Reproductive biology of Philodryas patagoniensis (Snakes: Dipsadidae) in south Brazil: male reproductive cycle

The male reproductive cycle of Philodryas patagoniensis in south Brazil was described through morpho‐anatomical and histological analysis of individuals deposited in zoological collections. Spermatogenesis occurred during late autumn–winter (June–September) and spermiogenesis occurred in spring–summer (October–March). The volume of the testes was smaller (quiescent) in winter, while the tubular diameter and the epithelial height of the seminiferous tubule were larger in summer (January–March). The ductus deferens presented spermatozoa all over the year and had no seasonal variation in diameter. The length of the kidney was larger in winter–spring (July–December), although the tubular diameter and epithelium height of the sexual segment of the kidney (SSK) were larger only in winter (July–September). Total testicular regression was observed in late autumn (May), simultaneously with the peak in SSK. Therefore, at the individual level, males exhibit a discontinuous cyclical reproduction. Considering the population level, the reproductive cycle is seasonal semisynchronous, with most of the individuals showing a reproductive peak in spring–summer (October–March). Here, we present evidence to support the importance of the microscopic approach to reproductive cycle studies. Finally, we discuss the intrinsic and extrinsic factors influencing P. patagoniensis reproductive patterns.     

Flowering seasonality and flower characteristics ofLoranthus acaciae Zucc. (Loranthaceae): Implications for advertisement and bird-pollination

The flowering biology and pollination ecology ofLoranthus acaciae was studied at Hazeva in the northern Arava Valley in Israel. Flowers at anthesis had red anthers, a red stigma and a green corolla which turned red as a postfloral phenomenon. Their flowering period was approximately 10 months long (from mid-June until mid-April) during which time two main flowering patterns were distinguished. Some plants flowered twice a year, with separate summer and winter flowering periods; other plants flowered continuously, with two peaks, one in the summer and one in the winter. Several significant differences between summer and winter flowering and fruiting were found: (1) the summer flowering period was shorter than that of winter, (2) flowering synchrony between individual plants was lower in summer than in winter, (3) in summer the plants produced a larger proportion of female flowers, whereas in winter most of the plants produced a larger proportion of hermaphrodites, (4) in summer a limited number of plants produced smaller flowers while the majority produced normal-sized flowers, whereas in winter the entire population produced only normal-sized flowers, and (5) fruit set percentage was lower in summer than in winter.L. acaciae was found to be self-compatible, but, since it was not spontaneously self-pollinated, it showed high dependence on pollinator activity. In summer the flowers were visited by a wide spectrum of pollinators, both birds and insects, while in winter flowers were visited almost exclusively by the orange-tufted sunbird (Nectarinia osea osea, Nectariniidae). These seasonal changes in flowering characteristics and pollinator activity could explain why reproductive success is higher in winter than in summer.     

Seasonal shifts in the life cycle of the ponto-caspian invader <Emphasis Type="Italic">Limnomysis benedeni</Emphasis> (Crustacea: Mysida): a physiological adaptation?

The mysid Limnomysis benedeni, one of the most important ponto-caspian invaders, was found in Lake Constance (southern Germany) in 2006. As part of larger studies to evaluate the effects of L. benedeni on the ecosystem, we studied its life-cycle strategies over an entire seasonal cycle in intervals of 3–5 weeks, addressing factors (predation, temperature) which we expected to be most important triggers of the observed changes. The size class distribution and the reproductive pattern indicated that the life cycle of L. benedeni changes seasonally. During winter (November to March), the mysid invested energy in growth and delayed reproduction until April, when the population was dominated by adults. In summer (June to September), the adults reproduced at a smaller body size and the population was disproportionately dominated by juveniles. In a mesocosm experiment that excluded fish predators, the mysids followed the same seasonal patterns of growth and energy investment as in the field population, but the size class distribution differed. Even in summer, the population in the mesocosm was dominated by adults. Stomach analyses of fish showed that L. benedeni is preyed upon by juvenile Perca fluviatilis, which fed size selectively on larger mysids. In conclusion, our results suggest predation was the reason for the dominance of juveniles and the observed size class distribution in summer. In contrast, the smaller adults in summer were most likely a physiological adaptation, perhaps evolved to avoid predation or as a reaction on metabolic losses at higher temperatures.     

The reproductive ecology and abundance of Symptevygia bonapavtii endemic to the south-west Atlantic

Logistical ogives gave an estimated L _T50 value (i.e. the total length at which 50% individuals are sexually mature) of 635 mm for female and 650 mm for male Sympterygia bonapartii . Mature individuals of both sexes had significantly larger livers than immature ones and females had a significantly heavier liver than males. Clasper elongation was the first step in male maturation, followed by clasper calcification and the development of alar thorns. In mature females, the right ovary was larger than the left, which was apparently due to differences in stroma tissue. Gonadosomatic index and diameter of ovarian follicles of mature females peaked in late spring and was at a minimum from late summer and through the winter. Juvenile S. bonapartii were more abundant near estuarine areas during winter, and adults appeared in estuaries by late spring and summer. Females carrying egg-cases were found near the shore in late spring and egg-cases were found in benthic samples only in shallow waters suggesting that S. bonapartii deposits egg-cases in shallow waters during late spring-summer and that nursery areas are in outer estuarine zones. In the southern part (38°–42° S) of the study area S. bonapartii showed a strong movement to shallow waters in late spring and summer, spreading over the entire coastal area in winter. These movements are discussed in relation to water temperature and trophic interactions.     

Reproductive biology of Psammobatis extenta

Psammobatis extenta collected from the commercial bottom trawl fishery operating in Puerto Quequén, Argentina, between 2000 and 2001, had a sex ratio of 1:1 (535 specimens). Both the largest male and female measured 313 mm total length ( L _T). The relationship between total body mass and L _T was significantly different between sexes; mature females weighed more than mature males for a given L _T. The size at which 50% of males were sexually mature was 262 mm L _T (83·6% of the maximum size), whereas 50% of females were mature at 249 mm L _T (80·0% of the maximum size). The gonadosomatic index in mature males and females was slightly higher during summer, but did not show significant variation over the sampling period. The hepatosomatic index of males and females was higher during the autumn and winter and followed a distinct seasonal pattern. Evidence suggested a continuous reproductive cycle during the year, with a maximum number of females carrying egg-cases in summer.     

Sex determination in the larvae of the parasitic barnacle Heterosaccus lunatus: an experimental approach

Heterosaccus lunatus parasitizes the portunid crab, Charybdis callianassa, in Moreton bay, Queensland, Australia. With the host crabs maintained at 25 °C this sacculinid rhizocephalan released larval broods every 5-6 days. This study examines the effect of photoperiod on the sex proportions of successive larval broods of individual parasites. Parasitized host crabs were maintained individually in circulating 25 °C seawater within two light-tight boxes, each with a controlled light-dark cycle operating. Box A had an LD 16:8 cycle (summer) and Box B an LD 8:16 cycle (winter). Both boxes had five host crabs and when parasites released their larval broods the larvae were flushed out and retained in a filter. Each captured brood then had its larvae sized to determine the proportions of the two sexes present. H. lunatus is ideal for such study because the sex(es) of all the larval stages (four naupliar stages and the cyprid) can be unequivocally identified by size (length). The experiment was run over a 6-week period during March and April 2004 when a total of 86 larval broods were released and their sex proportion(s) determined. It is concluded that larval sex determination is effected by photoperiod, with females becoming dominant under the winter condition (LD 8:16) and males dominant under the summer condition (LD 16:8). All initial broods were male dominated, so for Box A broods the male preponderance was maintained, whilst for Box B broods there was the progressive changeover to female preponderance. Such environmental sex determination is unusual because it is oogenesis which is being controlled, whereby two ovum sizes can be produced, either singly or together, the larger being the male egg. Further work is now necessary to verify the likely hormonal control processes involved.     

External factors determining seasonal breeding in a subtropical population of the shore crab Pachygrapsus transversus (Gibbes, 1850) (Brachyura,Grapsidae)

Summary

Monthly samples of the shore crab Pachygrapsus transversus from two distinct annual periods showed that ovigerous females are present throughout the year in the population. However, the relative ovigerous abundance of specimens among sexually mature changes from less than 10% during the winter months to almost 80% in summer. Linear correlations for each year revealed that both temperature and photoperiod were positively associated with relative abundance of ovigerous females. Multiple regression analyses suggested that photoperiod was the main factor affecting breeding in this species. Timing of observed reproductive pattern may enhance larval survival because of particular oceanographic conditions in the study region and favor early juvenile development due to certain species-specific growth features.     

Comparison of the life history strategies of three Dysdercus true bugs (Heteroptera: Pyrrhocoridae), with special reference to their seasonal host plant use

The life history strategy and seasonal host plant use of three Dysdercus bugs (D. cingulatus, D. poecilus and D. decussatus) were compared based on 2 years of twice monthly observations on Ishigaki‐jima Island (24°N, 124°E) in the southernmost part of Japan. Dysdercus poecilus reproduced almost year round, exclusively on Sida rhombifolia, which bears fruit and/or seeds almost year round. Dysdercus cingulatus reproduced successively on various malvaceous and bombacaceous plant species, according to their seasonal fruiting cycles. Its robust reproduction was observed on Hibiscus makinoi during winter months and on Chorisia speciosa and Bombax ceiba in early summer, whereas small‐scale reproduction was observed on various malvaceous plant species during the summer and autumn months. Dysdercus decussatus reproduced on Hibiscus tiliaceus and Thespesia populnea during the summer months, when these host plants bear abundant fruit and/or seeds, and its adults formed conspicuous aggregations without copulation on the underside of the leaves of those plants from November to the subsequent May. Each Dysdercus species showed a species‐specific life history strategy according to the differences in the phenology of their host plants.     

Rhipicephalus sanguineus: Observations on the parasitic stage on dogs in the Negev Desert of Israel

Sixteen dogs were studied for infestation with R. sanguineus in Kibbutz Ze'elim in the north-western part of the Negev Desert over a period of one year. The mean number of ticks per dog per month was 16.4. The majority of the ticks were adults: males (48.6%) and females (34.4%). The cars and abdomen of the dog were the predilection sites for the ticks. Male ticks were more abundant on the ears, whereas female ticks were more abundant on the ears and the abdomen. A strong correlation between tick numbers and the ambient temperatures was found. The mean percentage of dogs infested in the winter months was 16.6% and increased in the summer months to 34.4%. During winter, ticks were found more often on the ears and head of their hosts whereas in summer they were distributed mainly on the ears, headd and abdomen. The male: female ratio was higher in winter (2.3:1) than in summer (1.1:1).     

Locomotor Rhythms in the Fiddler Crab,Uca subcylindrica

The locomotor activities of individual specimens of Uca subcylindrica (Stimpson) collected from semi-arid, supratidal habitats in south Texas and northeastern Mexico were studied in the laboratory using periodogram analysis. When crabs were placed under constant darkness (DD) or constant illumination (LL), free-running circadian rhythms were observed in the activity recordings. The locomotor activity of strongly rhythmic crabs in LL has an average period length of 24.4 h. Crabs held in DD express motor rhythms with periods of approximately 24.0 h. In LL the most common wave form for activity is unimodal, while under DD it is bimodal. Recordings under natural illumination (NL) revealed that both period length and the time of maximum activity (phasing) varied through the year. During winter months, the crabs are primarily diurnal with peaks in activity occurring between 0900 and 2100 h and possess a circadian rhythm with a 23.9 h period. During summer, crabs were nocturnal with maximal activity between 1300 and 0600 and a circadian period closer to 24.0 h. In these experiments, the rhythmic locomotor activities of U. subcylindrica are best described as “circadian”. This is unusual for a genus known for its expression of circatidal and circalunidian rhythms.     

黄海中南部细纹狮子鱼的生物学特征及资源分布的季节变化

根据2009年7—8月、10月和2010年1月、5月黄海中南部渔业生物底拖网调查数据,对该海域细纹狮子鱼的生物学特征及其分布的季节变化作了分析。结果表明,细纹狮子鱼平均体长和平均体重从春季(4.7 cm、3.3 g)到冬季(34.2 cm、764.9 g)呈显著增加,并且雄性个体平均体长显著大于雌性个体(P<0.05,春季除外)。性比(♀∶♂)随体长组和季节变化,体长越大趋向于雄性,反之趋向于雌性;夏季雄鱼居多(0.70∶1,P<0.05),秋季则为雌鱼居多(1.35∶1,P<0.05),而冬季(产卵群体)和春季性比接近于1∶1。细纹狮子鱼各季节摄食等级均在2.5以上,冬季雄性个体摄食等级显著大于雌性个体(P<0.05),但雄性个体肥满度为全年最低(1.52)。细纹狮子鱼相对资源量和贡献率从春季(0.17 kg/h,1.54%)到秋季(15.36 kg/h,33.05%)呈上升状态,而冬季(2.37 kg/h,5.60%)有所下降。相比2000年,夏秋季相对渔获量和贡献率提高明显。全年集中分布于7.8—13.6℃,3.20%—3.38%的水域,平均体重和水深有显著的相关性(秋季除外)。另外,根据性成熟个体分布区和稚幼鱼分布的相关历史资料分析发现,除海州湾外,黄海中部深水区可能是细纹狮子鱼的产卵场。     

Reproductive biology of the Brazilian guitarfish,Pseudobatos horkelii (Müller & Henle, 1841) from southeastern Brazil,western South Atlantic

This study provides information on the seasonal occurrence, length‐width relationship, sexual development and size at first maturity of the critically endangered Brazilian guitarfish Pseudobatos horkelii in southeastern Brazil. Samples were obtained from September 2007 to August 2009 from commercial fisheries off São Paulo State coast at depths of 10–50 m, with net mesh sizes of 150 mm in the main net and 100 mm in the cod end. A total of 143 specimens (71 males, 72 females) were analyzed. Total length (TL), disc width (DW), sex and reproductive variables were recorded for each individual. Pseudobatos horkelii presents sexual dimorphism in length‐width relationships, with females attaining larger TL and DW. Females also mature at a larger TL, at 81.1% of the maximum TL, while males mature at 67.8% of the maximum TL. No specimens were captured in winter, and only a small sample size was observed in autumn. Males captured in spring and summer presented semen in the seminal vesicle, indicating that this species may reproduce in the warmer months, as already observed for other Rhinobatidae as well as for P. horkelii in southern Brazil.     

Bacterial Flora of the Hemolymph of the Blue Crab, Callinectes sapidus: Most Probable Numbers

The hemolymph of 290 freshly collected blue crabs from Chincoteague Bay, Va., was sampled over a 15-month period from August 1968 through November 1969 and most probable numbers of bacteria were determined by tube dilution. The hemolymph of 18% of all crabs sampled was found to be sterile, with 16% sterility in summer and 23% in winter samples. Despite individual variations, male crabs as a group had a higher bacterial hemolymph burden than females, and among both sexes summer counts were higher than winter. The hemolymph of crabs with missing appendages had significantly higher counts than uninjured crabs. The annual mean hemolymph most probable numbers per ml was 2,756 for males, 1,300 for females, and 1,876 for both sexes. The higher bacterial levels found in the hemolymph of male crabs may, in part, be explained by the fact that males, which predominated in the summer samples, had a higher incidence of injury and missing appendages than did females.     

Parental investment related to social systems in microtines

Summary Laboratory offspring of wild-caught voles Clethrionomys glareolus and Microtus agrestis, bred for 1 year under constant conditions, were examined with regard to sex ratios and weights at weaning and at 2 months of age. C. glareolus exhibits female territoriality and M. agrestis male territoriality in summer. The adults die away in late summer-autumn. Early-summer young mature in the year of birth but late-summer young do not reach maturity until the following year. C. glareolus young showed a male bias in early summer and a female bias in late summer. Conditions were the opposite but less clear in M. agrestis. C. glareolus males grew comparatively faster than M. agrestis males and showed a markedly higher early summer male: female weight ratio at 2 months of age. Maternal investment thus appears clearly related to the social system; the sex with the largest number and highest quality of young was that which was not limited in number by territoriality. However, the investment depended also on the time until maturation of the young.     

Growth and reproduction of Mesidotea entomon (Isopoda) in the northern Bothnian Sea

The life cycle of Mesidotea entomon sampled near the shore of Norrbyn in the northern Bothnian Sea, has been investigated. The species, a predacious brackish water isopod, had a three year life cycle. In May – June the juveniles were released from the female marsupium at a size of 3 mm. During the second summer size dimorphism became apparent, where the males were larger than the females. During the third summer and autumn the development of ova started in females. Maturation mostly occurred during late winter. Males matured before, and at larger sizes, than the females, 36.0 and 29.1 mm, respectively. The average fecundity was 153.2 and the females carried the eggs and embryos for several months before the release. Calculation of the survival rate for each year during the life-span revealed 0.05, 0.66 and 0.43, respectively.     

SOME OBSERVATIONS ON THE MALPIGHIAN TUBULES AND OVARIOLES IN MYRMECIA DISPAR (CLARK) (HYMENOPTERA: FORMICIDAE)

i
Myrmecia dispar (Clark) workers have a variable number of malpighian tubules; the number counted ranged from 21 to 29. The larger workers tend to have more tubules than smaller workers. Two male specimens had 16 tubules and 3 queen specimens had 23, 23 and 26 tubules respectively. Workers collected in winter and summer had 10 well developed polytrophic ovarioles while the queens had 18 ovarioles.     

High-resolution analysis of stem radius variations in black spruce [Picea mariana (Mill.) BSP] subjected to rain exclusion for three summers

Key message

A rain exclusion repeated for 3 years resulted in larger summer stem contractions in three of the sites in the third year of the experiment and in larger winter contractions in the northern sites. However, there was no pronounced stress reaction in the stem radius variations of mature black spruce since total stem expansion was not reduced.

Abstract

Future climate warming is expected to produce more severe and frequent periods of drought with consequent water stresses for boreal species. In this paper, we present a high-resolution analysis of stem radius variations in black spruce under rain exclusion. All summer long rain exclusions were applied for three consecutive summers to mature trees on four sites along a latitudinal gradient. The stem radius variations of control and treated trees were monitored year-round at an hourly resolution with automatic point dendrometers. The seasonal patterns of shrinking and swelling were analyzed using a sequential analysis technique and the daily patterns of contraction and expansion were extracted. Overall, the treated trees followed their diurnal cycles of contraction and expansion during the rain exclusions and no significant cumulative difference in stem expansion between control and treated trees was observed over the 3 years. In the third year trees subjected to rain exclusion showed larger stem contractions in summer on three out of four sites and larger winter contractions were observed on the northern sites. This study shows that repeated summer rain exclusion does not necessarily lead to a direct evident stress reaction, showing the resilience of the boreal forest.     

Early life history timings in marbled rockcod (Notothenia rossii) fingerlings from the South Shetland Islands as revealed by otolith microincrement

Although it has been reported that Notothenia rossii elsewhere hatches in spring, our daily increment back-counting from the capture date in otoliths of fingerlings caught in Potter Cove, South Shetland Islands, in the 2000s, showed two main periods of larval hatching, one in summer (February–March) and another in winter (July). In concordance, the simultaneous presence of two cohorts born the same year was identified in the age/length frequency distribution of fish sampled in spring 2010, which belonged to biological ages 0+ and 1+ and hatched, respectively, in summer and winter–spring. Maximum and minimum ages of pelagic blue-phase and demersal brown-phase fingerlings were, respectively, 227 and 240 days, indicating a demersal settlement after about 8 months from hatching. The estimated growth rate was 0.23–0.33 mm/day, equivalent to that of South Georgia fingerlings and higher than those of other nototheniids of similar size range. Based on early life events associated with the hatching periods, two types of life cycles are hypothesised for South Shetland fingerlings. The pelagic blue-phase fingerlings (6.5–7.6 cm TL, age group 0+) hatched in July (winter cohort), entering in Potter Cove in February–March. The brown-phase fingerlings (6.3–10.6 cm, mostly of age group 0+) hatched in February–March (summer cohort) and were collected in the cove in spring (the smaller specimens) or in summer (the larger ones). Finally, early juveniles (10.7–15.5 cm, age group 1+) hatched in winter, mainly in July (winter cohort), entering in the cove the following year to spend the second winter inshore.     

Annual cycle of zooplankton community in the Abra Harbour (Bay of Biscay): abundance, composition and size spectra

The annual cycle of the zooplankton community in a coastal embaymentof the Bay of Biscay was studied from data on zooplankton fractionslarger than 45 and 250 µm Smaller zooplankton and chlorophyllmaxima coincided in summer, while larger zooplankton reachedthe maximum in spring. Copepods dominated in both fractionsmost of the year, being copepod nauplii and postnaupliar stagesof Oithona nana and Paracalanus parvus the main constituentsof the microzooplankton maxima, and older copepodites and adultsof Acartw clausi of the meso-macrozooplankton maxima. Secondarypeaks of abundance due to protozoan blooms of Steno-semellanivalu, in early spring, and Noctiluca santillans, in summer,were also observed in smaller and larger fractions respectively.The collapse of phytoplankton biomass in early autumn was followedby a strong decrease of zooplankton in mid autumn. From thisperiod to winter, chlorophyll and zooplankton abundance showedsmall variations, but noticeable changes in the compositionand size spectra of zooplankton were observed. In winter, valuesof chlorophyll and zooplankton abundance reached minima, A.clausidominated the copepod assemblage and carnivorous zooplankterswere absent or negligible The annual development of the mainpredator populations (Sagitta frideria, Luiopc tetraphylla andanchovies) were found to be synchronized with the variationsin abundance and size spectra of zooplankton in the study area.     

The ectosymbiont crab Dissodactylus mellitae-sand dollar Mellita isometra relationship

The presence of the ectosymbiont Dissodactylus mellitae on Mellita isometra was studied at Tybee Island in Georgia. The number of crabs found on sand dollars, stage of maturity, sex, numbers of eggs, and size of eggs produced by crabs were noted. The test diameter of sand dollars, and the number and diameter of eggs produced were also noted. Infestation rates of crabs on sand dollars varied over time. The maximum number of crabs found on a sand dollar was 10. The three types of population dispersion, random, uniform, and clumped, were observed for crabs on sand dollars throughout the sampling period. Clumped or gregarious settling was observed when juvenile crabs were abundant, uniform and random distribution when mature crabs were abundant. Female crabs were significantly larger than male crabs, with carapace width of the largest mature female crab being 4.6 mm and the largest male 3.1 mm. Crabs produced between 80 and 300 eggs from 0.188 to 0.291 mm in diameter. Bigger crabs produced significantly more eggs than smaller crabs. Sand dollar sizes were 50-110 mm, with a mode between 60 and 70 mm. The effect of crab burden on egg production in the sand dollar was time-dependent. The presence of crabs on sand dollars correlated with total egg production of sand dollars in May, the peak of the spawning season, with sand dollars carrying one or two crabs having a lower egg production than those without crabs. Overall, variation in egg size was attributed to variation among females followed by variation between seasons and crab burden.