Evolution of complex life cycles in trophically transmitted helminths. II. How do life‐history stages adapt to their hosts?

We review how trophically transmitted helminths adapt to the special problems associated with successive hosts in complex cycles. In intermediate hosts, larvae typically show growth arrest at larval maturity (GALM). Theoretical models indicate that optimization of size at GALM requires larval mortality rate to increase with time between infection and GALM: low larval growth or paratenicity (no growth) arises from unfavourable growth and mortality rates in the intermediate host and low transmission rates to the definitive host. Reverse conditions favour high GALM size or continuous growth. Some support is found for these predictions. Intermediate host manipulation involves predation suppression (which decreases host vulnerability before the larva can establish in its next host) and predation enhancement (which increases host vulnerability after the larva can establish in its next host). Switches between suppression and enhancement suggest adaptive manipulation. Manipulation conflicts can occur between larvae of different ages/species a host individual. Larvae must usually develop to GALM before becoming infective to the next host, possibly due to trade‐offs, e.g. between growth/survival in the present host and infection ability for the next host. In definitive hosts, if mortality rate is constant, optimal growth before switching to reproduction is set by the growth/morality rate ratio. Rarely, no growth occurs in definitive hosts, predicted (with empirical support) when larval size on infection exceeds growth/mortality rate. Tissue migration patterns and residence sites may be explained by variations in growth/mortality rates between host gut and soma, migration costs and benefits of releasing eggs in the gut.     

Reproductive biology of the Suez Canal spider crab Schizophrys aspera (H. Milne Edwards, 1834: Crustacea: Brachyura: Majidae)

A reproductive biology study of the spider crab Schizophrys aspera (H. Milne Edwards, 1834) was conducted in the Suez Canal from July 2012 to June 2013. The annual sex ratio (Male:Female) of S. aspera was female biased with values of 1:1.25. Out of the four ovarian development stages of this crab, two stages were observed in the Suez Canal throughout the whole year. The ovigerous crab’s carapace width varied from 28 to 52 mm. This crab species can spawn during most of the year in the canal water, with a peak during late spring and early winter. The fecundity of ovigerous females ranged between 2349 and 13600 eggs with a mean of 5494 ± 1486 eggs. Female crabs that reached sexual maturity exhibited a minimum carapace width varying between 22 and 46 mm, and fifty percentage of all ovigerous females showed a carapace width of 36 mm.     

Additional moults into 'elongatus' males in laboratory-reared Polydesmus angustus Latzel, 1884 (Diplopoda, Polydesmida, Polydesmidae) - implications for taxonomy

The number of stadia during post-embryonic development is supposed to be fixed in most species of the millipede order Polydesmida. For the first time since 1928, additional moults were observed in two males of Polydesmus angustus Latzel, 1884 reared in the laboratory. These 'elongatus' males sensu Verhoeff reached stadium IX instead of stadium VIII, with addition of a further podous ring (32 pairs of legs). One male had well-developed gonopods at stadium VIII, which regressed at stadium IX; the other had no gonopods at stadium VIII, which developed at stadium IX. The two cases correspond to the 'regressionis' and 'progressionis' forms described by Verhoeff in Polydesmus complanatus (Linnaeus, 1761), which confirms entirely his results. Additional moults appear to be associated with small body sizes and possible underlying mechanisms are discussed. Comparisons between millipede orders indicate that post-embryonic development is less strictly canalized in Polydesmida than in Chordeumatida. This implies that the adult number of body rings is of limited taxonomic value in Polydesmida and should not be viewed as a character of generic importance.     

Dormancy and the influence of photoperiod and temperature on sexual maturity in Nicrophorus nepalensis (Coleoptera: Silphidae)

Abstract Carrion beetles (Nicrophorus spp.) use small vertebrate carcasses for food and reproduction. Their ecology and behaviors are highly affected by the availability of carcasses and the surrounding environmental conditions. Our results revealed that in subtropical Fushan, northern Taiwan, N. nepalensis was mainly active in spring (February to May), and could also be found in autumn (October and November); but there was no capture record in summer (June to September) and winter (December and January). A laboratory temperature tolerance study indicated that N. nepalensis adults become inactive at temperatures above 26°C, and had the highest mortality when the temperature was raised from 27°C to 28°C. Furthermore, N. nepalensis became sexually mature at 20°C, depending on the photoperiod: the longer the day, the lower the percentage of sexually mature 2‐week‐old females after emergence. In another experiment, N. nepalensis virgins were paired under three possible conditions at Fushan. At 15°C and 20°C, if carcasses were presented to the pairs within 3 days after emergence, all laid eggs in the second week after emergence. If carcasses were presented 1 week after emergence, most began to reproduce at 20°C with 12.5 h of daylight. However, at 15°C with 11 h of daylight, the carrion beetles hibernated first, and reproduced in the ninth week after emergence. At 25°C with 14 h of daylight, carrion beetles did not bury the mouse carcasses, the females did not lay eggs, and the adult lifespan was only one‐third of that at 20°C. This study revealed that both photoperiod and temperature influence the time needed to reach the sexual maturity of N. nepalensis; and also implied that the narrow temperature tolerance range and dormancy behavior of carrion beetles are highly regulated by those environmental factors.     

Growth, maturity and fecundity of wolffish Anarhichas lupus L. in Icelandic waters

Fecundity, maturity and the relationship between growth and maturity of common wolffish Anarhichas lupus were studied in Icelandic waters. A total of 788 female common wolffish were sampled in two areas: one in the relatively warm sea west of Iceland and the other in the colder sea east of Iceland. No difference was detected in fecundity of common wolffish between areas. The time from the onset of the cortical alveolus stage until spawning, was on average, 10 years in the east and 8 years in the west area. Common wolffish in the east area reached cortical alveolus stage, on average, at a greater age but similar size compared to common wolffish in the west area. Similarly, common wolffish started spawning, on average, at greater age and larger size in the east than in the west area. Common wolffish grew faster in the west than in the east area. Spawning common wolffish grew faster than common wolffish at the cortical alveolus stage in both areas. The relationship between growth and maturity for common wolffish in Icelandic waters appeared to be related to temperature, characterized by fast growth and early maturation in the west and slower growth and delayed maturation in the east.     

Female reproductive parameters in the Javan gibbon (Hylobates moloch)

Javan gibbons (Hylobates moloch) are one of the most endangered gibbon species in the world. Data on the reproductive biology of the species are almost nonexistent, and a general understanding of the female reproductive biology of this species is important for both ex situ and in situ conservation. Using 18 years of data from 11 captive individuals, we provide new information on the reproductive biology of Javan gibbons based on sexual swelling and menstrual bleeding, including reproductive development, interbirth intervals, and ovarian cycle lengths. Menarche and the onset of sexual swelling occurred at 6.2 and 6.5 years respectively, followed by a period of adolescent sterility of about 1.5 years. Average age at first birth was 8.8 years, and interbirth intervals were about 2.3 years, decreasing to 1.0 year during cases of infant mortality at or shortly after birth. Ovarian cyclicity was measured through periods between menstrual bleeding and sexual swelling. Menstrual bleeding indicates the start of a new ovarian cycle, while sexual swelling normally occurs near the time of ovulation. Menstrual bleeding intervals gave a cycle length of 25.6 days, while sexual swelling intervals gave a cycle length of 27.3 days. These both correspond closely to cycle lengths in other gibbon species, as well as hormonal studies in Javan gibbons. In particular, observing the presence/absence of swellings was found to be a useful and easy method to monitor female ovarian cycles, and could be a practical noninvasive technique for caretakers and researchers. Zoo Biol 29:449–456, 2010. © 2009 Wiley‐Liss, Inc.     

近红外光谱技术在水果成熟期预测中的应用(综述)

近红外光谱技术以快速、准确和多组分同步分析等优势,近年来在水果果实发育、成熟期预测和品质检测等方面应用广泛,并在果实品质无损检测分析技术研究方面取得重要进展。本文综述近红外光谱技术的基本原理和特点,分析近红外光谱技术在果实成熟期预测中的研究现状和存在问题,并提出今后研究方向。     

Selectivity Parameters and Size at First Maturity in Deep-Water Shrimps, Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816), from the North-Western Ionian Sea (Mediterranean Sea)

Selectivity experiments were carried out during trawling targeting deep-water shrimps Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816) (Crustacea, Decapoda, Aristeidae) in the North-Western Ionian Sea (Eastern-Central Mediterranean). Different criteria were employed to analyse maturity; however, the proportion at 50% of retained, mated and mature specimens was always used to indicate the size, expressed as Carapace Length (CL, mm), at first capture (CL_c), mating (CL_sp) and at first maturity (CL_m), respectively. In order to estimate the size at 50% maturity (CL_m) for females of both species, three criteria were adopted. In particular, CL_m was computed for the mature females not considering the presence of spermatophores, for the mature females with spermatophores and for the mature females intersected by the decreasing proportion with size of females without spermatophores. Three diamond stretched mesh codends of 40, 50 and 60 mm were tested using a cover of 20 mm. The 40-mm stretched mesh size (European Union legal size in the Mediterranean) was not selective for the sampled population of each species. The size at first capture (CL_c), calculated in both species for the two sexes combined, increased significantly with mesh size. Even for the mesh size of 60 mm, the size at first capture was still smaller than the sizes at 50% maturity, whatever the criterion adopted. Since the differences between the size at first maturity and the sizes at first capture are greater in A. foliacea than A. antennatus, the former species appears in this respect to be more vulnerable to trawling than the latter.     

Female teneral mating in a monandrous species

Schultesia nitor is a gregarious species living in Cacicus and Psarocolius ssp. pouch-like nests. Due to gregariousness, opportunities for multiple copulations in both sexes are not supposed to be restricted. Females produce only one brood during their life and die within a few days following the birth of their nymphs, but this unique brood could be the result of either single or multiple mating events (i.e., monandry vs. polyandry). In this study, we first determined the age of sexual receptivity of both males and females. Larval development in this species is shorter in males than in females and thus, this species is protandric. Males were not able to copulate the day after emergence. Contrary to males, teneral females (i.e., females achieving their imaginal molt but not yet fully sclerotised and colored) were attractive and were able to mate with males. In the second experiment, we tested the existence of multiple matings in both sexes. Our results showed that females were monandrous whereas males were polygynous. Since we had observed that females were monoandrous, we expected them to be choosy and we determined their ability to discriminate between virgin and nonvirgin males. When given the choice, females preferred virgin males and overall, they were more successful at mating than experienced ones. Our results suggest that monandry may be primarily driven by the female's short life-span fecundity. The occurrence of teneral mating in this species calls into question the existence of a male strategy for monopolizing females, and as well as the implication of female choice. Although further work is required, this species provides an interesting model for understanding sexual conflicts.     

有机肥和化肥配施对不同熟期大白菜土壤生物特性及产量品质的影响

以早熟和晚熟品种大白菜为试材,根据化肥氮(尿素)、有机肥氮(生物有机肥)配施比例设置4个施肥处理,测定不同施肥处理下不同熟期大白菜土壤酶活性、可培养微生物数量及产量、品质的变化特征.结果 表明:早熟品种'德高16'大白菜莲座期和结球紧实期均以配施1/2生物有机肥(T2)处理的土壤蔗糖酶、土壤脲酶、土壤过氧化氢酶活性较强...