Myelin-like membranes are associated with degenerating mitochondria in the posterior region of the cell. Thiéry-positive granules are aggregated as a glycogen body posteriorly in the cell. Spermatozoa1 ultrastructure confirms monophyly of the mysid–amphipod–isopod– cumacean section of the Peracarida but affinities of the tanaids are uncertain. A closer phylogenetic relationship of Phyllocarida to the Branchiopoda than to the Malacostraca is suggested. A weak similarity (synapomorphy?) of syncarids and peracarids is the filiform perforatorium bipassing the nucleus. Stomatopods resemble decapods in their diffuse sperm chromatin but are placed below the syncarid–peracarid–decapod assemblage.     

Système Sétifère des Maxillipèdes de Squilla mantis (Crustacea,Stomatopoda): Morphologie fonctionnelle

Résumé Les maxillipèdes de Squilla mantis comprennent 5 types fondamentaux de soies et un type de formation pseudosétale, représenté par des tubercules plissés sur les propodites des 5 maxillipèdes.Parmi les différents types de soies, 2 sont caractéristiques des Stomatopodes et 3 représentent des catégories sétales évolutives existant également dans d'autres groups de Crustacés.La distribution des soies montre que les premiers maxillipèdes, définis comme pattes nettoyeuses, sont les plus spécialisés dans la réception sensorielle (mécanique et chimique).

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Setal system of maxillipeds of Squilla mantis (Crustacea, Stomatopoda): Functional morphology

Summary There are 5 basic setal types in the maxillipeds of Squilla mantis (Stomatopoda) and 1 type of pseudosetal formation, represented by folded tubercles on the propodites of the 5 maxillipeds.Among these setal types, 2 are typical of Stomatopoda, and 3 represent evolutive setal categories also present in other groups of Crustacea.Their distribution shows that first maxillipeds, defined as grooming appendages, are the most specialized in sensorial reception (mechanical and chemical).

     

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.     

Synergistic and Antagonistic Effects of Thermal Shock,Air Exposure,and Fishing Capture on the Physiological Stress of Squilla mantis (Stomatopoda)

This study is aimed at assessing the effects of multiple stressors (thermal shock, fishing capture, and exposure to air) on the benthic stomatopod Squilla mantis, a burrowing crustacean quite widespread in the Mediterranean Sea. Laboratory analyses were carried out to explore the physiological impairment onset over time, based on emersion and thermal shocks, on farmed individuals. Parallel field-based studies were carried out to also investigate the role of fishing (i.e., otter trawling) in inducing physiological imbalance in different seasonal conditions. The dynamics of physiological recovery from physiological disruption were also studied. Physiological stress was assessed by analysing hemolymph metabolites (L-Lactate, D-glucose, ammonia, and H⁺), as well as glycogen concentration in muscle tissues. The experiments were carried out according to a factorial scheme considering the three factors (thermal shock, fishing capture, and exposure to air) at two fixed levels in order to explore possible synergistic, additive, or antagonistic effects among factors. Additive effects on physiological parameters were mainly detected when the three factors interacted together while synergistic effects were found as effect of the combination of two factors. This finding highlights that the physiological adaptive and maladaptive processes induced by the stressors result in a dynamic response that may encounter physiological limits when high stress levels are sustained. Thus, a further increase in the physiological parameters due to synergies cannot be reached. Moreover, when critical limits are encountered, mortality occurs and physiological parameters reflect the response of the last survivors. In the light of our mortality studies, thermal shock and exposure to air have the main effect on the survival of S. mantis only on trawled individuals, while lab-farmed individuals did not show any mortality during exposure to air until after 2 hours.     

Effect of morphine and naloxone on a defensive response of the mantis shrimp (Squilla mantis)

Summary The mantis shrimpSquilla mantis responds to an electrical shock with a quick and violent flexure of its body (Fig. 1 and 2). The reaction time of this defensive response was measured for each experimental shrimp and the minimal current that elicited a reaction time equal to or lesser than 0.22 s was considered as its intensity threshold (Fig. 3). Different doses of morphine-HCl were injected and results showed that this drug produces a dose-related analgesia by increasing the intensity threshold. A concentration of morphine equal to 30.0 g/mm of animal length (about 91.0 g/g) causes a 50% inhibition in the sensitivity to the electrical stimulus, but the effect is fully blocked by naloxone (Table 2).The present study represents the first behavioral analysis of opiate effects in invertebrates. However, the effective dose reported in this experiment is far greater than that used with vertebrates. Some speculative arguments are mentioned in order to account for a such large difference.     

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.     

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.     

Evolution of mantis shrimps (Stomatopoda,Malacostraca) in the light of new Mesozoic fossils

Background  

We describe new specimens of Mesozoic mantis shrimps (Stomatopoda, Malacostraca) that exhibit morphological and developmental information previously unknown.     

Contests with deadly weapons: telson sparring in mantis shrimp (Stomatopoda)

Mantis shrimp strike with extreme impact forces that are deadly to prey. They also strike conspecifics during territorial contests, yet theoretical and empirical findings in aggressive behaviour research suggest competitors should resolve conflicts using signals before escalating to dangerous combat. We tested how Neogonodactylus bredini uses two ritualized behaviours to resolve size-matched contests: meral spread visual displays and telson (tailplate) strikes. We predicted that (i) most contests would be resolved by meral spreads, (ii) meral spreads would reliably signal strike force and (iii) strike force would predict contest success. The results were unexpected for each prediction. Contests were not resolved by meral spreads, instead escalating to striking in 33 of 34 experiments. The size of meral spread components did not strongly correlate with strike force. Strike force did not predict contest success; instead, winners delivered more strikes. Size-matched N. bredini avoid deadly combat not by visual displays, but by ritualistically and repeatedly striking each other''s telsons until the loser retreats. We term this behaviour ‘telson sparring'', analogous to sparring in other weapon systems. We present an alternative framework for mantis shrimp contests in which the fight itself is the signal, serving as a non-lethal indicator of aggressive persistence or endurance.     

Different photoperiods affect proliferation of lymphocytes but not expression of cellular,humoral, or innate immunity in hamsters

In seasonal mammals, photoperiod change is associated with a suite of alterations in physiology. It has recently been proposed that the immune response is one of the systems regulated by changes in photoperiod, although this hypothesis has not been rigorously challenged by assays of functional immune responses. The aim of this study was to test the hypothesis that photoperiod modulates immune responsiveness in Syrian (Mesocricetus auratus) and Siberian (Phodopus sungorus) hamsters. Consistent with previously reported data, short-day-housed (SD) animals exhibited a significant increase in lymph node cell (LNC) numbers and increased cellular proliferation in response to the polyclonal mitogen concanavalin A compared to long-day-housed (LD) animals. In contrast, LNC numbers from intact or gonadectomized SD animals that had been sensitized with the antigen dinitrofluorobenzene (DNFB) exhibited a reduced ex vivo proliferative response and reduced production of interleukin-6 (IL-6) compared to LD animals. In vivo studies of the contact hypersensitivity response of animals that had previously been sensitized, and subsequently challenged, with DNFB were similar in SD and LD animals, as was the proliferative activity of LNC recovered from these animals. There were also no photoperiodic differences in the antidinitrophenyl antibody response of animals sensitized with DNFB, or the anti-sheep red blood cell (srbc) response of animals immunized with srbc. Furthermore, no differences could be detected in the activity of natural killer cells from spleens of LD and SD Siberian hamsters, or in lipopolysaccharide-induced IL-6 production by LD and SD Syrian hamsters in vivo. Thus, although photoperiod is able to influence factors regulating the gross number and non-antigen-specific proliferation of lymphocytes in seasonally breeding mammals, day length does not directly influence activation of an effective immune response. The authors conclude, therefore, that expression of the immune response is not directly modified or compromised by photoperiod in these seasonally breeding hamster species.     

Cellular and humoral aspects of innate immunity in the shark

Survival of many species depends, to a great extent, on their innate immunity. Innate immunity in the nurse shark (Ginglymostoma cirratum), a primitive elasmobranch, has been shown to consist of components, both humoral and cellular, which are in some respects similar to those found in mammals and other vertebrates. Innate immune factors present in the shark include complement (a complex system of serum proteins) and antibacterial proteins and enzymes, such as lysozyme. Shark complement, although opsonic and lytic in nature, differs from classical mammalian complement in the number of functionally distinct components involved in the activation sequence. Functional and structural analogues of several mammalian complement proteins have been isolated from the shark, and activation of shark serum by lipopolysaccharide or zymosan produces anaphylatoxin-like ligand(s) inducing mammalian smooth muscle contraction and chemotaxis of human leucocytes in vitro. Lysozyme activity has been recovered from shark leucocyte lysates, which also contain antibacterial peptides, distinct from lysozyme. The composition and antibacterial activity of shark leucocyte granules, the putative source of the activity, is under investigation. Cellular aspects of the inflammatory response which is an integral component of innate immunity, are leucocyte phagocytosis and chemotaxis. Both processes are functions of two distinct shark cell types, the granulocyte and the monocyte-macrophage. It should be noted that the innate resilience of the nurse shark is also augmented by a large pool of serum natural antibodies, which can account for as much as 45% of the total serum protein.     

Larval and early post-larval stages in the abbreviated development of Heterosquilla tricarinata (Claus, 1871) (Crustacea, Stomatopoda)

Heterosquilla tricarinata was laboratory-cultured through itscomplete larval development and found to have one propelagicand two pelagic larval stages prior to metamorphosis to thejuvenile. These larval stages, the first juvenile, and relevantportions of the second juvenile stage, are described and figured.Individual larvae do not change in size during intermoult periods.Larvae occurring in the plankton show a progressive decreasein mean size between early (September) and late (November) springtime.Reasons for this are suggested. The first pelagic stage of H.tricarinata is anatomically very advanced in development, andthe number of pelagic stages very few, in comparison with otherknown stomatopod life-histories. Ecological implications ofthis are discussed in relation to the high-latitude distributionof the species. Comparison is made between the final pelagicstage of H. tricarinata and that of its congenor H. brazieri. ^*Permanent address: Zoology Department, University of Queensland,Brisbane, Australia