Non-ovigerous Females Research Articles

Spatial distribution and fecundity of the cinnamon shrimp, Macrobrachium acanthurus (Wiegmann, 1836) (Crustacea: Decapoda: Palaemonidae) from Jequitinhonha River (BA), Brazil

ABSTRACT Macrobrachium acanthurus is an amphidromous palaemonid shrimp exploited by artisanal fishing in Brazil that presents limited published information on its population biology. Therefore, this study aimed to assess the spatial distribution and fecundity of M. acanthurus in the Jequitinhonha River (BA). Collections occurred at four points in the river downstream of the Itapebi Hydroelectric Powerplant (P1–P4). The abundance and size of the demographic categories analysed (male morphotypes, non-ovigerous females, and ovigerous females) and fecundity were compared among points. We also examined the relationship between female body size and fecundity. A total of 938 individuals were collected during the sampling period. The highest abundances were observed downstream (P3 and P4). The sizes of males and ovigerous females were greater at points farthest upstream. Three male morphotypes were identified, and their proportions varied among points. Fecundity was higher upstream, and there was a positive correlation between female size and number of eggs. All population parameters indicate a longitudinal gradient towards the estuary, with strong evidence of amphidromy. This is the first study with a polymorphic species to consider morphotypes as a population structure component. The results represent an important contribution to a better understanding of the amphidromous life cycle of palaemonid shrimp.

Estructura y dinámica de población de Tigriopus californicus (Copé´´poda, harpacticoida)

From January 1976 to July 1979, samples of a population of the copepod Tigrlopus californicus were collected at monthly intervals on lower supralittoral level tide pools at Península Foca, ría Deseado (Santa Cruz).
 Density and samples composition in males, ovigerous and nonovigerous females, coupled individuals and juveniles were determined. Females usually were significantly more abundant than males. The seasonal density changes are considered with respect to the physical environment. Copepods were present throughout the year but abundance in summer is several orders of magnitude greater than in winter, through a rapid autumn decline. A large density increase in spring complete the annual cycle. The frequency of this maxima and mínima appeared to be periodic in time during the sampling years, in annualy cycles. Natural mortality and instantaneous rates of population increase were estimated,and the last compared with the species reproductive potential (computed "in vitro", previously published). The periodic density fluctuation is considered with respect to the seasonal changes in poblational structure through cyclical modifications of the instantaneous rates of population increase.

Swimming behavior and energy metabolism of the calanoid copepod invader Sinodiaptomus sarsi

The appearance of invasive species threatens the integrity of aquatic ecosystems. Much is known about dispersal and introduction mechanisms while little is known on the biological properties of invasive species, such as behavior and energy efficiency, allowing them to successfully colonize new environments and compete with native species. This study examines the functional features of the Asian invasive copepod Sinodiaptomus sarsi (Rylov, 1923) that has invaded Europe since 2016. We focused on the energy metabolism and kinematic parameters of the main swimming types (i.e., gliding, hovering, small relocation jumps, and the escape reaction) of females and males of S. sarsi. Based on the above parameters, the mechanical energy for swimming and the respiration energy needed for movement were calculated. Females and males spend up to 95% of time hovering and slowly gliding at a speed of up to 0.5 cm s−1. During the remaining time, the average swimming speed was 8 cm s−1 by small jumps. In contrast, the average speed was 42 cm s−1 during escape swimming. Non-ovigerous females moved faster than ovigerous females during all relocation swimming types except for upward gliding. While performing small jumps with a frequency of 0.79 Hz, the respiration rate of active non-ovigerous females (0.32 ± 0.03 µg O2 ind−1 h−1) was 2.1 times higher than that of anesthetized individuals. The respiration energy associated with movement was 2.6 * 10−3 J h−1, while the total mechanical energy was only 4.2% of this value. The low energy cost of feeding along with the high speed of locomotion may explain the success of this Asian invader in European waters.

Examination of female energy dynamics and larval quality in the southern king crab, Lithodes santolla: Annual and interannual variability

The southern king crab, Lithodes santolla, constitutes one of the most important fishery resources in the Beagle Channel. In this study, we considered that Lithodes santolla females showing better physiological conditions may produce larvae with higher survival rates. To determine whether this quality may be useful for the enhancement of natural crab stocks, in the present study, we aimed to evaluate several biochemical parameters considering the size and ovigerous condition of the female parent. Primiparous (<80 mm CL) and multiparous (>80 mm CL) females, as well as ovigerous and non-ovigerous females, were evaluated. The patterns of accumulation or use of several macromolecules (glycogen, lipids and proteins) in different organs and development stages (midgut gland, ovary, eggs, larval stages and first crabs) were also evaluated along two reproductive seasons. The possibility that some females could be producing larvae with high survival was evaluated through the relationship between the female midgut gland and ovarian quality and the larvae. The results obtained indicate that the energy content of L. santolla females is highly variable according to the year, season, and month, and between primiparous and multiparous females. We hypothesized that this variability in the energetic quality is explained by differences in the female's diet: food availability or food quality during ovary maturation. Most of the energy reserves of the ovary are transferred to the offspring. The only female parent-brood connection is through the energy reserves transferred to the eggs 10 months earlier, and we hypothesize that this depends on the previous environmental and female feeding conditions during ovarian development. Moreover, zoea I larvae showed high variability in survival, not influenced by their own energy reserves or by the reserves of the eggs or the ovary. The physiological variables here analyzed did not allow identifying better females that can produce larvae with higher survival.

Diets of Portunus segnis (Forskål, 1775) (Decapoda, Portunidae) from the Persian Gulf, Iran

Abstract The food habits of the blue swimming crab, Portunus segnis (Forskål, 1775) were investigated using specimens collected from trawl catches in the north-east of the Persian Gulf, from June 2018 to May 2019. Feeding habits of 304 adult female crabs, ranging from 2.6 to 8.7 cm in carapace length, were analysed. The stomach content of examined crabs showed to consist of crustaceans, fish, molluscs, unidentifiable material, sea grass and foraminiferans. We realized that the vacuity index did not show significant differences between ovigerous and non-ovigerous females (). Nevertheless, there was a significant difference in the vacuity index between barnacle-carrying crabs — Chelonibia testudinaria — and crabs without barnacles (). There was no significant difference observed in the quantity of the eaten foods between large and medium-sized groups of crabs. But a significant difference was observed between large- and small-sized crabs, and small- and medium-sized crabs. Moreover, significant differences were observed in food items between barnacle-carrying crabs and crabs without barnacles. Also, the percentage of empty stomachs was higher in ovigerous females than in non-ovigerous females.

Population structure and genetic connectivity of the freshwater shrimp Potimirim brasiliana Villalobos, 1959 inhabiting a continental island

ABSTRACT Insular regions present peculiar characteristics, including small populations resulting from prolonged evolutionary isolation. Such conditions make these areas sensitive to anthropogenic changes. By consequence, these areas are interesting for studying genetic and adaptative processes. This study had two main goals: to evaluate the demographic structure (distribution, frequency of individuals in size classes, and sex ratio) and to assess the genetic diversity of a freshwater shrimp population of Potimirim brasiliana on the continental São Sebastião Island. Subsequently, population structure (size, abundance, and sex ratio) and genetic analyses (network haplotype and genetic distance of the mitochondrial marker cytochrome oxidase subunit 1 – COI) were analysed to compare the spatial distribution and connectivity of individuals along separated areas exposed to different conditions of dispersal. Three different areas were defined along the island (sheltered area – SA, exposed area – EA, and south extremity – SE). We found males and females in all areas except SE. The percentage of males was greater in the EA, that of non-ovigerous females was greater in the SE and that of ovigerous females was greater in the SA. Females were larger than males in all areas. No genetic structural difference was found between the studied areas and no genetic differences were detected in relation to the inland population. The strategy developed by P. brasiliana in the areas of the São Sebastião Island involves a differential occupation among the demographic groups in and maintaining connectivity between different and separated areas of the island by larval dispersal.

New host–parasite associations of Cymothoidae (Crustacea, Isopoda) infesting elasmobranch fishes in Tunisian waters

Between 2015 and 2020, 2 092 specimens of cartilaginous fishes (Chondrichthyes: Elasmobranchii) belonging to eight species and five genera were sampled along the Tunisian coast and examined for their cymothoid parasites, Among the eight examined elasmobranch species, only three were infested, Five parasite species were identified: Anilocra physodes, Emetha audouini, Ceratothoa oestroides, C. parallela and Nerocila orbignyi, These parasites presented three maturation stages: ovigerous females of A.physodes and E. audouini, adult non-ovigerous females of N. orbignyi, and juvenile females of C. oestroides and C. parallela, Most of these parasitic isopods were found on a single host species except for the two Ceratothoa species. We report new host-parasite associations, including the presence of A. physodes and E.audouini on smooth-hound Mustelus mustelus, the occurrence of C. oestroides and N. orbignyi on cartilaginous fish species, and the presence of C. parallela on black smooth-hound Mustelus punctulatus and M. mustelus. Parasitological indices and the seasonal variation in prevalence of the collected cymothoids, as well as parasitic species richness, are presented.

Study on Shell Utilization Pattern of Two Sympatric Hermit Crab Species on the Rocky Intertidal Region of Veraval, Gujarat, India

The present study illustrates the shell utilization and resource partitioning of two sympatric hermit crab species Clibanarius rhabdodactylus and Clibanarius ransoni with reference to gastropod shell species (shell shape), shell size and shell availability. Specimens were collected from January to March 2021 and hermit crab weight and shield length were measured. The gender of occupant hermit crab was identified and categorised into male, non-ovigerous female and ovigerous female. Gastropod shells were identified and different morphological parameters like shell length, shell aperture length and width, shell volume and dry weight were measured. The population of C. rhabdodactylus and C. ransoni was female biased with male: female ratio being 1:1.93 and 1:1.25 respectively. Clibanarius rhabdodactylus and C. ransoni were occupying 29 species and 28 species of gastropod shells respectively among which > 75% occupied shells were comprised of Cerithium caeruleum, Lunella coronata, Turbo bruneus, Tenguella granulate and Pollia undosa. Both the Clibanarius species were showing a high overlap in their intertidal distribution as well as gastropod shell use pattern. Cerithium caeruleum was found to occur in high abundance as compared to other gastropod species in the study area which may also influence the shell utilization of hermit crab species. Males and non-ovigerous females of the hermit crab species utilized almost all shell species, while ovigerous females used only a few shell species. Significant relationship was observed between different morphological parameters of the occupant crab species and occupied shells. Shell partitioning was evident between hermit crab sexes as well as reproductive stages on the basis of occupied shells of different species, shapes, and sizes. The present study revealed shell occupation pattern of C. rhabdodactylus and C. ransoni is highly influenced by the diversity, morphology and availability of gastropod shells in the study area.

Population structure of the stone crab Xantho poressa (Olivi, 1792) in a human-restricted access area

Some of the elements in the rocky intertidal zone, such as boulders, act as a refuge, mating, feeding and nursery area for marine fauna. In the present study, we analysed the population structure of the intertidal stone crab Xantho poressa in a human-restricted area, between March 2019 and February 2020, comprised of a rocky shore along the SW Atlantic Spanish coast. The study aims to provide information about the size distribution and identify which environmental factors shape the distribution, sex ratio and mating system of the species. The males were significantly larger than the females and no significant difference in size was observed between ovigerous and non-ovigerous females. The sex ratio was biased towards females. Groups constituted by one large male and several females were observed coexisting under a boulder. Other groups of two or more males and various females were also observed during the study. The distribution of the species is mainly determined by the size and weight of the boulder. The complexity of the study area, and the key role of boulders in the distribution of the species, suggests that X. poressa might have a refuge–defence polygynous mating system.

Sexually-manifested variations in pigmentation of Boeckella poppei (Copepoda, Calanoida) from Livingston Island (Maritime Antarctica)

Antarctic environments are exposed to high levels of ultraviolet radiation (UVR) that are often detrimental to their biota. Recent studies suggest that the genus Boeckella (Copepoda, Calanoida) has a high level of plasticity in terms of its reaction to UVR, which enables its wide distribution in various water bodies in Antarctica. Boeckella poppei is common in freshwater habitats of all three main biogeographic regions in Antarctica: sub-Antarctic islands, maritime and continental. We present for the first time a specific photoprotective response in populations of B. poppei from Livingston Island, Maritime Antarctica. In non-ovigerous females and in males, we observed uniform distribution of carotenoids in the body, while these pigments were almost entirely concentrated in the ovisacs of mature females. We consider this as a means of progeny protection from the teratogenic influence of the high level of UVR in Antarctic environments. Unequivocally, such adaptation would facilitate the expansion of B. poppei on the continent through colonisation and survival in shallow freshwater habitats. Given that the Antarctic environment is dynamically changing over the past decades and the accelerated retreat of permanent ice cover is a premise for the formation of shallow ponds, B. poppei could be a suitable indicator for reflecting the ongoing global environmental changes in Antarctica.

Reproductive strategy of yellow squat lobster (Cervimunida johni Porter, 1903): re-evaluating the maturity criteria

ABSTRACT Studying the basic biology of heavily fished marine species is essential to achieving conservation and sustainable exploitation. Yellow squat lobster (Cervimunida johni) is a demersal crustacean with a long fishing history in the Southeast Pacific. However, knowledge of its reproductive biology is still fragmented, and these traits have never been validated at the gonad level. In this context, we assessed the reproductive traits of this species for the first time based on gonadal development using data from a research survey conducted during 2018 off the Chilean coast. A total of 117 and 376 gonads were assessed based on histological and macroscopic analyses, respectively. The functional and effective criteria (a combination of functional and physiological maturity) were used to estimate the maturity ogives. Using a total of 113 females, fecundity (F) and relative fecundity (RF) at length were estimated using the autodiametric method. We determined that females of yellow squat lobster possess group-synchronous ovary development with indeterminate fecundity. Histological analysis revealed that 59% of non-ovigerous females had mature ovaries and were therefore misclassified as immature based on the functional criterion. Similarly, maturity ogives derived from the effective criterion were displaced to smaller sizes and varied significantly from those estimated using the functional criterion (P < 0.05). In addition, the effects of female size on F and RF were significant (P < 0.05). A warning on the use of functional criteria for assessing maturity status is issued, and the importance of adult females on the per capita contribution to population renewal in this crustacean species is discussed .

Amblypygi parthenogenesis, embryonic and post-embryonic development: a case study with the Amazonian species Charinus guto Giupponi and Miranda, 2016 (Amblypygi: Charinidae)

ABSTRACT Parthenogenesis is documented in a few species of Amblypygi, but it is unknown how widespread in the order this reproductive behaviour is, and little has been researched regarding aspects of embryonic and post-embryonic development in the group. Here, we studied the parthenogenetic capacity of an Amazonian whip spider (Charinus guto) evaluating the time of egg and embryonic development and inter-moult period. We also provide a review on embryonic and post-embryonic development in Amblypygi, compiling and analysing data from 43 species in three families. Fifty-two females and 42 juveniles of C. guto were collected in fragments of a secondary forest in Belém (Brazil); specimens were kept in captivity and observed weekly from 2018 to 2020. Nineteen specimens were collected with and 32 without egg sacs. Fourteen of the non-ovigerous females developed eggs in captivity, six of them moulted (i.e. lost stored sperm from previous contacts with males) before developing an egg sac, proving to be parthenogenetic. The mean time between the first day in captivity and moult was 96 days. In both adults and juveniles, a mean of 147 days passed between first day in captivity and first moult, and 125 days for a second moult. After moulting, a mean of 113 days passed for the females to develop an egg sac; the embryonic development took a mean of 59 days. Juveniles left the mother’s abdomen after 10 days of hatching from the egg and the mean number of live free-living protonymphs was five. Other amblypygids, especially charinids, have similar embryonic development and post-embryonic growth and a detailed discussion with all known information for whip spiders is presented. We also demonstrate a positive correlation between clutch size and female size across Amblypygi, in which larger females carry more eggs and have larger offspring regardless of climate and habitat.

Carrying eggs in a semi-terrestrial environment: Physiological responses to water deprivation of mothers and embryos of the tree-climbing crab Aratus pisonii

In semi-terrestrial crustaceans, mothers and the carried embryos form a unit. The ideal conditions for embryonic development place a sustained demand on the mothers' energy budget. A particular challenge for this unit is the transition between terrestrial and aquatic environments. Ecophysiological information on mothers and embryos contributes to the understanding of evolutionary pathways and constraints of terrestrialization in crabs. We evaluated the effects of 6, 12, and 18 h of water deprivation on embryonic development and maternal physiology of the tree-climbing crab Aratus pisonii (H. Milne Edwards, 1837). Specifically, we determined the effect of water deprivation on egg volume, osmolality, and larval survival, as well as on maternal body mass, hemolymph osmolality, and branchial carbonic anhydrase activity (CAA). We hypothesized that longer periods of water deprivation would negatively affect larvae viability, as well as disrupt the physiology of brooding females. Embryonic development, larval survival, and the mother's physiology were only altered after 18 h of water deprivation, possibly due to dehydration and/or the accumulation of metabolic wastes that could not be excreted in the absence of water. Osmolality was higher in females than in their eggs. CAA of the anterior gills was higher in ovigerous than in non-ovigerous females, possibly due to the increase in respiratory demands caused by carrying eggs. Our results confirmed that the gestation period represents a metabolically expensive period for mother crabs and that water deprivation of 18 h was critical for the embryos' survival.

Observations of life history traits of Typton carneus Holthuis, 1951 (Caridea, Palaemonidae): a poorly known sponge-dwelling shrimp

The objective of this study was to investigate some life history traits of the palaemonid shrimp Typton carneus collected from a reef in northeastern Brazil. Samples of the sponges Amphimedon compressa, A. viridis, Desmapsamma anchorata, Dysidea etheria, Haliclona implexiformis and Tedania ignis were analyzed and shrimps were removed from them. A total of 41 individuals were found in Te. ignis, three in H. implexiformis and one in D. etheria; the latter two sponges are new records of sponge hosts for Ty. carneus. Of the specimens associated with Te. ignis, 24 were males, 10 ovigerous females, six non-ovigerous females and one juvenile male. Fecundity varied between 19 to 56 eggs (37 ± 14) per female, and the mean egg volume was 0.033 ± 0.010 mm³. Eleven heterosexual pairs were obtained. Characteristics of the pairs suggest a monogamous mating system for the studied population, such as: the absence of sexual dimorphism in weaponry and body size and presence of paired non-brooding and brooding females carrying eggs in different development stages; and a sex ratio that does not differ from the expected 1:1. However, the lack of size-assortative pairing as well as the low proportion of pairs, compared to solitary individuals, have been observed in polygamous mating systems.

Body condition and energy content of shore crab Carcinus maenas in a temperate coastal system: temporal variability

The body condition of the shore crabCarcinus maenasin a temperate coastal system (western Dutch Wadden Sea) was followed over 14 mo. Fulton’s condition factorK, dry weight condition and the percentage of dry weight were determined as indirect indices, while bomb calorimetry was applied to obtain the energy density and total energy, as direct biochemical measures of condition. General linear models identified sex, size and season as relevant regressors explaining observed variance in crab condition, whereas colour morphotype effect was negligible. The seasonal pattern was consistent with the natural cycling in temperature and expected food availability, but the peak in body condition differed depending on the type of measure used: energy peaked in autumn, while morphometric condition was at its highest in winter, uncovering different latencies in the response of direct and indirect indices. Concordant with higher energy investment in reproduction, body condition and energy content of non-ovigerous females were higher than those of males, and egg-bearing females always had the lowest condition values. Energy content of adult females ranged from 16.37 ± 1.30 (winter 2013) to 19.83 ± 0.54 kJ g-1ash-free dry weight (AFDW) (autumn 2013), attaining 18.77 ± 1.22 kJ g-1AFDW prior to the onset of reproduction in 2012, while maximum energy density of ovigerous females (eggs excluded) was 16.49 ± 0.64 kJ g-1AFDW. Besides low correlation between indirect and direct indices, fluctuations were more pronounced in the energetic data. Therefore, the morphometric measures seem weak surrogates to estimate energy density of these crabs.

Population dynamics of Armases rubripes in southwestern Atlantic salt marshes: seasonality, abiotic influence and reproductive biology

The knowledge about reproductive biology and influence of seasonality and abiotic factors over crabs improves the understanding of their role in salt marsh ecosystems. Focusing on Armases rubripes, we analyzed of 2,206 individuals in terms of abundance, sex ratio, morphometry and egg count, monthly sampled along two years. Through Generalized Linear Mixed-effects Models we found a continuous presence of A. rubripes at Patos Lagoon Estuary (PLE), Brazil, with seasonal peaks of males and non-ovigerous females mostly during cold autumn–winter. The opposite pattern was found to ovigerous females, when they were prevalent during warm spring–summer and early autumn. The overall sex ratio indicated a predominance of males over females (1.2♂: 1♀), but male peaks during summer months (mainly ≥2♂: 1♀) could be due the migration of females to spawning grounds. The first maturation size based on the carapace width (CW) was estimated at 7.9 mm for males and 7.0 mm for females. The highest gain in fecundity (79.2%) occurred in the width class immediately after the transitional maturation stage (10.1–11.0 mm CW), suggesting that size influences in the ability of ovigerous females in the transitional maturation stage to reach the maximum reproductive outputs. The fecundity of 2,880 (± 1,964) eggs shown a low fecundity for A. rubripes along the sampled region. Our results bring a new information about the occurrence and reproductive biology of this species in salt marshes from medium latitudes, opening the discussion about our findings.

Unveiling the dynamics of the spider crab Libinia ferreirae, through reproductive and population characteristics on the south-eastern coast of Brazil

AbstractWe investigated the population dynamics of the spider crab Libinia ferreirae, focusing on the frequency distribution of individuals in size classes, sex ratio and the action of environmental variables (temperature, salinity, texture and organic matter content in the sediment) on reproduction and recruitment. Monthly collections were made in the Ubatuba region from January 1998 to December 2000. A total of 222 individuals were collected, including 123 juveniles (males and females), 43 adult males, 25 non-ovigerous adult females and 31 ovigerous females. Unlike most adult brachyurans, there was no significant size difference between sexes, and sexual dimorphism seems to be a varying characteristic for this crab genus. The reproductive period and recruitment were continuous with peaks that could be related to water mass dynamics and higher food availability in the Ubatuba region. In addition, our results increase knowledge about part of the life cycle of L. ferreirae, which could be useful for comparative studies.

Population Structure and Reproductive Biology of the Endangered Crab Deiratonotus japonicus (Brachyura, Camptandriidae) Surveyed for Nine Years in the Kita River, Japan

Deiratonotus japonicus (D. japonicus) is known as a near-threatened species, because of the changing conditions of its habitat. This species resides in isolated locations and in upstream, brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. In this study, we investigated the population structure and reproductive biology of D. japonicus in the Kita River, Japan. The distribution, sex ratio, breeding season, and fecundity were assessed at bimonthly intervals during spring low-tide periods from May 2001 to November 2008 and from November 2014 to January 2016 for approximately nine years. A total of 3525 crabs were collected during the sampling period: 1806 (51.2%) males, 1240 (35.2%) non-ovigerous females, and 479 (13.6%) ovigerous females. The overall sex ratio (1:0.95) did not differ significantly from the expected 1:1 ratio. The mean maximum density was 26.1 and 36.5 indiv./m2 for the first and second sampling periods, respectively, in the sampling station 5.2 km from the Kita River mouth, and all individuals were typically found approximately 4.4–6.8 km (13.2 ± 7.8 indiv./m2) from the Kita River mouth. Carapace width (CW) ranged from 2.6 to 13.5 mm in males and from 2.8 to 13.4 mm in females and was significantly different between the two sexes (p &lt; 0.05). Ovigerous females were found almost throughout the entire sampling period, with breeding peaks between July and September. The smallest ovigerous female had a CW of 3.9 mm. The seasonal frequency distribution suggested the continuous recruitment of young juveniles (CW &lt; 3.9 mm) throughout the year, with peaks from September to November. The mean fecundity was 1008.3 ± 183.1 (8.3 ± 1.6 mm) eggs. Egg number in relation to CW was calculated by the formula egg number (EN) = 110.36 × CW + 90.96 (R2 = 0.948, n = 41, p &lt; 0.0001). Regression analysis showed that fecundity was closely associated with female CW. Our results indicate that the performance of reproductive biology depends not only on continuous breeding but also on recruitment throughout the year in our study area.

Eurytemora affinis (Poppe, 1880) (Copepoda, Calanoida) in the Gulf of Riga, Baltic Sea — elemental composition and diurnal vertical migration

Abstract The present paper reports the results of two surveys conducted in the Gulf of Riga (Baltic Sea) during 1997. Elemental composition (carbon and nitrogen) and diurnal vertical migration (DVM) throughout development of the calanoid copepod Eurytemora affinis (Poppe, 1880) were studied. This is a species with a high genetic and morphological heterogeneity, inhabiting a seasonally stratified, herring (Clupea harengus Linnaeus, 1758) rich ecosystem. The DVM of copepods is a widespread advantageous behaviour, although with several trade-offs. At the expense of time spent in the food-richer surface layer, copepods avoid visual predators (planktivorous fish) by descending to greater depths, thereby decreasing their mortality. Being a part of the food web, copepods themselves serve as a source of nutrients with specific elemental contents. In the present study, we observed differences both in DVM and elemental content between the developmental stages of the studied species. The majority (57-89%) of nauplii and 1st to 3rd copepodids were found near the thermocline during daytime, whereas at night they were detected above the thermocline. The 5th stage copepodids and adults displayed evident nocturnal ascent, when most (&gt;90%) individuals moved above 15 m depth. During daytime, they tended to disperse throughout the water column. Carbon (C%) and nitrogen (N%) in dry weight of E. affinis increased with ontogenetic development, reaching the highest values in 4th to 5th copepodids and adults. Adult males showed higher values of C% and N%, as well as an increased C : N molar ratio, compared to adult non-ovigerous females. The amount of time spent at the food-richer surface layer appeared to be related to N% in E. affinis.

First known occurrence of the alpheid shrimps Leptalpheus forceps Williams, 1965and L. marginalis Anker, 2011 (Decapoda: Caridea) in the state of Pará, Amazonregion, Brazil.

In the present study, we report for the first time the occurrence of the alpheid shrimps Leptalpheus forceps Williams, 1965 and Leptalpheus marginalis Anker, 2011 in the state of Pará, in northern Brazil. Both Leptalpheus species (males, non-ovigerous females, and females carrying eggs) were collected from the burrows of the callichirid "ghost" shrimp, Lepidophthalmus siriboia Felder Rodrigues, 1993, in a muddy-sandy intertidal zone of the Ajuruteua Peninsula, in the Bragança region. These records update the known geographical distribution of the two species, with L. forceps extending its Brazilian occurrence from the state of Bahia to state of Pará, and L. marginalis which was exclusively found on the Caribbean coast of Colombia is now recorded in Brazil.