Population dynamics and production of the tropical freshwater shrimp Caridina nilotica (Decapoda: Atyidae) in the littoral of Lake Sibaya

SUMMARY. Seasonal changes in population structure, standing stock levels and production of Caridina nilotica were studied at three sites in the littoral margins of subtropical Lake Sibaya between January 1975 and March 1976. Average population density at these sites declined from a maximum of c. 1400 to a minimum of c. 350 individuals per m² (3.4–0.4 g m^?2 dry wt) during the study, possibly as a result of emigration into peripheral vegetation inundated by rising lake levels. Shrimps bred perennially and, although egg stocks and instantaneous birth rates (b) were highest during summer, no corresponding increases in populaton density were observed, suggesting that the seasonally higher birth rates were offset by higher mortality rates. Population size structure and size-specific sex ratios did not change seasonally to any marked extent. Relative abundance declined with size and females grew larger than males. Clutch size increased linearly as a function of female carapace length. Estimates of overall mean annual somatic production (g m^?2 year^?1 dry wt) for the three sites between January 1975 and January 1976 ranged between c. 132 (egg-ratio method), 37.5 (summation of growth increments) and 24 (Hynes-Hamilton method) at an annual mean standing stock level of 2.7 g m^?2 dry wt (calorific value, 20.34 kJ g^?1 dry wt). Production at sites 1, 2 and 3 decreased in line with declining annual mean standing stocks (5.32, 3.67 and 0.23 g m^?2, respectively). The growth increment method gave an overall mean annual P/B value of 13.9. Egg production amounted to a further 5.6, 3.6 and 0.1 g m^?2 year^?1 dry wt (calorific value, 28.01 kJ g^?1) at sites 1, 2 and 3, or 2.7 g m^?2 year^?1 on average.     

Early embryonic development of the freshwater shrimp Caridina multidentata (Crustacea,Decapoda, Atyidae)

Decapod crustaceans show a great diversity of developmental modes at all levels. In particular, early cleavage varies from total via mixed to superficial modes and from determinate cleavage with a stereotyped pattern to indeterminate cleavage. However, the ground pattern of early decapod development is not clear. To address this problem, we studied the early embryonic development of the caridean shrimp Caridina multidentata with a combination of confocal laser scanning microscopy, scanning electron microscopy, 4D microscopy and 3-D reconstruction software. Despite a yolk-rich egg, the cleavage is holoblastic and shows a distinct pattern of blastomere arrangement, characterized by two interlocking cell bands. This resembles the conditions in dendrobranchiate shrimps, which most likely are the sister group to Pleocyemata to which C. multidentata belongs. Hence, our results offer the possibility to assume total cleavage with blastomeres arranged in two interlocking cell bands as ancestral cleavage mode for Decapoda.     

Nested clade analysis of the freshwater shrimp, Caridina zebra (Decapoda: Atyidae), from north-eastern Australia

The freshwater shrimp, Caridina zebra, is endemic to montane rainforest streams of the Atherton Tableland, north-eastern Australia. As the confluences of many of the headwater streams are in unsuitable habitat, dispersal is expected to be highly restricted. Results from a previous allozyme survey for this species suggested that historical dispersal between separate river drainages had occurred due to rearrangements of the drainage lines at some stage in the recent past. The aim of this study was to use temporal information from the mitochondrial cytochrome oxidase subunit I (CO-I) gene to determine whether the observed genetic structure was a result of historical processes, or alternatively, due to low levels of terrestrial dispersal. The mitochondrial DNA (mtDNA) data were analysed using nested clade analysis, which can differentiate between historical fragmentation and range expansion vs. contemporary restricted gene flow. The results displayed three divergent clades that were likely to have arisen in allopatry. One widespread clade, with individuals in more than one river drainage, reflected a pattern of restricted gene flow. This suggests that this species is capable of terrestrial dispersal.     

Oxygen consumption in Caridina nilotica (Decapoda: Atyidae) in relation to temperature and size

SUMMARY. The oxygen consumption of shrimps ranging from 1 to 30 mg dry mass was determined at 18, 24 and 30°C using a continuous flow recording respirometer based upon a Clark-type oxygen electrode. Respiration (ascribed to routine metabolism) is described by the power curve: R = a M^b , ( R =μg O₂ h⁻¹, M = mg dry mass), which gives values of a = 1.632, 2.564 and 4.181, and b = 0.800, 0.898, and 0.793, at 18, 24 and 30°C respectively. The single expression, R = 0.008 T ^1.829 M ^0.830 provides a reasonable prediction of respiration as a combined function of shrimp size ( M ) and temperature (T, °C). Using an energy equivalent of 14.14 J mg O₂⁻¹ estimates of the energy requirements ( E , J h⁻¹ 10⁻³) of routine metabolism are given by the expression: E = 0.115 T ^1.829 M ^0.830.
Variability in oxygen consumption values between individuals is discussed and the observations on C. nilotica are compared with other crustacean studies.     

An island in the stream: Australia's place in the cosmopolitan world of Indo-West Pacific freshwater shrimp (Decapoda: Atyidae: Caridina)

Mitochondrial DNA sequences were used to investigate phylogenetic and biogeographic relationships among Australian freshwater shrimp from the genus Caridina H. Milne Edwards, 1837 (Atyidae) and congeners from potential source populations throughout the Indo-West Pacific region. Numerous Australian taxa have close evolutionary relationships with non-Australian taxa from locations throughout the region, indicating a diverse origin of the Australian freshwater fauna. This implies many colonisations to or from Australia over a long period, and thus highlights the surprising adeptness of freshwater shrimp in dispersal across ocean barriers and the unity of much of the region's freshwater biota. Interestingly, a study on Australia's other main genus of atyid shrimp, Paratya Miers, 1882, inferred only a single colonisation. A number of potential species radiations within Australia were also identified. This agrees with patterns detected for a large number of Australian freshwater taxa, and so implies a vicariant explanation due to the development of colder, dryer climates during the late Miocene/early Pliocene.     

Caridina bruneiana, a new species of freshwater shrimp (Decapoda, Caridea, Atyidae) from Negara Brunei Darussalam, Borneo

A new species of the freshwater atyid shrimp, Caridina bruneiana from Negara Brunei Darussalam, Borneo is described. Caridina bruneiana is characterized by its moderately long and deep rostrum, pereiopod shape, spination and segmental ratios, the shape and spination of its posterior telsonic margin, egg size and the presence of an appendix interna on the endopod of the first male pleopod. The distribution of atyid shrimps in forested streams and their possible use as bioindicators of stream water quality in tropical rainforests are briefly discussed.     

Isolation and characterization of 15 microsatellite loci from Caridina gracilipes (Atyidae, Decapoda)

Caridina gracilipes, an atyid shrimp of Taiwan, inhabits the fresh and brackish waters. Its life history can be classified into amphidromous and landlocked types. Recent human’s transportation has caused concerns of genetic contamination between these long evolved lineages and ecological instabilities. Molecular markers with high sensitivities are required for detecting the possible introgression due to human disturbance. In the study, we described the development of 15 polymorphic microsatellite loci in C. gracilipes for genetic and ecological studies. These new markers were tested in 20 individuals of three populations. The number of alleles ranged from 6 to 17. Expected (H _E) and observed (H _O) heterozygosities ranged from 0.653 to 0.954, averaged at 0.865, and from 0.000 to 0.4, averaged at 0.146, respectively. All loci are significantly deviated from Hardy–Weinberg expectations due to the heterozygote deficiency. Significant genetic differentiation among populations was detected based on F _ST values, which were estimated from 0.82 to 0.88. Chiao-Chuan Han and Cheng-Sheng Chang are contributed equally to this work.     

The relationship between egg size and embryonic and larval development in the freshwater shrimp Paratya australiensis Kemp (Decapoda: Atyidae)

1. Paratya australiensis egg and clutch sizes vary between lower and upper altitude sites within headwater streams of the Conondale Range, Queensland, Australia. The adaptive significance of this variation is examined by comparing the development of large eggs from upper sites with small eggs from lower sites at ambient temperatures in the laboratory. 2. Embryonic duration was not dependent on egg size, but was a function of temperature (28 days at 18 °C, but only 22 days at 21 °C). However, larvae developing from large eggs were significantly larger at all stages of development, larval duration was shorter and growth rate was faster than that of larvae from small eggs. 3. It is suggested that the larger, more rapidly developing larvae at upper altitude sites have a greater chance of maintaining position within headwater sections of the stream. This is important as physical barriers such as waterfalls may severely restrict upstream movement. At lower altitude sites, maintaining position may not be as critical as there are no major barriers to upstream movement following downstream displacement. The influence of temperature may also be important as larger eggs may be an adaptation to compensate for slower development of eggs and larvae at cooler, upper altitude sites. The advantage in completing larval development quickly is that larvae would have less risk of removal by spates occurring late in the breeding season.     

Inter- and intraspecific differences in the life history and growth of Caridina spp. (Decapoda: Atyidae) in Hong Kong streams

1. The life‐history pattern of three populations of Caridina cantonensis (Atyidae) and one population of Caridina serrata were studied in four Hong Kong streams: Pak Ngau Shek (PNS), Kap Man Hang (KMH), Pak Tam Chung (PTC), and Lung Fu Shan (LFS). Caridina cantonensis occurred at PNS, KMH and PTC while C. serrata was present at LFS only. Monthly quantitative sampling was carried out at each study site over 2 years to investigate life‐history patterns and cohort‐specific growth rates. 2. Breeding by both species was mainly restricted to the wet season, and there was an increase in the incidence of ovigerous females as water temperatures rose at the start of the summer monsoon. The number of cohorts and the frequency of recruitment of C. cantonensis (one to three times each year) were highly site‐specific, but consistent between years. 3. Shrimp growth was size‐dependent, and decreased with increasing body size. Caridina cantonensis at PTC had the highest cohort‐specific growth rates (0.05–0.14 mg ash‐free dry weight (AFDW) mg^?1 day^?1), followed by C. serrata at LFS (6% lower), and C. cantonensis at KMH and PNS (16–39% lower). Shrimp life spans exceeded 1 year (17–22 months), depending on site and species. 4. Sexual maturity occurred at an earlier age and at a smaller size in populations with higher growth rates. Shrimps at PTC and LFS matured at approximately 4 months old; this was 3 months earlier than at KMH and 5 months earlier than at PNS. Females of C. cantonensis at PTC and C. serrata at LFS may have bred twice during each breeding season, while females in the other two populations bred once only. The number of cohorts produced by each population in each year did not vary between the years of the study. Most sexually mature individuals only survived long enough (for 10–12 months after maturation) to breed during one season. 5. The mean brood size of C. cantonensis varied among streams and was 25–28% larger at PNS and KMH than at PTC. Egg size did not differ among populations. Larger brood sizes at PNS and KMH may have been a consequence of increased availability of algal food in these unshaded stream sites. Caridina serrata had similar egg and brood sizes to C. cantonensis, but females were smaller and reproductive investment was higher. Thus, the degree of intraspecific variation in atyid breeding in Hong Kong was at least equal to, if not greater than, the extent of interspecific variation. Interspecific differences in life history may reflect the frequency of droughts and spate intensity experienced by C. serrata at LFS.     

湖南淡水虾类两新种(十足目:匙指虾科:米虾属)

报道湖南省淡水匙指虾科米虾属两新种。窄肢米虾Caridina angustipes sp.now.与保靖米虾C.baojingensis Guo,He et Bai,1992近似,但新种额角长,上缘具15-27齿,下缘具3-6齿;雄性第一附肢内肢的内缘平直。棒肢米虾C.clavipes sp.nov.略似窄肢米虾C.angustipes,但目前雄性第一附肢内肢末端尖细,内缘刺少;雄性第二附肢雄附肢短而细,内缘仅具1刺,末端仅具4刺。正模标本保存在上海水产大学,副模标本保存在佛山科学技术学院。     

Variable growth rates of the tropical estuarine fish barramundi Lates calcarifer (Bloch) under different freshwater flow conditions

Relationships between freshwater flows and growth rates of the opportunistic predatory finfish barramundi Lates calcarifer in a dry tropical estuary were examined using data from a long-term tag-recapture programme. Lagged effects were not investigated. After accounting for length at release, time at liberty and seasonal variation ( e.g. winter, spring, summer and autumn), growth rates were significantly and positively related to fresh water flowing to the estuary. Effects were present at relatively low levels of freshwater flow ( i.e. 2·15 m³ s⁻¹, the 5th percentile of the mean flow rate experienced by fish in the study during time at liberty). The analysis, although correlative, provides quantitative evidence to support the hypothesis that freshwater flows are important in driving the productivity of estuaries and can improve growth of species high in the trophic chain.     

Toxicity of insecticides for control of freshwater Culex annulirostris (Diptera: Culicidae) to the nontarget shrimp, Caradina indistincta (Decapoda: Atyidae)

Laboratory evaluations were conducted in southeastern Queensland, Australia, to determine the toxicities of two organophosphate compounds (temephos and pirimiphos-methyl), an insect growth regulator (s-methoprene), and an entomopathogenic bacterium (Bacillus thuringiensis variety israelensis de Barjac [B.t.i.]) to Culex annulirostris (Skuse), an Australian freshwater mosquito vector of arboviruses, and to Caradina indistincta Calman, a co-habiting nontarget shrimp species. S-methoprene and B.t.i. were safest for Cx. annulirostris control with lethal dose ratios (LC95 nontarget/LC95 target) of 3,300 and 846,000, respectively. In contrast, lethal dose ratios for temephos and pirimiphos-methyl were 0.05 and 0.00005, respectively, suggesting that they are environmentally unsuitable. Based on their high lethal dose ratios, s-methoprene and B.t.i. are recommended for control of larval Cx. annulirostris in Australian freshwater habitats.     

Temperature Tolerances and Geographic Distribution of Three Species of Caridina (Decapoda,Atyidae) in Sri Lanka

The biokinetic zones of C. fernandoi, C. simoni and C. pristis were found to be 15–29 °C, 15–27 °C and 13–27 °C respectively, while their respective ranges of distribution were found to be in altitudes of 0–700, 0–700 and 450–850 m. Their responses to low temperatures indicate that all three species are unlikely to occur above 1,000 m. The lower limit of distribution of C. fernandoi and C. simoni extends to altitudes in which the temperature rises above their ultimate upper incipient lethal temperatures (UILT). They appear to avoid high temperatures by moving into cooler waters. C. pristis cannot do so since it lives in very shallow streams; the lower level of its distribution appears therefore to be limited by its UILT.     

Molecular phylogeny and diversification of freshwater shrimps (Decapoda, Atyidae, Caridina) from ancient Lake Poso (Sulawesi, Indonesia)--the importance of being colourful

Ancient Lake Poso on the Indonesian island Sulawesi hosts a highly diverse endemic fauna, including a small species flock of atyid Caridina shrimps, which are characterized by conspicuous colour patterns. We used a mtDNA based molecular phylogeny to test the assumption of a monophyletic origin and intralacustrine radiation of the species flock and to assess the species specificity of some colour morphs. Our data reveal a rapid radiation of Caridina in the entire Poso drainage system, but provide no strong evidence for a monophyletic radiation of the lake species. Nevertheless each lacustrine species shows a varying degree of substrate or trophic specialization, usually considered a hallmark of adaptive radiation. Two distinct colour forms previously attributed to a single species, C. ensifera, lack distinguishing qualitative morphological characters, but are shown to be two different species. In contrast, morphologically rather distinct lake species lacking specific colour patterns may be hybridizing with riverine taxa. These results suggest that colour may play a similar role in species recognition and possibly speciation in ancient lake Caridina as hypothesized, e.g. for some African cichlids.     

Facultative secondary lecithotrophy in the megalopa of the shrimp Lysmata seticaudata (Risso, 1816) (Decapoda: Hippolytidae) under laboratory conditions

Certain decapod crustaceans can catabolize internal reservesto undergo partial or full larval development. This featureis termed secondary lecithotrophy, if energy used results fromplankton derived organic matter accumulated by earlier larvalstages. The present work reports the ability of Lysmata seticaudatamegalopa to molt to the first juvenile stage in the absenceof food. Unlike previous records of secondary lecithotrophydisplayed by non-feeding last larval stages of hermit crabsand spiny lobsters, the megalopa of L. seticaudata retains itsfeeding capacity. This is the first time such a feature hasbeen reported in decapods, and the term facultative secondarylecithotrophy is proposed. The build up of energy reserves continuesduring the last zoeal stage of L. seticaudata, with starvedzoea IX failing to molt to megalopa. Energy reserves that enablestarved megalopa to molt to juvenile seem to be partially depleted,with starved juveniles produced either from starved or fed megalopaebeing unable to molt to the next juvenile stage. The longerresistance of starved juveniles produced from fed megalopae(nine days), compared to that of starved juveniles producedfrom starved megalopae (five days), indicates that some energyreserves may pass to the juvenile, not being totally depletedat metamorphosis.     

The effect of temperature on the post-embryonic growth of Neomysis intermedia Czernlawsky (Crustacea, Mysidacea) under laboratory conditions

The effect of temperature on post-embryonic growth of Neomysisintermedia was investigated under unlimited food conditionsin the laboratory. The effect of temperature on the size ofnewly released animals was negligibly small, but body size wasinversely related to temperature in adults. This was mainlycaused by the difference in the number of molts before maturation.The specific growth rate of N. intermedia increased exponentiallywith a temperature coefficient, Q₁₀ of 4.6 from 0.018 d^–13C to 0.21 d^–1 at 20C in juveniles, and with a temperaturecoefficient of 2.7 from 0.006 d^–1 at 3C to 0.05 d^–1at 25C in adults. The rate in juveniles levelled off above20C, and dropped at 29C. Brood size and brood interval decreasedwith temperature increase, while the daily specific reproductionrate increased. The specific growth rate of gravid females,including production of egg matter, increased exponentiallywith a temperature coefficient of 3.3 from 0.015 d^–1 at10C to 0.093 d^–1 at 25C. The present laboratory experiments confirmed the temperaturecontrol on the growth of N. intermedia suggested in a hyper-eutrophiclake.     

Genetic differentiation among populations of Caridinazebra (Decapoda: Atyidae) in tropical rainforest streams, northern Australia

1. Caridina zebra is a common atyid shrimp in some tropical rainforest streams in far north Queensland, Australia. Genetic variation at five allozyme loci was used to estimate the level of dispersal among populations of this species, within and between stream systems. Shrimps were sampled from nine streams in the Tully River catchment and two headwater streams in the adjacent Herbert River catchment in an area under consideration for extensive hydroelectric development.
2. High levels of genetic differentiation were recorded among most populations which suggests that, like other fully aquatic species, movement is limited to a very small spatial scale.
3. In the Tully catchment, populations of shrimp from streams with confluences at high altitude showed less genetic differentiation than those from streams which directly entered the lower river. Dispersal between the latter streams is clearly limited by the presence of large waterfalls and cascades.
4. Adjacent stream populations were often highly differentiated, despite their close proximity, suggesting that overland dispersal is unlikely. However, populations of shrimp in the two streams in the Herbert catchment were strikingly similar in genetic structure to those in adjacent headwater streams of the Tully. Such similarity may reflect relatively recent changes in drainage patterns.     

The complete mitochondrial genome of the Hawaiian anchialine shrimp Halocaridina rubra Holthuis, 1963 (Crustacea: Decapoda: Atyidae)

Shrimp of the family Atyidae are important members of nearly all tropical (and most temperate) fresh and brackish water ecosystems in the world. To date, a complete mitochondrial genome from this important crustacean group has not been reported. Here, we present the complete mitochondrial DNA sequence of the Hawaiian atyid Halocaridina rubra [Holthuis, L.B., 1963. On red coloured shrimps (Decapoda, Caridea) from tropical land-locked saltwater pools. Zool. Meded.16, 261-279.] (Crustacea: Decapoda: Atyidae). The genome is a circular molecule of 16,065 bp and encodes the 37 mitochondrial genes (13 protein-coding, 22 tRNAs, and two rRNAs) typically found in the metazoa. Gene order and orientation in the H. rubra mitochondrial genome is syntenic with most malacostracans that have been examined to date. Of special note is the absence of the dihydrouridine (DHU) arm stem from tRNA(Tyr) and the use of CCG as an initiation codon for cytochrome oxidase subunit I (COI); these represent the first reported examples of such phenomena in the Malacostraca. Phylogenetic analyses utilizing complete mitochondrial sequences from other malacostracans place H. rubra as sister to Macrobrachium rosenbergii, which also belongs to the Infraorder Caridea. However, the placement of this infraorder, as well as the Infraorder Dendrobrachiata, in the phylogeny of the Decapoda varied depending on outgroup selection. Data from additional mitochondrial genomes, such as basal decapods like the Stenopodidea, should contribute to a better overall understanding of decapod phylogenetics.     

The limits of cryptic diversity in groundwater: phylogeography of the cave shrimp Troglocaris anophthalmus (Crustacea: Decapoda: Atyidae)

Recent studies have revealed high local diversity and endemism in groundwaters, and showed that species with large ranges are extremely rare. One of such species is the cave shrimp Troglocaris anophthalmus from the Dinaric Karst on the western Balkan Peninsula, apparently uniform across a range of more than 500 kilometres. As such it contradicts the paradigm that subterranean organisms form localized, long-term stable populations that cannot disperse over long distances. We tested it for possible cryptic diversity and/or unexpected evolutionary processes, analysing mitochondrial (COI, 16S rRNA) and nuclear (ITS2) genes of 232 specimens from the entire range. The results of an array of phylogeographical procedures congruently suggested that the picture of a widespread, continuously distributed and homogenous T. anophthalmus was wrong. The taxon is composed of four or possibly five monophyletic, geographically defined phylogroups that meet several species delimitation criteria, two of them showing evidence of biological reproductive isolation in sympatry. COI genetic distances between phylogroups turned out to be a poor predictor, as they were much lower than the sometimes suggested crustacean threshold value of 0.16 substitutions per site. Most results confirmed the nondispersal hypothesis of subterranean fauna, but the southern Adriatic phylogroup displayed a paradoxical pattern of recent dispersal across 300 kilometres of hydrographically fragmented karst terrain. We suggest a model of migration under extreme water-level conditions, when flooded poljes could act as stepping-stones. In the north of the range (Slovenia), the results confirmed the existence of a zone of unique biogeographical conflict, where surface fauna is concordant with the current watershed, and subterranean fauna is not.     

Geographical distributions of mitochondrial DNA lineages reflect ancient directions of river flow: a case study of the Japanese freshwater shrimp Neocaridina denticulata denticulata (Decapoda: Atyidae)

The mitochondrial DNA phylogeographical structure of the freshwater atyid shrimp Neocaridina denticulata denticulata was investigated near the Yura and Kako Rivers in western Japan. To assess the biological significance of drainage evolution, fragments of 390 base pairs (bp) extending from the NADH dehydrogenase subunit 2 gene to the tryptophan transfer RNA gene were sequenced for 246 specimens from twenty locations. The phylogenetic tree detected two distinct clades corresponding to the region along the Sea of Japan and Seto Inland Sea, respectively. Geographical mapping of the two clades well reflected the river capture, in which the upper reaches of the Yura River draining into the Sea of Japan had been captured from the Kako River into the Seto Inland Sea. The clear pattern of mitochondrial DNA distribution may be accounted for by the ecological characteristics of species that minimize passive downstream drift, local adaptation, and mountain topography.