Effects of summer drawdown on cyprinid fish larvae in Lake Biwa, Japan

The effects of artificial water-level manipulations in Lake Biwa, initiated in 1992 to prevent flooding, on cyprinid fish larvae were assessed by measuring and estimating the topographic change in the reed zones. The shallow, litter-accumulated water in those zones was inhabited by larvae of two species, Carassius spp. and Cyprinus carpio. More than 70% (by volume) of these shallow areas in Lake Biwa was estimated to be lost when the water level was artificially lowered by 30cm from June to October 1997. During the low water level period, significantly fewer eggs of these cyprinid fishes were collected in a reed zone than in April and May of the same year, a comparison with a previous study suggesting that spawning of the fishes was inhibited during the period of low water level. The artificial reductions in water level probably resulted in a significant decrease in the volume of shallow water in the lake and may be linked to the drastic decline in these cyprinid fishes.     

Developmental interactions between the army wormLeucania separata [Lep.: Noctuidae] and its parasiteApanteles ruficrus [Hym.: Braconidae]

The developmental interactions between the gregarious endoparasitoidApanteles ruficrus Hal. and the army worm,Leucania separata Walker were investigated. The parasitoid preferred young host larvae and developed in 9.5 days irrespective of host age at the time of parasitization. The growth of parasitized host larvae were depressed. The net maximum weight of the host larva was positively correlated with the number of parasitoid eggs laid when the 2nd instar was parasitized. And when parasitizing in 2nd instar, the weight of parasitoid was negatively correlated with the number of eggs laid. The parasitoid has an ability to regulate the size of the host and the parasitoid itself according to the number of eggs laid when the host larva is very small.     

Experimental studies on parasitization byApanteles Glomeratus V. Relationships between growth rate of parasitoid and host age at the time of oviposition

The growth and development ofApanteles glomeratus L. eggs and larvae in the host larva (Pieris rapae crucivora Boisduval) was investigated by calculating their volume. WhenA. glomeratus eggs increase 90 fold in volume after being laid, larvae hatch from them. The larvae grow exponentially and the growth rate of the parasitoid is dependent on the host stage. Being laid in the 1st instar host, the parasitoids grow more slowly than those laid in 2nd–4th instar host. A pupal host stage prevents the parasitoids’ development. When larvae exceed the threshold size of 5.0×10⁸ μ³, they enter the 2nd instar. A few days after they attain the maximum size of 3.3×10⁹ μ³, they moult and egress from the host body.     

Biology of the small pelagic fishes in the New Volta Lake in Ghana. Part III: Sex and reproduction

Reproductive patterns of five species, from three families, of small pelagic fishes in the new Volta Lake in Ghana showed several similar features. These included sex size defferences, males maturing and reaching final sizes smaller than females; heterogenous sex ratios in four species, being most markedly unequal usually at peak breeding times; demersal eggs; and extended fractional spawning patterns. The clupeids Pellonula and Cynothrissa and the cyprinid Barilius all breed in the dry season, whereas the schilbeids Physailia and Siluranodon are wet-season spawners. Only Pellonula and Physailia have extended their breeding season in the new lake to cover most of the year; the other species have not, although Siluranodon spawns into the early dry season. In the lake environment Pellonula's pelagic larva is no longer endangered by seasonal floods, whereas Physailia can use the lake's continuous “high waters” for extended breeding. Relaxation of breeding patterns and protracted fractional spawning has allowed best exploitation of the new regime.     

Induction of ovarian maturation and development of eggs,larvae and juveniles of the tonguefish,Cynoglossus abbreviates,reared in the laboratory

Cynoglossus abbreviatus spawns from mid-March to mid-April in the Sea of Shimabara in Kyushu. During the spawning season ovarian maturation was successfully induced by injection of the pituitary homogenate ofHypophthalmichthys molitrix. The dose of the aceton-dried pituitary homogenate was 6.5 mg/kg body weight ofC. abbreviatus. It took about 2 days for ovulation after injection at a water temperature of 14 to 16°C. Artificial fertilizations were accomplished on March 29, 1974 and again on April 7, 1984, using the females matured by hormone injection in the latter case only. The larvae were reared on the rotifers,Artemia nauplii,Tigriopus japonicus and copepods collected from the sea over a period of 113 days in 1974 and 58 days in 1984. The eggs were pelagic, spherical, 1.19–1.23 mm in diameter and had 30–50 oilglobules of 0.068–0.095 mm in diameter, and the perivitelline space was narrow. The incubation period was 90–98 hours at a water temperature of 14 to 16°C. The newly hatched larvae were 3.18–3.45 mm TL and had 61–64 myomeres. The larvae had many melanophores and xanthophores on the body, forming three bands on the caudal region, but were lacking chromatophores on the finfolds. The yolk was completely absorbed when the larvae attained a size of 4.7–5.6 mm TL 8 days after hatching. A single elongated dosai fin ray developed on the head in the 8-day old larvae. The ray was reduced in size as long as the other rays 1 or 2 days after metamorphosis. The rudiment of pectoral fins were found on the both sides of the body in the 2-day old larvae, but two of them disappeared after metamorphosis. A pelvic fin first appeared as a ventral bud just anterior to the gut in the larva of 8.39 mm TL. The full count of 4 rays was observed on the larva of 10.83 mm TL. Metamorphosis began 22 days after hatching when the larvae were 11.20 mm TL. The right eye began to shift the left side of the head at night and reached to the final place after 8.5 hours. It took about 36 hours to complete the metamorphosis, including the eye movement and fusion of the hole in the rostral beak. At the last stage of metamorphosis, the dosal, caudal, anal and ventral fins became confluent. The larvae reached the juvenile stage at a size of 13.5–14.0 mm TL, approximately 28 days after hatchling. The growth of larvae reared in 1974 is expressed by the following equations: Y₁ = 3.448 · 1.0507^x (8≦X≦28) Y₂ = 6.3322 · 1.0275^x (28≦X≦75) where Y is the total length (mm) and X is the number of days after hatching. Growth rate changed after metamorphosis.     

A semi-artificial rearing system for the specialist predatory ladybird Cryptolaemus montrouzieri

In the present study a semi-artificial rearing system for the Australian ladybird Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), a specialist predator of mealybugs, was developed. In a first step, a rearing system using eggs of the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) as a food and synthetic polyester wadding as an oviposition substrate was compared with a natural rearing system using the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), as to its effects on the predator’s developmental and reproductive parameters. In a second series of experiments the performance of C. montrouzieri on bee pollen or on a mixture of E. kuehniella eggs and bee pollen was assessed. E. kuehniella eggs proved to be a suitable food to support larval development of the predator. Ladybird larvae reared on flour moth eggs developed two days faster and weighed approximately 10 % more than their counterparts reared on mealybugs. Despite a prolongation of the preoviposition period with ca. eight days and a decrease in egg hatch by about 10 %, C. montrouzieri females fed moth eggs accepted the synthetic wadding as an oviposition substrate and deposited the same number of eggs their counterparts maintained on mealybugs. A mixture of E. kuehniella eggs with pollen yielded similar developmental and reproductive rates as E. kuehniella eggs alone, but a diet of bee pollen alone was not adequate for the predator. Our findings indicate the potential of a rearing system using E. kuehniella eggs as a factitious food and synthetic wadding as an artificial oviposition substrate for the mass production of C. montrouzieri.     

New species of the genus Careproctus (Liparidae) from the Kara Sea with notes on spongiophilia,reproductive commensalism between fishes and sponges (Rossellidae)

A new species of the family Liparidae, fulvous snailfish Careproctus fulvus sp. n., is described from the Novaya Zemlya Depression of the Kara Sea at a depth between 190 and 414 m. The species belongs to the group of slit-eyed Careproctus (longitudinally oval pupil, elongated lower lobe of the pectoral fin, and large urogenital papilla). The representatives of the species are characterized by fulvous coloration with orange spots, deep body, small teeth, and three radials in the pectoral girdle. The eggs are deposited into glass sponges Schaudinnia rosea (Rossellidae). Valvatophilia (commensalism with bivalves) and carcinophilia (reproductive commensalism with crab-like decapod crustaceans of the family Lithodidae) have been registered in the family Liparidae before, but spongiophilia are described for the first time. Egg deposition into glass sponges (Rossellidae) is known also for cod icefishes (Nototheniidae) from Antarctic waters. Reproductive commensalism between the representatives of the family Liparidae in the Arctic, the species of the family Nototheniidae in the Antarctic, and glass sponges represents a new finding of bionomic bipolarity (independent appearance of similar adaptations in unrelated groups of fishes in two polar regions of the earth). Based on the ecologo-ethological classification of fish reproduction, brood hiding Careproctus species belong to ostracophils, a group of fishes deposited the eggs into live animals.     

Effect of the number of parasitoid (Apanteles kariyai) eggs [Hym.: Braconidae] on the growth of host (Leucania separata) larvae [Lep.: Noctuidae]

The developmental interactions between a gregarious endoparasitoid,Apanteles kariyai Watanabe and its host,Leucania separata Walker, were investigated. The parasitoid laid more eggs in older hosts. Host size increased gradiently as the instar advanced, but the number of eggs laid per host did not increase accordingly. The net weight of the host was correlated positively with the number of eggs laid and with the total weight of parasitoids, especially in cases of parasitization at 3rd (5th-instar type), 4th and early 6th instar where the correlation was significant at 1% level. It follows therefore that the more parasitoids there are relative to their host size, the more they contribute to make the host size larger.     

Observations onHexamermis albicans [Nematoda: Mermithidae] recovered fromLymantria dispar andStilpnotia salicis [Lep.: Lymantriidae] in west Germany and Austria

The mermithid,Hexamermis albicans (Siebold) was recovered from larvae ofLymantria (Porthetria) dispar (L.) collected from various localities in Burgenland, Austria in 1974 and 1975 and from Würzburg, Germany, in 1974. It was recovered also fromStilpnotia salicis (L.) in Austria in 1974. The mermithid was recovered from all field collected larval instars. The majority of the nematodes emerged fromL. dispar larvae collected as second and third larval instars although some nematodes were recorded from larvae collected as first instar larvae still on the egg mass. Peak emergence occurred in the laboratory during the period June 11–17 of both years, but emergence continued at a much lesser degree through the end of larval development. The nematode was found in both high and low host density populations. In 3 localities studied both years, there was a general increase in the percentage parasitism the second year. However, except for one locality in Austria in 1975 where individual samples produced up to 11% parasitism, the overall parasitism increased from 0.4% in 1974 to only 2.5% in 1975.     

Diversity in interspecific interactions between a nest-associating species, Pungtungia herzi, and multiple host species

Nest association in fishes affects the reproductive success of the host to varying degrees, from complete failure of the host’s reproduction to fitness advantages. Such varying impacts of nest association are considered to result from both the associate’s behavior and the characteristics of the host’s reproduction. To investigate the relationship between the impact of nest associate and host/associate ecology as well as evolutionary strategies involving nest association, we compared reproductive strategies and success between an associate East Asian minnow, Pungtungia herzi, and two host fishes (a goby, Odontobutis obscura, and a catfish, Pseudobagrus nudiceps) that have different reproductive ecologies. The associate frequently spawned around the days on which both hosts spawned, and gained a fitness advantage through continuous egg protection. Spawning by the associate had a negative effect on the survival of O. obscura eggs. Male O. obscura tended to abandon their nest when it was parasitized during the pre-spawning period. This is likely a tactic to alleviate the costs of brood parasitism. In contrast, survival of P. nudiceps eggs was consistently high in all nests, regardless of the intensity of associate’s spawning, and P. nudiceps young fed on cyprinid offspring (most probably the associate’s eggs/young) in the nest. Both P. nudiceps and P. herzi populations likely gain fitness benefits from their relationship. When comparing these two hosts with another known host, the freshwater perch Coreoperca kawamebari, the observed differences in the impact of nest association to the associate species likely correspond to differences in the spatial reproductive resources used by the respective hosts.     

The parasitoid complex of three noctuids [Lep.] in a northern Florida cropping system: Seasonal occurrence,parasitization, alternate hosts,and influence of host-habitat

Parasitoids of the cabbage looper,Trichoplusia ni (Hübner), the soybean looper,Pseudoplusia includens (Walker), and the tobacco budworm,Heliothis virescens (F.) were characterized in a 3.2-ha model of a north Florida (U.S.A.) cropping system (including tobacco (Nicotiana tabacum L.), soybeans (Glycine max (L.)Merr. and 18 other crops) not treated with chemical pesticides. The study was for a 2 yr-period; a minimum of three 0.0004-ha sections of row, or 0.0001-ha sections in broadcast or drilled crops were sampled weekly. In addition, sweeps with a net and some other sampling techniques were used in some crops.Litomastix truncatella (Dalman),Meteorus autographae Muesebeck, andVoria ruralis Fallen were the most important larval parasitoids recovered from cabbage loopers;Trichogramma spp. were by far the major egg parasitoid. Parasitization of eggs and larvae in crucifers (Brassica oleracea L.) ranged from 0 to 55% and 0 to 100%, respectively, and was generally highest during the spring and fall. Parasitization of cabbage looper immatures was highest in tomatoes (Lycopersicon esculentum Mill.). Parasitism by the parasitoid complex for the soybean looper larvae was high but eggs in soybeans were seldomly attacked by parasitoids. Tobacco budworm eggs were rarely parasitized in tobacco but were frequently parasitized in tomatoes and okra (Abelmoschus esculentus (L.)Medik). Parasitization of tobacco budworm larvae in tobacco was usually over 50% and was mostly byCardiochiles nigriceps Viereck; fewC. nigriceps were found from the other plants.     

Photoperiod as Cues for Determining Optimal Foraging in Developmental Stages in Chitala chitala Hamilton, 1822

Photoperiod plays an important role in controlling the feeding rhythmicity of juvenile fishes. Studies on feeding and spatial distribution pattern were made on wild populations of different juvenile stages of Chitala chitala, a threatened species in India. Results indicated that the prey preference of the fish increased with advancement of developmental stages. Moreover, nocturnal feeding was found to be more significant in the juveniles. Thus, feeding pattern of the different juvenile stages of Chitala is characterized by voracious predatory activity at dark condition. The vector controlling potential of the juvenile stages of Chitala specifically on mosquito and chironomid larvae was also significant. Studies on the distribution pattern of juvenile fishes were made with various combinations, viz. with or without food, in open surface and structured environments and observed during day as well as in dark regime. The juvenile distribution was clumped in open and closed environment during day time to minimize the chances of predation and juvenile mortality irrespective of food availability. A random distribution of juvenile fishes seemed to be advantageous for increasing feeding activity as observed in the experiment. This study is a pointer to the survival strategy of the larvae of C. chitala in their natural habitat which may be important from the perspective of conservation.     

Population Dynamic of the Mudskipper <Emphasis Type="Italic">Periophthalmus waltoni</Emphasis> Koumans, 1941 from the Bay of Hormozgan Province,Persian Gulf

We studied the population structure and reproductive biology of the mudskipper Periophthalmus waltoni Koumans, 1941, living on the mudflats of bay of Hormozgan province, Persian Gulf. The specimens were haphazardly and monthly collected from August 2008 to July 2009. A total of 2060 fishes was sampled, sexed 690 of which 221 (32%) were males, and 469 (68%) females. The total length (TL) and weight relationship demonstrated growth in both sexes was isometric with the function W = 0.0078TL^3.06. The asymptotic length (L∞) and growth coefficient (K) were estimated as 16.5 cm and 0.75 yr^–1, respectively. Age of the fish at zero length (to) was calculated–0.35 and the longevity was attained 3.65 year. The estimated Von Bertalanffy function was TL_(t) = 16.5[1–exp(–0.75(t + 0.35))]. Natural mortality (M) was estimated 1.74 yr^–1. Four cohorts were distinguished annuallywith mean of TL = 7.35, 10.17, 12.74 and 13.92 cm. The maximum recruitment rate was in January at 17.5%. The overall sex ratio (F: M) (1: 0.49) was significantly different than 1: 1. The peak of the gonadosomatic index (GSI) occurred in February. The size at onset of sexual maturity (LM₅₀)wasestimated at TL = 12 cm. The mean of absolute and relative fecundity were estimated as 3558 ± 2203 and 257 ± 101 eggs, respectively.     

Observations on the oviposition behaviour ofGoniozus sensorius [Hymenoptera: Bethylidae] a parasite ofDiaphania indica [Lepidoptera: Pyralidae]

Goniozus sensorius Gordh (Hymenoptera: Bethylidae) was recorded as a major parasite of the pumpkin caterpillar,Diaphania indica (Saunders) (Lepidoptera: Pyralidae). This paper provides detailed information on the oviposition behaviour ofG. sensorius. Prior to oviposition, the parasite temporarily paralyses the host larva. The paralysed condition lasts for about 2 h. The egg laying process on each larva requires 30 to 60 min. The maximum number of eggs are laid on the 6^th and 7^th segment, and none in the terminal segments. Generally, oviposition is restricted to 1 segment of the host larva and occasionally on 3 segments. The maximum number of eggs are laid on the 2^nd and 3^rd day after emergence and the mean number of eggs laid on each host larva was 7.1.     

Potential ofGeocoris punctipes [Hemiptera: Lygaeidae] andNabis spp. [Hemiptera: Nabidae] as predators ofEpilachna varivestis [Coleoptera: Coccinellidae]

Predation byGeocoris punctipes (Say) andNabis spp. onEpilachna varivestis Mulsant was studied in the laboratory at 26.7°C and in field cages containing soybeans. Both predator groups fed uponE. varivestis eggs, 1st, 2nd and 3rd stage larvae, but not upon 4th stage larvae, pupae, or adults. G. punctipes females produced significantly fewer eggs when fedE. varivestis eggs or 1st stage larvae than those fedGalleria mellonella (L.). Longevity of maleG. punctipes was significantly reduced when fedE. varivestis eggs; however, female longevity was not affected. Results from field cage tests indicated bothG. punctipes andNabis spp. could significantly reduce the density ofE. varivestis.     

Reproductive success of cat fleas,Ctenocephalides felis,on calves as unusual hosts

Abstract. Cat fleas, Ctenocephalides felis, were released onto calves as unusual hosts, and sampled at intervals for histological examination. Egg output from fleas on age-matched male and female calves was monitored. Using indicators of reproductive maturation and regression together with egg output data, the reproductive success and fertility of cat fleas on male and female calves were estimated. Comparisons were made with fleas taken from cats. The mean egg output of fleas on the bull calf was highly significantly different from that on the age-matched female calf: 28.14 ± 2.96 (SE) eggs/h compared with 16.21 ± 1.96 (SE) eggs/h. A higher proportion of sampled fleas (83.0%) was reproductively mature on the feline hosts compared with the calves (45.4-62.5%). Blue bodies resulting from oocyte resorption were present in the ovarioles of 10.4-19.0% of fleas sampled from the calves. No blue bodies were present in fleas removed from cats. Eggs laid by fleas on calves were viable and larvae were reared to adulthood. The mean percentage hatching success on the age-matched male and female calves was 46.7% and 51.7%. This represents a reduction in viability of 28-33% compared with eggs laid by fleas on cats. Factors which may account for reduced reproductive maturation of fleas on calves, including protein content of the host's blood, are discussed.     

Micrometeorological factors involved in development and survival of free-living stages of the sheep nematodesHaemonchus contortus andTrichostrongylus colubriformis. A review

Temperature and soil moisture are the most important factors affecting the development and survival ofHaemonchus contortus andTrichostrongylus columbriformis eggs and larvae on pasture. More than half of the eggs develop into infective larvae in the laboratory, but a very low percentage (0.03% forH. contortus) does so on pasture. There is a marked difference betweenH. contortus andT. colubriformis in survival of infective larvae.H. contortus larvae survived in the winter at Urbana poorly, whereasT. colubriformis did well. The former survived better than the latter in the spring and worse in the summer, while both survived equally well in the fall. Technics for larval recovery from pasture are not very efficient. Meteorologic conditions at ground level where the larvae exist are quite different from those in a standard weather shelter 1.6 m above the ground. Bioclimatographs in which mean monthly maximum temperatures are plotted against total monthly precipitation are fairly good in predicting the type of nematode liable to be important in a given region, but they are too simplistic to be relied on for more than approximations.     

Ontogenetic shift to dependence on salmon-derived nutrients in Dolly Varden char from the Iliamna River,Alaska

The upstream migration, spawning, and death of anadromous, semelparous Pacific salmon brings nutrients to terrestrial and aquatic communities around the Pacific Rim. Many fishes use these resources but the relationship between fish body size and the reliance on salmon-derived nutrients might follow one of several patterns related to the onset of egg consumption with body size as fish grow, and possible shifts to alternative prey such as fishes as they grow larger still. In this study, these size-dependent hypotheses of marine subsidy use by resident Dolly Varden, Salvelinus malma, were tested using diet and stable isotope analyses. S. malma did not shift abruptly to a reliance on salmon eggs after they became large enough to eat eggs (i.e., no gape limitation). Rather, fish large enough to eat eggs but < 150 mm showed diets that blended salmon nutrients with aquatic insects, likely because they were spatially segregated from the highest concentration of spawning sockeye salmon, Oncorhynchus nerka. From intermediate through the largest sizes observed (150 to > 600 mm long) S. malma received ca. 80 % of their nutrients from salmon (eggs, flesh, and maggots that had scavenged dead salmon) based on diet analysis and stable isotope ratios despite being large enough to consume fish, as many similarly-sized salmonids do in other ecosystems. The few fish sampled in June, prior to the availability of salmon subsidies, had stable isotope signatures that also reflected heavy (ca. 90 %) reliance on marine sources, likely because they had eaten little since the end of the salmon run the previous fall. This apparent avoidance of piscivory in favor a rich yet pulsed marine subsidy highlights the importance of healthy salmon runs for the sake of not only the salmon but resident fishes that consume them.     

The role of adult feeding in egg production and population dynamics of the checkerspot butterfly Euphydryas editha

Carbohydrate intake increases longevity, body weight maintenance and egg production in female Euphydryas editha. Amino acid intake leads to heavier eggs, larvae from which are more likely to survive. Females fed nectar produce more eggs in later masses than females which are not fed. During years of normal and below normal precipitation, larvae emerging from these later eggs are unlikely to reach obligatory size for diapause before their food dries up. On Jasper Ridge, where mortality is density-independent, nectar plays an important role increasing production of late egg masses during years of greater than normal rainfall when larvae from these masses are likely to reach diapause. The resulting large population increases, though infrequent, are probably important in maintaining population sizes large enough to reduce the chances of extinction during dry years.     

Fire Elicits an Adaptive Reproductive Strategy Shift from Host Plant Quantity to Quality in a Capital Breeding Species

Capital breeding species, those that do not acquire resources over their reproductive period, are hypothesized to have more flexible reproductive strategies than income breeding species, enabling the former to better cope with environmental changes. Yet, empirical study of this life history attribute in a changing environment is rare. Hemileuca eglanterina (Saturniidae), a strict capital breeding, day-flying moth, should employ a different reproductive strategy to exploit temporary increases in host plant nutrient quality following fire. In wetlands, where one half was burned and the other left unburned, the number of eggs/clutch was positively correlated with host plant abundance in the absence of fire, suggesting that H. eglanterina uses a resource abundance matching reproductive strategy by default. However, following fire, H. eglanterina laid greater numbers of eggs/clutch and did not adjust clutch size to host plant abundance, appearing to shift to a host plant quality based reproductive strategy. Coinciding with the fire-induced shift in reproductive strategy, host plants from burned habitat contained a greater proportion of N-containing compounds in their foliage than plants from unburned habitat, and larvae fed only leaves from the burned habitat had significantly greater survival than siblings fed unburned foliage. These results suggest the shift in reproductive strategy by H. eglanterina following fire was adaptive and that capital breeding species can cope with sudden environmental changes via alternative reproductive strategies.