Developmental shift in the selective tidal-stream transport behavior of larvae of the fiddler crab Uca minax (LeConte)

Following hatching, larvae of the fiddler crab Uca minax (La Conte) are exported from the adult habitat in estuaries to coastal and shelf waters where they undergo development prior to re-entering estuaries as postlarvae (megalopae). Studies of the spatial distribution of both newly hatched zoeae (Stage I) and megalopae indicate they undergo rhythmic vertical migrations associated with the tides for dispersal and unidirectional transport (selective tidal-stream transport) both within estuaries and between estuaries and the nearshore coastal ocean. We tested the hypothesis that U. minax zoeae possess a circatidal rhythm in vertical migration that facilitates offshore transport in ebb tidal flows, while postlarvae (megalopae) return to estuaries using a similar flood-phased endogenous rhythm. We also determined if the expression of the rhythm was influenced by the salinity conditions zoeae and megalopae experience as they transition between low-salinity regions of estuaries and high-salinity coastal waters. Stage I zoeae were collected by holding ovigerous female crabs in the lab until hatching. Megalopae were collected from the plankton and identified to species using molecular techniques (PCR-RFLP). Under constant laboratory conditions, both zoeae and megalopae exhibited endogenous circatidal rhythms in swimming that matched the principal harmonic constituent of the local tides (12.39 ± 0.07 h; X¯ ± SE). Upward swimming in Stage I zoeae occurred 2.5-4 h after high tide near the time of expected maximum ebb currents in the field. Rhythmic swimming of megalopae occurred slightly earlier in the tide (2.5 ± 0.09 h after high tide; X¯ ± SE) but was not entirely synchronized with flood currents, as expected. Salinity conditions had no apparent effect on the expression or pattern of the rhythms. Results indicate that this circatidal rhythm forms the behavioral basis of selective tidal-stream transport (STST) in early stage U. minax zoeae, but does not undergo a sufficient phase shift to account for vertical distribution patterns exhibited by megalopae in the field.     

The effect of salinity on respiratory metabolism in selected ontogenetic stages of the freshwater shrimp Macrobrachium olfersii (Decapoda,palaemonidae)

• 1.1. The effect of acute salinity exposure (0, 7, 14, 21, 28 and 35%.S) on the respiratory metabolism of selected ontogenetic stages (zoeae, postlarvae and adults) of the freshwater shrimp Macrobrachium olfersiiwas examined.
• 2.2. Metabolic rates are salinity independent from 14 to 28%. S in zoeae 1–4, but tend to increase with increasing salinity in zoeae 5 and 8. Postlarvae exhibit maximal rates in midrange salinities while in adult shrimps, oxygen consumption rates decrease with salinity increase.
• 3.3. Salinity has little effect on the metabolism-weight relationship, regression analysis indicating that b varies from 0.69 in 0%. S to 0.62 in 35%. S.
• 4.4. Data are discussed as to whether larval responses reflect adaptation to the adult biotope and whether development of the larval neurosecretory system might affect metabolic response to salinity exposure.

     

Morphological and behavioral antipredatory adaptations of decapod zoeae

Summary Zoeae of some species of estuarine decapods are retained in the estuary throughout development while others are exported into nearshore coastal waters. The horizontal migrations of decapod zoeae to coastal waters may have evolved to reduce the probability of encountering planktivorous fishes which are most abundant in the estuary. If so, then the morphological vulnerability of zoeae to fish predation should be inversely related to the number of predators occurring where they develop. Six species of estuarine decapod zoeae were offered to Menidia menidia and Fundulus heteroclitus. The behavioral interactions were observed to determine the prey's vulnerability to predation, and the mode of operation and relative effectiveness of their defenses. Feeding trials and behavioral observations both demonstrated that M. menidia 6–16 mm long preferred Uca minax and Callinectes sapidus zoeae, which are exported from the estuary, to Rhithropanopeus harrisii, Sesarma reticulatum and Palaemonetes pugio, which are retained within estuaries. Pinnotheres ostreum zoeae develop in the lower estuary and fish demonstrated an intermediate preference for the zoeae. Menidia menidia 20–40 mm long showed similar preferences for R. harrisii S. reticulatum, P. ostreum and U. minax as did small silversides. Large-mouthed demersal fish, Fundulus heteroclitus 6–10 mm long, also preferred U. minax to R. harrisii, but more readily preyed on zoeae than did M. menidia. The exported species of zoeae have shorter spines and smaller bodies than do retained zoeae, except P. ostreum which is small, spineless and passively sinks when attacked by fish. Other retained species of zoeae also have postcontact behavioral defenses which enhance the effectiveness of their morphological defenses. Zoeae do not evade attacks by fishes, but fishes quickly learned to avoid zoeae, which increases the effectiveness of the zoeae's antipredatory adaptations.     

Planktonic larval stages of Brachyura in the Gulf of Tigullio (Ligurian Sea,Italy)

Summary

Horizontal planktonic catches made in the Gulf of Tigullio (Genoa, Ligurian Sea) have been analyzed with the aim of identifying the zoeae of Brachyura, whose knowledge is poor in all the northern Mediterranean Sea. Forty-four taxa (42 species plus Liocarcinus spp. and Brachynotus spp.) have been identified, 12 of which were present with all the larval stages. The seasonal distribution of the taxa has been analyzed, and it was possible to recognize species present throughout the year as well as spring/summer, summer/autumn, and winter/summer species. Problems regarding zoeae of dubious identification are discussed.     

A key for the identification of the known larval stages of the Mediterranean Brachyura

Summary

Based on the accounts by various authors, an identification key has been constructed for the planktonic zoeae of the 70 species of Mediterranean Brachyura whose larvae are known. The key is based on primary (spines of the carapace, exopodite of the antenna, spines of telson forks) as well as secondary (setation of mouthparts, processes and spines on abdominal somites) morphological characteristics. It allows the identification of the zoeae of 64 species plus those of Liocarcinus genus (six species).     

Temperature and salinity tolerances of Stage 1 zoeae predict possible range expansion of an introduced portunid crab, Charybdis japonica, in New Zealand

The successful invasion of a non-native species depends on several factors, including initial colonization and establishment of a self-sustaining population. Populations of the non-native paddle crab Charybdis japonica were first recognized in the Waitemata Harbour, Auckland, New Zealand in 2000, most likely arriving in ballast waters of an Asian merchant vessel. A survey completed in 2003 found C. japonica throughout the Waitemata Harbour, and further sampling in 2009 has revealed several well established populations in estuaries up to 70 km from the putative invasion point. As the potential for further establishment of C. japonica beyond this area may depend on the temperature and salinity tolerances of their free swimming larvae, we quantified the survival of newly-hatched Stage 1 C. japonica zoeae subjected to temperatures ranging from 11 to 43°C or salinities from 5 to 45?? in the laboratory. Upon hatching, replicate C. japonica zoeae were directly transferred from 21°C and 34.6?? seawater to either an experimental temperature or salinity level. Behaviour and death rates of the larvae were monitored over a 24 h period in the absence of food. Comparisons of zoeal survival rates to historical sea surface temperatures and salinities show that C. japonica Stage 1 zoeae tolerate a broad range of temperatures and salinities and could survive natural conditions throughout New Zealand. This gives C. japonica the potential to invade many other New Zealand estuaries and harbours.     

Physiological responses of the early zoeal stages of Palaemon pandaliformis Stimpson and Palaemon northropi (Rankin) to salinity variation

The effect of salinity variation (0, 7, 14, 21, 28 and 35S) on survival, moulting and respiratory metabolism of the early zoeal stages of the shrimps Palaemon pandaliformis and P. northropi from the northern coast of the State of São Paulo, Brazil is investigated. Freshly hatched larvae were maintained at 20 °C, in each salinity for a maximum of seven days. Oxygen consumption measurements were made at 20 °C for each salinity using Cartesian diver microrespirometers. In 0S, all P. northropi zoeae died after 24 h while 24% of the P. pandaliformis zoeae survived until 4 days. Zoeae of both species survived poorly in 7S, the best survival for the two species (90%) being registered in 28%.S. Palaemon northropi zoeae did not survive 35S while 45% survival was recorded for P. pandaliformis zoeae in this medium after seven days. Moulting did not occur in zoeae of either species in 0%.S, nor in P. northropi in 7S. The metabolism-salinity curve for P. pandaliformis zoea I is very stable over the range 0–21S while that for P. northropi exhibits complete salinity independence from 21–35 S. Thus, while the early zoeal stages, at least, are conspecific, both developing in the same environment as part of the coastal zooplankton community, they clearly maintain distinct physiological characteristics. The data presented possibly reflect genetic adaptations to the adult biotope already manifested in the first zoeae.     

Morphology of the first zoeal stages of eleven Sesarmidae (Crustacea,Brachyura, Thoracotremata) from the Indo-West Pacific,with a summary of familial larval characters

Summary

The first zoeal stages of eleven species of Sesarmidae from the Indo-West Pacific were obtained from ovigerous females. Those of Labuanium scandens, L. rotundatum, L. trapezoideum, L. politum, Metasesarma aubryi, Pseudosesarma crassimanum, Stelgistra stormi, and Sesarmops impressum, are described for the first time, while the first zoeal stages of Clistocoeloma merguiense, Metasesarma obesum and Sesarmops intermedium are re-described. Larval characters of all these species are compared with previously described ones for the family and morphological features are re-evaluated. Minute spines on the telson of the zoeae are described as a new larval character in Sesarmidae and their presence or absence in other grapsoid groups is discussed. The results demonstrate that a recurrent combination of reliable larval characters distinguishes zoeae and megalopae of the examined sesarmids from the rest of the Grapsoidea. This appears to be consistent with recent studies that redefine the Sesarmidae.     

Three species of Lagenidiales isolated from the eggs and zoeae of the marine crabPortunus pelagicus

Three species of Lagenidiales were isolated from the eggs and zoeae of the marine crabPortunus pelagicus. One of them,Lagenidium callinectes, is reported for the first time in Japan, with fungal infection in the eggs.Haliphthoros milfordensis was discovered from a zoea of the crab.Atkinsiella okinawaensis was also isolated from a zoea of the crab and described as a new species. Growth temperature range and optimum temperature of the fungi were examined. All of the isolates grew at various concentrations of NaCl or KCl, and optimum growth was observed on PYGS agar containing seawater. Pathogenicity to zoeae of the swimming crabPortunus trituberculatus was demonstrated by using a zoospore suspension of each fungus at 25°C.     

Seasonal variation in the occurrence of planktonic larvae of sympatric hermit crabs

Patterns of seasonal change in the abundances of the planktonic larvae of four sympatric hermit crabs were examined at five fixed stations over 18 months in Christmas Bay, Texas. Clibanarius vittatus (Bosc) was present in the plankton from April through October, Pagurus longicarpus Say from September through May and P. pollicaris Say from December through February. Pagurus annulipes (Stimpson) zoeae were the most frequently encountered zoeae and were found throughout the year, but were most abundant in late spring and summer. Zoea I of P. annulipes and P. pollicaris were found to be reliably distinguishable on the basis of their carapace lengths. Clibanarius zoea I were very abundant (3149) and 42 megalopa but no zoea II–V were found. Inadequate sampling and the short durations of these missing stages do not seem sufficient to explain their absence.     

The Morphology of the Mandibles in Zoea I Larvae of the Burrowing Shrimp Genera <Emphasis Type="Italic">Upogebia</Emphasis> (Gebiidea) and <Emphasis Type="Italic">Nihonotrypaea</Emphasis> (Axiidea)

The mandibles in the first zoeal stage of five species of the burrowing shrimp genera Upogebia (infraorder Gebiidea) and Nihonotrypaea (infraorder Axiidea) have been examined by scanning electron microscopy. The general shape of the mandibles in Upogebia zoeae is similar to that in Anomura larvae; in Nihonotrypaea, it is intermediate between the mandibles of anomuran and caridean shrimp larvae. The asymmetry of the mandibles, which is more pronounced in Nihonotrypaea, is confirmed. Species-specific features of the structure of the incisor process are found in three Upogebia species, while two Nihonotrypaea species almost do not differ in the mandible structure in their zoea I larvae. The morphological features of the mandibles indicate differences in the diet of Upogebia and Nihonotrypaea larvae. Under natural conditions, zoea I of the studied Nihonotrypaea species may feed on diatoms, which should be taken into account when rearing these decapod larvae in the laboratory.     

Effects of inorganic mercury on the respiration and the swimming activity of shrimp larvae,Pandalus borealis

In order to test the sensitivity of respiration (physiological and potential) to mercury (Hg) contamination, larval shrimp Pandalus borealis were exposed to inorganic Hg (0–160 ppb) for 27 h in the laboratory. Oxygen consumption rates (RO₂), potential respiration (determined by respiratory electron transfer system activity, ETSA), protein content, and swimming activity for zoeae III and zoeae V stages were measured. For both zoeae stages, ETSA and protein content remained constant after 27 h exposure to 160 ppb Hg whereas RO₂ and swimming activity decreased. This study revealed the impact of different Hg levels and different exposure times on RO₂ of shrimp larvae. After 10 h exposure to 160 ppb Hg, the RO₂ decreased by 43 and 49% in zoeae III and zoeae V stages, respectively. Exposure time of 27 h to 80 ppb Hg and higher, induced paralysis in nearly 100% larvae. Surprisingly, the paralysed larvae displayed almost 50% of the control's RO₂. The results showed that Hg disturbs a part of the respiration process without modifying the maximum activity of the enzymes involved in the ETSA assay. Therefore, the ETSA assay can not be used as a sublethal bioanalytic probe to detect Hg in short-term exposures. The decline of the RO₂/ETSA ratios reported here, indicates an inability of contaminated larvae to adapt their metabolism to physiological stress caused by Hg.     

Complete larval development of the hermit crabs Clibanarius aequabilis and Clibanarius erythropus (Decapoda: Anomura: Diogenidae), under laboratory conditions, with a revision of the larval features of genus Clibanarius

The complete larval development (four zoeae and one megalopa) of Clibanarius aequabilis and C. erythropus, reared under laboratory conditions, is described and illustrated. The larval stages of the two northeastern Atlantic Clibanarius species cannot be easily differentiated. Their morphological characters are compared with those of other known Clibanarius larvae. The genus Clibanarius is very homogeneous with respect to larval characters. All Clibanarius zoeae display a broad and blunt rostrum, smooth abdominal segments and an antennal scale without a terminal spine. Beyond the second zoeal stage, the fourth telson process is present as a fused spine, and the uropods are biramous. In the fourth larval stage all species display a mandibular palp. The Clibanarius megalopa presents weakly developed or no ocular scales, symmetrical chelipeds, apically curved corneous dactylus in the second and third pereiopods, and 5–11 setae on the posterior margin of the telson. Apart from the number of zoeal stages, Clibanarius species may be separated, beyond the second zoeal stage, by the telson formula and the morphology of the fourth telson process.     

Morphology of Coenophthalmus tridentatus first zoea (Crustacea: Portunidae: Polybiinae) hatched in the laboratory

The swimming crab Coenophthalmus tridentatus A. Milne Edwards,1879 (Decapoda, Portunidae) is an endemic species of the SouthwesternAtlantic, from southern Brazil to northern Patagonia (Argentina).Larvae of C. tridentatus from one female collected on beds ofoysters and mussels at 50 m depth in the Argentine continentalshelf (38°21'S, 57°38'W) were hatched in the laboratory.Zoea I morphology is described for the first time and comparedwith known zoeae of other portunid species.     

Distribution of euphausiid and decapod larvae in the spring plankton of the southern Barents Sea

New data have been obtained on the spatial distribution of the early developmental stages of Malacostraca in the mesozooplankton of the southern Barents Sea. In spring 2007, the euphausiid stages with the highest abundance (over 80%) were eggs and nauplii. Decapod larvae were represented by zoeae of Paralithodes camtschaticus, Pagurus pubescens, and Hyas araneus; their abundance was at most 1.5% of total zooplankton abundance. The larvaton groups dominant by abundance were furciliae of Euphasiacea (14.5 ± 6.2 mg/m³) and zoeae of P. camtschaticus (32.7 ± 15.9 mg/m³). The size structure of larval hemipopulations was similar over the studied water area. Comparison with data on the larval body length obtained in other areas of the sea leads to a conclusion on the independence of the decapod groups of Eastern and Western Murman.     

Seasonal and tidal abundance patterns of decapod crustacean larvae in a shallow inlet (SW Spain)

Planktonic larvae of decapod crustaceans were collected monthlyfrom July 1991 to June 1992 by pumping during nocturnal floodand ebb tides to establish seasonal larval abundance patternsin an inlet of the Bay of Cdiz. Additional 24 h series of sampleswere collected seasonally (July 1991, October 1991, January1992 and May/June 1992) during spring and neap tides to analyselarval abundance in relation to the main environmental cycles(diel, tidal and lunar phases) and vertical position in thewater column. First zoeae were the most abundant stage for mostspecies, representing 97.6% of all individuals collected. ZoeaI abundance was higher in spring and swmner and, on most samplingoccasions, there was a net output from the inlet to the bay.Five species (Liocarcinus arcuatus and Liocarcinus vernalis,Uca tangeri, Diogenes pugilator and Panopeus africanus) represented60% of total individuals caught. The seasonal occurrence offirst zoeae of the most abundant species indicated two differentreproductive patterns: species with a short reproductive periodand species spawning year round. Zoea I of several species (Panopeusafricanus, Uca tangeri, Pachygrap sus marmoratus, Processa spp.)were significantly more abundant during ebb tides and theirlater larval stages were scarcely collected, suggesting thatthese larvae are released in the inlet and exported to the bay.Conversely, a net input of first zoeae was observed for otherspecies (D.pugilator and Pinnotheres pinnotheres), but theirlater larval stages were also scarcely collected. Such importationcould be a larval rhythm artifact due to release of larvae inthe bay that drifted into the inlet by tidal currents. The crabIlia nucleus, whose later larval stages were collected frequently,was the only species that seemed to complete its life cyclewithin the bay. These results suggest that the studied inletwas primarily used by decapods as an adult habitat and spawningground, while larval development occurred in open sea. Sincevertical migration was not observed for exported larvae, thetidal synchronization of female release seemed to be the mostprobable mechanism of larval exportation. There were no significantdifferences between larval release during spring and neap tides.     

The effect of salinity on respiratory metabolism,survival and moulting in the first zoea of Macrobrachium amazonicum (Heller) (Crustacea,Palaemonidae)

Survival, duration of intermoult cycle and respiratory metabolism were evaluated as a function of salinity (0–35‰; 25° C) in early zoeae of the cinnamon shrimp, Macrobrachium amazonicum. Zoeae are extremely resistant to salinity, mortality occurring only in fresh and sea-water after several days. Moulting occurs in all salinities, longer cycles being recorded in 0 and 35‰ S. The metabolism-salinity curve is broadly U-shaped between 0 and 28‰ S but declines sharply in sea-water. Such physiological responses characterise the early zoeae as strongly euryhaline and typically estuarine. Data are discussed in relation to the degree of adaptation of the organism to the freshwater biotope and the position of the species within the generic pattern of adaptive radiation.     

Effect of environmental embryonic temperature on larval development of Macrobrachium rosenbergii (De Man)

Berried females of Macrobrachium rosenbergii (De Man) from Anuenue stock were allowed to incubate their eggs at three different temperatures (25,29, and 31°C). The newborn larvae were reared in the laboratory from hatch through completion of the metamorphosis to postlarva in 30 combinations of temperature (22–34° C) and salinity (0–34 ppt). Survival and stage attainment rates were observed. Multiple linear regression analysis and response surface methodology were used to estimate the response of larvae to these different temperature and salinity combinations. Dissimilarities in the response of zoeae from the three egg incubation temperatures were found. Larvae from eggs incubated at 25° C during embryonic development showed tolerance to a broader range of temperature and salinity conditions than those incubated at 29 or 31 °C. The response also changed with the ontogeny of the larvae. The zoeae are considered to have undergone acclimation during embryonic development, thus eliciting a different response.