The biology of Vaejovis littoralis Williams, an intertidal scorpion from Baja California, Mexico

Vaejovis littoralis Williams is an intertidal scorpion inhabiting chiefly the drift zone in the high intertidal of beaches in Baja California, Mexico. Density within the drift zone averages approximately 2–4/m² (island sites) to 12/m² (mainland sites). Populations are aggregated into patches. Primarily, juveniles exhibit diurnal activity. Nocturnally active juveniles tend to be spatially segregated from nocturnally active adults within the drift zone.
Diet of V. littoralis includes the isopod Ligia, V. littoralis , spiders, pseudoscorpions, centipedes and beetles. Prey size is not a function of predator size. Centruroides exilicauda, V. littoralis and Ligia were observed as predators on V. littoralis .
The adult sex ratio is skewed toward females (1 male : 2.1 females). Adult females are usually larger than adult males. Litter size ranges from 1–8. Limited data suggest that offspring size and litter size increase with maternal size.
Vaejovis littoralis exhibits cryptic coloration, small size and lithophilic tarsal claws, all of which favour intertidal existence. Although V. littoralis is able to withstand up to 12 hours of submergence, it does not survive submergence significantly better than a comparable desert species. Field data suggest that V. littoralis does not exhibit an endogenous tidal rhythm.     

Population variables and life-history characteristics of the alligator pipefish Syngnathoides biaculeatus, in Papua New Guinea

Population structure and life-history variables of the widely distributed alligator pipefish Syngnathoides biaculeatus were characterized in Bootless Bay, Papua New Guinea over the course of 11 months. There was little evidence of seasonality with four focal populations showing no significant change in abundance. Similarly, the sex ratio remained 1:1 for all but 1 month. Reproductive males carrying eggs (148–278 mm in total length, L _T) were found in all months. Brood size was significantly, positively related to male L _T for newly laid broods only. Maximum observed brood size was 351 and mean ± s . d . brood size was 238 ± 57 for newly laid broods. Juveniles and males showed no change in mean L _T over the year while slightly smaller females were captured in November 2006 and September 2007. Males were significantly longer than females so von Bertalanffy growth coefficients were estimated separately for each sex: males L _∞= 285 mm, K = 0·82 year⁻¹ and females L _∞= 261 mm, K = 1·10 year⁻¹. These estimates suggest that this species grows rapidly and has a short-life span. In the context of growing concern about overexploitation of syngnathids, a rapid growth rate combined with year round reproductive activity suggests that the tropical S. biaculeatus may be relatively resilient with regard to fishing pressure.     

Effect of temperature and water activity on in vitro germination of Monilinia spp.

Aims:  This study evaluated the effect of temperature (0–38°C) and water activity ( a _w: 0·87–0·99) on the lag phase prior to germination and the percentage of germination over time for Monilinia laxa , Monilinia fructicola and Monilinia fructigena .
Methods and Results:  More than 80% of viable conidia germinated at 25°C and 0·99 a _w within 2 h for M. fructicola and M. fructigena and 4 h for M. laxa . There was no germination at 38°C, and all three Monilinia spp. germinated at 0°C. At the lowest a _w (0·87), none of the Monilinia spp. was able to germinate at any of the incubation temperatures studied. Whereas at 0·90 a _w, conidia were only able to germinate at 15, 25 and 30°C for the three species studied, except for M. fructicola at 15°C. In contrast, at 0·95, 0·97 and 0·99 a _w, germination occurred at all studied temperatures less 38°C. Generally, the lag phase was longer at low levels of a _w (0·90–095), and differences were more evident as temperatures were far from the optimum (0–5°C).
Conclusions:  Germination and lag phase period were markedly influenced by temperature and a _w, and in general when conditions of temperature and a _w were suboptimal, the lag phase was longer and the percentage of germination was lower.
Significance and Impact of the Study:  Knowledge of the germination requirements of this fungus is important in order to understand their behaviour in natural situations and to provide baseline data required for the construction of new prediction models. Our study might be used to develop a predictive model to understand and control the disease caused by Monilinia spp.     

Activity patterns in moose and roe deer in a north boreal forest

The activity patterns of a coarse browser, the moose. Alces alces , and a selective browser, the roe deer, Capreolus capreolus . in a north boreal forest, central Sweden, were compared with respect to time allocated for foraging and processing (ruminating) in different seasons. Data were quantified by measuring 24 h activity patterns which included both the duration and frequency of active and inactive periods. Activity patterns were measured from 9 female moose and 9 roe deer that were radiomarked during April 1974–May 1978 (roe deer) and February 1982–December 1984 (moose). In total, data were available from 4345 h for roe deer and 14745 h for moose. Roe deer differed from moose in having active bouts more evenly distributed over the day. Generally, both species were most active during sunrise and sunset. Total daily active time varied with season, reaching the highest value in late May – early June among roe deer (56.7% of the day) and a month later among moose (51.9%). Both species were least active in February (30–40%). Average length of active bouts did not differ significantly between the species but changed with season (roe deer 48.6–99.2 min, moose 61.6–88.7 min). Average length of inactive bouts varied significantly with season, with moose having consistently longer bouts (89.3–156.3 min) than roe deer (55.8–107.0 min). The number of activity bouts per day were also higher among roe deer. During midsummer, they changed activity nearly twice as many times as moose (26 times d⁻¹ vs 16 times d⁻¹).     

Age and size compositions, growth and reproductive biology of the breaksea cod Epinephelides armatus, a gonochoristic serranid

Details of the reproductive biology, size and age compositions and growth of the breaksea cod Epinephelides armatus , the sole representative of Epinephelides , were obtained by collecting monthly samples of a wide total length ( L _T) range of individuals from coastal marine waters at 31–32° S on the lower west coast of Australia. Although the modal L _T class of females (250–299 mm) was markedly less than that of males (400–449 mm), the modal ages of the two sexes were similar, i.e. 4 v. 5 years, respectively. The similarity in the age compositions and the histological demonstration that the gonads of all E. armatus consist solely of either ovarian or testicular tissues demonstrate that this species is gonochoristic, which is highly unusual for an anthiinine serranid. The absence of a central, membrane-lined 'ovarian' lumen in the testes of juveniles would account for adult testes containing neither this ovarian remnant nor the peripherally located sperm sinuses that are found in the mature testes of almost all other serranids. The results demonstrate that E. armatus exhibits a very unusual pattern of sexual development for a serranid. The spawning period of E. armatus lasts for c. 9 months, which is long for a species in temperate Western Australian waters, but comparable with that of many other relatively small serranids elsewhere. Females grow slower than males, attaining L _T at 3, 5 and 10 years of c. 200, 285 and 420 mm, respectively, compared with c. 215, 315 and 450 mm, respectively. Females, however, attain maturity at a greater L _T and older age than males.     

Comparisons of the diets and reproductive performances of two sympatric rotifers, Asplanchna girodi and Asplanchna priodonta

SUMMARY. 1. Diet composition and the production of embryos were measured in Asplanchna girodi and Asplanchna priodonta collected through 3 years in the San Joaquin-Sacramento delta of California. The two species are sympatric in low to moderate densities for 5 months of the year.
2. Despite marked differences in the structure of the trophi, both species consumed the same array of prey species. Percentage composition of the diet varied both intra- and interspecifically. The food niches of the two species appear to differ little from one another.
3. Individuals of Asplanchna girodi had a larger mean number of prey in the gut per individual than did those of A. priodonta , due to their larger size. Per unit volume, each species prey gathering performance was the same. Asplanchna priodonta produced more embryos per calculated unit volume of prey ingested than did A. girodi .
4. During spring, when both species were present in the plankton, A. priodonta did not capture Size Class 2 and 5 animals (volumes 0.09–1.0 μm³×10⁶ and 3.0–3.5 μm³X10⁶ respectively) nor large Synchaeta . Both these prey classes were in the diet during the summer and autumn months. Several hypotheses are examined as possible explanations for this phenomenon.     

Factors affecting size, longevity and fecundity in the reindeer oestrid flies Hypoderma tarandi (L.) and Cephenemyia trompe (Modeer)

1. Laboratory reared reindeer oestrid flies Hypoderma tarandi and Cephenemyia trompe (Diptera: Oestridae) were weighed to determine progressive weight loss and death weights at treatments with various temperature and humidity conditions.
2. Four individual measurements of size were taken: larval weight, wet weight of newly eclosed flies, wing length, and weight of flies after dehydration and fat extraction. In H. tarandi, males were bigger than females (except for wing length), whereas the reverse was true for C. trompe .
3. Size variation was not significantly related to conditions (temperature, humidity, duration) during the pupal stage, but individual reindeer produced flies (both species) of different mean sizes. These size differences were not correlated with larval burden (= number of larvae per individual host), but are hypothesized to be connected to unknown host quality factors.
4. Longevity of flies kept in vials and subjected to various temperature and humidity conditions revealed that C. trompe lived significantly longer than H. tarandi (range: 4–44 and 1.2–27 days, respectively) at 5–33 °C. Male H. tarandi survived longer than females; female C. trompe survived longer than males. Longevity was not significantly correlated to any of the size measures.
5. Most flies had a large portion of their fat reserves left at death.
6. In H. tarandi , mean number of eggs was 609 ± SD 73 (range 354–772, n = 119). Egg number was slightly dependent on larval size, but not on wet weight of newly eclosed flies or wing length. In C. trompe , mean number of eggs was 960 ± SD 208 (range 493–1349, n = 31).
7. The possible adaptive value of large size in oestrids is questioned. Benefits of flexibility in size in oestrids are hypothesized.     

Vertical distribution and abundance of invertebrates within the sandy substrate of a low-gradient headwater stream

SUMMARY. 1 The vertical distribution of invertebrates (>0.053 mm) was studied in a sandy-bottomed, first-order stream on the Coastal Plain of Virginia, U.S.A. Invertebrate species composition, abundance and bio-mass were determined monthly over one year at sediment depth intervals of 0–1, 1–5, 5–15,15–30 and 30–40 cm.
2. The subsurface community was numerically dominated by species of Chironomidae, Nematoda and Crustacea, while much of the biomass was due to early instars of several species of Trichoptera.
3. Invertebrate density and biomass decreased significantly with depth in the substrate (ANOVA; P <0.05). Annual mean density decreased from 1,346,844 individuals m⁻³ at the surface to 13,578 individuals m⁻³ at 15–30 cm. Annual mean biomass decreased from 66.30 g m⁻³ at the surface to 0.44 g m⁻³ at 15–30 cm.
4. Dissolved oxygen decreased markedly from the surface to the 5 cm depth in the substrate, anaerobic conditions often occurring below 10 cm. Density and biomass both showed a significant positive relationship with dissolved oxygen concentration (Linear regression; P <0.05).
5. Physical forces were important in structuring the subsurface invertebrate community. Besides low dissolved oxygen concentration, sediment scouring resulting from storm discharge dramatically reduced density and biomass     

Colony structure, seasonality and food requirements of the crazy ant, Anoplolepis longipes (Jerd.), in the Seychelles

Abstract. 1. In Seychelles, A. longipes nests on the ground and in trees, underground nests do not occur, possibly because soils are too hard or unstable.
2. Nest density approached 700 ha^-1 in some areas and nests contained, on average, about 4000 ants. The total population (including foragers) in heavily infested areas may exceed 10 millions ha^-1.
3. On average, each nest contained about forty queens and fifty males, although only 50% of nests contained males. A few nests contained up to 300 queens, 1000 males, 36 000 workers and 23 000 brood.
4. Production of sexual adults and brood was related to the wet season, most being produced shortly before or after the heavy rains from November to March.
5. Natural spread is probably by budding of colonies which, during an expansive period, may advance 1 m day^-1.
6. Food collected by the colony included sugary substances from fruits, honey-dew-producing insects and plant exudates, and proteinaceous material, mainly in the form of insect prey and carcases. A forager collected, on average, 1.2 mg of liquid or 2.8 mg of solid material on each foraging trip.
7. Foraging occurred at fluctuating intensities throughout the day and night, but was limited by heavy rain, strong winds and substrate temperatures above 30°C. Maximum activity occurred at ground temperatures of 25–30°C and ceased about 44°C.
8. Availability of food and nest sites proably have the greatest influence on population size.     

Home-range use, activity, and density of caracal in relation to prey density

Two male and three female caracal Felis caracal were radio-tracked over a 1-year period in arid shrub on the west coast of South Africa, by day and night over at least 130 days for each caracal, and uninterrupted for up to 120 h at a time. These results, on short-term use of space, were related to concurrent availability of prey. The use by caracal of specific plant communities showed a significant positive correlation to prey biomass of rodents. Males had much larger home-ranges (26.9±0.75 km²) than females (7.39±1.68 km²). Male home-ranges overlapped completely with those of females, whereas female ranges overlapped between 0 and 19%. Caracal were active by night and day; onset of activity was affected more by ambient temperature (T_A) than photoperiod. Caracal were active significantly longer on nights colder than 20°C. Females ceased activity at T_A > 20°C, males at T_A > 22°C. Males foraged faster than females (667 vs. 312 m h⁻¹) and moved more than twice the distance of females during an active period. Calculated density of caracal was between 0.23 and 0.47 km⁻².     

The form of the curves: a direct evaluation of MacArthur & Wilson's classic theory

1. We calculate the yearly numbers of bird species immigrating to – and becoming extinct on – 13 small islands of the British Isles, using a long and relatively complete data record.
2. We estimate the size of the colonist pool for each island using four methods.
3. We assume that immigrations and extinctions are distributed binomially, and use a maximum likelihood method to fit concave immigration and extinction functions to the data, utilizing all four species pool estimates.
4. Extinction rates increase significantly and consistently with increasing numbers of breeding species on each island. For nine of the 13 islands the extinction functions are significantly concave.
5. Immigration rates decrease consistently with increasing numbers of breeding species on each island. Seven islands have significantly concave immigration functions.
6. Immigration rates and extinction rates decline consistently, but not significantly, with island distance and island size, respectively. The number of breeding species does not always reflect the number of species likely to have reached an island. Moreover, some species may choose not to breed when their chance of extinction is high. These factors, plus the modest range of island areas and distances in our database, reduce our chances of finding the theoretically predicted effects of area and distance on extinction and immigration rates.     

Effects of eugregarine parasites on adult longevity in the polymorphic damselfly Mnais costalis Selys

Abstract.  1. The relationship between the abundance of midgut parasites (eugregarine trophozooites) and the survival of hosts (field-collected damselflies, Mnais costalis ) was investigated under laboratory conditions.
2. Males of M. costalis are morphologically and behaviourally polymorphic, typically existing as clear-winged non-territorial sneaks and orange-winged territorial fighters (the latter are larger in size). The survival cost of eugregarine infection for the two morphs was compared.
3. Orange-winged males showed shorter longevity compared to clear-winged males when they were fed at levels lower than the natural feeding rate, or when they were deprived of food. In contrast, morph longevity did not differ when they were fed until satiation every day.
4. Within each morph, the survival of damselflies was negatively correlated with the parasite abundance except when damselflies were fed until satiation.
5. The results suggest that the abundance of eugregarine parasites exerts a substantial cost, which is associated with the maintenance of alternative mating strategies, together with the higher developmental cost and energy expenditure of the fighter morph.     

Population growth rates of two closely related rotifer species: effects of food quantity, particle size, and nutritional quality

SUMMARY. 1. The relationship between population growth rates and the concentrations of several algal species was determined in laboratory experiments with the rotifers Brachionus rubens and B. calyciflorus .
2. The effects of food quantity were well described by a modified Monod model with a threshold for zero population growth. The model parameters depended on particle size and nutritional quality of the food algae. Differences between the rotifer species were significant and reflected their varying food-size preferences.
3. For each rotifer species, thresholds were lowest for algae in the most readily ingested size range. The lowest thresholds were 0.07–0.09 mgC 1⁻¹ with algae of about 5 μm equivalent spherical diameter (ESD) for B. rubens , and 0.19 mgC 1⁻¹ with algae of about 10 μm ESD for B. calyciflorus .
4. Maximal growth rates ( r _max) were slightly below 0.8 day⁻¹ for both rotifers with most algal species. The highest r _max values for both rotifers were observed when Cyclotella meneghiniana was provided as food. With this alga, B. calyciflorus had a significantly higher r_max (1.02 day⁻¹) than B. rubens (0.838 day⁻¹).
5. From a comparison of the relationship between growth rates and ingestion rates, Chlamydomonas reinhardii appeared to be of low nutritional quality for B. rubens .
6. Egg ratios were related to growth rate and were not influenced by the algal food used. Egg development times and average mortality rates were estimated from the relationship between egg ratio and growth rate. B. calyciflorus appeared to have a high average mortality rate (0.383 day⁻¹) compared to B. rubens (0.083 day⁻¹).     

Age, growth and reproduction of the barrelfish Hyperoglyphe perciformis (Mitchill) in the western North Atlantic

Otoliths ( n = 847) and gonads ( n = 817) were collected from barrelfish Hyperoglyphe perciformis that were captured by commercial fishermen in the waters off South Carolina and Georgia in 1995, 1997 and 2001–2006. Of the otoliths collected, 97% were aged successfully, and specimens sampled ranged from 5 to 85 years, with a median age of 12 years. The von Bertalanffy growth parameters yielded the equation: L_t = 857·8{1 − e^{−0·0985[ t −(−8·95)]}}, where L_t is fork length ( L _F) at time t . Through histological examination, 94% of the gonads assessed were assigned to a sex and reproductive class. Females spawned from September to May with a peak from November to January. Males spawned year round, but had a peak from September to April. The sex ratio (M:F) for this population was 1:1·34. The smallest mature female was 605 mm L _F and the youngest immature female was 697 mm L _F. Estimates of L _F and age at 50% maturity ( L ₅₀ and A ₅₀) for females were 660 mm L _F (95% CI = 633–667 mm L _F) and 6·08 years (95% CI = 3·50–7·27 years), respectively. The youngest mature male was 575 mm L _F and the oldest immature male was 762 mm L _F, and no estimates of L ₅₀ or A ₅₀ were made for males. It was determined that barrelfish exhibit the typical characteristics of long life span, slow growth and high age at maturity seen in other deepwater fishes, and that care should be taken to manage this species accordingly.     

The distances travelled by downstream-moving trout fry, Salmo trutta, in a Lake District stream

SUMMARY. 1. Field experiments were performed in the day and night at six modal water velocities (range 10–52cm s⁻¹), using: (i) newly- emerged fry without neutral buoyancy; (ii) older fry in poor condition (weight well below that expected for resident fry); (iii) older fry in good condition (weight similar to that of resident fry); (iv) dead fry.
2. An exponential model described the return rate of fry to the stream bottom; the mean distance travelled downstream varied considerably between the four fry categories, but always increased linearly with increasing water velocity.
3. Results were similar for dead fry and newly-emerged fry released at night; 50% of the fry returned to the bottom in 10–11 s and nearly all returned in c . 70s, the maximum distance travelled ranging from c . 7 m at 10 cm s⁻¹ to c . 37m at 52cm s⁻¹, Newly-emerged fry released in the day returned slightly faster (54s for 99% return to bottom).
4. Older fry in poor condition returned to the bottom slightly faster in the day than at night, but took about 2 min and travelled about twice the distance covered by dead fry. Older fry in good condition returned to the bottom at the fastest rate (3–6s for 50% and c . 30s for the rest), and travelled only about half (at night) or a third (in day) of the distance covered by dead fry.
5. The implications of this investigation are discussed and it is concluded that, apart from water velocity, the age and condition of the fry were the two most important factors affecting their downstream movement.     

Diurnal activity patterns in hoverflies (Diptera, Syrphidae)

Abstract. 1. Time-budgets are constructed from censuses of hoverflies. Larger species spend less time in flight.
2. Most species are active under similar conditions of light intensity, but a shade-tolerant (Melanostoma scalare Fabr.) and a sun-loving species (Metasyrphus corollae Fabr.) were identified.
3. Large species become active (i.e. move, by flying or feeding) at lower temperatures than small ones, except M.scalare, which is tolerant to cool temperatures. This means that, M.scalare apart, the order of species appearing during the day is size-dependent, largest first.
4. Previous claims about the diel periodicity of syrphids can be reconciled by considering the importance of individual thermal balance.
5. Tolerance to low temperatures in small hoverflies is associated with feeding on anemophilous pollen; this may indicate a proline-fuelled flight.     

Diel abundance, migration and feeding of fish larvae (Eleotridae) in a floodplain billabong

Eleotrid larvae (2.1–16 mm) were collected from surface waters of a billabong in south-eastern Australia. Estimates of larval density in plankton net samples at night averaged 148.3 larvae per m³ and 16.6 larvae per m³ during the day. In contrast, pump samples provided density estimates of 8.3 larvae per m³ at night and 0.9 larvae per m³ during the day. Larval densities did not differ between open water, snag (fallen tree) and Typha habitats, but Typha habitats yielded larger larvae than other habitats. 32.9% of larvae in pump samples were damaged and unmeasurable, creating a bias favouring larger larvae. The modal length of larvae in net samples at night was 5–6 mm, compared with 3–4 mm during the day, reflecting both greater net avoidance by larger larvae during the daytime and dispersal of smaller larvae from the surface at night. Dispersion patterns of larvae suggest that classes of larvae smaller than, and larger than 5.0 mm exhibit reciprocal diel vertical migration behaviour linked to ontogenetic changes in diet. Larvae less than 5 mm fed only during the day and preyed exclusively on rotifers, whereas larger larvae continued to feed at night and consumed mostly planktonic crustaceans.     

Growth, diet and condition of corkwing wrasse and rock cook on the west coast of Scotland

A study of seasonal and sexual variations of growth, diet, somatic condition ( K _S), gonadosomatic condition (GSI) and hepatosomatic condition (HSI) of corkwing wrasse Crenilabrus melops (L.), and rock cook Centrolabrus exoletus was made on specimens taken from areas on the west coast of Scotland from May 1992 to February 1994. Capture throughout the year was by baited creel, 3-m beam trawl, fyke net or by anaesthetics applied underwater. Corkwing ranged in size from 31–212 mm and 0.3–131.2 g for males, and 31–203 mm and 0.3–103–5 g for females. Maximum corkwing ages were 6+ years for males, 7+ years for females. Male rock cook ranged in size from 43–165 mm, weighed 0.7–56–5 g, and had a maximum age of 8+ years; females ranged in size from 43–138 mm, weighed 0.7–39.3 g, and had a maximum age of 4+ years. Male growth rates were faster for both species. Male and female corkwing had low K_S values during the period of high GSI values; the trends for rock cook K _S values were more variable, but levels increased after the reproductive period. Maximum GSI values were 11.37 and 18.94 for male and female corkwing respectively, 9.63 and 16.63 for male and female rock cook. There was no seasonal HSI fluctuation for male corkwing, levels were higher during the reproductive period for female corkwing and male rock cook, lower during the same period for female rock cook. The diets of corkwing and rock cook were both dependent on epibenthos. Corkwing diet was dominated by gastropod molluscs. The management of sustainable fisheries for corkwing and rock cook is discussed in relation to the growth rates of the two species.