Multiple Egg Batches Research Articles

Maternal Allocation of Lipids to Eggs by Southern Flounder after Diet Changes

AbstractMaturation and spawning diets for flatfish broodstock, such as Southern Flounder Paralichthys lethostigma, have received little research attention, despite their critical role in the reproductive performance. During the spawning season, which is when Southern Flounder broodstock produce multiple egg batches, they rely on their diet to supply nutrients to the eggs. Lipids are an important class of nutrients for offspring development. The objective of this brief communication is to describe the changes in egg lipid classes during the spawning season following a diet change. Female broodstock were fed three diets after the first spawn (week 0)—a control diet (equal weights of Spanish Sardines Sardinella aurita and brown shrimp Farfantepenaeus aztecus), a shrimp‐only diet, and a sardine‐only diet (n = 3, 3, and 4, respectively)—for a period of 6 weeks and the lipid composition of the eggs was measured every 2 weeks. The change to a diet of sardines only or shrimp only altered the concentrations of egg lipid classes, indicating that egg composition is affected by maternal dietary intake over a period of 2 weeks or less. Females that were fed the sardine‐only diet produced eggs with higher levels of ketones and acetone‐mobile polar lipids and lower levels of hydrocarbons than did females that were fed shrimp, exhibiting changes that were consistent with the differences between the diets. The shift to the sardine‐only diet had little effect on total lipids, triacylglycerols, free fatty acids, and sterols in the eggs. The change to the shrimp‐only diet resulted in subtle but consistent decreases in all of the lipids, except wax/steryl esters at week 2, followed by gradual increases. This suggests that the shrimp‐only diet provided insufficient nutrition and that the females mobilized stored lipids to compensate. These preliminary results revealed interesting patterns that, with further research, could lead to improved diets and feeding protocols for the production of Southern Flounder.

Comparative effects of temperature on rates of development and survival of eggs and yolk-sac larvae of Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus)

AbstractChanges in Arctic fish assemblages resulting from climate change will likely be determined by the differential thermal response of key species during their early life history. In this study, we incubated multiple batches of eggs and larvae of two ecologically important gadids co-occurring at the Pacific–Arctic interface, Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus). Fertilized egg batches (n = 11 Arctic cod; n = 6 walleye pollock) were collected in the late winter/early spring from laboratory broodstock held under simulated seasonal environmental conditions. Image and lipid analyses indicated that Arctic cod eggs and larvae were ∼25–35% larger than walleye pollock and had nearly 3–6× more energetic reserves. Two batches of eggs from each species were incubated in replicated containers (n = 3/batch/temperature) at −0.4, 1.2, 2.5, 3.8, 5.0, 9.0, and 12.0°C for Arctic cod and −0.8, 0.3, 2.2, 4.5, 9.0, and 12.0°C for walleye pollock. Both species had very similar low thermal tolerance, but Arctic cod were much more sensitive to higher thermal stress in terms of hatch success and size-at-hatch. For example, Arctic cod hatch success declined precipitously at temperatures above 3.5°C yet remained above 50% in walleye pollock at 9°C. Arctic cod also had significantly longer development times, such that embryos could survive for ∼4 months at temperatures <0°C from the time of spawning to first-feeding. Collectively, these results indicate Arctic cod have a much smaller thermal window for survival, but can survive for longer periods in the absence of food than walleye pollock at cold temperatures. These temperature-dependent rates will be useful in the development of population forecasts and biophysical transport models for these species in the northern Bering, Chukchi, and Beaufort seas.

Taxonomy and life history of the Acropora-eating flatworm Amakusaplana acroporae nov. sp. (Polycladida: Prosthiostomidae)

Efforts to culture and conserve acroporid corals in aquaria have led to the discovery of a corallivorous polyclad flatworm (known as AEFW – Acropora-eating flatworm), which, if not removed, can eat entire colonies. Live observations of the AEFW, whole mounts, serial histological sections and comparison of 28S rDNA sequences with other polyclads reveal that this is a new species belonging to the family Prosthiostomidae Lang, 1884 and previously monospecific genus Amakusaplana (Kato 1938). Amakusaplana acroporae is distinguished from Amakusaplana ohshimai by a different arrangement and number of eyes, a large seminal vesicle and dorsoventrally compressed shell gland pouch. Typical of the genus, A. acroporae, lacks a ventral sucker and has a small notch at the midline of the anterior margin. Nematocysts and a Symbiodinium sp. of dinoflagellate from the coral are abundantly distributed in the gut and parenchyma. Individual adults lay multiple egg batches on the coral skeleton, each egg batch has 20–26 egg capsules, and each capsule contains between 3–7 embryos. Embryonic development takes approximately 21 days, during which time characteristics of a pelagic life stage (lobes and ciliary tufts) develop but are lost before hatching. The hatchling is capable of swimming but settles to the benthos quickly, and no zooxanthellae were observed in the animal at this stage. We suggest that intracapsular metamorphosis limits the dispersal potential of hatchlings and promotes recruitment of offspring into the natal habitat. The evolutionary and ecological significance of retaining lobes and ciliary tufts in the embryo are discussed. Camouflage, high fecundity and possible dispersal dimorphisms probably explain how Amakusaplana acroporae can cause Acropora sp. mortality in aquaria where natural predators may be absent.

The Spawning Run of Blueback Herring in the St. Johns River, Florida

AbstractBlueback herring Alosa aestivalis are anadromous, iteroparous, winter spawners in the St. Johns River, Florida, but published data about this population are limited. We collected adults by electrofishing in the upper St. Johns River during the 2002–2005 spawning runs to examine the abundance, distribution, size, sex ratio, reproductive biology, and feeding habits of the population. When possible, data from the present study were compared with those for blueback herring collected with seine nets in the lower St. Johns River during the 1972 and 1973 spawning runs. Blueback herring began upstream migration by January and stayed in the river until at least April. The average fish size was significantly smaller in 2002–2005 than in 1972–1973, but sex ratios were not different from 1:1 in 5 of the 6 years studied. The more recent collections suggest that blueback herring females released multiple batches of eggs during one spawning season (spawning a batch every 3–4 d on average) and that spawning occurred as far upstream as river kilometer 400. Males and females fed actively during the entire spawning run. Overall, the stock is persistent, but its status is unknown and the smaller individual sizes evident today suggest that this population is experiencing higher mortality now than a few decades ago.

Females of the specialist butterfly Euphydryas aurinia (Lepidoptera: Nymphalinae: Melitaeini) select the greenest leaves of Lonicera implexa (Caprifoliaceae) for oviposition

In Mediterranean habitats, the specialist butterfly Euphydryas aurinia oviposits on Lonicera implexa. Previous work has shown that ovipositing females select and lay a higher number of egg clusters on certain plants. In this paper the results of a field study aimed at assessing whether females use plant size and/or plant or leaf greenness (i.e., chlorophyll concentrations) as cues for oviposition are described. Size of plants did not appear to be an important factor in determining host plant selection, probably because even small plants provide enough resources for the young larvae to reach the diapausing stage and because last instar larvae, the most likely to face resource depletion, can move great distances in search of food. Measurements of both spectral reflectance and chlorophyll concentration of plants failed to reveal differences between host and non-host plants. On the other hand, reflectance and chlorophyll concentration of leaves were found to be important in oviposition choice as egg clusters were generally located on the greenest leaves with the highest chlorophyll contents. This suggests that females use visual cues to select the leaves that will provide optimal growth opportunities for newly hatched larvae. Although there was some indication that plants receiving a greater number of egg clusters also had more leaves of high chlorophyll content, multiple egg batches on single plants could also be a consequence of females being attracted by the presence of conspecific egg clusters.

Life history of a short-lived squid (Sepioteuthis australis): resource allocation as a function of size, growth, maturation, and hatching season

Abstract Many cephalopods continue growing while laying multiple egg batches over the adult life, with repro-somatic allocation continuing beyond attainment of reproductive maturity. Many species show extreme individual variation in reproductive investment. Factors driving this variation in adult Sepioteuthis australis were evaluated by examining allocation of energy to somatic and reproductive growth as a function of body shape, growth rate, maturation, and hatching season. Hatching season influence was sex-specific; males hatched in warmer months had greater reproductive investment, faster growth, and better somatic and reproductive condition, whereas females hatched in spring and summer had less reproductive investment. Seasonal impacts on life history resulted in an “alternation of generations”, with slow-growing squid in poor condition and with high levels of reproductive investment producing a generation with completely different life-history characteristics. This suggests that abiotic and biotic conditions that change seasonally could play a large role in determining energy allocated to reproduction. However, this was not driving trade-offs between size and number of offspring. Life-history trade-offs should be detectable as negative correlations between relevant traits. However, in Sepioteuthis australis there was little evidence of trade-offs between reproduction and growth or condition of individuals, suggesting a “live for today” lifestyle.

Selection for birth date in North Sea haddock and its relation to maternal age

Summary Birth date can be important to lifetime reproductive success. However, selection for birth date has rarely been addressed in fish, despite the opportunity provided by otolith microstructure. This study examined the relationship between maternal age, spawning time and early survivorship in the North Sea haddock stock. Temporal changes in egg production were compared with the birth date distribution of progeny surviving to the demersal phase in 1994, 1996 and 1999, when the age structure of the spawning stock differed. Estimates of intra‐annual variation in stock egg production indicated that first‐time spawning 2‐year‐olds began spawning much later than older age‐classes. The form and magnitude of selection on birth date varied between years, indicating that the production of multiple batches of eggs over an extended period has some adaptive significance to progeny survival. Survivorship was consistently poor from the late spawning period when age 2 females contributed most to stock egg production. This persistent selection against late hatched offspring could reflect either low parental investment, as age 2 females produce smaller eggs, or the short length of the growing season prior to settlement. Variability in birth date selection, particularly with respect to first vs. subsequent years of spawning, implies a strong selection pressure for a long reproductive lifespan. As such, reproductive potential in this and other exploited fish species with a similar reproductive trait may have been affected adversely by the general decline in repeat spawning females in recent years.

Flexible reproductive strategies in tropical and temperate Sepioteuthis squids

A major difficulty confronting the determination of cephalopod reproductive life history is assessing over what portion of the life span an individual is reproductively mature and actively depositing eggs. This paper assesses the potential of the tropical Sepioteuthis lessoniana and two genetic types of the temperate Sepioteuthis australis, to spawn multiple batches of eggs at discrete times throughout the adult life span. This is achieved by histological examination of the ovarian gametogenic cycle and detailed morphological assessments of the reproductive system, in conjunction with other biological information. The genetic type of S. australis found at the northern limits of its Australian distribution showed evidence of a high correlation between body size and quantity of mature eggs, suggesting that eggs may be accumulating to be laid in a single batch. Although maturation was also a size-related process in S. lessoniana and Tasmanian S. australis, oviduct size was not correlated with body weight in mature females, which is indicative of multiple spawning. Further supporting evidence includes relatively low gonadosomatic indices, the heavier weight of the ovary relative to the oviduct, and the feeding activity of mature animals. Mature S. lessoniana and S. australis individuals were present at each location over very wide age and size ranges. In Tasmanian waters, there were distinct seasonal differences in the reproductive biology of S. australis. Summer-caught individuals had much higher gonadosomatic indices and may have been laying larger batches of eggs compared with winter-caught individuals. Summer-caught females also showed a negative correlation between egg size and egg number within the oviduct, suggesting that some individuals were producing fewer, larger eggs and others many smaller eggs. Evidence suggests that considerable flexibility is inherent in the reproductive strategy of both S. lessoniana and S. australis.

Maternal Influences on Variation in Egg Sizes in Temperate Marine Fishes

SYNOPSIS. We examine the variation in egg sizes of marine teleosts and evaluate the maternal contribution to this variability. At the species level, egg sizes in 309 North Atlantic fishes range from 0.3 to 18.0 mm diameter (median = 1.1), size at hatching varies directly with egg size, and large adult size is associated with large eggs but the relationship is weak. Within populations, egg sizes are distributed normally with a median coefficient of variation of 4% (n = 56 species). Egg size varied among females in all cases for which female-level data were found. Estimates of the variance components of egg size due to females were found for three species and, as a percentage of total variance, are 71 % for capelin, Mallotus villosus , 46% for winter flounder, Pleuronectes americanus , and 35% for Atlantic cod, Gadus morhua . For cod, which spawn multiple egg batches per year, an additional batches-within-females component was estimated to be 26%. Size at hatching also differs among sibgroups and is generally directly related to egg size at the individual level. We modelled fish growth by allowing individuals to grow at exponential rates from a normal distribution of initial sizes. Comparing size variation in model fish to empirical evidence suggests that variation in initial sizes, propagated by growth, could account for a large fraction of the size variation observed months after hatching in natural populations. We view size variation in young marine fishes to be largely of maternal origin and environmentally modulated, which if true has special consequences for fisheries and aquaculture.

Multiple spawning in the tropical squid Photololigo sp.: what is the cost in somatic growth?

This study assesses the potential of the tropical loliginid squid Photololigo sp. to lay multiple batches of eggs and examines changes in somatic growth during reproduction. Histological analysis of the ovary and the relative size of the oviduct to mantle weight and ovary weight were used to determine the potential for multiple spawning. Ovaries of mature females always had immature and mature oocytes present, suggesting that not all the oocytes were maturing simultaneously and that multiple batches of eggs were being produced. Furthermore, poor correlations of oviduct weight with body size and ovary weight indicated that mature oocytes were not accumulating in the oviduct for a single spawning event. Both these observations supported the hypothesis that Photololigo sp. has the potential to lay multiple batches of eggs throughout its life. Specific growth rates, length-weight relationships, relative growth of somatic and reproductive tissue and microscopic assessment of muscle tissue were compared between immature and mature females. Growth rates of immature females were almost twice as fast as those of mature females. Mature females also had no large muscle fibres present, suggesting that energy for reproduction was mobilised from the muscle tissue.

Seasonal incidence of egg‐bearing in the New Zealand paddle crabOvalipes catharus(Crustacea: Brachyura), and its production of multiple egg batches

Abstract The annual reproductive cycle of Ovalipes catharus (White) was investigated by determining the proportion of mature females carrying eggs, in samples of crabs taken at dusk every 4 or 5 weeks for 22 months from Plimmerton Beach, near Wellington, New Zealand. Three peaks of egg‐bearing were found over each breeding season: the first during August, the second through late November and early December, and the last during early January into early April. The average carapace width (CW) of crabs carrying eggs was 84.6 ± 9.65 mm and this average did not alter significantly during the year. Smaller female crabs (41–60 mm CW) were found carrying eggs predominantly during January and February. Captive O. catharus were able to produce a maximum of five batches of eggs during one intermoult period, from a single insemination. The average number of egg batches produced increased with crab size. Crabs 90 mm CW produced an average of three ...

Spawning Mode and Reproductive Output of the Tropical Cephalopod Idiosepius pygmaeus

Reproductive biology of the tropical sepioid cephalopod Idiosepius pygmaeus was investigated in wild specimens and in individuals maintained in aquaria through the adult life span. This species produced multiple egg batches over 80% of the observable adult weight range, indicating a coordination of reproductive and somatic growth. Reproductive output was consistent within, but variable between, individuals. Oocyte synthesis and maturation occur continuously after sexual maturation has been reached. Senescence and death are not related to an exhaustion of reproductive potential. On average, captive female I. pygmaeus with access to unlimited food produced 640 eggs in 11 batches over 18 d. When reproductive output was expressed as a ratio of dry female body weight, on average, specimens had incorporated five times their body weight into eggs and egg coatings. Under food stress, captive specimens laid fewer eggs but maintained egg size and periodicity of egg laying. Food stress had no effect on either laying duration or weight at death. This study provides further evidence that terminal spawning modes are not ubiquitous amongst cephalopods.

Viviparity and the reproductive ecology of clinid fishes (Clinidae) from temperate Australian waters

Viviparity is reported in twelve species of the family Clinidae in Tasmanian waters, and superfoetation (the simultaneous development of multiple batches of eggs and/or embryos) in nine of the twelve (all in the subfamily Clinini). The reproductive anatomy and life history features are documented in two superfoetate, shallow-water species,Heteroclinus perspicillatus andHeteroclinus sp. nov. (Scott's Weedfish). Gestation of embryos is intrafollicular and their mode of nutrition shifts from lecithotrophy during early development to trophodermal matrotrophy and, eventually, intestinal nutrient transfer. The sizes of the newly born larvae differ between species, but in all cases maternal investment in individual offspring (as measured by the proportionate increase in embryo dry weight)—20125%, 5744% and 3140% forH. perspicillatus, Scott's Weedfish andH. heptaeolus, respectively — is among the highest recorded for teleosts. Relative fecundity, however, is comparable to those of temperate, demersal spawning blennioids, and this suggests that high levels of maternal investment and relatively advanced stages of larval development at parturition for the sub-family as a whole do not involve a cost in individual fecundity. Parturition, which occurs over several months in spring and summer, is asynchronous. After parturition, the larva spend from 3 to 7 weeks in the plankton, primarily in in-shore waters. Post-settlement growth is rapid and most of the reproductive populations consist of fishes in the 1 + year-class.