Early development and microhabitat of the monogenean Horricauda rhinobatidis, with observations on the related Troglocephalus rhinobatidis, from Rhinobatos batillum from Queensland,Australia

The small monocotylid monogenean Horricauda rhinobatidis is abundant on the gills of its host Rhinobatos batillum, whereas the larger, related monogenean Troglocephalus rhinobatidis is comparatively uncommon. Young specimens of Horricauda live between the host's secondary gill lamellae. Post-oncomiracidia have 14 marginal booklets but as the larvae develop these are supplemented first by a pair of hamuli and then by muscular ventral loculi followed by six forwardly-directed, dorsal spines. By impaling secondary gill lamellae these spines may serve to prevent parasites from being dislodged by gill ventilating currents. Before reaching sexual maturity the parasites leave the secondary gill lamellae and establish themselves in the septal canals. It is uncommon to find more than one adult specimen of Horricauda in each septal canal. The significance of this in relation to sperm exchange is discussed. Like Troglocephalus, Horricauda has eight head sacs, and the suggestion is made that these sacs may play a part in feeding.     

Microhabitats of gill parasites (Monogenea and copepoda) of teleosts (Scomberoides spp.)

Ramasamy P., Ramalingam K., Hanna R. E. B. and Halton D. W. 1985. Microhabitat of gill parasites (Monogenea and Copepoda) of teleosts (Scomberoides spp.). International Journal for Parasitology15: 385–397. The parasites Vallisia indica, Allodiscocotyla chorinemi, Heterapta chorinemi, and Dionchus remorae exhibited site specificity on the gills of Scomberoides commersonianus, S. tol, S. lysan and S. tala, whereas the copepod Caligus sp. did not. Observations on site preference revealed microhabitat differences along the length of gill filaments, along the anterio-posterior axis of the gill, between external and internal gill filaments and on different gill arches. Site preference varied with parasite density on each gill and host. An interspecific association test between pairs of species revealed, in some cases, a positive association, and in other cases a negative association. There were apparently no association? between certain pairs of species. A comparison of intensity within pairs of parasite species infecting the same host revealed either an inverse or a direct correlation. The numerical dominance and prevalence of parasites differed on each host species. This study indicates that intra- and interspecific competition may occur among the gill parasites. The direction and speed of ventilation water-currents and certain intrinsic factors of the parasite themselves may determine their microhabitat restriction on the gills.     

Response to environmental salinity of Na-KATPase activity in individual gills of the euryhaline crab Cyrtograpsus angulatus

The occurrence, localization and response to environmental salinity changes of Na⁺-K⁺ATPase activity were studied in each of the individual gills 4-8 of the euryhaline crab Cyrtograpsus angulatus from Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina). Na⁺-K⁺ATPase activity appeared to be differentially sensitive to environmental salinity among gills. Upon an abrupt change to low salinity, a differential response of Na⁺-K⁺ATPase activity occurred in each individual gill which could suggest a differential role of this enzyme in ion transport process in the different gills of C. angulatus. With the exception of gill 8, a short-term increase of Na⁺-K⁺ATPase specific activity was observed in posterior gills, which is similar to adaptative variations of this activity described in other euryhaline crabs. However, and conversely to that described in other hyperregulating crabs, the highest increase of activity occurred in anterior gills 4 by 1 day after the change to dilute media which could suggest also a role for these gills in ion transport processes in C. angulatus. The fact that variations of Na⁺-K⁺ATPase activity in anterior and posterior gills were concomitant with the transition to hyperregulation indicate that this enzyme could be a component of the branchial ionoregulatory mechanisms at the biochemical level in this crab. The results suggest a differential participation of branchial Na⁺-K⁺ATPase activity in ionoregulatory mechanisms of C. angulatus. The possible existence of functional differences as well as distinct regulation mechanisms operating in individual gills is discussed.     

The attachment of the monogenean parasite Callorhynchicola multitesticulatus to the gills of its holocephalan host Callorhynchus milii

Llewellyn J. and Simmons J. E. 1984. The attachment of the monogenean parasite Callorhynchicola multitesticulatus to the gills of its holocephalan host Callorhynchus milii. International Journal for Parasitology14: 191–196. C. multitesticulatus when juvenile (up to about 10 mm long) attaches itself by four pairs of clamps to the secondary gill lamellae of its host the elephant fish Callorhynchus milii. However, in adult parasites the haptor invades the host tissue and the stalk connecting the haptor with the body-proper becomes surrounded by a sleeve of fibrous host inflammatory reaction tissue. The stalk is provided with annuli with anteriorly-directed flanges which are pressed into the walls of the sleeve of host tissue when the diameter of the stalk increases as a result of the contraction of well-developed sub-tegumentary longitudinal muscles.     

Dietary Ca inhibits waterborne Cd uptake in Cd-exposed rainbow trout, Oncorhynchusmykiss

The effects of chronic exposure to waterborne Cd and elevated dietary Ca, alone and in combination, were examined in juvenile rainbow trout, Oncorhynchusmykiss. Fish were chronically exposed to 0.05 (control) or 2.56 μg/l Cd [as Cd(NO₃)₂·4H₂O] and were fed 2% body mass/day of control (29.6 mg Ca/g) or Ca-supplemented trout food (52.8 mg Ca/g as CaCl₂·2H₂O). Cd accumulated mainly in gill, liver, and kidney. Waterborne Cd inhibited unidirectional Ca uptake from water into the gill and induced hypocalcemia in the plasma on day 40. Waterborne Cd also induced an elevated Ca concentration on day 20 in the gill tissue of trout fed the Ca-supplemented diet and a decreased Ca concentration on day 35 in the gills of trout fed the control diet. Dietary Ca protected against Cd accumulation in gill, liver, and kidney, but did not protect against the inhibition of Ca uptake into the gill or plasma hypocalcemia. When fed Ca-supplemented diet and exposed to waterborne Cd, fish showed 35% mortality, compared to 0–2% in control fish and in the Cd-exposed fish with normal Ca in the diet. Growth, on the other hand, was not affected by any treatment.     

Invasion of Ceratomyxa shasta (Myxozoa) and comparison of migration to the intestine between susceptible and resistant fish hosts

The myxozoan parasite Ceratomyxa shasta infects salmonids causing ceratomyxosis, a disease elicited by proliferation of the parasite in the intestine. This parasite is endemic to the Pacific Northwest of North America and salmon and trout strains from endemic river basins show increased resistance to the parasite. It has been suggested that these resistant fish (i) exclude the parasite at the site of invasion and/or (ii) prevent establishment in the intestine. Using parasites pre-labeled with a fluorescent stain, carboxyfluorescein succinimidyl diacetate (CFSE), the gills were identified as the site of attachment of C. shasta in a susceptible fish strain. In situ hybridization (ISH) of histological sections was then used to describe the invasion of the parasites in the gill filaments. To investigate differences in the progress of infection between resistant and susceptible fish, a C. shasta-susceptible strain of rainbow trout (Oncorhynchus mykiss) and a C. shasta-resistant strain of Chinook salmon (Oncorhynchus tshawytscha) were sampled at consecutive time points following exposure at an endemic site. Using ISH in both species, the parasite was observed to migrate from the gill epithelium into the gill blood vessels where replication and release of parasite stages occurred. Quantitative PCR verified entry of the parasite into the blood. Parasite levels in blood increased 4 days p.i. and remained at a consistent level until the second week when parasite abundance increased further and coincided with host mortality. The timing of parasite replication and migration to the intestine were similar for both fish species. The field exposure dose was unexpectedly high and apparently overwhelmed the Chinook salmon’s defenses, as no evidence of resistance to parasite penetration into the gills or prevention of parasite establishment in the intestine was observed.     

Gross morphology and surface ultrastructure of the gills of Odontesthes argentinensis (Actinopterygii, Atherinopsidae) from a Southwestern Atlantic coastal lagoon

Odontesthes argentinensis was collected from Mar Chiquita Coastal Lagoon, the Southernmost coastal Atlantic Lagoon of Argentina. The morphology of the gills was analyzed by scanning electron microscopy. The morphology of the superficial structures of the gill filaments and pharyngeal region of the gill arch was discussed and related to their functional aspects. The gills arches are structurally similar to those of other teleosts and bring out the osmoregulatory capacity of this species. The epithelium that covers the surface of the filaments and the pharyngeal region of the gill arch is formed by polygonal pavement cells with conspicuous microridges. These folds in the membrane are not denoted in the epithelium of the respiratory lamellae. Apical crypts of chloride cells are present on the afferent and interlamellar filament surfaces, but are absent elsewhere on the gill arch. The highest density of mucous cells is observed into the gill filament and the pharyngeal region which indicates the existence of a protective strategy of the respiratory lamellae and the pharynx. The epithelium of the gill arches and the rakers is studded with spines. There are taste buds along the whole pharyngeal region that may be associated with their participation in tasting at this zone.     

Influence of highly unsaturated fatty acids on the responses of white shrimp (Litopenaeus vannamei) postlarvae to low salinity

Salinity stress tests are commonly applied in shrimp hatcheries to estimate the quality of postlarvae (PL) to be used during growout. Higher larval survival during culture and to a salinity stress test in both fish and crustaceans have been reported when specimens were offered a diet containing high levels of highly unsaturated fatty acids (HUFA). However, it is not clear if increased survival is a result of better overall physiological condition resulting from the diet or a specific effect of HUFA on osmoregulatory mechanisms. This study analyzed if HUFA-rich diets could modify the fatty acid composition of membranes in gills, and if this change in composition could affect the activity of the Na⁺/K⁺ ATPase pump and carbonic anhydrase in relation to changes in salinity. One-day-old postlarvae (PL1) pooled from different spawns were fed for 20 days with Artemia sp. nauplii enriched with three levels of HUFA: low, medium and high. At PL20, survivals during culture and to salinity stress test (tap water for 30 min) were evaluated. Also at this stage, Na⁺/K⁺-ATPase and carbonic anhydrase activity, morphometric variables, and fatty acid composition in the hepatopancreas and gills were measured after they were submitted to a salinity challenge in dilute seawater (10 ppt) for 3 h. No significant differences were observed in survival rates during culture, but survival to a salinity stress test was higher and gill area was larger in PL20 fed the Artemia sp. nauplii enriched with medium HUFA levels, probably as a result of an increased 22:6n-3 content and higher 22:6n-3/20:5n-3 ratio in this diet and in the tissues of the organisms fed this diet. Na⁺/K⁺-ATPase specific activity was significantly higher in posterior gills, while the specific activity of the carbonic anhydrase was higher in anterior gills. Enzymatic activities increased significantly in PL20 submitted to a salinity challenge, and HUFA levels in the diet affected both. The proportion of fatty acids in hepatopancreas and gills were significantly affected not only by diet, but also by exposure to dilute media. This effect is discussed in relation to an increase in gill surface and changes in fatty acid composition in the phospholipids present in gill membranes, which can modify the permeability and the activity of the Na⁺/K⁺-ATPase pump. The beneficial effect of HUFA supplementation in the diet on survival to salinity stress test is partially related to modification of fatty acid composition of gills and to a larger gill area, which in turn enhances osmoregulatory mechanisms, namely Na⁺/K⁺-ATPase and carbonic anhydrase activities.     

Emergence of the cercariae of Gorgoderina vitelliloba from daughter sporocysts

The daughter sporocyst of Gorgoderina vitelliloba develops attached to the gills of its molluscan host, Pisidium. It has a conical attachment structure at one end of its body through which the birth pore opens. Cercariae emerge through the birth pore, their passage being apparently lubricated by copious secretions from the stylet glands. Only after emergence does the anterior tail chamber envelop the cercarial body to form the typical cystocercous cercaria. When sporocysts were freed from gill tissue and maintained in vitro, cercariae failed to escape from the sporocyst and several encysted, in situ. It is suggested that if this occurred naturally a different host range would be encountered and the long term result might be the evolution of a new species.     

Functional responses associated with pallial organ variations in the Pacific oyster Crassostrea gigas (Thunberg, 1793)

The plasticity and function of the pallial organs were studied in the Pacific oyster Crassostrea gigas from three sites of Bourgneuf Bay (French Atlantic coast, 46-47°N, 1-2°W) characterized by different turbidity conditions. Labial palp area was closely and positively related to the turbidity gradient. No clear pattern was established between the gill area and the gradient of suspended particulate matter (SPM). The functional responses induced by these morphological variations were investigated in the laboratory by means of ecophysiological experiments and endoscopic observations. Oysters with different pallial organ areas were supplied with mixed suspensions of heat-killed Tetraselmis suecica and living Skeletonema costatum added to different concentrations of kaolinite to simulate low (SPM = 8.5 ± 0.4 mg l^− 1) and high (SPM = 48.3 ± 1.4 mg l^− 1) turbidity conditions. At each SPM concentration, heat-killed T. suecica were preferentially rejected in pseudofaeces compared to S. costatum, indicating a preingestive particle selection. At low seston load, clearance rate (CR) was closely and positively related to gill area and particle selection occurred only on the gills, between the ventral grooves and dorsal tracts. At higher seston load, palps exhibited a particle-sorting capacity dependent on gill area. Indeed, with small gills, an increase in selection efficiency (SE) and CR was positively related to palp area. On the other hand, large gills processed the particles without an effect of palps but with a decrease in CR. The functional responses associated with pallial organ variations clearly showed that the preingestive particle processing in oysters is an integrated mechanism dependant on the gill and labial palp areas.     

Salinity adaptation of HCO3−-dependent ATPase activity in the gills of blue crab (Callinectes sapidus)

A bicarbonate-dependent ATPase (EC 3.6.1.3) was found in microsomal preparations from blue crab gills. When the crabs were transferred to low salinity (200 mosmolal) from seawater (1000 mosmolal), the HCO₃^?-dependent ATPase increased in all gill pairs, reaching its new steady state in 2 weeks. The greatest increase occurred in the sixth and seventh gill pairs (approx. 2.5-fold). Maximal enzyme activity was observed at an Mg²⁺ concentration of 3 mM and an optimal pH of 7.8. The apparent K_a for HCO₃^? was found to be 8.9 mM. Kinetic analysis showed that low-salinity adaptation increased the V_max without altering the K_m for ATP. When the microsomes from high-salinity crab gills were treated with detergent or assayed at different temperatures, the total enzyme activity did not reach the activity levels seen after adaptation to low salinity. These results suggest that the alteration of HCO₃^?-ATPase activity may be due to synthesis, rather than modulation of membranes or of the existing enzyme activity.     

Morphological observations on the gills of dendrobranchiate shrimps

Gill morphology, traditionally, has played an important role in attempts to reconstruct the phylogenetic history of the Crustacea Decapoda. We examined the gills of dendrobranchiate shrimps (Crustacea, Decapoda, Dendrobranchiata) to test the assumption that all members of the clade have gills that are “dendrobranchiate” (highly branching) in form, from whence the taxon name Dendrobranchiata comes. Currently, the Dendrobranchiata consists of two superfamilies and seven families. Specimens from two genera in each of the known families were examined using light and scanning electron microscopy. Members of the family Luciferidae, all of which lack gills as adults, were not examined. Only one genus was examined for the Penaeidae (because they have been the subject of numerous previous studies) and Sicyoniidae (a monogeneric family). All gills examined have secondary branches that are further subdivided, conforming to existing and rather broad definitions of dendrobranchiate gills. Families with “typical” dendrobranchiate gills, which consist of curved secondary branches that in turn bear branched (dendritic) tubular tertiary elements on their distal surfaces, include the Penaeidae, Aristeidae, and Solenoceridae. In other families, secondary and tertiary gill elements are sometimes quite flattened, and the tertiary elements are not dendritic, giving the gill a distinctly non-dendrobranchiate appearance. Flattened biserial secondary branches and their flattened tertiary elements are particularly obvious in gills of the monogeneric family Sicyoniidae (Sicyonia). Within the family Sergestidae, gills of the genus Sergestes are unusual in having secondary branches that arise from the main gill axis in an alternating pattern; these gills also have distinctly oval tertiary elements that are not further subdivided and are directed basally rather than distally. Another sergestid genus, Petalidium, displays gills that differ from those of Sergestes; in Petalidium the secondary branches also come off the main gill axis in an alternating pattern, but these branches are more widely spaced and have relatively larger and broader tertiary elements when compared with gills of Sergestes. The family Benthesicyemidae also contains species with different gill types; Gennadas is shown to have flattened, plate-like tertiary elements, whereas Benthesicyemus has more typical dendrobranchiate gills. The significance of this variation in gill morphology within families and within the Dendrobranchiata as a whole is unclear at this point; rearrangements of the currently accepted phylogeny and resulting classification based solely on gill morphology are not recommended at this time.     

合浦珠母贝鳃的显微与超微结构

合浦珠母贝(Pinctada fucata)是典型的滤食性瓣鳃类动物,也是我国重要的海水珍珠养殖贝类。本研究用光学显微镜、扫描电镜和透射电镜观察了合浦珠母贝鳃的显微和超微结构。结果表明,合浦珠母贝鳃结构属于异丝鳃型,左右两侧各2个鳃瓣,每个鳃瓣由内鳃瓣和外鳃瓣组成。鳃瓣由主鳃丝和普通鳃丝构成,主鳃丝在鳃瓣中主要起支架作用,每2根主鳃丝之间的9～12根普通鳃丝由"簇内连接"(intrabunchial junction)相连成簇。普通鳃丝之间通过"丝间连接"(interfilament junction)相连,丝间连接的上皮细胞与普通鳃丝的扁平细胞结构一样,为鳃的呼吸上皮。丝间连接的存在扩大了鳃的表面积,这种结构有助于进行气体交换。主鳃丝和普通鳃丝表面有前纤毛和侧纤毛,与食物运送和气体交换有关。普通鳃丝表面的纤毛为典型的"9+2"型微管结构。     

Filter feeding,deviations from bilateral symmetry,developmental noise,and heterochrony of hemichordate and cephalochordate gills

We measured gill slit fluctuating asymmetry (FA), a measure of developmental noise, in adults of three invertebrate deuterostomes with different feeding modes: the cephalochordate Branchiostoma floridae (an obligate filter feeder), the enteropneusts Protoglossus graveolens (a facultative filter feeder/deposit feeder) and Saccoglossus bromophenolosus (a deposit feeder). FA was substantially and significantly low in B. floridae and P. graveolens and high in S. bromophenolosus. Our results suggest that the gills of species that have experienced a relaxation of the filter feeding trait exhibit elevated FA. We found that the timing of development of the secondary collagenous gill bars, compared to the primary gill bars, was highly variable in P. graveolens but not the other two species, demonstrating an independence of gill FA from gill bar heterochrony. We also discovered the occasional ectopic expression of a second set of paired gills posterior to the first set of gills in the enteropneusts and that these were more common in S. bromophenolosus. Moreover, our finding that gill slits in enteropneusts exhibit bilateral symmetry suggests that the left‐sidedness of larval cephalochordate gills, and the directional asymmetry of Cambrian stylophoran echinoderm fossil gills, evolved independently from a bilaterally symmetrical ancestor.     

The sorting of food particles by Abra sp. (bivalvia: tellinacea)

The selection of food particles by Abra tenuis (Montagu), A. alba (Wood) and A. nitida (Müller) has been investigated.Material for ingestion smaller than 30μm is not selected according to size by A. tenius. Particles smaller than 0.5 μm are retained by the palliai organs and ingested but only particles larger than 1 μm appear to be retained with an efficiency approaching 100 %. The mesh size of the gill filter is found to be ≈ 3.0 × 0.5 μm.A. tenuis does not appear able to discriminate between particles smaller than 20 μm by their food value; however, relatively large silica particles which are devoid of food are partially rejected by the labial palps in favour of particles of similar size but having a bacterial coating. To a lesser extent the physical nature of particles seems to influence their selection by A. tenuis; clean angular particles are rejected in favour of clean rounded ones.Small, light particles appear to be transported on the gills directly to the mouth without coming into contact with the palps. Larger, heavier particles tend to drop from the gill to be caught by the palps which extend posteriorly to cup the entire ventral margin of the inner demibranch when the animal is feeding.The material ingested by A. alba is significantly finer than that taken into the mantle cavity indicating that the pallial organs actively select food by size. Selection of material for ingestion by size in A. nitida appears to be optional since only some of the animals examined had stomach contents significantly finer than material from the mantle cavity.     

Hydrodynamics of water flow in front of and through the gills of skipjack tuna

• 1.1. The structure of the gills of skipjack tuna (Katsuwonus pelamis) is reviewed and the pattern of water flow in front of, and through, the gills is described. The tuna system is attractive for analysis of this type because water flow is continuous rather than pulsatile and the gill system is more rigid than that of other fish. In addition, oxygen uptake rates are the extreme case (i.e. highest values) for water-breathers.
• 2.2. Flow into the slits between the gill bars is rectilinear and nearly uniform, and therefore irrigation at the gill sieve should be nearly uniform.
• 3.3. Reynolds numbers are so low that turbulent flow is unlikely and entrance effects are negligible.

     

Metallothionein-like proteins in the blue crab Callinectes sapidus: Effect of water salinity and ions

The effect of water salinity and ions on metallothionein-like proteins (MTLP) concentration was evaluated in the blue crab Callinectes sapidus. MTLP concentration was measured in tissues (hepatopancreas and gills) of crabs acclimated to salinity 30 ppt and abruptly subjected to a hypo-osmotic shock (salinity 2 ppt). It was also measured in isolated gills (anterior and posterior) of crabs acclimated to salinity 30 ppt. Gills were perfused with and incubated in an isosmotic saline solution (ISS) or perfused with ISS and incubated in a hypo-osmotic saline solution (HSS). The effect of each single water ion on gill MTLP concentration was also analyzed in isolated and perfused gills through experiments of ion substitution in the incubation medium. In vivo, MTLP concentration was higher in hepatopancreas than in gills, being not affected by the hypo-osmotic shock. However, MTLP concentration in posterior and anterior gills significantly increased after 2 and 24 h of hypo-osmotic shock, respectively. In vitro, it was also increased when anterior and posterior gills were perfused with ISS and incubated in HSS. In isolated and perfused posterior gills, MTLP concentration was inversely correlated with the calcium concentration in the ISS used to incubate gills. Together, these findings indicate that an increased gill MTLP concentration in low salinity is an adaptive response of the blue crab C. sapidus to the hypo-osmotic stress. This response is mediated, at least in part, by the calcium concentration in the gill bath medium. The data also suggest that the trigger for this increase is purely branchial and not systemic.     

Impact of seston characteristics on qualitative particle selection sites and efficiencies in the pseudolamellibranch bivalve Crassostrea gigas

To date, knowledge of the qualitative particle selection sites and conditions in the widely-distributed bivalve Crassostrea gigas is incomplete, having focussed either on heterogeneous particles, or on particles intentionally too large to enter the gill principal filament tracts. We used endoscope-directed sampling and the intact diatom-empty, cleaned frustule approach to unambiguously establish qualitative selection sites and the influence of seston quality (varying proportions of intact diatoms and empty, cleaned frustules) and quantity (particle loads) on the degree of qualitative selection. Normally-feeding oysters were presented test mixtures of the naturally-occurring Actinoptychus senarius (small enough to enter the gill principal filaments), and the potential selection sites (gill: dorsal and ventral collecting tracts; labial palps: anteriorly-deposited pseudofaeces), were sampled for comparison with the proportions and concentrations of the ambient medium. Qualitative selection was demonstrated at both the gills and labial palps. Gill selection efficiency was shown to be directly proportional to seston quality and quantity, using a technique independant of pseudofeces mucus content. The oyster gill is thus able to increase ingested food quality when environmental food quality is low and / or when seston concentrations are high, which is typical of oyster habitats. Palp selection efficiency was directly proportional to seston quality, but at the highest concentration tested, no qualitative selection was observed on the labial palps, probably due to overload on these smaller organs. The partial functional redundancy of these key processing organs in heterorhabdic species such as oysters and scallops may enhance their success in high-turbidity habitats.