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1.
Deep-sea benthic communities derive their energetic requirements from overlying surface water production, which is deposited at the seafloor as phytodetritus. Benthic invertebrates are the primary consumers of this food source, with deep-sea fish at the top of the trophic hierarchy. Recently, we demonstrated with the use of baited cameras that macrourid fish rapidly respond to and feed vigorously on large plant food falls mimicked by spinach (Jeffreys et al., 2010). Since higher plant remains are scarce in the deep-sea, with the exception of canyons, where terrestrial material has been observed, these results led us to ask if a more commonly documented plant material i.e. phytodetritus might form a food source for deep-sea fish and mobile scavenging megafauna. We simulated a phytodetritus dump at the seafloor in two contrasting environments (1) the NE Atlantic where carpets of phytodetritus have been previously observed and (2) the oligotrophic western Mediterranean, where the deposition of phytodetritus at the seafloor is a rare occurrence. We recorded the response of the scavenging fauna using an in situ benthic lander equipped with baited time-lapse cameras. In the NE Atlantic at 3000 m, abyssal macrourids and cusk-eels were observed ingesting the phytodetritus. The phytodetrital patch was significantly diminished within 2 h. Abundance estimates calculated from first arrival times of macrourids at the phytodetrital patch in the Atlantic corresponded with abundance estimates from video-transect indicating that fish were attracted to the scent of phytodetrital bait. In contrast to this, in the western Mediterranean at 2800 m a single macrourid was observed investigating the phytodetrital patch but did not feed from it. The phytodetrital patch was significantly diminished within 6.5 h as a result of mainly invertebrate activity. At 1900 m, Lepidion lepidion was observed near the lander and the bait, but did not feed. The phytodetrital patch remained intact until the end of the experiment. In the deployments in the Mediterranean abundance estimates from first arrival times at the bait, corrected for their body size, were lower than estimates obtained from video-transects and trawl catches. This suggests that the Mediterranean fish were not readily attracted to this food source. In contrast, invertebrates in the Balearic Sea were observed ingesting the phytodetritus bait despite the rare occurrence of phytodetritus dumps in the Mediterranean. Stable isotope values of the fish at both study sites, set within the context of the benthic food web, did not demonstrate a strong trophic link to phytodetritus. Fatty acid profiles of these fish indicated a strong link between their lipid pool and primary producers i.e. phytoplankton, which may be attributed to trophic transfer. The usefulness of fatty acid biomarkers in ascertaining deep-sea fish diets is discussed. Our study suggests that the abyssal grenadier C. armatus on the Atlantic Iberian margin is attracted to phytodetritus. However the exact contribution of this food source to the diet of macrourids in this area remains unresolved.  相似文献   

2.
Scavengers perform an important role in deep-sea ecosystems, recycling carrion. However, scavenged material can be difficult to discern from predation. The synaphobranchid eel Diastobranchus capensis Barnard, 1923, is common bycatch in deep-water fisheries for orange roughy (Hoplostethus atlanticus Collett, 1889) in New Zealand waters. Despite anecdotal reports of scavenging in D. capensis, their ecology and feeding are little known. Scavenged material was estimated to be approximately 39 per cent (by weight) of the diet of D. capensis from northeastern Chatham Rise, New Zealand, from water depths of 1062–1196 m. Scavenged material was defined as fragmentary food items from animals and plants either not normally available to the eel, or from animals larger than the eel consuming them (e.g., fish heads and tails, spent squid spermatophores, beaks and tentacle crowns, and seaweed). D. capensis were primarily piscivorous, with the diet supplemented by squid, natant decapods and mysids. The weight or number of food items did not increase with the size of the eel, nor was there any major ontogenetic shift in the composition of the diet. D. capensis probably plays an important role in mid-slope communities, recycling carrion.  相似文献   

3.
We conducted an in situ feeding experiment using 13C-labeled unicellular algae in Sagami Bay, Japan (water depth, 1450 m), in order to understand the fate of lipid compounds in phytodetritus at the deep-sea floor. We examined the incorporation of excess 13C into lipid compounds extracted from bulk sediments and benthic foraminiferal cells. 13C-enriched fatty acids derived from 13C-labeled algae were exponentially degraded during 6 days of incubation in the sediment. Subsequent enrichments in 13C in sedimentary n-C15, anteiso-C17, and C17 fatty acids indicated the microbial degradation of algal material and production of bacterial biomass in the sediment. We observed the incorporation of 13C-labeled algal phytol and fatty acids into foraminiferal cells. The compositions of 13C-labeled algal lipids in foraminiferal cells were different from those in the bulk sediments, indicating that foraminiferal feeding and digestion influenced the lipid distribution in the sediments. Furthermore, some sterols in Globobulimina affinis (e.g., 24-ethylcholesta-5,22-dien-3β-ol, 24-ethylcholest-5-en-3β-ol, and 23,24-dimethylcholesta-5,22E-dien-3β-ol) were newly produced via the modification of dietary algal sterols within 4–6 days. In addition to the effects of bacteria, feeding by benthic foraminifera can result in a significant reorganization of the composition of organic matter and influence benthic food webs and carbon cycling at the deep-sea floor.  相似文献   

4.
The deep sea has been shown to exhibit strong depth zonation in species composition and abundance. Examination of these patterns can offer ecological insight into how organisms adapt and respond to changing environmental parameters that co-occur with depth. Here we provide the first tropical study on bathymetric zonation and other depth-related trends (size, abundance, and species richness) spanning shelf to abyssal depths of scavenging megafauna. Baited time-lapse free-vehicle cameras were used to examine the deep-sea benthic and demersal scavenging communities of the Hawaiian Islands, an area for which the biology and ecology have remained poorly studied below 2000 m. Twenty-two deployments ranging in depth from 250 to 4783 m yielded 37 taxa attracted to bait, including the first known occurrence of the family Zoarcidae in the Hawaiian Islands. Cluster analysis of Bray–Curtis similarity of species peak abundance (nmax) revealed four main faunal zones (250–500, 1000, 1500–3000, and ?4000 m) with significant separation (ANOSIM, global R=0.907, p=0.001) between designated depth groups. A major faunal break was identified at the 500–1000 m transition where species turnover was greatest, coinciding with the location of the local oxygen minimum zone. Dominance in species assemblage shifted from decapod crustaceans to teleosts moving from shallow to deeper faunal zones. Significant size differences in total length with depth were found for two of the four fish species examined. A logarithmic decline was observed in scavenger relative abundance with depth. Evidence of interaction between scavenging species was also noted between Synaphobranchus affinis and Neolithodes sp. (competition) and Histiobranchus sp. and aristeid shrimp (predation), suggesting that interactions between scavengers could influence indices of abundance generated from baited camera data.  相似文献   

5.
The bait-attending fauna of the abyssal-hadal transition zone of the Kermadec Trench, SW Pacific Ocean (4329-7966 m), was investigated using a baited camera and a trap lander. The abyssal stations (4329-6007 m) revealed a typical scavenging fish community comprising macrourids and synaphobranchid eels, as well as natantian decapods. At the hadal depths of 7199 and 7561 m, the endemic liparid Notoliparis kermadecensis was observed aggregating at the bait reaching surprisingly high numbers of 5 and 13, respectively. A total of 3183 invertebrate samples were collected (mean deployment time=16 h) of which 97.8% were of the order Amphipoda (nine families, 16 species). Ten of the amphipod species represent new distributional records for the Kermadec Trench and the New Zealand Exclusive Economic Zone; this includes the shallowest known record of the endemic hadal amphipod Hirondellea dubia (6000, 6007 m). Using amphipods to statistically examine the compositional change across the abyssal-hadal boundary, an ecotone between depths <6007 and >6890 m was found, indicating that there is an ecologically distinct bait-attending fauna in this trench.  相似文献   

6.
Interlinked mangrove–seagrass ecosystems are characteristic features of many tropical coastal areas, where they act as feeding and nursery grounds for a variety of fishes and invertebrates. The autotrophic carbon sources supporting fisheries in Gazi bay (Kenya) were studied in three sites, two located in the tidal creeks flowing through extensive mangrove forests, another site located in the subtidal seagrass meadows, approximately 2.5 km away from the forest. Carbon and nitrogen stable isotope composition of 42 fish species, 2 crustacean species and a range of potential primary food sources (e.g., mangroves, seagrasses and epiphytes, macroalgae) were analysed. There was considerable overlap in the δ13C signatures between fish (−16.1 ± 2.1‰), seagrasses (−15.1 ± 3.0‰), seagrass epiphytes (−13.6 ± 3.3‰), and macroalgae (−20.4 ± 3.1‰). Nevertheless, the signatures for most primary producers were sufficiently distinct to indicate that the dominant carbon sources for fish were mainly derived from the seagrass and their associated epiphytic community, and possibly macroalgae. Mangrove-derived organic matter contributes only marginally to the overall fish food web. Carbon supporting these fish communities was derived directly through grazing by herbivorous and some omnivorous fishes, or indirectly through the benthic food web. Fishes from the mangrove creeks had distinctly lower δ13C signatures (−16.8 ± 2.0‰) compared to those collected in the adjacent seagrass beds (−14.7 ± 1.7‰). This indicated that these habitats were used as distinct sheltering and feeding zones for the fishes collected, with minimal degree of exchange within the fish communities despite their regular movement pattern.  相似文献   

7.
A stable carbon isotope approach was taken to identify potential organic matter sources incorporated into biomass by the heterotrophic bacterial community of Florida Bay, a subtropical estuary with a recent history of seagrass loss and phytoplankton blooms. To gain a more complete understanding of bacterial carbon cycling in seagrass estuaries, this study focused on the importance of seagrass-derived organic matter to pelagic, seagrass epiphytic, and sediment surface bacteria. Particulate organic matter (POM), seagrass epiphytic, seagrass (Thalassia testudinum) leaf, and sediment surface samples were collected from four Florida Bay locations with historically different organic matter inputs, macrophyte densities, and primary productivities. Bulk (observed and those reported previously) and compound-specific bacterial fatty acid δ13C values were used to determine important carbon sources to the estuary and benthic and pelagic heterotrophic bacteria. The δ13C values of T. testudinum green leaves with epiphytes removed ranged from −9.9 to −6.9‰. Thalassia testudinum δ13C values were significant more enriched in 13C than POM, epiphytic, and sediment samples, which ranged from −16.4 to −13.5, −16.2 to −9.6, and −16.7 to −11.0‰, respectively. Bacterial fatty acid δ13C values (measured for br14:0, 15:0, i15:0, a15:0, br17:0, and 17:0) ranged from −25.5 to −8.2‰. Assuming a −3‰ carbon source fractionation from fatty acid to whole bacteria, pelagic, epiphytic, and sediment bacterial δ13C values were generally more depleted in 13C than T. testudinum δ13C values, more enriched in 13C than reported δ13C values for mangroves, and similar to reported δ13C values for algae. IsoSource mixing model results indicated that organic matter derived from T. testudinum was incorporated by both benthic and pelagic bacterial communities, where 13–67% of bacterial δ13C values could arise from consumption of seagrass-derived organic matter. The IsoSource model, however, failed to discriminate clearly the fraction of algal (0–86%) and mangrove (0–42%) organic matter incorporated by bacterial communities. These results indicate that pelagic, epiphytic, and sediment surface bacteria consumed organic matter from a variety of sources. Bacterial communities incorporated consistently seagrass-derived organic matter, the dominant macrophyte in Florida Bay, but seagrass δ13C values alone could not account fully for bacterial δ13C values.  相似文献   

8.
Surveys were undertaken on the shallow Bermuda marine platform between 2006 and 2008 to provide a baseline of the distribution, condition and environmental characteristics of benthic communities. Bermuda is located in temperate latitudes but coral reefs, tropical seagrasses and calcareous green algae are common in the shallow waters of the platform. The dominant organisms of these communities are all living at or near their northern latitudinal range limits in the Atlantic Ocean. Among the major benthic autotrophs surveyed, seagrasses were most restricted by light availability. We found that the relatively slow-growing and long-lived seagrass Thalassia testudinum is restricted to habitats with much higher light availability than in the tropical locations where this species is commonly found. In contrast, the faster growing tropical seagrasses in Bermuda, Syringodium filiforme, Halodule sp. and Halophila decipiens, had similar ecological compensation depths (ECD) as in tropical locations. Increasing sea surface temperatures, concomitant with global climate change, may either drive or allow the poleward extensions of the ranges of such tropical species. However, due to latitudinal light limitations at least one abundant and common tropical autotroph, T. testudinum, is able to occupy only shallower depths at the more temperate latitudes of Bermuda. We hypothesize that the poleward shift of seagrass species ranges would be accompanied by restrictions to even shallower depths of T. testudinum and by very different seagrass community structures than in tropical locations.  相似文献   

9.
Coryphaenoides armatus plays a fundamental role in the dispersal of organic matter on the deep-sea floor by consuming food-falls. The use of baited cameras to study population parameters (e.g. abundances and size frequencies) assumes that members of this species follow odour plumes directly to bait, appear immediately in the field of view, and depart as predicted by optimal foraging theory. Described here are behaviours to the contrary observed during the operation and development of more complex baited camera systems. Of the 247 C. armatus observed by a video lander, 72.5% of the fish explored the structure whilst only 6% fed, and 21.5% were indifferent. This exploratory behaviour increased individual staying time by 38.4% compared to those that just fed. Experiments with several models of in situ fish respirometry lander showed the importance of both equipment design, and an understanding of the behaviour of the target animals in maximising capture success. These results show how previously unexpected aspects of behaviour by C. armatus can greatly affect the chances of capturing members of this species and influence the results of baited camera experiments.  相似文献   

10.
To investigate the trophic ecology of two of the dominant families of deep-sea fish (Macrouridae and Moridae) fatty acid and stable isotope analyses were applied to liver and muscle samples of five abundant species from the NE Atlantic. In conjunction with stomach content data these methods made it possible to identify differences in feeding strategies between the five study species as well as variation in feeding in relation to increasing depth and body size. Biomarkers identified strong similarities between Coryphaenoides armatus and Antimora rostrata though differences were found associating C. armatus more with the benthic food web whereas A. rostrata showed stronger links to the pelagic food web. While Lepidion eques was classified as a species linking benthic and benthopelagic food webs, both fatty acid and stable isotope data suggested that Coryphaenoides guentheri fed on an exclusively benthic diet. Coryphaenoides rupestris on the other hand were largely dependent on a copepod-based food web. Ontogenetic changes in feeding were found for both A. rostrata and C. armatus with the indication of a switch from active predation to scavenging occurring with increasing body size. Biomarkers also reflected the seasonal influx from the photic zone though changes were species-specific and probably reflected the variation in prey availability and abundance in response to these inputs. Our findings have thus demonstrated that the combined use of these biomarkers can elucidate trophic specialisations in situations where conventional methods alone previously provided insufficient data.  相似文献   

11.
山东半岛东端以岩基海岸为主,而浅海多为岩礁底质,适宜大型藻类生长。为探究该海域的大型藻类群落结构特征,于2018年11月(秋)、2019年2月(冬)、5月(春)和8月(夏)对山东荣成马山里海域的三个典型生境(草床区、天然礁区和泥沙区)中的大型藻类进行了调查。结果显示：三种生境共鉴定出大型藻类23种,其中红藻门15属15种,褐藻门3属4种,绿藻门3属4种。物种数最高值出现在天然礁区(22种),最低值出现在泥沙区(12种)。生物量最高值为春季草床区(1567.44±21.29)g.m-2、最低值为秋季的泥沙区(594.45±107.06)g.m-2。大型藻类优势种在不同生境、不同季节不同：草床生境为小珊瑚藻,在四个季节中均占绝对优势;礁区为绿藻向红藻、褐藻变化;泥沙区为从红藻到褐藻变化。Pielow均匀度指数的最高值在三个生境中相近且均出现在冬季;多样性指数最高值、最低值分别出现在礁区与泥沙区;Margalef丰富度指数的最高值出现在秋季的礁区,而最低值出现在夏季的泥沙区;聚类与排序结果表明,大型藻类群落结构在不同生境不同季节差异都显著。结果表明,生境特征和季节性变化是影响底栖大型海藻群落结构的主要因素。  相似文献   

12.
Abstract. The benthic flora of the limestone (20%) and sand (80%) substrates typical of intermediate depths on the west coast of Florida was sampled using quadrats over a three year period. Twenty seven taxa of macroscopic algae and one seagrass, Halophila decipiens , were collected. No plants were found during February of two consecutive years. The biomass and available energy ranged from 0 (winter) to 12.4g dry weight and 128 kJ (summer) per 25cm: on the limestone outcroppings and from 0 to 4.4g dry weight and 43 kJ for the sand substrate. The flora was seasonal with no dominant macroscopic algae occurring throughout the year. The flora of the intermediate depths is subjected to abiotic disturbances and is rudcral in nature. Thus, secondary production in the extensive intermediate depths along the west coast of Florida must depend more on the inshore, shallow water seagrass communities for primary production.  相似文献   

13.
Deep-sea ecosystems are fragile yet diverse habitats that are sensitive to disturbance. In the northern Gulf of Mexico deepwater extraction of hydrocarbons led to the accidental release of four million barrels of oil from the Macondo wellhead in 2010. The release of oil combined with the addition of dispersant at depth and the resulting delivery of oiled “marine snow” led to dramatic disruptions of diversity and ecosystem services within the near field deep-sea benthic communities. Analysis of the biological trait diversity of the surrounding megabenthos reveals notable loss of traits that may explain the stunted recovery of communities within 2 km of the wellhead. The present megafauna show complete loss of some traits relating to tier, motility, and feeding mechanisms. Functional evenness was higher than in surveyed unaffected sites, highlighting some loss of trait space, reflecting increasing abundances of scavengers and the loss of sessile invertebrates. Loss of biological traits that aid in ecosystem resilience has impeded recovery of benthic communities severely impacted by the Deepwater Horizon oil spill.  相似文献   

14.
Deep-sea benthic ecosystems are sustained largely by organic matter settling from the euphotic zone. These fluxes usually have a more or less well-defined seasonal component, often with two peaks, one in spring/early summer, the other later in the year. Long time-series datasets suggest that inter-annual variability in the intensity, timing and composition of flux maxima is normal. The settling material may form a deposit of “phytodetritus” on the deep-seafloor. These deposits, which are most common in temperate and high latitude regions, particularly the North Atlantic, evoke a response by the benthic biota. Much of our knowledge of these responses comes from a few time-series programmes, which suggest that the nature of the response varies in different oceanographic settings. In particular, there are contrasts between seasonal processes in oligotrophic, central oceanic areas and those along eutrophic continental margins. In the former, it is mainly “small organisms” (bacteria and protozoans) that respond to pulsed inputs. Initial responses are biochemical (e.g. secretion of bacterial exoenzymes) and any biomass increases are time lagged. Increased metabolic activity of small organisms probably leads to seasonal fluctuations in sediment community oxygen consumption, reported mainly in the North Pacific. Metazoan meiofauna are generally less responsive than protozoans (foraminifera), although seasonal increases in abundance and body size have been reported. Measurable population responses by macrofauna and megafauna are less common and confined largely to continental margins. In addition, seasonally synchronised reproduction and larval settlement occur in some larger animals, again mainly in continental margin settings. Although seasonal benthic responses to pulsed food inputs are apparently widespread on the ocean floor, they are not ubiquitous. Most deep-sea species are not seasonal breeders and there are probably large areas, particularly at abyssal depths, where biological process rates are fairly uniform over time. As with other aspects of deep-sea ecology, temporal processes cannot be encapsulated by a single paradigm. Further long time-series studies are needed to understand better the nature and extent of seasonality in deep-sea benthic ecosystems. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

15.
We have compared the distribution of mesopelagic, benthopelagic and benthic fauna between two areas: one on the continental side of the Catalan Sea (cCS: northwestern Mediterranean) and one to the SW of the Balearic Islands (SWB: southwestern Mediterranean) at depths between 147 and 2266 m. Based on 88 bathyal fish and crustaceans (Decapoda and Peracarida) dominant in these communities, we compared the maximum depth of occurrence (MDO) of (upper) middle-slope species and the minimum depth of occurrence (mDO) of lower-slope dwelling species. Mid-slope fish, decapods, peracarids and, within the latter, amphipods and cumaceans had a deeper MDO in the cCS than in the SWB. Depth differences between MDO of species were significant for all taxa, except isopods. In the same way, lower slope fish and decapods had a shallower mDO in the SWB than in the cCS. Within peracarids, the dominant taxon (amphipods) also followed this trend. Depth differences in mDO of species between the areas were significant for decapods and for amphipods (not for fish, nor all peracarids nor cumaceans). In summary, most taxa showed a deeper depth distribution of middle-slope species in the cCS, and a shallower depth distribution of lower-slope dwelling species in the SWB. This suggests that the whole community, from small detritus-feeders (peracarids) to top predators (fish) have a similar response to a common signal. Much basic information on the biology and possible environmental factors affecting deep-sea species distribution is not available, so causes of the trends demonstrated here cannot be fully evaluated. In spite of these obvious limitations, we have shown that (1) mesopelagic decapods (e.g., Gennadas elegans and Sergia robusta), with a higher dependence upon primary sources of food close to the surface primary production, showed greater differences in their mDO between the areas than benthopelagic (e.g., Acanthephyra eximia, Nematocarcinus exilis) and benthic (e.g., Stereomastis sculpta, Munida tenuimana, Geryon longipes) species, and (2) fish at lower trophic levels, deduced from fractional trophic levels, showed higher differences in the MDO than fish at higher trophic levels. Trophic position of species in food webs seems the most important factor affecting the distributional differences between contrasting areas.  相似文献   

16.
The benthic macroinvertebrates of the Nakdong River estuary were sampled at three different habitats: two salt marsh (Scirpus triqueter and Phragmites australis) beds and a bare intertidal flat. Fishes were sampled in the main channel. The trophic importance of marsh vascular plants, microphytobenthos, and riverine and channel particulate organic matter to macroinvertebrate and fish production was studied using stable carbon and nitrogen isotope tracers. There was a dramatic change in coverage of macrophytes (salt marshes and seagrass) after the construction of an estuarine barrage in 1987 in the Nakdong River estuary, with the S. triqueter bed increasing, the P. australis bed decreasing, and Zostera marina habitats being nearly lost. Although the invertebrate δ13C were within a narrower range than those of the primary producers, the values varied considerably among consumers in these habitats. However, the isotope signatures of consumers showed similarities among different habitats. Cluster analysis based on their isotopic similarity suggested that the isotope variability among species was related more to functional feeding groups than to habitats or taxonomic groups. While δ13C values of suspension feeders were close to that of the channel POM (mainly phytoplankton), other benthic feeders and predators had δ13C similar to that of microphytobenthos. Isotopic mixing model estimates suggest that algal sources, including microphytobenthos and phytoplankton, play an important role in supporting the benthic food web. Despite the huge productivity of emergent salt marshes, the contribution of the marsh-derived organic matter to the estuarine food webs appears to be limited to some nutrition for some invertebrates just within marsh habitats, with little on the bare intertidal flats or in the channel fish communities. Isotope signatures of the channel fishes also confirm that algal sources are important in supporting fish nutrition. Our findings suggest that benthic and pelagic microalgae made a large contribution to consumer diets, while marsh plants may not have a large role in supporting food webs in this estuarine system.  相似文献   

17.
Many deep-sea animals derive part of their nutrition from rare and unpredictable food falls. However, traits that allow organisms inhabiting the sea floor to exploit carrion are poorly understood. We found in laboratory experiments that hagfish (Eptatretus stouti), gastropods (Neptunea amianta) and amphipods (Orchomene obtusus) survived extended periods of starvation, in some cases for more than a year. When exposed to odors emitted from carrion, most individuals of E. stouti and O. obtusus began searching for food within seconds, whereas none responded to the scent of the live prey. In contrast, the slow crawling N. amianta readily consumed carrion but showed no apparent response to any odor solutions tested. Because more motile animals exhibited lower thresholds for response to signal molecules, sensitivity to chemical cues appears related to species mobility. Hagfish were also found to defend carrion from some competitors by releasing slime when feeding. Though varying dramatically in size, morphology, locomotive ability, and phylogeny, these three species all possess traits well suited for a scavenging lifestyle.  相似文献   

18.
The deep-sea grenadier fishes (Coryphaenoides spp.) are among the dominant predators and scavengers in the ocean basins that cover much of Earth's surface. Baited camera experiments were used to study the behaviour of these fishes. Despite the apparent advantages of rapidly consuming food, grenadiers attracted to bait spend a large proportion of their time in prolonged periods of non-feeding activity. Video analysis revealed that fish often adopted a head-down swimming attitude (mean of 21.3° between the fish and seafloor), with swimming velocity negatively related to attitude. The fish also swam around and along vertical and horizontal structures of the lander with their head immediately adjacent to the structure. We initially hypothesised that this behaviour was associated with the use of the short chin barbel in foraging. Barbel histology showed numerous taste buds in the skin, and a barbel nerve with about 20,000 axons in adult fish. A tracing experiment in one undamaged animal revealed the termination fields of the barbel neurons in the trigeminal and rhombencephalic regions, indicating both a mechanoreceptory and a gustatory role for the barbel. Our conclusion was that olfactory foraging becomes ineffective at close ranges and is followed by a search phase using tactile and gustatory sensing by the barbel. The development of this sensory method probably co-evolved alongside behavioural changes in swimming mechanics to allow postural stability at low swimming speeds.  相似文献   

19.
Seagrass grazing by fish was measured in a large seagrass-dominated temperate bay (Geographe Bay, Western Australia) to examine whether: (1) seagrass herbivory occurs; (2) the level of herbivory is influenced by nitrogen in seagrass leaves; and (3) how herbivory and herbivorous fish communities vary with water depth and seagrass species. Species and abundance of fish and herbivore bite marks on seagrass leaves were recorded from diver surveys of 23 sites of varying depth ranging from 1 m to 18 m. Posidonia sinuosa, Posidonia coriacea, Amphibolis griffithii, and Amphibolis antarctica seagrass leaves were collected, dried and analysed for total nitrogen. Evidence for low levels of seagrass grazing was found at over half the sites surveyed, though high levels of grazing were recorded at only one site. An east–west pattern was observed in the location of grazed sites and of herbivorous fish species that corresponded with the general prevalence of patch reefs, indicating that reef associated fish assemblages may be responsible for the observed grazing. Total nitrogen was elevated in seagrass leaves associated with drains, although increased nitrogen was not associated with increased grazing. While grazing was recorded in this temperate seagrass meadow, the abundance of herbivorous fish was low and the amount of biomass removed by them was small compared to the balance of the meadow remaining, and to seagrass grazing studies elsewhere.  相似文献   

20.
南海深海鱼类的初步报告   总被引：1，自引：0，他引：1  
南海在我国濒临的四个海中面积最大，而其大陆架宽度则较狭窄，水深在200米以上的深海水域相当广阔。我国过去关于南海深海鱼类的研究报道极少，1962年《南海鱼类志》中曾记载过少数深海鱼类，但具有确切深度记录的仅有8种。在国外文献中，Gilbert和Hubbs(1920), Schultz(1938), Abe(1974 , 1975, 1976 )等曾报道过数种。 本文材料是1959-1960年在海南岛以东海域，水深200-1100米进行底栖生物拖网时所获得的标本。鉴定结果，共71种，分隶于37科，12目，其中34种为我国新记录，7种是我国在南海首次记录。 文内凡是我国新记录的种均有形态描述，并附有外形图,有些种作了分类上的讨论；对我国有过记录的种，只记有地理分布和标本采集记录。此外，就现有资料并参考有关深海鱼类文献，对这些种类的地理分布和深度分布也作了初步分析。由于调查范围较小，拖网次数不多，本文仅为南海鱼类区系提供了一些初步资料。丰富的南海深海鱼类区系，随着我国海洋调查事业的发展，还有待进一步深入研究。  相似文献   

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