Host choice and fitness of anemonefish Amphiprion ocellaris (Perciformes: Pomacentridae) living with host anemones (Anthozoa: Actiniaria) in captive conditions

In this study, we investigated the host choice of naïve Amphiprion ocellaris, a specialist, at two different stages of development (newly settling juveniles and post-settlement juveniles). The fish were exposed to their natural and unnatural host species in the laboratory and their fitness was assessed in terms of activity and growth rate. Newly settling juveniles exhibited little host preference, while post-settlement juveniles immediately associated with their most common host in the wild. The analysis of fish activity confirmed that A. ocellaris is diurnal; they are most active in the morning, less at midday and barely move at night. The average travelling distance of juveniles was shorter in the groups living with their natural host, increasing in the groups living with an unnatural host and was highest in groups that did not become associated with any other unnatural host species. Post-settlement juveniles living with the natural host species grew better than those living with unnatural hosts or without anemone contact. These results suggest that the welfare of A. ocellaris in captivity will be optimized by keeping them with their natural anemone host species, although more generalist Amphiprion species may survive in association with other hosts.     

Arcyria monticola from Hokkaido, northern Japan: its habit, detailed morphology, and comparison with Arcyria imperialis

Arcyria monticola was found in Hokkaido, northern Japan. This is the first record of its locality, except for the type locality. The linearly expanding capillitium with many coils characterizing A. monticola consists of very elastic longitudinal tubes, short lateral tubes, and many small intricate nets. A longitudinal tube coils around a small intricate net, which forms a core. In contrast, A. imperialis, the other known Arcyria species with a linearly expanding capillitium, has neither short lateral tubes nor nets. The microscopic character of the A. imperialis capillitium is also totally different from that of A. monticola.     

Impact of micropredatory gnathiid isopods on young coral reef fishes

The ecological role of parasites in the early life-history stages of coral reef fish, and whether this varies between fish with and without a pelagic phase, was investigated. The susceptibility to, and effect of reef-based micropredatory gnathiid isopods on larval, recently settled, and juvenile fishes was tested using two damselfishes (Pomacentridae): Neopomacentrus azysron, which has pelagic larvae, and Acanthochromis polyacanthus, which does not. When larval and recently settled stages of N. azysron and very young A. polyacanthus juveniles (smaller than larval N. azysron) were exposed to one or three gnathiids, the proportion of infections did not vary significantly among the three host types or between the number of gnathiids to which the fish were exposed. The overall infection was 35%. Mortality, however, differed among the three gnathiid-exposed host types with most deaths occurring in larval N. azysron; no mortalities occurred for recently settled N. azysron exposed to one or three gnathiids, and A. polyacanthus exposed to one gnathiid. Mortality did not differ significantly between larval N. azysron and A. polyacanthus juveniles, failing to provide support for the hypothesis that reef-based A. polyacanthus juveniles are better adapted to gnathiid attack than fish with a pelagic phase. The study suggests that settling on the reef exposes young fish to potentially deadly micropredators. This supports the idea that the pelagic phase may allow young fish to avoid reef-based parasites.     

Larval morphology and occurrence of the louvar,Luvarus imperialis (Luvaridae)

A total of nineteenLuvarus imperialis larvae, 3.5 to 10.7 mm in standard length were collected during the cruises of R/V Shoyo Maru in the northwestern Pacific and eastern Indian Ocean. This paper describes meristic and morphological features of these specimens throughout development. The features particularly noted in postlarvae and early juveniles ofL. imperialis are: 1) large head with a wide snout, 2) oval and well-compressed body, 3) large pectoral fins, 4) developed and finely serrated dorsal and pelvic spines, 5) well-developed head spination, 6) minute spines on the soft rays of all fins in larvae larger than about 5.6 mm SL, and 7) very rough body surface associated with the development of spiny-edged scales. Larvae ofL. imperialis occur mostly in the coastal waters between lat. 40°N and 40°S of the world oceans, suggested the spawning in temperate waters.     

长江口水域夏季鱼卵和仔稚鱼年间变化

基于2005年、2008年、2009年和2011年8月(夏季)在长江口水域(30°30'—31°45'N,121°15'—123°10'E)4个航次的浮游生物拖网资料,分析了长江口水域鱼卵和仔稚鱼的种类组成、数量分布特征及其年间变化。结果表明:4个航次采集的鱼卵和仔稚鱼鉴定到种的种类有17种,隶属于8目13科,以鲈形目种类最多,11种,其次是鲱形目,5种,其他各目种类均小于5种;种类数存在明显年间差异,2005年种类数最多(鱼卵3种,仔稚鱼8种),其次是2009年和2011年,2008年种类数最少(鱼卵1种,仔稚鱼5种)。优势种年间更替明显,长蛇鲻(Saurida elongata)、虾虎鱼(Gobiidae spp.)和中华小公鱼(Stolephorus chinensis)在2005年是优势种,2008年优势种为鳀鱼(Engraulis japonicus),2009年优势种为鳀鱼、寡鳞飘鱼(Pseudolaubuca engraulis)、虾虎鱼等,2011年虾虎鱼和小公鱼(包括小公鱼属未定种Stolephorus spp.和中华小公鱼Stolephorus chinensis)成为优势种。2005年鱼卵和仔稚鱼数量分布的密集区在嵊泗列岛附近水域,2008年鱼卵和仔稚鱼出现较少,未出现明显的数量密集区;2009年鱼卵数量较少,仔稚鱼数量较多,密集区主要分布在在长江口以外123°E附近水域;2011年鱼卵主要分布在在长江北支口门外附近水域,仔稚鱼在调查区内分布相对均匀。     

Physical changes in specimens of five species of Cyprinidae preserved in ethanol and frozen

Preservation in 30% ethanol and freezing to a temperature of ?20 ± 2° C is an appropriate method for measurement of fish eggs, larvae and juveniles. Egg diameter of the common carp Cyprinus carpio increased insignificantly by 1·32% after preservation compared with live size. The total length (L_T) of 1 day post‐hatching (dph) larvae as well as the standard length (LS) of 16 dph larvae of C. carpio increased significantly (2·95 and 1·50%, respectively) after preservation. Egg diameter as well as the L_T of 1 dph larvae of barbel Barbus barbus increased significantly after preservation, by 1·74 and 1·96%, respectively over their original size. The standard length (L_S) of 14 dph larvae of B. barbus as well as juveniles of B. barbus, crucian carp Carassius carassius, common nase Chondrostoma nasus and tench Tinca tinca decreased significantly after preservation (?0·56 to ?5·54%), whereas their body mass increased significantly (11·46–18·57%). Preserved eggs of C. carpio and B. barbus were hard, round and transparent. The larvae and juveniles of examined fishes, preserved in frozen ethanol, were straight, flexible and easily measurable after 60 days. Integrity of body surface and fins, as well as preservation of colours were much better in larvae or juveniles frozen and thawed only once than in specimens frozen and thawed thrice. Cooling in 30% ethanol to a temperature of 6 ± 2° C and freezing in water to a temperature of ?20 ± 2° C are not appropriate preservation methods for eggs and larvae of C. carpio (1 and 16 dph).     

Loss of genetic diversity in farmed populations of Colossoma macropomum estimated by microsatellites

The genetic variability of four Colossoma macropomum broodstocks, three from fish farms in different regions and one from the natural environment in Brazil, was analyzed using microsatellite markers. The wild progeny (n = 30) were caught in the Solimões–Amazonas River, at the varzea lakes; this location is used to mature the fish from larvae to juveniles. The three fish farms were selected according to the age of their lineages and broodstock availability: DNOCS (n = 21) is located in the Ceará State, representing the oldest lineage of cultivated tambaqui in Brazil; Balbina (n = 30) is located in the Amazonas State, representing the youngest stocks of tambaqui farmed in Brazil (approximately 15 years); and UFRPE (n = 30) is located in the Pernambuco State and is considered to be a mixed stock formed from the DNOCS and Balbina lineages. The analysis of 13 microsatellite loci indicated the occurrence of a variability reduction in the farmed populations; the UFRPE stock was the population with the highest diversity level. Low values of molecular coancestry were found in these populations. Additionally, significant differences in the R_ST values among the populations were detected, as was the occurrence of genetic structure. The genetic loss found in these populations may have been influenced by the founder effect. Because no breeding programs were during the entire production period and no pedigree records were kept for these broodstocks, we suggest that a wild population might be used as an important genetic resource to increase the genetic diversity of renewal stock lineages.     

Density and size distribution of Daphnia populations at different fish predation levels

Density and size structure changes of natural daphniids populations were studied in enclosures with a different level of fish predation. Daphnia pulicaria was totaly removed in high predation variants, and the differences of the mean body length both in adults and juveniles are apparent between low predation enclosure and enclosure without fish. Daphnia galeata was replaced by D. magna and D. pulicaria in the enclosure without fish. The decline of densities and the substantial (30–50%) and fast (during 12 days) shift of mean body length both in adults and juveniles of D. galeata was induced by the fish (carp fry) introduction to the high predation enclosures.     

Effects of low temperature on growth and non-structural carbohydrates of the imperial bromeliad <Emphasis Type="Italic">Alcantarea imperialis</Emphasis> cultured in vitro

The imperial bromeliad Alcantarea imperialis grows naturally on rocky outcrops (‘inselbergs’) in regions where daily temperatures vary from 5 to 40°C. As carbohydrate metabolism is altered in response to cold, it could lead to reprogramming of the metabolic machinery including the increase in levels of metabolites that function as osmolytes, compatible solutes, or energy sources in order to maintain plant homeostasis. The aim of this study was to evaluate the effects of different temperatures on plant growth and non-structural carbohydrates in plants of A. imperialis adapted to low temperature. Seedlings of A. imperialis were grown in vitro under a 12-h photoperiod with four different day/night temperature cycles: 5/5°C, 15/15°C, 15/30°C (dark/light) and 30/30°C. Plants were also cultivated at 26°C in ex vitro conditions for comparison. The results showed an inverse relationship between temperature and germination time and no differences in the percentage of germination. Plants maintained for 9 months at 15°C presented a reduced number of leaves and roots, and a dry mass four times lower than plants grown at 30°C. Sugar content was higher in plants grown at 15°C than at 30°C. However, the highest amount of total sugar was found in plants growing under warm day/cold night conditions. Myo-inositol, glucose, fructose and sucrose were found predominantly under high temperatures, while under low temperatures, sucrose was apparently replaced by trehalose, raffinose and stachyose. Starch content was highest in plants grown under high temperatures. The lowest starch content was detected under low temperatures, suggesting its conversion into soluble carbohydrates to protect the plants against cold. These results indicated that low temperature retarded growth of A. imperialis and increased sugar levels, mainly trehalose, thus suggesting that these sugar compounds could be involved in cold tolerance.     

Ontogenetic Shifts in Patterns of Microhabitat Utilization in the Small-headed Clingfish, Apletodon Dentatus (Gobiesocidae)

The patterns of microhabitat utilization by the clingfish Apletodon dentatus were investigated, based on SCUBA diving surveys at the Arrábida Marine Park (Portugal). In all inspected microhabitats, this species was only found in algal turfs, sea urchins and boulders. The association of A. dentatus with sea urchins is here analysed for the first time. There was a differential utilization of the microhabitats, with small juveniles recruiting to algal turfs, intermediate individuals found in association with the sea urchins Paracentrotus lividus and Sphaerechinus granularis and larger fish occurring mainly in boulders. The depth distribution patterns are also analysed.     

Effect of vertebrate predation on the spatio-temporal distribution of cladocerans in a temperature eutrophic lake

We analysed the spatio-temporal distribution of zooplankton along a profile of 10 stations from the shore to the pelagic zone from April to September 1988, the period when the larvae and juveniles Rutilus rutilus, the most abundant species in the Lake, are in the littoral zone. The digestive tracts of the young roach were analysed. They fed essentially on rotifers and on cladocerans. For comparison, zooplankton was also analysed at one littoral area without fish fry. There was an increase of cladoceran density from the vegetated nearshore zone to the offshore zone. Considering the density of Bosmina longirostris, Daphnia longispina, Chydorus sphaericus and Ceriodaphnia quadrangula, we observed a different distribution pattern in the course of the year. In the nearshore zone, the relative abundance of small species, Bosmina and Chydorus, was much higher than that of the larger Daphnia. From April to September, predation pressure mainly affected the smallest species: in contrast to the inshore station without fish fry, the density of Bosmina decreased in May in the littoral with fish. Chydorus was concentrated in the littoral between February and April, then grew into the pelagic zone, where predation pressure obviously was low during the warm season. The number of Daphnia, which was eaten by the fish fry at any time, remained low in the nearshore zone, which suggests that the presence of fish may cause Daphnia to avoid this zone. Ceriodaphnia which was not affected by this predation, was scarce in the nearshore zone during mid-summer. The low density of the cladocerans in the nearshore zone is likely associated with vertebrate predation by roach fry and juveniles, the result of such a process being either a depletion in density of the prey, or an avoidance behaviour.     

Environmental requirements of common riverine European salmonid fish species in fresh water with particular reference to physical and chemical aspects

This review attempts to assess, as quantitatively as possible, the habitat requirements in fresh water of three common and widespread European salmonid species. Namely: the trout (Salmo trutta L.), the salmon (S. salar L.) and the grayling (Thymallus thymallus L.). Requirements are considered for spawning, incubation and emergence, juveniles and smolts and for adults and spawning movements.     

The importance of juveniles in modelling growth: butterflyfish at Lizard Island

Synopsis I established and fitted von Bertalanffy growth functions to size-at-age data for four species of chaetodontids at Lizard Island. Special emphasis on juveniles provided detailed information of the early growth period. All four species demonstrated rapid initial growth achieving an average of 92% of maximum theoretical size in the first 2years. I used various constraints of the theoretical age at length zero (t₀) in an analysis of both complete data sets and data sets using only adult fish. An unconstrained value of t₀ resulted in the best-fit (maximum r²) curve when juveniles were included. When excluding juveniles, it was necessary to constrain t₀ to an approximate settling size to most closely represent the growth of the species.     

Composition and length‐weight relationships of fish species in Lake Erhai,southwestern China

Length–weight relationships (LWRs) are described for 23 fish species (five indigenous species and 18 exotic species) in Lake Erhai, a plateau deep lake located in southwestern China. Four different types of fishing gear were used in order to include all possible length ranges from 2009 to 2012. Results show that the exponent b ranged from 2.72 to 3.79. The length of the growth inflection point between juveniles and females of Pseudorasbora parva and Micropercops swinhonis coincides with the length at which 50% of the females are sexually mature, respectively. The LWRs of P. parva and M. swinhonis are affected by sexual dimorphism, and Hemiculter leucisculus shows significant differences between juveniles and females. In addition, the first LWR records for nine species are provided in this study.     

Taxonomic study of the genus Dichrogaster Doumerc (Hymenoptera: Ichneumonidae: Cryptinae) in Japan

Japanese species of the genus Dichrogaster are revised. Four species are recognized. Two species, D. imperialis n. sp. and D. parva n. sp., are described. Dichrogaster liostylus (Thomson) and D. kichijoi (Uchida) are redescribed. A key to the Japanese species is provided.     

Extent and role for fish populations of riverine ecotones along the Sinnamary river (French Guiana)

The Sinnamary is a small tropical river (250 km long, watershed of 6500 km²) where a dam is to be impounded in 1994.The extent of naturally periodically flooded areas along the Sinnamary river is estimated by using remote sensing (Landsat TM satellite data) and botanical groupings are described on in situ observations, ground truth and collections. The fish assemblages of these areas are described and their density estimated by rotenone sampling. The role of this ecotone to fish populations is discussed.The extent of the inundated areas appears to be greater than previously estimated by classical mapping.As expected, the fish fauna is mostly composed of fish juveniles and adults of dwarf (< 3 cm) and small (< 15 cm) species. Large predators where not found. Due to these characteristics, fish are abundant but their biomass is low in naturally inundated areas. However, juveniles of some species found only in these zones. Therefore their adult populations will probably be very sensitive to any modification of these land/water ecotones.     

Timing and size of blooms of the ctenophore Mnemiopsis leidyi in relation to temperature in Narragansett Bay, RI

The ctenophore Mnemiopsis leidyi is at the northern extreme of its geographic range in Narragansett Bay, an estuary on the northeast coast of the United States. Blooms have typically been observed in late summer and fall according to records from 1950 to 1979. We document an expansion of the seasonal range of this important planktonic predator to include springtime blooms during the 1980s and 1990s. This shift to an earlier seasonal maximum is associated with increasing water temperature in Narragansett Bay. Temperatures in spring have risen, on average, 2 °C from 1950 to 1999 with warm years being associated with the positive phase of the North Atlantic Oscillation. During 1999, M. leidyi appeared earlier in spring and was more abundant than during any previous year for which records are available. Changes in the seasonal pattern and abundance of this predator are likely to have important effects on planktonic ecosystem dynamics of Narragansett Bay. These include reduction of zooplankton abundance in spring followed by increases in size and frequency of summer phytoplankton blooms. Earlier blooms of M. leidyi may also reduce survival of eggs and larvae of fish because, as in 1999, they coincide with the period of peak spawning.     

Genetic structure analysis of Girella laevifrons populations in central Chile

Connectivity among most marine species depends of their life cycles, and the main phase that can regulate dispersal is the larval stage of an organism. Girella laevifrons (Girellidae) is an omnivore fish inhabiting in intertidal pools as juveniles and subtidal reefs as adults from northern to central Chile. It has a pelagic larval duration for approximately 69 days. In this study, we used eight molecular markers (microsatellites) to explore the genetic structure of their populations along 400 km of the central Chilean coast.20 juveniles were sampled from four different populations. Microsatellite loci did not detect a genetic structure within a 400 km scale along the coast of Central Chile. There is evidence (F_st = ?0.0038, p = 0.8954) suggesting that populations between Coquimbo and Littoral Central behave as a single whole population. This could be an estimate that may define future management units for the species.     

Fossil juvenile coelacanths from the Devonian of South Africa shed light on the order of character acquisition in actinistians

A new coelacanth genus from the Famennian (Upper Devonian) of South Africa is described, principally from presumed juveniles. S erenichthys kowiensis gen. et sp. nov. uniquely shares with Diplocercides a ventral expansion of the elbow‐like lachrymojugal, as well as a symmetrical diphycercal tail supported by expanded neural and haemal spines and radials. Serenichthys is distinguished from Diplocercides by a number of derived characters, including possession of longer anterior parietals, a more crescent‐shaped postorbital with a more anteriorly positioned infraorbital canal, and a far smaller squamosal, which is well separated from the skull roof. By contrast, Serenichthys appears to lacks a second dorsal fin lobe, a derived feature present in Diplocercides. Most specimens of Serenichthys are between 3 and 6 cm in length. They have large eyes, and dermal bones of the skull ornamented with long wavy ridges, similar to the dermal ornament of other Devonian coelacanths such as Gavinia. Larger isolated operculae also collected from the Waterloo Farm locality and attributed to Serenichthys indicate that with growth the ridges on the dermal bones transformed into elongate tubercles, reminiscent of those of Diplocercides and Carboniferous taxa. Phylogenetic analysis resolves Serenichthys as the sister group of Holopterygius and all known post‐Devonian coelacanths. The clade including the unusual leaf‐shaped coelacanths, the Devonian Holopterygius and Carboniferous Allenypterus, branches from the coelacanth lineage immediately crownward of Serenichthys. The presence of abundant juveniles within an estuarine setting strongly parallels the discovery of similarly sized juveniles of Rhabdoderma exiguus together with eggs and yolk‐sack larvae in the Upper Carboniferous Mazon Creek biota. It is therefore argued that Serenichthys, like Rhabdoderma, was using the sheltered estuarine environment as a nursery. © 2015 The Linnean Society of London     

Demonstration of migration of juvenile cyprinid fish using parasite biomarkers

Migration of juvenile (0+) cyprinid fish from the Kiso River to experimental streams in the Aqua Restoration Research Center was demonstrated by the presence of parasites on fish. The experimental streams were located a minimum of 0.7 km from the main reach of the Kiso River, and they were connected via a tributary (Shinsakai River). The experimental streams were used as a spawning site and a nursery for juveniles, similar to the use of a temporary water body such as a paddy field. A digenean trematode (Centrocestus spp.) and the glochidia of unionid bivalves, both of which did not infect fish in the experimental streams or in the Shinsakai River, were used as marker parasites. Their presence indicated that the fish moved in the experimental streams from the Kiso River. For both fish species (Gnathopogon elongatus and Zacco platypus) assessed in this study, juveniles greater than 20–30 mm standard length could migrate from the Kiso River. This study showed that temporary waters are important as a nursery for juvenile fish, for whether or not a species spawns there. For the conservation of fish populations, it is important that temporary waters that are used as a nursery are connected with a permanent water area by a channel, through which not only adults, but also juvenile fish can migrate.