Biology and life cycle of Tmetonyx similis (G. O. Sars, 1891) (Amphipoda,Lysianassidae), a scavenging amphipod from the continental slope of the Mediterranean

The present study focused on the biology and life cycle of Tmetonyx similis, a scavenging amphipod inhabiting the continental slope of the north‐western Mediterranean. All the categories of individuals were observed in the samples. The emergence of offspring occurs in successive cohorts. The lifespan of the females is longer than that of the males, but the sex ratio is strongly in favour of the males. The fecundity was found to be lower than that of the other female crustaceans present in these samples. The growth pattern was modelled. A strong correlation was observed between the length and the weight of the animals collected. Several hypotheses are proposed to explain a sex ratio in favour of males. This result may be explained by a migratory process of the females of T. similis. A comparison of the reproduction strategy is given for the three main scavenger crustacean species (amphipods and isopod) collected in this area.     

Relative growth and sexual dimorphism of the South Atlantic hermit crab Loxopagurus loxochelis (Anomura,Diogenidae) from Ubatuba,Brazil

Some morphometric relationships and biometric aspects were studied in the hermit crab Loxopagurus loxochelis (Moreira, 1901) with the purpose of describing its relative growth and finding the size where sexual maturity is reached. Specimens were collected monthly from September 1995 to August 1997 in the Ubatuba region using double-rig trawl nets. A total of 1084 specimens (625 males and 459 females) was analysed. In this species, sexual dimorphism is particularly evident in chela dimensions. Differences between males and females were found in the left propodus length versus cephalothoracic shield length (CSL) and wet weight (WW) versus CSL relationships. Males showed a high positive allometry in chela growth, while females were close to isometry/negative allometry. The size at which a clear differentiation occurred in the growth of the propodus length and in the increase in weight of males and females was between 4.5 and 6.0mm CSL, suggesting that size at which sexual maturity is reached.     

Reproductive biology of two species of Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from southern Brazil

Reproduction is a critical event in the life cycle of animals, and a high amount of energy is allocated to it. The aim of this study was to characterize the reproductive biology of two recently described species of Hyalella from the north-east region of state of Rio Grande do Sul in southern Brazil. The specimens were collected during 12 months from a stream source (Hyalella georginae) and from a water reservoir (H. gauchensis), in Palmeira das Missões municipality, state of Rio Grande do Sul. Upon sampling, ovigerous females and pairs in precopulatory behaviour were separated into microtubes. In the laboratory, the cephalothorax length (CL in mm) of all specimens was measured. Male size at onset of sexual maturity was larger than that of the females, in both species. There was a correlation between the size of paired males and females: larger males carried larger females, in both Hyalella species. Precopulatory pairs were found throughout the year; however, H. georginae had a higher frequency in spring, and H. gauchensis in autumn. There was a positive correlation between the CL of ovigerous females and the number of eggs/juveniles. A reduction in the number of eggs throughout the embryonic development was observed in H. georginae. The average fecundity of H. georginae was significantly higher than H. gauchensis. The differences between the reproductive biology of these species may be related to the physical and environmental conditions at which they are exposed in their habitats.     

Population characteristics of four deep‐water pandalid shrimps (Decapoda: Caridea) in the northern Aegean Sea (NE Mediterranean)

The population characteristics of four deep‐water pandalid shrimps (Decapoda: Caridea) were studied in the northern Aegean Sea in samples collected annually (1997–2000) in summer, through experimental trawl, at depths down to 600 m. Females were larger than males in Plesionika martia and Plesionika heterocarpus; no significant differences in size of males and females were found in Chlorotocus crassicornis and Plesionika antigai. A trend of increasing size with depth was observed, as well as a linear increase in the proportion of females with increasing size. Sex ratio was skewed towards females at all depths in P. antigai, while in P. heterocarpus and C. crassicornis males dominated the intermediate depths. Negative allometries were apparent in the carapace length–weight relationships in males of all species. Isometric relationships were found in females apart from in P. heterocarpus. The population patterns conform to relevant Mediterranean reports. However, some population differences exist that may reflect the distinct environmental conditions prevailing in the study area.     

Morphometric structure and allometry profiles of the giant red shrimp Aristaeomorpha foliacea (Risso, 1827) in the eastern Mediterranean

The relative growth of body parts, such as abdomen, uropod, scaphocerite, telson, rostrum, and the third pereiopod of males and females of the giant red shrimp (Aristaeomorpha foliacea, Risso, 1827) was studied in samples from the Greek Ionian Sea (eastern Mediterranean) in 1999–2000. These were related to carapace length, sex and size of individuals. A length–weight relationship was also obtained. In general, a negative allometry of swimming appendages (uropod, scaphocerite), abdomen (related to metabolic processes), and length of the third pereiopod (involved in walking ability) was observed in both sexes. Growth of the telson was positively allometric in females and negatively allometric in males. Asynchronous growth of the male rostrum was also noted. Appendages were proportionally longer in juveniles than in adults of both sexes. A strong negative allometry between length–weight for both sexes was shown, and females were heavier than males in all sampled months.     

Age structure and growth in an isolated population of Pelodytes punctatus in northern Spain

We studied the age structure and the growth of a breeding population of parsley frogs, Pelodytes punctatus, from a pond system in northern Spain using skeletochronological methods. This population lives in an upland area with marked seasonal differences characterized by long, cold winters and dry summers. We assessed, using the mark–recapture method, the annual periodicity of bone growth marks. Only one line of arrested growth is laid down per winter, showing, in general, a well-defined histological structure. Females are larger than males with 43.31 and 36.32?mm average body length, respectively. This sexual dimorphism in body length increases with age. Males and females reach sexual maturity when they are 1 year old. The oldest males were 8 years old while the females were 2 years older. Growth curves for both sexes were constructed based on body size and the number of lines of arrested growth found in bone sections. The growth rate of males declined abruptly after the first year. Females delayed reproduction and continued to grow at a high rate for 2 years longer than males, thus reaching a higher asymptotic size.     

Mating behaviour and maternal care in the tropical savanna funnel-web spider Aglaoctenus lagotis Holmberg (Araneae: Lycosidae)

Despite their abundance and diversity, Neotropical spiders have been the subject of relatively few studies of behavioural ecology. The sexual behaviour and maternal care of the spider Aglaoctenus lagotis (Lycosidae) is described here. We performed experimental manipulations to test the hypothesis that males are attracted by female cues in the web. Two predictions were tested: (a) webs used by a virgin female will attract more males than webs used by an inseminated female; (b) the main cue in the web is chemical, so webs recently used by virgin females will attract more males than those that are not recently used. Additionally, we tested the hypothesis that maternal care increases offspring survivorship. Results showed that males are attracted by recently used webs (z = 0.0015; p = 0.037; z-test) and webs of virgin females (z = 0.041; p = 0.036, z-test). Male sexual behaviour presented three different categories: court, pre-mate and mate. After the mating, the females built a cocoon that was transported adhered to the spinnerets and held by the last pair of legs. After the hatching of the eggs, the young migrated to the dorsal region of the mother's body for 5 days. During maternal care the mother eliminates a yellowish drop from its oral cavity, which is collected by the young. During the development of the young until adulthood, the offspring that have their mother present in the first stages of life have greater survival compared with those without maternal care. Our results make it possible to perform comparative analyses between a South American Lycosidae species and other species distributed worldwide.     

Observations on the tube-building behaviour of the marine amphipod Cymadusa filosa Savigny (Crustacea: Ampithoidae)

The study reports on the tube-building behaviour of the corophioidean amphipod, Cymadusa filosa Savigny on two algae, Sargassum binderi Sonder and Ulva lactuca Linnaeus, based on experimental protocols using specimens in aquaria and in petri dishes. Cymadusa filosa was observed to construct open-ended, uniform diameter cylindrical tubes using amphipod silk, to bind together faecal pellets, detritus and fronds of Sargassum binderi or Ulva lactuca. Detailed studies of tube-building behaviour were carried out in petri dishes containing Ulva lactuca, using isolated specimens (5–13 mm in size) of different sexes for a period of one and a half months. Both males and females constructed tubes, and an average of four tubes were built by adults in 15 days. Females with young in the brood pouch did not construct new tubes following juvenile release. Juveniles were observed to build tubes using detritus and faecal material only within hours of being released from the brood pouch. The tubes of juveniles were either built on the walls of their mother's tubes or on an algal mass put together by the mother. There was a highly significant positive correlation between body length and tube length in males and females. There was no significant difference in the rate of tube length increase relative to body size between males and females, between males less than or more than 10 mm, or between females of less than or more than 10 mm. Tube-sharing was also observed between males and females.     

Spatial patterns of the semi-aquatic rodent Nectomys squamipes in Atlantic forest streams

Nectomys squamipes is a semi-aquatic rodent with a wide geographic range in Brazilian forests and savannas. This species is a host for several parasites associated with aquatic environments, especially Schistosoma mansoni, and thus its spatial pattern may influence some diseases’ patterns. Here we present important aspects of water rat spatial behaviour, including technical and ecological aspects. Water rats were studied by live trapping in rivers and in gallery forests between January 2005 and August 2008, with a total sampling effort of 9511 trap-nights. We also studied some animals through radio tracking and the spool-and-line technique. Water rat movement was distributed evenly between the terrestrial and aquatic environments. Nectomys squamipes occurrence in small tributaries was higher than in larger and lotic rivers. Both home range, the conventional two-dimensional approach, and home length, a one-dimensional approach, proved to be useful to study N. squamipes, depending on the shape of the water body used by the individual. Although Nectomys squamipes’ home length was positively correlated with body weight, sex was also important to explain home length variation; at similar body weights, males have larger home lengths than females. Males explored larger areas during the rainy season, likely in search of females, as this is the water rat reproductive season in Atlantic forest. In contrast, females explored larger areas during the dry season, likely looking for additional food supplies as a result of deficient water rat food supplies during the Atlantic forest dry season. Females overlapped home lengths with more than one male, and males with more than one female, suggesting a promiscuous mating system for this species.     

Breeding biology and population structure of the intertidal crab Petrolisthes laevigatus (Anomura: Porcellanidae) in central-southern Chile

The present study describes the seasonal reproductive cycle and population structure of the porcellanid crab Petrolisthes laevigatus, a typical inhabitant of the rocky intertidal. A total of 960 individuals (including 372 females) was collected in monthly samples from October 1993 to December 1994 in central-southern Chile. Ovigerous females were present between August and December, and were absent between January and July. The breeding season started during late winter (August), and females with embryos close to hatching occurred between October and end of spring (December). Considering the gonadosomatic index and the duration of the incubation period, it is concluded that P. laevigatus has a markedly seasonal breeding period with probably two successive spawnings per female per season. Our results compared with previous studies in temperate intertidal porcellanids suggest a lower structural variability of the population during the sampling period, but a pronounced seasonal variation in both sex ratio and abundance. The influence of environmental habitat conditions (i.e. temperature) is suggested to be responsible for the lower variation in the crab population size structure in ovigerous females, and the almost constant size distribution observed in males.     

Are there costs to extended larval transport in the Trinidadian stream frog,Mannophryne trinitatis (Dendrobatidae)?

Previous work has shown that male Mannophryne trinitatis (Dendrobatidae) carry their larvae on their backs for up to 4 days in search of a predator‐free pool in which to deposit them. The experiments reported here investigated whether costs to the larvae or to the adults limit transport duration. We simulated transport durations of 0, 4, 8, and 12 days for larvae, but found no deterioration in terms of ability to grow to metamorphosis; indeed, 12‐day larvae grew better than all the others. After 8 days of simulated transport, larvae had used up all their yolk reserves and begun to lose dry weight. Larvae on wet substrates gained wet weight and length but on drier substrates merely maintained weight, suggesting that dehydration could be a problem on the male's back. In a trial of locomotor performance (mean jump length; number of jumps to traverse a runway), females performed best with calling males not significantly different from transporting males, despite an average larval load equivalent to 15–20% of the frog's mass. Assessment of gut contents showed that females foraged more than males, but that transporting males foraged as much as did calling males. We found no differences between the three classes of adult frogs in fat body weight.     

The occurrence of the genus Ingolfiella (Crustacea,Amphipoda) in South Africa,with description of a new species

Abstract

The occurrence in South West Africa, i.e. within the confines of the Republic of South Africa, of the Amphipod genus Ingolfiella Hansen is recorded. The species is subterranean, is larger than any of the previously known species, and is described as I. opisthodorus sp. n. It is compared with I. leleupi Ruffo from the Congo and Northern Rhodesia. The majority of the specimens seem to be females although none has even a trace of oostegites or brood lamellæ. They exhibit a marked dimorphism of the first pair of pleopods, chiefly in specimens exceeding 14 mm. in body length; a juvenile form of this pair occurs in specimens measuring 12 to 14 mm. A few supposed males, among the last specimens to be collected (in June), are smaller than the supposed females but the two pairs of gnathopods are relatively larger and of a different form.     

Aspects of natural history in a sand boa,Eryx muelleri (Erycidae) from arid savannahs in Burkina Faso,Togo, and Nigeria (West Africa)

The ecology of West African arid savannah snakes is still poorly known, especially in regard to the fossorial species. Here, field data on distribution, morphometrics, habitat use and diet are reported for the sand boa Eryx muelleri (Erycidae) from three different countries, i.e. Burkina Faso, Togo and Nigeria. This snake was observed in 21 distinct localities, and a total of 39 individuals was recorded. The species is likely fairly common and locally abundant. Mean body length of snakes was similar among countries and between sexes, but males had proportionately longer tails than females. Body length was significantly positively correlated with both tail length and head length. Adult sex ratio was close to parity. Most of the specimens were found in well-vegetated spots with low percentage of bare soil. There were apparently both ontogenetic and intersexual dietary variations: (1) a single analysed juvenile fed upon a small-sized lizard, whereas adults fed considerably upon young rodents; and (2) females fed exclusively upon young rodents and males upon both lizards and young rodents. In conservation terms, the species is actively exported from Togo for the pet trade, and additional individuals may also be illegally collected in other countries.     

Feeding ecology of the common sun skink,Eutropis multifasciata (Reptilia: Squamata: Scincidae), in the plains of central Vietnam

We studied the feeding ecology of Eutropis multifasciata in the tropical plains of central Vietnam to understand better the foraging mode, spatiotemporal and sexual variation in dietary composition, and rarefaction curves of prey-taxon richness for males and females. Stomach contents (n = 161) were collected from October 2013 to May 2014 using a nonlethal stomach-flushing technique. A total of 680 food items (624 animal items and 56 plant items) was found in 161 stomachs of skinks, representing 19 unique animal categories. We found that the diet of E. multifasciata is composed mainly of small, sedentary and clumped prey and that this skink specialises on spiders, insect larvae, snails, grasshoppers and crickets (with a combined importance index of 60%). Dietary composition, prey size and total prey volume in E. multifasciata changed between dry and rainy seasons and among regions. The total volume of food items consumed by males was larger than that of females, and the diversity and evenness index of prey categories were larger in males than in females. However, using rarefaction curves revealed that females have the higher prey-taxon richness after points between 130 and 140 prey items for frequency, and between 160 and 170 prey items for number of items, and the differences were not statistically significant. The foraging behaviour of E. multifasciata best fits a ‘widely foraging’ model.     

Dietary variation and overlap in D’Orbigny’s slider turtles Trachemys dorbigni (Duméril and Bibron 1835) (Testudines: Emydidae)

Although D’Orbigny’s slider (Trachemys dorbigni) is the most abundant freshwater chelonian species in southern Brazil, little is known about its feeding habits. Our goal was therefore to evaluate this species’ dietary composition and niche variation there. For this, we collected road-killed animals (n = 73) on a federal highway (BR 392) between 2002 and 2003, and analysed their gut contents. We identified 26 different dietary items, and our results indicated that D’Orbigny’s slider is omnivorous in this area. Total food volume, as well as the degree of herbivory and carnivory, were similar between males and females. However dietary composition of plants was different: although both males and females fed on underwater plant matter, only females consumed surface macrophytes. This finding suggested differential microhabitat usage between males and females throughout the swamps.     

Phoretic behaviour of Attacobius attarum (Roewer, 1935) (Araneae: Corinnidae: Corinninae) dispersion not associated with predation?

Attacobius attarum spiders exhibit a phoretic behaviour on the winged sexual of Atta leaf-cutting ants during their mating flight. However, it is unclear if this behaviour is for dispersion or to facilitate the predation of ants in the new colonies. A nest of Atta sexdens was monitored on the day of the mating flight, and the winged ants, as well as the spiders, were collected. The results obtained corroborate the hypothesis that phoretic behaviour is commonly used for dispersion of the spider A. attarum, predominantly females. Of these spiders, 64 individuals of A. attarium were collected, of which 62 were females (96.9%) and two were males (3.1%). Regarding the winged leaf-cutting ants sampled, 378 females and 361 males were collected, totaling 739 individuals. Of these, 64 individuals (8.7%) had a spider attached to its back for phoretic dispersal and none was observed on the queens after the nuptial flight. In our study, A. attarum females perform phoretic dispersal into the environment on winged leaf-cutting ants but do not settle in the new nests.     

Life history of the spider Selenops occultus Mello‐Leitão (Araneae,Selenopidae) from Brazil with notes on the natural history of the genus

Selenopids are extremely fast‐moving, dorsoventrally flattened spiders and are among the most secretive of animals. However, they can be locally abundant, providing an opportunity to examine their life and natural histories. Here we report life history data from Selenops occultus which were studied and collected monthly for over a year at an experimental farm of São Paulo State University in Botucatu, Brazil. We compare these data with what we have found in other Selenops species in the Caribbean region. Overall, S. occultus showed considerable seasonality. Males were most common in January and March, whereas females were more common in June and November. Significant differences between the numbers of males collected during the wet and dry seasons indicate that mating may be limited to the wet season. The Caribbean species share similar natural histories to S. occultus, such as little conflict in small areas and overlapping generations throughout the year.     

Age-related body weight,fecundity and population change in a south Dorset sika population (Cervus nippon); 1985–1993

Density-related changes in performance have been documented for a number of different ungulate species, with recorded decline in body weight, fecundity and both juvenile and adult survival as population densities increase. While density-dependent responses of this kind have been explored in some detail in red, roe and fallow deer, little published information is available on demographic responses to density in European populations of sika deer (Cervus nippon). This paper offers an analysis of the dynamics of two populations of sika from the south of England from 1985–1993. Data on age-related body weights for males and females and pregnancy rates of females are taken from analysis of cull records of 321 males and 534 females culled during that 8-year period. We describe trends in body mass of adult and juvenile sika of both sexes, and consider changes in pregnancy rates of both mature and yearling females in relation to changes in relative abundance. Despite steadily increasing population density between 1985 and 1991/1992, no consistent decline was recorded in body weight or condition (as measured by % cover of kidney fat) for calves or yearlings of either sex, or for mature females. A decline in recorded body weight of adult males was not significantly correlated to ranked relative abundance. Fecundity was high (with > 90% of mature females sampled found pregnant). Most mature females found pregnant were also lactating. The proportion of animals that conceived as yearlings (72%) was lower than that recorded for more mature hinds; however there is some indication that the difference recorded may simply reflect the fact that yearlings may conceive later in the season than older animals. No significant differences were apparent in the proportion of either adult or yearling females found pregnant in different years.     

Ecological distribution and reproductive period of the hermit crab Loxopagurus loxochelis (Anomura,Diogenidae) on the northern coast of São Paulo State,Brazil

The present study aimed to determine the ecological distribution of Loxopagurus loxochelis as a function of selected environmental factors, as well as its reproductive period based on the combined analysis of the presence of ovigerous females and the development of the gonad. The collections were carried out monthly from January to December 2000 in the region of Ubatuba (SP), using a fishing boat equipped with two double rig nets, in isobaths of 5, 10, 15, 20, 25, 30, 35 and 40?m, at which depths samples of sediment and water were collected. The cephalothoracic shield length and sex of the animals were determined; the abdomen was dissected to verify gonad development stages. A total of 334 individuals was obtained (196 males, 48 ovigerous females and 90 non-ovigerous females) with sizes varying from 3.0 to 8.6?mm (5.7±1.0?mm). A greater abundance of L. loxochelis (95.2%) was observed at depths of 20 and 25?m. These sites mainly revealed a substratum stable with a very fine sand fraction, which facilitates the habit of embedding shown by this hermit. With regard to gonadal analysis, it was possible to classify four gonad development stages for each sex: immature, rudimentary, developing and developed. It was observed that in the winter months about 71% of the females had gonads either developing or developed and 67% were ovigerous. Therefore, the winter period can be considered the peak of reproduction for this species, characterizing a typical seasonal-continuous reproduction.     

Reproductive traits in the northern scorpion ( Paruroctonus boreus )

Despite its large geographic range, little is known about reproductive traits in the northern scorpion ( Paruroctonus boreus ). We analyzed reproductive traits for 36 females from a population near Billings, Montana. All data were collected within a single year. Litter size, offspring mass, total litter mass (TLM), and relative litter mass (RLM) were within the ranges of values reported for other species in the Vaejovidae. Female size (length or mass) was not correlated with any reproductive trait. Litter size and offspring mass were each positively correlated with RLM, suggesting that females investing relatively larger amounts of energy in reproduction increase both size and number of offspring. Finally, the within-litter coefficient of variation in offspring mass was negatively correlated with RLM, TLM, and mean offspring mass, suggesting that females investing more energy in reproduction produce more-uniformly sized offspring, an observation that appears common in scorpions.