Life Cycle Of Species Research Articles

FOUR CHALLENGES OF LONG-TERM SOCIO-ECOLOGICAL RESEARCH IN BRAZIL

Long Term Ecological Research (LTER) aims to monitor natural ecological processes that operate over longer time periods than are typically permitted by standard research grants (e.g. species life cycles, natural resource dynamics, and the ecological effects of climate changes). Despite the enormous success of LTER, many of the initial projects largely overlooked the consequences of their study sites being embedded in wider socio-ecological systems. This potential shortcoming led to the development of Long Term Socio-Ecological Research (LTSER), a logical extension of LTER that seeks to fully integrate the human dimension into long term environmental monitoring. LTSER sites have now been successfully established in many countries, although such an approach is still incipient in Brazil´s program of LTER (known by the acronym PELD in Portuguese). The PELD APA Costa de Corais is one of Brazil’s newest PELD sites, and intentionally incorporated a strong socio-ecological focus into its design and implementation. In this brief perspective we draw on our experiences of creating a LTSER, identifying four key challenges that need to be overcome to ensure successful implementation.

In Silico Identification of Chemicals Capable of Binding to the Ecdysone Receptor.

The process of molting, known alternatively as ecdysis, is a feature integral in the life cycles of species across the arthropod phylum. Regulation occurs as a function of the interaction of ecdysteroid hormones with the arthropod nuclear ecdysone receptor-a process preceding the triggering of a series of downstream events constituting an endocrine signaling pathway highly conserved throughout environmentally prevalent insect, crustacean, and myriapod organisms. Inappropriate ecdysone receptor binding and activation forms the essential molecular initiating event within possible adverse outcome pathways relating abnormal molting to mortality in arthropods. Definition of the characteristics of chemicals liable to stimulate such activity has the potential to be of great utility in mitigation of hazards posed toward vulnerable species. Thus the aim of the present study was to develop a series of rule-sets, derived from the key structural and physicochemical features associated with identified ecdysone receptor ligands, enabling construction of Konstanz Information Miner (KNIME) workflows permitting the flagging of compounds predisposed to binding at the site. Data describing the activities of 555 distinct chemicals were recovered from a variety of assays across 10 insect species, allowing for formulation of KNIME screens for potential binding activity at the molecular initiating event and adverse outcome level of biological organization. Environ Toxicol Chem 2020;39:1438-1450. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Herbicides employed in sugarcane plantations have lethal and sublethal effects to larval Boana pardalis (Amphibia, Hylidae).

The increasing demand for biofuels favored the expansion of sugarcane and, as a consequence, in the consumption of pesticides in Brazil. Amphibians are subject to pesticide exposure for occurring in or around sugarcane fields, and for breeding at the onset of the rainy season when pesticide consumption is common. We tested the hypothesis that herbicides used in sugarcane crops, although employed for weed control and manipulated at doses recommended by the manufacturers, can cause lethal and sublethal effects on amphibian larvae. Boana pardalis was exposed to glyphosate, ametryn, 2,4-D, metribuzin and acetochlor which account to up to 2/3 of the volume of herbicides employed in sugarcane production. High mortality was observed following prolonged exposure to ametryn (76%), acetochlor (68%) and glyphosate (15%); ametryn in addition significantly reduced activity rates and slowed developmental and growth rates. AChE activity was surprisingly stimulated by glyphosate, ametryn and 2,4-D, and GST activity by ametryn and acetochlor. Some of these sublethal effects, including the decrease in activity, growth and developmental rates, may have important consequences for individual performance for extending the larval period, and hence the risk of dessication, in the temporary and semi-permanent ponds where the species develops. Future studies should seek additional realism towards a risk analysis of the environmental contamination by herbicides through experiments manipulating not only active ingredients but also commercial formulations, as well as interactions among contaminants and other environmental stressors across the entire life cycle of native amphibian species.

Do intertidal Zostera noltei meadows represent a favourable habitat for amphipods? The case of the Kneiss Islands (Gulf of Gabès: Central Mediterranean Sea)

AbstractThe structure, diversity, spatial and seasonal distributions of amphipod assemblages associated with intertidal Zostera (Zosterella) noltei meadows were studied around the Kneiss Islands (central Mediterranean Sea). This site represents a site of international interest in terms of its ornithological diversity (Important Bird Area, Ramsar Site and SPAMI). The amphipod fauna was sampled at 32 stations in spring 2014. A total of 6,482 individuals belonging to 78 species and 22 families were identified; among these taxa, Lysianassa ceratina is new for the Tunisian amphipod inventory, whereas 25 species are identified for the first time in the Gulf of Gabès. The dominant species are Cymadusa filosa, Microdeutopus gryllotalpa, Gammarus insensibilis, Dexamine spiniventris, Monocorophium insidiosum, Elasmopus rapax, Melita palmata and Leucothoe incisa. Four amphipod assemblages are identified using MDS analysis. The distribution of amphipod assemblages is linked to several environmental factors, such as sediment type, organic matter content and distance from the shore, which is itself associated with a clear inshore–offshore gradient. Seasonal variations of the amphipod assemblage patterns at eight stations, sampled between April 2014 and January 2015, show a maximum abundance and diversity during summer and autumn, with a minimum in winter. These seasonal fluctuations may be related to many factors such as variations of climatic factors (e.g. temperature, salinity), the growth and production rates of Zostera noltei meadows and seasonal patterns in the life cycle of dominant species.

What do Eumerus Meigen larvae feed on? New immature stages of three species (Diptera: Syrphidae) breeding in different plants

The genus Eumerus Meigen 1822 (Diptera: Syrphidae) is widely distributed in the Old World, though recently introduced into America, and their larvae feed on decaying vegetal material and/or inside underground storage organs of many plants, sometimes generating economic losses as pests. However, little is known about Eumerus larval cycles and their interactions with host plants. Here, immatures of three Eumerus species from different continents are described, noting their feeding habits and host plants. Larvae of Eumerus figurans Walker 1859 were obtained from Hawaiian cultured ginger roots; puparium of Eumerus alpinus Rondani 1857 originated from larvae collected in Asphodelus ramosus L. in France; puparia of Eumerus superbus Shannon 1927 were reared from larvae found in two Zamiaceae species from Australia. Mitochondrial COI sequences served for diagnosing E. figurans larvae. Optical and scanning electron microscopy were used to describe body features, head skeletons, anterior spiracles, pupal spiracles, and posterior respiratory processes. Overall, E. alpinus resembles E. nudus Loew 1848 immatures. Eumerus superbus has a remarkable morphology among all described immatures of the genus, being the only Eumerus reported from gymnosperms. Head skeleton of E. figurans suggests this species is a filtering one. Present findings show that larvae of Eumerus can be separated at the species level and that this genus is polyphagous, feeding on a wide range of plant tissues and taxa, including commercial species. This study emphasizes immature stages and breeding sites as important means to understand species life cycles and the interactions with their host plants and ecosystems.

Reaching similar goals by different means – Differences in life-history strategies of clonal and non-clonal plants

Clonality is a largely underexplored plant life-history trait with possibly profound effects on plant demography. Clonal growth constitutes an alternative reproductive pathway, which should provide clonal species with an advantage over non-clonal ones under disturbance regimes unfavourable to regeneration from seeds.We investigated how clonal and non-clonal species differ in their life histories (other than clonality) and how this relates to disturbance regimes where the studied species occur. Further, we focused on the contribution of clonality to fluctuations in the populations of species and the importance of clonality for the life cycle of a species in relation to its other life-history characteristics. We achieved this through phylogenetically informed analyses of the matrix population models available from the COMPADRE database coupled with information on species clonality from the CLO-PLA database.The phylogenetic principal component analysis revealed that plant life-history characteristics could be aligned along two gradients. The gradient of generation time and individual turnover in populations was more important and corresponded to the frequency of habitat disturbance. Clonal species on average had populations with lower overall rates of individual turnover and disturbance frequencies. The second gradient was correlated with disturbance severity and plant ability to regenerate after the loss of biomass. The importance of clonal growth for the life cycle of a clonal species increased with more severe disturbance events. The fluctuation of population growth rates depended on the life-history characteristics of a species but not on clonality. The net effect of clonal growth on the fluctuations of the populations of a species was positive.In general, clonality seems to provide an important alternative for adjusting plant life history to the disturbance regime and other site conditions allowing a plant to circumvent its morphological or developmental constraints. Clonal growth turned out to be mainly a mechanism that enables population expansion under favourable conditions rather than a mechanism that buffers the effects of adverse conditions.

Mutations in the predicted DNA polymerase subunit POLD3 result in more rapid flowering of Brachypodium distachyon.

The timing of reproduction is a critical developmental decision in the life cycle of many plant species. Fine mapping of a rapid-flowering mutant was done using whole-genome sequence data from bulked DNA from a segregating F2 mapping populations. The causative mutation maps to a gene orthologous with the third subunit of DNA polymerase δ (POLD3), a previously uncharacterized gene in plants. Expression analyses of POLD3 were conducted via real time qPCR to determine when and in what tissues the gene is expressed. To better understand the molecular basis of the rapid-flowering phenotype, transcriptomic analyses were conducted in the mutant vs wild-type. Consistent with the rapid-flowering mutant phenotype, a range of genes involved in floral induction and flower development are upregulated in the mutant. Our results provide the first characterization of the developmental and gene expression phenotypes that result from a lesion in POLD3 in plants.

Incorporating fish habitat requirements of the complete life cycle into ecological flow regime estimation of rivers

AbstractMaintenance of ecological flow regime for aquatic biota is essential to river ecosystem health. To estimate ecological flow, habitat simulation methods have been widely applied because of their combination of hydrological regime and species hydraulic preference. However, few methods are available to provide a flow regime that varies over time due to time‐specific habitat requirements from different target species or from one target species at its different life stages. This paper described a novel approach for evaluating the ecological flow regime that was a time series of discharge considering different life stages of target species. First, an ecohydraulic model that combined multivariable habitat suitability curve of target species with a hydraulic module was developed to establish the relationship between habitat status and hydrological conditions. Then, the habitat connectivity index was adopted to assess the spatial patterns of habitat patches. Finally, the ecological flow regime considering the complete life cycle of target species was derived. The developed approach was applied to the middle reach of Huaihe River, where the flow is highly regulated by dams and sluices. The Chinese bream (Parabramis pekinensis) was chosen as the target species for ecological flow calculation. The ecological flow regime in the Lutaizi was provided for the river management. The study provided a promising method to support ecological friendly operations of hydraulic structures for river ecosystem restoration and management.

Morphology and life cycle of a new species of Psilocladus Blanchard, 1846 (Coleoptera, Lampyridae, Psilocladinae), the first known bromeliad-inhabiting firefly

Fireflies (Coleoptera: Lampyridae) are soft-bodied beetles usually associated with mesic and hydric habitats. As such, terrestrial firefly larvae are commonly found in marshy environments and stream banks, while aquatic larvae might dwell in ponds, streams, mangroves, and even brackish water. Larval biology is especially important in fireflies, as the majority of species are extremely semelparous – that is, adults rely on resources gathered during larval stages. Despite their crucial relevance in firefly biology, larvae of only near 1% firefly species have been studied, and the majority of species remain known only from adult stages. That is especially true in the Neotropical region, where they are most diverse. Here, we describe Psilocladus costae sp. nov. after the study of adults and immature stages, the latter reported for the first time for the monotypic subfamily Psilocladinae McDermott, 1964. Interestingly, adults were first obtained by rearing the larvae, the former usually fly fairly high (ca. 10 m) and are therefore seldom collected at ground level by conventional methods (e.g., active search, Malaise traps). The new species is found in the Brazilian Atlantic Rainforest, inhabiting canopy bromeliads, an unprecedented habit for fireflies.

Characterisation of sphaeractinomyxon types (Cnidaria: Myxozoa) from marine and freshwater oligochaetes in a Portuguese estuary, with the demise of the endocapsa collective group.

Six types of sphaeractinomyxon are reported from the coelomic cavity of oligochaetes collected from the Minho River estuary in northern Portugal. Four new types are morphologically and molecularly described from freshwater species belonging to the genera Psammoryctides Hrabě and Potamothrix Vejdovský et Mrázek in the upper estuary, thus significantly increasing the number of known freshwater sphaeractinomyxon. In the lower estuary, sphaeractinomyxon types 8 and 10 of Rangel et al. (2016) are recorded infecting the marine oligochaete Tubificoides pseudogaster (Dahl). A single specimen of T. pseudogaster further displayed infection by one of the four new types found in the upper estuary, suggesting the involvement of sphaeractinomyxon in the life cycles of myxosporean species that infect migratory fish hosts. The acquisition of these second hosts is proposed to have allowed the myxosporean counterparts of sphaeractinomyxon to cross environmental barriers and conquer new habitats. Phylogenetic analyses of the SSU rRNA gene reveal the four new types clustering within the monophyletic clade of mugiliform-infecting myxobolids, strengthening the previously proposed involvement of the sphaeractinomyxon collective group in the life cycles of this specific group of myxosporeans. Endocapsa types also cluster within the latter clade, having actinospores that differ from those of sphaeractinomyxon only in the presence of valvular swellings that do not change when in contact with water. In this study, however, one type was found displaying actinospores with and without valvular swellings in the same oligochaete specimen. This overlap in actinospore morphology is given as grounds for the demise of the endocapsa collective group.

Biology, ecology and behavior of the acoupa weakfish Cynoscion acoupa (Lacepède, 1801) according to the local knowledge of fishermen in the northern coast of Brazil

Local ecological knowledge (LEK) of fishers and other actors involved in the fishery can be provide information on the life cycle of fish species they harvest, help defining low-cost sampling projects, new biological hypotheses, management activities and policy measures. This study focuses on fishers’ LEK on diet, feeding, spawning grounds, reproductive size, exploited sizes and perceived changes in abundance over the years of the acoupa weakfish (Cynoscion acoupa), a commercially important marine species. Results from interviews with 240 actors (fishers, captains and boat owners) involved in C. acoupa fisheries in eight municipalities in the northern coast of Brazil indicated that: (a) C. acoupa feeds in areas with rocky bottoms down to the depth of 30 m, eating mainly fish, particularly another weakfish (Macrodon ancylodon) and sardines (Engraulidae); (b) this fish spawns in rocky and non-estuarine habitats; (c) the spawning period mentioned by fishers coincided with the harvest period, but was in disagreement with published scientific information; (d) the median minimum length of individuals of C. acoupa carrying eggs according to interviews was of 70 cm, which was smaller than the length reported in biological studies, possible due to the selectiveness of fishing; (e) there is an overall perception of a decrease in the abundance of C. acoupa among the interviewed fishers, which is compatible with studies on stock exploitation of this species. The current dearth of financial and human resources available for scientific research underlines the importance of making use of LEK to improve fishery policy and management.

Leaf phenology amplitude derived from MODIS NDVI and EVI: Maps of leaf phenology synchrony for Meso‐ and South America

AbstractThe leaf phenology (i.e. the seasonality of leaf amount and leaf demography) of ecosystems can be characterized through the use of Earth observation data using a variety of different approaches. The most common approach is to derive time series of vegetation indices (VIs) which are related to the temporal evolution of FPAR, LAI and GPP or alternatively used to derive phenology metrics that quantify the growing season. The product presented here shows a map of average ‘amplitude’ (i.e. maximum minus minimum) of annual cycles observed in MODIS‐derived NDVI and EVI from 2000 to 2013 for Meso‐ and South America. It is a robust determination of the amplitude of annual cycles of vegetation greenness derived from a Lomb–Scargle spectral analysis of unevenly spaced data. VI time series pre‐processing was used to eliminate measurement outliers, and the outputs of the spectral analysis were screened for statistically significant annual signals. Amplitude maps provide an indication of net ecosystem phenology since the satellite observations integrate the greenness variations across the plant individuals within each pixel. The average amplitude values can be interpreted as indicating the degree to which the leaf life cycles of individual plants and species are synchronized. Areas without statistically significant annual variations in greenness may still consist of individuals that show a well‐defined annual leaf phenology. In such cases, the timing of the phenology events will vary strongly within the year between individuals. Alternatively, such areas may consist mainly of plants with leaf turnover strategies that maintain a constant canopy of leaves of different ages. Comparison with in situ observations confirms our interpretation of the average amplitude measure. VI amplitude interpreted as leaf life cycle synchrony can support model evaluation by informing on the likely leaf turn over rates and seasonal variation in ecosystem leaf age distribution.

Potential impacts of land use/cover and climate changes on ecologically relevant flows

This study explored the sensitivity of ecologically relevant flows to individual and combined impacts of climate and land use/cover (LULC) change as well as to their synergistic impacts (combined effect minus sum of individual effects) in a rapidly urbanizing watershed in Alabama, USA. The Soil and Water Assessment Tool (SWAT) was first calibrated (1988–1993) and validated (2008–2013) at daily time scale for streamflow. Then, bias-corrected and downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) climate data from 2035 to 2060 with eleven climate models under two different representative concentration pathways (RCP 2.6 and RCP 8.5) were fed into SWAT to quantify the effects of future climate. Watershed LULC change was represented in SWAT via a future projected dataset developed by the United States Geological Survey (USGS). Past, present, and future potential streamflow responses to LULC and climate changes were analyzed for various ecologically relevant flow parameters. A total of 38 key flow parameters known to have significant impacts on aquatic flora and fauna were examined including high, low, and median flows, as well as flashiness. Increased summer temperature and decreased fall precipitation are expected in the study region accompanied by rapid urbanization. Climate change is expected to increase maximum monthly streamflows, especially in June-September potentially altering habitat availability for aquatic organisms. When climate change was combined with LULC change, more frequent drought and flood events are expected, which may negatively affect many fish species. Significant shifts in the timing of annual extreme streamflow conditions were also predicted in the future, which may adversely impact the life cycle of various aquatic species.

New data on life cycles for three species of Fellodistomidae (Digenea) in the White Sea.

Few digeneans of the family Fellodistomidae are known from the Russian Arctic seas. The taxonomic status of these species, their life cycles and host range raised recurrent questions, some of which remain unanswered. To revise the species composition and life cycles of fellodistomids in the White Sea, we searched for them in several known and suspected hosts: wolffish, flatfishes (definitive), gastropods of the family Buccinidae (second intermediate) and protobranch bivalves (first intermediate). Species identification was based both on morphology and 28S ribosomal RNA gene sequences. We found Fellodistomum agnotum in the White Sea for the first time. Buccinum undatum was proved to be intermediate host of both F. agnotum and Fellodistomum fellis, and metacercariae of F. fellis were registered from two more buccinid species: Buccinum scalariforme and Neptunea despecta. We also found metacercariae of F. agnotum and F. fellis producing eggs in the second intermediate host. Two fellodistomids were found in protobranch bivalves: sporocysts and cercariae of Steringophorus furciger in Nuculana pernula, and sporocysts with large furcocercous cercariae in Ennucula tenuis. The latter were identified as F. agnotum by molecular analysis; thus, the entire life cycle of this species was reconstructed.

Cultivation of early life history stages of Porphyra dioica from the British Isles

Bladed Bangiales of the genus Porphyra/Pyropia are highly valuable red algae and extensively farmed in South East Asia. Interest is rising in cultivating species local to the North East Atlantic but the control of the heteromorphic life cycle of native species remains difficult as previous studies reported high inter- and intraspecific variability in required cultivation conditions. Here, working with Porphyra dioica from a UK source population, we conducted a series of experiments investigating the influence of substrate, temperature, photoperiod and light intensity on the development of early life history stages (conchocelis (filamentous sporophyte) and young thalli (gametophyte)). Special focus was the influence of temperature and photoperiod on mature conchocelis to induce a conchospore mass release—the current bottleneck of European Porphyra cultivation. Sporophytes grew largest on an oyster shell substrate and under long day conditions at 18 °C. A decrease in temperature from 18 to 9 °C initiated a mass conchospore release (498 ± 146 spores mL−1) from a P. dioica conchocelis culture grown in suspension. Released conchospores germinated into small thalli on nylon ropes, with best growth (7.2 ± 0.9% day−1) at low temperatures of 9 °C. Conchospore germination increased with decreasing light intensity but germination success was generally very low (< 5%), indicating the cultivation protocol needs further improvement. Our results reflect the adaptation of P. diocia to seasonal environmental conditions in temperate regions and the importance of these conditions for the successful cultivation. We are the first to describe a mass conchospore release for P. diocia growing in suspension which has important implications for commercial production.

Discriminating Natal Source Populations of a Temperate Marine Fish Using Larval Otolith Chemistry

The life cycles of many marine species depend on a dispersive larval stage that connects spatially segregated populations. However, quantifying larval movement among populations remains one of the greatest challenges in marine ecology. Such movement determines whether a population is essentially a self-recruiting stock, or if it forms part of a larger meta-population where recruits originate from multiple sources. Previous research has struggled to differentiate between such stock structure models for King George whiting (Sillaginodes punctatus; Perciformes) in southern Australia, largely due to difficulties in identifying the source populations of dispersing larvae. In this study, pelagic larvae were collected throughout the only recognized spawning area in South Australia in 2017 and 2018. First, we identified that the distribution of larvae was broadly divisible into two groups – those in southern Spencer Gulf and those in Investigator Strait. Then, the incremental structure and elemental composition of otoliths of larvae from the two regions were compared to determine if they had originated from a common source population. There were no spatial differences in the sizes (3.0-5.0 mm SL), ages (5-21 d), hatch dates (7-24 April) or average growth rates (0.09-0.21 mm d-1) of larvae. However, multi-elemental (Li, Mg, Mn, Sr and Ba) otolith signatures differed significantly between the two regions, primarily driven by differences in concentrations of Li and Ba. Although otolith signatures were year-specific, larvae were assigned to their region of capture with 70-82% accuracy. Larvae in each region hatched at the same time yet had significantly different otolith chemistry, providing strong evidence that those in southern Spencer Gulf and Investigator Strait originated from spatially segregated water masses. This study has demonstrated the ability of otolith chemistry to discriminate source populations of pelagic larvae in a fully marine environment, which provides a basis to quantify larval movement between fish populations.

Instar Determination of Blaptostethus pallescens (Hemiptera: Anthocoridae) Using Artificial Neural Networks

Abstract Blaptostethus pallescens Poppius is an important predator of vegetable pests in tropical regions. The correct identification of the stages of the life cycle of predatory species is crucial, since different stages may present different rates of pest consumption. Artificial neural networks (ANNs) are computational tools with a structure based on the human brain. With applications in several fields, ANNs have been applied in pest management for identification of pest species, spatial distribution modeling, and insect forecasting. The objective of this study was to apply ANNs as a method for the instar determination of B. pallescens using three morphometric measures (head width, body width, and body length). Cluster analysis was performed to categorize the insects in instars according to the morphometric variables. Subsequently, the ANNs were trained for instar determination using the morphometric measures as input variables. The ANNs tested (with 2, 4, 6, 8, 10, and 12 hidden neurons) provided proper data fitting (R2 &amp;gt; 98%). However, due to the parsimony principle, the network with hidden layer size 6 was selected. This study shows the successful application of ANNs in the instar determination of B. pallescens, which would not be possible using classical methods.

High genetic connectivity among pink shrimp Farfantepenaeus paulensis (Pérez-Farfante, 1967) groups along the south-southeastern coast of Brazil

The pink shrimp Farfantepenaeus paulensis is one of the most important fishing resources along the south-southeast coast of Brazil. Its fishing zone includes two main reproductive stocks, located at the coasts of Santa Catarina and São Paulo states. The species life cycle includes an offshore reproductive stage and juvenile recruitment to estuarine areas; therefore, adults are caught in oceanic areas by industrial fisheries and juveniles in estuarine areas by artisanal fisheries. The unrestricted growth of the industrial fleet, along with the increase of artisanal fishing in estuarine areas and the low effectiveness of fishery legislation, led to a collapse of the pink shrimp fishery in the late 1990s. The present work aimed to assess the population genetics of the pink shrimp F. paulensis throughout its main distribution in the Southwestern Atlantic (SWA), to verify whether different fishing stocks also represent different genetic stocks. Based on the evaluation of the mtDNA control region (D-loop), we detected high connectivity and absence of genetic structure among F. paulensis groups in the SWA. Fixation indexes, Analysis of Molecular Variance and a haplotype network also showed no significant genetic differences, with individuals sharing haplotypes among more than one region. Mismatch analysis showed unimodal distributions for all the sampled populations with high haplotype diversity and low nucleotide diversity, showing a pattern of recent demographic expansion, which was corroborated by the Tajima's D and Fu's Fs neutrality tests. Estimates of migration rates indicated high gene flow, with a large number of migrants exchanged between regions. All obtained results are consistent with a panmitic population of F. paulensis. This scenario is a result of a complex interaction of several factors, from the influence of currents on larval dispersal to the effect of overfishing. The knowledge on the diversity and genetic structure of F. paulensis is a fundamental part of the scientific basis necessary for decision makers to elaborate adequate management strategies for pink shrimp stocks.

Effects of starvation and refeeding cycles on spermatogenesis and sex steroids in the Nile tilapia Oreochromis niloticus

Food restriction is part of the life cycle of many fish species; however, nutritional deficiency may negatively influence gametogenesis and gonadal maturation. The aim of this study was to evaluate the effects of food restriction on the spermatogenesis of Nile tilapia. For this, adult males were submitted to starvation and refeeding cycles (alternating periods of starvation and feeding) for 7, 14, 21, and 28 days. After 7 days of starvation, glycaemic and lipid levels were significantly reduced, followed by reduction of plasma testosterone (T) and 11-ketotestosterone (11-KT). In addition, reduced proliferation of spermatogonia and increased apoptosis of spermatocytes, spermatids, and spermatozoa was observed in starvation groups. In the refeeding groups, the sex steroids and the proportion of germ cells had no significant alterations compared to the control group, except for spermatozoa. In this sense, the present study suggests that starvation after 7 days progressively reduces T and 11-TK, resulting in damage to the production of spermatogenic cells, while refeeding may delay spermatogenesis but does not lead to testicular impairment.

Bioenergetics of parental investment in two polychaete species with contrasting reproductive strategies: The planktotrophicBoccardia chilensisand the poecilogonicBoccardia wellingtonensis(Spionidae)

AbstractThe level of parental investment for larval nutrition may determine the life cycle in marine invertebrate species laying egg masses or capsules, where the food available for enclosed individuals would determine time and developmental stage of hatching. Most species show a unique type of larval development. However, few species are poecilogonous and combine more than one development type. Poecilogony, although scarcely studied, allows comparing different patterns of parental reproductive investment, without the phylogenetic effect of the species ancestral modes of development (phylogenetic inertia), to help to understand the factors determining life strategy evolution in marine invertebrates. The poecilogonous polychaete wormBoccardia wellingtonensisencapsulates and incubates its offspring, which then hatches as either planktotrophic larvae or benthic juveniles; whileBoccardia chilensisshows a non‐poecilogonous reproductive type, producing only planktotrophic larvae. In this work, we estimated the bioenergetic and biochemical composition of brooding and non‐brooding females ofB. wellingtonensisandB. chilensisto compare the costs of reproduction in these two species. Results showed that glucose, protein, lipid, and energy content were significantly higher in non‐brooding than in brooding females ofB. wellingtonensis; but also contained significantly more glucose, protein, and lipid than females ofB. chilensis(in absolute and relative dry weight values). The poecilogonous species showed higher energy content previous to laying offspring. Our results support the idea that the evolution of a certain reproductive and life history traits in marine invertebrates is related to adaptations in the female's reproductive investment.