The morphology and physiology of CAP organs in Jasus novaehollandiae (crustacea,decapoda, reptantia,macrura)

The location and external anatomy of the CAP organs of Jasus novaehollandiae were examined and found to be similar to those in Homarus gammarus (Laverack, 1978a). Histological examination of the organs showed threads or filaments arising from the internal surface of the spines to run through canals in the cuticle and join with dendrites of CAP sensory cells in the region of the hypodermis. The CAP neuron cell bodies lie in the nearby chordotonal organ strand. It is demonstrated that flexion of the limb causes the articulating membrane to deflect the spines of the sensillae distally. A variety of experimental techniques used to investigate the physiology of the organs reveals why previously reported attempts to record from the receptors failed. Direct stimulation of the sensillae with an analogue of the membrane and summation of many traces revealed phase constant responses at points corresponding to the covering and uncovering of the sensillae.     

The sensory innervation of the foregut of Panulirus argus (Decapoda Crustacea)† ‡

Ths structure of the stomatogastric neuromuscular system in Panulirus argus, Callinectes sapidus and Homarus americanus has recently been described (Maynard and Dando, 1973). We attempt here to describe the sensory innervation of the foregut in Panulirus argus and, by combining this information with previous published data and less systematic observations on Callinectes and Homarus, to provide in addition a summary of the stomatogastric sensory systems in these types of Decapoda Crustacea (Figure 1, Table I).

Some anatomical problems remain unresolved and there is variation in the structure of the sense organs in different species, but we are able to recognize six major receptor groups in all of the species examined. These are (i) mechanoreceptors which monitor movements of the lower oesophagus and mouth (Receptor reference Nos. 1, 2, 3); (ii) probable chemoreceptors in the higher oesophagus and ventral cardiac sac (Rf. Nos. 6, 9, 11); (iii) cells located in or near the stomatogastric ganglion which monitor movements of the gastric mill (Rf. No. 8); (iv) neurones of the posterior stomach nerve (Rf. No. 15) which monitor movements of the gastric mill; (v) neurones innervating muscles near the cardio‐pyloric valve (Rf. No. 16); (vi) neurones innervating the hepatopancreas duct and the initial part of the intestine (Rf. Nos. 18, 19).

In such a restricted system it should be possible to determine the precise role that the various sensory systems play in the control of the simple movements of the foregut. This research must necessarily involve the investigation, with intracellular techniques, of the central events in the commissural ganglia as these ganglia appear to be the major co‐ordination centres of the stomatogastric nervous system.     

Mg++-sensitivity of neuromuscular transmission in two crustaceans: Correlation with blood Mg++ levels

Neuromuscular transmission was measured in muscles of spider crabs (Hyasareneus) and lobsters (Homarus americanus). Solutions containing 40 and 10 mM/1 Mg⁺⁺, which were approximately the same as those measured in the blood of Hyas and Homarus, respectively, were used to soak the preparations prior to testing. In Homarus, neuromuscular transmission was severely depressed by 40 mM Mg⁺⁺. In spider crabs, neuromuscular transmission was not severely depressed. Although the amount of transmitter released by nerve impulses was reduced, total membrane depolarization during trains of impulses was not reduced because a compensating increase in muscle fiber membrane resistance occurred in Hyas preparations exposed to 40 mM Mg⁺⁺. Hyas, but not Homarus, is physiologically adapted to function at relatively high blood Mg⁺⁺ concentrations.     

Do the neurohormones VIH (vitellogenesis inhibiting hormone) and CHH (crustacean hyperglycemic hormone) of crustaceans have a common precursor? Immunolocalization of VIH and CHH in the X-organ sinus gland complex of the lobster,Homarus americanus

Summary

The present study deals with the location of the vitellogenesis inhibiting hormone (VIH)-producing cells in the eyestalk of the lobster Homarus americanus. In the present study, the neurosecretory pathways of VIH in Homarus, have been described immunocytochemically by use of a mouse serum against Homarus VIH. The location of the VIH cells was compared with the location of the crustacean hyperglycemic hormone (CHH) cells visualized by a rabbit serum raised against CHH of the crayfish Astacus leptodactylus. Immunocytochemical detection procedures, both at the light and electron microscopic level, revealed frequent but not complete co-localization of VIH and CHH in a variable number of the same group of perikarya. In the sinus gland, both neuropeptides were mostly demonstrated in distinct axonal endings characterized by different granule types. Postulations on the biosynthesis of these factors and suggestions concerning the processing of both neurohormones have been made.     

Microanatomy of the abdominal stretch receptors of the crayfish (Astacus fluviatilis L.)

Microanatomical studies on the abdominal stretch receptor organs of the crayfish Astacus fluviatilis L. have been carried out in order to establish a basis for the physiological work that has been, and is being carried out on stretch receptors of various species of crayfish. Important differences have been found between these organs and those previously described by Alexandrowicz for the lobsters Homarus vulgaris and Palinurus vulgaris. With the aid of silver-impregnated preparations the relationship of sensory endings and muscle fibers has been shown as well as the pattern of the efferent innervation. The physiological significance of the histological findings has been discussed.     

Ciliary receptors associated with the mouth and pharynx of Acoela (Acoelomorpha): a comparative ultrastructural study

The ultrastructure and distribution of receptor cells near the mouth and (where present) the pharynx of Hofstenia miamia, Proporus bermudensis, Conaperta thela, and Convoluta convoluta (Acoela) were investigated by transmission electron microscopy and confocal laser scanning microscopy of specimens stained with a fluorescence marker for actin. Five types of monociliary receptors were identified: (1) non‐collared receptors with a single long and narrow ciliary rootlet; (2) non‐collared receptors with a wide main ciliary rootlet and a smaller posterior rootlet; (3) non‐collared receptors with a single wide and hollow ciliary rootlet with a granulated core; (4) Collar (?) receptors with obliquely radial filament bundles in the cell apex and with a single hollow ciliary rootlet composed of numerous strand‐like elements; and (5) Collar receptors lacking a striated rootlet but with a granular body (swallow's nest rootlet). While H. miamia bears the first two receptor types, P. bermudensis has receptors of type 1, 3 and 5, and Cona. thela and Conv. convoluta have receptors of type 3, 4 and 5. The density of receptors is generally highest at the anterior body tip, regardless of where the mouth is located. Most receptor types occur scattered over the whole body but type 2 receptors of H. miamia are restricted to the pharynx and mouth region. The lack of a common receptor type specific for the mouth and pharynx of the investigated species points to an independent origin of the pharynges in Hofsteniidae and in Proporidae and of the mouth tube in Convolutidae. Moreover, the homology of the so‐called collar receptors in Acoela with typical collar receptors in other invertebrates is questioned.     

Die Entstehung fossilisationsfähiger Schalen-Fraßreste,dargestellt am Nahrungserwerb vonHomarus gammarus (Crustacea,Decapoda)

Zusammenfassung 1. Dem Beuteverhalten vonHomarus gammarus (L.) gegenüberMytilus edulis (L.), einem Lamellibranchiaten, sowie gegenüberBuccinum undatum L., dem im Biotop typisch vergesellschafteten Gastropoden, wurde anhand von Aquariums-Beobachtungen nachgegangen.2. Beide dieser Beute-Objekte aus dem weitgespannten Beutespektrum vonHomarus, zu dem Echinodermen, Crustaceen und eine Vielzahl anderer Benthonten des Litorals gehören, klären die Entstehung charakteristischer, fossilisationsfähiger Schalen-Fraßreste. Deren Morphologie wird dargestellt und ihre Entstehung besprochen.3. Im anpassungsfähig-plastischen Verhalten dieses und zahlreicher anderer Dekapoden bleiben darüber hinaus vielfältige morphologische Freiheitsgrade, die in der Ausgestaltung und Formgebung von Mollusken-Bruchscherben weitere Möglichkeiten offenlassen. Jedoch zeigt sich auch eine gewisse Einengung durch gemeinhin festliegende Reaktionsfolgen der überwiegend im Litoral beheimateten Dekapoden.

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The formation of shell feeding-fragments, capable of fossilization, demonstrated on the basis of food uptake inHomarus gammarus (Crustacea, Decapoda)

This paper deals with the complex behaviour ofHomarus gammarus attacking the pelecypodMytilus edulis and the gastropodBuccinum undatum; both molluscs inhabit the same nearshore environment asH. gammarus. The molluscs were chosen from a variety of prey animals ofH. gammarus in order to demonstrate formation of characteristic shell-fragments recognized by paleozoologists as traces of the meals of littoral decapods. Significant structural details of the shell-fragments are illustrated. Other shell-fragments produced by preying decapods, which often gnaw the hard shells after the meal, are not so easy to identify, although the behaviour patterns of littoral decapod crustaceans are generally quite similar.

     

Observations on the feeding mechanism,structure of the gut,and digestive physiology of the european lobster Homarus gammarus (L.) (Decapoda: Nephropidae)

Investigations have been made on the feeding mechanism, structure of the gut, and digestive physiology of the European lobster Homarus gammarus (L.).Ciné-photography has shown that the mandibles do not possess a masticatory function, merely serving to grip food morsels during the tearing process effected by the pulling action of the third maxillipeds. The remaining maxillipeds, together with the maxillae, then direct food fragments to the mouth for ingestion.Ingestion is facilitated by mucoid secretions discharged from the oesophageal tegumental glands; the glands do not appear to produce any enzymes which directly contribute to the digestive processes.The hepatopancreas is the principal organ concerned with digestion. It possesses a complex tubular organization in which sequential cellular differentiation culminates in the discharge of enzymes from the B-cells for extracellular digestion in the cardiac stomach. The enzymes are synthesized within vacuoles contained in the B-cell precursors (F-cells) and are secreted in three bursts of activity at 0–15 min, 1–2 h, and 3.5–5 h after a meal. The initial secretory phase is holocrine. Extracellular digestion involves esterases, arylamidases, and lipases; endopeptidases have not been positively identified by histochemical means despite the fact that Homarus is a carnivore. There is an intracellular digestive phase, not previously described in decapod crustaceans, at the 7–9 h post-ingestive stage in the hepatopancreatic R-cells which is effected by arylamidases and lipases.Various phosphatase enzymes have been identified in the hepatopancreatic cells. Acid and alkaline phosphatases are apparently concerned with several stages in the digestive cycle, including enzyme synthesis and secretion, and the absorption of digestive products. Adenosine triphosphatase activity is primarily associated with granules located in the distal R-cell cytoplasm; the possible significance of these granules in the elimination of metabolic wastes is discussed. Acid phosphatases and esterases are present in the midgut epithelium. The possibility of a passive uptake of material from the midgut lumen is considered.Faecal material in the hindgut is bound by mucoid secretions derived from the tegumental glands of this alimentary region; the mucus may also assist in defaecation.A complete digestive cycle in Homarus occupies ≈ 12 h.Food reserves in the gut consist principally of fat deposits in the R-cells, but minute amounts of glycogen can also be detected.No evidence of calcium, copper or ferric iron deposition in any part of the alimentary tract was found.     

An electromagnetic tracking system for studying the movements of rock (spiny) lobsters

A simple and inexpensive method for examining the movements of rock (spiny) lobsters is described. Electromagnetic tags emitting a pulsed signal were detected in loop antennae placed on the bottom in a grid pattern within a shallow coastal reef area. Signals were received in a tuned receiver and then interpreted using an oscilloscope. Results showing examples of the nocturnal movements of Panuliruscygnus George the western rock lobster in Western Australia are presented.     

The structure and function of the labrum in the lobster Homarus gammarus (L.).

The labrum of decapod crustaceans is a soft lobe overhanging the mouth. The labral skeleton, musculature and innervation of Homarus gammarus are described. There are three bilateral groups of sensory neurons innervating the floor, lobe and lateral walls of the labrum. These are probably responsible for the phasic afferent activity that can be recorded from the inner labral nerve on mechanical deformation of the labrum. The labrum undergoes rhythmical retraction-protraction movements during ingestion and is shown to be active during both mandibular activity and oesophageal peristalsis. Studies were made on the duration and frequency of labral "swallowing" activity. The role of the labrum in feeding is discussed.     

Distribution and at‐sea behavior of Bermudan White‐tailed Tropicbirds (Phaethon lepturus catesbyi) during the non‐breeding season

The movements and behavior of many taxa of seabirds during the non‐breeding season remain poorly known. For example, although studies conducted in the Pacific and Indian oceans suggest that White‐tailed Tropicbirds (Phaethon lepturus) seldom fly more than a few thousand kilometers from nest colonies after breeding, little is known about the post‐breeding movements and behavior of a subspecies of White‐tailed Tropicbirds (P. l. catesbyi) that breeds on islands in the North Atlantic Ocean. Our objective, therefore, was to use light‐based geolocators to identify the ranges and pelagic activities of White‐tailed Tropicbirds from Bermuda during the non‐breeding periods in 2014–2015 (N = 25) and 2015–2016 (N = 16). Locations were estimated based on changes in light intensity across time, and pelagic activities were determined based on whether geolocators attached to leg bands were wet (i.e., birds resting on the water's surface) or dry (i.e., birds in flight). In 2014, birds spent late summer (July–September) near Bermuda and the British Virgin Islands; by mid‐September, most (N = 17; 68%) birds took a direct easterly route to the Sargasso Sea. In 2015, most post‐breeders (N = 15; 94%) flew east from Bermuda and to the Sargasso before the end of late summer. For both years combined, fall and winter (October–February) ranges extended as far west as North Carolina and as far east as the mid‐Atlantic Ridge. In both years, all birds were located between Bermuda and the British Virgin Islands during the spring (April–May). All birds then flew north to Bermuda in both years, with variations in timing, during April and May. We also found extensive overlap in the ranges of males and females during the non‐breeding season in both years. During the non‐breeding season, White‐tailed Tropicbirds spent 5% of night periods and 41% of day periods in flight in 2014; in 2015, birds spent 8% and 42% of night and day periods, respectively, in flight. Tropicbirds spent more time flying during the day because they hunt by day, detecting prey on the wing by sight. Overall, our results suggest that White‐tailed Tropicbirds that breed in Bermuda are diurnal, nomadic wanderers that range over an extensive area of the Atlantic Ocean during the non‐breeding season.     

Differences in life-history and ecological traits between co-occurring Panulirus spiny lobsters (Decapoda,Palinuridae)

Coexistence of closely related species may be promoted by niche differentiation or result from interspecific trade-offs in life history and ecological traits that influence relative fitness differences and contribute to competitive inequalities. Although insufficient to prove coexistence, trait comparisons provide a first step to identify functional differences between co-occurring congeneric species in relation to mechanisms of coexistence. Here, a comparative review on life history and ecological traits is presented for two pairs of co-occurring species of spiny lobsters in the genus Panulirus: Panulirus gracilis and Panulirus inflatus from the Eastern Central Pacific region, and Panulirus argus and Panulirus guttatus from the Caribbean region. Panulirus gracilis and Panulirus inflatus have similar larval, postlarval, and adult sizes and a similar diet, but differ in degree of habitat specialization, fecundity, and growth rate. However, little is known on behavioral traits of these two species that may influence their competitive abilities and susceptibility to predators. The more abundant information on Panulirus argus and Panulirus guttatus shows that these two species differ more broadly in degree of habitat specialization, larval, postlarval and adult sizes, diet, fecundity, growth rate, degree of sociality, defense mechanisms, susceptibility to predators, and chemical ecology, suggesting a greater degree of niche differentiation between Panulirus argus and Panulirus guttatus than between Panulirus gracilis and Panulirus inflatus. Whether the substantial niche differentiation and apparent interspecific trade-offs between Panulirus argus and Panulirus guttatus relative to Panulirus gracilis and Panulirus inflatus reflect an earlier divergence of the former pair of species in the evolution of the genus constitutes an intriguing hypothesis. However, whether or not post-divergence evolution of each species pair occurred in sympatry remains uncertain.     

Comparative studies of crustacean spectral sensitivity

Summary Spectral sensitivity of the lateral eyes of the isopodPorcellio scaber (wood louse) and the decapodsCallinectes sapidus (blue crab),Palaemonetes paludosus (Everglades prawn),Orconectes virilis, andO. immunis (crayfish) have been measured between 300 and 660 nm by determining the reciprocal number of photons required to evoke a constant size retinal action potential. Porcellio is maximally sensitive at 515 nm andCallinectes at 505 nm. Both species have a single pigment system, as spectral sensitivity is unchanged by red light adaptation. Palaemonetes appears to have a dichromatic color vision. Sensitivity of the dark-adapted eye is dominated by a receptor maximally sensitive at 550–555 nm, but red or yellow adaptation discloses a uv pigment with _max at about 380 nm. Present evidence suggests the 555 and 380 nm pigments are located in different receptor cells. Orconectes has peak sensitivity at 565 nm, but under red light adaptation and close to the electroretinographic threshold a second sensitivity maximum appears at 425 nm. As in the prawn, these peaks seem to indicate the presence of a two-receptor color vision system.The corneas ofOrconectes, Callinectes, andHomarus (lobster) are relatively thick, and microspectrophotometric measurements show near ultraviolet absorption as well as the protein peak at 280 nm. By contrast,Palaemonetes andMusca (housefly), species with near ultraviolet receptors, have thinner corneas which are transparent through the near ultraviolet. The crystalline cone ofPalaemonetes likewise shows no near ultraviolet absorption but a strong protein band at 280 nm.The scarcity of ultraviolet receptors in the compound eyes of crustacea, in contrast to their common occurrence in insects, is thought to be related to the relative absence of ultraviolet wavelengths in most aquatic environments.This work was supported in part by USPHS research grant NB 03333 to Yale University and postdoctoral fellowship NB 22,547 to H.R.F.     

The mandibular muscle receptor organ of Homarus gammarus (L.) (crustacea,decapoda)

Summary A muscle receptor organ is present in the mandible of macruran decapods. The mandibular muscle receptor organ (Mand. MRO) of Homarus gammarus (L.) consists of a ribbon of muscle innervated at its ventral insertion by 10–20 multiterminal sensory neurones. The sensory cells have a small number of dendritic processes.The receptor muscle exhibits some structural properties of both fast and slow muscle. The mean sarcomere length is similar to that of the slow abdominal MRO but the receptor muscle in cross section has a punctate distribution of myofibril bundles more typical of fast muscle.This work was supported by Science Research Council grants B/SR/1871 and BR/G/585.     

The facial musculature of the Suoidea

The facial musculature and rhinarial anatomy of a tayassuid, Dicotyles, and four suids, Sus, Hylochoerus, Phacochoerus and Babirussa, are described. Differences found include the lack of m. zygomaticus in Hylochoerus and Phacochoerus and several modifications of the rostral muscles, mm. levator rostri, dilator naris, and depressor rostri. These differences are related to behavioral characteristics of the animals, particularly the occurrence of toothbaring and rhinarial mobility. The missing m. zygomaticus and relatively small mouth of Hylochoerus and Phacochoerus are probably associated with behavioral patterns which do not necessitate a large gape. In these genera the canines are exposed even when the mouth is closed. The development of the rostral musculature is correlated with movements of the rhinarium. Similarly, the distribution of terminal tendons depends on the shape of the nostril. In Hylochoerus and Phacochoerus, mobility of the rhinarium, especially the dorsal part, is less than in other suoids because of the firmer attachment of the rostral bone to the skull and the weaker development of the rostral muscles.     

Innervation of the receptors present at the various joints of the pereiopods and third maxilliped of Homarus gammarus (L.) and other macruran decapods (crustacea)

Summary This paper gives a full account of the number and structure of the chordotonal organs present at all joints between the coxopodite and dactylopodite of the pereiopods and 3rd maxilliped of the macruran Homarus gammarus L. (H. vulgaris M. Ed.). Some comparative data is supplied for other macruran decapods. As the form of the receptors depends to some degree upon the structure of the joint we have included details of musculature, planes of movement and degrees of freedom at each of the joints.The third maxilliped has a smaller number of chordotonal organs than the pereiopod, in particular at the mero-carpopodite and carpopodite-propodite joints where only one organ is present. In some species the propodite-dactylopodite organ is absent from this limb.The electrical activity recordable from the receptors in the 3rd maxilliped shows considerable differences from the corresponding receptors in the pereiopod.The structure of the carpopodite-propodite joint of both limbs is discussed in detail as this joint differs greatly from that of the Brachyura. In the 3rd maxilliped and 2nd pereiopod three muscles are present. In the latter the joint is capable of rotation about the longitudinal axis but the third muscle does not appear to produce this rotation. A small number of units in the CP₂ receptor respond to rotation.A receptor is described in the basipodite of the pereiopod and 3rd maxilliped situated just proximal to the plane through which the limb breaks at autotomy or autospasy. This receptor does not monitor joint movement and may detect cuticular strain, thus preventing accidental autotomy of limbs. A similar receptor has been observed in Carcinus.Cuticular receptor structures (CAP organs) are described as present at the M-C and C-P joints in both limbs, and at the I-M joint of the pereiopod.     

The control of hindgut motility in the lobster,Homarus gammarus (L.)

1. The sixth abdominal ganglion (6 A.G.) of the lobster Homarus gammarus (L.) innervates the rectum via the paired posterior intestinal nerves (P.I.N.’s) and the paired anal nerves. The anterior branches of the P.I.N.’s supply the anterior hindgut, the main faecal expulsion region, whilst the posterior branches (P.I.N.p.’s) supply the posterior region and the 5 extrinsic radial muscle groups around the anus.

2. Stimulation of the ventral nerve cord (V.N.C.) or the oesophageal connectives initiates co‐ordinated hindgut movements, the defaecatory response. The nervous activity eliciting these movements passes down the P.I.N.’s. The anal nerves are devoid of motor function with respect to the hindgut.

3. In addition to neurogenic movements the rectum also undergoes non‐coordinated, low amplitude longitudinal and circular muscle contractions. These are thought to be due to independently acting endogenous oscillators within the muscles themselves. The radial muscles of the anus also exhibit rhythmical contractions after an initial maximal contraction following stimulation of the P.I.N.p.’s.

4. Receptors responding to anal dilation and closure have been shown to exist in the anal nerves. They are non‐specific soft cuticle receptors which are, apparently, positionally sensitive. These receptors are not thought to modulate motor output from the 6 A.G. to the rectum at the level of the 6 A.G.

5. Bifurcating motor axons are thought to exist in the P.I.N.’s.

6. It is concluded that the defaecatory response of the lobster is a centrally programmed phenomenon.     

The neurobiology of dopamine receptors: evolution from the dual concept to heterodimer complexes

Context: G protein-coupled receptors (GPCRs) have been classically thought to work as monomeric entities. The current view of their organization, however, assumes that they are part of highly organized molecular complexes, where different receptors and interacting proteins are clustered. These heteromers have peculiar pharmacological, signaling, and trafficking properties. GPCR heteromerization, raising different combinatorial possibilities, thus underlies an unexpected level of diversity within this receptor family.

Methods: In this paper, we summarize recent data, reported by different research groups, suggesting that the dopamine (DA) D1 receptor forms heteromers with receptors of the same family and with structurally and functionally divergent receptors.

Results and discussion: DA D1 and D3 receptors and glutamate NMDA receptors regulate rewarding mechanisms and motivated behavior, modulate emotional and cognitive processes and regulate locomotor activity by extensive cross-talk mechanisms. Co-localization of D1 and D3 receptors and D1 and NMDA receptors in specific neuronal populations in the striatum and nucleus accumbens, moreover, suggested that their cross-talk may involve direct interactions. By using different experimental approaches various groups have, in fact, demonstrated the existence of D1-NMDA and D1-D3 heteromers, in both transfected cell systems and in the straitum, with peculiar pharmacological, signaling, and functional properties. The putative role of the D1-D3 and D1-NMDA heteromers in the physiological regulation of striatal function and in the development of motor dysfunctions will be discussed.