Immunohistochemical and ultrastructural studies on ciliary sense organs of arrow worms (Chaetognatha)

We examined epibenthic and pelagic species of Chaetognatha (Spadellidae and Sagittidae) using immunohistofluorescence and confocal laser scanning microscopy to detect tubulin and cell nuclei in whole-mount preparations and scanning and transmission electron microscopy to visualize the ultrastructural organisation of their ciliary sense organs. All chaetognaths bear three types of ciliary sense organs distributed throughout the body: (1) transversally oriented ciliary fence organs, (2) longitudinally (parallel to the anterior-posterior axis) oriented ciliary tuft organs, and (3) a ciliary loop, the corona ciliata. This study targets the ciliary fence as well as the ciliary tuft organs. Two types of primary receptor cells constitute the ciliary fence and ciliary tuft organs. The first type of receptor cells forms a single cell line along the midline axis of the organs, whereas the second type of receptor cells forms multiple lines of cells at either side of type 1 cells. Each receptor cell extends a single, non-locomotory cilium from its narrow apex collared by slender, non-reinforced microvilli; however, both types of sensory cells considerably differ on ultrastructural level. Type 1 sensory cells have thicker cilia than those protruded by the type 2 sensory cells which are characterized by rootlets consisting of an elongated, amorphous distal as well as a cross-striated proximal portion. These results likely reveal that both types of sensory cells have distinct functions.     

Trophic importance of the chaetognaths Eukrohnia hamata and Sagitta gazellae in the pelagic system of the Prince Edward Islands (Southern Ocean)

Trophodynamics and predation impact of the 2 dominant chaetognaths Eukrohnia hamata and Sagitta gazellae were investigated at 19 stations in the vicinity of the Prince Edward Islands and at a 24-h station occupied at the sub-Antarctic Front in late summer (April/May) 1996. During the entire investigation, the zooplankton assemblages were numerically dominated by copepods with densities ranging from 21 to 170 ind. m⁻³. Amongst the copepods, Clausocalanus brevipes, Metridia gerlachei and M. lucens dominated accounting for >90% of the total. Generally, chaetognaths were identified as the second most important group composing at times up to 30% (mean = 14.7%) of total zooplankton abundance. Of the two chaetognath species, E.␣hamata was generally numerically dominant. Gut content analysis showed that both chaetognath species are opportunistic predators generally feeding on the most abundant prey, copepods. No feeding patterns were evident during the 24-h station, suggesting that both species feed continuously. The feeding rates of E. hamata ranged from 0 to 0.50 prey ind. day⁻¹ and between 0 and 0.90 prey ind. day⁻¹ for S. gazellae. The maximum total predation impact of E. hamata was equivalent to 5.2% of the copepod standing stock or up to 103% of copepod production per day. For S. gazellae the predation impact was lower, reaching a level of 3.2% of the copepod standing stock or 63% of the daily copepod production. Chaetognaths can, therefore, be regarded as an important pelagic predator of the Prince Edward Islands subsystem. Received: 27 March 1997 / Accepted: 11 September 1997     

Integumental organs of unknown function on chelipeds of deep-sea crabs,genus Hypsophrys

Homolid crabs (Hypsophrys) from water deeper than 700 m in the Straits of Florida and Arabian Sea have smooth darkened oval spots contrasting with the surrounding roughened integument on inner and outer surfaces of each pincer at the base of the fixed finger. Cuticle is thinner over these spots than over surrounaing tissues. Beneath each spot is an organ composed of two markedly contrasting layers of tissue: (1) an outer, densely staining layer of tightly packed tubules, relatively straight and perpendicular to the overlying surface proximally but progressively convoluted and narrowed distally, finally ending blindly in association with the overlying thinned cuticle; (2) an inner layer of relatively large, eosinophilic, irregular cells with dark nuclei also trending at a right angle to the integument and bulging into the hemal sinus of the hand but separated from it by an epidermal lining. Droplets secreted from the inner layer apparently move into and along the tubules. Similar organs are known in no other crabs. The function is unknown but the structure suggests that they may be photophores.     

Nippostrongylus brasiliensis: further properties of antibody-damaged worms and induction of comparable damage by maintaining worms in vitro.

When adult Nippostrongylus brasiliensis were maintained in vitro they became damaged. Using the criteria of ultrastructural morphology, acetylcholinesterase isoenzyme pattern and the behaviour of the worms after transfer to a normal rat, this damage appeared to be similar to that produced by the in vivo action of antibodies. Antibodies were shown to be responsible for the anterior migration of adult worms which occurs during primary infections in mature rats and in the prolonged infections seen in lactating and immature rats. Antibody damaged worms and worms unaffected by antibodies were equally able to stimulate the immune response required for worm expulsion. Apparently antibody damage is not required for the initiation of the second immune component necessary for expulsion of this parasite.     

Comparative anatomy of excretory organs in vestimentiferan tube worms (Pogonophora, Obturata)

In the past, the excretory systems of only few vestimentiferan species have been examined in detail. This study presents comparative data on eight species on the basis of histological serial sections. Ridgeia piscesae was studied by transmission electron microscopy. All species examined possess a central excretory organ consisting of numerous small branching and intertwined excretory tubules. These are connected to voluminous glandular excretory ducts that lead to the exterior by single or paired excretory pores located at the anterior end of the vestimentum. A comparative analysis shows differences among the species with regard to several features, such as the number of excretory pores, presence/absence of excretory grooves and papillae, position of the excretory organ relative to the brain, and the shape of the excretory ducts. Neither podocytes nor coelomoducts could be detected; therefore, there is no indication of the presence of metanephridia. The vestimentiferan excretory system shows some similarities with the design in Athecanephria (Pogonophora, Perviata) and a general resemblance to the design in sabellid polychaetes, even though in the latter metanephridia are clearly present.     

Rubyspira, new genus and two new species of bone-eating deep-sea snails with ancient habits

Rubyspira, a new genus of deep-sea snails (Gastropoda: Abyssochrysoidea) with two living species, derives its nutrition from decomposing whalebones. Molecular phylogenetic and morphological evidence places the new genus in an exclusively deep-sea assemblage that includes several close relatives previously known as fossils associated with Cretaceous cold seeps, plesiosaur bones, and Eocene whalebones. The ability to exploit a variety of marine reducing environments may have contributed to the evolutionary longevity of this gastropod lineage.     

Hymenolepis diminuta: ultrastructural observations on complement-mediated tegumental lysis and destrobilation of 4-day-old worms in vitro

Changes in the ultrastructure of the tegument and subtegumental cells of 4-day-old Hymenolepis diminuta were studied in vitro in 50% fresh normal rat serum over a 5-h period and compared with heat-inactivated serum and saline controls. First, membrane-bound vesicles accumulate above the microthrix-border. After 30–40 min large vacuoles, which may contain membranous elements, appear in the tegument at a time when the surface of the young strobila is virtually denuded of the microthrix-border. With prolonged incubations there are subtegumental secretory inclusions with dark, enveloping cytoplasm in the tegument and finally the apical plasma membrane, together with the majority of the matrix, is lost. The disrupted portion of the worm is abruptly demarcated from the comparatively intact scolex/anterior neck region by a constriction. Even after 5 h incubation there is no evidence of loss of tegumental matrix components from regions anterior to the constriction but the neck region shows a significant denudation of the microthrix layer and the tegument contains numerous inclusions. The scolex tegument only showed little evidence of loss of membrane from the surface. Possible mechanisms for the avoidance of complement-mediated lysis in the anterior region are discussed.     

Some further observations on synergism between chloramphenicol and polymyxin B in relation toSalmonella bacteria

Summary The synergism between chloramphenicol and polymyxin B sulphate, earlier noticed using a replica technique, has been reexamined applying quantitative methods. Vital count experiments in suspensions ofSalmonella typhimurium in broth have revealed that addition of bacteriostatic concentrations of chloramphenicol in a range of 5–100 μg/ml to bacteriostatic concentrations of polymyxin (0.1–0.9 μg/ml) produce a strong bactericidal effect (synergism). Combinations of bactericidal concentrations of polymyxin (1 μg/ml and higher) with chloramphenicol also exert a very high degree of bactericidal activity, though no more than with polymyxin alone (no synergism). Chloramphenicol therapy sustained with polymyxin, may be of therapeutic value in the eradication of stubborn enteralSalmonella infections. With the technical assistance of MissM. J. Wisse.     

Purification, characterization, and lytic activity against Naegleria fowleri of two amoebicins produced by Bacillus licheniformis A12.

Bacillus licheniformis A12 produces two amoebolytic substances (amoebicins A12-A and A12-B) in liquid media during sporulation. Both substances have been purified and characterized. They are heat- and protease-resistant peptides containing aspartic acid, glutamic acid, serine, proline, and tyrosine in a molar ratio of 5:2:2:2:2. No fatty acids or carbohydrates have been detected. Their molecular weight is 1,430. Purified amoebicins A12-A and A12-B exhibit amoebolytic action against Naegleria fowleri. They also exhibit antibiotic action against yeasts (Saccharomyces heterogenicus and Cryptococcus neoformans) and several fungal species (Aspergillus niger, Microsporum canis, Mucor plumbeus, and Trychophyton mentagrophytes). Their antibacterial spectrum appears to be restricted to Bacillus megaterium, Corynebacterium glutamicum, and Sarcina sp.