Larval sensory abilities and mechanisms of habitat selection of a coral reef fish during settlement

In most animals, siblings from a given reproductive event emerge over a very short period of time. In contrast, many species of birds hatch their young asynchronously over a period of days or weeks, handicapping last-hatched chicks with an age and size disadvantage. Numerous studies have examined the adaptive significance of this atypical hatching pattern, but few have attempted to explain the considerable intrapopulation variation that exists in hatching asynchrony. I explored proximate determinants of hatching asynchrony by monitoring 112 Burrowing Owl (Athene cunicularia) nests in the grasslands of southern Saskatchewan, Canada, over 4 years. Age disparities between first- and last-hatched siblings (i.e., hatching spans) varied considerably, ranging between 1 and 7 days (mode = 4 days). These hatching spans increased with increased hatching success. Hatching spans also increased with larger clutches, but the increase was less than predicted given the increased time required to lay more eggs. Hatching span was unrelated to number of prey cached in the nest during egg laying (an index of food availability), and was unaltered by a year of super-abundant prey. Furthermore, pairs given extra food during laying had hatching spans equal to those of unsupplemented control pairs. These results were inconsistent with both the energy constraint and facultative manipulation hypotheses, which predict that hatching asynchrony should vary with the level of food during laying, when incubation onset is determined. Burrowing Owls were apparently free of food limitation early in breeding, yet may not have been able to optimize hatching spans because food conditions during laying were largely unrelated to food conditions during brooding. Thus, one of the premises for facultative manipulation of hatching asynchrony—that laying females are able to forecast post-hatch food conditions—may not have been met for this population of Burrowing Owls.     

Fungal infection of sea turtle eggs in the sea turtle hatcheries in Peninsular Malaysia

Fungal infection in sea turtle nests has become a potential threat to sea turtle embryos. We screened the hatchery nest sand, eggshells of failed eggs, and stillbirths of green turtles and hawksbills collected from hatcheries in Malacca, Pahang, Perak and Terengganu for the presence of fungi. The DNA sequence of the ITS region of the three highest occurring isolated fungi confirmed that these species were Pseudallescheria ellipsoidea (35.4%), Scedosporium aurantiacum (27.2%), and Fusarium solani (22.0%). Morphological characteristics of these fungi were recorded. Although the total fungi abundance had no significant effect on hatching success (p > 0.05), the abundance of P. ellipsoidea significantly increased mortality in the nests (r = 0.70, p < 0.05). Future research should focus on understanding the biological aspects of this species to establish a more effective mitigation technique for the prevention of fungal infection of sea turtle eggs and hatchery employees.     

Expression of a zebrafish Cathepsin L gene in anterior mesendoderm and hatching gland

 During a differential display-based screen for developmentally regulated genes in zebrafish, we have isolated a cDNA for zebrafish cathepsin L, termed catL. The gene shows abundant expression in the anteriormost cells of the head process which give rise to the polster and later to the hatching gland. Expression of catL persists in these tissues until hatching. catL thus provides a useful marker for very anterior mesendodermal structures in zebrafish. Received: 23 September 1996/Accepted: 29 October 1996     

BIOMECHANICAL PROPERTIES OF DINOSAUR EGGSHELLS (Ⅲ)──THE MECHANIC ANALYSIS OF THE BABY DINOSAURS' EMERGING FROM THEIR EGGS

Thepurposeofthispaperistoanalyzethestressofdinosaureggshellloadedbythehatch1ingswhentheyhatch,andfourtypesofdinosaureggshellsareavaila-ble(seeTablelofZhaoeta1.,l994;TablelofMaandZhao,1994).Mostofthelivingreptileshaveflexible,parchment-likeeggshellscomposedoffibresandrelativelysma1lamountsofcalciumcarbonate.Thchatchlings,eachequ-ippedwithasmalI,sharp"eggtooth",cracktheireggshel1stoemerge'However,theyoungbirdspokeatthebluntendoftheeggwiththeirbeak,thenstruggleoutfromtheireggs.Thehatchingproce…     

Syphacia muris: response to environmental stimuli when hatching in vitro.

It is known that several oxyurids have hatched in fluids without extra stimuli except digestive enzymes, whereas the eggs of several other nematodes require for hatching optimal temperature, pH, redox potential, and pCO₂ but no enzymes. Consequently, a study was carried out on the effect of external stimuli on hatching of the eggs of the oxyurid Syphacia muris.Eggs of S. muris, attached to pieces of transparent adhesive tape, proved themselves able to hatch in a PO₄-buffer to which only trypsin and bile had been added. Trypsin acted, like NaOH on other nematode eggs, by dissolving proteins from the surface of the eggshell. The addition of reducing agents, and to some extent CO₂, had a stimulating effect. Hatching began to occur at 19 C and at pH 3, although 41 C and pH 7 gave optimal results.The conclusion is that the eggs of S. muris react in the same way to the environment as those of Ascaris lumbricoides and other nematodes which hatch inside the hosts' intestinal tracts. S. muris eggs distinguish themselves, however, by being dependent on the environment to an appreciably lesser extent.This last characteristic makes it possible to use simple media for routine hatchings of these eggs, for instance, in disinfection tests.     

台湾中部暗绿绣眼鸟的繁殖生物学

本研究将暗绿绣眼鸟 (Zosteropsjaponicasimplex)捕捉、套彩色环后释放 ,分别于 1999年和 2 0 0 1年 3～ 8月追踪监测 7对和 13对暗绿绣眼鸟的繁殖行为。总结此二年对 2 0对暗绿绣眼鸟的监测 ,其繁殖期始于 3月中旬 ,终止于 8月下旬。 1对最多可年产 5窝 ,但以 3～ 4窝为常见。初次筑巢所需时间平均为 10 4d ,筑第 2、3巢的时间依次减少 ;窝与窝之间的繁殖间隔视情况而定 ,如孵化或喂养失败 ,通常都在 1～ 2d内再筑巢 ,如繁殖育雏成功 ,平均相隔 7d再筑巢。 2年 6 3窝的窝卵数平均为 2 6 8± 0 71(n =6 3)枚 ;孵化期平均为 11±0 6 4 (n =4 7)d ;6 3窝孵化成功 4 7窝 ,孵化成功率为 74 6 % ;雏鸟离巢日龄平均为 10 5± 0 88(n =35 )d ;4 7窝雏鸟喂养成功 35窝 ,育雏成功率为 74 5 % ;6 3窝繁殖成功 35窝 ,繁殖成功率为 5 5 5 %。失败因素包括气候、动物掠食、人为破坏和其它不明原因     

Reproduction strategies of <Emphasis Type="Italic">Daphnia pulicaria</Emphasis> population in a high mountain lake of Southern Spain

For three consecutive years, a population study of Daphnia pulicaria was undertaken in Río Seco Lake, a small high-mountain lake, in order to elucidate the reproductive strategies adopted by Daphnia in this system. Daphnia appears to colonize this lake every spring by hatching from ephippia and reproduce by means of subitaneous (non-diapausing) and ephippial (diapausing) eggs. D. pulicaria in this lake is an obligate parthenogenetic population. There is a short time period for subitaneous egg production and a much longer period for ephippial egg production. The contribution of subitaneous eggs to Daphnia population density and structure appears to be low. Diapause onset showed a high temporal synchronization in the three studied years in Río Seco Lake, and day-length emerged as the main cue triggering diapause onset and the main explanatory factor for the proportion of ephippial females observed. The development and reproduction of D. pulicaria in Río Seco Lake involves taking a gamble on resting forms to guarantee inter-annual Daphnia persistence in the lake, giving priority to investment in future generations. Guest editor: Piet Spaak Cladocera: Proceedings of the 7th International Symposium on Cladocera     

The contribution of differential hatching success to the fitness of species and interspecific hybrids

Resting egg banks of microcrustaceans have been used to reconstruct the evolutionary and ecological history of species. However, recent studies provided evidence for a discrepancy between dormant propagules in the sediment and the planktonic population. This pattern raises two questions: First, what is the value of data on resting egg banks for population dynamics over time and second, which component of the reproductive cycle causes the observed inconsistency? In our study we focussed on the second question by comparing the taxon composition of a resting egg bank with the reproductive success of ex-ephippial hatchlings. Species and interspecific hybrid identification of dormant and hatched stages was achieved through the application of restriction fragment length polymorphism analysis of an internal transcribed spacer region. We found no significant deviation between the proportion of hatched Daphnia galeata, D. galeata × hyalina and D. hyalina individuals and the observed taxon composition of the resting egg bank. However, species and hybrids differed in their mode and relative success of reproduction. We conclude that the components of reproductive success in Daphnia contribute differentially to the fitness of species and interspecific hybrids. The discrepancy between resting egg banks and “active” planktonic populations results not from differential hatching of species but from the reproductive success of ex-ephippial females and the timing and frequency of sexual reproduction of the different taxa.     

Age and maturation of Loligo duvauceli and L. chinensis from Andaman Sea of Thailand

Estimated age, hatching date and sexual maturation were investigated for the loliginid squids Loligo duvauceli and L. chinensis, the commercially important neritic species in the Andaman Sea of Thailand. The specimens caught by commercial bottom-trawl in Phang-nga Bay and southern area off Phuket Island were obtained monthly from Phuket fish landing between April and August 2005. Age was estimated based on the counting of statolith increments from a total of 329 individuals of L. duvauceli (ML ranges from 41 to 224 mm) and 116 individuals of L. chinensis (ML ranges from 42 to 186 mm). The estimated age ranged from 41 to 161 and 67 to 158 days old for L. duvauceli and L. chinensis, respectively. The length–weight relationships differed among sexes and the sexual dimorphism was expressed as mature females having a greater body weight than males of the same length. Males showed a wide range of maturity size possibly because of the seasonal change in size at maturity. The results of the back calculation for the hatching date of individuals fell between November 2004 and June 2005 which suggests that L. duvauceli and L. chinensis hatch continuously and recruit to the fishing ground for a relatively short period with a shorter lifespan than expected.     

不同纬度洞巢鸟类对人工巢箱的利用及差异

迄今对洞巢鸟类生活史特征的纬度变异（特别是热带洞巢鸟类的繁殖）了解还十分有限。我们于2018年3至8月,分别在海南吊罗山（热带）、河南董寨（亚热带）和河北塞罕坝（温带）的林缘地带,悬挂相同规格的人工巢箱招引洞巢鸟类繁殖,用以比较不同地理区域的洞巢鸟类对人工巢箱的利用情况及其孵化成效和繁殖成功率。野外共悬挂577个木制巢箱,3个研究地的利用率在海南吊罗山为最低（32.6%）,河南董寨最高（92.0%）。3个地点均有大山雀（Parus cinereus）入住（占总巢数的84.3%）,其孵化成效和繁殖成功率在3个地点不存在显著差异（P > 0.05）。但在河北塞罕坝,大山雀的孵化成效（75.7%）和繁殖成功率（65.7%）显著低于同域繁殖的褐头山雀（Poecile montanus）（97.7% 和97.7%）和煤山雀（Periparus ater）（93.5%和90.3%）（P < 0.05）。研究表明,3个地理区域利用巢箱繁殖的洞巢鸟的种类、数量以及对巢箱的利用率均存在差异,但对于广布种大山雀来说,地理位置的差异并不影响其孵化成效和繁殖成功率。