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1.
This taxon is distinguished from other Ergasilidae by having only three pairs of legs, and a well‐developed hook on the penultimate joint of the second antenna abutting against the claw‐like terminal segment. A. amplexus has been reported from Anguilla australis, A. dieffenbachii, Perca fluviatilis, Carassius auratus, Retropinna retropinna, Physiculus bachus, Galaxias maculatus, Arripis trutta, Rhombosolea leporina, R. retiaria, and R. plebeia from Lake Ellesmere, near Christchurch, and from Anguilla australis from Makara River near Wellington. Both localities are euryhaline.  相似文献   

2.
The present note deals with the exact analytical solution of thermal bending of clamped, anisotropic, elliptic plates in the case where the thermal field is given by an expression of the type T(x,y,z)=z(Ax2+Cxy+By2).The problem is of basic interest in some ocean and mechanical structural systems since anisotropic materials are commonly used in those fields. Obviously the case of an orthotropic material constitutes a particular situation of the problem under study.  相似文献   

3.
Obelia is used in many zoology textbooks to exemplify the Hydrozoa life cycle. The body plan of Obelia medusae, however, is unique among the Hydrozoa. Contrary to all other hydromedusae, Obelia medusae do not derive from a medusary nodule, have neither a velum nor a subumbrellar cavity, the umbrella is flat, and swimming is achieved by umbrellar flapping and does not involve jet propulsion. The medusae of most Obelia species do not grow well on a diet of Artemia salina nauplii, the usual food for laboratory‐reared hydrozoans, and their rearing is often difficult. Previous observations reported that Obelia medusae might eat phytoplankton, driven to the mouth by movements of both the bell and the tentacles. To evaluate the efficiency of this feeding mechanism, we gave a suspension of genetically modified Escherichia coli expressing GFP to starved, newly released medusae of both O. dichotoma and Clytia hemisphaerica (the other campanulariid genus with medusae). Obelia medusae are able to concentrate bacteria in their gastric cavity, whereas Clytia medusae are not. Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous and filter‐feeding medusa, at least at the onset of its medusan life. As Cnidaria evolved before their current metazoan prey, their ancestral diet was probably microphagous. Obelia’s microphagous feeding habits could thus represent an example of the ancestral feeding condition in Cnidaria, but the apomorphic characters of its medusa suggest that its body architecture is not ancestral, and that its microphagy evolved relatively recently.  相似文献   

4.
Rhinochimaera africana, a new species (Chondrichthyes, Chimaeriformes, Rhinochimaeridae), is described from five specimens from the Western Cape and KwaZulu coasts of southern Africa and from the Moçambique Channel between South-Western Madagascar and Europa Island. Two more specimens are known from off the Agulhas Bank, South Africa. It differs from the partially sympatric R. atlantica Holt and Byrne, 1909, and the Pacific R. pacifica (Mitsukuri, 1895) in its darker coloration, longer, broader, paddle-shaped snout, tooth plates of different shape, a more elongate-oval clasper glans, a shorter caudal fin with very short filament, and possibly a smaller dorsal fin and longer interdorsal space. R. africana males are mature at 568 mm body length (BDL), females adolescent at 476 mm BDL. A large, probably adult female of 650 mm BDL is larger than any recorded R. atlantica or R. africana. Wounds on two specimens indicate possible "cookie-cutter" bites by squaloid sharks, and one has a possible bite by another Rhinochimaera. Data on R. pacifica and R. atlantica, including 45 specimens from off Namibia and South Africa, are presented for comparison with R. africana. Caudal tubercle counts of R. africana (40–46) are intermediate between those of R. atlantica (most with 19–33, rarely up to 43) and of R. pacifica (41–68, rarely as low as 25–34). Southern African R. atlantica agree with North Atlantic R. atlantica in having few caudal tubercles, but there is slight overlap with R. pacifica in the case of higher counts recorded for R. africana. The systematics and distribution of the genus Rhinochimaera are reviewed, a terminology and abbreviation system for morphometries presented, and a key to species provided. The separation of R. atlantica and R. pacifica on caudal tubercle counts is provisionally accepted but considered problematical until adequate samples of both species can be critically compared. Proportional measurements and counts of caudal tubercles were highly variable in Rhinochimaera, with much allometry in proportions with growth and much individual variation. Selected morphometrics are plotted to show allometric trends in proportions that separate R. africana from other species.  相似文献   

5.
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6.
The Nansei Islands in the southern Japanese Archipelago have 15 taxa of seagrasses from seven genera within three families. Seagrasses in this region grow on coral sands or coral debris in shallow reefs and on sandy or muddy substrata in the shallow areas of bays and inlets. Certain Halophila species grow in deep water off some islands. Enhalus acoroides only reaches to Ishigaki I. with winter sea water temperature (WST) at 23 °C, while Okinawa I. (WST at 21.6 °C) is the northern biogeographic limit for Halophila decipiens, H. okinawensis, H. major and H. gaudichaudii. Amami‐oshima I. (WST at 20.7 °C) is the northern border for Thalassia hemprichii, H. minor, H. ovalis, Cymodocea serrulata, Cymodocea rotundata, Syringodium isoetifolium, Halodule uninervis and Halodule pinifolia. Halophila mikii the sole seagrass collected from Yakushima I. (WST at 19.3 °C), is of volcanic origin. The distribution of tropical seagrasses in the Nansei Islands is clearly associated with the warm Kuroshio Current, WST and habitat availability. Zostera japonica is the only temperate species occurring in the region. Meadows of Z. japonica, H. ovalis and Halodule pinifolia have disappeared from certain localities in the Archipelago, due probably to human activities and natural siltation.  相似文献   

7.
Momentum and heat flux were measured with a sonic anemometer at the Marine Observation Tower in the port of ItÔ. Under unstable conditions (T w -T a =3C4C), using the eddy correlation method, results show thatCd=(1.2±0.3)×10–3 andCh=(1.5±0.3)×10–3 at 5.5 m above mean sea level except for the case of weak winds.An unexpected relationship betweenCd and (–z/L) was observed, that is,Cd decreases as (–z/L) increases. If roughness variation over the sea is taken into account, we can explain the decrease in the range of (–z/L) less than 1, but not in the range greater than 1. This is due to a strong instability effect and the change of roughness class, from moderately rough to smooth.  相似文献   

8.
Growth of the red gurnard, Chelidonichthys kumu (Lesson and Garnot), from Pegasus Bay, Canterbury, was measured during 1966–67. Otoliths were used as an indicator of fish growth; mean length‐at‐age data were obtained from back‐calculated fish lengths at the time of formation of successive annual rings in the otoliths. Growth in length was found to be adequately expressed by the von Bertalanffy growth equation :

lt = 52.0 [1 ‐ e‐0.406 (t‐o.291)]

(where lt is the fork length in cm at age t). The length: weight relationship was:

w = 78.56 × 10‐4 l 3.072

(where w is the weight in grams). From this relationship, growth in weight was described by the equation:

wt = 1469 [1 ‐ e‐0.406 (t‐0.291)]3.  相似文献   

9.
Ecosystem engineers can influence community and ecosystem dynamics by controlling resources, modifying the flow of energy or biomass, or changing physical characteristics of the habitat. Invasive hybrid cordgrass (Spartina alterniflora × Spartina foliosa) is an ecosystem engineer in salt marshes in San Francisco Bay, California, U.S.A. that raises intertidal elevations and may be either increasing C4 plant carbon input into food webs or tying up carbon in a form that is not usable by consumers. A manipulative experiment compared abundance, growth, and stable isotope (δ13C and δ15N) composition of the clam Macoma petalum (=M. balthica) among native marsh, hybrid Spartina, and mudflats in central San Francisco Bay. We found higher densities (individuals m−2) of M. petalum on mudflats compared to either native or hybrid Spartina (p < 0.001). Macoma petalum shell growth was significantly greater in mudflats than in either vegetation type in 2002 (p = 0.005) but not 2003. Differences in shell growth between native and hybrid Spartina were not significant. Stable isotope results showed differences between habitats in δ13C but not δ15N. Carbon signatures of M. petalum placed in Spartina were much more depleted than the isotopic signature of Spartina. Neither native nor hybrid Spartina appears to be a significant carbon source for M. petalum in San Francisco Bay, and we found no evidence that hybrid Spartina contributes carbon to M. petalum beyond what is provided by S. foliosa, despite the hybrid's much greater biomass. Our results show that loss of mudflat habitat, rather than increased input of C4 carbon, is the greatest effect of the invasion of hybrid Spartina on M. petalum.  相似文献   

10.
Abstract. Using an in situ observational approach, the food preferences among hard corals were examined for the two obligate coral‐feeding butterflyfishes Chaetodon austriacus and C. trifascialis in the Northern Red Sea, Gulf of Aqaba, Egypt. Chaetodon austriacus is a generalist coral feeder that feeds mainly on three genera of abundant hard corals (Acropora, Porites and Pocillopora). In contrast, C. trifascialis is a specialist coral feeder on Acropora spp. and Pocillopora verrucosa. In general, C. austriacus had a lower feeding rate than C. trifascialis (both species in the Northern Red Sea reefs had high feeding rates compared with other reefs). Ivlev's electivity index was calculated for the two species. This index shows that C. austriacus prefers Montipora and Pocillopora, and avoids Lobophyllia and Favites. On the other hand, C. trifascialis prefers Acropora valida and avoids Porites solida. Thus, the feeding preference and avoidance of these chaetodontids depend on both biting rate and food availability in the environment rather than on biting rate alone.  相似文献   

11.
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12.
Definitions are given for stages in the development of five species of Galaxias, family Galaxiidae, which have marine larvae.

Larvae of Galaxias maculates attenuates and G. brevipinnis are large, and those of G. fasciatus relatively small as they enter fresh water from the sea. Development as whitebait involves shrinkage by about 25% in total length; the head length, considered separately, shrinks by about 15%. The ratio of standard length to head length alters from the larval to the adult value before positive growth recommences. These features are probably similar for G. postvectis and G. argenteus

Minimum observed pigmentation is described for the late larvae of G m. attenuates, G. brevipinnis, and G. fasciatus and for early whitebait of these and of G. postvectis and G. argenteus Subsequent development of melanophores and of colour pattern is described and figured. Large melano‐phores along the lateral line distinguish early whitebait of G. m. attenuates, but no distinguishing feature of pigmentation has been found in other species until the juvenile pattern is apparent. This pattern is characteristic for each species, and it persists in adult G. m. attenuates. G. argenteus has distinct juvenile and adult patterns, the latter being developed in a second, superficial, layer of pigment cells. Adult G. postvectis develop a distinctive fin colour pattern unlike other New ‐Zealand Galaxias; the superficial pigment layer is without definite pattern. In adult G. brevipinnis this layer resembles the persistent juvenile pattern and the two layers combined give a reticulate appearance. In G. fasciatus the juvenile pattern persists and develops as the fish grow; the superficial pigment layer is present in adults but is not usually apparent.

Until now positive identification of whitebait has depended on colour pattern. Recently recorded identifications of unpigmented whitebait are shown to be misleading. A key is given for the identification of early and late whitebait using absolute measurements as an important character.  相似文献   

13.
A synopsis of the classification of the New Zealand Polyplacophora is presented. The name Lepidochitonidae is replaced by the earlier Callochitonidae, Plaxi‐phoridae by Mopaliidae, Aulacochitonidae by Schizochitonidae, and Cryptocon‐chidae by Acanthochitonidae.

Vaferichiton Iredale and Hull is treated as a subgenus of Aerilamma Hull. Lorica H. and A. Adams is used instead of its junior synonym Aulacochiton Shuttleworth. Lorica haurakiensis Mestayer is recorded from the Nukumaruan (Lower Pleistocene). Paricoplax profundior Dell is placed in Loricella Pilsbry. Icoplax chathamensis Dell is made the type species of a new subgenus of Anthochiton Localities in southern New Zealand for Notoplax cuneata (Suter) and Lorica haurakiensis are listed.  相似文献   

14.
A sediment core covering the last 145 kyrs was collected in the western subarctic Pacific (WSAP), and analyzed for Ba, U, Al, Sc, La, Yb, Th, biogenic opal (Opal) and organic carbon (Corg) as well as its isotopic ratio (δ13C). This study examined the change of past biological production in WSAP with multiple proxies, together with understanding the relation between Loess from the Asian continent and the biological production. The Loess content was estimated from the metal components, Al, Sc, La, Yb and Th. In this high latitude core (50°N), the Loess content was generally high during the glacial periods, but it was also high even in some interglacial periods. The excess amount of Ba relative to the detrital material composition, Baex, showed the best correlation with the Vostok δD (r = 0.72, p < 0.001), indicating that the biological production was lower in the glacial periods than in the interglacials. This corroborates the pervasive correlation between Baex in the polar region, WSAP and the Antarctic Sea, and Antarctic temperature, combined with previous research. This correlation might be explained by the stratification caused by cooling. In addition, the time variations of Baex in WSAP were similar to those of Baex in the Okhotsk Sea and of other proxies (Corg and Opal) in both the Okhotsk and the Bering Sea, indicating the spatial homogeneity of Baex in WSAP including proximal marginal seas. The Opal content was more weakly correlated with the Vostok δD (r = 0.46, p < 0.001) than Baex, reflecting that Opal in WSAP including proximal marginal seas was spatially heterogeneous compared to Baex. While both the Corg content and Uex, the excess amount of U relative to the detritus composition, were not positively correlated with the Vostok δD, they behaved similarly in the sediments. The positive correlation between δ13C and the Vostok δD (r = 0.42, p < 0.001), between δ13C and Baex (r = 0.60, p < 0.001) and between δ13C and Opal (r = 0.36, p < 0.01) indicates that δ13C in WSAP may give some information on the phytoplankton growth rate. There was not a significant correlation between the spatially homogeneous Baex in WSAP and Loess (r = − 0.16, p > 0.01), suggesting that the increase of biological production with the increase of Loess supply during the glacial periods did not occur.  相似文献   

15.
The life history of Plesionika edwardsi (Brandt, 1851) around the Canary Islands in the Eastern Central Atlantic was investigated, based on a total of 11 434 shrimps ranging in length between 8 and 40 mm carapace length (CL). The species carries out seasonal migrations; they concentrate in deep water during winter, move shallower in summer and return to deep water again in autumn. Ovigerous females occur throughout the year, but a spawning peak was determined between April and September. The size at maturity for females was approximately 26 mm CL. Shrimp size generally increased with increasing water depth. The growth parameters for males were L ∞ = 25.75 mm CL and K = 0.55 year?1, and L ∞ = 28.28 mm CL and K = 0.66·year?1 for females. The species displays the typical reproductive pattern of tropical pandalids and is dioecious.  相似文献   

16.
The abundance of a scyphomedusae, Aurelia aurita and Chrysaora melanaster, and a ctenophore, Bolinopsis mikado, in Tokyo Bay was investigated from 1995 to 1997. Aurelia aurita appeared throughout the year with a peak in abundance occurring from spring to summer. The average abundance and biomass during this period for the three successive years was 4.8, 43.8 and 3.2 ind. m−2, and 1.02, 10.0 and 0.42 gC m−2, respectively. The values in 1995 and 1997 were comparable with those previously reported for A. aurita abundance from 1990 to 1992. Values were very high in 1996, but the size composition of the bell diameter did not differ from other years, which suggested the absence of food limitation for A. aurita in 1996. C. melanaster was scarce over the survey period (<1.0 ind. m−2) while Bolinopsis mikado was more abundant during September to December, with maximum values of 172 ind. m−2 and 0.33 gC m−2 observed in December 1997. The weight-specific clearance rate for A. aurita on zooplankton (mainly copepods and their nauplii) was 0.16 ± 0.05 lgWW−1 h−1 (n = 13). Population clearance rate peaked from spring to summer, with average levels of 14.2%, 162% and 5.0% day−1 obtained from spring to summer for respective years. Population clearance rates for B. mikado, calculated based on minimum carbon requirements, was 7.1% day−1 in December 1997. Consequently, the trophic role of gelatinous zooplankton as predators in Tokyo Bay is important all the year round, considering the high impact of A. aurita from spring to summer and B. mikado from autumn to winter.  相似文献   

17.
万茜  张扬  张跃环  喻子牛 《海洋与湖沼》2015,46(5):1078-1087
水通道蛋白1(Aquaporin1,AQP1)是一类通过渗透梯度将水或一些小的中性分子快速穿过细胞膜的通道蛋白。通过RT-PCR和RACE技术克隆获得了香港牡蛎AQP1基因全长,并命名为Ch AQP1(Gen Bank登录号:KJ704847)。该基因全长1153bp,开放阅读框长度为888bp,编码295个氨基酸残基。Ch AQP1基因包括1个保守的MIP结构域、6个跨膜区、5个连接环、2个NPA(Asn-Pro-Ala)基序和选择性水孔构件ar/R(aromatic/arginine)。系统学分析表明Ch AQP1属于AQP1-like型水通道蛋白。m RNA组织分布结果显示,Ch AQP1在各个组织中均有表达,其中在闭壳肌和外套膜中表达量相对较高。利用实时定量PCR分析高、低盐胁迫下其在鳃中的表达模式,结果表明,Ch AQP1 m RNA表达量在低盐处理下基本没有太大变化;在高盐胁迫下,第1天(P0.01)、第3天和第5天(P0.05)显著下调;这说明Ch AQP1基因参与了香港牡蛎的渗透压平衡调节。  相似文献   

18.
Pseudocycnus appendiculatus Heller is described and recorded, for the first time from New Zealand, on Thunnus alalunga (Bonnaterre, 1788). Pseudocycnus spinosus Pearse, 1951 and P. thynnus Brandes, 1955 are thought to be synonyms of P. appendiculatus. Other species previously placed in the genus are discussed and the action of Yamaguti (1963) in removing them to other genera supported. It is suggested that the family Pseudocycnidae Yamaguti, 1963 cannot be differentiated from the family Dichelesthiidae Bassett‐Smith, 1898.  相似文献   

19.
Size-fractionated seawater samples were collected from the Gulf of Maine to determine the fraction (fc/d) of total dissolved (< 1 μm) Cd, Cu, Ni and 234Th in the colloidal size range (1,000 nominal molecular weight, NMW, to 1 μm) using cross-flow filtration. Colloidal Cd, Cu and Ni represents < 1–7% of the total dissolved concentration in these shelf waters and increases with an increase in particle concentration. By comparison, results obtained for particle-reactive 234Th indicate that < 1–47% of total dissolved is associated with the colloidal size fraction. A revised relationship between the concentration of colloids (Cc) and suspended particles (Cp) is reported (log Cc = 0.66 log Cp −2.01 kg L−1) and used to examine the dependence of fc/d for these metals on the concentration of suspended particles for Cp = 0.01–100 mg L−1. Results indicate that a significant fraction (˜ 10–30%) of Cd, Cu, Ni and 234Th in the traditionally defined ‘dissolved’ fraction may exist in the colloidal size range in regions characterized by high particle concentrations (Cp > 1–10 mg L−1), such as in near-shore and estuarine waters.  相似文献   

20.
A simple model of lower trophic level ecosystem has been created to analyze possible environmental control of primary production in eight sub-areas of the Seto Inland Sea. The primary production rates observed by Hashimotoet al. (1997a) in these sub-areas are well reproduced by the model, including horizontal processes such as horizontal transport of nutrients and vertical processes such as vertical mixing, light intensity and sinking of particulate matter. Without taking account of horizontal processes the model also successfully reproduces the observed primary production rates in some areas, but if fails to reproduce those in the others. This shows that the relative importance of the horizontal transport on the primary production differs are by area. Two time scales,T z andT H, are introduced to explain this difference.T z is a vertical cycling time of material, which is defined as the time during which the stock of the material in the water column is utilized for primary production;T H is the horizontal transit time of the material. The relative importance of the horizontal process is well explained by theT H/T z ratio; that is, the horizontal transport process is important in the areas where this ratio is small. Further the possible mechanisms of nutrient supply for the primary production in each sub-area are investigated using this model.  相似文献   

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