A systemic microbial disease in the Dungeness crab,Cancer magister,caused by a Chlamydia-like organism

A Chlamydia-like agent was diagnosed in Dungeness crabs, Cancer magister, collected from Willapa Bay and northern Puget Sound, Washington. Over a 5-year period, infected crabs were found during the months of December through March. Infection by the organism is systemic, resulting in greatly hypertrophied cells with appressed nuclei. Unlike Chlamydia or other Chlamydia-like organisms, the present microbe has a great affinity for connective tissue or connective tissue cells rather than epithelial cells. Transmission electron microscopy revealed the presence of several developmental stages that are similar to chlamydial stages, in addition to what appear to be slightly altered or aberrant stages.     

Respiratory and digestive responses of postprandial Dungeness crabs, Cancer magister, and blue crabs, Callinectes sapidus, during hyposaline exposure

Respiratory responses and gastric processing were examined during hyposaline exposure in two crab species of differing osmoregulatory ability. The efficient osmoregulator, Callinectes sapidus, displayed an immediate increase in oxygen uptake when exposed to low salinity in isolation. In contrast, the weak osmoregulator, Cancer magister, showed no change in oxygen uptake upon acute exposure (<6 h), but slight increases in oxygen uptake tended to occur over longer time scales (12–24 h). These changes were likely attributable to an increase in avoidance activity after 6 h hyposaline exposure. Following feeding in 100% SW, oxygen uptake doubled for both species and remained elevated for 15 h. When postprandial crabs were exposed to low salinities, C. sapidus were able to sum the demands of osmoregulation and digestion. Thus, gastric processes continued unabated in low salinity. Conversely, postprandial C. magister prioritized responses to low salinity over those of digestion, resulting in a decrease in oxygen uptake when exposed to low salinity. This decrease in oxygen uptake corresponded to a reduction in the rate of contraction of the pyloric stomach and a subsequent doubling of gastric evacuation time. The current study is one of the few to illustrate how summation or prioritization of competing physiological systems is manifested in digestive processes.     

Gastric processing in the Dungeness crab, Cancer magister, during hypoxia

The gastric physiology of the Dungeness crab, Cancer magister, was investigated over a range of oxygen tensions. Postprandial crabs reacted differently to hypoxia compared with unfed animals. The bradycardic response in postprandial animals was reduced, suggesting a summation of responses with feeding. A similar pattern was observed for ventilation rate. In unfed animals ventilation rate increased slightly as oxygen levels declined, but dropped significantly in oxygen tensions below 3.2 kPa, whereas in postprandial crabs it increased significantly in the lower oxygen regimes. Gastric processing of the meal was followed using a fluoroscope. Pyloric contraction rates were maintained during mild hypoxia, but decreased in 5.3 kPa oxygen tension and below. This led to an increase in clearance times of digesta from the foregut, midgut and hindgut regions. The slowing of gastric processing in the lower oxygen tensions suggested that the animals were unable to maintain their internal oxygen concentration. A significant reduction in efficiency of assimilation only occurred in the lowest oxygen regime tested (1.6 kPa). The range of hypoxia where gastric processing was affected corresponded closely to the levels of oxygen that modulate the foraging behaviour of C. magister. By using both physiological and behavioural mechanisms C. magister can maintain digestive processes, even in severely oxygen depleted environments.     

Peptidergic modulation of cardiovascular dynamics in the Dungeness crab,Cancer magister

Decapod crustacean pericardial organs contain extensive neurohormonal reserves which can be released directly into the haemolymph to act as physiological modulators. The present paper concerns the in vivo effects of two pericardial peptides, proctolin and crustacean cardioactive peptide, on cardiovascular dynamics in the crab Cancer magister. Infusion of proctolin into the pericardial sinus caused a slight decrease in heart rate concurrent with a large increase in cardiac stroke volume. It decreased haemolymph flow anteriorly through the paired anterolateral arteries and increased flow posteriorly and ventrally through the posterior aorta and sternal artery, respectively. The threshold for responses occurred at circulating concentrations of 10^-9 mol·l^-1, and haemolymph flows remained elevated for up to 30 min after peptide infusion. The effects of crustacean cardioactive peptide were less dramatic. Heart rate was not affected but a significant increase in stroke volume was observed. Crustacean cardioactive peptide increased haemolymph flow through the anterolateral arteries and increased scaphognathite rate. The threshold for crustacean cardioactive peptide activity was higher than for proctolin (10^-7 mol·l^-1 and 10^-6 mol·l^-1) but the responses to crustacean cardioactive peptide were of longer duration. The effects of proctolin on regional haemeolymph distribution in Cancer magister closely resemble the cardiovascular responses of this species when exposed to hypoxic conditions. These peptides may be implicated as cardiovascular regulators during environmental perturbations.     

A mycosis caused by Lagenidium sp. in laboratory-reared larvae of the Dungeness crab,Cancer magister,and possible chemical treatments

A mycosis in larvae of the Dungeness crab, Cancer magister, was observed about 48 hr after they had molted to second-stage zoeae in the laboratory during a chronic bioassay. The fungus was of the genus Lagenidium and caused about 40% mortality of larvae before the test was terminated. Hyphal development and subsequent sporulation of the fungus was observed over a range of 0–32‰ salinity, with an optimum around 16‰. Bioassays of eight fungicides and the herbicide trifluralin, using the larvae and fungus in separate tests, were performed to explore means of chemical treatment. Trifluralin was the most satisfactory of the chemicals screened, with captan, Cu²⁺, and benomyl also giving good results for certain treatment intervals of up to 96 hr. Malachite green was toxic to larvae at concentrations inhibiting the fungus.     

Ontogeny of Behavior in the Crab Instars of the Dungeness Crab,Cancer magister Dana 1852

Schimpansen werden im Gombe-Nationalpark in Tansania seit 1960 beobachtet. Die Tiere bilden soziale Gruppen, die wir “Communities”, die Japaner “Unit-Groups” nennen. Als Faktoren, die von 1965 bis 1980 die Größe und Zusammensetzung der Hauptgruppe beeinflußten, werden erörtert: Pubertätsalter, Fortpflanzungsreife, Fortpflanzungszyklen der Weibchen, Geburtenfolge, Wechsel von Individuen zwischen Gruppen, Geschlechterverhältnis, Alterszusammensetzung und Mortalität. Zwischen 1970 und 1972 teilte sich die Gruppe. In den folgenden 5 Jahren wurden die Männchen und mindestens eins der Weibchen, die sich als Kahama-Gruppe abgespaltet hatten, von den Männchen der größeren Kasakela-Gruppe umgebracht. Eingehend werden Mortalitätsfaktoren (Krankheiten, Verletzungen, Mutterverlust, Alter) sowie der allgemeine Gesundheitszustand besprochen. Die deutlich unterschiedenen Regen- und Trockenzeiten im Gombe beeinflussen die Gesundheit und wohl auch die Fortpflanzung. In der Gruppe gibt es Inzucht, aber der Wechsel von Weibchen in andere Gruppen (der noch einigermaßen rätselhaft bleibt) sorgt für genetische Auffrischung. Die Befunde werden mit der einzigen anderen Langzeitstudie an freilebenden Schimpansen aus den Mahali-Bergen in Tansania verglichen. Der Einfluß künstlicher Fütterung in beiden Gebieten wird erörtert.     

Gastrin/cholecystokinin-like immunoreactive peptides in the Dungeness crab, Cancer magister (Dana): immunochemical and biological characterization

The purpose of this investigation was to characterize a gastrin/cholecystokinin-like immunoreactant (G/CCK-LI) extractable from the crab, Cancer magister. G/CCK-LI was extracted best in boiling water and was found mainly in the stomach, hemolymph and carapace. A relatively large immunoreactive peptide in the stomach and apparently smaller forms in the hemolymph and carapace were separated by Sephadex G-50 fractionation. Anion-exchange chromatography further fractionated the stomach form into three major peaks. The crab material cross-reacted with three antisera specific for the common C-terminus of gastrin/CCK, but cross-reacted much less with three antisera directed against other portions of the gastrin molecule. Partially purified crab stomach G/CCK-LI inhibited the binding of labeled CCK to mouse brain G/CCK receptors but not to rat pancreatic CCK receptors. The crab peptide did not stimulate rat gastric acid or rat pancreatic amylase secretion. These results indicate that the crab peptides are structurally similar to, but distinguishable from, the bioactive C-terminal amino acid sequence common to gastrins and CCKs.     

Kiitricha minuta n. sp., a peculiar hypotrichous ciliate (Ciliophora, Spirotrichea) from the Yellow Sea

The morphology and infraciliature of a new ciliate, Kiitricha minuta n. sp., isolated from the Yellow Sea, were investigated using live observation and protargol impregnation. Kiitricha minuta represents a third member of the rarely known order Kiitrichida. It is unique in the subclass Hypotrichia in having many rows of small uniform cirri along the right side of the body and the dorsal kineties composed of dikinetids, most of which bear two cilia. Kiitricha minuta n. sp. is ovoid and measures about 60 x 45 microm in vivo. It has a huge buccal cavity occupying about 80% of the body length, numerous body extrusomes, one macronucleus and two micronuclei, 27-27 adoral membranelles, 9-12 frontoventral cirral rows, a submarginal row of 7-9 cirri, 6 or 7 transverse cirri, and roughly 7-9 dorsal kineties. This new species differs distinctly from its only congener Kiitricha marina by its smaller size (60 microm vs. 80-150 microm), the presence of body extrusomes (vs. absent), the different macronuclear pattern (one vs. two nodules), and the lower number of frontoventral cirral rows (9-12 vs. 21-26), which terminate at the anterior two-thirds of body (vs. extend to the posterior). The new term "submarginal cirral row" is introduced to distinguish from the marginal cirral row in typical hypotrichs sensu lato. Based on our new observations and the literature, an improved diagnosis for the genus Kiitricha is provided and its phylogenetic importance is discussed.     

Pathology of Hematodinium infections in snow crabs (Chionoecetes opilio) from Newfoundland, Canada

Bitter crab disease (BCD) of snow crabs, Chionoecetes opilio, is caused by a parasitic dinoflagellate, Hematodinium sp. The disease has shown an alarming increase in prevalence in the commercial fishery in eastern and northeastern areas of Newfoundland and Labrador since it was first recorded there in the early 1990s. We documented histopathological alterations to the tissues in snow crabs with heavy infections of Hematodinium sp. and during sporulation of the parasite. Pressure necrosis was evident in the spongy connective tissues of the hepatopancreas and the blood vessels in most organs. In heavy infections, little remained of the spongy connective tissues around the hepatopancreas. Damage to the gills varied; in some cases it was severe, particularly during sporulation, involving apparent thinning of the cuticle, loss of epithelial cells, and fusion of the membranous layers of adjacent gill lamellae. Affected lamellae exhibited varying degrees of distention with a loss of trabecular cells, hemocyte infiltrations, and swelling or "clubbing" along the distal margins. Large numbers of zoospores were located along the distal margins of affected lamellae suggesting that sporulation may cause a lysis or bursting of the thin lamellar cuticle, releasing spores. Pressure necrosis, due to the build up of high densities of parasites, was the primary histopathological alteration in most tissues. Hematodinium infections in the snow crab are chronic, long-term infections that end in host death, during sporulation of the parasite.     

悬游双眉虫(原生动物,纤毛门)无性生殖期间的形态发生

应用蛋白银染色技术研究了悬游双眉虫青岛种群无性生殖期间皮层结构和核器的演化过程,其主要特征为:后仔虫口原基独立地出现于紧靠虫体左侧第一根横棘毛的皮层下小龛,其中毛基粒不参与其它棘毛原基的形成;老的口围带发生后半部的局部重建而非整个的由前仔虫简单继承;在前仔虫中,波动膜原基来自老结构的反分化,而在后仔虫中则来自口原基;所有棘毛原基均为独立发生并与老结构没有任何关系;在前仔虫中,口棘毛(即左侧第一根额棘毛)来自于波动膜的反分化,而在后仔虫中则为独立发生;背触毛列于老的结构当中产生,并由最右一列原基演化出3根尾棘毛;两大核片段的改组带从一端向另一端移动 ,并随着两者的融合而消失.文中同时对前人有关该属发生模式的若干存疑问题做了探讨 [动物学报 54(3):517-524,2008].     

海洋纤毛虫黄色伪角毛虫无性生殖期间的形态发生

利用蛋白银染色技术研究了海洋纤毛虫———黄色伪角毛虫Pseudokeronopsisflava (Cohn ,186 6 )Wirns berger,Larsen&Uhlig ,1987无性生殖期间的细胞发生学。其主要特征为 :1)前仔虫口原基以独立发生的方式出现并独特地形成于口前庭右侧的皮层深处 ,由其对老口围带进行完全的更新 ;2 )老口器不参与新口器的形成 ,完全被吸收 ;3)前仔虫的额 -腹 -横棘毛原基同样为独立发生 ,老结构可能不参加其随后的发育 ;4 )后仔虫的口原基、波动膜原基及额 -腹 -横棘毛原基均来自最初排列无序的毛基粒发生场 ;5 )背触毛及缘棘毛的更新发生在老的结构中 ,并向前后延伸取代老结构 ;6 )在整个发生过程中 ,无大核融合现象。文中同时对该种所表现的发生学特征及系统学意义做了探讨     

Epidemiology of bitter crab disease (Hematodinium sp.) in snow crabs Chionoecetes opilio from Newfoundland, Canada

The parasitic dinoflagellate Hematodinium sp. causes a condition known as bitter crab disease (BCD) in snow crabs Chionoecetes opilio and Tanner crabs C. bairdi. As the name of the condition implies, crabs infected with BCD are unmarketable due to their bitter flavor. We surveyed the distribution of BCD in 3 regions within the snow crab fishery of Newfoundland from 1997 to 2003. Over time, the disease has become firmly established in Conception and Bonavista Bays and persists at low levels on the Avalon fishing grounds. An epizootic occurred within Bonavista and Conception Bays in 1999 and persisted in Conception Bay in 2000, reaching prevalences of over 2% to 9% in trapped and trawled male crabs and from 19 to 26% in trawled and trapped female crabs, respectively. Infections were highest in females and small males, i.e. the unfished and pre-recruit portions of the fishery. In a mortality study, all of the naturally infected crabs died and 50% of the experimentally inoculated crabs died. Patterns in the molting cycle and prevalence of infection indicate that transmission occurs during the post-molt condition, and that overt infections probably develop 2 to 4 mo later with mortalities occurring at least 3 to 4 mo thereafter. The hydrography of this bay may have contributed to the epizootic as infections were centered within the deeper confines of the bay. Analysis of various abiotic factors uncovered a significant positive association between prevalence, depth and mud/sand substrates; the nature of this relationship was not apparent but may be related to diet or alternate hosts. Lastly, given the increase in BCD in snow crabs in Newfoundland, we recommend that fishery management programs for Chionoecetes fisheries employ non-selective gear to monitor for Hematodinium infections in female and juvenile crabs because these under-sampled members of the population may forewarn of impending recruitment declines that might otherwise remain unexplained.     

The morphology, ontogeny, and small subunit rRNA gene sequence analysis of Diophrys parappendiculata n. sp. (Protozoa, Ciliophora, Euplotida), a new marine ciliate from coastal waters of southern China

The morphology, morphogenesis, and phylogeny of Diophrys parappendiculata n. sp., a large marine ciliate isolated from the coastal waters of Daya Bay, southern China, were investigated. This new species is characterized by a combination of its large size, appendiculata-pattern of ciliature, and bipartite adoral zone of membranelles. The main stages of morphogenesis during binary fission were also recorded and described. Comparisons of morphological characteristics with similar congeners support the validity of the new species. The small subunit rRNA gene sequence of D. parappendiculata is 96.3-99.94% similar to those of four other congeners; it differs in four nucleotides from that of Diophrys appendiculata (i.e. structural similarity was 99.94%). Phylogenetic analysis indicates that D. parappendiculata n. sp. falls into the Diophrys clade and is most closely related to the well-known D. appendiculata.     

Morphology and cell division of Saudithrix terricola n. gen., n. sp., a large, stichotrich ciliate from Saudi Arabia

The morphology and main ontogenetic traits of a new stichotrich ciliate, Saudithrix terricola Foissner, AL-Rasheid and Berger n. gen., n. sp., from a terrestrial habitat in Saudi Arabia were investigated using live observation, protargol impregnation, and scanning electron microscopy. Saudithrix terricola is characterized by a large (200-350 x 70-150 microm), flexible body; an adoral zone formed like a three-quarter circle; a sickle-shaped buccal lip with a widened paroral forming a cyrtohymenid pattern with the endoral; 11 frontal and frontal-ventral cirral rows (including right marginal rows) and one left marginal row covering the ventral side; two buccal cirri; six to nine transverse cirri; three dorsal kineties; and two macronuclear nodules. The resting cyst is about 85 microm across, has a smooth wall, and a fluffy mucous layer. Most cirral anlagen originate within the parental rows and are arranged side by side, the proximal portion of the adoral zone of membranelles is reorganized, and some parental dorsal bristles are maintained. Neither the morphological nor the ontogenetic data reveal the systematic position of Saudithrix within the stichotrichs. The term multicorona is introduced and describes a frontal ciliature composed of four or more cirral bows.     

甘肃定西华家岭土壤纤毛虫群落对生态恢复的响应

为了解土壤纤毛虫群落对生态恢复下的土壤环境的响应,于2007年9月—2008年8月用活体观察法和"三级十倍环式稀释法"对甘肃定西华家岭5个不同恢复阶段的人工云杉林和1个荒草坡对照点的土壤纤毛虫群落以及季节动态进行了研究,探讨了土壤纤毛虫群落组成对生态恢复下土壤环境的相关性。共鉴定到127种纤毛虫,隶属于3纲9目34科50属。研究发现,各不同恢复年限土样中土壤纤毛虫的物种分布存在明显差异,并随恢复时间的延长,样点间物种相似性减小,群落组成复杂化,丰度、物种数和物种多样性指数均呈上升趋势。优势类群也发生了响应,由I号对照样点和恢复初期II号样点的肾形目变为恢复后期样点的下毛目。结果显示,土壤纤毛虫群落动态很好地响应了生态恢复过程中土壤环境条件的变化。土壤纤毛虫群落可用于陆地生态恢复评价,但要建立有效可行的、具有普遍意义的评价指标体系,尚需大量的和系统的工作。     

The relative importance of habitat-specific settlement, predation and juvenile dispersal for distribution and abundance of young juvenile shore crabs Carcinus maenas L.

Young juveniles of many motile benthic species are concentrated in structurally complex habitats, but the proximate causes of this distribution are usually not clear. In the present study, I assessed three potentially important processes affecting distribution and abundance of early benthic stages in the shore crab (Carcinus maenas): (1) selection of habitat by megalopae (postlarvae); (2) habitat-specific predation; and (3) post-settlement movements by juveniles. These processes were assessed concurrently over 3-9 days at two spatial scales: at the scale of square meters using cage techniques within nursery areas, and at the scale of hectares using isolated populations of juvenile shore crabs in small nursery areas as mesocosms. The results were compared to habitat-specific distribution in the field.Shore crab megalopae and first instar juveniles (settlers) were distributed non-randomly among micro-habitats in the assessed nursery areas, with great densities in both mussel beds, eelgrass and filamentous algal patches (on average 114-232 settlers m⁻²), and significantly smaller densities on open sand habitats at all times (on average 4 settlers m⁻²). The same habitat-specific settlement pattern was found in cages where predators were excluded, suggesting that active habitat selection at settlement was responsible for the initial distribution. Older juveniles (second to ninth instar crabs) were also sparse on sand, but in contrast to settlers, were concentrated in mussel beds, which showed significantly greater densities than eelgrass and algal habitats. The cage experiment demonstrated a dynamic distribution of juvenile crabs. Young juveniles constantly migrated over open sand habitats (20 m or further) and colonized the experimental plots in a habitat-specific pattern that reflected the distribution in the field. This pattern was also found for very small crabs colonizing predator-exclusion cages, suggesting that selection of habitat by migrating juveniles caused the ontogenetic change in habitat use. Although post-settlement movements were great within nursery areas, juvenile dispersal at a regional scale appeared to be small, and the recruitment of juvenile shore crabs to the shallow bays occurred mainly through pelagic megalopae.Conservative estimates at the scale of whole nursery areas, based on migration trap data and field samples, indicated great mortality of settlers and early benthic stages of shore crabs. Results from the cage experiment suggest that predation by crabs and shrimp were responsible for the high settlement mortality. Both enclosed cannibalistic juvenile crabs and local predators on uncaged habitat plots caused significant losses of settlers in all habitats (on average 22% and 64% 3 day⁻¹, respectively). The effect of predators was highly variable between trials, but differed little between habitat types, and predation had no detectable proximate effect on juvenile distribution, despite the great losses. Small settlement densities on sand habitats in combination with a refuge at low prey numbers, and an aggregation of cannibalistic juvenile crabs in nursery habitats appear to decrease the effect of habitat-specific predation rates on the distribution of juvenile shore crabs. This study demonstrates that active habitat selection at settlement followed by a dynamic redistribution of young juveniles can be the proximate processes responsible for habitat-specific distribution of epibenthic juveniles, and indicate that predation represents a major evolutionary process reinforcing this behavior.