Presence Of Egg Predators Research Articles

A tiny cuckoo: Risk‐dependent interspecific brood parasitism in a predatory mite

Abstract Many animal species protect their eggs against predators, and other species may profit from this by adding their eggs to those of the protecting species. We studied two tiny species of predatory mites that share a food source, are engaged in intraguild predation, and which eggs are attacked by the same egg predator. One of these predatory mites (Neoseiulus californicus) adds its eggs to those of the other species (Gynaeseius liturivorus) which guards its eggs from egg predators, resulting in reduced predation of the eggs of the nonguarding species. The guarding species experiences costs in the form of intraguild predation of her offspring, and the addition of eggs to the guarding species therefore qualifies as brood parasitism. In the presence of egg predators, the brood parasite preferentially adds its eggs to those of the guarding host species, not to those of another, nonguarding mite species. This cuckoo behaviour comes with a cost for the parasite when egg predators are absent, and therefore only occurs when egg predators are present. Our findings emphasize the importance of the risk of egg predation as a factor driving facultative brood parasitism. Read the free Plain Language Summary for this article on the Journal blog.

Offspring mortality factors and parental care efficiency of the spider Manogea porracea (Araneidae) in the Brazilian savanna

The expressions of parental care can vary in space and time because factors driving offspring mortality depend on variable abiotic and biotic conditions. Manogea porracea is a spider that exhibits biparental care and widespread distribution in the Neotropical region. Parents can protect their offspring against abiotic conditions that may damage their webs, or compromise their egg sacs, and against araneophagic spiders that prey on their eggs. However, the current knowledge of the parental care in the species is restricted to a population located in areas covered by Eucalyptus plantations. This study investigates parental care efficiency in a new ecological context, a protected area of Brazilian savanna. We described the substrates in which M. porracea built webs and the agents of egg mortality. We also performed a parent removal experiment to test the effect of parental care on the integrity of nursery webs, offspring survival, and the presence of egg predators. Spiders built webs at variable heights and many distinct substrates but were mainly associated with the bromeliad Ananas ananassoides. We found two previously reported egg predators, Faiditus caudatus and Argyrodes elevatus (Araneae Theridiidae), and a new one emerging from the egg sacs, the insect Zeugomantispa virescens (Neuroptera Mantispidae). The presence of parents in the webs of M. porracea prevented the webs from collapsing and effectively increased offspring survival. However, the occurrence of egg predators was not reduced by the presence of parents. Overall, parental care increased offspring survival in both populations, but variation in biotic and abiotic factors between areas influenced offspring mortality and the efficiency of parental behaviours. Our results emphasise the importance of investigating multiple populations in behavioural studies of parental care.

Spawning season and nest guarding behavior of invasive smallmouth bass (Micropterus dolomieu) in a Japanese Lake

AbstractSpawning of invasive smallmouth bass (Micropterus dolomieu) was studied in 2020 and 2021, in Lake Nojiri, Nagano, Japan. Male smallmouth bass began nest construction once water temperatures reached 14°C, and eggs progressed to fry dispersal in approximately 2 weeks. The main spawning season was in late May through early June, with a smaller second peak of nests in late June through early July. Nests were constructed primarily under dock cover, and nest size and depth were positively correlated with male body size. Of the nests that received eggs, nearly all progressed successfully to fry dispersal. Time lapse videos of male guarding behavior revealed that as nests progressed, males rotated less and were suspended off the bottom substrate. Similarly, the presence of egg predators was determined by experimental removal of guarding males. Freshwater gobies (Rhinogobius kurodai) were the only egg predators observed and arrived on all nests in the egg stage. However, only a handful of gobies visited each nest, the total number of eggs predated was low, and eggs or alevins in the progressed stage were rarely predated. These results indicate that in Lake Nojiri, smallmouth bass spawning is highly successful and egg predators appear to have minimal effect on egg survival. The stable smallmouth bass fishery without stocking at this lake is likely a product of these favorable spawning conditions. The lack of native egg predators may also be a driving factor in the continued spread of smallmouth bass throughout Japan.

Extremely short embryonic period of the intertidal pulmonate limpet Siphonaria sirius (Pilsbry, 1895)

ABSTRACT Siphonariidae is a panpulmonate family that occurs in intertidal rocky shores worldwide within temperate to tropical areas. Although the egg masses of Siphonaria sirius are commonly found in lower intertidal rocky shores in summer, there is a lack of information on their embryonic development. We examined the embryonic development and duration of S. sirius both in the laboratory and in the field. The study was conducted in Shirahama, Wakayama, Japan, during the summer of 2014 and 2015. The embryonic developmental process of S. sirius was similar to that of other planktotrophic siphonariids. However, S. sirius hatched within four days after oviposition at 27.35°C in the laboratory, which is the shortest in the Siphonariidae. In the field, hatching occurred notably faster at 1.6 days after oviposition, although the average temperature (27.42°C) was similar to that in the laboratory. The presence of egg predators, as well as other environmental factors, may be responsible for the short embryonic period of this species, especially in the field.

Preliminary survey of a nemertean crab egg predator, Carcinonemertes, on its host crab, Callinectesarcuatus (Decapoda, Portunidae) from Golfo de Nicoya, Pacific Costa Rica.

The possible presence of egg predators in brood masses of portunid crabs from Pacific Central America has not been studied yet. This survey reports the finding of a nemertean crab egg predator on the portunid crab, Callinectes arcuatus, from the Golfo de Nicoya, Pacific Costa Rica. Nemerteans were found in the egg masses of 26 out of the 74 crabs for a prevalence of 35%. The intensity (mean number of worms/ infected crab) was estimated to be 18 with a variance of 1–123 worms/infected crab. No nemerteans were observed either in the 19 Callinectes arcuatus from Golfo Dulce (southern Pacific coast) and the 10 Portunus asper from Herradura-Jaco (central Pacific coast). This nemertean is a member of the genus Carcinonemertes, which has been reported from the Caribbean coast of Panama. However, the encountered Carcinonemertes sp. is the first published finding and report from Costa Rica and Pacific Central America.

Effect of egg predator on nest choice and nest construction in sand gobies

Nest defence is a particularly costly component of parental care. The costs of nest-related behaviours are affected by the nest's location, size and architecture; yet surprisingly little is known about how choice of a nesting site or nest characteristics are adjusted as a response to the threat of future nest predation. To address this topic, we investigated whether egg predation threat influenced nest choice and nest construction in the sand goby, Pomatoschistus minutus, a small marine fish with exclusive paternal egg care. We found that exposure to sand shrimp, Crangon crangon, a predator of sand goby eggs, did not affect male preferences for large nesting resources or the onset of nest-building activity. Small and large males did, however, respond differently to the presence of shrimp during the nest-building phase. In particular, large males used more sand to cover their nests in the shrimps' presence. By contrast, neither the presence of egg predators nor male size class affected the size of the nest entrance. Together, our results show that while the risk of future egg predation may not necessarily influence a male's decision to nest, during the nest construction phase it can nevertheless induce responses that strongly depend on builder phenotype.

Should you eat your offspring before someone else does? Effect of an egg predator on filial cannibalism in the sand goby

Costs and benefits of parental care are expected to affect filial cannibalism. One factor that increases the costs and decreases the benefits of care is the presence of egg predators. In general, the effect of egg predators on filial cannibalism is unknown. Here, we examine the effect of an egg predator on filial cannibalism in the sand goby. Males caring for eggs were exposed to three treatments: no egg predator, visual cues from an egg predator, and chemical and visual cues from an egg predator. We hypothesized that the perceived benefits of providing care in the presence of an egg predator would be relatively low, and we expected filial cannibalism to increase in the presence of the egg predator, especially when both chemical and visual predator cues were present, as this might represent a greater threat. When both visual and chemical predator cues were present, whole-clutch cannibalism increased. In addition, larger males and males in poorer condition showed less whole-clutch cannibalism than smaller males or males in better condition. There was no effect of egg predator on partial-clutch cannibalism. However, males that engaged in partial-clutch cannibalism ate more of their eggs when the eggs were spawned by a female in relatively good condition, but a smaller proportion and number of eggs when only a single female spawned. In general, our findings suggest that male sand gobies are sensitive to the costs and benefits of care and are more likely to terminate care when the expected benefits are relatively low.

Plasticity of Hatching in Green Frogs (Rana clamitans) to Both Egg and Tadpole Predators

Abstract We examined whether embryos of the green frog (Rana clamitans) would adaptively alter hatching times in the presence of both egg predators (the crayfish Procambarus nigrocinctus) and tadpole predators (the dragon nymph Anax junius). Under laboratory conditions, we exposed eggs with developing embryos to four experimental treatments that varied in the type of caged predator: egg predator only, tadpole predator only, both predators together, or no predator. As predicted, the presence of an egg predator caused a significant reduction in time to hatching. However, contrary to our prediction, eggs also hatched sooner in the presence of a tadpole predator. Moreover, there was no significant interaction between the effects of the two predators and thus no evidence that R. clamitans embryos can distinguish between predator types. We also found significantly lower hatching success in the presence of an egg predator, despite the fact that the predator did not have direct contact with the eggs. These result...

RISK-INDUCED EARLY HATCHING IN SALMONIDS

Many ontogenetic niche shifts are phenotypically plastic and with their timing dependent on the perceived risks and benefits for the individual. In fish, hatching can be induced by oxygen shortage or the presence of egg predators or pathogens. However, little is known about the embryos' ability to avoid desiccation by hatching earlier. We simulated an increased risk by exposing some embryonated eggs to low water levels and compared them to control eggs kept deeper in the water. We tested eggs of arctic charr (Salvelinus alpinus), brown trout (Salmo trutta), and of small and large ecotypes of alpine whitefish (Coregonus sp.). During exposure, the apparently more risky environment induced higher rates of early hatching in all taxa tested. We suggest that the early hatching is either an adaptation of salmonids to risky environments or an accidental by-product that did not get counterselected because of its benefits to the fish larvae.

The net effects of guarding on egg survivorship in the flagfish, Jordanella floridae

We investigated the effects of male nest guarding on egg survival in the flagfish, a species in which paternal care is thought to be relatively recently evolved. Thus, we characterized the fitness consequences of a major component of paternal care when secondary adaptations to care are likely to be minimal. The effects of guarding under three predation regimes were examined by exposing eggs to treatments in which no predators, conspecific females, and conspecific females and the egg predator Gambusia affinis were present. These were crossed with the presence and absence of parental males. We expected that guarding would result in an increase in egg survival in the presence of egg predators, but considered that in their absence the benefit might be decreased or absent, as a result of filial cannibalism. We also examined effects on egg survivorship stemming from filial cannibalism and egg-directed components of care (i.e. cleaning and fanning); the effects of these behaviours were examined through treatments in which males had full access to eggs (i.e. complete care), males were separated from their eggs by a screen (i.e. egg fanning and no cannibalism), and males were absent (i.e. no care and no cannibalism). In accordance with our expectations, guarding increased egg survivorship in the presence of females and Gambusia. However, egg survivorship when males were alone with eggs was low. Indeed, significantly more eggs were eaten than became diseased, suggesting that males cannibalize healthy eggs. Neither fanning nor cleaning resulted in an increase in egg survivorship. Thus, in flagfish, there may be costs of care when predators are absent. We discuss our findings in relation to sexual selection and the early evolution of parental care.