Competitive Interactions between Hydrilla (Hydrilla verticillata) and Vallisneria (Vallisneria americana) as Influenced by Insect Herbivory

Two experiments (winter and summer) were conducted in outdoor tanks using addition-series methods to evaluate the impact of specialized feeding by two biological control agents,Hydrellia pakistanaeDeonier andBagous hydrillaeO'Brien, on competitive interactions between hydrilla [Hydrilla verticillata(L.f.) Royle] and vallisneria (Vallisneria americanaMichx). Competitive abilities of each plant species were determined using the reciprocal-yield model of mean plant weight. In the absence of the biocontrol agents, intraspecific competition from hydrilla on itself was 8.3 times stronger than interspecific competition from vallisneria.Hydrellia pakistanaeinterfered with hydrilla canopy formation by removing as much as 80% of the plant biomass in the top 30 cm of the water column. Damage byH. pakistanaealso caused a 43% reduction in hydrilla tuber production during the winter experiment. Similarly,B. hydrillaecaused up to a 48% reduction in hydrilla plant weight in the summer experiment. Neither insect species damaged vallisneria. As a result, there were significant shifts in the competitive balance between hydrilla and vallisneria due to selective insect feedings. In the presence ofH. pakistanae, hydrilla intraspecific competition was nearly equal to interspecific competition from vallisneria, indicating that hydrilla had lost its competitive edge over vallisneria.Bagous hydrillaealso produced similar, but smaller, shifts in the relative competitive abilities of hydrilla and vallisneria. These results indicate that biological control agents can disrupt the competitive balance between plant species in favor of native species, thus adding another element to the weed biological control strategies.     

Assessing Spirulina platensis as a dietary supplement and for toxicity to Rhynchophorus ferrugineus (Coleoptera: Dryopthoridae)

Insects are important for humanity; play role in crop pollination, and biocontrol of harmful pests. The red palm weevil, Rhynchophorus ferrugineus, is a major pest of date palms and has become a serious threat. Scientists needs ample numbers of insects for bioassays to explore control options. The alga Spirulina platensis, is enriched by protein, natural vitamins, minerals, and amino acids, stimulate the development of organisms that feed on it. I assessed the value of Spirulina as a nutritional supplement for red palm weevil larvae by adding its various percentages to the artificial diet. Once a week, the larvae were removed from the containers, washed with distilled water, dried, weighed using an electronic scale, returned to a new container, and supplied with Spirulina mixed fresh diet. Larvae fed with lower concentrations showed vigorous growth and significant weight gain. Particularly, larvae fed 0.5%, 1%, and 2% Spirulina powder supplementation to their diet were healthier and gained more weight than larvae reared with >5% concentration. Overall 40% mortality was recorded in larvae fed with 10% concentration. Higher concentrations were lethal, and all larvae died within two weeks when fed 20% Spirulina. The present research findings indicate that Spirulina used in concentrations from 0.5% to below 5% had a beneficial effect on red palm weevil larval growth but a detrimental effect and even mortality was recorded when used ≥5%.     

Host specificity testing and suitability of the parasitoidMicroctonus hyperodae (Hym.: Braconidae,Euphorinae) as a biological control agent ofListronotus bonariensis (Col.: Curculionidae) in New Zealand

The behaviour of the parasitoidMicroctonus hyperodae Loan was studied under quarantine conditions to determine its likely host range in New Zealand. The species was imported from South America as a potential biological control agent of Argentine stem weevil,Listronotus bonariensis (Kuschel). The study involved systematic evaluation of the parasitoid's behaviour when exposed to 24 non-host weevil species; all but three of these were native to New Zealand. Of those tested, four were found to sustain someM. hyperodae development. However, further examination showed that in all but one species,Irenimus aequalis (Broun), parasitoid development was impeded, with up to 50% of the larvae becoming encapsulated. Overall, those weevil species that were attacked produced only 19% of the parasitoids derived fromL. bonariensis controls. As an adjunct to this quarantine study, a review of the habitats of the native weevil and target pest populations indicated that refugia would probably exist for native alpine species. I. aequalis was not considered to be threatened byM. hyperodae as this weevil has benefited from the advent of European agricultural systems to the extent that it is now recognised as a minor pest. In view of its relatively oligophagous behaviour, the parasitoid was recommended as suitable for release.      

Development of larval diets for milkfish (Chanos chanos)

This study aimed to develop nutritionally balanced and cost-effective processed diets for milkfish larvae ( Chanos chanos Forsskal). Two larval diets (feed A and feed B) were formulated and prepared to contain 45&percnt| protein and 10&percnt| lipid. Several larval diet preparations were tried such as microbound/ unpelleted (freeze-dried), microbound/pelleted (oven-dried) and microbound/flaked (drum-dried) and assessed in terms of feed particle size and buoyancy, water stability and feed acceptability. The preparation that gave the best particle size and buoyancy as well as good water stability was prepared as the microbound diet (using K -carrageenan as a binder) and flaked using a drum drier. A series of feeding experiments were conducted to determine the growth and survival of milkfish larvae reared on various feeding schemes using these processed larval diets which were fed either solely or in combination with live feed. Larvae in control treatments were reared on live foods such as Brachionus plicatilis and Artemia nauplii. Larvae were observed to ingest the diets, indicating that the feeds had suitable physical characteristics and were attractive to the larvae. The overall results of the feeding trials showed that the artificial diets could be fed to milkfish larvae in combination with Brachionus rotifers starting on day 2 or day 8, and could be fed alone starting from day 15. These promising results would reduce the dependence of milkfish larvae on live feed and would have significant economic benefits in the form of simplified milkfish hatchery procedures.     

Biology and host preferences of Cryptorhynchus melastomae (Coleoptera: Curculionidae), a possible biocontrol agent for Miconia calvescens (Melastomataceae) in Hawaii

The introduced plant Miconia calvescens (Melastomataceae) poses a grave threat to Hawaii's native ecosystems and biodiversity. One potential candidate for classical biological control is Cryptorhynchus melastomae (Coleoptera: Curculionidae: Cryptorhynchinae), a stem-boring weevil from Central and South America. This weevil feeds on M. calvescens in its native Costa Rica and has been successfully reared under greenhouse conditions. Comparison of its environmental conditions in Costa Rica with those in the Miconia infested areas of Hawaii indicates the latter is a suitable habitat for C. melastomae. C. melastomae has one or two generations per year. Adults feed on new stems, petioles, leaf buds, veins, and lamina, whereas larvae mine the stem until pupation. Adults appear to prefer saplings for oviposition and feeding. Under greenhouse conditions both adults and larvae can seriously damage and kill small M. calvescens. Preliminary host testing indicates that C. melastomae may be family specific on Melastomataceae. However, because Hawaii lacks native melastomes and has many other serious melastome weeds, a family specific insect may be suitable as a biocontrol agent in this case.     

Selection of plant parts by Depressaria multifidae (Lep., Oecophoridae) on its seasonally-restricted hostplant, Lomatium grayi (Umbelliferae)

ABSTRACT.

• 1 Depressaria multifidae Clarke feeds on a broader variety of Umbelliferae plant parts than other Depressaria species.
• 2 Early instar larvae feed in the sheaths surrounding floral buds and leaves. Later instar larvae feed in the sheaths and floral stems and on flowers and leaves.
• 3 Floral stems bored by larvae had significantly larger basal stem diameters than floral stems that were not bored. Smaller stems usually have umbels with only male flowers, and wither after flowering, too soon for larvae to complete development. In contrast, larger stems often have umbels with some hermaphroditic flowers, which remain green and erect long enough for larvae to complete development. Hence, selection may favour larvae that bore only in relatively large stems.
• 4 In the laboratory, larvae fed sheaths with enclosed floral buds, flowers, or leaves all pupated at the same weight, but larvae fed floral stems pupated at a significantly lower weight. Larval and pupal development time was the same on all plant parts.
• 5 In the field, larvae restricted to a single umbel throughout development pupated at the same weight as those restricted to a single leaf.
• 6 Unlike in other Depressaria species, nitrogen levels only partly correspond to the pattern of use of plant parts in D.multifidae. Nitrogen values varied as follows: floral buds > immature leaves ≥ flowers > floral stalks > sheaths excluding floral buds or leaves.
• 7 The broad variety of plant parts used by D.multifidae may result partly from the problem of feeding on a small, seasonally restricted hostplant; the greater use of sheaths and floral stems than in other Depressaria species may result from selection for safety from parasites or predators.
• 8 The results for D.multifidae indicate that the way in which an insect feeds on a plant species can vary broadly even at a single site.

     

Ecological studies on Thrips imaginis Bagnall (Thysanoptera) in flowers of Echium plantagineum L. in Australia

Aspects of the ecology of Thrips imaginis Bagnall in flowers of Echium plantagineum L. are described and subjected to experimental analysis. Thrips eggs were mostly laid in plant parts that were not lost when the short-lived flowers abscissed. The abundance of adults and larvae in flowers from the bud stage through to abscission was determined. Larvae usually required more than one flower to complete development and so had to migrate between flowers to survive. Larvae generally remained between the bases of the stamen filaments when in direct sunlight, but moved along the filaments to the anthers for rapid pollen feeding during low light intensity, especially at night. There was little spatial and temporal overlap between thrips larvae and honeybees in the flowers. Ants can cause much damage to the flowers and can feed on thrips. Pollen feeding of T. imaginis is described. The species of pollen grain affects feeding, and this may influence breeding success. Low u.v.-reflecting white, blue and yellow water traps caught more T. imaginis that green, red, black and high u.v.-reflecting white. These results agree well with the numbers of adults in several native and non-native flowers of various colours. Adult female thrips colour variation is correlated with for ewing length, and hence reflects factors acting on a pre-adult stage.     

Reproduction and Development of the Biocontrol AgentHydrellia pakistanae(Diptera: Ephydridae) on Monoecious Hydrilla

Previous investigations of the laboratory biology and host range ofHydrellia pakistanae,a biological control ofHydrilla verticillata(hydrilla), used the dioecious hydrilla biotype common to Florida, Texas, and California. A monoecious biotype that is now spreading throughout the mid-Atlantic states, California, and Washington was not investigated during these original studies. We therefore compared the dioecious and monoecious hydrilla biotypes as hosts forH. pakistanae.FemaleH. pakistanaeaccepted the two biotypes equally as ovipositional substrates. Overall developmental success differed little: 42% of eggs oviposited on monoecious hydrilla produced adults compared to 39% of eggs oviposited on dioecious hydrilla. Fly development required about 33 days on both biotypes (at 22 ± 2°C), but larvae that completed development mined 1.6 times as many leaves on monoecious hydrilla as on dioecious plants. These data suggest thatH. pakistanaewould be a useful biocontrol agent of monoecious hydrilla, should this plant invade areas where it can grow as a perennial.     

Host range of the leaf-tier Tentamen atrivirgulatum Metz (Lepidoptera: Gelechiidae); an unsuitable candidate for biological control of Brazilian peppertree

ABSTRACT

The life history and host range of the South American leaf-tier Tentamen atrivirgulatum Metz, 2019 (Lepidoptera: Gelechiidae) was evaluated to determine its suitability for classical biological control of invasive Brazilian peppertree, Schinus terebinthifolia, in the USA. Larvae were collected during a survey in the native range of Brazil feeding on Brazilian peppertree. A quarantine colony was established and no-choice tests were conducted to determine the host range of this species. The results of these tests indicated that the larvae fed and completed development on seven of the eleven non-target species tested. Percent survival on these non-targets ranged from 20% to 100%. Larval survival was 50% when fed the target weed Brazilian peppertree. When larvae were fed leaves of these non-targets, pupal weights were significantly lower only for those fed Pistacia chinensis. Development time to the pupal and adult stages did not differ with larval diet. These no-choice results indicate T. atrivirgulatum larvae have a broad host range and thus this species will not be developed as a biological control agent for Brazilian peppertree in the USA.     

Effect of feed on larvae of Macrobrachium malcolmsonii (H. Milne Edwards) reared in synthetic brackishwater

Freshwater prawn, Macrobrachium malcolmsonii, has potential for aquaculture. Larvae of M. malcolmsonii were reared in synthetic brackishwater using commercial salts. Live and artificial feeds were provided to larvae either individually or in combination. Survival was significantly higher when larvae were fed with live feed only. However, larvae fed with artificial feed showed significantly lower survival. Survival was significantly higher when Artemia combined together with other feeds. Despite its limitations, synthetic brackishwater can be used for freshwater prawn seed production.     

Life cycle and host specificity ofEutinobothrus sp. (Col.: curculionidae) an agent for biological control ofSida acuta (malvaceae) in the northern territory,Australia

The biology of an undescribed weevil,Eutinobothrus sp., and its specificity toSida acuta, a serious weed in northern Australia, were studied in a quarantine facility in Australia. Sixty-eight plant species were screened and onlyS. acuta andS. rhombifolia could sustain populations ofEutinobothrus sp. Adults feed externally on the stems and oviposit in feeding scars. Larvae feed internally and pupate in the stem. Prepupae and pupae may aestivate in the stem and adults emerge with the onset of the wet season when new growth is evident.Eutinobothrus sp. was released in January, 1994 in the Northern Territory and has established.     

Larvae of Nymphulinae (Lepidoptera: Pyralidae) associated with Hydrilla verticillata (Hydrocharitaceae) in North Queensland

Abstract  Australian Nymphulinae are a diverse group of moths with aquatic caterpillars that probably play an important role in determining the composition and abundance of aquatic macrophytes in Australian freshwater systems. Less than 10% of the nymphuline larvae in Australia have been described. As part of a project to develop biological control agents for hydrilla, Hydrilla verticillata , we encountered a variety of Nymphulinae larvae feeding on this and other aquatic plants. We illustrate, describe and provide a key to five species of Nymphulinae larvae ( Ambia ptolycusalis (Walker), Parapoynx diminutalis Snellen, Hygraula nitens Butler, Margarosticha repititalis (Warren) and Theila siennata (Warren)) that feed on hydrilla in North Queensland. Information on their host plants also is included. Our field research indicates that none of these species should be considered as potential biological control agents for hydrilla.     

Using food for different purposes: female responses to prey in the predator Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Abstract.  1. Although predatory insects often feed on diverse prey, their reproductive activity may be linked most strongly to a more restricted range of prey. The propensity of adult females of the ladybird beetle, Coccinella septempunctata L., to attack two natural prey species, pea aphids [ Acyrthosiphon pisum (Harris)] and alfalfa weevil larvae [ Hypera postica (Gyllenhal)], was compared, and the degree to which ladybird egg production depends on consumption of aphids vs. weevils was assessed.
2. Coccinella septempunctata females more readily attacked aphids than weevil larvae. This was true regardless of whether females had fed previously on aphids or on weevil larvae.
3. When females were provided with few to many aphids daily, or few aphids plus an excess number of weevil larvae, their rates of egg production depended primarily on the number of aphids consumed.
4. Addition of weevil larvae to diets of limited numbers of aphids increased egg production, but only modestly. Thus, consumption of weevil larvae may have served mostly for self-maintenance, thereby enabling females to use for egg production more of the nutrients and energy obtained from limited consumption of aphids.
5. The females' linkage of egg production primarily to aphid rather than weevil consumption may be adaptive, as their offspring are much less able as larvae to survive and mature on a diet of weevils rather than aphids.     

Host range and searching behaviour of Cricotopus lebetis (Diptera: Chironomidae), a tip miner of Hydrilla verticillata (Hydrocharitaceae)

A chironomid midge, Cricotopus lebetis Sublette (Diptera: Chironomidae), was discovered feeding on Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) in Crystal River, Citrus, Co., Florida, in the 1990s. Larvae of the midge mine the apical meristems of hydrilla, causing terminal branching and stunting of the plant. We investigated the fundamental host range of the midge by conducting a series of no-choice and paired-choice tests. No-choice developmental tests with neonate larvae revealed that the fundamental host range of C. lebetis included not only on hydrilla but also several other aquatic plants in different families, suggesting that this insect is not a hydrilla specialist. In paired-choice bioassays, larval colonisation of Elodea canadensis Michx. (Hydrocharitaceae) and Najas guadalupensis (Spreng.) Magnus (Najadaceae) was greater than colonisation of H. verticillata. Behavioural bioassays in a Y-tube olfactometer and in Petri dishes suggested that neonate larvae were not able to locate host plant material, whereas older larvae were successful in finding hosts. In paired-choice oviposition tests, adult females discriminated between potential oviposition sites, with greater numbers of eggs laid on E. canadensis and N. guadalupensis than on H. verticillata. This study is the first detailed account of host searching and oviposition behaviour of a phytophagous chironomid midge. The results will be used to assess the potential value of C. lebetis as a biological control agent of hydrilla.     

Biology of Polypedilum n. sp. (Diptera: Chironomidae), a promising candidate agent for the biological control of the aquatic weed Lagarosiphon major (Hydrocharitaceae) in Ireland

Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae), an aquatic macrophyte native to Southern Africa that has become invasive in several countries worldwide, is a potential target for biological control. Biology studies were conducted on Polypedilum (Pentapedilum) n. sp. near reei Oyewo & Sæther (Diptera: Chironomidae), a midge whose larvae were discovered mining the plant's shoot tips in its native range. Field surveys indicated that the midge occurred only at a small number of sites but attained high densities (up to 370 shoots damaged/m²) that prevented further growth from the shoot tips. A population of the midge was imported into quarantine in Ireland to evaluate its potential as a candidate biological control agent. The adult stage is terrestrial and short-lived (4–5 d), with females depositing one–two egg packets into the water bodies. First-instar larvae fed externally on the stems and leaflets. Later instars fed on the apical meristems and burrowed into the shoot tips, with resultant damage stunting the apical growth. Larvae moved readily between shoots to complete their development and pupated within the tunnels excavated by the late instar larvae. Developmental time to adulthood ranged from 31 to 49 days at 20.7°C and a 15 L:9-D cycle. This is the first time that a chironomid has been imported and successfully cultured for consideration as a classical biological control agent. Several aspects of the midge's biology suggest that host specificity testing is warranted to determine its potential as a biocontrol agent of L. major.     

Insecticidal effects of extracts of seven plant species on larval development, alpha-amylase activity and offspring production of Tribolium castaneum (Herbst) (Insecta: Coleoptera: Tenebrionidae)

Bioinsecticidal effects of methanol extracts from seven plant species on Tribolium castaneum were investigated. Centaurium erythraea, Peganum harmala, Ajuga iva, Aristolochia baetica, Pteridium aquilinum and Raphanus raphanistrum extracts inhibit growth of larvae. C. erythraea was the most toxic with 63% mortality 10 days after treatment, followed by P. harmala with 58%. C. erythraea and P. aquilinum reduce the emergence rate respectively of 66% and 19%. The duration of larval period was shortened by Launaea arborescens, P. aquilinum and A. iva extracts, whereas R. raphanistrum and P. harmala extracts extend the larval period when compared to the control. Extracts of C. erythraea, P. harmala, A. iva and A. baetica inhibited F1 progeny production. Larvae possess three alpha-amylase isoforms as determined by SDS-PAGE. Larvae fed on treated diet had lower alpha-amylase activity than larvae feed on untreated diet. C. erythraea and P. harmala are the most potent extracts. These plant extracts could be useful to reduce seed damage caused by this pest species.     

The Life History and Host Range of Charidotis pygmaea (Col.: Chrysomelidae), a Biological Control Agent for Lantana montevidensis (Verbenaceae)

The life cycle and host range of Charidotis pygmaea Klug were investigated to assess its suitability for release as a biological control agent for Lantana camara L. and L. montevidensis (Sprengel) Briquet. Adults fed and deposited eggs on the underside of leaves of both species. They generally laid fewer eggs in the dry winter months when lantana yellows or drops its leaves. Larvae fed on the upper leaf surface and pupation occurred on the leaves or stems. Development from egg to adult took approximately 50 days. Survival to the adult stage was greater, and the development time was shorter on L. montevidensis than on all varieties of L. camara tested, suggesting that the agent would be ineffective against L. camara. Forty-two plant species were tested to determine host specificity in choice oviposition and larval feeding trials. These demonstrated that C. pygmaea did not pose a threat to non-target species. Consequently, C. pygmaea was approved for release in Australia and through its ability to survive the dry season, should assist in the control of L. montevidensis.     

Alcidodes sedi (Col.: Curculionidae), a natural enemy of Bryophyllum delagoense (Crassulaceae) in South Africa and a possible candidate agent for the biological control of this weed in Australia

The Madagascan endemic, Bryophyllum delagoense (Crassulaceae), is a major weed in Queensland, Australia. Despite having first been recorded in Australia in the 1940s, it is far more invasive there than on the African mainland where it was introduced more than 170 years ago. This may be due to a number of factors, one of which could be the occurrence of new natural enemy associations in southern Africa. Among the insects of crassulaceous plants that have extended their host ranges, a stem-boring weevil, Alcidodes sedi, was studied to elucidate its status as a natural enemy of B. delagoense in southern Africa and as a candidate biological control agent for introduction to Australia. Laboratory studies indicated that damage inflicted by adult and larval feeding caused significant reductions in stem length and number of leaves. Preliminary host-range trials revealed that A. sedi can complete its development on other species in the Crassulaceae, including most of the introduced Bryophyllum species and some Kalanchoe species native to South Africa. Despite the oligophagous nature of A. sedi and the fact that it can complete its development on a number of ornamental species in the Crassulaceae, it should be considered a potential biological control agent in Australia. All of the native Crassulaceae in Australia are in the genus Crassula, most of which are very small and therefore unlikely to support the development of a large weevil like A. sedi. However, additional host-range trials will have to be undertaken in Australia to determine whether the weevil can be considered safe for release.     

Quarantine host range of Bikasha collaris,a potential biological control agent of Chinese tallowtree (Triadica sebifera) in North America

Chinese tallowtree, Triadica sebifera (L.) Small (Euphorbiaceae), is one of the worst invasive weeds of the southeastern USA impacting coastal wetlands, forests, and natural areas. Traditional mechanical and chemical controls have been unable to limit the spread, and this invasive species continues to expand its range. A proposed biological control candidate, the flea beetle Bikasha collaris (Baly) (Coleoptera: Chrysomelidae), shows high specificity for the target weed Chinese tallowtree. Results from a series of no‐choice and choice feeding tests of B. collaris adults and larvae indicated that this flea beetle was highly specific to Chinese tallowtree. The larvae of B. collaris feed by tunneling in the roots, whereas the adults feed on the leaves of Chinese tallowtree. A total of 77 plant taxa, primarily from members of the tallow plant family Euphorbiaceae, were tested in numerous test designs. Larval no‐choice tests indicated that larvae completed development only on two of the non‐target taxa. Of 80 B. collaris larvae fed roots of Hippomane mancinella L. and 50 larvae fed roots of Ricinus communis L., two and three larvae completed development, respectively. The emerging adults of these five larvae died within 3 days without reproducing. Larval choice tests also indicated little use of these non‐target taxa. Adult no‐choice tests indicated little leaf damage by B. collaris on the non‐targets except for Ditrysinia fruticosa (Bartram) Govaerts & Frodin and Gymnanthes lucida Sw. When given a choice, however, B. collaris adults consumed much less of the non‐targets D. fruticosa (7.4%) and G. lucida (6.1%) compared with the control leaves. Finally, no‐choice oviposition tests indicated that no eggs were produced when adults were fed all non‐target taxa, except those fed G. lucida. These B. collaris adults fed G. lucida leaves produced an average of 4.6 eggs compared with 115.0 eggs per female when fed Chinese tallowtree. The eggs produced from adults fed G. lucida were either inviable or the emerging larvae died within 1 day. These results indicate that the flea beetle B. collaris was unable to complete its life cycle on any of the non‐target taxa tested. If approved for field release, B. collaris will be the first biological control agent deployed against Chinese tallowtree in the USA. This flea beetle may play an important role in suppressing Chinese tallowtree and contribute to the integrated control of this invasive weed.     

摄食水平对不同性别食蚊鱼仔幼鱼生长发育的影响

在实验室27℃水温下,研究了少食、中食和饱食三个摄食水平对0至25日龄雌雄食蚊鱼(Gambusia affinis)的生长发育特征和饵料利用效率的影响。26d饲养实验结束后,对试验鱼摄食和生长指标、臀鳍分化、性成熟及饵料转换效率进行分析。结果显示:到臀鳍开始分化时,饱食组雄鱼的累计摄食总能量和生长速度开始小于雌鱼,且随日龄的增加差异加大;随摄食水平的增加,0日龄仔鱼到臀鳍分化和性成熟的时间缩短。至实验结束,各摄食组的雄鱼均形成发育完善的生殖足,性腺都达到成熟状态;而雌鱼性成熟迟于雄鱼,且其性成熟更易受到摄食水平的影响,饱食组只有约50%的个体达到性成熟,少食组的卵母细胞则均处在小生长期。随着摄食水平的增加,雌雄鱼的体长、体重和干物质特定生长率均呈明显上升趋势,而干物质饵料转化效率则呈明显下降趋势;实验结束时,雌鱼的生长指标和干物质饵料转化率均大于雄鱼。以上结果表明,伴随臀鳍的分化,食蚊鱼在摄食、生长、发育、性成熟和应对食物丰度变化上表现出显著的性别差异。