Along‐ and across‐shore components of the spatial distribution of the clam Tivela mactroides (Born, 1778) (Bivalvia,Veneridae)

Beach clam fisheries often provide an alternate income for traditional fishermen, but this activity is highly vulnerable to urbanization of coastal areas. Tivela mactroides is a beach clam commonly harvested in the Caribbean (Venezuela) and on the south‐eastern Brazilian coast. Only localized records on its spatial structure in size and abundance are available to support management of this clam. The present study showed that the spatial distribution in abundance and size of T. mactroides in Caraguatatuba Bay, state of São Paulo, Brazil, has both along‐ and across‐shore (intertidal and subtidal) components. The nature of this distribution should be taken into account in the design of further population or monitoring studies concerning this species. Clam density varied along‐shore, with a tendency towards higher numbers of individuals in the stations near the northern side of river mouths of this bay. Lower densities were related to the occurrence of sea‐stars and sand‐dollars. The intertidal and subtidal across‐shore distribution of clam abundance and size varied between and within areas (southern and northern). The individuals from the southern area were concentrated at intermediate tidal levels (0.2–0.6 m in relation to mean low water), whereas in the northern area the clams were more homogeneously distributed. The uppermost limit of their distribution was 0.8 m (southern) and 0.4 m (northern), and an upwards tendency towards increased size was more evident in the northern area. In the subtidal, abundance and individual size tended to increase from the deepest (4.5 m) to the shallowest (0.5 m) levels only in the southern area. Individual clams in the northern area tended to be smaller and more abundant than in the southern area. The species had an ontogenic distribution: small‐sized individuals were recorded only in the subtidal. Possible causes for these patterns and for the differences between areas (human exploitation, organic pollution, beach morphodynamics, differential recruitment, and adult–larvae interactions) are discussed, and specific studies are suggested to evaluate formally the proposed hypotheses.     

Spatial distribution of the ghost crab Ocypode quadrata in low‐energy tide‐dominated sandy beaches

The spatial distribution of the ghost crab Ocypode quadrata (Crustacea, Brachyura) was described in five low‐energy tide‐dominated sandy beaches in São Sebastião Channel (Grande, Zimbro, Pitangueiras, Cabelo Gordo, and Segredo). On each beach, the zonation study was performed on five random 1?m wide transects sampled from the water line to the vegetation. In general, individuals occurred above 1?m in height in relation to mean low water (MLW) and peaked between 1.5 and 2.0?m. The sandy beaches were then divided into three 1?m wide strips (tidal levels) parallel to the water line and equivalent to medium intertidal, upper intertidal, and subterrestrial fringe to test the effect of beach and tidal level on the abundance and size of O. quadrata. These strips were sampled as a whole using adjacent 1 m² squares. A previous evaluation showed a positive significant relationship between carapace length and burrow diameter, thus supporting crab size estimates from burrow openings. The smallest individuals occurred mainly in the medium intertidal, but were also recorded in the subterrestrial fringe, which was occupied mainly by large‐sized individuals. In general, the individuals were randomly dispersed within the strips and concentrated in the upper intertidal zone on all the sandy beaches. The density of O. quadrata varied among beaches, with a tendency to lower values on areas with very fine and poorly or moderately sorted sediments and on that most used for recreational activities (Grande). Burrow size also varied among beaches, with a tendency of smaller burrows in areas with coarser sand grains and higher tourism. These results indicate that the effect of human impact on density and size of O. quadrata may be confounded by the high environmental heterogeneity of the studied system, which may make it difficult to utilize this species as an indicator of the conservation status of low‐energy tide‐dominated sandy beaches.     

Population structure of Tachypleus tridentatus (Chelicerata: Merostomata) at a nursery beach in Puerto Princesa City,Palawan, Philippines

This study aimed to determine the population structure of juvenile Tachypleus tridentatus, one of two species of horseshoe crabs found in Palawan, at Aventura Beach, Puerto Princesa City, Palawan. Surveys to assess the population in terms of size, density, size‐frequency, age structure, sex ratio and distribution were conducted from June to October 2002. The habitat was mapped and physical/chemical parameters taken to further describe it. The position of population members was plotted on the map. Individuals were measured, marked, sexed and released. Prosoma width was measured for living individuals and exuviae. Postembryonic stages were identified based on histograms with different interval size. The normal distribution of the animals per instar stage was tested with the Kolmogorov–Smirnov test. After the 5‐month survey a total of 125 juveniles was recorded and 40% of them were recaptured. Population size was estimated to be 150 individuals. Seven postembryonic stages were identified based on their prosoma width. Male: female ratio was 1:1.8 and the age of the first five postembryonic stages ranged from 5.4 months to 17.6 months. The population density was 1.47 individuals per?100?m². The majority of the animals of all postembryonic stages were found between 0 and 50?m from the mean high tide level. Further studies on the population structure of T. tridentatus with regards to the adult population are seen as a necessity.     

Life cycle and population structure of the terrestrial isopod Hemilepistus klugii (Brandt, 1833) (Isopoda: Oniscidea) in Iran

The life cycle and population structure of Hemilepistus klugii were studied in a population in Varamin, Iran. The population was sampled monthly (or fortnightly during the breeding season) from February 2008 to June 2009 and a total of 7015 individuals, comprising 1069 males, 1079 females and 4867 juveniles, were collected. As in other Hemilepistus species, five distinct phenophases, namely pair formation, gestation, hatching, growth and stationary, were recorded during the life cycle of H. klugii. The overall sex ratio was 1 : 1 but varied over time. Ovigerous females were observed only in April, indicating a seasonal and very short breeding period. With a short lifespan after breeding, females demonstrated true semelparity. The mean cephalothorax width for ovigerous/post-ovigerous females was higher in 2008 than in 2009. These females attained the largest size in the population throughout the year. The number of eggs per female ranged from 28 to 147 (mean ± SE, 78 ± 1.8). There was a positive correlation between female size and fecundity. Recruitment occurred in late April and resulted in the highest population density in this month, whereas the lowest densities were observed during November to January. Despite a high percentage of ovigerous females carrying undeveloped eggs (72.3%), intramarsupial mortality was low (3.5%).     

Biology of a tropical intertidal population of Cerithium atratum (Born, 1778) (Mollusca,Gastropoda)

The spatial distribution, population structure and secondary production of the gastropod Cerithium atratum were studied in the intertidal region of Engenho d'Água Beach in São Sebastião Channel on the northern coast of the state of São Paulo, Brazil, from May 1998 to April 1999. Twenty monthly samples were taken using a 0.25×0.25?m quadrat in each of two areas. Individuals showed a clustered dispersion pattern in both areas throughout the sampling period. Abundance and mean shell size were related to period of the year and to intertidal level, although no consistent pattern could be described when comparing the two sampling areas due to significant interaction between time and locality. Migratory events were evidenced by marked year-round variations in the frequency of individuals in the largest size classes. Thus, the size structure of this population could not be explained by recruitment and growth alone. Almost 90% of the intertidal population was represented by small individuals that recruited at the beginning of the sampling period (May to August 1998). The intertidal population was composed of annual cohorts formed by individuals recruited in different years. Each annual cohort could be divided into sub-cohorts with closely spaced recruitment periods in the same breeding season. The growth and annual P/B ¯ ratio (where P is the annual somatic production and B ¯ is the mean annual biomass) was estimated for the first year of life of recruits from 1998 occupying the intertidal region. Individuals may have an increment of up to 15?mm in shell length during the first year of life, but the growth was more pronounced in summer months. The high value of P/B ¯ (3.902) was a consequence of the dominance of small-sized individuals, which have a higher weight-specific increment than large-sized ones.     

A snapshot of a high density seahorse population in a tropical rocky reef

Seahorses are fishes that suffer high trading pressure in the international market. Three species have been recorded in Brazil, Hippocampus reidi, Hippocampus erectus and Hippocampus patagonicus, already classified as threatened or data deficient. Guaíba Island is an ecologically relevant site due to its position between two bays in Rio de Janeiro state. The present study aimed to survey the seahorse population of Guaíba Island, verifying several population structure parameters. Eight diving sites were selected around the island. Only the longsnout seahorse H. reidi was recorded. The population showed the largest density ever recorded in the world for the species. Sex ratio was 1:1 and seahorses were reproductively active. We observed three juveniles. The mean length recorded was 8.9 ± 1.64 cm. The population structure was similar to others populations studied throughout the Brazilian coast.     

Another migid in the wall: natural history of the endemic and rare spider Calathotarsus simoni (Mygalomorphae: Migidae) from a hill slope in central Argentina

A population of Calathotarsus simoni Schiapelli and Gerschman (1975) was discovered on a hillside in the Ventania system, Argentina. Our objectives were to quantify burrow density, record burrow morphology and door characteristics and describe the micro-habitat. We counted 57 burrows and report a density of 0.01 burrows/m². Aggregation indices suggest that burrows are aggregated under some area plots but more evenly distributed on others. The trapdoor is thick and rigid with bevelled edges connected to the entrance rim by a narrow articulated hinge. Two egg sacs from females were obtained and data on eggs and spiderlings are presented. We registered six burrows of an undetermined species of Actinopus. While a few specimens of Actinopus sp. were found inhabiting this hillside, the highest proportion of burrows belonged to C. simoni. Spider diversity on the hillside shows the predominance of Linyphiidae, Nemesiidae and Gnaphosidae. One juvenile of C. simoni was captured using pitfall traps.     

Seasonal cycle of zooplankton abundance and biomass in Hamsilos Bay,Sinop, Southern Black Sea,Turkey

In this investigation, zooplankton was studied between July 2015 and June 2016 in Hamsilos Bay to examine spatial and temporal variations in abundance, biomass and taxonomic composition. The recorded mean zooplankton abundance and biomass were 3770.35 ind. m^?3 and 25.06 mg m^?3 in the inner station, 3928.11 ind. m^?3 and 28.19 mg m^?3 in the middle station and 3948.22 ind. m^?3 and 28.74 mg m^?3 in the outer station, respectively. The high abundance and biomass values observed in September 2015 were attributed to Oithona davisae (4575 ind. m^?3 at the inner station) and Penilia avirostris (33.4 mg m^?3 at the outer station), respectively. Copepoda was the most abundant during the entire period of the survey. In terms of abundance and biomass, Copepoda was followed by meroplankton and Cladocera. Most species within the zooplankton community exhibited evident seasonality throughout the year in Hamsilos Bay. This was particularly apparent for O. davisae, Centropages ponticus, Cladocera and meroplankton, which were abundant in summer–autumn, and for Pseudocalanus elongatus, which was more abundant during winter and spring. It has been determined that O. davisae, which is a non-indigenous cyclopoid copepod species of the Black Sea, has successfully inhabited southern Black Sea and has established a permanent population in this area.     

Spatial and temporal distributions of juvenile horseshoe crabs (Arthropoda: Chelicerata) approaching extirpation along the northwestern shoreline of the New Territories of Hong Kong SAR,China

Juvenile horseshoe crabs, Tachypleus tridentatus and Carcinoscorpius rotundicauda, with prosomal widths of between 11.5 and 102.5 mm, occur along Hong Kong's northwestern shoreline abutting Deep Bay where dissolved oxygen (DO) has been identified as the principal factor determining distribution and survival. Unreported upon hitherto, however, Tachypleus tridentatus occurred consistently in association with sea-grass (Halophila beccarii) beds, with DO concentrations of 8–14 mg·L^?1, a median grain size of >180 μm, interstitial water contents of <36% (sediment wet weight) and organic contents of <3.2% (sediment dry weight). Most individuals occurred between 60 and 120 m down from the shoreline although there appeared to be a trend of down-shore migration in summer, possibly to alleviate thermal stress. No individuals were found at sediment temperatures ≤20°C, i.e. in sub-tropical Hong Kong's winter, when they adopt buried repose. Abundances of emerged T. tridentatus, peaking in November, were synchronized with interstitial salinities of 22–26‰ and averaged 1–2 individuals per 100 m². Mean population density of T. tridentatus was 4–9 individuals per 100 m². Only four individuals of C. rotundicauda were found in August and September, suggesting a recent dramatic decline in numbers. The natal crèche environment for juvenile horseshoe crabs in Hong Kong is deteriorating and threatening their survival.     

Hibernation and emergence pattern of Tupinambis merianae (Squamata: Teiidae) in the Taim Ecological Station,southern Brazil

The emergence period and winter aggregations of a population of Tupinambis merianae from southern Brazil as well as some behavioural aspects from its post‐emergence period are examined. Fifty‐six individuals were captured and marked in 64 days (640 h) of field study. Most of the hibernacula identified were beneath human constructions. The first individuals emerged in August and the last active ones were observed in April. The population's emergence shows a protandric pattern, where males emerge before females, both in adults and juveniles. After emerging, males basked in aggregations of up to 13 individuals, in which individuals changed positions following audible resonant signals emitted by the lizards. Sibilated sounds were emitted in stress situations or in agonistic interactions. Future studies are necessary to elucidate behaviour patterns of the species in the natural environment, mainly related to the utilization of sound communication.     

Effects of temperature and salinity on survival and growth of the amphipod Hyale crassicornis (Gammaridea,Hyalidae)

This study explored the survival and growth of the marine amphipod Hyale crassicornis under different conditions of ambient temperature and salinity in the laboratory. In 96‐h exposure experiments at a salinity of 30, H. crassicornis tolerated temperatures between 6 and 28°C (>90% survival). The 96‐h LT₅₀ value (median lethal temperature) at high temperature range for the amphipod was 32°C. The values at low temperature range for adults and juveniles were 3.2 and 4.2°C, respectively, indicating that adults have a higher tolerance to low temperature than juveniles. At 25°C, the amphipods tolerated salinities between 10 and 50 (with >80% survival in 96?h). The 96‐h LS₅₀ values at high and low salinity ranges were 56 and 2, respectively. Growth of the juveniles from instars 1 to 6 was determined under different combinations of temperature and salinity. Growth rate of juveniles cultured at 25°C and a salinity of 20 was the highest (0.114?mm?day^?1) among the combinations of 15–25°C and 10–40 salinity. The moult increment of body length was affected by both temperature and salinity. Yet the intermoult duration of the amphipods was affected by temperature only but not by salinity.     

Reproductive biology of Limnoria chilensis: another boring peracarid species with extended parental care

Several boring peracarid species engage in extended parental care with parents tolerating small juveniles in their burrows, but only anecdotal observations have been reported from boring isopods of the genus Limnoria. The isopod Limnoria chilensis Menzies is frequently found in holdfasts of the macroalgae Macrocystis pyrifera (L.) C. Agardh and Durvillea antarctica (Chamisso) Hariot. In the present study, holdfasts of D. antarctica that harboured L. chilensis were carefully dissected in order to examine the association pattern of reproductive females and small juveniles. In most infested holdfasts, L. chilensis reached very high densities of 43.7 ± 3.9 (mean ± SE) individuals cm^?2 (range: 0–90 individuals cm^?2). The overall sex ratio (females:males) was close to unity (1.2). Male size varied between 1.5 and 2.6 mm body length (BL) and female size between 1.5 and 3.6mm BL. The percentage of reproductive females was low (19.7% of all females), and only the largest females (>2.6 mm BL) were reproductive. Embryo numbers ranged between six and 19 per female and a significant correlation between female BL and the number of embryos was found. Several females were found with small juveniles (0.8–1.2 mm BL) in the terminal end of their burrows. On several occasions, aggregations of similar-sized juveniles (1.0–1.5 mm BL) in their own burrows were found near a female burrow, indicating that these juveniles initiated their first individual burrows from within the maternal burrows. Some females with small juveniles in the terminal end of their burrows were either accompanied by males or they were ovigerous, indicating that they may have been in the process of producing a second brood. The fact that juveniles build their first burrows in the protection of female burrows suggests that such small juveniles have not yet developed full boring capacity. Extended parental care in this (and other boring) peracarid species represents a mechanism facilitating high juvenile survival rates. Given the highly local recruitment, it is suggested that the reproductive biology of this isopod has strong implications for Its population biology.     

Planktonic copepod community of a reef zone in the southern Gulf of Mexico

ABSTRACT

In this study, the variation of seasonal and inter-annual density and diversity of the copepod community in the Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) was analysed. Samples were collected under nortes, rainy and dry weather conditions in 2011, as well as under nortes and dry weather conditions in 2012 and 2013 in four transects. Surface trawls with 330-μm conical nets were made. The temperature, salinity and dissolved oxygen were measured in situ. The values obtained were 23.07 ± 0.53 to 29.29 ± 0.27°C for temperature, 33.43 ± 0.49 to 35.91 ± 0.09 for salinity, and 2.52 ± 0.08 to 6.56 ± 0.08 mg l^?1 for dissolved oxygen. The copepods collected belonged to 19 families, 28 genera and 62 species. Copepods represented between 69.74% and 76.79% of the abundance of crustaceans present in zooplankton. The highest number of copepods occurred under nortes weather conditions in 2011 with 401,885 ± 28,092 copepods/100 m³ of the species Temora stylifera. In 2012, 256,325 ± 76,872 copepods/100 m³ of the species Paracalanus aculeatus were obtained and in 2013, 311,526 ± 76,872 copepods/100 m³ of the species T. turbinata. The highest specific richness was found in the southern zone with 28 species. In 2013 the highest density was found in the northern zone with 100,323 ± 28,888 copepods/100 m³. The highest diversity was found under dry weather conditions in 2011 with 3.71 bits/individual. In the 3 years of study, 24 species were dominant; 12 of these, appeared in the 3 years of sampling: T. stylifera, T. turbinata, Labidocera scotti, P. aculeatus, O. latus, Pontellopsis villosa, Centropages velificatus, Parvocalanus crassirostris, Corycaeus speciosus, Undinula vulgaris, Oithona plumifera, and Farranula gracilis. Canonical correlation analysis showed the formation of five groups explained by the neritic or oceanic affinity of the species and their tolerance to changes in salinity or temperature.     

A not so natural history of the tarantula Brachypelma vagans: Interaction with human activity

We describe the structure of a population of Brachypelma vagans (Ausserer, 1875) in relation to the intensity of human activity and report characteristics of the burrows in Campeche, Mexico. During September and October 2003, we established sampling areas in five different classes of vegetation type/land use: mature forest (MF), secondary forest (SF), backyard (BY), and a football field divided into corner area (FC) and goal area (FG). The densities of spiders and the proportion of different age/gender classes of individuals on the sites were compared. Morphological data among adults and juveniles were contrasted, and differences in morphology between juveniles were tested according to land use class. We compared the nearest distances between neighbouring burrows and between burrows and trees. Also, we studied the orientation of the burrows, and compared the diameter of the burrow entrance. Brachypelma vagans was found exclusively in the open areas with densities that ranked from 0.02 to 0.1 individuals per square metre, being among the highest ever reported for Theraphosidae. However, there was a negative relationship between density and intensity of human activity. The population of this tarantula shows segregation in occupation of space. Females occupied exclusively the backyards, whereas juveniles occupied sites according to their stage of development. The youngest juveniles occupied the backyards, while the pre‐adults occupied the football field. The distance between burrows was highly variable at all the sites. However it tended to be shorter in the backyards. The orientation of burrows was in all sites preferentially directed northwards. The diameter of the burrow entrances was a relatively good indicator of the sex and age of its occupier, and related almost directly to the dimension of the body. This study provides better knowledge of the structure of B. vagans populations in a human‐modified environment and gives new information on the natural history of these spiders.     

A method of obtaining dietary data for slow worms (Anguis fragilis) by means of non‐harmful cooling and results from a Danish population

Diet composition of slow worms (Anguis fragilis) from a Danish population was recorded from May to September 2006. Slow worms were maintained in cool conditions (at 8°C) for a maximum of 126 h, which made approximately half of the animals regurgitate. The method worked equally well on juveniles and adults. The regurgitations revealed that the slow worms preyed on small snails, slugs, pill millipedes (Glomeris marginata), earthworms and Lepidoptera larvae. There were seasonal changes in taxon composition of the diet but no ontogenetic or sex‐related differences. The food quality of selected prey types was tested on juveniles in a laboratory experiment. Mealworms gave a significantly lower gain in mass and snout–vent length than slugs, earthworms and a mix of all three prey types. A supplementary experiment revealed that slow worms from the present population completely rejected mealworms as prey. Earthworms seemed to be nutritionally inferior to molluscs.     

Aspects of the biology of a population of the cosmopolitan brittlestar Amphipholis squamata (Echinodermata) from the Firth of Forth,Scotland

In the Firth of Forth, Amphipholis squamata has continuous brooding, and pulsed breeding and recruitment, with highest numbers of brooded embryos and newly released juveniles occurring in the summer months. The estimated size of maturity was 1·5 mm disc diameter although the majority of reproductive output came from individuals of between 2·00–2·99 mm disc diameter. Brittlestar size and season had significant effects on embryo production. Embryos of different developmental stages were present in the bursae of the same individual, and newly spawned embryos and those of a potentially releasable size were present each month. The majority of juveniles apparently emerge at a disc diameter of between 0·8–1·2 mm.

Brittlestars were found with full stomachs throughout the year but a peak of feeding was recorded during summer when growth and seawater temperatures were highest. Stomach analyses indicated that almost all animals (99·4%) ingest fine particulate matter but a relatively wide range of plant and animal food items was also identified. Approximately 3% of this Scottish population of A. squamata was infested by the ectoparasitic copepod Cancerilla tubulata.     

Behaviour and habitat of Neohela monstrosa (Boeck, 1861) (Amphipoda: Corophiida) in Norwegian Sea deep water

There are few in situ observations of deep-sea macrofauna, due to the remoteness of this ecosystem. Visual surveys conducted for marine management by MAREANO, (marine area database for Norwegian waters) and the petroleum industry (by SERPENTS, scientific and environmental remotely operated vehicle partnership using existing industrial technology) have provided unique material of visual information from large areas in the Norwegian Sea. The distribution, density and behaviour of the deep-sea amphipod Neohela monstrosa (Boeck, 1861) is described based on videos and samples from the Norwegian Sea. This amphipod is common on mud bottoms at 200–2181 m depth in the area. Dense communities were found in stands of the arctic sea pen Umbellula encrinus at more than 1000 m depth where temperatures were below 0° C. The mean density of N. monstrosa observed for larger areas was 4/100 m² but densities of 15–36 individuals per m² were found in local patches. It is domicolous which is characteristic of the superfamily Corophiida and digs burrows in soft muddy bottoms primarily by using large shovel-like gnathopods to scoop the sediment out. The amphipod was observed pushing and rolling sediment balls out of its burrow, which were probably held together with amphipod silk. It digs out an upper 3 to 4 cm wide burrow with a horizontal side burrow a couple of centimetres down. Neohela monstrosa appears to feeds on newly settled detritus that it collects from the surface sediment through the use of its long antennae while the burrow is mainly used for protection against predators such as demersal fish. Newly released juveniles are probably kept in the burrow for protection. Based on the local high density of N. monstrosa together with its habit of making long burrows, we suggest that there is significant bioturbation associated with the presence of N. monstrosa in deep sedimentary habitats of the Norwegian Sea, which likely provides an important ecosystem function.     

The hermit crab Sympagurus dimorphus (Anomura: Parapaguridae) at the edge of its range in the south-western Atlantic Ocean: population and morphometry features

Sympagurus dimorphus is one of the 12 hermit crab species recorded for Argentinean waters. Despite the high abundance registered in some scallop fishing grounds, its biology remains little known. In the present study, we analysed some population features of S. dimorphus living in symbiosis with Epizoanthus paguricola from a series of samples taken in the Argentine Sea, south-western Atlantic Ocean. Our results showed that S. dimorphus was commonly found from 40ºS to lower latitudes, in a patchy distribution along the shelf-break front. The overall sex ratio was 1:1. The smallest ovigerous female measured 6 mm in cephalothoracic shield length and this size was used as parameter to define the size of juveniles. The sex ratio size class pattern corresponded to Type IV or anomalous curve. S. dimorphus is a dimorphic species, as evidenced by the larger size of the males and the positive allometric growth of the right cheliped. The species also showed asymmetry, with the left uropod always larger than the right one. To the best to our knowledge, this is the first report on population features and relative growth for a member of the genus, based on long-term sampling. This species presents a patchy distribution along the shelf-break of Argentina. Its density tended to decrease over the five-year sampling period regarding the recruitment of hermits associated with colonies of zoanthids. In addition, the relatively homogeneous nature of this refuge does not seem to influence the growth of the hermit crab, which presents sexual dimorphism in relation to the sex/size conditions.     

Responses of pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817) (Penaeoidea) to physico-chemical parameters in a marine protected area: changes in abundance and distribution after 20 years

ABSTRACT

This study analysed the influence of temperature, salinity and sediment texture on the distribution of pink shrimp juveniles (Farfantepenaeus brasiliensis) over a 20-year period. The shrimps were sampled monthly in Fortaleza Bay, north coast of São Paulo, Brazil, in November 1988–October 1989 (period 1) and then 20 years later in November 2008–October 2009 (period 2). In period 1 we captured 80 juveniles whereas in period 2 we captured 226. The abundance and distribution of F. brasiliensis seemed to be modulated by temperature and sediment texture, along with the fishing activity. The management strategies established between the samplings might have been responsible for the higher abundance of juveniles seen during period 2. The strategies included the limitation of fishing effort, regulation of fishing equipment and the establishment of environmental protection areas and temporary fishing ban.     

Activity and reproduction in Megalobulimus paranaguensis (Gastropoda,Eupulmonata): implications for conservation in captivity for a South American land snail

ABSTRACT

In South America, Megalobulimus includes a number of threatened species, as well the largest land snails on the continent. The activity patterns and reproductive aspects of this group have not been documented. This work describes the daily and seasonal activity patterns and reproduction of M. paranaguensis. We maintained specimens in the laboratory for one year, and we quantified their behaviour for one hour at four different times of the day (0 h, 6 h, 12 h and 18 h) during three days in four months (August, September, April and May). The number of postures, hatching rate, time of hatching since oviposition and mortality rate among juveniles for each month were also quantified. Megalobulimus paranaguensis was more active in August, and had a egg laying peak one month after. Fifty-one eggs were laid by 12 captive individuals throughout the year, with a mean value of 4.25 eggs per individual. The hatching rate was 80.39%, and the time of hatching since oviposition was 56.7 ± 4.3 days. In two eggs, we observed the presence of twins. The mortality rate among juveniles was low (9.30%) indicating that rearing land snails in captivity has the potential to be an important and viable tool for the management and conservation of these organisms.