Hatching Pattern Research Articles

Hatching controlled by the circatidal clock, and the role of the medulla terminalis in the optic peduncle of the eyestalk, in an estuarine crab Sesarma haematocheir.

Embryos attached to the female crab Sesarma haematocheir hatch synchronously within 1 h. Hatching is also synchronized near the time of the expected nocturnal high tide. These events are governed by a single circatidal clock (or pacemaker) in the female crab. The present study examined the role of the optic peduncle of the eyestalk on hatching and hatching synchrony. Surgery was performed either from the tip of the eyestalk [to remove the region of the optic peduncle from the compound eye-retina complex to the medulla interna (MI)] or from a small triangle 'window' opened on the eyestalk exoskeleton [to create lesions on the medulla terminalis (MT) of the optic peduncle]. Neither hatching nor hatching synchrony was affected by removal of the region of the optic peduncle from the compound eye-retina complex to the MI: the circatidal rhythm also remained. Removal of the MI probably caused damage to the sinus gland and the bundle of axons running from the sinus gland to the X organ. Nevertheless, maintenance of highly synchronized hatching indicates that the X organ-sinus gland system is not related to hatching. Hatching and hatching synchrony were not affected by dorsal-half cuts of the MT: the timing of hatching was not affected either. By contrast, transverse and ventral-half cuts of the MT caused severe damage to most females; hatching of many females was suppressed, while hatching of some females was either periodic, at intervals of approximately 24 h, or arrhythmic for a few days. The bundle of neuronal axons is tangled in the MT, and the axons inducing hatching pass through the ventral half of the MT. Complete incision of these axon bundles may have suppressed hatching. Incomplete incision of the axon bundle or partial damage to the neurons may have caused periodic or arrhythmic patterns of hatching. There are two possible roles for MT in hatching. One possibility is that neurons in the MT only induce hatching under the control of the circatidal pacemaker located in a site somewhere other than the optic peduncle. Another possibility is that the circatidal pacemaker is actually present in the MT. The second possibility seems more plausible. Each embryo has a special 48-49.5 h developmental program for hatching. This program could be initiated by the circatidal pacemaker in the female, and hatching synchrony may also be enhanced by the same pacemaker.

Immune expression in a damselfly is related to time of season, not to fluctuating asymmetry or host size

Summary1. Variation in immune responsiveness within and among species is the subject of the emerging field of ecological immunology. The work reported here showed that individuals ofLestes forcipatusRambur differ in their likelihood of mounting immune responses, and in the magnitude of those responses, against a generalist ectoparasite, the water miteArrenurus planusMarshall.2. Immune responses took the form of melanotic encapsulation of mite feeding tubes, occurred in the few days after host emergence, and resulted in mites dying without engorging. Such immune responses were more probable and stronger for hosts sampled later rather than earlier in the season. Such responses may act as selection affecting seasonal patterns of egg hatching and larval abundance of mites.3. Contrary to expectation, metrics of host size (wing length) and wing cell fluctuating asymmetry were not related to the likelihood of immune responses.4. The importance of season on immune expression of insects has not been explored in detail. These results suggest possible trade‐offs in allocation of melanin (or its precursors) to maturation versus immunity, and indicate the need for studies on the synergistic effects of weather and parasitism on host species that use melanotic encapsulation to combat parasites and pathogens.

Co‐evolution between ectoparasites and their insect hosts: a simulation study of a damselfly–water mite interaction

Summary1. A simulation model investigating the co‐evolution of water mites infesting their aquatic insect hosts during emergence is presented. The model is based on field and experimental studies of the ectoparasitic water mite Arrenurus cuspidator and the damselfly Coenagrion puella.2. Three scenarios were studied: (1) Only the host was allowed to evolve timing of emergence, while the timing of the parasites' infestation opportunity was held constant. (2) Both host and parasite were allowed to evolve. (3) Only the parasite's timing was allowed to evolve, while the host was constrained completely.3. In the first two scenarios, parasite abundances decreased in the course of evolution and reached values well below those found in the field, whereas in the third scenario, parasite abundances were maintained at a level close to that found in the field. In the second scenario (co‐evolution), the host seemed to be the leader in the evolutionary race.4. It is concluded that water mite parasitism is capable of shaping emergence patterns in aquatic insects and, despite the same life‐cycle length for host and parasite, the parasite evolves fast enough to shape its hatching pattern to match the emergence pattern of its host.

How to hatch from an egg of great structural strength. A study of the Common Cuckoo

Brood parasitism represents a unique mode of avian reproduction that requires a number of adaptations. For example, to reduce chances of puncture ejection of their eggs by small hosts, brood parasites may have been selected for laying eggs of unusually great structural strength. However, great structural strength of eggshells should hinder hatching. The goals of our study were to establish if chicks of the Common Cuckoo Cuculus canorus have more difficulty with hatching out of their strong eggs than chicks of species with eggs of similar size, and whether they possess any mechanisms facilitating hatching. To achieve these goals, we compared hatching pattern and selected body characteristics of chicks of the Common Cuckoo with those of another altricial species with eggs of a similar size, the Great Reed Warbler Acrocephalus arundinaceus. Although the rate of pecking was similar in the two species, the Common Cuckoo chicks started pecking earlier in relation to their emergence and consequently required more time and a greater cumulative number of pecks for breaking open their eggs than did young Great Reed Warblers. The two species also differed with respect to the pattern of opening their shells; in contrast to the warbler chicks, which enlarged the original pip circularly, the cuckoo chicks opened the egg by systematically creating a long narrow slit until they emerged. Finally, our study of hatched young revealed several differences; the Cuckoo hatchlings were significantly heavier, had a longer forearm, and their egg tooth was located significantly farther from the tip of the beak. The edge used for cutting through the shell was also significantly longer than that of hatchling Great Reed Warblers. To conclude, our data suggest that hatching is more difficult for a Cuckoo than for a Great Reed Warbler and that Cuckoos possess several mechanisms to overcome the problems of hatching from a structurally strong egg.

On the improvement of the stereolithography (SL) process

The successful control and operation of the stereolithograpy (SL) process depends on many parameters. These can be categorized systematically into: hardware, i.e., the construction and mode of operation of the machine; the controlling software such as the hatching pattern, error compensation and part orientation; and the material properties of the photo-polymer. The improvement of the current SL process is approached from both the software and hardware viewpoints. In the software study, the following issues are considered: (a) a correction table for compensating on the positioning accuracy; (b) STL slicing software with an editing and automatic error-correction function; (c) a direct slicing algorithm to be used on commercial CAD software; (d) the optimal part orientation software and (e) a variable slicing algorithm. For hardware and material studies, a novel process using a mixture of Aerosil silica powder and photo-polymer was developed. The resulting mixture not only reduces the requirement for support structures for the model hence shortening the model-building time, but also improves the properties of the model, such as tensile strength, shrinkage rate, etc.

Egg hatching in 3 species of monocotylid monogenean parasites from the shovelnose ray Rhinobatos typus at Heron Island, Australia.

Eggs of Neoheterocotyle rhinobatidis, Troglocephalus rhinobatidis and Merizocotyle icopae (Monogenea: Monocotylidae) from the shovelnose ray Rhinobatos typus (Rhinobatidae) have a distinct hatching pattern linked to light periodicity. Larvae of these 3 monogenean species emerge only during daylight when exposed to natural illumination or when incubated in alternating 12 h periods of light and dark (light on 06.00 h, light off 18.00 h). N. rhinobatidis larvae emerge with a distinct peak during the first 2 h of light; this peak is not as pronounced in T. rhinobatidis or M. icopae. Eggs of N. rhinobatidis incubated in a reverse light/dark cycle (light on 18.00 h, light off 06.00 h) hatched only during periods of illumination, again with a peak during the first 2 h of light. Evidence suggests that the hatching patterns observed in all 3 species represent true circadian rhythms because eggs incubated in 24 h light or 24 h dark conditions continued to hatch with a rhythm. Shadows, disturbance and host tissue did not promote hatching in N. rhinobatidis or T. rhinobatidis but there were indications that host tissue may promote hatching in M. icopae. The hatching patterns observed are discussed with respect to their adaptive responses to host behaviour and predation pressure.

Timing of oviposition and reproductive skew in cobreeding female burying beetles (Nicrophorus vespilloides)

Burying beetles (genus Nicrophorus) are known for their elaborate parental care. Two or more conspecific females may reproduce on the same carcass, especially when the carcass is large. Here we present the results of experiments in which we observed patterns of larval hatching and parental care in unmanipulated cobreeders, manipulated hatching synchrony between cobreeders, and compared patterns of oviposition in cobreeding and single females. Our results show that in these cobreeding associations, one of the females may or may not monopolize the carcass during the period of larval hatching. We present evidence that in either case, infanticide based on temporal cues constitutes an important proximate mechanism underlying the observed reduction in average reproductive success in cobreeding females. Females with higher synchrony (i.e., greater overlap between their oviposition patterns) produce larger broods with lower reproductive skew. Cobreeding females oviposit later and less synchronously than single breeders. Such delayed oviposition may reduce the risk that a female’s larvae fall victim to cannibalistic acts committed by her cobreeder or maximize her own opportunity to selectively kill her cobreeder’s larvae. Key words: burying beetles, cannibalism, communal breeding, infanticide, kin recognition, Nicrophorus, parental care, reproductive competition, reproductive skew. [Behav Ecol 11:357–366 (2000)] R eproductive competition is ubiquitous among communally breeding animals. When several conspecific females share a breeding site, as is the case in some vertebrates (‘‘joint nesting’’ or ‘‘communal breeding’’) as well as in some primitively social or eusocial insects (polygyny), young in the communal nest may compete for food. In this situation, females may increase their individual reproductive success by destroying their cobreeders’ eggs or young while sparing their own. Such selective infanticide requires the perpetrator to discriminate between her own offspring and those of cobreeders. One simple mechanism that can enable such discrimination is a temporal switch (Elwood, 1994), sometimes referred to as a ‘‘change in parental state’’ (Rosenblatt and Siegel, 1983), which is possibly mediated by hormonal changes triggered by important reproductive events (‘‘state-dependent cues’’; Elwood, 1991). Selective infanticide may result if the individual shows infanticidal behavior toward young at a time at which it is likely to encounter unrelated offspring, and parental, non-infanticidal behavior at a time when it is likely to encounter its own (Elwood, 1994). Examples include many bird species with intraspecific brood parasitism or communal breeding, in which females remove eggs from the nest throughout the prelaying period (i.e., until they have laid their first egg) (e.g., Emlen and Wrege, 1986; Macedo and Bianchi, 1997; Moller, 1987; Mumme et al., 1983; Stouffer et al., 1987; Vehrencamp, 1977), and males of many mammalian species that exhibit infanticidal behavior toward the young of females with whom they have not mated or cohabited long enough for the young to be the males’ own offspring (see Hrdy and Hausfater, 1984,

Sex-Biased Nestling Mortality Is Influenced by Hatching Asynchrony in the Lesser Black-Backed Gull Larus fuscus

Many birds hatch their eggs asynchronously while other species are more synchronous. Different hatching patterns may produce different sex-ratios through sex-biased chick mortality, but the relationship between sex-ratios and hatching pattern has received little attention. An extreme food shortage in a Lesser Blackbacked Gull colony allowed us to examine the timing of mortality of nestlings relative to sex and to hatching order. This was carried out in experimentally-created synchronous and asynchronous broods, where the latter mimicked the normal hatching spread. Unambiguous sexing was facilitated by use of molecular methods. In asynchronous broods, last-hatched female chicks survived significantly longer than last-hatched male chicks, whilst the males significantly out-lived the females among the earlier-hatched chicks. There was no difference in survival time of the sexes in synchronous broods. This suggests that chick sex-ratio is, at least partly, a function of asynchrony. Production of skewed sex-ratios via sex-biased mortality should be considered when evaluating the merits of asynchrony and synchrony.

Do males and females differ in the feeding of large and small siblings? An experiment with the bluethroat

Males and females have been reported to diAer in their feeding of large and small siblings in several species of birds. According to recent hypotheses, this phenomenon may be related to a sexual conflict over avian hatching patterns. We designed an experiment to test for the existence of such a sex diAerence by ma- nipulating nestling size hierarchies of the bluethroat (Luscinia s. svecica) in two directions; half the broods were ''asynchronized'' to yield large size-diAerences within broods and the other half were ''synchronized'' to yield small size-diAerences. In all broods, nestlings were cate- gorized as being either large or small according to body mass. We recorded male and female food distribution by video early (day 4 after hatching) and late (day 8) in the nestling period. Males and females did not diAer in their distribution of food among diAerent-sized nestlings. With large size-diAerences, both males and females fed large nestlings nearly twice as often as small ones. In contrast, when the size-diAerences were small, food was more evenly distributed among nestlings. Early in the nestling period, males fed more nestlings during each feeding visit than did females. Our finding that male and female bluethroats do not diAer in the feeding of large and small siblings is in contrast to most previous studies. Variation in costs and benefits to males and females from feeding diAerent-sized nestlings, and restrictions to parental choice due to nes- tling interactions, may explain interspecific variation.

HATCHING ASYNCHRONY IN GREAT TITS: A BET-HEDGING STRATEGY?

Previous studies have shown that asynchronous hatching in birds tends to result in fewer, but higher quality, offspring than does synchronous hatching. However, very few studies have considered the consequences of such a pattern for the recruitment of offspring as subsequent breeders. We recorded nestling survival and fledgling body mass in experimentally synchronous and asynchronous broods of the Great Tit, Parus major. Using six different juvenile survival models, taken from published studies of the species, we calculated the expected number of offspring recruited with each hatching pattern and survival function. The sex of fledglings was included in the analysis. When comparing the estimates of surviving juveniles between synchronous and asynchronous broods, we found no significant difference in the means with any of the six models. However, the distributions of recruitment were different: the expected number of recruits was more variable with synchrony than with asynchrony. This suggests that hatching asynchrony in the Great Tit may serve as a bet-hedging strategy. A larger proportion of asynchronous broods than of the synchronous broods experienced brood reduction, but fledgling body masses for the reduced synchronous broods were lower than those for the reduced asynchronous broods. This suggests that synchronous hatching inhibits adaptive brood reduction in the Great Tit. There was considerable individual variation in the level of brood reduction within the same area and season. We argue that conditions also may be unpredictable at a small scale (parental abilities, territory quality, or parasite load). In consequence, high-quality parents may benefit from synchrony, but low-quality parents benefit from asynchrony, within the same year.

A system to understand hand-drawn floor plans using subgraph isomorphism and Hough transform

Presently, man-machine interface development is a widespread research activity. A system to understand hand drawn architectural drawings in a CAD environment is presented in this paper. To understand a document, we have to identify its building elements and their structural properties. An attributed graph structure is chosen as a symbolic representation of the input document and the patterns to recognize in it. An inexact subgraph isomorphism procedure using relaxation labeling techniques is performed. In this paper we focus on how to speed up the matching. There is a building element, the walls, characterized by a hatching pattern. Using a straight line Hough transform (SLHT)-based method, we recognize this pattern, characterized by parallel straight lines, and remove from the input graph the edges belonging to this pattern. The isomorphism is then applied to the remainder of the input graph. When all the building elements have been recognized, the document is redrawn, correcting the inaccurate strokes obtained from a hand-drawn input.

Planktivorous fishes as selective agents for reproductive synchrony

Most shallow-water crabs release larvae during nocturnal maximum amplitude high tides, when larvae are rapidly transported by strong ebb tides to deeper waters at night. Larvae released at this time may avoid being eaten by planktivorous fishes, which abound in shallow water and feed during the day. Eurypanopeus planus (Smith, 1869), Uca beebei (Crane, 1941) and Pachygrapsus transversus (Gibbes, 1850) live on the Pacific coast of Panama and often release larvae during the day. Eurypanopeus planus also releases larvae without regard to tidal amplitude. Unlike most crabs, larvae of these three species will encounter, not avoid, planktivorous fishes. The predator avoidance hypothesis predicts that these larvae should be relatively well protected from predation compared to larvae of species that are released when predators are avoided. We tested this prediction experimentally by exposing larvae of these species and the sympatric crab, Cataleptodius taboganus (Rathbun, 1912), which exhibits the common hatching pattern, to silversides, Membras gilberti an abundant diurnal planktivore that feeds where all species release larvae. The rank order of silversides' prey preferences matched that predicted from the timing of larval release. Larval vulnerabilities to predation were related to the apparent conspicuousness of larvae, which is determined by the color of yolk and chromatophores. A survey of 30 other species of crabs further indicates that conspicuously colored larvae are released when they best avoid predators and that inconspicuously colored larvae may be released at other times.

Lack's Brood Reduction Hypothesis and Avian Hatching Asynchrony: What's Next?

Forbes recently argued that extant attempts to test Lack's brood reduction hypothesis for asynchronous hatching were of limited value. He argued that the hypothesis had to be tested in a two-step process: first, by testing whether brood reduction is adaptive, second, by testing whether asynchrony pays, provided the first test is fulfilled. Here, we focus on how this protocol can be adopted in empirical work. First, we identify several theoretical limitations to Forbes's approach: (1) it is unclear whether the brood reduction threshold should be tested using synchronously or asynchronously hatched broods, (2) individuals are different and thus have individual brood reduction thresholds, and (3) unpredictability may occur at different levels. Second, we discuss a main practical difficulty in testing the brood reduction hypothesis, related to the fact that asynchrony may carry a cost when conditions are good. When this is the case, tests must be carried out under a wide range of conditions, and during many years. Such a testing programme may turn out an almost insuperable task and Lack's hypothesis may be practically untestable using the traditional approach of recording the quantity of fledglings. Instead, we suggest that focus in future research on the issue is turned to consequences of different hatching patterns with respect to offspring quality. Recent evidence suggests that asynchrony serves to ensure offspring quality instead of quantity (the Offspring Quality Assurance Hypothesis), and may also lead to less variable recruitment (bet-hedging).

From Tragedy to Triumph: Renesting in Ring-Billed Gulls

ABsTAcT.-When animals that provide parental care to offspring are faced with actual or potential failure during a breeding bout, the option to continue breeding is countered by the option to cut losses and forego reproduction until the next breeding season. In 1990, we recorded laying date and laying order of eggs in 51 Ring-billed Gull (Larus delawarensis) clutches prior to their total loss by flooding. Pairs remained on territory and produced new clutches following a refractory period of 11.6 ? SD of 1.9 days. Post-loss clutches were initiated synchronously (n = 51 clutches in four days; 89% of all clutches marked in the 7 x 7 m study plot) but mostly contained significantly fewer and lighter eggs than first clutches. We contrast incubation, hatching and chick survival patterns of these storm-delayed pairs in 1990 with patterns of early-, peak- and late-nesting pairs at the same colony in 1992. The incubation and within-clutch hatching patterns of post-loss clutches 1990 were most similar to those of late nesting pairs in 1992, yet these storm-delayed pairs realized a fledging success similar to that of early-and peak-nesting pairs in 1992. We discuss larid reproductive strategies in the context of conditions that favor successful renesting. Received 22 August 1994, accepted 27 January 1995.

A comparison of the adult and miracidial stages of Echinostoma paraensei and E. caproni

Adult Echinostoma paraensei and Echinostoma caproni were grown in outbred mice and golden hamsters to compare size, growth rates, infectivity, and habitat selection. Antagonistic responses between the 2 species were investigated by concurrent infections in mice. Miracidial stages were compared for developmental stages, hatching responses, and behaviour to light and gravity. Size differences and growth rates were significantly different in both mice and hamsters. Mice proved to be better hosts for E. caproni and hamsters for E. paraensei. In mature infections, E. paraensei adults localized in the duodenum and E. caproni in the ileum of both mice and hamsters. In concurrent infections of mice, E. paraensei adults were significantly smaller than in single species infections beyond 14 days post-infection, while E. caproni adults were either equal to or larger than those in single species infections. On the other hand, E. paraensei were recovered in larger numbers in concurrent infections than in single species infections, while the reverse was found for infectivity of E. caproni adults. Miracidia of E. paraensei developed at the same rate as those of E. caproni in both light and dark cultures, but E. paraensei hatched much sooner when exposed to light. No miracidia hatched from cultures kept in the dark, indicating light is needed to stimulate the hatching process. All light-stimulated cultures exhibited a circadian hatching pattern from 1100 to 1600 hours. Cultures maintained in the dark past 11 days did not hatch when exposed to light. Miracidia of E. paraensei showed a positive phototaxis but no response to gravity. This comparison of life cycle stages leads us to conclude that E. paraensei and E. caproni are distinct species.

Evolutionarily stable seasonal timing for insects with competition for renewable resource

I study the evolutionarily stable seasonal patterns of hatching and pupation for herbivorous insects that engage in exploitative competition for a renewable resource. A longer larval feeding period enhances female fecundity, but also causes a higher mortality by predation and parasitism. Previously, it was shown that the evolutionarily stable population exhibits asynchronous starting and ending of the larval feeding period in a model in which larval growth rate decreases with the total larval biomass in the population due presumably to interference competition. Here I study the case in which resource availability changes not only with environmental seasonality but with the depletion by the feeding of larvae. I find that if the impact of the herbivory is strong, both hatching and pupation should occur asynchronously in the evolutionarily stable population. And if the favourable season for the host plant is short the ESS population may include synchronous timing of pupation. If the timing of hatching and pupation occurs asynchronously, in the first day of each interval some fraction of the population hatch or pupate, respectively and the rest do so gradually over the interval. In addition, if the environmental variable changes as a symmetric function of time, the length of the period in which hatching occurs tends to be much shorter than the period in which pupation occurs.

Advantages of Hatching Synchrony in the Pied Flycatcher Ficedula hypoleuca

Many bird species begin incubation before the clutch is complete, which leads to asynchronous hatching of the young. Several hypotheses have been proposed to explain this hatching pattern, most of them assuming that asynchronous hatching is of adaptive value. Pied Flycatcher broods were induced to hatch either synchronously or asynchronously in order to compare the breeding success resulting from these two hatching patterns. Experimental maximization of hatching synchrony led to an increase in the production of young. Synchronously hatched young also had longer tarsi and higher fledging weights than young from asynchronous broods. Synchronous hatching was favourable in both years of study, even though one was cold and rainy and the other warm and dry. Survivors in asynchronous broods in which some mortality had occurred were not in better condition than young in synchronous and unreduced broods, in contrast to what the brood reduction hypothesis predicts. Thus, this study does not support Lack's (1947, 1954) original presentation of this hypothesis as an explanation for the presence of the semi-asynchronous hatching pattern occurring naturally in Pied Flycatchers. However, the raising of experimentally synchronous broods might induce a larger parental effort perhaps affecting parental survival probability or subsequent fecundity. It is not possible to decide whether the absence of complete synchrony in the Pied Flycatcher is due to hormonal constraints, or whether some factor, such as predation on the nest contents (eggs, young or adults), may also make hatching asynchrony adaptive.

Incubation Behaviour and Hatching Patterns in the American Kestrel Falco sparverius

Asynchronous hatching within clutches is a pervasive phenomenon in altricial birds and the subject of considerable controversy. Intraspecific variation in the degree of hatching asynchrony is usually assumed to be the product of individual differences in parental incubation behaviour, yet few studies have reported on how variable such behaviour might be or the patterns of hatching within clutches. Wild American Kestrels in northern Saskatchewan started incubating their eggs prior to clutch completion, but the timing of the onset of incubation varied among pairs. There was considerable variation in the number of eggs to hatch per day within clutches. Many patterns of hatching could not be explained by conventional thinking about parental incubation behaviour, for the order in which eggs hatched was often not the order in which the eggs were laid. Small females were more likely to have such irregular hatching patterns and have hatching failures than large females, possibly because of problems in effectively covering all eggs during incubation.

An Experimental Test of the Brood-Reduction Hypothesis in European Starlings

An Experimental Test of the Brood-Reduction Hypothesis in European Starlings

Development of the Xenopus laevis hatching gland and its relationship to surface ectoderm patterning

An antibody that recognizes tyrosine hydroxylase can be used as a marker for hatching gland cells in Xenopus embryos. Using this marker, we have shown that hatching gland cells are induced at the end of gastrulation and that presumptive hatching gland cells are localized to the anterior neural folds in Xenopus. The movements of neurulation bring the hatching gland cells together to form a characteristic Y pattern on the dorsoanterior surface of the head. The Y pattern delineates several zones of surface ectoderm which can be visualized by the presence or absence of ciliated cells. As development proceeds the hatching gland pattern is altered, demonstrating the active changes involved in forming the face. Lithium, UV irradiation and retinoic acid can be used to alter the hatching gland pattern in specific ways which help to understand the underlying mechanisms of ectodermal patterning.