Effects of salinity on chloride cells in the euryhaline cyprinodontid fish Rivulus marmoratus

Summary The ultrastructure and density of chloride cells in the gill, opercular epithelium, and opercular skin of the euryhaline self-fertilizing fish Rivulus marmoratus (Cyprinodontidae) were studied with electron and fluorescence microscopy. R. marmoratus raised from birth in 1, 50, 100, and 200% seawater were compared. Chloride cells from fish raised in each of the four salinities exhibited an invaginated pit structure at the apical crypt. Multicellular complexes were present in the 1% seawater group and in those fish raised in higher salinities where elaborate interdigitations were seen between cells. Chloride cells from gills of fish raised in 200% seawater had a significantly higher percentage of their cytoplasmic volume composed of mitochondria than did those from fish raised in 1% seawater (69.9% vs 37.4%). The opercular skin and opercular epithelium had the same density of chloride cells (4.2×10⁴-4.5×10⁴ chloride cells/cm²), and this number did not vary significantly with increased salinity. The opercular skin thus appears far more responsive to environmental salinity than the opercular epithelium. Chloride cells from the opercular epithelium of fish raised in 200% seawater were found to be 39% larger than those from fish raised in 1% seawater, whereas the chloride cells from the opercular skin of the 200% seawater group were 107% larger than those from the 1% seawater group.     

造纸废水对离体鱼头呼吸运动的影响

本文采用离体鱼头灌注法,以两个造纸厂的制浆造纸废水对147个鲤鱼头进行了人工灌流。结果表明:废水在低浓度(如4%以下)体积稀释液时,鱼头呼吸速率基本未产生影响,而以较高浓度的废水(如5%以上)稀释液灌流与不含废水的鸭绿江水源地水灌流的对照组鱼头比较,几乎均发生了显著性变化,即对鱼鳃盖运动产生了抑制作用,出现了Biot氏呼吸。以往学者们认为,造纸废水主要是由于水中溶解氧(DO)减少而使鱼类致死的,但本工作灌注液中已人工给予足够的DO,提示:有毒物质本身似已直接危及延髓呼吸中枢。 实验同时表明,离体鱼头灌注法可供环境保护部门应用于含多种有机毒性物质的制浆造纸废水的现场监测。     

Opercular development and ontogenetic re-organization in a direct-developing frog

The direct-developing frog, Eleutherodactylus coqui, has eliminated the tadpole stage from its ontogeny, and lacks many larval characters. We demonstrate that the dermal folds of E. coqui are homologous with the opercular folds of metamorphosing frogs. In both E. coqui and its metamorphic counterparts the opercular folds grow over the developing forelimb before perforating to free the entrapped limb. Opercular perforation in E. coqui occurs even in the absence of the forelimb but shows no signs of thyroid hormone dependence. The condensation of E. coqui development appears due to the excision of the extended larval period of developmental stasis. Analysis of opercular development, when viewed in conjunction with other developmental characters, suggests the ontogenetic period in the ancestral Eleutherodactylus life-history from which the tadpole was likely eliminated. Received: 7 October 1999 / Accepted: 17 January 2000     

Cellular and epithelial adjustments to altered salinity in the gill and opercular epithelium of a cichlid fish (Oreochromis mossambicus)

Morphological features of the gill and opercular epithelia of tilapia (Oreochromis mossambicus) have been compared in fish acclimated to either fresh water (FW) or hypersaline water (60 S) by scanning electron and fluorescence microscopy. In hyperosmoregulating, i.e., FW-acclimated, tilapia only those mitochondria-rich (MR) cells present on the filament epithelium of the gill were exposed to the external medium. After acclimation of fish to hypersaline water these cells become more numerous, hypertrophy extensively, and form apical crypts not only in the gill filament but also in the opercular epithelium. Regardless of salinity, MR cells were never found to be exposed to the external medium on the secondary lamellae. In addition, two types of pavement cells were identified having distinct morphologies, which were unaffected by salinity. The gill filaments and the inner operculum were generally found to be covered by pavement cells with microridges, whereas the secondary lamellae were covered exclusively by smooth pavement cells.     

暗纹东方鲀年龄鉴定的研究

用耳石、脊椎骨、鳃盖骨等识别和鉴定暗纹东方鲀(Takifugu obscurusAbe)的年龄,在描述其轮纹特征基础上,比较其在判读暗纹东方鲀年龄和生长特征上的异同与准确性。结果表明,耳石磨片上的轮纹特征明显、清晰且规律性强,是最好的年龄鉴定材料;脊椎骨轮纹也很清晰,但测量时有一定难度,也是较好的年龄鉴定材料;鳃盖骨上年轮较难判定,只能作为辅助材料。本文还对牙齿能否作为年龄鉴定材料进行了观测。     

Ventilatory frequency of Nile tilapia subjected to different stressors

Ventilatory frequency (VF) was investigated in the fish Nile tilapia, Oreochromis niloticus, subjected to confinement, electroshock or social stressor. Fish were allowed to acclimatize to tank conditions for 10 days (1 fish/aquarium). VF baseline was determined 5 days after adjustment had been started. At the 10th day of isolation, stressor effects on VF were assessed. The stressors were imposed during 60 min: pairing with a larger resident animal (social stressor), or gentle electroshock (AC, 20 V, 15 mA, 100 Hz for 1 min every 4 min), or space restriction (confinement). VF was quantified immediately after the end of the stressor imposition. Baseline of VF was not statistically different among groups. Social stressor clearly induced VF to increase, while an increased or decreased VF can be observed for both confinement and electroshock. However, fish tend to increase their VF in response to confinement and decrease in the case of electroshock. These results suggest that VF is a sensitive behavioural indicator for distinguishing stress responses in the fish Nile tilapia among different stressors.     

锌对离体鲤鱼头呼吸的抑制作用

本工作基于化学纤维工厂废水中硫酸锌含量的石超标而设计。采用改进的离体鱼头灌注法,以不同浓度的ＺｎＳＯ４．７Ｈ２Ｏ对８４个鲤鱼头进行了人工灌流,结果表明,锌的渔业水质安全下限似应以０．００２３ｍｇ／Ｌ（我国现行规定锌的渔业水质标准为０．１ｍｇ／Ｌ）为宜。     

The erectile cheek-spine apparatus in the bristlenose catfish Ancistrus (Loricariidae, Siluriformes), and its relation to the formation of a secondary skull roof

In the South American catfish family Loricariidae, the opercle has been decoupled from the lower jaw, and has also lost its function in expiration. While many loricariid species have a small and slightly mobile opercle with reduced opercular musculature, within the hypostomine subfamily a novel opercular mechanism has developed that erects a tuft of enlarged odontodes anterior to the opercle. This defensive mechanism is examined in Ancistrus cf. triradiatus. The opercle has a prominent anterior process and the orientation of the reinforced articulation hinge to the hyomandibular bone has shifted. The opercular musculature is well developed, with a hypertrophied dilatator operculi that extends deep inside the skull roof bones and toward the midline, over the brain, but below the superficial skull roof. Hence the frontal, sphenotic, parieto-supraoccipital and compound pterotic bones consist of a dorsal, superficial part and a deeper part separating the brain from the muscle: two functional skull roofs are thus formed. The impact on the path of the cranial sensory canals is substantial, moving canals away from the skull surface. Hypertrophy of cranial muscles is known from many teleosts, but the invasion of such large muscles into the skull, which is drastically modified and literally hollowed out, has never been described before. These cranial modifications are greater in males than in females, related to the territorial behavior of the former, in which the erectile spines are usually used.     

大鳞裂峡鲃的年轮特征

大鳞裂峡鲃(Hampala macrolepidota)隶属于鲤形目(Cypriniformes)、鲤科(Cyprinidae)、鲃亚科(Barbinae)、裂峡鲃属(Hampala),在我国属濒危鱼类[1]。国外分布于泰国、印度尼西亚等,国内仅分布于澜沧江下游云南西双版纳自治州勐腊县境内支流[2]。     

Feeding activity and opercular pressure transients in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis> L.): application to feeding management in fish farming

Ecological and economical sustainability of marine aquaculture operations depend on proper feeding management. Feed wastage from overfeeding is a source of pollution, represents futile use of precious marine resources, and undermines the economic viability of operations. Additionally, underfeeding reduces growth and fish welfare. Finding an optimal feeding regime in terms of temporal and spatial distribution of the feed ration require intimate knowledge of the individual feeding behaviour of fish sustaining intensive culturing conditions. Fish telemetry has proved to be a valuable tool for studying spatial behaviour in sea cages, however there are currently no practical methods available with respect to detection of actual feed intake in fish on the individual level. The present study investigates pressure transients arising in the opercular cavity of farmed Atlantic salmon (Salmo salar L.) in connection with feeding, and whether such measurements can serve as an indication of feed ingestion. A technical solution to the sensing problem based on a differential pressure transducer is presented along with typical pressure signal traces obtained during feeding in a hard wire tank experiment. Measurements showed considerable variation of sub-ambient pressure transients (1.5 kPa ± 0.95) and their duration (519 ms ± 117), suggesting that the fish modulates its strike intensity depending on the particular feeding situation. Despite variations in scale, opercular pressure waveforms have distinct structural features that repeat between feeding instants. From a signal processing point of view waveforms provide sufficient information with respect to isolation and detection of feeding incidents, which is important with respect to a potential implementation of the sensing principle in a telemetry tag design. Issues regarding development and application of a telemetry system based on this sensing principle are discussed.