Ghost Shrimp Research Articles

Reproductive strategy of the ghost shrimp Callichirus major (Crustacea: Axiidea: Callianassidae) from the southwestern Atlantic: sexual maturity of females, fecundity, egg features, and reproductive output

Reproduction and reproductive investment of females is an intriguing feature in axiidean shrimps. They have a cryptic behavior and great ecological importance in sediment turnover, and recycling of organic material and nutrient. Herein, we describe different aspects of the reproductive biology (size at sexual maturity of females, fecundity, egg characteristics, and reproductive output [RO]) of the ghost shrimp Callichirus major from the southeastern coast of Brazil. Females reached sexual maturity at sizes ≥11.85 mm dorsal oval length. Fecundity increased significantly with female size and varied between 1455 and 9931 eggs (average 4564 eggs). Individual egg volume almost doubled during embryogenesis, and average egg water content increased during the incubation period from 75.0 to 93.3%. The egg mass comprised on average 13.2% of the dry body weight of females. This relatively high RO value is probably compensatory to the relatively low number of ovigerous females in axiidean populations. The few published data on RO values suggest that female investment in reproduction of axiidean shrimps is somewhat higher than in other decapods. The high investment in egg production reflects most likely an effort to maximize the viability of the progeny. Studies with additional congeneric species will clarify whether there is a tendency of axiidean shrimps to have RO values at the upper end of the range reported for decapods.

Disturbance facilitates the coexistence of antagonistic ecosystem engineers in California estuaries.

Ecological theory predicts that interactions between antagonistic ecosystem engineers can lead to local competitive exclusion, but disturbance can facilitate broader coexistence. However, few empirical studies have tested the potential for disturbance to mediate competition between engineers. We examined the capacity for disturbance and habitat modification to explain the disjunct distributions of two benthic ecosystem engineers, eelgrass Zostera marina and the burrowing ghost shrimp Neotrypaea californiensis, in two California estuaries. Sediment sampling in eelgrass and ghost shrimp patches revealed that ghost shrimp change benthic biogeochemistry over small scales (centimeters) but not patch scales (meters to tens of meters), suggesting a limited capacity for sediment modification to explain species distributions. To determine the relative competitive abilities of engineers, we conducted reciprocal transplantations of ghost shrimp and eelgrass. Local ghost shrimp densities declined rapidly following the addition of eelgrass, and transplanted eelgrass expanded laterally into the surrounding ghost shrimp-dominated areas. When transplanted into eelgrass patches, ghost shrimp failed to persist. Ghost shrimp were also displaced from plots with structural mimics of eelgrass rhizomes and roots, suggesting that autogenic habitat modification by eelgrass is an important mechanism determining ghost shrimp distributions. However, ghost shrimp were able to rapidly colonize experimental disturbances to eelgrass patch edges, which are common in shallow estuaries. We conclude that coexistence in this system is maintained by spatiotemporally asynchronous disturbances and a competition-colonization trade-off: eelgrass is a competitively superior ecosystem engineer, but benthic disturbances permit the coexistence of ghost shrimp at the landscape scale by modulating the availability of space.

Factors Affecting the Distribution Patterns of Benthic Invertebrates at a Major Shorebird Staging Site in the Yellow Sea, China

The tidal flats of the Yellow Sea support benthic communities that are vitally important to migratory birds, but baseline information on benthic community structure and variability is largely lacking. We investigated spatial and temporal patterns of macrobenthic invertebrates in areas used by large numbers of shorebirds and how these patterns related to environmental factors at Yalu Jiang coastal wetland in the north Yellow Sea during boreal spring (March–May) from 2010 to 2012. At least 61 species were documented during the study. Monthly benthos sampling from 54 stations indicated that polychaetes and bivalves dominated the benthic communities, with capitellid or maldanid polychaetes dominating upper tidal flats and the bivalve Potamocorbula laevis dominating intermediate and lower tidal flats. The middle and eastern sites approximately 10 km apart showed substantial differences in benthic species abundance and distribution, with bivalves dominating in the middle but not the eastern site. The spatial distribution of benthos was correlated with both exposure time during the tidal cycle and sediment particle size. Benthic communities showed both annual and within season variation. Two of the frequent prey for migratory birds, namely ghost shrimps Nihonotrypaea japonica and young Potamocorbula laevis, were relatively common in 2010 and 2011, respectively, but not in 2012.

Additional record of Rayllianassa amboinensis (de Man, 1888) from Japan, and description of a new species from Okinawa Island, Ryukyu Islands (Crustacea: Decapoda: Axiidea: Callianassidae).

Two species referred to the callianassid ghost shrimp genus Rayllianassa Komai & Tachikawa, 2008 are reported herewith. Additional locality records from Japan are provided for R. amboinensis (de Man, 1888), and the synonymy of Callianassa ngochoae Sakai, 1999 with R. amboinensis is discussed. It is shown that R. amboinensis is associated with sponges or alcyonacean soft corals, representing unusual habitats for callianassids. Rayllianassa rudisulcus n. sp. is described on the basis of a single ovigerous female from shallow soft sediment in Ohura Bay, Okinawa Island, Ryukyu Islands. The new species is distinguished from R. amboinensis by the absence of a dorsal oval on the carapace, the antennal peduncle being longer than the antennular peduncle, and the different shape of the third maxilliped. The status of Rayllianassa is also briefly discussed.

A new species of Leptalpheus Williams, 1965 and new records of L. mexicanus Ríos & Carvacho, 1983 and L. hendrickxi Anker, 2011 (Crustacea: Decapoda: Alpheidae) from the Pacific coast of Mexico.

A new species of Leptalpheus is described from Estero Pérula, Jalisco, on the Pacific coast of Mexico. Leptalpheus corderoae sp. nov. is most similar to Leptalpheus azuero Anker, 2011 from Panama and Leptalpheus axianassae Dworschak & Coelho, 1999 from Brazil, differing from both of them by a combination of morphological characters, especially the presence of tubercles on the ventral surface of the major chela palm and pollex. The most common host of L. corderoae sp. nov. at the type locality is the callianassid ghost shrimp Lepidophthalmus bocourti (A. Milne Edwards, 1870). Additional specimens of Leptalpheus mexicanus Ríos & Carvacho, 1983, from Estero de Urías, Sinaloa, are reported and compared to the type material from Río Mulegé, as well as to Leptalpheus bicristatus Anker, 2011 from Panama. Finally, Leptalpheus hendrickxi Anker, 2011 is reported from Mexico for the first time, representing a significant northward range extension of the species. In Estero Pérula, L. hendrickxi lives in burrows of Lepidophthalmus bocourti, sometimes together with L. corderoae sp. nov.

Prey Availability, and not Energy Content, Explains Diet and Prey Choice of Eastern CurlewsNumenius madagascariensisin Southern Australia

Eastern Curlews breed in Siberia in the boreal spring and summer and migrate to Australia in the austral spring and summer. The Eastern Curlew is notable for its very long, decurved bill; this sexually dimorphic characteristic represents approximately 25–30% of total body length. Female curlews have the longest bill of any wader. Diet and prey choice in relation to availability and profitability were examined over two non-breeding periods in Western Port in southern Australia. Diet was determined from direct feeding observations, examination of pellets collected at high-tide roosts (during daytime and night-time) and by following tracks of foraging curlews. Male and female curlews used the intertidal feeding areas differently: females used more sandy areas and males more muddy areas. This difference may be related to sexual dimorphism in bill length and could reflect substantial dietary differences. Tasselled Crab Pilumnus fissifrons was the most common prey, followed by Australian Ghost Shrimp Trypaea au...

Complete mitochondrial genome of the hydrothermal vent ghost shrimp Paraglypturus tonganus (Crustacea, Axiidea, Callianassidae)

Ghost shrimps are burrowing decapods that serve as bioturbators and habitat providers in seafloor environments. The hydrothermal vent ghost shrimp, Paraglypturus tonganus, was collected from a hydrothermal vent in the Tonga Arc. This species has a mitochondrial genome (mitogenome) of 15,924 bp in length with an AT content of 66.1%. The mitogenome was identical to the typical gene arrangement and transcriptional polarity of the infraorder Axiidea. Paraglypturus tonganus showed 65.3–70.1% nucleotide similarity with the known mitogenomes of other axiid shrimps. These results are useful for understanding the phylogenetic relationships among the members of Axiidea within the decapods.

Ghost shrimp Calliax de Saint Laurent, 1973 (Decapoda: Axiidea: Callianassidae) in the fossil record: systematics, palaeoecology and palaeobiogeography.

Ghost shrimps of the family Callianassidae are very common in the fossil record, but mostly as isolated cheliped elements only. The assignment to biologically defined genera, diagnosed on the basis of soft part morphology, is thus rather difficult. In this respect, proxy characters present on chelipeds that are the most durable ghost shrimp remains are needed to ascribe fossil material to extant genera. The genus Calliax de Saint Laurent, 1973 has been particularly obscure in this respect. Thorough comparison of extant members of the genus resulted in evaluation of characters present on chelipeds being taxonomically important on the genus level, specifically: 1) rectangular major P1 propodus with two ridges on the base of the fixed finger extending onto manus; 2) major P1 fingers relatively short; and 3) minor P1 chela with dactylus longer than fixed finger and possessing a wide gap between fingers. On this basis, Callianassa michelottii A. Milne Edwards, 1860, from the Oligocene and Miocene of Europe is herein reassigned to Calliax. Further re-examination of the ghost shrimp fossil record revealed that C. szobensis Müller, 1984, from the Middle Miocene of Hungary represents the same animal as C. michelottii and they are synomymised herein. The known geographic distribution of C. michelottii is expanded by the first confirmed occurrence of the species in Slovakia. All occurrences of C. michelottii known to date are reviewed and documented. The presence of Calliax michelottii comb. nov. may be considered an indicator of deeper marine settings. Based on the scarce fossil record known to date, Calliax has a Tethyan origin; it supposedly migrated westward to establish present day communities in the Caribbean sometime before the Middle Miocene.

Evolution of Crustaceans at the edge of the end-Permian crisis: Ichnonetwork analysis of the fluvial succession of Nurra (Permian–Triassic, Sardinia, Italy)

Decapod crustaceans are among the most efficient ecosystem engineers of the Phanerozoic, but the path that led to their engineering success is poorly known. The Permian–Triassic continental succession of Nurra (early Cisuralian–early Middle Triassic; Sardinia, Italy) sheds light on this obscure subject, because it preserves the oldest (Roadian) fluvial Ophiomorpha and Camborygma, ascribed to ghost shrimps (Decapoda: Axiidea, Gebiidea) and crayfishes (Decapoda: Astacidea, Parastacidea), respectively. These crustacean trace fossils are part of a well-preserved ichnofauna including Arenicolites, Diplocraterion, Helminthoidichnites, Palaeophycus, Planolites, rhizoliths, Skolithos, Spongeliomorpha, Taenidium, Treptichnus, alongside an undetermined tetrapod footprint, helical burrows and Sinusichnus-like traces.In light of the abundance of crustacean trace fossils, the Cala Viola section (Roadian–Anisian) was selected for ichnonetwork analysis. This novel approach, focusing on the topology of the association relationships of ichnotaxa, revealed six ichnoassociations, i.e., Rhizohaloes, Taenidium/Ophiomorpha, Helminthoidichnites, Palaeophycus, Skolithos and Arenicolites ichnoassociations. In addition, ichnonetwork analysis shown that Camborygma and Ophiomorpha colonised adjacent, partially overlapping fluvial subenvironments, ranging from active fluvial channels to periaquatic overbanks. As the Nurra occurrences are penecontemporaneous of the astacid/thalassinid diversification (Carboniferous–Early Permian) and coeval with the appearance of crayfishes (Middle Permian), fluvial environments played an important role in the evolution of both crayfishes and ghost shrimps. The most parsimonious explanation of the observed scenario is that astacid–thalassinid diversification happened in fluvial environments between the Carboniferous and Early Permian, while ghost shrimps invaded marine environments at the Permian–Triassic boundary. In addition, ichnonetwork analysis revealed that the ichnological system simplified across the Permian–Triassic boundary, accounting for a structured Permian ecosystem and fragmented, stressed habitats during the Early Triassic. This scenario is explained by a progressive drying trend that dramatically changed the hydrological features across the Permian–Triassic boundary. This supports the crucial role of global warming in driving the end-Permian crisis and its prolonged recovery.

Assessment of benthic disturbance associated with stingray foraging for ghost shrimp by aerial survey over an intertidal sandflat

One notable type of bioturbation in marine soft sediments involves the excavation of large pits and displacement of sediment associated with predator foraging for infaunal benthos. Batoids are among the most powerful excavators, yet their impact on sediment has been poorly studied. For expansive tidal flats, only relatively small proportions of the habitat can be sampled due to physical and logistical constraints. The knowledge of the dynamics of these habitats, including the spatial and temporal distribution of ray bioturbation, thus remains limited. We combined the use of aerial photogrammetry and in situ benthic sampling to quantify stingray feeding pits in Tomioka Bay, Amakusa, Japan. Specifically, we mapped newly-formed pits over an 11-ha section of an intertidal sandflat over two consecutive daytime low tides. Pit size and distribution patterns were assumed to scale with fish size and reflect size-specific feeding behaviors, respectively. In situ benthic surveys were conducted for sandflat-surface elevation and prey density (callianassid shrimp). The volume versus area relationship was established as a logistic function for pits of varying sizes by photographing and refilling them with sediment. This relationship was applied to the area of every pit detected by air to estimate volume, in which special attention was paid to ray ontogenetic change in space utilization patterns. In total, 18,103 new pits were formed per day, with a mean individual area of 1060cm2. The pits were divided into six groups (G1 to G6 in increasing areas), with abundances of G1, G2+G3, and G4−G6 being medium, high, and low, respectively. Statistical analyses using generalized linear models revealed a marked preference for the higher prey-density areas in G1 and the restriction of feeding grounds of G4−G6 to the lower shore, with G2+G3 being generalists for prey density and sandflat elevation. The lower degrees of overall bioturbation by G1 and G4−G6 were spatially structured for the eight sub-areas demarcated by prey density and sandflat elevation, while G2+G3 homogenized the state over the sandflat. The newly-formed pits׳ sub-areal mean numerical, excavated-areal, and displaced-sediment-volume densities per day were confined to small ranges: 0.14–0.17m−2, 132–223cm2m−2, and 551–879cm3m−2 (latter two including 119 shallow non-pit excavations). These bioturbation rates are positioned at relatively high levels compared with those by rays from other geographic regions. The present procedure is applicable to the assessment of disturbance by any surface-sediment excavators on tidal flats if their pit dimensions are discernible from the air.

On the occurrence of Ctenocheles (Decapoda, Axiidea, Ctenochelidae) in the Bohemian Cretaceous Basin.

Because of close morphological affinities, fossil cheliped fragments of the ghost shrimp Ctenocheles (Decapoda, Axiidea, Ctenochelidae) can be easily misidentified as remains of different decapod crustacean taxa. Re-examination of the Cretaceous decapods deposited in the National Museum in Prague revealed that all supposed specimens of the lobster genus Oncopareia found in the Middle Coniacian calcareous claystones of the Březno Formation, including one of the Fritsch's original specimens of Stenocheles parvulus, actually belong to Ctenocheles. This material together with newly collected specimens from the same locality, allowed for erection of a new species, Ctenocheles fritschi. Its major chela possesses a serrated ischium and ovoid, unarmed merus; therefore, it is considered a close relative of the extant C. collini and C. maorianus. Ctenocheles fritschi sp. nov. represents the first report on the occurrence of the genus from the Bohemian Cretaceous Basin. It is one of the oldest records of Ctenocheles and simultaneously one of the best preserved fossils of the genus reported to date. Confusing taxonomy of S. parvulus is reviewed and shortly discussed.

Intertidal habitat utilization patterns of birds in a Northeast Pacific estuary

A habitat-based framework is a practical method for developing models (or, ecological production functions, EPFs) to describe the spatial distribution of ecosystem services. To generate EPFs for Yaquina estuary, Oregon, USA, we compared bird use patterns among intertidal habitats. Visual censuses were used to quantify abundance of bird groups and general species richness in: Zostera marina (eelgrass), Upogebia (mud shrimp)/mudflat, Neotrypaea (ghost shrimp)/sandflat, Zostera japonica (Japanese eelgrass), and low marsh estuarine habitats. Also assessed were (1) spatial variation within a habitat along the estuary gradient and, (2) temporal variation based on bi-monthly samples over a year at five tidal ranges. Z. marina was an important estuarine habitat based on nearly all metrics of bird use, except for shorebird densities. This suggests that reductions in native eelgrass habitat may reduce the abundance and diversity of birds in Yaquina estuary. Our results suggest that a habitat based assessment approach is generally feasible for developing relative EPFs related to the presence of birds within estuarine systems.

A collection of Callianassidea Dana, 1852 (Decapoda, Pleocyemata) from the Saudi Arabian Red Sea coast with a check-list of all ghost shrimps (Thalassinidea and Callianassidea) known from the area

During a survey of the coastal biodiversity of the Saudi Arabian Red Sea, four species of callianassid ghost shrimps were collected:Gilvossius bouvieri(Nobili, 1904),Neocallichirus mucronatus(Strahl, 1862a),Podocallichirus madagassus(Lenz & Richters, 1880), andCallianidea typaH. Milne Edwards, 1837. Of these,N. mucronatusis recorded from the Red Sea for the first time. With this new record, 29 species of the group are now known in the Red Sea fauna. The distribution of the species within the Red Sea is discussed in detail.

Modelling the variation in larval dispersal of estuarine and coastal ghost shrimp: Upogebia congeners in the Gulf of Cadiz

Modelling the variation in larval dispersal of estuarine and coastal ghost shrimp: Upogebia congeners in the Gulf of Cadiz

First record of Clausidium (Copepoda, Clausidiidae) from Brazil: a new species associated with ghost shrimps Neocallichirus grandimana (Gibbes, 1850) (Decapoda, Callianassidae)

A new clausidiid copepod was found living in galleries of ghost shrimps Neocallichirus grandimana (Gibbes, 1850) in Natal, Brazil. The new species resembles to Clausidium senegalense Humes, 1957 and Clausidium vancouverense (Haddon, 1912) in the armature of P2–P5 of the female, and shares with Clausidium senegalense similar segmentation and armature of the antenna and maxilla of the female. Nevertheless, it can be easily distinguished from its congeners by the unique characteristics observed in the antenna, maxilliped and first leg of males, as well as by the anal somite, maxillule and maxilliped of the females. This new species extends the group distribution to the Southwest Atlantic and represents the first record of the genus in Brazil. A key for the identification of the species based on females of Clausidium is provided.

Some peculiarities of the population biology of the ghost shrimp Nihonotrypaea petalura (Stimpson, 1860) (Decapoda: Callianassidae) in coastal waters of Vostok bay, the Sea of Japan

In June 2012, some features of the population biology of the ghost shrimp Nihonotrypaea petalura were studied first for the Russian waters in sublittoral populations of the Vostok Bay (Peter the Great Bay, Sea of Japan). It was found that N. petalura formed aggregations of an average density of 9–19 ind./m2 at the depth of 0.2–3 m on rocky and mixed bottoms. The biomass of the aggregations was 15–27 g/m2 or 1–33% of the average total biomass of macrozoobenthos, which included animals of 48 taxa. The maximum depth of the shrimp burrows was 52 cm. The populations consisted of animals with body lengths of 17–63 mm. In the size-frequency distribution, two peaks in the number, attributed to the shrimps of 24–29 and 39–48 mm size groups, were observed. The ratio of males to females almost did not vary with size and remained in general close to 1: 0.9 for the surveyed shrimp populations. The local differences in the studied parameters of N. petalura from the Vostok Bay, as well as from other areas of the range, are discussed in relation to features of the habitation of these animals that living in different biotopes.

Response of suspension-feeding clams to natural removal of bioturbating shrimp on a large estuarine intertidal sandflat in western Kyushu, Japan

On a 3.4-km2 intertidal sandflat in Ariake Sound, Japan, four phytoplankton-feeders were dominant in the benthic community in terms of abundance and biomass in spring–summer, 2004: ghost shrimp, Nihonotrypaea japonica, mud shrimp, Upogebia major, and clams, Ruditapes philippinarum and Mactra veneriformis, each occupying a specific one-fourth area of the sandflat. N. japonica is a deposit feeder, while the others are suspension feeders. N. japonica and U. major dwell in 0.7- and 2-m deep burrows, respectively. Subsequent monitoring conducted every spring during 2005 to 2008 revealed that (1) probably due to typhoon- and stingray-induced substratum disturbances for mud and ghost shrimp populations, respectively, these had greatly shrunk from their original mid- to low-tide habitat in 2005 and high- to mid-tide one in 2006, respectively, (2) vacated space was colonized by juveniles of both clams and a formerly subdominant, suspension-feeding clam, Meretrix lusoria, (3) only Ma. veneriformis and Me. lusoria were found as adults there, with R. philippinarum adults remaining limited to the low-tide zone, and (4) loss in sum total population biomasses due to that in the shrimp' was compensated by the gain in the clam species'. These findings suggest that the five species compete for (1) space, with superiorities exerted by shrimps to clams through the former's intense bioturbating activities and by Ma. veneriformis and/or Me. lusoria to R. philippinarum in the high- to mid-tide zone and vice versa in the low-tide zone, and (2) food to the limit of the carrying capacity provided by the sound. Furthermore, estimates were made of the benthic community biomass in the past based on a long-term record (or estimate) of chlorophyll-a concentrations (proxy measure for food) for the sound water column and of the R. philippinarum population biomass based on its fishery-landing record. The latter estimate would account for 60% of the former one in the late 1970s, when the first eutrophication is believed to have been in progress. The subsequent decrease in benthic community biomass was suggested in response to that in phytoplankton abundance, reaching the one-fourth level in 2004–2008. In the long run, three alternative states would have occurred in the benthic community, from (1) R. philippinarum population boom in the 1970s, through (2) remarkable increases in the populations of the shrimps and Ma. veneriformis in place of R. philippinarum in the early to mid-1980s, followed by a plateau until 2004, to (3) the one described here for the 2004–2008 period.

A new species of callianassid ghost shrimp of the genus Nihonotrypaea Manning & Tamaki, 1998 (Crustacea, Decapoda, Axiidea, Callianassidae) from southern part of the Russian coast of the Sea of Japan.

A new species of callianassid shrimp genus Nihonotrypaea Manning & Tamaki, 1998 (Crustacea: Decapoda: Axiidea: Callianassidae) is described from the Peter the Great Bay, Primorye, Russian coast of the Sea of Japan. The species clearly differs from other representatives of the genus by unique armature of ventral margin of merus and different form of carpus of major cheliped in males and yellow-greenish coloration never observed in other species of the genus Nihonotrypaea.

Marine organisms as heavy metal bioindicators in the Persian Gulf and the Gulf of Oman

In the present study, cadmium and lead concentrations were compared in barnacles, ghost shrimps, polychaetes, bivalves, and sediment from ten different locations along the intertidal zone of the Persian Gulf and the Gulf of Oman. The results revealed significant differences in the heavy metal concentrations between the organisms with barnacles showing, by far, the highest metal concentrations. The bioaccumulation factor of Cd in different animals follows this pattern with barnacles>bivalves>polychaetes>ghost shrimps, while the pattern for Pb was barnacles>polychaetes>bivalves>ghost shrimps. In most of the stations, sediments showed the lowest lead and cadmium concentrations. Therefore, it is concluded that barnacles with Pb concentrations between 0.17 and 2,016.1 μg/g and Cd concentrations ranging from 0.4 to 147.1 μg/g are the best organisms to be employed in monitoring programs designed to assess pollution with bioavailable metals in the Persian Gulf and the Gulf of Oman.

Morphological character changes through decapodid-stage larva and juveniles in the ghost shrimp Nihonotrypaea harmandi from western Kyushu, Japan: Clues for inferring pre- and post-settlement states and processes

Some decapod crustaceans release larvae from estuarine or coastal shores to coastal oceans. Decapodids (last-stage larvae) return home, settle, and metamorphose into juveniles I, which go through further instars. Several morphological characters degenerate or develop in response to lifestyle transitions. Using a burrow-dwelling callianassid shrimp, Nihonotrypaea harmandi, inhabiting an intertidal sandflat in a coastal boundary layer adjacent to coastal ocean, this study described morphological changes and drew inferences about states and processes in its early life history. Decapodid and juveniles were differentiated by linea thalassinica on carapace. In the laboratory, the decapodid stage lasted 3–6d. Given choice between sandy sediments from coastal ocean bed and adult habitat, decapodids exhibited no preference, suggesting broad receptiveness. The shortest durations of the juvenile-I, -II, and -III were estimated at 6d each. Starved decapodids normally metamorphosed into juveniles I, showing secondary lecithotrophy. The non-feeding state could be extended through the juvenile I (and possibly juvenile II), where the mean total lengths of shrimps reared in groups with food (diatoms) remained about 4.6mm. Post-settlement decapodids reared individually resumed feeding. The rostrum lengths in decapodids were ≥0.36mm on the initial two dates (Days 0 and 1), after which the mean values rapidly reduced to 0.30–0.36mm on Day 2 and below 0.30mm thereafter. The pereiopod exopods disappeared through the decapodid stage from four pairs to almost zero by Day 4. In the coastal ocean, no juveniles occurred, and almost all decapodids had rostrum lengths ≥0.30mm and 3 or 4 pereiopod exopods, suggesting their pre-settlement state. Of the smallest shrimps collected on the sandflat for their subsequent rearing there, 74% were estimated to be Day-0 or -1 decapodids based on their rostrum lengths. This and the laboratory experimental results suggest (1) the acquisition of competence for settlement by newly-metamorphosed decapodids while in the coastal ocean, which was nevertheless realized there and (2) their rapid transport by flood tidal currents from coastal ocean to sandflat. The newly-settled decapodids grew steadily at 0.2mmd−1 in total length. The reared juveniles reached the smallest adult size in 80d. The uropod expod changed from elliptical to sub-circular in shape markedly around the termination of the juvenile II or III, suggesting the acquisition of ventilating function for benthic life. Overall, the post-settlement shrimps can be staged by total-length ranges as 4–5.5mm for decapodids, 5.5–10mm for juveniles, and 10–20mm for sub-adults.