The effect of the impoundment of Lake Kainji, Nigeria, on the indigenous species of mormyrid fishes

SUMMARY. Changes in the numbers and species composition of mormyrid fishes since the impoundment of the Niger (Lake Kainji) are analysed. An initial decline after impoundment appears to have been reversed and these fish are now increasing. The increase is, however, restricted to a few species only; many forms common in the river are still declining or have disappeared altogether. Marked seasonal variations in abundance are described and possible explanations discussed.     

The reproductive biology of Pellonula afzeliusi Johnels,and Sierrathrissa leonensis thys Audenaerde in Lake Kainji,Nigeria

Aspects of the reproductive biology of the two species of clupeids known to occur in Lake Kainji, Pellonula afzeliusi Johnels and Sierrathrissa leonensis Thys Van Den Audenaerde were studied for a period of twenty eight months. Mature individuals were found in both species all the year round but with a prolonged peak of activity from December to May, more distinct in P. afzeliusi than in S. leonensis.There were no significant length differences between mature males and females in both species. The smallest mature individuals were 28 mm standard length female; 27 mm standard length male in P. afzeliusi, while the corresponding figures for S. leonensis were 18 mm standard length female and 19 mm standard length male.No sexual dimorphism was observed. There was a simple correlation between fecundity and fish standard body length as well as weight in both species.     

On a new species of electric catfish from Kainji, Nigeria, with some observations on its biology

A new species of electric catfish, Malapterurus minjiriya , from Kainji, Nigeria, is described and a key for separating it from the two other known species is given. Notes on some aspects of the biology of the electric catfishes in Lake Kainji, Nigeria are included.     

Food and feeding of the mormyrid fishes of Lake Kainji, Nigeria, with special reference to seasonal variation and interspecific differences

The feeding habits of mormyrids from Lake Kainji, Nigeria, are discussed in relation to the decreased abundance of these fish since impoundment in 1968. Evidence is presented of both intra-specific seasonal variation in diet and inter-specific trophic divergence. These variable factors are discussed in relation to the degree of success achieved by certain species in the lake.     

中国四种扇野螟属幼虫形态记述及生物学习性（鳞翅目：草螟科：斑野螟亚科）

记述中国扇野螟属三条扇野螟Pleuroptya chlorophanta、枇杷扇野螟P.balteata、四斑扇野螟P.quadrimaculalis、淡黄扇野螟P.sabinusalis等4种老熟幼虫的的形态特征且提供幼虫的形态特征图,并给出基于幼虫的生物学习性。     

Food and feeding of three Citharinus species in Lake Kainji, Nigeria

This paper provides information on the food and feeding habits of three Citharinus species in Lake Kainji. A total number of 2357 specimens made up of 1628 Citharinus citharus , 705 C. distichodoides and 24 C, latus were examined. The majority of the fish caught by gill-netting had empty stomachs unlike those caught by cast-netting and electrofishing. The main food items were planktonic and epipelic blue-green and green algae. All the three species had similar feeding habits and also fed on the same items; their food varied with the seasons. Citharinus spp. have high gut length/standard length ratios which are adaptations to the microphagous and planktivorous feeding habits.     

The food of adult copepods from Lake Kainji, Nigeria

SUMMARY. Gut contents of adult copepods from Lake Kainji were analysed. The calanoid copepod Tropodiaptomus banforanus was exclusively herbivorous with Melosira and Peridinium forming a large proportion of the diet. Of the cyclopoid copepods, Mesocyclops leuckarti was mainly carnivorous while the smaller Thermocyclops neglectus was mainly herbivorous. Experiments with Diplocystis (Microcystis) showed that it was not ingested by these three copepod species even after starvation and possible explanations for the results are discussed.     

Floral biology and pollination mechanisms of four Mexico-endemic Fuchsia species with contrasting reproductive systems

Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of lineage diversification. Closely related hermaphroditic and dioecious species with biotic pollination provide the opportunity to study and compare traits related to pollinator attraction and their consequences on reproductive components. A higher predictability of pollination syndromes is expected in dioecious species, which are dependent on pollinators, than in self-compatible hermaphroditic taxa. Dioecious species may suffer pollen limitation depending on the quality of floral rewards and the kind and abundance of pollinators, whereas no pollen limitation is expected in hermaphroditic species with autonomous self-pollination. Additionally, in the absence of pollen limitation, more or better seeds are expected in dioecious species, according to the sexual specialization hypothesis.Methods In natural populations of the hermaphroditic Fuchsia fulgens and Fuchsia arborescens and dioecious Fuchsia parviflora and Fuchsia obconica, all endemic to Mexico, we first described flower phenology, flower production and longevity and nectar volume and concentration. Then, we evaluated the correspondence between floral visitors and pollination syndromes. In hermaphrodite plants, we determined the level of herkogamy and the potential for autonomous self-pollination. Finally, we evaluated the effect of pollen limitation on fruit set and seed number and assessed seed germination for all species.Important findings In contrast to our prediction, dioecious species did not show a higher correspondence between pollination syndromes and floral visitors than did hermaphrodites; however, male flowers exhibited a higher correspondence than female flowers. No pollen limitation was detected in dioecious species, for which visitation rate did not differ between male and female flowers. The hermaphroditic F. fulgens showed pollen limitation for seed number, despite the presence of autonomous selfing. Fruit set from autonomous pollination was higher in F. arborescens, which showed a lower level of herkogamy compared with F. fulgens. Finally, dioecious species produced fewer but heavier seeds compared with hermaphrodite species. Although Fuchsia is classified as an outcrossing genus, both hermaphroditic species showed autonomous self-pollination. The heavier but lower number of seeds per fruit in dioecious species may be related to the more efficient resource allocation expected from sexual specialization. This could play an important role in the evolution of dioecy; however, a comparative phylogenetic approach is required to confirm this hypothesis.     

A new genus and species of cypridid ostracod from India, with notes on its biology

A new Recent cypridid ostracod genus Bharatcypris , belonging to the subfamily Cypridinae, with Bharatcypris mackenziei sp. nov. as type-species is described from the Punjab, India. Some observations on its biology are also recorded. Two Indian species previously placed in Sclerocypris are transferred to the new genus.     

Aspects of reproductive biology of Labeo horie Heckel (Pisces: Cyprinidae) in Lake Chamo, Ethiopia

Labeo horie Heckel is increasingly becoming commercially important in Lake Chamo but its reproductive biology in the lake is not well enough to guide its management. Sex ratio, breeding season, length at first maturity and fecundity of L. horie were studied from 1197 fish samples collected between August 1998 and October 1999 in Lake Chamo, Ethiopia. The sex ratio was significantly different (χ ² = 12.12, P < 0.001). The peak‐breeding period was during the rainy months of March to May, during which time more than 90% of both sexes had ripe gonads. The size at maturity ( L _m50 ) of males was 52 cm while the L _m50 of females was 62 cm. The smallest ripe male in the catch was 46.7 cm and weighed 890 g while the smallest ripe female caught was 49.5 cm and weighed 1145 g. The weight of ripe ovaries ranged from 54.3 g to 991.8 g and contained between 68,400 and 1,320,400 eggs. Relative fecundity ranged between 60 and 290 eggs per g of body weight. The relationships between fecundity and total length and between fecundity and total weight were curvilinear, while the relationship between fecundity and ovary weight was linear. L. horie conformed to the general pattern of reproduction in a tropical environment where peak‐breeding activity occurred during the rainy season. In order to protect the spawning population, fishing pressure should be minimized during breeding time at the shallower littoral regions.     

The genus Xenoclarias (Pisces, Siluriformes) in Lake Victoria, with a redescription of Xenoclarias eupogon and notes on the biology of the species

The acquisition of large collections of the catfish Xenoclarias Greenwood from Lake Victoria, East Africa, demonstrated a need for a reappraisal of the taxonomy of the genus. It is suggested that only one species, Xenoclarias eupogon (Norman) is found in the lake but that it is very variable in many of its morphometric characters. The species is redescribed from data obtained for 72 fishes from various localities and depths in the lake. Observations of the food of the fish show it to be almost entirely insectivorous with a preference for Chironomidae over Chaoboridae larvae. Evidence is also put forward to support the view that X. eupogon breeds on or close to rocky shores.     

Toxic soles,Pardachirus marmoratus from the Red Sea and P. pavoninus from Japan,with notes on other species

Synopsis Fishes of the genus Pardachirus (Soleidae) are reviewed. Four species are recognized and their distribution mapped: P. marmoratus (Lacépède) from the Red Sea and Indian Ocean, P. pavoninus (Lapédè) and P. poropterus (Bleeker) from the Indo-Pacific, and P. hedleyi (Ogilby) from estuarine waters of Australia. Achirus rautheri Chabanaud is placed in synonymy with P. hedleyi. The ichthyocrinotoxic effect on teleosts of the secretion from P. pavoninus is described and compared with that of P. marmoratus. The distribution of poison glands in these two species shows more glands present on the eyed side. The number of glands range from 212 to 235 in P. marmoratus and 204 to 237 in P. pavoninus and number of rays on fins associated with the poison glands are about the same for both species. P. marmoratus appears to be more toxic than P. pavoninus.     

Observations on the biology of nymphs of Povilla Adusta Navas (Ephemeroptera: Polymitarchidae) in Lake Kainji,Nigeria

Observations onPovilla adusta Navas nymphs in Lake Kainji revealed that seasonal fluctuations in abundance were due to a shortage of food during the period of rising lake level rather than a depletion of oxygen in the water column; this shortage was caused by the increased turbidity of the flood waters restricting the growth of both planktonic and periphytic algae. Planktonic algae apparently formed the diet of nymphs <4–6 mm and also of larger nymphs if their preferred diet of periphytic algae was in short supply. Both depth distribution and individual size of the nymphs were closely related to the distribution of periphytic algae. Depth distribution patterns of the nymphs revealed a peak between 2–4 m below the surface.The dimensions of the nymphs and the duration of the aquatic stages (3–4 months) in Lake Kainji correspond closely with results obtained elsewhere as does the mean percentage of males in the population (28%±10%). Seasonal fluctuations in the sex ratio were apparently caused by variations in the intensity of predation.Department of Zoology, University of Reading     

Aspects of the reproductive ecology of four australian Hakea species (Proteaceae) in South Africa

Summary Four shrub species of the Australian Proteaceae (Hakea sericea, H. gibbosa, H. suaveolens and H. salicifolia) were introduced to South African fynbos shrublands between 1840 and 1860. H. sericea is highly invasive, H. gibbosa and H. suaveolens are moderately invasive and H. salicifolia is not invasive. The allocation of reproductive energy, germinability, the ability to survive fires and to germinate in burnt and unburnt areas, and the nutrient content of seeds were assessed for the four species. The information was used to investigate whether the success of H. sericea relative to the other three species could be explained by the superior expression of any trait. The most important trait which separates H. sericea from the other species is its ability to produce a large seed bank in its adopted environment in the absence of seed predators. Seed production in H. sericea shrubs with an above-ground dry mass of 8 kg is four times greater than H. gibbosa and more than 16 times that of H. suaveolens. Although H. salicifolia also produces a large seed bank, its seeds are unable to survive fires due to inadequate insulation by the small follicles. The results are compared to dispersal and seed bank data for indigenous South African Proteaceae, which have low dispersal and suffer high pre-dispersal seed predation. We suggest that potential invasives in the fynbos can be identified as species that have: (i) a potentially high seed production that is limited by specialized predators; (ii) an ability to disperse over long distances; and (iii) are pre-adapted to frequent fires and low soil nutrients. The data also support the current strategy of combatting H. sericea using specialized insect seed predators.     

Aspects of the reproductive biology of three species of Ectobius (Dictyoptera: Blattidae)

Ootheca production is here investigated in three species of field-dwelling cockroaches under both field and controlled conditions. Mating is shown to have a significant effect on the length of the pre-oviposition and inter-oviposition periods, fecundity, female longevity and the formation of the ootheca. The occurrence of facultative parthenogenesis is confirmed in Ectobius lapponicus and E. pallidus.

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Résumé Les effets de l'accouplement sur certains aspects de la biologie de la reproduction ont été étudiés, pour trois espèces de blattes champêtres du genre Ectobius, à la fois en conditions expérimentales et en conditions naturelles. E. lapponicus et E. pallidus se révèlent être des parthénogénétiques facultatives, bien que ce mode de reproduction entraîne une réduction de la fertilité de ces espèces. Cette parthénogenèse est thélytoque. Quelques ufs non fécondés de E. panzeri se développent partiellement, mais n'éclosent pas. Des différences dans certains aspects de l'oviposition apparaissent chez les 3 espèces entre les femelles vierges et les femelles accouplées. Les périodes de pré-oviposition et d'inter-oviposition sont allongées chez les femelles vierges. La forme des oothèques varie, celles déposées par les femelles accouplées sont plus courtes et plus larges. Des différences spécifiques sont manifestes dans le mode de dépôt et dans le sens de rotation de l'oothèque, ce dernier caractère étant aussi affecté de quelque façon par la copulation. La longévité des femelles vierges est plus grande que celles des femelles accouplées, bien qu'un moindre nombre d'oothèques soit déposé. En général les femelles des trois espèces se comportent de façon semblable dans les conditions expérimentales et en milieu naturel.

     

Age and growth of Neotrygon picta, Neotrygon annotata and Neotrygon kuhlii from north-east Australia, with notes on their reproductive biology

Vertebral band formations were used to define age and growth in three Neotrygon species caught regularly as by-catch in prawn trawl fisheries in north-east Australia. Centrum edge and marginal increment ratio analyses were used to validate annual band formations. Age estimates ranged from 1 to 18 years, with the von Bertalanffy growth function considered to have the best fit to Neotrygon picta (males, W(D∞) = 271 mm, k = 0·12; females, W(D∞) = 360·5 mm, k = 0·08) and Neotrygon kuhlii (males, W(D∞) = 438·6 mm, k = 0·08; females, W(D∞) = 440·6 mm, k = 0·08) disc width (W(D))-at-age data. The Gompertz growth function had the best fit to Neotrygon annotata W(D)-at-age data (males, W(D∞) = 230·4 mm, k = 0·20; females, W(D∞) = 265·5 mm, k = 0·31). Age at sexual maturity ranged from 3 to 6 years, with N. picta having the smallest size at birth (100 mm W(D)), smallest W(D) at 50% maturity (W(D50): male, 172 mm, female, 180·7 mm) and lowest age at sexual maturity (3-4 years). This study helps redefine and improve the accuracy of fisheries-based risk assessments for these small species with relatively conservative life-history variables.     

Aspects of the reproductive biology of Gonostoma bathyphilum (Gonostomatidae)

Protandrous hermaphroditism among deep-sea fishes is known only within one family, Gonostomatidae, and therein restricted to a few species of two genera, Cyclothone (C. atraria, C. microdon) and Gonostoma (G. elongatum, G. gracile). Gonostoma bathyphilum, the deepest dwelling (700–2700 m depth) of Gonostoma spp., is also protandrous and shares with Cyclothone spp. an expression of sexual dimorphism manifested by the excessive development of olfactory structures, including the olfactory lobes, in ripe males. Sex-reversal in ripe males, therefore, involves a regression of these structures. The relationships apparent between sex, maturity and olfactory development, and those between animal size, maturity and depth of occurrence, indicate that whilst protandry is an integral component of the species' reproductive strategy some individuals develop directly as females and that among males (max. size 150 mm S.L.) sex-reversal is not obligatory. Primary females, together with those derived from prematurely reversing males, may form an early maturing female group, spawning for the first time at about 110–120 mm S.L. Most hermaphrodites were < 100 mm S.L., and within the 70–99 mm S.L. size-range a significant proportion had mature male characters. Since males of this size were all found to be immature, this suggests that these hermaphrodites are derived from a precocious element within the initial male population, and, by virtue of size-stratification by depth, are responsible for mating with the early-maturing females. The lack of a marked seasonality in the sexual cycle implies an ever presence of all sexual categories within the population. It is conjectured that sex-reversal of ripe males is a response to critical population density levels of ripe females and that the smaller, precocious males would be more prone to sex-reversal than the larger, later-maturing ones. In some respects protandry in G. bathyphilum is similar to that in G. elongatum. In the latter, however, the reproductive cycle is seasonally linked and sex-reversal in males is probably obligatory. Even so, critical density levels of ripe females can still be invoked as being causal to sex-reversal.     

An unusual species of spoon-wing lacewing (Neuroptera: Nemopteridae) from South Africa, with notes on its biology

Abstract. An unusual species of spoon-wing lacewing, Palmipenna aeoleoptera sp.n., is described from Namaqualand, South Africa. This small species is similar to its three congeners in general body morphology and genitalic features. Its hindwings, however, differ dramatically from known insect hindwing form. These conspicuously pigmented wings with their relatively huge surface area are hypothesized to have dual aerodynamic and semaphore functions when used by males in gliding flight during mate attraction.     

A new species of hagfish of the genus Myxine, with notes on other eastern Atlantic myxinids

Myxine ios sp. nov. is a seven-gilled hagfish occurring on the continental slope in the eastern North Atlantic, off West Africa and southwest Ireland. The two populations overlap in morphometric and meristic character, but the Irish population is distinguished by having a white head and a whitish middorsal or midventral line. More material and collections from intermediate localities are needed before it can be determined if the two populations are distinct at the specific or subspecific level. The northern (Irish) population of M. ios is believed to occur in the same geographical range as M. glutinosa but to live at greater depths. Myxine ios is compared with M. glulinosa L. and M. capensis Regan, the other two eastern Atlantic Myxine species; new data are given for these species, both of which are regarded as valid.