Aspects of Reproductive Biology of the Scalloped Hammerhead Shark, Sphyrna Lewini, off Northeastern Brazil

Ninety four scalloped hammerhead sharks, Sphyrna lewini (53 females and 41 males) ranging in size from 121 to 321cm total length (TL), were collected from surface gillnetters operating off northeastern Brazil and throughout the southwestern equatorial Atlantic Ocean between January and December 1996. A common regression for TL and eviscerated weight (EW) was calculated as, logEW = –11.786 + 2.889 logTL. Females and males were categorised into reproductive stages (4 and 2, respectively) according to morphological changes in their gonads. Size at sexual maturity for females was estimated to be 240cm, while males appeared to mature at between 180 and 200cm. Gravid females had between 2 and 21 embryos or pups, varying in TL from 3 to 38cm. There was no relationship between maternal length and size of litter. Copulation and parturition appear to occur outside the sampled area and possibly closer to the coast. With the exception of slightly lower uterine and ovarian fecundities, the results support the few existing data on the reproductive cycle of S. lewini in other areas.     

Estimation of Standing Stock and Decomposition Rates of Labile Organic Matter in Waters of Novorossiisk Bay,Black Sea

The annual dynamics of the decomposition rate, standing stock, and residence time of labile organic matter as an index of full self-purification were investigated in Novorossiisk Bay, Black Sea. The results are suggestive of fairly effective processes of biological self-purification in polluted waters of the bay. The decomposition rate was highest (0.3–0.7 mgO₂/l per day) during the summer, and it decreased by 4–8 times in winter. The residence time of labile organic matter was 97–104 days in winter and 8–11 days in summer. Oxygen consumption rates measured in different areas of the bay conformed to their trophic status and were not above the normal level for summer.     

The Effects of Increasing UV-B Radiation on Pigmentation, Growth and Survival of Coregonid Embryos and Larvae

In the northern regions UV-B radiation levels have increased due to ozone depletion. A two-week laboratory experiment was conducted to measure the effects of UV-B radiation on the pigmentation, growth, oxygen consumption rate and survival of whitefish, Coregonus lavaretus, and vendace, Coregonus albula, larvae. In May newly hatched embryos were exposed in laboratory aquaria to three CIE weighted UV-B radiation levels: subambient (daily dose 1.37kJm^–2), 9% (1.81kJm^–2) and 34% higher (2.24kJm^–2) than ambient. Control embryos and larvae were not exposed to UV-B. Larvae of whitefish and vendace that were irradiated with highest UV-B level had 32% and 31% more melanin than control larvae, respectively, which we interpret as an apparent induced response. In controls, the species difference revealed 53% more melanin in vendace larvae than in whitefish larvae. UV-B radiation had no effect on the mortality of either species, the survival being high in all treatments (>90%). Additionally, neither growth rate nor the metabolic rate of larvae of either species was affected by UV-B radiation. Thus, in relation to future scenarios UV-B radiation may not be a threat to whitefish or vendace larvae in current or expected radiation levels.     

The Biology of the Nurse Shark,Ginglymostoma cirratum,Off the Florida East Coast and the Bahama Islands

The nurse shark is an extremely abundant shallow water species in Florida and the Caribbean, yet its biology is poorly known. Moreover, there is a great deal of misinformation about it in the literature. The maximum size and weight attained by the nurse shark have often been exaggerated. None of the specimens measured in this study exceeded 265cm TL and 114.5kg, and none of the specimens actually measured by other researchers exceeded 280cm. Females reach maturity at a length of 223–231cm, or at 86% of their maximum size. Males reach maturity between 214 and 214.6cm in length or at about 83% of their maximum size. Mating primarily occurs from mid-June to early July. The embryos are enclosed in sturdy egg capsules for the first 12–14 weeks of gestation. In a gravid female, the embryos are at different stages of development during the first four months of gestation. Embryos are lecithotrophic and there is no evidence of any supplemental mode of embryonic nourishment. Embryos measure 28–30.5cm at birth. The gestation period is estimated at about five to six months. Brood sizes are large, ranging from 21 to 50 young, with a median of 34 young. The reproductive cycle of the nurse shark consists of a five to six-month gestation period and a two-year ovarian cycle. Thus, the reproductive cycle is biennial and a female produces a brood every two years. The nurse shark is an opportunistic predator that consumes a wide range of small fishes, primarily grunts (Haemulidae).     

Activation of protease by sol-gel entrapment into organically modified hybrid silicates

To prepare an immobilized protease with a high activity for transesterification of vinyl n-butyrate with 3-methyl-1-butanol (isoamyl alcohol) in organic media, a protease was entrapped into organic–inorganic hybrid silica gel on Celite 545 by the sol-gel method. When propyltrimethoxysilane was used as the organic silane precursor mixed with tetramethoxysilane at a molar ratio of 16:1, the hybrid gel-entrapped protease on Celite 545 had 8 times the activity of the protease deposited on Celite 545 from 35 to 85°C.     

Biological productivity of Lake Towada,a north temperate,oligotrophic, kokanee fishery lake

During the Lake Towada survey from April through October 1998, we measured primary production at shore and offshore stations, and calculated crustacean zooplankton production from samples collected at the offshore station. We then analyzed these data and compared them with commercial fishery data in order to discuss the energy flow in this lake where kokanee (Oncorhynchus nerka) fisheries are one of the main businesses. At all stations, primary production was relatively high: 150–300mgCm^–2day^–1 in April–mid-June and lower at ca. 100mgCm^–2day^–1 thereafter. The variation in primary productivity could largely be explained by multiple regression models that included phytoplankton biomass and ambient nutrient conditions as independent variables. Among zooplankton, rotifers had their peak abundance in May, before the crustacean zooplankton (Daphnia longispina, Bosmina longirostris, and Acanthodiaptomus pacificus) population was well established. D. longispina dominated the crustacean zooplankton community in terms of biomass and production; their production during the study period made up 80% of crustacean community production (19.6gdry-wtm^–2), which was 40% of primary production during the survey. In July, when the abundance of D. longispina was particularly high, their daily production slightly exceeded daily primary production, which resulted in ca. 30% and 75% reduction in the amount of particulate organic carbon and chlorophyll a, respectively, during this period. The community ingestion rate of crustacean zooplankton, calculated from their daily production (D. longispina accounted for 90%) and the assumption that their gross production efficiency (K₁) was 60%, could roughly explain this reduction of particulate matter, corroborating previous studies that the grazing of D. longispina can significantly improve the water transparency of this lake. The catch of kokanee and pond smelt (Hypomesus transpacificus nipponensis, another important fish in the lake) during the survey corresponded to 1.1% of crustacean community production, and corresponded to 0.45% of the primary production, which is one of the highest recorded values. Bearing in mind that D. longispina was the major food item of planktivorous fish such as kokanee and pond smelt, the present study suggests that the energy transfer from phytoplankton to zooplankton to fish is outstandingly efficient, compared with other aquatic ecosystems, when D. longispina dominates in the lake.     

Ontogeny of the umbilical cord and placenta in the Atlantic sharpnose shark,Rhizoprionodon terraenovae

Synopsis The Atlantic sharpnose shark is a viviparous anamniote that develops an epitheliochorial yolksac placenta. Initially, contents of the yolksac nourish the embryos. Yolk is partially digested in the yolk syncytial-endoderm complex and subsequently transferred to the vitelline circulation. Yolk is also transported by ciliary activity of the yolk stalk ductus to the fetal gut for digestion. When embryos are 4.0cm in length, vascular ridges, termed appendiculae, develop on the yolk stalk. As yolk stores are depleted, the yolksac differentiates into the fetal portion of the placenta and the uterus abutting the yolksac differentiates into the maternal portion of the placenta. The yolk stalk differentiates into an elongate umbilical cord. The uterine epithelium produces secretions that are positive by the periodic acid-Schiff and alcian blue methods and metachromatic when stained with toluidine blue. Uterine capillaries are continuous and the surface epithelium is active both in secretion and transport of nutrients. When the embryos are 7–10cm in length, appendiculae are elongate, branched and populated by separate microvillar and granulated cells. Appendiculae may function as a paraplacental nutrient absorptive organ and be involved in the regulation of osmolarity of periembryonic fluids. The fetal placenta has two functional regions: a proximal portion that is presumed to function as a steroid producing organ and a distal portion that effects nutrient and metabolic exchange between the mother and fetus. Characteristics of the fetal placenta include endocytotic activity, crystalline-like cytoplasmic bodies and fenestrated capillaries. Fetal and maternal components of the placenta are separated by the egg envelope.     

Reproductive Ecology of Pterapogon kauderni, an Endemic Apogonid from Indonesia with Direct Development

Pterapogon kauderni does not have secondary sexual dimorphism, and has an equal sex ratio (50.8% males:49.2% females). Females first mature at a length of about 34mm. Data from both laboratory-bred and wild-collected eggs and embryos are not consistent with the presence of differential reproductive allocation in this species. Analysis from clutches brooded by wild-collected males shows a significant intra-clutch and among-clutch variation in egg size. Mean individual egg size (diameter, volume, or weight) is not correlated with the size (standard length, head length, or lower jaw length) of the males brooding those eggs. P. kauderni has a lunar reproductive cycle, with a major spawning peak during full moon and a smaller peak during the last quarter. Similarly, it has a major juvenile release (settlement) peak at full moon, with a minor peak at new moon. However, one population, which is located in a site with distinct environmental conditions and which was sampled a year earlier, shows a different reproductive pattern, last quarter being the phase where most of spawn and release events take place.     

Applying near-infrared reflectance spectroscopy to predict carbon,nitrogen, phosphorus,and organic-bound cadmium in lake picoplankton

This study describes the 0.1–3 m particle size fraction in a Precambrian Shield lake (37-ha Lake 382 in the Experimental Lakes Area, northwestern Ontario) receiving experimental additions of cadmium to determine fate and effects of low cadmium loading. This size fraction is important in binding cadmium in water. The study examined the feasibility of using near-infrared reflectance spectrophotometry (NIRS) for quantifying carbon, nitrogen, and phosphorus in this size fraction in 20-fold concentrated water samples from the lake and from a limnocorral experiment exploring the effect of fertilization on sedimentation of cadmium from the water column. NIRS was also used for detecting and characterizing organic matter in this size fraction associated with cadmium. Aliquots (1.5 ml) of the concentrated samples were applied to pre-ashed Whatman GF/C glass fibre filters. The filters containing 40–150 g carbon, 1–21 g nitrogen, 1–10 g phosphorus, and 0.21–2.21 ng cadmium, were scanned by NIRS, then analyzed by traditional methods for carbon, nitrogen, and phosphorus. Cadmium was determined in the concentrated samples by atomic absorption spectrophotometry. Coefficients of determination,r ², between chemically-measured and NIRS-predicted values were 0.921 for carbon, 0.852 for nitrogen, 0.869 for phosphorus, and 0.752 for cadmium. Several lines of evidence suggested that the organic material associated with cadmium was predominantly algae <3 m. NIRS is useful for measuring organic matter in this size fraction and is potentially useful for characterizing organic matter that binds metals.     

Fine root mass in relation to soil N supply in a cool temperate forest

Soil inorganic nitrogen supply and fine root mass in the top layers of mineral soil (0–5 and 5–10cm) were investigated at upper and lower sites of a cool temperate forest where Fagus crenata and Quercus crispula dominate. At both sites, soil inorganic nitrogen supply was greatest in the 0–5cm layer. The predominant forms of soil inorganic nitrogen supply were NH₄⁺-N at the upper site and NO₃^–-N at the lower site. Fine roots were concentrated in the 0–5cm layer at the upper site, but not at the lower site. The form of supplied soil inorganic nitrogen supply can be important in determining the vertical distribution of fine roots.     

Haploid plant regeneration via embryogenesis from anther cultures of Hepatica nobilis

An anther culture technique for the production of haploid plants was developed in Hepatica nobilis. Embryos with bipolar meristem regions were induced from microspores within the cultured anthers. Embryo formation was promoted by first culturing anthers on NN medium (Nitsch and Nitsch, 1969) supplemented with 1% activated charcoal (AC) at 5 or 35°C for a few days and by then incubating them in the dark at 25°C. Pre-culturing anthers at 35°C for 4days (thermal-shock treatment) led to the best embryo formation (45 embryos/Petri dish with 30 anthers). Plant regeneration was achieved by culturing the anther-derived embryos on NN medium without AC at 15°C. Flow cytometric analysis of anther-derived embryos and chromosome counts in regenerated plants showed that they were haploid plants.     

Proliferation and germination of somatic embryos from embryogenic suspension cultures in <Emphasis Type="Italic">Phœnix dactylifera</Emphasis>

The present study demonstrates a procedure for the rapid development of a high number of somatic embryos from embryogenic suspension culture. This method might be efficient for mass propagation of Phnix dactylifera L. Embryogenic callus placed in liquid medium with 10^–5M ABA yielded an average 72 embryos per 100ml of culture medium within 2months, while those placed on solid medium yielded an average of 33, 20 and 16 embryos per 100ml of culture medium respectively for 10^–7, 10^–6 and 10^–5 M ABA after 4months. The combination of 2,4-DIchlorophenoxyacetic acid (2,4-D) (4.5×10^–7M), glutamine (6.7×10^–4M), and ABA (10^–5M) (L8 liquid medium) showed a beneficial effect on somatic embryos production compared to 2,4-D and glutamine alone, while this combination significantly (p<0.05) increased the accumulation of storage proteins (144 and 138mgg^–1 DW respectively for Jihel and Bousthami noir cultivars) in somatic embryos. The somatic embryos which underwent maturation on medium containing only 4.5×10^–7M 2,4-D and 10^–5M ABA (L6 liquid medium) accumulated more sugars (292 and 265mgg^–1 DW respectively for Jihel and Bousthami noir) than those matured on any other liquid medium. Histological studies revealed that somatic embryos (developed in L6 and L8 liquid media) accumulated less reserve compounds (proteins and sugars) than zygotic embryos. The addition of activated charcoal (0.25 and 0.5gl^–1) and phytagel^® (2.5gl^–1) to the germination medium may be useful for enhancing the germination of Phnix dactyliferasomatic embryos.     

Preliminary Study of Vertebral Growth Rings in the Whale Shark, Rhincodon typus, from the East Coast of South Africa

Growth rings (GR) in vertebral centra of 15 whale sharks, Rhincodon typus, four female (418–750cm precaudal length), 10 male (422–770cm), and one of unknown sex (688cm), were examined using x-radiography. GR counts were made from scanned images and count precision was determined using the average percentage error index (4.19%) and the index of precision D (3.31%). In females, counts ranged from 19 GR (418cm) to 27 GR (750cm); in males from 20 GR (670cm) to 31 GR (770cm). Three mature males had 20 GR (670cm), 24 GR (744cm) and 27 GR (755cm). A female with 22 GR (445cm) was adolescent. There was a linear relationship between centrum dorsal diameter and body length, and back-calculated body lengths at number of GR are presented. A linear relationship between body length and number of GR prevented the calculation of von Bertalanffy parameters from either observed or back-calculated values.     

Effects of auxins and cytokinins on direct somatic embryogenesison leaf explants of Oncidium 'Gower Ramsey’

Four auxins (IAA, IBA, NAA and 2,4-D) and five cytokinins (2iP, zeatin,kinetin,BA and TDZ) were examined for their effects on direct somatic embryogenesis onleaf explantsof a sympodial orchid Oncidium 'Gower Ramsey.On a hormone-freebasal medium, the percentages of embryo formation were 40%, 20%,5% and0% on leaf tips, adaxial sides, wound surfaces and abaxial sides of theleaf explants, respectively, and the average number of embryos per explant was5.6. Embryo formation on leaf explants was retarded by all four auxins tested,but promoted by all the cytokinins. The percentages of embryo formation werereduced to 20%, 5–10%, 0% and 0%,respectively, in the same parts of leaf explants when supplemented with lowdogsages of IAA (0.3–3 mg/l) on the basal medium.Furthermore, embryo formation was totally inhibited by 3 mg/l NAA,0.3–3 mg/l IBA and 2,4-D. The sequence of embryo formationonvarious location of leaf explants was altered by 0.3–1 mg/l2iP and 3 mg/l zeatin, and embryo formation on adaxial sides>leaf tips>woundsurfaces>abaxial sides. The highest percentage of embryoformation on leaf tips, adaxial sides and wound surfaces of explants were75%, 50% and 20% when supplemented with 1mg/lTDZ, 1 mg/l 2iP and 0.3 mg/l kinetin, respectively.The highest average number of embryo per explant (10.7) was found on a basalmedium containing 1 mg/l TDZ.     

Viviparity and the maternal-embryonic relationship in the coelacanth Latimeria chalumnae

Synopsis Embryos of Latimeria chalumnae develop in well-vascularized compartments in the uterine region of the right oviduct. Compartments conform to the shape of their embryos and yolksacs; they represent a stable, gestation-induced oviductal modification. Late-term pups possess large, flaccid, vascular yolksacs almost devoid of yolk. The sac is in close contact with, but does not adhere to, the lumenal uterine surface. A massive vascular plexus occurs in the wall of the compartment at the site of contact with the yolksac; together they constitute a non-adherent, transposable placenta. The exterior surface of the yolksac is bounded by an attenuated, single-layered, squamous epithelium that surrounds an intercommunicating bed of cortical sinuses. The cortex of the sac is composed mostly of connective tissue stroma. The inner surface is bounded by a layer of yolk-digesting merocytes. Residual yolk occurs as yolk platelets that include yolk crystals. The interior surface of the sac is invested by an uniquely specialized vitelline circulation; no connection seems to exist between the interior of the yolksac and gut. The uterine wall consists of: (1) a lumenal surface composed of an anastomosing network of capillaries with a layer of attenuated, very thin, squamous epithelium, (2) a well-vascularized connective tissue stroma, (3) alternating transverse and longitudinal layers of smooth muscle, also well-vascularized, and (4) an external epithelial layer. Comparison of egg dry weight (184 g) with the estimated dry weights of a late-term pup (171 to 239 g) and a neonate (200 to 280 g) reveals a weight change of – 7 to + 30% and + 9 to + 52%, respectively. This is indicative of matrotrophy. In one female specimen, 19 remarkably large ovulated eggs were found and in another about 30 somewhat smaller ovarian ones. These are many more than ever could be accommodated in the uterine space. During the early and middle phases of development, embryos must be lecithotrophic, using their yolk reserves, with oophagy of fragmented supernumerary eggs as the most probable source of additional nutrients. The well-developed embryonic gut contains brown, amorphous yolk-like material. The limited amount of metachromatic secretory product of the uterine glands can play little or no role in embryonic nutrition.     

Soil phosphorus movement and budget after 13 years of fertilized cultivation in the Amazon basin

Agronomic studies on soil phosphorus dynamics have primarily focused on the plant-available inorganic P pool. However organic P and less labile inorganic pools can contribute significantly to plant P uptake. The objectives of this study were to determine the changes in inorganic and organic P pools of varying lability in and below the plowlayer after 13 years of continuous cultivation and fertilization on a Typic Paleudult in Yurimaguas, Peru. The field experiment was established after slash and burn of a secondary forest and included non-fertilized and fertilized treatments. The yearly cropping pattern consisted of an upland rice (Oryza sativa),-corn (Zea mays),-soybean (Glycine max) rotation. A modified version of the Hedley et al. procedure was used to sequentially fractionate soil P into increasingly recalcitrant organic and inorganic pools. Plowlayer accumulation of the fertilizer P occurred in all P pools. The greatest increase was in the NaOH extractable inorganic P pool. In the non-fertilized plots, the organic P decreased by 42%. Phosphorus fertilization resulted in significant movement of P below plowlayer. The accumulation occurred mostly in inorganic and organic P pools that are not quantified by traditional soil-P test methods. In fertilized plots sub-plowlayer total P increased by 90 g g^–1 (87%) while resin extractable P increased only 4 g g^–1. Phosphorus content of the organic P pools below the plowlayer increased by 24 g g^–1 (50%) in fertilized plots. The inclusion of less labile P pools in studies of P movement and the evaluation of P fertilizer residual values could lead to a better understanding of P dynamics and hence better management of P fertilization.     

The consistency of quantitative genetic estimates in field and laboratory in the yellow dung fly

How consistent quantitative genetic estimates are across environments is unclear and under discussion. Heritability (h ²) estimates of hind tibia length (body size), development time and diapause induction in the yellow dung fly, Scathophaga stercoraria, generated with various methods in various environments are reported and compared. Estimates varied considerably within and among studies, but yielded good overall averages. The genetic correlations between the sexes for body size and development time were expectedly high (r(sex)=0.57–0.78) but clearly less than unity, implying independent evolution of both traits in males and females of this sexually dimorphic species. Genetic and environmental variance components increased in proportion at variable field relative to constant laboratory conditions, resulting in overall similar h ². Heritabilities for males and females were also similar, and h ² of the morphological trait hind tibia length was not necessarily greater than that of the two life history traits. Full-sib (broad-sense) estimates (h ²=0.7–1.1) were 2–3 times greater than half-sib and parent/offspring (narrow-sense) estimates (h ²=0–0.6). Common environment (i.e., among-container) variance averaged 38.3% (body size) and 16.8% (development time) of the broad-sense genetic variance in two laboratory studies. The broad-sense h ², therefore, may contain substantial amounts (12–50%) of dominance variance and/or variance due to maternal effects. A general conclusion emerging from this and similar studies appears to be that whether field and laboratory genetic estimates differ depends on the environment, trait and species under consideration.     

First Field Studies of an Endangered South African seahorse, Hippocampus capensis

South Africa's endemic Knysna seahorse, Hippocampus capensis Boulenger 1900, is a rare example of a marine fish listed as Endangered by the IUCN because of its limited range and habitat vulnerability. It is restricted to four estuaries on the southern coast of South Africa. This study reports on its biology in the Knysna and Swartvlei estuaries, both of which are experiencing heavy coastal development. We found that H. capensis was distributed heterogeneously throughout the Knysna Estuary, with a mean density of 0.0089m^–2 and an estimated total population of 89000 seahorses (95% confidence interval: 30000–148000). H. capensis was found most frequently in low density vegetation stands (20% cover) and grasping Zostera capensis. Seahorse density was not otherwise correlated with habitat type or depth. The size of the area in which any particular seahorse was resighted did not differ between males and females. Adult sex ratios were skewed in most transects, with more males than females, but were even on a 10 by 10m focal study grid. Only three juveniles were sighted during the study. Both sexes were reproductively active but no greeting or courtship behaviours were observed. Males on the focal study grid were longer than females, and had shorter heads and longer tails, but were similar in colouration and skin filamentation. The level of threat to H. capensis and our limited knowledge of its biology mean that further scientific study is urgently needed to assist in developing sound management practices.     

Ontogenetic Behavior and Migration of Chinese Sturgeon, Acipenser sinensis

The Chinese sturgeon, Acipenser sinensis, is an anadromous protected species that presently only spawns in the Yangtze River. Using laboratory experiments, we examined the behavioral preference of young Chinese sturgeon to physical habitat (water depth, illumination intensity, substrate color, and cover) and monitored their downstream migration. Hatchling free embryos were photopositive, preferred open habitat, and immediately upon hatching, swam far above the bottom using swim-up and drift. Downstream migration peaked on days 0–1, decreased about 50% or more during days 2–7, and ceased by day 8. Days 0–1 migrants were active both day and night, but days 2–7 migrants were most active during the day. After ceasing migration, days 8–11 embryos were photonegative, preferred dark substrate and sought cover. Free embryos developed into larvae and began feeding on day 12, when another shift in behavior occurred–larvae returned to photopositive behavior and preferred white substrate. The selective factor favoring migration of free embryos upon hatching and swimming far above the bottom may be avoidance of benthic predatory fishes. Free embryos, which must rely on yolk energy for activity and growth, only used 19 cumulative temperature degree-days for peak migration compared to 234 degree-days for growth to first feeding larvae, a 1:12 ratio of cumulative temperature units. This ratio suggests that sturgeon species with large migratory embryos, like Chinese sturgeon, which require a high level of energy to swim during migration, may migrate only a short time to conserve most yolk energy for growth.     

Soybean, cowpea, groundnut, and pigeonpea response to soils, rainfall, and cropping season in the forest margins of Cameroon

Yields of groundnut, the traditional grain legume grown in central and southern Cameroon and in much of the humid zone of Central Africa, are generally low. Other food legumes may provide alternatives to groundnut. On-farm experiments examined the relative yields of up to 15 pigeonpea, 10 groundnut, 7 soybean, and 4 cowpea varieties over three growing seasons in four to six rural communities. Soil analytical values and rainfall data from all seasons were used as covariates in the analysis of variance. In the first two trials, variety-within-species interactions were significant (P<0.0001 and 0.04). Groundnut var. JL-24 yielded 60% more than local groundnuts in the first season of 2000, while soybean var. TGx1838-5E, local cowpea var. `Mefak' and pigeonpea var. ICEAP 00436 outyielded several other varieties of their respective species. Comparing these selected varieties over three seasons, significant species×community and species×season effects (P<0.0001) were observed. Covariate analysis showed that soybean yields increased with increasing soil Mg saturation and P levels. Groundnut yielded more in the first season of 2000 compared to the second seasons of 1999 and 2000 (average yields of 927 kg ha^–1 vs. 422 and 522 kg ha^–1, respectively). Improved yields were related to soil exchangeable Ca levels greater than 5 cmol(+) kg^–1 in both second seasons, but not during the first season. Cowpea yields were superior in both second seasons. Pigeonpea yields were unrelated to soil factors, showing its wide adaptability to soil conditions. Pigeonpea, which matured in February during the dry season, was severely affected by the early cessation of rains in 2000. In 1999 yields averaged 820 kg ha^–1 across communities. The results show that good food legume alternatives to groundnut exist, particularly for second season production. Species can be targeted to communities based on soil properties and season of production.