Introduction. Ricinodendron heudelotii Baill. est une essence forestière en voie de domestication au Cameroun où la plante est appréciée pour ses vertus alimentaires, écologiques et médicinales. Les dégâts causés par le psylle Diclidophlebia xuani Messi et al. aux jeunes plants, en pépinière ou après leur plantation, constituent l’une des principales contraintes à la domestication de l’espèce. La biologie de ce ravageur a donc été étudiée afin d’envisager son contrôle. Matériel et méthodes. Différents aspects de la biologie de D. xuani ont été abordés : processus d’accouplement, choix du site de ponte par la femelle, maturation sexuelle des imagos, fécondité des femelles, longévité des imagos, développement embryonnaire et larvaire, sex-ratio à l’émergence et spécificité alimentaire. Les expérimentations ont eu lieu dans la région de Yaoundé soit en champ, soit en milieu contrôlé durant les années 2001 et 2002. Résultats et discussion. Les mâles de D. xuani ont émergé avant les femelles et le rapprochement des sexes a eu lieu 15 min environ après la mue imaginale. La longévité des femelles a été de 29 jours en moyenne, celle des mâles, de 7 jours. La ponte a commencé 3 jours après l’émergence et s’est poursuivie jusqu’à la fin de la vie de la femelle. En période chaude (28 °C environ), une femelle a pondu en moyenne 532 œufs pendant toute sa vie ; en période de basses températures (24 °C à 26 °C environ), la fécondité moyenne a été de 758 œufs. Les œufs sont essentiellement déposés sur les étages foliaires les plus jeunes de R. heudelotii. Les développements embryonnaire et larvaire ont duré respectivement 7 jours et 22 jours environ. Le cycle de développement, d’œuf à œuf, a nécessité 32 jours en moyenne. Le sex-ratio a été proche de 1. Conclusion. D. xuani se développe entièrement et sans interruption sur R. heudelotii ; il n’a jamais été rencontré sur d’autres espèces de plantes. Il serait donc étroitement associé à cette plante.

The biological hypothesis that female parasitoids can adjust their fecundity schedule according to host availability, and tradeoff longevity with fecundity was tested in a thelytokous oophagous parasitoid, Trichogramma brasiliensis Ashmead (Trichogrammatidae: Hymenoptera) parasitising the rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). The tradeoff between early and late reproduction revealed that this wasp was able to exploit practically all available hosts during the first day or first few days of adult life. During spells of host unavailability, it was able to adjust its fecundity schedule accordingly. There was a negative relationship between survival and reproduction. Adult females survived shorter (10 days) when an unlimited supply of hosts was present, but longer (16 days) when no hosts were provided. These observations suggest the potential suitability of T. brasiliensis for inundative releases even in conditions of fluctuating host availability.

The developmental, oviposition, and mortality rates for the polyphagous earwig Diaperasticus eryihrocephala Olivier feeding on pollen and Ephestia kuehniella Zeller eggs were measured at constant temperatures of 18, 25 and 32 °C. The developmental period for D. erythrocephala required 533 degree-days (DD) above a threshold of 6.7 °C. Egg and larval development rates increased with increasing temperature, with the shortest developmental period being recorded at 32 °C. However, egg and larval mortality and larval malformation rates were significantly higher at 32 than at 25 and 18 °C. Over a period of 60 days, females laid an average of 26.5 eggs at 25 °C and none at 18 °C. Based on the results obtained, it is concluded that of the three temperatures, 25 °C is the most suitable for the laboratory mass rearing of D. erythrocephala.

The developmental potential of the palm aphid Cerataphis palmae Ghesquière (Homoptera: Pemphigidae) on three dwarf coconut varieties—Malayan dwarf red (Mdr), Malayan dwarf green (Mdg) and Malayan dwarf yellow (Mdy)—was studied in a screenhouse using leaf clip-on cages. Under similar temperature (30°C ± 1.13) and relative humidity (69.8% ± 1.63) conditions, the aphid expressed significant differences in fecundity, longevity and developmental period on the coconut varieties. The total developmental period on Mdr lasted 12.17 ± 0.76 days while on Mdg and Mdy it was 14.84 ± 0.63 and 13.83 ± 1.05 days, respectively. Thus the aphid population increased on the dwarf red variety over a significantly shorter period than it did on the other two varieties. Furthermore, fecundity and longevity of C. palmae on Mdr were significantly higher than on the Mdg and Mdy varieties (P < 0.01). These results indicate that Mdr supports C. palmae development better than the other two palm varieties.

Growth, development and fecundity of Maruca vitrata Fabricius (Lepidoptera: Crambidae) were studied on artificial diet and flowers of two accessions each of three wild Vigna species, namely V. vexillata (TVnu 594 and TVnu 72), V. oblongifolia (TVnu 957 and TVnu 42) and V. unguiculata ssp. dekindtiana (TVnu 979 and TVnu 863) and six accessions of cowpea, V. unguiculata ssp. unguiculata (Moussa Local, VICAM-1, TVu 13731, IT84S-2246, IT89KD-457 and IT91K-180). The percentage survival of the larvae, larval weights as well as growth and development indices were significantly higher on the artificial diet, flowers of cowpea cultivars and those of V. unguiculata ssp. dekindtiana compared to those of V. vexillata and V. oblongifolia. The fecundity of females from larvae reared on artificial diet and flowers of cowpea was also significantly higher than that of females from the wild Vigna genotypes. All variables were included in principal component analysis. Two components accounted for 81.79%. On the basis of this analysis, the diets appeared to fall into four categories based on their suitability for supporting development of M. vitrata: unsuitable (TVnu 42 and TVnu 957), fairly suitable (TVnu 72, TVnu 594, TVnu 979, Moussa Local and TVnu 863), suitable (IT89KD-457, IT91K-180, VICAM-1, TVu 13731 and IT84S-2246), and very suitable (artificial diet). The importance of these findings in the development of host plant resistance of cowpea to M. vitrata is discussed.

The biology of the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), on four legumes (faba bean, field pea, lentil and grass pea) was studied in a greenhouse during the 1999/2000 seasons. There was no significant difference in length of nymphal period and number of moults (instars) among the crop species tested. The aphids generally took 9 to 11 days to reach the adult stage with a maximum of 3 moults. Lifespan was significantly longer on lentils than on other crops. Significantly more aphids survived beyond 15 days on lentil than on other crops. Similarly, the reproductive and post-reproductive period and adult longevity were longer on lentil. The pre-reproductive period was significantly higher on field pea than on the other crops. The net reproductive rate (R0) was highest on lentil (103.56 females /female) arid the intrinsic rate of increase (r) was highest on faba bean due to a short generation time (14.27 days). Generally, lifetime fecundity was higher on lentil (115.10/female) due to a higher daily reproduction rate (6.7 nymphs/female/day) on this crop. Nymphal production per aphid was strongly and positively correlated with lifespan, reproductive period and adult longevity but not of the nymphal period. Daily nymph production was significantly correlated with minimum temperature on lentil alone (F = 4.61, P < 0.05). Knowledge of the crop species and varieties susceptible to pea aphid is useful for identifying diets for the mass rearing of aphids for use in resistant variety selection and as diet for artificial natural enemy production. The present experiment indicates that lentil is suitable for both purposes.

The leaf miner Coelaenomenodera lameensis Berti and Mariau (Coleoptera: Chrysomeiidae, Hispinae) is the main oil palm pest in Africa. A study of variations in its fecundity, in space and time, was carried out at 7 plantations and 19 sites in Côte d'lvoire. Fluctuations in fecundity, which could vary from almost 300 eggs to just a few eggs per 90-day period, were very similar at the various sites of the same plantation, and at the sites of different plantations, even when these were very far apart from each other. Fecundity increased with temperature, but other climatic factors were also important, with air saturation deficit playing a decisive role. The drier the air, the lower was the fecundity, which could even reach almost zero. As this parameter had a considerable impact on palm leaves' stomatal opening, a highly significant correlation was established between the latter and fecundity. Food supplies for larvae and adults can also affect fecundity, which seems to vary with the potassium content of the leaves.

Des paramètres de la reproduction d'une population isolée du tilapia Sarotherodon melanotheron ont été étudiés durant 2 années consécutives et comparés avec les données de la littérature obtenues sur des populations vivant dans son milieu naturel. Le sexe-ratio (année 1 : 1:2,69; année 2 : 1:1,96) en faveur des femelles varie de façon saisonnière. Les mâles atteignent la maturitésexuelle plus rapidement (année 1 : 129 mm LS ; année 2 : 126 mm LS) queles femelles (année 1 : 135 mm ; année 2 : 136 mm LS). Le cycle dematuration des gonades est continu. Ces résultats sont dans l'ensemblesemblables à ceux obtenus dans le milieu naturel de l'espèce. Cependant,une fécondité inférieure et un diamètre ovocytaire plus grandsont notés dans le lac d'Ayamé. Le facteur de condition moyen despopulations du lac, intermédiaire entre des valeurs observées dans lesmilieux lagunaires, indique une bonne adaptation de l'espèce aux conditionsd'eau douce du lac.

Diet change in the cotton stainers, Dysdercus cardinalis and D.fasciatus, occasioned by their migration from Gossypium hirsutum (cotton) to alternate hosts Sterculia rhynchocarpa and Adansonia digitata, was overall beneficial to their bionomics. Only the host Abutilon mauritianum appeared to possess antibiotic effects against the fecundity, fertility and longevity of the stainers. The occurrence in tropical natural ecosystems of both suitable and unsuitable hosts appears to constitute a vital and a viable stainer population-regulatory mechanism. Overall, D. cardinalis exhibited superior reproductive parameters on a variety of diets than did D. fasciatus. The latter apparently suffered profound negative effects on its bionomics when feeding on certain hosts.

L'inversion hormonale du sexe chez Oreochromis aureus (génotype mâle ZZ et génotype femelle ZW) avec un œstrogène (1717α-éthynylœstradiol) conduit à l'obtention de pseudofemelles, caractérisées par un genotype mâle (ZZ). Le croisement de ces pseudofemelles avec des mâles (ZZ) donne, en théorie, des populations 100 % mâles. Nous avons déterminé et comparé les principaux paramètres caractéristiques de la reproduction au sein de trois groupes de géniteurs O. aureus. Le premier groupe (groupe 1) est composé de femelles, le second (groupe 2) de pseudofemelles et le troisième (groupe 3) de femelles et de pseudofemelles. La fécondité et le poids des œufs des femelles et des pseudofemelles ne sont pas significativement différents. Dans le groupe 3, le taux de reproduction des pseudofemelles (0,6 pontes) est plus faible que celui des femelles (6,4 pontes). Dans ce groupe 60 % des pseudo-femelles ne se sont jamais reproduites. Dans les groupes 1 et 2, il n'existe pas de différence entre les femelles (6,9 pontes) et les pseudofemelles (4,7 pontes). Le plus faible taux de reproduction des pseudofemelles pourrait résulter de l'expression du génotype sexuel mâle chez ces individus.

The life cycle of a brackish-water population of Palaemonetes argentinus, a normally freshwater shrimp from the warm temperateregion of eastern South America, was studied in Mar Chiquita coastal lagoon, Argentina. In 1995, recruitment took placein January, followed by two growth periods, the first at the beginning of summer and the second from the end of winter throughmost of spring. Females reached a larger size than males. Ovigerous females, probably belonging to two cohorts, were foundfrom October 1995 to February 1996, with a maximum number in November (93 %). Their average size and fecundity varied duringthe breeding period. The sex ratio did not significantly differ from 1:1 except in November. Evidence of mature oocytes inthe ovaries was found in ovigerous and postovigerous shrimps, suggesting that they breed twice a year. However, only some femalesof the first cohort produced a second hatch in 1995. The maximum number of undifferentiated embryos carried by a femalewas 250; there was a positive relationship between fecundity and size. Larvae were collected together with adults from Novemberto March. The life history is similar to that described in several freshwater populations. Differences are restricted to chronologicalaspects such as a shorter unimodal breeding period and are probably related to climatic factors, since Mar Chiquita is nearthe southern limit of the geographic range of the species. Data presented here suggest interannual variations in reproductive patternsthat lead, sometimes, to a longer bimodal breeding period.

The paper explores the apparent contradiction between a high trawling pressure on juveniles and sustained production of hake that has occurred over the last decade in many Mediterranean fisheries. The practical consequences are followed of assuming rapid declines in natural mortality rate M in the first few years of life to a low, constant adult natural mortality, as well as the observation, for small-mesh trawl cod ends, of declining availability with age. Several approaches are proposed for fitting declining M-with-age with a reciprocal function for hake, using criteria based on mean life-time fecundity, mean age at egg production, existing estimates of adult M, and vectors based on stock productivity assumptions. All vectors of M-at-age were similar to MSVPA estimates of North Sea stocks.

The implications of the changes in mortality with age for stocks harvested by fine-mesh trawls wereexplored in yield per recruit calculations under 2 different hypotheses: 1) using current estimates of growth and adult mortality, 2) M-at-age vectors for juveniles, dropping rapidly from age 0+, and declining availability to trawling for older fish. These hypotheses were compared within yield per recruit analyses. Under the new assumptions, given current F>>M (adults), yield isopleths predict no significant increases in Y/R with stretched mesh > 40 mm, but a substantial decline in fecundity per recruit with small increases in effort by gill nets or longlines, aimed at mature fish. These results are linked to the refugium concept for older fish, and it is speculated that this may be in part responsible for the continued productivity of other sustained fisheries for juvenile resources elsewhere.

L'examen macroscopique, histologique et cytologique des ovaires de Barbus holotaenia adultes récoltés dans le bassin de la Luki entre juillet 1986 et septembre 1988 a permis de décrire six stades de développement des ovaires et sept stades au niveau des ovocytes et des follicules. Quelques conclusions biologiques et écologiques sont tirées de ces différentes observations. La fécondité individuelle partielle est comprise entre 0,005 et 0,018 ovocytes par kg de la masse du poisson.

In captive Heterobranchus 1ongifilis females, oocytes maturation and ovulation are induced by a single injection of human chorionic gonadotropin (hCG) at a dose of 1.5 I.U./g body weight. In the present study, three experiments were performed in order to specify the timing of ovulation and the effects of varying latency period on the quantity and quality of the collected ova. The ova quality was estimated by hatching percentage and proportion of deformed larvae obtained after artificial fertilization. The results showed that, in an individual female, ovulation of postvitellogenic oocytes is not synchronous and takes 3 to 4 hours to be completed, between 7–8 h and 11 h after hCG injection at 30 °C. The quantity of ova that could be collected by handstripping increased with the latency period, from 18,000 ± 12,000 to 72,000 ± 29,000 ova per female at 8 h and 11 h after injection, respectively. However, the first ova obtained (8 h after injection) were of good quality (94% hatching) and showed no signs of incomplete final maturation. Eleven hours after injection, the percentages of ovulated oocytes within the whole ovarian population of postvitellogenic oocytes were high in all the females, being generally around 90%. After ovulation, aging of ova occurred rapidly: the proportion of deformed larvae increased significantly (from 4 to 20%) 2 h after completion of ovulation and, 4 h post-ovulation, hatching percentage dropped from 92 to 36%. In H. longifilis, the optimal latency period can be defined as the time, from injection to stripping, allowing the best compromise between quantity and quality of ova released. This latency period was found to be 11 h following hCG injection at 30 °C, and corresponds approximately to the completion of ovulation.

The development of Helicoverpa (= Heliothis) armigera (Hb.) (Lepidoptera: Noctuidae) on foliage, squares and bolls of four cotton cultivare [G 27, HD 167 (Gossypium arboreum), H 777 and H 974 (G. hirsutum)] and one hybrid (HHH 81) was studied under controlled conditions. The results indicated that some biological parameters were influenced only by plant parts and not by cultivar/hybrid. The larvae died as first instars when reared on the foliage of cv. G 27 and HD 167. Irrespective of cultivar, the larvae and pupae weighed more when the larvae were reared on cotton bolls than on squares and foliage. The larval and pupal periods were shortest for larvae reared on bolls, followed by squares and foliage. The fecundity of the female was highest when the insect was reared on bolls, followed by foliage and squares. The longevity of the female moth was highest in insects reared on bolls, followed by insects reared on squares, and on foliage. The longevity of the male moth was not influenced by rearing on the different plant parts. The duration of the life cycle was shortest for insects reared on bolls, followed by squares and foliage.

This work examines the effects of constant long and short days on the hormonal profile of plasma17β-oestradiol (E2) levels and the ovarian vitellogenic events, as well as on the fecundity, time of spawning and egg quality of sea bass. Constant short days first administered in April advanced spawning (by 45 days on average) whereas exposure to constant long days from the same date induced a delay (averaging 38 days) compared to controls reared on an ambient light regime (Lat. 40°N). These light regimes produced shifts in the profiles of plasma 17β-oestradiol and in the percentage of the vitellogenic oocytes according to the spawning time of the respective groups. Relative fecundity of the short day group was similar to controls (257,000 versus 230,000 eggs/kg spawned female, respectively). However, in the long day group, relative fecundity was reduced to one half that of control fish (124,000). Plasma oestradiol showed a bimodal pattern under long days and vitellogenetic and atretic oocytes were present for a longer period (6-7 months compared to 4-5 months in controls). In summary, in this paper we describe, for the first time in the sea bass, the effect of constant photoperiod regimes on the 17β-oestradiol plasma profiles, the timing of spawning and the quality of the eggs.

La fécondité par acte de ponte du listao Katsuwonus pelamis de l'ouest de l'océan Indien a été étudiée à partir de 281 femelles dont les tailles (longueur à la fourche) sont comprises entre 43 et 73 cm et dont les ovaires étaient à un stade de maturité sexuelle avancé. Le liquide de Gilson, utilisé comme agent conservateur et dissociateur des ovocytes, a une action importante et rapide (5 jours) sur le rétrécissement des ovocytes. Des comptages effectués à l'aide d'une cuve de Dollfus sur des sous-échantillons d'ovocytes dissociés, montrent que pour une même période d'activité sexuelle (février), la fécondité du listao du canal de Mozambique est semblable à celle des listaos du sud du plateau des Seychelles. Bien qu'une activité sexuelle du listao soit notée tout au long de l'année, la fécondité individuelle varie d'une saison à l'autre et ce, pour un même secteur géographique. Cette fécondité individuelle par acte de ponte varie de 80 000 œufs pour des femelles de 44 cm provenant de la côte nord-ouest de Madagascar à 1,25 millions d'œufs pour des femelles de 75 cm pêchées autour des Seychelles. La fécondité relative correspondante évolue donc entre 40 et 130 œufs/g de poids de corps. Pour cette espèce, le nombre de pontes successives a été estimé à 4 par an.

Adult two-year-old broodstock sea bass (Dicentrarchus labrax), raised in captivity, were fed ad libitum a natural diet (trash fish) until the end of their first spawning, and maintained under natural conditions of light and temperature. Six months before the second spawning, fish were randomly separated in two tanks with running sea water (salinity 37.80‰, pH 8.3) and maintained under similar environmental conditions. Fish were fed two different ration levels: group F, 1.04%, and group H, 0.45% body weight/day. The Jow ration supplied affected broodstock growth as indicated by decreased growth rates in weight and condition factor in group H, when compared to group F. The mean fecundity per female (No. eggs/female) in group H fish was similar to that from F group, while the relative fecundity (No. eggs/kg female) was more elevated in the H group. However, group H showed a delay in spawning time and slightly higher number of spawnings per female and larger spawning period, when compared to group F fish. In addition, group H females had reduced 17β-estradiol (E2) plasma levels and presented vitellogenic oocytes in the ovary a month later than group F females. By contrast, the vitellogenin (VGT) plasma levels remained similar between groups over the reproductive cycle. The egg quality (i.e. percentage of buoyant eggs), the egg biochemical composition and larval survival at hatching were similar between the two groups. The larvae from both groups also exhibited the same survival after 40 days of culture, although group H produced smaller eggs that yielded smaller newly-hatched larvae. Although the low ration supplied significantly reduced the growth and E2 plasma levels of sea bass, these preliminary results suggest that these changes do not dramatically affect the egg viability or the survival of larvae 46 days after hatching.

L'élevage de groupes d'atipas, Hoplosternum littorale (Hancock, 1828). en bassins de pisciculture, ou de couples isolés en viviers, a montré que, dans ces conditions, la chronologie de la reproduction de l'espèce, établie par le dénombrement des nids et des pontes, reste comparable à celle observée dans le milieu naturel et s'étend de début novembre à fin mai. L'élevage de couples isolés a montré une régression du poids de la ponte en fonction de son numéro d'ordre. Chez les femelles d'un poids moyen de 207 g, ce poids diminue de la première (66,7 g) à la troisième ponte pour se stabiliser à 21,9 g. Chez les femelles d'un poids moyen de 89 g se reproduisant pour la première fois, cette diminution est de moindre amplitude. De 28,5 g pour la première ponte, la masse d'œufs pondue se stabilise à 23,9 g à partir de la troisième ponte. Le nombre de pontes au cours d'un cycle annuel peut s'élever à 14 et la production annuelle d'œufs peut atteindre 180 g, soit 48 600 œufs, pour une femelle de 89 g, ou 340 g, soit 91 900 œufs, pour une femelle de 207 g. Ces nombres d'œufs ont été évalués sur la base d'un poids unitaire de 3,7 mg, poids moyen déduit de la pesée et du dénombrement de 55 pontes. Au cours d'une saison de reproduction, les femelles de 207 g accusent en moyenne un déclin du poids corporel de 23 %. Chez les mâles d'un poids moyen de 292 g, cette perte de poids, plus modeste, atteint 9 % du poids initial. Chez des sujets se reproduisant pour la première fois, cette perte de poids est de 10 % pour les femelles de 89 g et de 0,4 % pour les mâles de 185 g. Les observations menées sur des groupes de sujets élevés collectivement en bassin ont montré que 49 °C des nids contenant des œufs abriteraient la ponte de 2 femelles ou plus et que 5 femelles peuvent pondre simultanément dans un même nid. Dans la pisciculture, 48 % des nids observés ne contenaient pas de ponte et les périodes où le taux de nid vide est le plus important encadrent la période correspondant à l'activité maximale de reproduction (janvier-février). Par ailleurs, le taux de nid vide n'est pas corrélé à l'importance des pluies. Le prélèvement d'alevins opéré à un moment tardif du cycle de reproduction serait susceptible de relancer l'activité de ponte mais n'engendrerait pas d'augmentation significative de la durée de la période de reproduction. De même, la mise en présence tardive des géniteurs ne semble pas générer d'allongement de la période de reproduction. La conclusion porte sur l'intégration de ces divers résultats à une vision globale de la stratégie de reproduction de l'espèce.

The length of the reproduction cycle of Lasioderma serricorne (F.) under ambient laboratory conditions (temperature range 28.0–32°C and 72.5–80.5% r.h.)was shown to depend on the identity and state of division of various cereal grains, cowpeas, groundnuts and dried root crops. Cut dried yams allowed the shortest cycle andwholericethelongest.The rate of population increase by L. serricorne was also assessed and this was maximal when cut wheat and minimal when whole rice was provided. Fecundity was highest with sorghum and lowest with rice as food source. Females of the species lived longer than males.