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261.
The effects of blooms of the cyanobacterium Trichodesmium spp. on penaeid prawn larvae were examined using in situ and laboratory rearing experiments and plankton surveys in Albatross
Bay, Gulf of Carpentaria, Australia. The in situ experiments demonstrated that, during a bloom of Trichodesmium spp., larvae of the prawn Penaeus merguiensis did not develop beyond the first protozoea stage, and survival was low compared with times when diatoms were dominant in
the same study area. Laboratory experiments confirmed the in situ results. None of the prawn larvae fed Trichodesmium sp. in laboratory experiments developed beyond the first protozoeal stage. In contrast, 94% of prawn larvae fed the green
flagellate Tetraselmis suecica successfully developed to the second protozoea stage. Electron microscopy of larvae gut-contents revealed that Trichodesmium spp. were ingested by larvae but were of no nutritional value, resulting in starvation. A 7 yr plankton survey, from 1985
to 1992, showed that minimum abundance of prawn larvae occurs during the annual summer blooms of Trichodesmium spp. and that maximum abundance of prawn larvae generally occurs just after the bloom. There was a negative correlation between
the abundance of larvae and the abundance of Trichodesmium at individual sites, one offshore and one inshore, indicating that the blooms affect the survival of larvae. We conclude that
variations in both timing and magnitude of Trichodesmium blooms are important determinants of prawn larvae abundance in Albatross Bay.
Received: 28 April 1997 / Accepted: 2 April 1998 相似文献
262.
High-resolution videos, scanning electron microscopy and histology were used to study the feeding mechanism of myodocopid
ostracods from the Pacific Coast of Japan, as exemplified by Vargula hilgendorfii (Müller, 1890) and a few other cypridinid species. Ostracods observed in the laboratory were attracted to a wide spectrum
of natural food sources, behaving as predators of living prey (e.g. polychaete annelids), as opportunistic scavengers on dead
animals (e.g. annelids, fishes, squid), and also consuming artificial food. Food sources may be detected by chemoreception.
The fourth limb (endopodites with strong sclerotized setae) and the furcal lamellae (claws with teeth) act in coordination
to abrade and eventually tear open the protective integument of living/dead prey such as annelids. The mandibular palps are
used mainly to hold the food. Food sections and soft-body contents are transferred to the mouth by the fourth limb (endopodial
“rake”) and fifth limb (exopodite with pectinate setae) and are passed to the oesophagus by the endites (mandibles, fourth
and fifth limbs). Food is subsequently pumped up to the stomach by peristaltic contractions of the oesophagus (ring muscles)
and stored in the stomach pouch. The upper lip of bioluminescent (V. hilgendorfii) and non-bioluminescent species of Cypridinidae often contact food, suggesting that some of the glands housed in this organ
may emit digestive enzymes prior to ingestion. Ostracods are able to ingest massive quantities of food within a few minutes
and to survive starvation for several weeks. In V. hilgendorfii, the midgut is a huge sac-like organ with no partition and is lined with a single layer of columnar epithelial cells. No
differentiated hepatopancreas is present. The cypridinid produces a single faecal pellet wrapped in a thin reticulated, peritrophic
membrane. Myodocopid ostracods exhibit a wide range of feeding strategies (detritus-feeding, comb-feeding, scavenging, predation,
ectoparasitism) in both benthic and pelagic niches, and constitute a substantial source of food for many zooplankters. Adaptation
of cypridinids to scavenging/predation is reflected in the morphology of their furcae, mandibles, fourth and fifth limbs,
and their digestive system. Palaeontological data suggest that early Triassic cypridinids and possible late Ordovician myodocopids
may have been carnivorous scavengers feeding on carcasses of cephalopods (ammonoids or orthoconic nautiloids), thus playing
the same role of “recyclers” as modern representatives of the group.
Received: 2 January 1998 / Accepted: 23 July 1998 相似文献
263.
J. B. Lewis 《Marine Biology》1998,130(4):651-662
Dipolydora armata (Langerhans, 1880) is a small (4 to 5 mm) spionid polychaete found burrowing in the calcareous hydrozoan Millepora complanata Lamarck, 1816, on coral reefs at Barbados, West Indies. It excavates complex networks of interconnecting burrows and forms
aggregations of worms in cavities within branches of the coral. Adult worms have a mixed feeding mode (suspension feeding
and deposit feeding). Size–frequency distributions of worms in branch samples suggest that they mature in a single year and
that reproduction occurs throughout the year. Burrow openings on the surface of the coral develop distinctive, erect spines
caused by combined growth of worm tubes and host tissue. Millepore zooids were absent in the vicinity of tube openings and
on spines, and thus the potential feeding surface of the coral will be reduced in heavily colonized branches. Burrows and
openings were densest at the bases of millepore branches where weakening of the skeleton would be expected to occur. The absence
of openings near the branch tips suggests difficulty in larval settlement there, amongst stinging zooids. Reproduction␣and
larval development of the worms were examined, and a sequence of larval stages from one to 20 segments and a juvenile stage
of 22 segments are described. Eggs are deposited in brood sacs attached to the burrow wall, and the larvae feed upon nurse
eggs (adelphophagy). The presence of larvae and juveniles occurring free in the burrows suggests that larval development may
be completed within the host coral as an alternative or in addition to a planktonic larval phase. Lack of provisional larval
setae, early development of adult capillary setae, production of special spermatophores and a protracted breeding cycle in
D. armata are all traits which would favour complete development within the host skeleton.
Received: 6 March 1997 / Accepted: 25 October 1997 相似文献
264.
Previously published mtDNA cytochrome b sequences for Xyrichtys novacula (Linnaeus) and two morphologically distinct types of Xyrichtys larvae (Pisces: Labridae) included human cytochrome b sequence, presumably due to sample contamination and/or poor preservation of sample DNA. Those sequences had been used to
identify the two types of Xyrichtys larvae as X. novacula, but owing to the contamination, the identifications are invalid. Fresh specimens were collected: X.␣martinicensis (Cuvier and Valenciennes), X. novacula, X. splendens (Castelnau), and Xyrichtys sp. larvae of each of the two morphotypes (dorsal-forward eye and ventral-forward eye). The cytochrome b fragment was amplified from each specimen using the polymerase chain reaction. Comparison of the sequences with human cytochrome b sequence confirmed that the new sequences were not contaminated. The interspecific differences in Xyrichtys sequences were less than previously reported, but still greater than observed in many fish genera. Distance and parsimony
analyses indicated that X. novacula and X. martinicensis were more closely related to each other than to X. splendens. This conclusion differs from our previous conclusion that X. martinicensis and X. splendens were more closely related to each other than to X. novacula. Distance and parsimony analyses also demonstrated that both larval morphotypes were X. novacula and, thus, our previous conclusions regarding larval ecology and oceanographic transport remain unchanged.
Received: 12 March 1997 / Accepted: 24 October 1997 相似文献
265.
M. Thiel 《Marine Biology》1998,132(2):209-221
The suspension-feeding amphipod Dyopedos monacanthus (Metzger, 1875) is a common epibenthic amphipod that lives on self-constructed “mud whips” (built from filamentous algae,
detritus and sediment particles) in estuaries of the northern North Atlantic Ocean. The population biology of D. monacanthus at a shallow subtidal site in the Damariscotta River Estuary (Maine, USA) was examined between July 1995 and July 1997. The
resident population at the study site was dominated by adult females during most months of the year. High percentages of subadults
were found in late summer/early fall. Often, between 10 and 20% of the adult females were paired with males, and the percentage
of ovigerous females varied between 40 and 100%, indicating continuous reproduction. The percentage of parental females varied
between 40 and 80% during most months, but dropped to levels below 20% during summer/early fall. The average size of amphipods
on their own mud whips was ∼4 mm during the summer/early fall, after which it increased continuously to >7.0 mm in March or
April, and then dropped again. In March and April, the average number of eggs and juveniles female−1 was ∼100 eggs and 55 juveniles, while during the summer/early fall the average number of eggs female−1 was <20 and that of juveniles female−1 was <10. Many juveniles grew to large sizes (>1.4 mm) on their mothers' whips in winter/early spring but not in the summer/fall.
The average number of amphipods at the study site was low in late summer/early fall (<50 individuals m−2), increased steadily during the winter, and reached peak densities of >3000 individuals m−2 in April 1996 (>1600 individuals m−2 in May 1997), after which densities decreased again. The decrease of the D.␣monacanthus population at the study site coincided with a strong increase of amphipods found pelagic in the water column. This behavioural
shift occurred when temperatures increased and benthic predators became more abundant and active on shallow soft-bottoms,
suggesting that D. monacanthus at the study site is strongly affected by predation. The effects are direct (by predation on amphipods) and indirect (by
reducing duration of extended parental care and enhancing pelagic movements). Both extended parental care and pelagic movements
are important behavioural traits of D.␣monacanthus (and other marine amphipods), and significantly affect its population dynamics.
Received: 18 January 1998 / Accepted: 27 May 1998 相似文献
266.
Whole-body carbon (C), nitrogen (N) and phosphorus (P) content, and stable-isotope composition (13C:12C and 15N:14N), were followed during metamorphosis of bonefish (Albula sp.) larvae (leptocephali). Metamorphosing larvae depend entirely on endogenous carbon compounds (some of which contain N and P) as an energy source. Two fundamental questions are (1) Do the demands of extensive tissue remodeling during metamorphosis require the efficient retention of N and P during the catabolism of carbon compounds? (2) What effect does the lack of feeding have on stable-isotope composition? Our results showed that both C and N decreased by ~35 to 40%, reflecting the utilization of neutral lipid (triacylglycerols) and N-containing compounds (phosphatidylethanolamine and keratan sulfate glycosaminoglycan) as energy sources, and indicating that larvae have little or no capacity to retain N. Evidence suggested that collagen breakdown, measured as a loss of hydroxyproline content, also contributed to N loss. Stable-isotope ratios, expressed as 13C and 15N, showed no statistically significant differences in early and advanced metamorphosing larvae. In contrast to C and N, phosphorus was conserved during metamorphosis and most probably is utilized in the increased bone mineralization occurring in advanced larvae. We show, however, that advanced larvae are P-limited and that normal ossification is dependent upon a supply of exogenous P obtained after the resumption of feeding. The N:P ratio of 12.3 in early larvae decreased to 8.1 in advanced larvae owing to the conservation of P as N was lost. The mean 15N value in early metamorphic larvae (11.6‰) is consistent with results from other studies, and provides further support for the view that premetamorphic leptocephali feed at a very low trophic level. 相似文献
267.
The pattern of settlement over time of three broadcast spawning coral species (Cyphastrea serailia, Acanthastrea lordhowensis, and Goniastrea australensis) from the Solitary Islands (30°00′S; 153°20′E) was studied in 1995 and 1996 in order to determine the maximum length of time
these larvae could remain in the water column and still retain the ability to settle and metamorphose. Larvae were maintained
in aquaria and the number which had settled on biologically-conditioned tile pairs was monitored every 5 to 10 d. While the
majority of larvae settled quickly after becoming competent, some larvae survived and settled for extended periods after spawning.
Competency periods ranged from 26 d for C. serailia to 56 d for G. australensis and 78 d for A. lordhowensis. These data greatly extend the known competency periods for larvae of broadcast-spawning corals and indicate the potential
for transport of broadcast-spawned coral larvae over large distances. Medium to long-distance larval dispersal of the species
studied provides a mechanism for their widespread distribution in subtropical regions, on reefs which are often widely spaced
and relatively isolated.
Received: 27 May 1997 / Accepted: 27 November 1997 相似文献
268.
Karyotypic characterization of the great sturgeon, Huso huso, by multiple staining techniques and fluorescent in situ hybridization 总被引:1,自引:0,他引:1
F. Fontana J. Tagliavini L. Congiu M. Lanfredi M. Chicca C. Laurente R. Rossi 《Marine Biology》1998,132(3):495-501
A karyotype analysis by several staining techniques was carried out on the great sturgeon, Huso huso (Linnaeus, 1758). The karyotype (2n = 118 ± 2) was composed of 42 pairs of meta-/submetacentric chromosomes and 17 pairs of acrocentrics/microchromosomes. Constitutive
heterochromatin was mainly located at the centromeric regions of the acrocentric chromosomes. The biarmed chromosomes showed
weak C-bands. Fluorescent staining with GC-specific chromomycin A3 showed clearly recognizable fluorescent regions, whereas a more uniform base composition was revealed by the AT-specific
4,6-diamidino-2 phenylindole. After Ag-staining, nucleolar organizer regions could be observed on the short arms of two medium-sized
submetacentrics and on two acrocentrics. Digoxigenated 28S and 5S rDNA probes, prepared from Acipenser naccarii DNA and hybridized to metaphase chromosomes, showed signals on six and two chromosomes, respectively. The telomeric sequence
(TTAGGG)
n
detected by FISH was located at both ends of each chromosome. Results are discussed in relation to karyotype organization
and evolution in sturgeons.
Received: 1 April 1998 / Accepted: 21 July 1998 相似文献
269.
Three marine diatoms Lauderia annulata Cleve, Odontella sinensis (Greville) Grunow and Thalassiosira rotula Meunier were exposed to ultraviolet (UV) radiation of different wavebands under controlled laboratory conditions (0.035 vol%
CO2, 18 °C). Several changes in the patterns of pigments in these organisms were seen depending on the waveband of UV radiation
and species examined. UV-B and UV-B plus UV-A radiation led to a reduction in the overall pigment content of all three diatoms.
The uptake of 15N-ammonium was less affected by 5-h UV-A (WG 320) but significantly reduced after UV-B and UV-B plus UV-A exposure. The pattern
of free amino acid pools varied depending on the applied UV wavebands and the tested diatom. The main protein-bound amino
acids of T. rotula decreased after 5-h UV irradiance except leucine. Contents of adenosine 5′-mono-, di-, and triphosphate (AMP, ADP and ATP)
were affected differently by UV radiation; ATP values increased at the end of UV-B and UV-B plus UV-A exposure. These results
have been discussed with reference to the impact of the different UV sources and the influence on the nitrogen metabolism
in connection to pigments and supply with energy.
Received: 13 May 1997 / Accepted: 11 October 1997 相似文献
270.