Ovigeny strategy of the parasitic wasp Cosmocomoidea annulicornis (Hymenoptera: Mymaridae): effect of female age, feeding and host availability on reproductive traits

The reproductive traits of the mymarid wasp Cosmocomoidea annulicornis (Ogloblin) (Hymenoptera: Mymaridae) attacking eggs of the sharpshooter Tapajosa rubromarginata (Signoret) (Hemiptera: Cicadellidae) were evaluated under laboratory conditions. Bioassays were carried out to estimate the realized fecundity and egg load of females. The ovigeny index was calculated and different biological traits, such as body size, oöcyte length, gaster length and wing length, were analysed to assess significant associations between these traits and the species fitness. In addition, the effect of host availability and feeding on longevity and potential fecundity throughout life and the effect of female age on egg maturation dynamics were assessed. The results showed that C. annulicornis is a strongly synovigenic species. A positive correlation was found between fecundity and longevity of the females and between body size and oöcyte length. Contrary to expected, body size was not related to fecundity and longevity. Females lived significantly longer in the presence of hosts and honey than when they were host-deprived and honey-fed or both host and honey deprived. Host availability had a significant effect on the amount of eggs laid by C. annulicornis females. Female age was negatively associated with oöcyte length. Furthermore, females were able to mature additional eggs as they aged, nevertheless, when host-deprived, senescent females presented significantly less mature eggs than younger ones, suggesting a possible egg oosorption. These results might contribute to a better understanding of the reproductive potential of this species as a biocontrol agent.

Macroevolutionary Trade-Offs and Trends in Life History Traits of Cephalopods Through a Comparative Phylogenetic Approach

One of the major mechanisms responsible for the animals’ fitness dynamics is fecundity. Fecundity as a trait does not evolve independently, and rather interacts with other traits such as body and egg size. Here, our aim was to correctly infer the macroevolutionary trade-offs between body length, egg length, and potential fecundity, using cephalopods as study model. The correlated evolution among those traits was inferred by comparative phylogenetic methods. Literature data on biological and reproductive traits (body length, egg length, and potential fecundity) was obtained for 90 cephalopod species, and comparative phylogenetic methods based on a previous molecular phylogeny were used to test the correlated evolution hypothesis. Additionally, we estimated the phylogenetic signal and fitted five different evolutionary models to each trait. All traits showed high phylogenetic signal, and the selected model suggested an evolutionary trend toward increasing body length, egg length, and fecundity in relation to the ancestral state. Evidence of correlated evolution between body length and fecundity was observed, although this relationship was not detected between body length and egg length. The robust inverse relationship between fecundity and egg length indicates that cephalopods evolved a directional selection that favored an increase of fecundity and a reduction of egg length in larger species, or an increase in egg length with the concomitant reduction of fecundity and body length in order to benefit offspring survival. The use of phylogenetic comparative methods allowed us to properly detect macroevolutionary trade-offs.

Molecular and Biological Analysis on Ommastrephes caroli Findings in the Central Western Mediterranean Sea (Sardinian Waters) Including First Age Investigation Using Eye Lenses and Beaks

Molecular identifications based on two mitochondrial markers (cytochrome c oxidase subunit I -COI- and 16S ribosomal RNA gene -16S-) have been implemented to confirm the morphological identification of eight specimens collected in the Central western Mediterranean. Molecular data show they belonged to a recently resurrected species of the genus Ommastrephes, i.e., O. caroli, known to be distributed in the Atlantic Ocean and Mediterranean Sea. Despite this, molecular analyses of COI sequences evidenced the presence of potential genetic differentiation between Mediterranean and Atlantic samples, highlighting the need for further studies, with more individuals to investigate the connectivity between individuals living in the two areas. Furthermore, morphological, biometric and reproductive features here reported, could be useful in evaluating possible distinctive biological features between the Mediterranean and Atlantic individuals. Female mature size was larger than the male. The relationships obtained between the beak measurements and body sizes (DML; TW) were better described by a power model. Asynchronous oocytes development with relatively small oocytes (0.05–1.10 mm) and a protracted intermittent spawning with active feeding were observed. This study also reported for the specie O. caroli the first data on the potential fecundity estimated (840061 oocytes), the oviducal load (90000 ripe oocytes) as well as the number of seminal receptacles and the size and morphology of the spermatangia found in the buccal mass of all mated females. Even if on a low sample size, beaks and eye lenses were used for the first time in O. caroli for age estimation. The statistically significant relationship found between increments counted in eye lenses and beaks highlighted the reliability of the lenses to estimate age in O. caroli, even if further studies will be needed for its validation. Assuming a daily increment for both structures, a mean life span of about 12–13 months was estimated for both sexes, which is consistent with the sexual maturity condition observed in all the samples and the semelparity known for cephalopods coleoids.

Two-sex life table and host preference studies of Bactrocera dorsalis Hendel (Diptera: Tephritidae)

Oriental fruit fly, Bactrocera dorsalis, is a serious invasive pest in tropical and subtropical countries. The stage-specific two-sex pooled life table of B. dorsalis on four different fruits (guava, water apple, rose apple and mango) were studied during 2018-2020. The life table showed that the survivorship of B. dorsalis falls in Type III with about 41.394-33.827per cent of the eggs successfully reached adult stage. The highest mortality recorded was in the egg and adult emergence stages with kx of 0.045-0.113 and 0.032-0.192, respectively. The average potential fecundity (Pf) was 223-362 eggs female-1. The intrinsic rate of natural increase (rm) was 0.021-0.035 female-1 day-1 with mean generation time (Tc) of 194.058-148.710 days. The net reproductive rate (Ro) was 61.504-176.006 female offspring per female and the population doubling time (DT) was within 32.719-19.946 days. The population dynamics of B. dorsalis were significantly influenced by the host fruits due to their respective phytoconstituents in terms of host suitability or susceptibility (guava> water apple> rose apple> mango). Host preference of B. dorsalis was in the order of guava> water apple>rose apple.

FEATURES OF THE REPRODUCTIVE FUNCTION OF KARACHAY GOATS DEPENDING ON DIFFERENT GEOGRAPHICAL AREAS OF BREEDING

In recent years, goat breeds with a dairy-meat-wool or combined productivity type, represented by local breeds that are bred mainly in the foothills and mountainous regions of the North Caucasus, Altai, Tyva and Khakassia, have become increasingly widespread in Russia. The Karachay goat population is the most interesting for research, since in their breeding was aimed at obtaining animals with a number of unique productive characteristics and capable of producing the required outputs under the harsh conditions of the mountain and foothill zones of the Caucasus. In view of the limited research on these animals, in particular their reproductive functions, the aim of this study was to investigate the natural implementation of the reproductive function of the Karachay goats in different geographical areas of breeding. There are slight differences in some parameters of Karachay goat reproduction in high mountain zone (from 2000 m a.s.l.) and middle mountain zone (1000–1500 m a.s.l.). An important conclusion is that the recognized low fertility of the Karachay goats is not genetically determined. Analyzing the number of ovulations and fresh yellow bodies in the ovaries by laparoscopy using Karl Storz (Germany) endoscopic equipment, the authors found a potential fecundity of 3.1 (2.8 to 3.4).

Oviposition Behavior and Development of Aster Leafhoppers (Hemiptera: Cicadellidae) on Selected Host Plants From the Canadian Prairies

Some plant pathogens are capable of manipulating their insect vectors and plant hosts in a way that disease transmission is enhanced. Aster leafhopper (Macrosteles quadrilineatus Forbes) (Hemiptera: Cicadellidae) is the main vector of Aster Yellows Phytoplasma (Candidatus Phytoplasma asteris) in the Canadian Prairies, which causes Aster Yellows (AY) disease in over 300 plant species including cereals and oilseeds. However, little is known about the host range of Aster leafhoppers or their host-choice selection behavior in this geographical region. Several crop and noncrop species commonly found in the Canadian Prairies were evaluated as food and reproductive hosts for Aster leafhoppers through no-choice bioassays. To study possible effects of pathogen infection, AY-uninfected and AY-infected insects were used. Cereals and some noncrops like fleabane were suitable reproductive hosts for Aster leafhoppers, with numbers of offspring observed in treatments using both AY-uninfected and AY-infected insects, suggesting an egg-laying preference on these plant species. Development was similar across the different plant species, except for canola and sowthistle, where growth indexes were lower. Sex-ratios of Aster leafhopper adults did not differ among the plant species or with respect to AY infection. Potential fecundity differed across plant species and was affected by the infection status of the insect. These findings have implications for AY epidemiology and suggest that while cereals can be suitable host plants for Aster leafhopper oviposition and development, some noncrop species could act as alternate hosts for leafhoppers that migrate into the Canadian Prairies before emergence of cereal and canola crops.

Population dynamics of the Mediterranean green crab Carcinus aestuarii Nardo, 1847 (Crustacea: Portunidae) in the Gediz Delta (İzmir Bay, Eastern Aegean Sea)

A total of 6265 Mediterranean green crabs Carcinus aestuarii were sampled from the Gediz Delta in the eastern Aegean Sea (Turkey) during 24 sampling surveys with a 15-day interval from November 2014 to October 2015. The overall ratio of males to females was 1.8:1. Males were predominant in all sampling surveys, except in September 2015. The ranges of total weight (W) and carapace width (CW) for all crabs were 0.19–45.74 g and 8–53 mm. Male crabs were, on average, larger and heavier than females. The W–CW relationships were W=0.0004×CW2.88 for females, and W=0.0003×CW2.96 for males. The estimated von Bertalanffy growth parameters for females were: CW∞=49 mm, K=0.82 year-1 and t0=-0.9 year, and for males CW∞=54 mm, K=0.92 year-1 and t0=-0.96 year. The total mortality rates were 2.25 and 2.27 year-1 for females and males, respectively. The breeding season spans from mid fall to early spring peaking in winter. The recruitment of juveniles to the lagoon happens predominantly in summer. The median size at first maturity was 30.6 mm for females and 41.5 mm for males. The average potential fecundity estimate was 63565±36519 oocytes per female crab while the average realized fecundity was 42810±33310 eggs.

Morphological features of the Black Sea turbot (Scophthalmus maeoticus) during the period of embryonic development

Black Sea turbot (hereinafter BST), Scophthalmus maeoticus (Pallas, 1814), is a valuable fish for commercial fishery and promising object of industrial mariculture. Potential fecundity of BST is very high, 3–13 million eggs; however, survival of its progenies during early development in the sea is unpredictable and low (mortality is up to 90 %). In nature fertilized pelagic BST eggs rise to the sea surface in 2–3 hours; BST develop in upper waters being part of neuston till hatching. BST on its early stages of development could be considered the most vulnerable as the embryo is exposed to diverse adverse effects. The survival and physiological state of the larvae at hatching till exogenous feeding depend on the norm of morphological characteristics of the embryos during their development. Our aim was to study the norm of the changes in BST morphological characteristics during embryogenesis. Morphological analysis of the BST embryogenesis stages from fertilization till hatching on the basis of detailed study of intact embryos (> 2000 eggs) sampled from different experimental batches incubated under experimental conditions is presented. Digital photos and videos of alive eggs were taken with Canon PowerShot A720 using binocular microscope MBS-10 at magnification 8×4 and under light inverted microscope Nikon Eclipse TS100, equipped with analog camera, at magnification ×4, ×10, and ×40. The morphological features of embryogenesis in BST before and after fertilization, cleavage, blastulation, gastrulation, epiboly, and neurulation and until hatching are presented by photos with detailed description of transforming embryological structures. Fertilized pelagic BST eggs covered by transparent shell vary from (1.26 ± 0.14) to (1.31 ± 0.15) mm in diameter, have homogenously distributed yolk and a single round transparent oil drop of 0.20–0.21 mm, positioned at the top of the yolk. Scale of timing of morphological changes is presented in relative time units (as a time interval from fertilization until the emergence of morphological structure in percentage of the total duration of embryogenesis, % RT). Cleavage starts at 2.5 % RT. Cell division desynchronizes between the 6th and 7th cleavage, at 128 blastomeres. Yolk syncytial layer controlling processes of epiboly, cells differentiation, and morphogenesis is formed during the 10th–11th mitotic cycle (12 % RT, about 512–1024 cells). From the germ ring registered at 21 % RT, the embryonic shield develops (at 25 % RT), and organize formation of embryonic axis from 20 to 50 % epiboly (31 % RT). During 70–75 % epiboly (40–45 % RT), the neural keel is formed; notochord and optical primordia become visible; Kupffer’s vesicle emerges at the start of segmentation. Optic cups develop, and more than 20 somites are observed at the end of epiboly (49 % RT). By 60 % RT the Kupffer’s vesicle disappears in tail bud formed; lens placodes are formed in optic cups. Notochord vacuolization, myotomes formation, and tail growth are observed by 65 % RT. The caudal part of the body separates from the yolk by 70–75 % RT. About 80 % RT neuromuscular activity starts; heart beating initiates; free tail covers more than 60 % of the yolk; differentiating xantophores give a pinkish hue to the embryo. By 90–95 % RT eye cups with lenses; three symmetric otic capsules with otoliths, melanophores, and xantophores present in the embryo with 33–38 body somites; it performs jerky movements. Prior hatching, the egg shell becomes elastic, stretches, and breaks in the head area. Hatching occurs 114–94 hours after fertilization at +14…+16 °С. By hatching, all organs are formed in bilateral symmetrical BST larva (standard length is (2.53 ± 0.13) to (2.91 ± 0.10) mm), three auditory chambers with otoliths exist, eyes are non-pigmented, intestinal tract is closed; within 3–5 days it develops at the expense of yolk. Description of morphological changes in the BST embryo at norm of development could be used for elaboration of criteria of developing BST eggs both in natural environment and under cultivation conditions.

New insights in oocyte dynamics shed light on the complexities associated with fish reproductive strategies

Information on temporal variations in stock reproductive potential (SRP) is essential in fisheries management. Despite this relevance, fundamental understanding of egg production variability remains largely unclear due to difficulties in tracking the underlying complex fluctuations in early oocyte recruitment that determines fecundity. We applied advanced oocyte packing density theory to get in-depth, quantitative insights across oocyte stages and seasons, selecting the commercially valuable European hake (Merluccius merluccius) as a case study. Our work evidenced sophisticated seasonal oocyte recruitment dynamics and patterns, mostly driven by a low-cost predefinition of fecundity as a function of fish body size, likely influenced also by environmental cues. Fecundity seems to be defined at a much earlier stage of oocyte development than previously thought, implying a quasi-determinate – rather than indeterminate – fecundity type in hake. These results imply a major change in the conceptual approach to reproductive strategies in teleosts. These findings not only question the current binary classification of fecundity as either determinate or indeterminate, but also suggest that current practices regarding potential fecundity estimation in fishes should be complemented with studies on primary oocyte dynamics. Accordingly, the methodology and approach adopted in this study may be profitably applied for unravelling some of the complexities associated with oocyte recruitment and thereby SRP variability.

Experimental increase in female mass during the fertile phase leads to enhanced extra-pair paternity in pied flycatchers Ficedula hypoleuca

Female mass in most altricial birds reaches its maximum during breeding at egg-laying, which coincides temporally with the fertile phase when extra-pair paternity (EPP) is determined. Higher mass at laying may have two different effects on EPP intensity. On the one hand, it would lead to increased wing loading (body mass/wing area), which may impair flight efficiency and thereby reduce female’s capacity to resist unwanted extra-pair male approaches (sexual conflict hypothesis). On the other hand, it would enhance female condition, favouring her capacity to evade mate-guarding and to search for extra-pair mates (female choice hypothesis). In both cases, higher female mass at laying may lead to enhanced EPP. To test this prediction, we reduced nest building effort by adding a completely constructed nest in an experimental group of female pied flycatchers (Ficedula hypoleuca). Our treatment caused an increase in mass and thereby wing loading and this was translated into a significantly higher EPP in the manipulated group compared with the control group as expected. There was also a significant negative relationship between EPP and laying date and the extent of the white wing patch, an index of female dominance. More body reserves at laying mean not only a higher potential fecundity but a higher level of EPP as well. This interaction had not previously received due attention but should be considered in future studies of avian breeding strategies.