Female reproductive output in exploited Nile monitor lizard (Varanus niloticus L.) populations in Sahelian Africa

1999 ◽  
Vol 77 (10) ◽  
pp. 1530-1539 ◽  
Author(s):  
Vivian de Buffrénil ◽  
Frédérique Rimblot-Baly
Keyword(s):  
Reproductive Output ◽  
Energy Content ◽  
Local Level ◽  
Egg Laying ◽  
Relative Mass ◽  
Egg Mass ◽  
Lake Chad ◽  
Egg Maturation ◽  
Monitor Lizard ◽  
Local Sampling

Sexual maturation and ontogenetic development of gametes were studied in a sample of 481 female Nile monitor lizards (Varanus niloticus L.) (18.8-71.5 cm snout-vent length (SVL)) from the Lake Chad region in Chad and Nigeria and the central delta of the Niger River in Mali. The timing of egg maturation suggests that only one large clutch can be produced in 12 months, and that egg laying occurs between late November and early January. Each year, about 45-50% of mature females, on average, lay eggs, but local sampling shows that this proportion varies greatly. Females reach sexual maturity at 36 ± 2 cm SVL and 24 months of age. Clutch size (CS) increases from 12-13 to 53-60 eggs (average values for specimens of 36 cm and 71.5 cm SVL, respectively) with increase in SVL, according to the power function CS = 0.0049 SVL2.206 (specimens from Mali) or CS = 0.0052 SVL2.163 (specimens from the Lake Chad region). Conversely, the relative mass of the clutches (RCM) and their relative energy content (RWC) decrease during growth; hence, small (young) individuals are subjected to a much higher reproductive effort than large ones. Compared with that of most other large varanids, egg mass in the Nile monitor (38.8 g) is small, but reproductive output (CS) and effort (RCM, RWC) appear to be very high. Moreover, the specimens from Mali, where the species is heavily exploited, have a higher reproductive output and shorter longevity than those from the Lake Chad region. These data are discussed with reference to the ecology and local level of exploitation of the Nile monitor.

scholarly journals Reproductive traits of the gray ratsnake Ptyas korros from three geographically distinct populations

2012 ◽  
Vol 58 (6) ◽  
pp. 820-827 ◽  
Author(s):  
Long-Hui Lin ◽  
Fei Mao ◽  
Ce Chen ◽  
Xiang Ji
Keyword(s):  
Clutch Size ◽  
Egg Size ◽  
Reproductive Output ◽  
Reproductive Traits ◽  
Egg Laying ◽  
Laying Date ◽  
Egg Mass ◽  
Size Number ◽  
Female Reproductive Traits ◽  
Clutch Mass

Abstract We collected gravid gray rat snakes Ptyas korros from three geographically distinct populations in China, Chenzhou (CZ), Jiangshan (JS) and Dinghai (DH), to study geographical variation in female reproductive traits. Egg-laying dates differed among the three populations such that at the most northern latitude egg-laying was latest, and earliest at the most southern lati-tutde. Clutch size, clutch mass, egg mass, egg shape, within clutch variability in egg sizes and relative clutch mass differed among the three populations, whereas post-oviposition body mass did not. Except for egg-laying date, none of the traits examined varied in a geographically continuous trend. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar in nearly all traits examined. JS females were distinguished from CZ and DH females by their higher fecundity (clutch size), greater reproductive output (clutch mass) and more rounded eggs. Our data do not validate the prediction that larger offspring should be produced in colder localities. The absence of an egg size-number trade-off in each of the three populations presumably suggests that P. korros is among species where eggs are well optimized for size within a population.

Probiotics in the diets of laying quails

2020 ◽  
pp. 60-66
Author(s):  
O. Merzlyakova ◽  
V. Rogachyev ◽  
V. Chegodaev
Keyword(s):  
Bacillus Subtilis ◽  
Bacillus Licheniformis ◽  
Egg Production ◽  
Positive Impact ◽  
Hematological Parameters ◽  
Economic Effect ◽  
Egg Laying ◽  
Control Group ◽  
Egg Mass ◽  
The Cost

The efficiency of introducing probiotics based on strains of Bacillus subtilis, Bacillus licheniformis and their consortium in the amount of 150 g/t of feed into the diets of laying quails has been studied. The experiment lasting 182 days has been carried out on four groups of quails with 30 heads in each. The quails have been housed in the broiler battery in compliance with the required microclimate conditions. Quails of all groups have been received the main diet (compound feed) developed taking into account their age and physiological characteristics. The quails of the 1st, 2nd and 3rd experimental groups in addition to the main diet received probiotics (150 g/t compound feed) based on strains Bacillus subtilis, Bacillus licheniformis and their consortium, respectively. It has been found that feeding the laying quails of the consortium of strains Bacillus subtilis and Bacillus licheniformis had the most significant positive impact on their productive performance, it allowed to increase egg production by 7,81 %, egg laying intensity by 5,0 %, egg mass yield by 9,77 %, while reducing feed expenditures for 10 eggs by 13,35 %. The yield of hatching eggs has been increased by 7,03 %, hatchability of chickens from laid and fertilized eggs by 8,33 and 8,35 %, brooding waste decreased by 21,74 %. Hematological parameters of quails during the whole experiment were within the physiological norm. The economic effect calculated on the basis of data on the cost of compound feed, probiotics and the cost of sold eggs of quail laying was 14,56 % in the 3rd experimental group (in relation to the control group).

scholarly journals Reproductive suppression in female cooperatively breeding cichlids

2008 ◽  
Vol 4 (6) ◽  
pp. 606-609 ◽  
Author(s):  
Dik Heg
Keyword(s):  
Clutch Size ◽  
Group Living ◽  
Egg Laying ◽  
Alloparental Care ◽  
Large Female ◽  
Egg Mass ◽  
Small Female ◽  
Reproductive Suppression ◽  
Cooperatively Breeding ◽  
Female Subordinate

Suppression by dominants of female subordinate reproduction has been found in many vertebrate social groups, but has rarely been shown experimentally. Here experimental evidence is provided for reproductive suppression in the group-living Lake Tanganyika cichlid Neolamprologus pulcher . Within groups of three unrelated females, suppression was due to medium- and small-sized females laying less frequently compared with large females, and compared with medium females in control pairs. Clutch size and average egg mass of all females depended on body size, but not on rank. In a second step, a large female was removed from the group and a very small female was added to keep the group size constant. The medium females immediately seized the dominant breeding position in the group and started to reproduce as frequently as control pairs, whereas clutch size and egg mass did not change. These results show that female subordinate cichlids are reproductively capable, but apparently suppressed with respect to egg laying. Nevertheless, some reproduction is tolerated, possibly to ensure continued alloparental care by subordinate females.

scholarly journals From individual to population level: Temperature and snow cover modulate fledging success through breeding phenology in greylag geese (Anser anser)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Didone Frigerio ◽  
Petra Sumasgutner ◽  
Kurt Kotrschal ◽  
Sonia Kleindorfer ◽  
Josef Hemetsberger
Keyword(s):  
Ambient Temperature ◽  
Reproductive Output ◽  
Population Level ◽  
Egg Laying ◽  
Future Research ◽  
Breeding Phenology ◽  
Anser Anser ◽  
Fledging Success ◽  
Average Annual Temperature ◽  
Greylag Geese

AbstractLocal weather conditions may be used as environmental cues by animals to optimize their breeding behaviour, and could be affected by climate change. We measured associations between climate, breeding phenology, and reproductive output in greylag geese (Anser anser) across 29 years (1990–2018). The birds are individually marked, which allows accurate long-term monitoring of life-history parameters for all pairs within the flock. We had three aims: (1) identify climate patterns at a local scale in Upper Austria, (2) measure the association between climate and greylag goose breeding phenology, and (3) measure the relationship between climate and both clutch size and fledging success. Ambient temperature increased 2 °C across the 29-years study period, and higher winter temperature was associated with earlier onset of egg-laying. Using the hatch-fledge ratio, average annual temperature was the strongest predictor for the proportion of fledged goslings per season. There is evidence for an optimum time window for egg-laying (the earliest and latest eggs laid had the lowest fledging success). These findings broaden our understanding of environmental effects and population-level shifts which could be associated with increased ambient temperature and can thus inform future research about the ecological consequences of climate changes and reproductive output in avian systems.

Environmental Change, Migration, and Conflict in Africa: A Critical Examination of the Interconnections

2017 ◽  
Vol 26 (4) ◽  
pp. 351-374 ◽  
Author(s):  
Laura Freeman
Keyword(s):  
Environmental Change ◽  
Political Violence ◽  
Local Level ◽  
Critical Examination ◽  
Population Movements ◽  
Lake Chad ◽  
Islamic Terrorism ◽  
Conflict In Africa ◽  
Intervening Variables ◽  
Causal Variable

How should we understand the interconnections between environmental change, migration, and conflict in Africa? Should the rise of Islamic terrorism and Boko Haram in northeast Nigeria be directly linked to the drying of Lake Chad? Should cattle raiding in Kenya be seen as a result of drought across East Africa? Does the constrained migration of the pastoral Tuareg in the Sahel causally connect to desertification and their rebellion against governmental forces? Despite the compelling and often persuasive case for directly connecting environmental change to migration and conflict, there is a growing agreement in both the environment-migration and climate-conflict spheres that intervening variables determine if and how environmental change causes population movements and political violence. This article presents a case for migration as an intermediary and bidirectional causal variable. The article argues that close attention needs to be paid to local-level manifestations of conflict and (mal)adaptive forms of migration to understand the potential propensity of environmental change to lead to conflict in Africa.

Soybean Foliage Consumption Reduces Adult Western Corn Rootworm (Diabrotica virgifera virgifera)(Coleoptera: Chrysomelidae) Survival and Stimulates Flight

2021 ◽  
Author(s):  
Joseph L Spencer ◽  
Timothy R Mabry ◽  
Eli Levine ◽  
Scott A Isard
Keyword(s):  
Wind Tunnel ◽  
Crop Rotation ◽  
Diabrotica Virgifera Virgifera ◽  
Western Corn Rootworm ◽  
Egg Laying ◽  
Corn Rootworm ◽  
Diabrotica Virgifera ◽  
Egg Maturation ◽  
Behavioral Resistance ◽  
Collection Sites

Abstract Western corn rootworm, Diabrotica virgifera virgifera LeConte, biology is tied to the continuous availability of its host (corn, Zea mays L.). Annual rotation of corn with a nonhost, like soybean (Glycine max (L.) Merrill) was a reliable tactic to manage western corn rootworm. Behavioral resistance to annual crop rotation (rotation resistance) allowed some eastern U.S. Corn Belt populations to circumvent rotation by laying eggs in soybean and in cornfields. When active in soybean, rotation-resistant adults commonly consume foliage, in spite of detrimental effects on beetle survival. Rotation-resistant beetle activity in soybean is enabled by the expression of certain proteinases and an adapted gut microbiota that provide limited protection from soybean antiherbivore defenses. We investigated the effects of corn and soybean herbivory on rotation-resistant female survival and initiation of flight using mortality assays and wind tunnel flight tests. Among field-collected females tested with mortality assays, beetles from collection sites in a cornfield survived longer than those from collection sites in a soybean field. However, reduced survival due to soybean herbivory could be restored by consuming corn tissues. Field-collected beetles that fed on a soybean tissue laboratory diet or only water were more likely to fly in a wind tunnel than corn-feeding beetles. Regardless of collection site and laboratory diet, 90.5% of beetles that flew oriented their flights upwind. Diet-related changes in the probability of flight provide a proximate mechanism for interfield movement that facilitates restorative feeding and the survival of females previously engaged in soybean herbivory. Rotation-resistant western corn rootworm females feeding on soybean tissues experience reduced survival in mortality assays and display increased flight probability (which may facilitate flight back to a cornfield where consumption of host tissues improves survival potential and facilitates maturation of eggs). The consequences of soybean herbivory provide a proximal mechanism for behavioral resistance to crop rotation. Increased egg-laying probability while feeding on soybean tissues, facilitation of egg maturation while feeding on corn tissues, and interfield movement are previously documented consequences.

Biennial Reproductive Cycle of Blue King Crab, Paralithodes platypus, at the Pribilof Island, Alaska and Comparison to a Congener, P. camtschatica

1989 ◽  
Vol 46 (6) ◽  
pp. 932-940 ◽  
Author(s):  
Gregory C. Jensen ◽  
David A. Armstrong
Keyword(s):  
Carapace Length ◽  
Reproductive Output ◽  
Size Range ◽  
Egg Mass ◽  
King Crab ◽  
Pribilof Island ◽  
Blue King Crab ◽  
Paralithodes Platypus ◽  
One Year ◽  
Reproductive Events

Pribilof Island blue king crab (BKC; Paralithodes platypus) were sampled by beam trawl in May and August of 1983 and April 1984 to determine timing of reproductive events. Biennial reproduction was found to be the result of slow ovarian growth in large, muciparous females, while smaller primiparous females are often able to spawn in two consecutive years. Mating and egg extrusion occur in late March to early May and eggs hatch in mid-April of the following year, consequently, the embryonic period and rate of development is approximately 12 mo, similar to that of its congener the red king crab (RKC; P. camtschatica). Comparison of the reproductive output of the two species revealed that despite the 2 yr ovarian cycle, BKC only produce 20–30% more dry egg mass at any carapace length than do RKC, a substantially smaller difference than previously calculated. One year after molt, females of both species are not significantly different in dry body weight over a size range of 100–140 mm carapace length, but RKC have produced about three times more dry ovarian weight than BKC of comparable size, suggesting that biennial reproduction in BKC may be the result of energetic limitations.

An ultrastructural study of oogenesis, fertilization, and egg laying in a nemertean ectosymbiont of crabs, Carcinonemertes epialti (Nemertea, Hoplonemertea)

1986 ◽  
Vol 64 (6) ◽  
pp. 1256-1269 ◽  
Author(s):  
Stephen A. Stricker
Keyword(s):  
Ultrastructural Study ◽  
Gravid Female ◽  
Somatic Cells ◽  
Egg Laying ◽  
Egg Mass ◽  
Stages Of Development ◽  
Endocytotic Vesicles ◽  
Brachyuran Crabs ◽  
Germinal Cells ◽  
Sexually Mature

The nemertean worm Carcinonemertes epialti occurs ectosymbiotically on brachyuran crabs and becomes sexually mature while feeding on the eggs of its host. Gravid worms possess numerous saccular ovaries that lie among serially arranged diverticula of the intestine. The epithelium surrounding the lumen of each ovary contains germinal cells at various stages of development and somatic cells. Previtellogenic oocytes are typically situated in the subepidermal region of the ovarian epithelium, whereas vitellogenic oocytes tend to occur toward the intestine. The presence of numerous synthesizing organelles in vitellogenic oocytes indicates that at least some yolk constituents are produced within the ooplasm by an autosynthetic method. A supplemental form of heterosynthetic vitellogenesis may also occur, since somatic cells situated next to yolk-forming oocytes possess putative endocytotic vesicles that might help to transport yolk components derived from ingested crab eggs to the developing oocytes. Fully formed primary oocytes in the lumen of the ovary lack extracellular coats and typically measure 70–75 μm in diameter. Following fertilization, several egg strings that characteristically contain about 200 developing embryos are deposited by each gravid female in the egg mass of the crab.

population ecology of the Australian frog Crinia signifera: egg-laying patterns and egg mortality

1994 ◽  
Vol 21 (6) ◽  
pp. 621 ◽  
Author(s):  
I Williamson ◽  
CM Bull
Keyword(s):  
Population Ecology ◽  
Water Body ◽  
Significant Variation ◽  
Hatching Success ◽  
Egg Laying ◽  
Egg Mass ◽  
Egg Mortality ◽  
Different Depths ◽  
Small Clusters ◽  
Overall Mortality

There are few studies of embryo mortality in anurans, and most of these studies deal with anurans that deposit clutches as one egg mass. In this study, egg mortality in Crinia signifera, an anuran that distributes its clutches in small clusters of eggs, was examined with the aims of: (i) determining overall mortality levels, and (ii) determining whether there was significant variation in success between clutches laid by different females. Hatching success varied significantly between years and between habitats, and was as low as 2% in some habitats in some years. Fungal infection caused most mortality, and hatching success was higher in temporary pools than in a permanent water body. Although significant variation in clutch success between females could occur if clutches were laid in different habitats or at different times, it was not clear whether there would be significant variation in clutch success between females laying simultaneously in the same water body. Differences in success of clutches might occur if females distributed eggs at different depths or in different-sized clusters. However, information on inter-female variation in these components of egg-laying behaviour in C. signifera is currently unavailable.

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