Ecophysiological studies on developing eggs and ovigerous females of intertidal crabs (original) (raw)
Related papers
Marine and Freshwater Research, 2001
The size and composition of eggs from 22 giant crabs ( Pseudocarcinus gigas ) were monitored over 165 days to determine trends through embryogenesis. Egg composition was most stable during the early stages of embryogenesis so additional sampling ( n =143) was conducted during this period to assess the effect of female size, sampling location (east and west Tasmania) and successive broods between moults, on egg composition. During embryogenesis, eggs increased in diameter and moisture content while organic dry mass declined. Total carotenoid and lipid content per egg did not change significantly, whereas protein declined (as ash-free dry mass per egg). This indicates that protein was used preferentially to lipid, which may be an adaptation to the deeper water habitat of P. gigas . Females with heavy and intermediate carapace wear were considered more likely to have produced previous clutches and they produced eggs with significantly less carotenoid. The eggs of larger females contained significantly more water, less protein and less carotenoid, whereas there was no effect on total lipid ( P <0.05). Although the effects of female size on egg composition were significant, the magnitude of the effect was small (highest for carotenoid, r 2 =0.17). Consequently, it is unlikely that larval viability is affected, or that larger females contribute more to recruitment than predicted by fecundity.
2013
Portunus pelagicus Linnaeus, 1758 is an important candidate species for culture in India and trials are for developing its hatchery technology. The present work investigates the changes occurring in diameter, volume, wet weight and morphology of P. pelagicus eggs during incubation which would improve the knowledge base on embryology of species. Mated females from wild were maintained under similar physico-chemical conditions. Once spawned, the egg samples were collected from each animal daily and their diameter, volume, and wet weight were assessed. Based on the changes occurring in egg morphology at 24 hour intervals, the embryo development was classified into eight 'periods'. The egg size and wet weight varied significantly (P<0.01) among crabs and egg size was unrelated with the carapace width of female. The average diameter, volume and wet weight of the egg were 0.324 mm, 0.016 mm 3 and 0.048 mg, respectively. Diameter, volume and wet weight of the eggs increased to 13.58, 46.52 and 49.05%, respectively and the major share of increment occurred in last two days.
Integrative and Comparative Biology, 2011
Synopsis Most semiterrestrial, intertidal and shallow subtidal brachyuran crabs that live in tropical and warm temperate estuaries, bays and protected coasts worldwide release their planktonic larvae near the times of nocturnal high tides on the larger amplitude tides in the biweekly or monthly cycles of tidal amplitude. Crab larvae usually emigrate quickly to the sea where they develop to return as postlarvae to settle in habitats suitable for their survival. Predators of larvae are more abundant where larvae are released than where they develop, suggesting that this migration from estuaries to the sea reduces predation on larvae. Crabs with larvae that are relatively well-protected by spines and cryptic colors do not emigrate and often lack strong reproductive cycles, lending support to this explanation. Adults control the timing of the release of larvae with respect to the biweekly and monthly cycles of tidal amplitude by controlling when they court and mate and females control when development begins by controlling when they ovulate and allow their eggs to be fertilized by stored sperm. By changing the time they breed, fiddler crabs (Uca terpsichores) compensate for the effects of spatial and temporal variation in incubation temperature on development rates so that embryos are ready to hatch at the appropriate time. Control of the diel and tidal timing of hatching and of release of larvae varies with where adults live. Females of the more terrestrial species often move from protected incubation sites, sometimes far from water, and they largely control the precise time, both, of hatching and of release of larvae. Females of intertidal species also may influence when embryos begin to hatch. Upon hatching, a chemical cue is released that stimulates the female to pump her abdomen, causing rapid hatching and release of all larvae in her clutch. Embryos, rather than females, largely control hatching in subtidal species, perhaps because females incubate their eggs where they release their larvae. Topics for further study include the mechanism whereby adults regulate the timing of breeding, the mechanisms by which females control development rates of embryos, the nature of communication between females and embryos that leads to precise and synchronous hatching by the number (often thousands) of embryos in a clutch, and the causes of selection for such precision. The timing of hatching and of release of larvae by cold-temperate, Arctic, and Antarctic species and by fully terrestrial and freshwater tropical species has received little attention.
Marine Ecology Progress Series, 2003
In an experimental laboratory investigation on an estuarine crab, Chasmagnathus granulata Dana, we investigated how salinities experienced during embryonic and larval development (embryonic and larval salinity exposures, respectively) and intraspecific variability of initial biomass at egg laying and hatching affected larval performance. The latter was measured in terms of survival rate, duration of development through successive stages, frequency of occurrence of an additional (fifth) zoeal stage, and size of the first juvenile instar. Ovigerous female crabs were maintained at 3 salinities (15, 20, 32 ‰). For each egg mass, biomass of freshly laid eggs and of freshly hatched larvae, respectively, was measured as dry mass, carbon, and nitrogen contents. After hatching, the larvae were reared at salinities of 5, 10, 15, and 32 ‰. When larvae hatched from eggs that had been incubated at reduced salinities (15 or 20 ‰), their survival through the zoea I stage at low salinities (5 and 10 ‰) was high and stage duration was short. By contrast, poor survival and delayed development were observed in larvae reared at low salinities when they hatched from eggs that had been incubated in full-strength seawater (32 ‰). Larval rearing in seawater allowed generally for highest survival and shortest development. While the embryonic salinity exposure had a strong influence on the performance of the first zoeal stage, later stages showed no significant response to the previous conditions of egg incubation. At advanced stages, low larval salinity exposure (15 ‰) led to consistently lower survival, longer duration of development, and higher proportion of larvae passing through an additional zoeal instar. However, larger juveniles metamorphosed from larvae that hatched from eggs incubated at low (15 ‰) salinity. The initial biomass of eggs and larvae, which varied significantly among broods produced by different females, was identified as another factor affecting larval performance. At constant 32 ‰, larvae with high initial biomass showed higher survival and faster development. Significantly more larvae developed through an additional instar when they hatched with a low initial biomass. In conclusion, our results show that the performance in a given phase of a complex life-history depends not only on the present environmental conditions but also on those prevailing in the preceding phase. Moreover, intraspecific variability in maternal energy investment into offspring production may play a significant role for the chances of larval survival and development in the plankton.
Timing of larval release by intertidal crabs on an exposed shore
1986
Semilunar, tidal and diel timing of larval release by four species of intertidal crabs that occur together on exposed cobble beaches on the Pacific coast of Panama was studied to provide comparisons to temporal patterns of hatching known for estuarine species. Ovigerous females, collected periodically and held until their eggs hatched, were observed daily to determine day-today variation in the number releasing larvae. Tidal and solar-day timing of hatching were studied by collecting, at 3D-min intervals, zoeae released by females held in a box in the intertidal zone. Xanthodius sternberghii and Cataleptodius taboganus released larvae at night within 1.5 h of high tide and usually during the hour following last light 1-4 days before the quarter moons. Eurypanopeus planus released larvae throughout the lunar cycle about I h before both daytime and nighttime high tides. Petrolisthes armatus also released larvae throughout the lunar month but hatching usually occurred only near the times of high tides that peaked at twilight or at night. The timing of hatching by X. sternberghii and C. taboganus is closely similar to that exhibited by several intertidal estuarine crabs. In estuaries, such timing may aid escape of larvae from lethal high temperatures and low salinities. Since these environmental factors vary little with the tidal and diellight cycles on exposed coasts they are unlikely to be important mortality factors influencing the timing of hatching in such habitats. Instead the timing oflarval release may aid escape of newly hatched larvae from planktivorous fish that locate prey visually. Contrasts in the timing of hatching among the four species are associated with differences in zoeal size and color, features that may affect their visibility to predators.
Ecological Research, 1989
Reproductive traits of three ocypodid crabs, Scopimera globosa, llyoplax pusillus and Macrophthalrnus japonicus, were compared. S. globosa and L pusillus, inhabiting the upper-middle intertidal zone, produced 1-2 large broods per year, whereas M. japonicus, inhabiting the lower intertidal zone, produced 4 5 small broods per year. In S. globosa and L pusillus, ovigerous females remained in their plugged burrows without feeding until their eggs hatched. On the other hand, female M. japonicus fed actively on surface mud while incubating. We concluded that few large broods may be advantageous in crab species that incubate in burrows, whereas continuous small broods may be advantageous in species thai feed actively while incubating.
Biological Bulletin, 1987
The relationship between egg number, size, and year class was determined for sand crabs (Emerita ana.loga) collected at three California sites, including two differ ent dates for two ofthose sites. Size frequency distributions ofsand crab population samples collected in 1982 from San Clemente, Goleta (2 dates), and Pismo Beach (2 dates) were separated into three modal size/year classes before plotting the size and egg number data and calculating regressions for egg number as a function ofsize. The slope ofthe regressions for within year class data generally decreased with increase in age. Both seasonal and locality differences were found in comparisons of data for individual year classes. The technique can be used to compare egg production be tween female crabs ofsimilar ages between sites and/or dates.
The brown crab is an important fishery resource in northern Europe. Understanding factors that affect fecundity in this species is complicated by the fact that ovigerous females enter traps infrequently. This study aimed to understand factors that affect brown crab fecundity and egg quality for crabs sampled from the waters around the Isle of Man. The size-fecundity relationship for the Isle of Man matched closely with those published for other geographical areas where a fishery exists for this species. Ovigerous crabs varied in size from 134 to 215 mm carapace width and each individual carried an estimated 0.4–3.0 million eggs. Fecundity was not affected by factors such as sampling season, location, loss of chelae, or black spot disease. Egg volume was independent of the number of eggs per batch or female body size. Egg volume was reduced significantly in crabs that had lost chelae. Egg dry weight, C and N composition did not vary with body size or any other explanatory factors such as chelal loss or the occurrence of black spot disease. Although the importance of the effect of claw loss on egg volume remains unclear, it may be an important consideration in fisheries in which the landing of claws is permitted.
2004
The female reproductive biology of a Chasmagnathus granulatus population inhabiting the area near the mouth of Mar Chiquita coastal lagoon, Argentina, was studied. An increase in air temperature during the spring is related to the start of the breeding period, when well defined egg-laying and hatching pulses were observed. Hatching is synchronic during the whole summer but the egg production was not, probably due to the gradual incorporation of young females to the reproductive population. Neither egg-laying nor larval release showed a clear relation to moon phase or tidal cycles, suggesting that reproduction is not rigidly programmed in this unpredictable habitat. Females moult at the beginning of autumn, after releasing the last larvae. However, a new cohort of ovocytes, which was in primary vitellogenesis before moulting, completed the secondary ovogenesis after moulting. Consequently, ovaries remained fully developed throughout the winter.