Feeding resumption, morphological changes and mortality during starvation in Japanese flounder larvae

Japanese flounder Paralichthys olivaceus larvae established first feeding 3 days after hatching (DAH) at c . 17° C. Non-fed fish reached irreversible starvation at age 5 DAH. Non-fed fish showed similar feeding rate and feeding intensity as the fed fish when they were provided with prey before 5 DAH, after which the starved larvae did not feed even when prey became available. None of the six morphological measurements examined (total length, body height, eye height, head height, gut height and myotome height) showed significant differences between the non-fed and fed larvae until 5 DAH. Normal development continued only in the fed group, and the non-fed larvae showed reverse growth or body collapse after 5 DAH. Owing to the shrinkage and collapse at the top of head due to starvation, head height could be a sensitive indicator of starvation in Japanese flounder larvae. In the fed treatments, high mortality occurred from first feeding (3 DAH) to irreversible starvation (5 DAH), accounting for about two-thirds to three-quarters of the overall mortality (46–52%) throughout the experiments. This mortality was not prey density or larval density dependent. Mortality during the same period in the non-fed larvae accounted for about a third of the overall mortality (100%).     

First feeding and subsequent growth performances in piscivorous larvae of Chinese perch Siniperca chuatsi (Perciforms: Sinipercidae)

The success of first feeding is influenced by many factors, such as prey availability, and is critical to subsequent larval growth performances. To test the advantages of prey exposure before complete yolk absorption in piscivorous larvae, feeding incidence and specific growth rate were longitudinally measured in Chinese perch Siniperca chuatsi larvae first fed at different ages. The results showed that Chinese perch larvae were able to capture live piscine prey at 4 DAH (days after hatching), 1 day before complete yolk absorption. The feeding incidence and specific growth rate were higher in larvae first fed at 4 DAH than in larvae first fed at 5 or 6 DAH. These results indicate that prey exposure experience can facilitate the onset of first feeding, and that successful exogenous feeding, even before complete yolk absorption, is important for growth performances of piscivorous fish larvae.     

Diet composition,feed preferences and mouth morphology of early stage silver therapon (Leiopotherapon plumbeus,Kner 1864) larvae reared in outdoor tanks

This study examined the diet composition, feeding preferences, and mouth morphology of the silver therapon (Leiopotherapon plumbeus, Kner 1864) larvae under captive conditions. Larvae were reared in outdoor tanks (4 m³) with natural food grown 2 weeks prior to start of larval rearing. Food preference was measured by the Chesson's electivity index (α_i). Gut content analysis of larvae sampled between 5 and 25 days after hatching (DAH) showed the dominance in the diet by zooplankton, mainly copepod nauplii, cladocerans and insect larvae. Small fish larvae (5–9 DAH; 3.32–6.29 mm standard length) preferred cladocerans, ciliates and copepod nauplii; whereas older larvae (12–25 DAH; 5.45–19.26 mm standard length) preferred insect larvae over cladocerans and adult insects. The mouth gape size at 5 DAH was 359 μm and increased to 3.75 mm at 40 DAH when body size grew at an average rate of 0.59 mm d^?1. The standard length (SL) of L. plumbeus larvae was strongly associated with mouth size (r² = 0.98, P < 0.05), indicating a progressive increase of ingested prey size of the fish larvae. These results clarified the early life feeding ecology of this species, which is essential in developing effective hatchery techniques.     

Ontogenetic changes in the morphology and morphometry of Cuban gar (Atractosteus tristoechus)

Detailed examination of early development and growth of Cuban gar (Atractosteus tristoechus) was conducted using morphologic and morphometric characters. Larvae were reared at a constant water temperature (28 ± 1°C) from hatching to 18 days after hatching (DAH). Observation of the disappearance, reduction, or appearance of external structures, pigment characteristics, and behavior, identified three developmental stages (attached 0-3 DAH; transitional 4-10 DAH; and free-swimming 11-18 DAH). For the 18 day trial, the average growth rate was 1.30 mm/d and the specific growth rate averaged 10.2%/d. The slowest growth rates (0.02 mm/d and 2.8%/d, 7-11 DAH) coincided with the exhaustion of yolk reserves and the transition from endogenous to exogenous feeding. In addition to the slowest growth rates, the most dramatic morphological changes in A. tristoechus were observed during the transition from endogenous to exogenous feeding. Five total length (TL) groupings were established using 25 morphologic and morphometic characters. The characters snout length, pelvic fin length, snout width at nares, head length, and head width best identified length groupings. As the larvae developed, the snout and head lengthened and narrowed. Proportionally, the snout was narrower and the head longer in Cuban gar larvae than in other lepisosteid larvae.     

The effects of temperature on feeding in zooplanktivorous walleye,Stizostedion vitreum,larvae

Synopsis We examined the prey capture process in walleye larvae (9.8–18.0 mm mean length) feeding on zooplankton (density 1501^–1) in laboratory aquaria at 15,18.5 and 22°C. Larvae were starved for 8 h prior to the experiment and only allowed to feed for 10 min during the experiment in order to minimize the influence of gut processing or satiation on feeding behaviour. Prey consumption (g min^–1) increased exponentially and prey capture success (%) increased logarithmically with mean walleye length. Prey consumption and attack rate (strikes min^–1) increased significantly with increasing temperature. The effect of temperature on capture success was slight (2% increase from 15 to 22°C) and not significant. Walleye showed positive electivity for medium-sized prey (0.3–0.6 mm body width, mostlyCeriodaphnia quadrangula), negative electivity for small prey (0.3 mm, mostly cyclopoid copepods) and neutral electivity for large prey (0.6 mm, mostlyDaphnia sp.). Neither prey species electivity nor prey size electivity were significantly affected by temperature. However, prey size electivity did show a fairly large effect size with respect to temperature and we suggest that this relationship should be examined further. These results indicate that temperature affects prey capture in walleye larvae primarily by influencing attack rate.     

Intraspecific variation in Gape–prey size Relationships and Feeding Success During Early Ontogeny in Red Drum, Sciaenops Ocellatus

The relationship between predator gape and prey consumption in laboratory-reared larva and field-caught early juvenile red drum, Sciaenops ocellatus, was investigated in light of the hypothesis that feeding success varies throughout the early life history intervals of marine fishes. We expected the feeding ability of red drum to be more strongly constrained by mouth gape in smaller fish and expected this ability to improve with gape size. To test this hypothesis, field-caught, early juvenile red drum were examined to determine the relationship between gape size and prey size consumed. In field-caught early juveniles, gape (height and width) and prey size consumed (length and width) increased linearly with standard length (SL); however, mean width of prey consumed was only 20–47% of gape width. Furthermore, when regressed on SL, gape width yielded a higher slope than prey width. To further test this hypothesis on less developed, pre-metamorphic fish, age-specific differences in gape, number of prey and size of prey consumed prior to metamorphosis were determined from laboratory-reared red drum larvae. Similar patterns were observed for gape height– and gape width–SL relationships in laboratory-reared red drum larvae. Size of consumed prey increased from three days from hatching (dfh) to 18dfh. The percentage of feeding larvae also increased from 3% at 3dfh to 97% at 18dfh. In both field-caught, early juvenile red drum and laboratory-reared larvae, there was little evidence that the size of prey consumed was constrained by mouth gape. It is hypothesized that besides gape size, the development of other features of the feeding mechanism (e.g., hyoid and opercular series) influences prey-capture performance prior to settlement in marine fishes.     

Effects of the timing of initial feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae

The effects of delayed first feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae were examined under controlled conditions. Morphometric characters [yolk‐sac volume, oil globule volume, head depth (H_D), body depth (B_D), eye diameter (E_D), musculature height (M_H), mouth diameter (M_D) and total length (L_T)], body mass (M), specific growth rate (S_GR) and survival were evaluated under different first‐feeding time (2, 3, 4 and 5 days after hatching). Larvae began to feed exogenously at 2 days after hatching (DAH) and the point of no return (P_NR) occurred between 5 and 6 DAH at 23° C, range ±1·0° C. The yolk volume of larvae first‐fed at 2 days had a significant difference compared with that of larvae first‐fed at 3, 4 and 5 days on 3 and 4 DAH. The larvae first‐fed at 2 days achieved comparatively better growth performance than that of 3, 4 and 5 days. On 5 DAH, all morphometric characters had significant differences between 2 and 5 days and 2 and 4 days initial feeding, respectively. Total mortality was recorded on 9 DAH for the larvae first‐fed at 5 days. On 12 DAH, significant differences were observed between 2 and 4 days and 3 and 4 days initial feeding for all morphometric characters. From 16 DAH to the end of experiment, all growth variables of the larvae first‐fed at 2 days were significantly higher than those in other treatments. The S_GR (2–9 DAH) first‐fed at 2 and 3 days were significantly higher than 4 and 5 day treatments, and the S_GR (9–16 DAH) first‐fed at 2 days was significantly higher than 3 and 4 day treatments. There was no significant difference, however, of S_GR (16–28 DAH) among treatments. Survival rate was significantly higher at 2 days initial feeding (27·42%) when compared with 3 (15·96%) and 4 days (7·92%) initial feeding at the end of experiment. The present study suggests that the first feeding of S. scherzeri larvae should be initiated at 2 days after hatching for achieving good growth and survival.     

Influence of the forest caterpillar hunter Calosoma sycophanta on the transmission of microsporidia in larvae of the gypsy moth Lymantria dispar

• 1 The behaviour of predators can be an important factor in the transmission success of an insect pathogen. We studied how Calosoma sycophanta influences the interaction between its prey [Lymantria dispar (L.) (Lepidoptera, Lymantriidae)] and two microsporidian pathogens [Nosema lymantriae (Microsporidia, Nosematidae) and Vairimorpha disparis (Microsporidia, Burellenidae)] infecting the prey.
• 2 Using laboratory experiments, C. sycophanta was allowed to forage on infected and uninfected L. dispar larvae and to disseminate microsporidian spores when preying or afterwards with faeces.
• 3 The beetle disseminated spores of N. lymantriae and V. disparis when preying upon infected larvae, as well as after feeding on such prey. Between 45% and 69% of test larvae became infected when C. sycophanta was allowed to disseminate spores of either microsporidium.
• 4 Laboratory choice experiments showed that C. sycophanta did not discriminate between Nosema‐infected and uninfected gypsy moth larvae. Calosoma sycophanta preferred Vairimorpha‐infected over uninfected gypsy moth larvae and significantly influenced transmission.
• 5 When C. sycophanta was allowed to forage during the latent period on infected and uninfected larvae reared together on caged, potted oak saplings, the percentage of V. disparis infection among test larvae increased by more than 70%. The transmission of N. lymantriae was not affected significantly in these experiments.
• 6 Beetles never became infected with either microsporidian species after feeding on infected prey.
• 7 We conclude that the transmission of N. lymantriae is not affected. Because no V. disparis spores are released from living larvae, feeding on infected larvae might enhance transmission by reducing the time to death and therefore the latent period.

     

Feeding by the aquatic heteropteran,Diplonychus rusticum (Belostomatidae): an effect of prey density on meal size

The behaviour of Diplonychus rusticum feeding on chironomid larvae has been investigated under laboratory conditions. Changes in the percentage of material extracted from prey indicated that feeding for the first two minutes enabled the predator to obtain approximately 33% of the available food; feeding for 10 minutes resulted in only 60% extraction. Comparing the percentage of each prey consumed by D. rusticum exposed to various prey densities, it was apparent that predators were more wasteful and ate less of each prey as chironomid density increased. Because the rate of food intake declined as a greater proportion of each prey was extracted, predators exposed to high chironomid densities reduced the amount of each prey consumed thereby conforming to a simple optimal feeding model.     

Vulnerability of larval white perch,Morone americana,to fish predation

Synopsis The vulnerability of white perch, Morone americana, larvae to yearling bluegill, Lepomis macrochira, predators was examined in relation to larval size, nutritional condition and relative abundance of alternative prey. Short-term (15 min) predation trials were conducted in 381 tanks in the laboratory. Larval vulnerability was measured as the proportion of larvae killed and the proportion of successful attacks per predator in each 15 min trial. No significant differences in vulnerability were apparent among larvae regardless of feeding history at sizes < 6 mm SL. At larval lengths > 6 mm SL, size of larvae was the crucial determinant of their vulnerability. Percentage of larvae killed in 15 min was nearly 100% at sizes < 6 mm SL, decreased to 30% at a length of 12.0 mm SL and dropped to 18% at 14.0 mm SL. Larvae initially feeding at low food levels for 2–4 d exhibited decreased growth of 13–25% over the first 3 wks of life, and simulations based on laboratory results indicated that these growth deficits could result in 5- to 68-fold decreases in survivorship at 38 days after hatching (DAH). The relative abundance of alternative prey also had a pronounced effect on mortality of larvae. A 10-fold increase in alternative prey (Daphnia magna) abundance decreased bluegill predation rates on white perch larvae by 10–20%, while a 100-fold increase in Daphnia density decreased larval mortality by 75–90%.     

Red porgy (Pagrus pagrus) larval feeding performance and behavior at the onset of exogenous feeding

The feeding performance and behavior at the onset of exogenous feeding, 3 to 4 days after hatching (DAH), were studied in red porgy Pagrus pagrus larvae. Similar feeding efficiency and intensity were achieved for two feeding treatments (live or freeze-dried rotifers) suggesting that prey movement is not decisive for their detection and capture and demonstrating that at first feeding red porgy larvae can ingest inert food. Larvae feeding performance was not affected by a diet shift between treatments. Based on maximum rotifers consumption and gut evacuation time at 18 °C, the daily ration was estimated as 14.035 μg, considering 14 h of feeding and a 25% egg:female rotifer ratio. Larval swimming activity measured by video recording showed a close association with gut fullness and similar swimming patterns for 3 and 4 DAH larvae. However, 20.3% larger mouth gape and 54.6% higher swimming speed of the older larvae should provide a better feeding performance and more energy needed for growth.     

A continuous flow-chamber to study prey preferences of Golden Perch (Macquaria ambigua Richardson) larvae

This paper describes the use of a continuous-flow chamber for maintaining small and fragile fish larvae and their prey in a healthy state and under suitable conditions over a 24 h period for studies on prey preferences. Survival of golden perch (Macquaria ambigua Richardson) larvae and prey was high and ten replicates on food preferences were carried out simultaneously. The larvae preferred small Daphnia carinata King (780–860 m) over larger ones (2000–3120 and 3680–5440 m) and preferred cladocerans (Daphnia carinata King and Moina micrura Kurz) over calanoids (Boeckella de Guerne & Richard). The chamber is also suitable for studies on feeding behaviour and diet requirements of fish larvae.     

云斑尖塘鳢仔鱼摄食节律的研究

对自然光照条件下云斑尖塘鳢仔鱼的昼夜摄食节律和在夜间增加不同强度外光源条件下仔鱼的摄食发生率进行了研究。结果表明,云斑尖塘鳢仔鱼具有明显的昼夜摄食节律,晚上摄食发生率是著高于白天,其摄食主要集中在光线较弱的16:00～00:00;5日龄仔鱼在100～500Lx,8日龄和12日龄仔鱼在10～100Lx光照条件下的摄食发生率要明显高于黑暗或更高光照条件下的摄食发生率。     

Detecting predation and scavenging by DNA gut-content analysis: a case study using a soil insect predator-prey system

White grubs (larvae of Coleoptera: Scarabaeidae) are abundant in below-ground systems and can cause considerable damage to a wide variety of crops by feeding on roots. White grub populations may be controlled by natural enemies, but the predator guild of the European species is barely known. Trophic interactions within soil food webs are difficult to study with conventional methods. Therefore, a polymerase chain reaction (PCR)-based approach was developed to investigate, for the first time, a soil insect predator-prey system. Can, however, highly sensitive detection methods identify carrion prey in predators, as has been shown for fresh prey? Fresh Melolontha melolontha (L.) larvae and 1- to 9-day-old carcasses were presented to Poecilus versicolor Sturm larvae. Mitochondrial cytochrome oxidase subunit I fragments of the prey, 175, 327 and 387 bp long, were detectable in 50% of the predators 32 h after feeding. Detectability decreased to 18% when a 585 bp sequence was amplified. Meal size and digestion capacity of individual predators had no influence on prey detection. Although prey consumption was negatively correlated with cadaver age, carrion prey could be detected by PCR as efficiently as fresh prey irrespective of carrion age. This is the first proof that PCR-based techniques are highly efficient and sensitive, both in fresh and carrion prey detection. Thus, if active predation has to be distinguished from scavenging, then additional approaches are needed to interpret the picture of prey choice derived by highly sensitive detection methods.     

Feeding ecology of larval and juvenile black seabream (Acanthopagrus schlegeli) and Japanese seaperch (Lateolabrax japonicus) in Tolo Harbour, Hong Kong

Black seabream, Acanthopagrus schlegeli, and Japanese seaperch, Lateolabrax japonicus, are important commercial species in the coastal waters of western Pacific Ocean, including Japan, Korea and China. In Hong Kong, larvae and juveniles of these two species occur in bays and estuaries during late winter and spring. This study reports on the ontogenetic changes in food habits in larvae and juveniles of these species in an artificial rocky shore area. Copepods and cladocerans were the most numerous food items for black seabream. There was a shift to larger and benthic prey as the fishes grew. Japanese seaperch <2.1cm fed predominantly on copepods and cladocerans, while larger prey were added as fish size increased. Japanese seaperch >6.0cm were piscivorous. Maximum prey width increased with fish standard length and mouth gape width in both species. Overall, black seabream showed greater diet breadth than did Japanese seaperch. In black seabream, diet breadth increased with fish size. In Japanese seaperch, diet breadth increased with size for fishes <4.0cm, then decreased as the fishes became piscivorous. Prey selectivity in black seabream was determined using information on prey availability in plankton samples. In general, preference was stronger for cypris larvae, Penilia avirostris and decapod larvae than for copepods and podonids. In recent years, overfishing and environmental degradation have led to the decline of fish populations in Tolo Harbour. Absence of fishes with empty gut indicates that inner Tolo Harbour is still an important nursery area for these two commercial species.     

An experimental study on the foraging behavior of a pit-building antlion larva,Myrmeleon bore

Foraging behavior of a pit-building antlion larva, Myrmeleon boreTjeder was investigated experimentally to elucidate the relation between the feeding level and pit relocation.

1. In artificial sands constructed in the field the 3rd instar larvae of M. bore rarely changed the positions of their pits, though several antlions had moved actively until they constructed pits. The average feeding rate was 0.3 prey/day/pit, and about 60% of prey captured were ants.
2. To examine whether or not M. bore larvae concentrate into the area where they can capture more prey, 8 antlions were released into each of 6 boxes filled with sand. I divided the sand surface of each box into two half areas, then gave prey to the pits built in a half area and gave no prey to the pits built in the other half. During the 50-day observation period, nonfed antlions never moved into the area where prey were given.
3. The 3rd instar larvae were reared separately without food. Even under starved conditions they rarely relocated their pits until dealth. The average duration of survival period was 83.9 days.
4. The experimental results indicate that M. bore larvae adopt a tactic of sedentary ambushing. These larvae exhibit low movement rates which are independent of prey capture rates.

     

Histological studies on the development of the digestive system of the clownfish Amphiprion percula and the time of weaning

This study investigates the histological development of the digestive system of the common clownfish, Amphiprion percula Lacépède 1802, as a means to predict the time when the early juveniles can begin to digest inert feeds. The incubation period is completed within 7 days. At the time of hatching the alimentary canal is advanced and larvae start exogenous feeding immediately. Three days after hatch (DAH) the yolk sac is completely absorbed and at 5 DAH small supranuclear inclusions appear in the hindgut epithelium, suggesting pinocytotic digestion. At 7 DAH gastric glands are established in the epithelium of the stomach and by 9 DAH supranuclear inclusion vacuoles have appeared in the epithelium of the midgut, indicating extracellular digestion and absorption across the lumen. It was concluded that A. percula could only effectively digest artificial feeds from 9 DAH.     

Predation on crown-of-thorns starfish larvae by damselfishes

Examining the functional response of predators can provide insight into the role of predation in structuring prey populations and ecological communities. This study explored feeding behaviour and functional responses of planktivorous damselfishes when offered captive reared larvae of crown-of-thorns starfish, Acanthaster sp., with the aim of determining whether these predators could ever play a role in moderating outbreaks of Acanthaster sp. We examined predatory behaviour of 11 species of planktivorous damselfish, testing: (1) the relationship between predator size and predation rate, both within and among fish species; (2) consumption rates on larvae of Acanthaster sp. versus larvae of a common, co-occurring coral reef asteroid Linckia laevigata; (3) maximal feeding rates upon both Acanthaster sp. and L. laevigata; and (4) functional responses of planktivorous fishes to increasing densities of Acanthaster sp. Consumption rates of crown-of-thorns larvae by damselfishes were independent of predator size; however, there was a significant negative relationship between predator size and consumption rate of L. laevigata, when pooling across all predatory species. Some damselfishes, including Acanthochromis polyacanthus and Amblyglyphidodon curacao, consumed larval Acanthaster sp. at a greater rate than for L. laevigata. Most predatory species (all except A. curacao and Pomacentrus amboinensis) exhibited a Type II functional response whereby the increasing feeding rate decelerated with increasing prey density. In addition to revealing that a wide range of planktivorous fishes can prey upon larvae of Acanthaster sp., these data suggest that planktivorous damselfishes may have the capacity to buffer against population fluctuations of Acanthaster sp. Importantly, predators with Type II functional responses often contribute to stability of prey populations, though planktivorous fishes may be swamped by an abnormally high influx of larvae, potentially contributing to the characteristic population fluctuations of Acanthaster sp.     

Fungal endophytes of grasses and their effects on an insect herbivore

Summary The effects of endophytic fungi (Tribe Balansiae, Clavicipitaceae, Ascomycetes) of grasses on an insect herbivore were studied by feeding paired groups of larvae of the fall armyworm (Spodoptera frugiperda, Noctuidae, Lepidoptera) leaves from either infected or uninfected individuals. Perennial ryegrass infected by the Lolium endophyte, tall fescue infected by Epichloe typhina, dallisgrass infected by Myriogenospora atramentosa, Texas wintergrass infected by Atkinsonella hypoxylon, and sandbur infected by Balansia obtecta were utilized. The endophytes of ryegrass and fescue previously have been shown to be toxic to mammalian herbivores and to deter feeding of some insect herbivores. In this study we extend the antiherbivore properties of those endophytes to the fall armyworm and demonstrate that fungal endophytes in three other genera have similar antiherbivore properties. For most grasses, survival and weights of fall armyworm larvae fed infected leaves were significantly lower and larval duration was significantly longer compared to larvae fed uninfected leaves. Resistance to herbivores may provide a selective advantage to endophyte-infected grasses in natural populations.     

Predation by wasps on lepidopteran larvae in an Ozark forest canopy

ABSTRACT.

• 1 Predation by birds, crawling arthropods (ants, harvestmen, spiders), and social wasps (Vespula) spp. on introduced stocks of Heliothis virescens (Fabricius) larvae was investigated in a oak-hickory forest canopy in northwestern Arkansas (U.S.A.).
• 2 Wasps, Vespula maculifrons (Buysson) and V.squamosa (Drury), removed over 90% of the larvae. Repeated visits to a feeding site by the same marked wasps accounted for removal of either a single larva or all larvae. Larvae pinned (punctured) to artificial leaves were selected over 70% of the time by wasps when compared to attachments that did not puncture larvae; however, unpunctured larvae were taken.
• 3 Crawling arthropods accounted for low levels of predation, and birds did not appear to prey on larvae. Apparently wasps removed larvae rapidly and efficiently, thereby depleting the feeding sites before other predators discovered the larvae.
• 4 Although attaching larvae to artifical hickory leaves provided an easy method for placing larvae into the forest canopy, a lower percentage of larvae were removed from these leaves compared to natural hickory leaves. Moving feeding sites did not influence the number of larvae taken.