Comparative study of the stomatogastric system of several decapod crustacea. I. Skeleton

The skeletal structure of the stomachs of several decapod Crustacea is described in detail. The general organization of the ossicles is similar for all species and the homologies of the elements can be recognized despite large variations from group to group. The Reptantia are characterized by a complex ossicle organization while the Natantia, on the other hand, are characterized by a simple organization. The various types of ossicle organization found in the decapod stomach can be arranged in a series ranging from simple to complex. The Brachyura have the most complex ossicle system and the Penaeidea the most simplified. This graded series of complexity closely follows the evolution of the Decapoda.     

Neuronal control of respiration in decapod crustacea.

Respiratory exchange in decapod crustacea requires the coordinated activity of the heart and the scaphognathites, appendages which ventilate the gills. There is common central nervous system neuronal modulation of both autogenically active systems as well as direct neuronal communication between both systems. The heart and scaphognathites also respond directly to oxygen tension. The neuronal control of the scaphognathites also respond directly to oxygen tension. The neuronal control of the scaphognathites is analyzed at several levels. Particular attention is directed toward the means by which the innately organized and stereotyped motor pattern for forward beating can be altered to produce reversed beating. The importance of sensory feedback in maintaining normal rates of scaphognathite beating is noted. And the phenomenon of bilateral coordination between the morphologically independent scaphognathites is described. Several different models of parts of the over-all scaphognathite neuronal circuitry are presented for heuristic purposes.     

Stress detection at the autotomy plane in the decapod crustacea

Summary The preformed autotomy plane of most reptantian decapods circumnavigates the basi-ischiopodite of the pereiopods. Associated with discrete areas of soft or thin cuticle in the proximity of the breakage plane are two connective chordotonal organs. These organs are sensitive to cuticular stress and are referred to as Cuticular Stress Detectors (CSD).The CSD organs respond to pressure applied to the basi-ischiopodite and upon deformation of the discrete areas of soft cuticle onto which the connective tissue strands of the receptors insert. The CSDs exhibit a wide range of unit activity and both receptors have a similar population of unit types. Some units are active only on application or removal of a force applied to the soft cuticle but a large number of phaso-tonic and tonic units respond to a constant pressure applied to the soft cuticle. The majority of the units respond during application of the stimulus (ON units) but a small proportion of the units increase activity on removal of the stimulus (OFF units).Passively produced tension in the anterior levator (autotomiser) muscle and depressor muscle tendons of the C-B joint is a potent stimulus to both receptors.Both receptors respond to movement of the B-I joint of the Nephropsidean walking leg and to movement of the I-M joint in the pereiopods of other reptantian decapods where the basipodite and ischiopodite have fused. The degree of activity is not directly related to the joint position or direction of movement.During autotomy both receptors respond strongly, particularly CSD 1. CSD 2 also shows increased activity but as the receptor is located distal to the breakage plane the receptor nerve is severed when breakage occurs.After autotomy CSD 1 responds normally to deformation of the soft cuticle but manipulation of the breakage plane membrane or of the regenerating limb bud produces low levels of activity even though the stimulus is gross.The possible functional roles of the receptors are discussed.This work was supported in part by European Science Exchange Programme study visit grants awarded to F. Clarac and W. Wales.     

On the biological function of the mandibular gland of decapod crustacea

Homogenates of the mandibular glands from the crayfish, Procambarus clarki, were injected into the freshwater shrimp, Caridina denticulata. These homogenates accelerated the moulting cycle of the shrimp, which strongly suggests that the mandibular glands of decapod crustaceans produce and secrete either moulting hormone(s) and thereby accelerate the moulting process, or produce a factor that activates the Y organs.     

The distribution and organization of CAP sensillae in decapod crustacea

The organization of peg‐like sensillae composing CAP organs is described for a number of representative decapod crustacea. In Natantian forms the sensillae are aligned in linear fashion on the distal side of the appropriate joints. One example, Pasiphaea, possesses a cluster of hair sensillae instead of pegs, possibly indicating the primitive origin of this organ system. In the Reptantia the Macrura have well‐developed groups of sensillae, arranged in broad fan‐shaped arrangements; the Anomura display rather varied plans of small sensillae, and in Porcellana only one group on maxilliped 3 are found. The Brachyura have no CAP organs. The significance of these findings, and their possible implication in the evolution of internal proprioceptors in the crustacea, is discussed.     

The stomatogastric nervous system of the house cricket Acheta domesticus L. II. Iontophoretic study of neuron anatomy

The anatomy of neurons of the stomatogastric nervous system of Ascheta domesticus was studied using heavy metal iontophoresis through cut nerve ends followed by silver intensification. Nineteen categories of neuron are described and compared with neurons known from the stomatogastric nervous system of other insects. Possible functions for the neurons are suggested. Motor neuron candidates are suggested for all parts of the gut served by the stomatogastric nervous system, and axons of sensory neurons of the anterior pharynx are located. There are four neuron types that cannot readily be assigned motor, sensory, or interneuron functions: large dorsal cells of the frontal ganglion; the two neurons of the nervus connectivus, and two categories of neurons in the median neurosecretory cell group of the pars intercerebralis, the axons of which are contained in the stomatogastric nerves.     

Allometry of gill dimensions in some British and American decapod crustacea

The gill areas and their component measurements of 16 species of North American crab and seven species of British decapod crustaceans have been analysed in relation to body mass using the method of logarithmic transformation.
A wide range of relationships was found, each of which is typical for a given species. The slope, b , of the log/log regression lines varied from 0·5 to 1·0, the lower values being most commonly found in the Macrura. For the North American species the average slope is about 0·8 whereas for British brachyurans the relationship was close to linear (b=0·97).
The analysis shows that the increase in gill surface body size is mainly due to the increasing area for individual platelets or gill lamellae.
Comparison of weight-specific gill areas for animals of the same body weight suggests that the most active species have larger gill areas. For some of these species the values (900mm²/g) approximate to those of active fish.
As plots for interspecific relationships derived from average values for many individual species have slopes which are not typical for any of the component species, it is concluded that caution must be exercized when interpreting such interspecific plots in Allometric studies.     

Cytochemical observations of hemocytes in decapod brachyuran crustacea (author's transl)]

Hemocytes from two species of crabs, Eriocheir sinensis and Carcinus maenas, have been submitted to different cytochemical reactions in order to bring out the nature of granules' content, either by specific coloration or be enzymatic digestion. Light as well as electron microscopy has been used. The granules appeared to be made essentially of basic proteins, rich in arginin and disulfide bridges but poor in tyrosin. These proteins are linked with nonglycogenic carbohydrates. Glycogen deposits of varied size are restricted to the cytoplasm in all the different cell-types but have never been detected inside the granules themselves. Lipids are poorly represented. The bulk of the granule material is made of neutral mucopolysaccharides although minute amounts of acid mucosubstances could be found in some instances.     

The ultrastructure of the oval organ a mechanoreceptor in the second maxilla of decapod crustacea

Summary The oval organ is a mechanoreceptor in the second maxilla. It has a rich dendritic arborisation, suspended in the haemocoele of the appendage by a cone of connective tissue. The apex of the cone is firmly inserted onto a small apodeme at the base of the endites, from which strands of collagenous connective tissue fan out to end in an oval area of arthrodial membrane. Three large sensory units, whose cell bodies lie centrally in the suboesophageal ganglion, enter the connective tissue cone and use its strands as a supportive framework for the primary and secondary dendrites. Thin tertiary dendrites end in clusters of bulbous terminals embedded within the epidermis of the arthrodial membrane.     

Ultrastructure of the testicular germinal zone and of the secondary spermatogonia in normal and destalked brachyuran decapod crustacea

Ultrastructural study of gonia of various species of male crabs shows that these cells belong to two types : primary and secondary gonia; these are discriminated according to their location inside or outside germinative islets, i. e. by the presence or absence of surrounding somatic tissue. The most original feature of the primary spermatogonia concerns the extrusion of gonial material under the shape of lamellar bodies or granules engulfed by the contiguous mesodermic cells; the latter degenerate when they are full of germ cell remnants. Poorly differentiated, the primary gonia have no great variety of cytoplasmic organelles. However two characteristic structures can be recognized in juxtanuclear position : nuage material (electron dense bodies more or less associated with gonia) and chromatoid bodies. Lipid droplets, the significance of which is unknown occur sometimes. Secondary spermatogonia divide synchronously although they are placed side by side without any connection such as cytoplasmic bridges. No ultrastructural modification has been noticed among the two types of gonia in crabs deprived of eyestalks. Mesodermic tissue distributed between primary gonia probably has a double role : inhibition of the onset of gametogenesis (as in Amphipods) and prevention of gonia cytolysis by collecting of altered elements.     

Individual distance in crustacea II. the mantis shrimp Gonodactylus oerstedii

The distances of separation at which individuals of the territorial shrimp Gonodactylus oerstedii showed agonistic behaviors were measured in the laboratory. Sizes of interacting animals had no effect on distances at which behavior patterns were shown. Different acts occurred at significantly different distances.

In the case of territorial G. oerstedii, most agonistic acts occurred just as an introduced animal crossed the gravel line marking the boundary of the territory. Actual distance separating animals was less important than location of an introduced shrimp in determining the probability of agonistic interactions.

Overall, there was an inverse correlation between degree of site attachment in a species and the variance in its behavior‐distance values.     

A comparative immunocytochemical investigation of the crustacean hyperglycemic hormone (CHH) in the eyestalks of some decapod crustacea

The eyestalk of the astacideans Orconects limosus, Nephrops norvegicus, and Homarus gammarus, and the palinuran Palinurus vulgaris, was examined with an antiserum raised against purified crustacean hyperglycemic hormone (CHH) of the astacidean species Astacus leptodactylus. A distinct immunopositive reaction occurs in a group of neurosecretory cells in the medulla terminalis ganglionic X-organ (MTGX), in the MTGX-sinus gland tractus, and in a considerable part of the sinus gland. The immunoreactive sites in the eyestalk of the investigated species correspond to the site of production, storage, and release of the CHH. Preliminary investigations with this antiserum also indicate that a positive immunoreaction can be obtained in the eyestalk of other decapod crustaceans, for example, of the brachyuran Macropipus puber and the caridean Palaemon serratus.     

Innervation of the limb accessory flexor muscle in several decapod crustaceans. II. Electrophysiology

The innervation of the distal and proximal heads of the accessory flexor muscle in three portunid crabs and two non-portunid decapods was studied electrophysiologically. In all species studied, the proximal head received only the two previously reported accessory flexor axons, an excitor and an inhibitor. The same two axons also innervated the distal head in all species, but in the portunids the distal head also received excitation from at least three, and probably sometimes four, of the main flexor excitor efferents. The accessory inhibitor exerted very strong effects in the tonic muscle fibers found in the proximal head and in the most proximal bundle of the distal head. The newly described inhibitory and excitatory distributions may have important implications for locomotory behavior.     

The anatomy and physiology of the stomatogastric nervous system ofSquilla

Summary The stomatogastric nervous system of a mantis shrimp,Squilla oratoria, is described. The motor nerves of the stomatogastric ganglion (STG) and their innervation of muscles of the posterior cardiac plate (pcp) and pyloric systems are detailed.The STG contains more than 25 neurons. It sends out one pair of major output nerves. The pcp-pyloric cycle recorded from the motor axons in this nerve consists of rhythmic bursts of several units which fire with a characteristic phase relationship to each other. The rhythm is intrinsic to the STG itself, but it is modifiable.Recordings from the peripheral nerves reveal that identifiable cardiac plate, pyloric dilator and pyloric neurons control sequential contractions of the pcp and pyloric muscles to constrict or dilate a number of their attached ossicles.Several modulatory input fibres in the stomatogastric nerve, activated via stimulation of the superior or inferior oesophageal nerve (son, ion), prime or trigger the cyclic motor outputs. The son inputs induce distinct effects on the cardiac and pcp-pyloric pattern generators, while the ion inputs, via the oesophageal ganglion, excite only the pcp-pyloric generator.On the basis of anatomical and physiological observations, the possible functions of motor neurons involved in the pcp-pyloric cycle are described with reference to opening of the pcp and pyloric channels.This stomatogastric nervous system inSquilla is compared to that in decapods which has been well analyzed.Abbreviations CG commissural ganglion - ion inferior oesophageal nerve - lvn lateral ventricular nerve - OG oesophageal ganglion - pep posterior cardiac plate - son superior oesophageal nerve - STG stomatogastric ganglion - stn stomatogastric nerve - ivn inferior ventricular nerve