The tendons of Ophiocomina nigra and their role in autotomy (Echinodermata,Ophiuroida)

Summary In the arm of the ophiuroid Ophiocomina nigra the intervertebral muscles are linked to the vertebral ossicles by tendinous connective tissue fibres. When an arm autotomizes, rupture of the tendons at one end (the autotomy insertion) permits each muscle in the autotomizing segment to separate cleanly from an ossicle while its other attachment (the non-autotomy insertion) remains intact. The anatomical relations, composition and function of the tendons were investigated by histochemical, electron microscopical and experimental methods. The tendons consist of a carbohydrate-rich secreted collagen derived from the basal lamina of the muscles. At autotomy their rupture is preceded and facilitated by an increase in extensibility, which represents the first evidence for variable tensility in an echinoderm connective tissue not composed of interstitial collagen. Granule-containing juxtaligamental cell processes are associated with the tendons of the autotomy insertions but are absent from the non-autotomy insertions. There appears to be widespread release of granules from these processes at autotomy. The results of a simple experiment implicate the juxtaligamental cells in the control of tendon extensibility and a possible mechanism for this control is presented.     

Tail regeneration following autotomy in the adult salamander Desmognathus fuscus

Tail regeneration occurs following autotomy of the tail in the salamander Desmognathus fuscus. Studies based on histology and autoradiography suggest that the cells of the regeneration blastema arise from the connective tissue of the tail stump. Following autotomy of the tail in Desmognathus the muscle of the regenerate is not derived from de differentiated or modulated striated muscle fibers of the autotomy stump. Possible sources of myogenic cells are discussed.     

Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy

Araújo, T.H., Faria, F.P., Katchburian, E. and Freymüller, E. (2009). Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy. —Acta Zoologica (Stockholm) 91 : 440–446. Although autotomy and subsequent regeneration of lizard tails has been extensively studied, there is little information available on ultrastructural changes that occur to the muscle fibers at the site of severance. Thus, in the present study, we examine the ultrastructure of the musculature of the remaining tail stump of the lizard Hemidactylus mabouia immediately after autotomy. Our results show that exposed portions of the skeletal muscle fibers of the stump that are unprotected by connective tissue bulge to produce large mushroom‐like protrusions. These exposed portions show abnormal structure but suffer no leakage of cytoplasmic contents. Many small and large vesicular structures appeared between myofibrils in the interface at this disarranged region (distal) and the other portion of the fibers that remain unchanged (proximal). These vesicles coalesce, creating a gap that leads to the release of the mushroom‐like protrusion. So, our results showed that after the macroscopic act of autotomy the muscular fibers release part of the sarcoplasm as if a second and microscopic set of autotomic events takes place immediately following the macroscopic act of autotomy. Presumably these changes pave the way for the formation of a blastema and the beginning of regeneration.     

Functional morphology and biomechanics of cuticular fracture at the elytrophoral autotomy plane of the scaleworm Alentia gelatinosa (Annelida: Polynoidae)

Abstract. Autotomy of the elytra (scales) in the annelid Alentia gelatinosa occurs at a breakage plane near the junction between the elytron and its elytrophore (stalk), and requires fracture of the external epidermal cuticle. The mechanism of cuticular fracture was investigated by light and electron microscopy, glycoconjugate histochemistry, direct observation of autotomy in isolated preparations, and mechanical tests. The breakage plane crosses the elytrophoral wall at a cuticular thickening and passes through the subelytral cavity between the elytron and the terminal septum of the elytrophore. At the cuticular breakage zone (CBZ), the collagenous framework of the normal cuticle is replaced with non‐collagenous microfibrils. The CBZ has a complex glycoconjugate composition and includes a strongly sulfated, uronic acid‐containing glycosaminoglycan and a high proportion of disulfide or sulfydryl linkages. Tonofilament‐rich epidermal cells (tendon cells) are attached to the thick cuticle on the dorsal and ventral sides of the CBZ. Dorsal tendon cells have long processes that extend into the elytron near the roof of the subelytral cavity. Ventral tendon cells are linked by connective tissue to the longitudinal and terminal sphincter muscles of the elytrophore. Mechanical tests showed that the elytrophoral wall is not inherently weaker at the autotomy plane than elsewhere. It is hypothesized that at autotomy (i) contractile force generated by the sphincter muscle is transmitted through elytrophoral tendon cells to the ventral side of the CBZ and (ii) contraction of the longitudinal and main circular muscles of the elytrophore increases hydrostatic pressure in its lumen, everts the terminal septum, and generates tension that is transmitted through elytral tendon cells to the dorsal side of the CBZ. This results in stress concentration at the basal edge of the CBZ and initiates fracture. The distinctive microstructure and macromolecular composition of the CBZ may reduce its fracture toughness and make it more susceptible to brittle failure.     

Chemical defense,biochemical composition and energy content of three shallow-water Antarctic gastropods

Summary Aqueous extracts of the mantle tissues of the opisthobranchs Austrodoris kerguelensis and Tritoniella belli and the lamellarid gastropod Marseniopsis mollis were cytotoxic to the sperm of the antarctic sea urchin Sterechinus neumayeri, and caused behavioral responses (sustained terminal sensory tube-feet retractions) in five species of antarctic sea stars. Pieces of mantle tissue of all three species were noxious to two species of antarctic fish. Primary body components (mantle, foot, viscera) of the three gastropod species contained high levels (% dry wt) of NaOH-insoluble protein (40–59%), moderate levels of NaOH-soluble protein (7–25%) and lipid (6–18%), and low levels of carbohydrate (< 1%). The energetic composition of the tissues reflected their organic make-up, with most energy (11–17 kJg^–1 dry wt) associated with protein. Total energy contents of representative adult individuals were 192,26 and 69 kJ for A. kerguelensis (93 g wet wt), T. belli (22 g wet wt) and M. mollis (114 g wet wt), respectively. Although these sluggish gastropods lack an external shell and are nutrient-and energy-rich and therefore high quality prey, like many of their temperate and tropical counterparts, they appear to be protected by chemicals.     

Autotomy of walking legs in the Pacific Shore crab Hemigrapsus oregonesis †

The ease of autotomy in Hemigrapsus oregonensis was tested by crushing the propodite of each walking leg. Individual curves of percent autotomy in groups of 18–21 animals were drawn for six different sequences of stimulation. Lumped data show peaks in ease of autotomy for the third anatomical leg of each side and for the second leg stimulated regardless of anatomical position. Later autotomies are more severely depressed when the stimulation sequence is from posterior to anterior. Segmental and lateral interaction and the characteristics of individual responses suggest that autotomy of legs in the crab, while depending upon specific structural features of the legs, is less a unisegmental reflex, than an accident occurring during escape.     

Identification of muramyl derivatives in mollusca gastropoda tissue

Summary Previous findings have demonstrated the presence of muramic acid and the lack of sialic acid in gastropod glycoconjugates from different tissues. The present study investigated the composition of muramyl derivatives in Mollusca Gastropoda tissue from the foot, mantle and periesophageal ganglia, using HRP-labeled lectins (LTA, UEA I, GSA IB₄, GSA II, DBA, SBA, RCA II, WGA, PNA, ConA) and glycosidase digestion (neuraminidase, lysozyme, -l-fucosidase, -N-acetylglucosaminidase, -N-acetylgalactosaminidase). Muramyl derivatives from the tissue examined showed some differences related to the composition of the terminal disaccharides. Indeed, foot and mantle mucocytes exhibited muramic acid in a terminal position, linked to (subterminal) N-acetylgalactosamine, whereas in neuron cells muramic acid was present in an internal position and linked to N-acetylglucosamine. Diversities also occurred between foot and mantle mucocytes with respect to the receptor sugar for penultimate N-acetylgalactosamine.     

Juxtaligamental system of the disc and oral frame of the ophiuroid Amphipholis kochii (Echinodermata: Ophiuroidea) and its role in autotomy

Abstract. The ophiuroid Amphipholis kochii is able to detach its central disc from the underlying oral frame in response to external stimuli. In this article we supply new observations on the microanatomy and ultrastructure of the autotomy plane, and of the juxtaligamental system which is believed to bring about connective tissue changes that underpin the detachment process. We correct previous confusion over the innervation of juxtaligamental nodes involved in disc autotomy, provide evidence that juxtaligamental cells are a population of specialized nerve cells, and present observations on changes in the ultrastructure of juxtaligamental cells during autotomy, which support the view that they are responsible for connective tissue disruption.     

Development of asymmetry in the caenogastropods Amphissa columbiana and Euspira lewisii

Abstract. The asymmetry displayed by the body plan of gastropods has been directly or indirectly attributed to an evolutionary process called torsion. Torsion is defined as a rotation of 180° between the cephalopodium (head and foot) and visceropallium (visceral organs, mantle, mantle cavity, and shell). During development, the displacement of anatomical components occurs during a process called "ontogenetic torsion." Although ontogenetic torsion is central to theories of gastropod evolution, surprisingly few studies have documented actual tissue movements during the development of asymmetry in gastropods. We investigated the development of the mantle cavity and pleurovisceral nerve connective (visceral nerve loop) in the caenogastropods Amphissa columbiana and Euspira lewisii , because displacements of both of these structures are interpreted as major consequences of torsion. Scanning electron micrographs, histological sections, and immunofluorescence images showed that the developing vis-ceropallium twists by 90° relative to the cephalopodium, the mantle cavity initially forms on the right side, and displacements of the visceral nerve loop become evident on the left side before the right side. A developmental stage in which the mantle cavity is confined to the right side has also been reported in members of the Vetigastropoda and Heterobranchia. We suggest that further comparative studies should test the hypothesis that early development throughout the Gastropoda converges on an embryonic organization in which the mantle cavity and anus are located laterally, despite clade-specific differences in developmental patterns both before and after this stage.     

Immunohistochemical Study of Leucine-Enkephalin and Delta Opioid Receptor in Mantles and Feet of the Octopus Octopus ocellatus Gray

The study was supposed to determine whether leucine-enkephalin (leu-Enk) or delta opioid receptor was presented in mantles and feet of the Octopus Octopus ocellatus. The results showed that they were found in the mantles, wrists, interbrachial membrane, and funnels of the Octopus Octopus ocellatus. The immunoreactivities of leu-Enk and delta opioid receptor were observed in the epithelial cells of dorsal mantle, wrist and interbrachial membrane. Strong one was presented in both the connective tissue which was close to the epithelium of dorsal mantle, wrist and interbrachial membrane and a small amount of connective tissue cells and nerve fibers, while less positive in other parts. A little of immunoreactive material was also observed in the ventral mantle and funnel, for example, weak one was in the epithelial tissue, the adjacent cells and nerve fibers. The different densities of leu-Enk and delta opioid receptor in mantles and feet of the Octopus O. ocellatus may be related to the different functions.     

Venom induces alarm behaviour in the social wasp Polybioides raphigastra (Hymenoptera: Vespidae): an investigation of alarm behaviour, venom volatiles and sting autotomy

Chemicals from the venom gland elicited alarm behaviour and attack in the Asian polistine wasp Polybioides raphigastra. When presented with crushed venom glands workers of this wasp respond with a mass stinging attack. Gas chromatography–mass spectrometry analyses show that the major volatiles in the venom gland are alkanes, monounsaturated alkenes and 2-alcohols. Several pyrazines, a spiroacetal and aromatics were also identified as trace compounds. The anatomy and morphology of the sting apparatus are reported, and we describe sting autotomy in this wasp. This is the first such report for the Ropalidiinae. The structures responsible for autotomy are likely to be large barbs present on the sting lancets, and a conspicuous tooth present on the medial side of the left lancet. Sting autotomy in P. raphigastra probably plays an important role in the localization of sites of attack by wasps defending the nest.     

Morphology and histology of the disc autotomy plane in Ophiophragmus filograneus (Echinodermata,Ophiurida)

Summary Normal and autotomized specimens of Ophiophragmus filograneus were studied by gross dissection, light microscopy, transmission electron microscopy, and scanning electron microscopy to determine how autotomy occurs at the major region of disc attachment. Each of the 10 genital bars is attached to an arm by a broad ligament consisting of a thick outer layer of collagenous connective tissue and an inner layer of neurosecretory cells innervated by a lateral ectoneural branch of the radial nerve. Neurosecretory cell processes extend into the collagenous layer. During autotomy the collagenous fibers separate, weakening the ligament near its insertion along the genital bar. Collagen fiber separation is probably caused by neurosecretions. There is no evidence for ossicle dissolution. The results indicate that the histological organization of the genital bar ligaments is identical to that of mutable collagenous tissues in other echinoderms and that the autotomy process is similar to that described for other echinoderms.     

Morphology of the pedal circulatory system of the marine gastropod Busycon contrarium and its role in locomotion (Gastropoda,Buccinacea)

Summary Dissections, injections, and histological preparations of the foot of Busycon contrarium show that the open circulatory system of the snail foot consists of discrete arteries and veins that anastomose throughout the foot in a pattern similar to the closed circulatory system of annelids and vertebrates. As the major arteries penetrate the foot, their diameter decreases and the thickness of their muscular walls diminishes. Near the ventral surface of the foot, the blood is channeled through the venous sinus, a fine network of discrete spaces delimited by the muscle and connective tissue of the sole. Small nuclei at the edges of some of these vessels indicate that they may have an incomplete endothelial lining. From the venous sinus, blood is channeled into two major veins on either side of the foot that join and return the blood to the kidney.While probably important for expanding the sole region and for maintaining turgor once the foot has expanded, the circulatory system is not isolated from the pedal musculature, but rather forms a continuum with the pedal muscles and the surrounding connective tissue. It is therefore unlikely that the blood functions as the mechanical antagonist to the muscular contractions of locomotion. The results indicate that the role of the pedal circulation in Busycon is intermediate between the fluids in the hydrostatic skeleton of many worm-like animals and the muscular-hydrostat of cephalopod arms and tentacles.     

Variation of life‐history parameters of Planococcus ficus (Hemiptera: Pseudococcidae) in response to grapevine nitrogen fertilization

The effects of different nitrogen fertilization regimes on body size and selected life‐history parameters (development time, survival, fecundity and fertility) of the vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), were investigated on potted grapevines under laboratory and screenhouse conditions. In both trials, five groups of four grapevines each were supplied with 0, 0.25, 0.5, 1.0 or 2.0 g/l of ammonium nitrate fertilizer for a month and then artificially infested with 200 first‐instar vine mealybugs (24 h of age). The concentration of nitrogen on grape leaves was measured during both experiments by a SPAD chlorophyll metre, showing statistical differences among treatments. The nitrogen fertilization significantly affected the investigated P. ficus parameters, providing consistent results in both laboratory and screenhouse trials. The vine mealybug females exhibited higher survival and fecundity, larger body size and lower development time on plants supplied with higher nitrogen fertilization rates. Survival, body size and fecundity of P. ficus were positively correlated with the leaf nitrogen concentration, whereas the development time was negatively correlated. Fertility did not vary significantly among treatments. Our results show that high nitrogen regimes increase the reproductive performance of P. ficus on grapevines and point out the importance of implementing balanced fertilization plans in grapevine IPM programs to reduce population densities and prevent insect outbreaks.     

Comparative studies on the nutrition of two species of abalone,Haliotis tuberculata Linnaeus and Haliotis discus hannai Ino I. Effects of algal diets on growth and biochemical composition

Summary

This study was conducted to examine the nutritional value of eight algal diets for two species of abalone, Haliotis tuberculata and Haliotis discus hannai, by measuring biochemical composition of the algae and relating this to feeding rate, growth and biochemical composition of the animals. Nutritional value of algal diets can be divided into three categories for each species of abalone. For H. tuberculata the best performance was on the mixed diet and Palmaria palmata intermediate was Alaria esculenta, Ulva lactuca and Laminaria digitata, and lowest growth was on Laminaria saccharina and Chondrus crispus. For H. discus hannai, best performance was on A. esculenta, P. palmata and the mixed diet; intermediate was on L. saccharina and L. digitata and lowest was on U. lactuca. It is generally accepted that high “balanced” levels of protein (>15%), lipid (3–5%) and carbohydrate (20–30%), with no detrimental substances in natural algae are essential for optimal growth performance of these abalone. The fact that A. esculenta, L. saccharina and U. lactuca had different dietary values for the two abalone species indicates specific nutritive requirements and/or digestive physiology. Overall, H. tuberculata grew faster, had higher food conversion efficiencies and muscle yield than H. discus hannai. Generally abalone fed on the highest category diets, had higher muscle yields and levels of protein, visceral lipids and muscle carbohydrate. Viscera and foot muscle are reservoirs for lipid and carbohydrate, respectively. The effect of algal diet on sexual maturation is similar to that on somatic growth.     

Insect-associated fungi from naturally mycosed vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Vine mealybug, Planococcus ficus, is a major pest of grapevine, which is present in at least 39 countries. According to American Vineyard Foundation, P. ficus is in the top ranks among major insect-pests of grapevine. It is the ‘top priority concerns’ by grape growers and a ‘threat to the sustainability of wine industry’ demanding a ‘high priority research’. In Douro vineyards, it is considered as an occasional insect-pest; however, its importance is increasing in some localities. The present study investigates the occurrences of P. ficus-associated fungi. Vine mealybugs were observed in two of the four surveyed farms. Out of the 183 collected mealybugs, 58 were dead of which 25 had symptoms of mycosis and 13 were parasitised. Subculturing cadavers and subsequent pathogenicity test yielded 22 entomopathogenic fungi (EPF) including yeasts. The yeast Meyerozyma (=Pichia) guilliermondii, and the EPF Sarocladium kiliense and Purpureocillium lilacinum were the most abundant, i.e. representing 18.18% (N?=?4), 13.64% (N?=?3) and 13.64% (N?=?3) of the isolates, respectively. Considering biological affinities, fungal families Nectriaceae and Microascaceae had the most similar count-data profiles. To our knowledge, this work reports the first isolations of EPF from vine mealybug worldwide; and Pseudocosmospora rogersonii in Europe and as EPF worldwide. The mortality rate originated by mycoses on P. ficus was significantly higher than by its parasitoids, suggesting that fungi as P. ficus biocontrol agents are relatively more important than considered before. Overall, this report provides new insights into the development of mycoinsecticides and conservation biocontrol strategies for P. ficus pest management.     

Ultrastructure of sea urchin tube feet

Summary An analysis of the ultrastructure of the tube feet of three species of sea urchins (Strongylocentrotus franciscanus, Arbacia lixula and Echinus esculentus) revealed that the smooth muscle, although known to be cholinoceptive, receives no motor innervation.The muscle fibers are attached to a double layer of circular and longitudinal connective tissue which surrounds the muscle layer and contains numerous bundles of collagen fibers. On its outside, the connective tissue cylinder is invested by a basal lamina of the outer epithelium to which numerous nerve terminals are attached. These are part of a nerve plexus which surrounds the connective tissue cylinder. The plexus itself is an extension of a longitudinal nerve that extends the whole length of the tube foot. It is composed of axons, but nerve cell bodies and synapses are conspicuously lacking, suggesting that the axons and terminals derive from cells of the radial nerve. Processes of the epithelial cells penetrate the nerve plexus and attach to the basal lamina. There is no evidence that the epithelial cells function as sensory cells.On the basis of supporting evidence it is suggested that the transmitter released by the nerve terminals diffuses to the muscle cells over a distance of several microns and in doing so affects the mechanical properties of the connective tissue.Supported by the Sonderforschungsbereich 138 of the Deutsche Forschungsgemeinschaft