Phosphoglucose isomerase polymorphism in the freshwater crab Sesarma boulengeri

Three phenotypes of phosphoglucose isomerase (PGI) were detected in abdominal muscle extracts from freshwater crab (Sesarma boulengeri) by starch-gel electrophoresis. The observed phenotypes were assumed to be under the control of two allelic genes. This assumption was supported by the observed distribution of phenotypes. There were no significant differences in PGI phenotype distribution among samples of crab taken from Karmat Ali, and Abu Al-Khasib locations along Shatt Al-Arab River. The three PGI alleles observed in S. boulengeri appear to be the same in specimens from the two locations.     

Abundance and seasonal migrations of the penaeid shrimp Metapenaeus affinis (H. Milne-Edwards) within Iraqi waters

Migration of Metapenaeus affinis (H. Milne-Edwards) from the Arabian Gulf to nursery grounds in the inland waters of Iraq extends from May/June to January/February. Shrimp ranging in size from 3–125 mm total length were found in inland waters. In the shallow waters of the Al-Assaflya small-sized shrimp only were caught, while in the Marshes large-sized shrimp were abundant. Maximum numbers of recruits were recorded when temperatures reached 23–25 °C. However, the discharge of the Shatt Al-Arab may also be an important factor regulating recruitment.The growth rates of small shrimp were higher than those of large ones. There mostly was, a preponderance of females over males. Spawning at sea appears to occur immediately after emigration. Gonad development was not observed. Commercial landings, at the two main fish markets at Basrah, during September–November 1985 averaged 1000 kg day^–1.     

Characterization of brown spot disease of gulf coast shrimp

Adult penaeid shrimp were collected from mariculture raceways, holding tanks, and near-shore waters of Galveston Island, Texas. Those with darkly pigmented lesions were chosen for study. When observed by scanning electron microscopy, diseased cuticle shows dense populations of bacteria within a lesion, whereas normal cuticle shows a relatively low number of bacteria. Some lesions exhibited a morphologically homogeneous population of bacteria while others revealed a heterogeneous or mixed infection. Bacteriological analysis of a homogenate of each lesion revealed the presence of a wide variety of organisms which produced extracellular lipases, proteases, and chitinases. Lipolytic and proteolytic organisms were consistently isolated from all 20 lesions examined, while chitinoclastic bacteria were found in all but two lesions. According to the presumptive isolation scheme used, 10 distinct phenotypes of bacteria were differentiated among the isolates from 20 lesions. These phenotypes were classified into four genera: Vibrio, Alteromonas, Spirillum, and Flavobacterium. Groups of 10 shrimp were abraded and inoculated with representative isolates from each of the 10 phenotypes. Four isolates were able to initiate lesion formation. These were two Vibrio species, one Alteromonas species, and one Spirillum species. All of these four pathogens were lipolytic, while only two were chitinoclastic. This evidence suggests that there is not one specific chitinoclastic bacterium which causes brown spot symptoms, but that a variety of bacteria acting alone or in groups may be the causal agents.     

A review of flying fishes of the subgenus Hirundichthys (Genus Hirundichthys, Exocoetidae). Part 2. Nerito-oceanic species: H. oxycephalus, H. affinis

The second part of the review of the subgenus Hirundichthys s.str. dealt with two nerito-oceanic species of the subgenus which have weakly pronounced “mirror” on the pectoral fins: H. oxycephalus and H. affinis. The validity of H. coromandelensis (Hornell, 1923) as a subspecies of H. oxycephalus is restored. A comparison of local populations showed that H. oxycephalus is a polytypic species and forms three subspecies: nominative H. oxycephalus oxycephalus from the Western Pacific and Eastern Indian Ocean, H. oxycephalus coromandelensis from the Arabian Sea, Bay of Bengal and adjoining waters of the Indian Ocean, and known by the only specimen from the waters of New Guinea H. oxycephalus frereensis ssp.n. Populations of H. affinis from the Western and Eastern Atlantic differ in the color of pectoral fins. Maps showing the geographical distribution of species and subspecies in the World Ocean are drawn up. A key for identification of species and subspecies belonging to the subgenus is proposed.     

Genetic structure analysis of mantis shrimp <Emphasis Type="Italic">Oratosquilla oratoria</Emphasis> based on mitochondrial DNA control region sequence

The genetic relationships of mantis shrimp Oratosquilla oratoria between the coastal waters of China and Japan were not well studied. To reveal the genetic differentiation and genetic structure among populations, we collected populations of mantis shrimp O. oratoria from the coastal waters of China and Japan to analyze the mtDNA control region variation. A total of 309 individuals of O. oratoria were collected from 13 localities (11 from China and 2 from Japan) and a segment of mitochondrial DNA control region was sequenced. Three hundred nine haplotypes were defined, yielding a very high haplotype diversity and nucleotide diversity. Two lineages of O. oratoria were revealed and displayed strong differences in the geographical distribution. In the coastal waters of China, the geographic distribution of the two lineages was completely separated by the Yangtze River estuary; however, the lineages showed geographic sympatry in two populations from Japan. Based on the lineage distribution, three groups were defined. There was no significant genetic differentiation among the populations within the three groups, indicating high gene flow within each group. Significant and negative values for Tajima D and Fu’s Fs tests, and mismatch distributions for two lineages indicated population expansion. The present result confirmed that the freshwater outflow from the Yangtze River formed a physical barrier and affected gene exchange. The different distribution patterns of the two lineages in coastal waters of China and Japan indicated that the larvae of O. oratoria were transferred from China to the coastal waters of Japan with a one-way gene flow.     

Diurnal dynamics of the microbial loop in peatlands: structure, function and relationship to environmental parameters

Globally, introductions of alien species are increasingly common, with invasive predators potentially having detrimental effects via predation on native species. However, native prey may avoid predation by adopting new behaviors. To determine whether invasive fish populations consume endemic shrimp in invaded Hawaiian anchialine habitats or if adopted patterns of diel migration prevents predation as previously hypothesized, a total of 183 invasive poeciliids (158 Gambusia affinis and 25 Poecilia reticulata) were collected for gut content analyses from four anchialine sites during wet and dry seasons on the islands of Hawai‘i and Maui. Predation on shrimp was not detected in habitats where they retreat exclusively into the underlying aquifer diurnally and only emerge nocturnally. However, low levels of predation were detected (7/65 fishes, only by Gambusia affinis) at Waianapanapa Cave, Maui, where shrimp retreat into both the aquifer and a cave during the day. Thus, adopted behavioral responses to invasive fishes generally, though not universally, prevent predation on endemic Hawaiian anchialine shrimps. However, non-consumptive effects resulting from behavioral modification of shrimps may have appreciable impacts on the Hawaiian anchialine ecosystem and warrant further study.     

Evidence for duplication and divergence of the structural gene for phosphoglucoisomerase in diploid species of clarkia

Formal genetic analysis of the mode of inheritance of the electrophoretic phenotypes for phosphoglucoisomerase (PGI) in the annual plants Clarkia rubicunda and C. xantiana showed that these diploid species have two and three genes, respectively, that specify PGI subunits. Electrophoretic examination of seven other diploid species of Clarkia revealed that species assigned to ancestral sections in the current taxonomy have two PGI genes, whereas more specialized species have three PGI genes. Together with evidence that diploid species in two closely related genera have two PGI genes, this suggests the third PGI gene arose within Clarkia. Intergenic heterodimers are formed between polypeptides specified by the third gene and one of the other PGI genes, indicating they have a high degree of structural similarity. The combined genetic, biochemical, and phylogenetic evidence suggests that the third PGI gene resulted from a process of gene duplication. The apparent Michaelis constants (F6P to G6P) of the most common electrophoretic variants of the ancestral gene in C. xantiana and in C. rubicunda are closely similar, but that of the duplicate enzyme is much higher. The intergenic heteromer has an intermediate value. Four alleles have been identified for the duplicate PGI gene in C. xantiana, including a null allele which eliminates the activity of its product. This allele is one of the few examples of a "silenced" duplicate gene. The ancestral and duplicate genes assort independently in C. xantiana. In conjunction with the substantial chromosomal rearrangements that characterize species of Clarkia, this may mean that the duplicate PGI marks a duplicated chromosomal segment that originated from a cross between partially overlapping reciprocal translocations rather than from unequal crossing over.     

Assessment distribution of the phytoplankton community structure at the fishing ground,Banyuasin estuary,Indonesia

The research objective was to describe the distribution of phytoplankton community structure and corelated to the physic-chemical parameters at fishing ground, Banyuasin estuarine waters. The methodology of research was phytoplankton sampling; physicochemical waters parameters data collected such as; dissolved oxygen, pH, temperature, brightness, salinity, current speed, nitrate, and phosphate. Identifications and calculations phytoplankton are based on photography under a light microscope. Data were analyzed by calculated abundance, diversity (H′ index) and dominance (C index), and Principal Component Analysis (PCA). There were 24 species of phytoplankton on the all-observation station grouped in three classes, Bacillariophyceae 91.3%, Dinophyceae 9%, and Cyanophyceae 0.1%. The abundance of phytoplankton species obtained in the range of 666.48 to 184,592.68 cells L^?1, were mostly found in high Chaetoceros affinis and Bacteriastrum furcatum. The distribution of phytoplankton abundance in these waters was found to be more influenced by seawater mass than freshwater. Phytoplankton diversity is considered a moderate category (1.37 < H′ < 2.57), and there were no species of phytoplankton that dominates (C < 0.5). Principal component analyzes showed that waters can be classified based on their physical-chemical characteristics, which were temperature, salinity, pH, transparency, current speed in the south coast around river estuaries, while DO and nutrients on the north coast of the waters. Based on the distribution of phytoplankton abundance is illustrated that the northern part is more potential for fishing area than the southern part with an abundance of phytoplankton >90,000 cells L^?1 and more stable water dynamics.     

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.     

Study on the Host–Parasite Relationship of Parapenaeopsis stylifera (H. Milne Edwards) (Decapoda:Penaeidae) and Parapenaeon japonica (Thielemann); (Isopoda:Bopyridae)

Thirteen species of penaeid shrimps, namely, Fenneropenaeus merguiensis, F. penicillatus, F. indicus, Penaeus semisulcatus, Metapenaeus affinis, M. monoceros, M. brevicornis, M. stebbingi, Parapenaeopsis stylifera, P. hardwickii, P. sculptilis, Parapenaeus longipes and Metapenaeopsis stridulans were examined in the present study. With the exception of Fenneropenaeus merguiensis and Parapenaeopsis stylifera no other shrimp species were found to be infected with bopyrids, the infection rate being 0.21% in F. merguiensis and 1.22% in P. stylifera. No marked change was observed in weight of the shrimps infected by bopyrids, however, a single male shrimp infected with bopyrid possessed a female like rostrum. All the infected male and female shrimps were found to be sexually immature.     

Diverse retrotransposon families and an AT-rich satellite DNA revealed in giant genomes of Fritillaria lilies

Background and Aims

The genus Fritillaria (Liliaceae) comprises species with extremely large genomes (1C = 30 000–127 000 Mb) and a bicontinental distribution. Most North American species (subgenus Liliorhiza) differ from Eurasian Fritillaria species by their distinct phylogenetic position and increased amounts of heterochromatin. This study examined the contribution of major repetitive elements to the genome obesity found in Fritillaria and identified repeats contributing to the heterochromatin arrays in Liliorhiza species.

Methods

Two Fritillaria species of similar genome size were selected for detailed analysis, one from each phylogeographical clade: F. affinis (1C = 45·6 pg, North America) and F. imperialis (1C = 43·0 pg, Eurasia). Fosmid libraries were constructed from their genomic DNAs and used for identification, sequence characterization, quantification and chromosome localization of clones containing highly repeated sequences.

Key Results and Conclusions

Repeats corresponding to 6·7 and 4·7 % of the F. affinis and F. imperialis genome, respectively, were identified. Chromoviruses and the Tat lineage of Ty3/gypsy group long terminal repeat retrotransposons were identified as the predominant components of the highly repeated fractions in the F. affinis and F. imperialis genomes, respectively. In addition, a heterogeneous, extremely AT-rich satellite repeat was isolated from F. affinis. The FriSAT1 repeat localized in heterochromatic bands makes up approx. 26 % of the F. affinis genome and substantial genomic fractions in several other Liliorhiza species. However, no evidence of a relationship between heterochromatin content and genome size variation was observed. Also, this study was unable to reveal any predominant repeats which tracked the increasing/decreasing trends of genome size evolution in Fritillaria. Instead, the giant Fritillaria genomes seem to be composed of many diversified families of transposable elements. We hypothesize that the genome obesity may be partly determined by the failure of removal mechanisms to counterbalance effectively the retrotransposon amplification.     

Population genetic structure of Penaeus monodon, in relation to monsoon current patterns in Southwest, East and Andaman coastal waters of India

The black tiger shrimp (Penaeus monodon), a commercially important penaeid species, is widely distributed across the Indo-Pacific region. Genetic diversity in P. monodon collected from eight geographical regions in Southwest, East and Andaman coastal waters of India (N = 418) was investigated using 10 polymorphic microsatellite loci. Average observed heterozygosity at sampled loci were high, ranging from 0.643 (Coromandel Coast) to 0.753 (South Andaman). Pairwise F_ST (ranged from 0.005 to 0.078) and R_ST (ranged from 0.005 to 0.171) estimates revealed surprisingly strong and statistically significant genetic structure among tiger shrimp populations. A synthetic map generated by multidimensional scaling shows an apparent cline in allele frequencies paralleling the roughly circular flow of surface currents in the Bay of Bengal. Significant heterozygote deficiencies were noted in most population samples at most loci. Andaman Island sites showed the highest diversity. Recognition of high genetic diversity and distinct population structuring of P. monodon in Indian seas has important implications for future domestication of this species in India, for two reasons: identification of the best wild founding stocks for aquaculture and, subsequently, the potential impacts of release of domesticates to the wild, either accidentally or deliberately (i.e. for stock enhancement).     

Long-term changes in the population of Eurytemora affinis (Copepoda,Calanoida) in the Gironde estuary (1978–1992)

Long-term changes in the population of Eurytemora affinis were investigated during 15 years (1978–1992) at a fixed station in the Gironde estuary (South West France). Total numbers, sex-ratio, % ovigerous females, proportion of copepodites and clutch-size were taken into account and their long-term distribution was related to temperature, river flow, salinity, suspended matter and chlorophyll a concentrations after the seasonal effect was removed for all variables.There was a great decrease of the river flow during the period of investigation, due to a general deficit in pluviosity. On the contrary, the general trend for salinity was an increase from 1978 to 1992. The same pattern was observed for chlorophyll, indicating an intrusion of marine phytoplankton. Water temperature increased significantly during the study period, following the general increase in air temperature observed in the area. For the suspended particulate matter (SPM), an increase was observed between 1978 and 1981–1982, then a very sharp decrease occurred from 1984 onwards.Numbers of E. affinis were inversely correlated with temperature and salinity, and positively correlated with the river flow. E. affinis was negatively correlated with chlorophyll concentration because of the covariation with salinity. No clear long-term trend was observed for the sex-ratio. A significant correlation was found between females carrying egg-sacs and SPM concentration, probably due to a decrease of the predation pressure in very turbid waters. The percentages of copepodites tended to decrease with time and were inversely correlated with temperature. Clutch-size significantly decreased during the 15-year period. This trend was mainly explained by temperature and salinity.It is concluded that, in the absence of strong human alteration in the Gironde estuary the long-term distribution of zooplankton can be explained by the natural environmental variability. The dominant factors are the river flow which governs the movement of the populations along the estuary and the temperature which influences the reproductive processes. Any change in climate will have consequences on the pelagic community.     

A review of flying fishes of the subgenus Hirundichthys (genus Hirundichthys, exocoetidae). 1. Oceanic species: H. speculiger, H. indicus sp. nova

A systematic revision of flying fishes of the subgenus Hirundichthys s.str was carried out based on a study of meristic and morphometric traits and characteristics of pigmentation of fishes from the local populations of species belonging to the subgenus. It is found out that the subgenus includes four species: oceanic H. speculiger from the Atlantic, Pacific and Indian Oceans, oceanic H. indicus sp.n. from the waters of the Indian Ocean, nerito-oceanic H. oxycephalus from the waters of the Indo-West Pacific and nerito-oceanic H. affinis from the Atlantic Ocean. The first part of the review focuses on two oceanic species with a large “mirror” on the pectoral fins: H. speculiger and H. indicus. A comparison of local populations showed that the species H. indicus is polytypic and consists of two subspecies. One of the subspecies—nominative H. indicus indicus—is distributed in the western and the central parts of the Indian Ocean and the other—H. indicus orientalis ssp.n.—in the Eastern Indian Ocean. Maps showing a geographical distribution of the species and the subspecies in the World Ocean are drawn up.     

Haplotype-specific single-locus multiplex PCR assay for molecular identification of sea-bob shrimp,Xiphopenaeus kroyeri (Heller, 1862), cryptic species from the Southwest Atlantic using a DNA pooling strategy for simultaneous identification of multiple samples

This work describes a single-locus multiplex PCR assay based on partial COI mitochondrial gene polymorphisms for identification of two Atlantic cryptic species of the sea-bob shrimp, Xiphopenaeus kroyeri (Heller, 1862) that were recently identified using molecular approaches. Reliable identification of cryptic species of Xiphopenaeus spp. has fundamental implications for management and conservation of the sea-bob shrimp fishery stocks. The assay was developed based on sequence polymorphisms of 130 specimens of both species, comprising samples from Venezuela to the southern coast of Brazil, validated by the amplification of 368 adult shrimp samples from nine different locations and confirmed by direct sequencing. The methodology has been optimized to enable the identification of equi-molar mixtures of DNA from up to 10 individuals by PCR reaction, allowing the fast and cheap identification of many specimens for large scale studies on fisheries biology and population genetics. The DNA pooling strategy enabled the identification of a new locality of occurrence of Xiphopenaeus sp. II in the Brazilian coast, Caravelas, indicating that the species distribution may be continuous on the coast, and not disjoint as observed so far.     

Implications of a fluctuating fish predator guild on behavior, distribution, and abundance of a shared prey species: the grass shrimp Palaemonetes pugio

In some systems, the identity of a prey species' dominant predator(s) may not be constant over time. In cases in which a prey species exhibits different responses to various predator species, such changes in predator identity may have population-wide consequences. Our goals were to determine (1) whether mortality of and refuge use by the grass shrimp, Palaemonetes pugio, were predator-specific, and (2) how effects of prey size and habitat interacted with predator type. Striped bass (Morone saxatilis) exerted twice as much predation pressure as mummichog (Fundulus heteroclitus), although not equally as great on large (female) and small (male) shrimp. Mummichog, which fed preferentially on large shrimp, forced a partitioning of habitat between the two shrimp size classes. In contrast, large and small shrimp occupied similar habitats when subjected to striped bass, which fed on both size classes equally. Refuge use of grass shrimp depended on predator type. In the presence of mummichog, which occupied shallower depths in the water column than striped bass, shrimp stayed deep and close to structural habitat. Striped bass, which were deeper, caused shrimp to move high in the water column away from structural habitat. When both predators were present, shrimp distribution was similar to that when only striped bass were present, striped bass predation rate was enhanced, and overall mortality was higher than with either predator alone. Results suggest that at times when mummichogs are the dominant predators, large (female) shrimp experience higher predation than small (male) shrimp and are physically separated from their potential mates. When striped bass are more abundant, male and female shrimp may share a similar, shallow, less structure-oriented distribution and be subjected to higher mortality. When both predators are present, mortality rates may be higher still. This predator-, size-, and habitat-specificity of grass shrimp behavior suggests significant population and distribution consequences of fluctuating predator guilds and fluctuating cover of structural habitats in the field.     

Interactions between the grass shrimp <Emphasis Type="Italic">Palaemonetes pugio</Emphasis> and the salt marsh grasses <Emphasis Type="Italic">Phragmites australis</Emphasis> and <Emphasis Type="Italic">Spartina alterniflora</Emphasis>

The grass shrimp Palaemonetes pugio, a species common to Spartina alterniflora-dominated marshes, may be sensitive to the invasion of the common reed Phragmites australis in northeastern US salt marshes. We examined two questions: (1) Do grass shrimp have a preference for the native plant over the non-native plant? (2) Are grass shrimp more effective foragers on P. australis? We tested the first hypothesis by comparing the amount of time shrimp spend in physical contact with the plant types over a 1-h period. Shrimp were observed under different arrangements of vegetation to control for differences in conspicuous structural features. Additionally, the amount of time shrimp spent foraging on S. alterniflora and P. australis shoots was compared to determine if shrimp graze more often on S. alterniflora. Shrimp spent significantly more time in contact with S. alterniflora only when plant types were grouped at opposite ends of aquaria, but did not exhibit a foraging preference for this plant type. To address our second question, we investigated the effects of shrimp foraging on stem epifauna, an assemblage of semi-aquatic invertebrates associated with macrophyte shoots. Previous research showed that P. australis supports a lower density of stem-dwelling epifauna relative to S. alterniflora. We hypothesized that the primary grazer of this community, P. pugio, can forage on P. australis stems more effectively due to structural differences between the two plants, causing the lower abundance of epifauna through top-down effects. We exposed individual shoots inhabited by epifauna to shrimp and compared faunal densities on exposed shoots to densities on control shoots after 18 h. The reduction of epifauna by predation was proportional on the two plant types. Therefore, top-down effects can be ruled out as an explanation for the patchy distribution of epifauna observed in P. australis–S. alterniflora marshes.     

Effects of large Saduria entomon (Isopoda) on spatial distribution of their small S. entomon and Monoporeia affinis (Amphipoda) prey

We performed laboratory experiments to investigate the effects of predator avoidance and numerical effects of predation on spatial distribution of small Saduria entomon (Isopoda) and Monoporeia affinis (Amphipoda), with large S. entomon as predators. The horizontal distribution and mortality of the prey species, separately and together, were studied in aquaria with a spatial horizontal refuge. We also estimated effects of refuge on mortality of small S. entomon and M. affinis by experiments without the refuge net. In addition, we investigated whether predation risk from large S. entomon influenced the swimming activity of M. affinis, to clarify the mechanisms behind the spatial distribution. Both small S. entomon and M. affinis avoided large S. entomon. The avoidance behaviour of M. fffinis contributed about 10 times more to the high proportion in the refuge than numerical effects of predation. Due to the low mortality of small S. entomon the avoidance behaviour of this species was even more important for the spatial distribution. The combined effect of avoidance behaviour and predation in both species was aggregation, producting a positive correlation between the species in density. M. affinis showed two types of avoidance behaviour. In the activity experiments they reduced activity by 36% and buried themselves in the sediment. In the refuge experiments we also observed avoidance behaviour with the emigration rate from the predator compartment being twice the immigration rate. The refuge did not lower predation mortality in M. affinis, probably due to the small scale of the experimental units in relation to the mobility of the species. Predation mortality in small S. entomon was higher in absence of a refuge and especially high in absence of M. affinis.     

Distribution of decapod larvae in the surface layer of an isolated equatorial oceanic archipelago: the cases of benthic Grapsus grapsus (Brachyura: Grapsidae) and pelagic Sergestes edwardsi (Dendrobranchiata: Sergestidae)

Two different decapod larval assemblages inhabit the marine environment of Saint Paul’s Rocks, differentiating the inlet from the surrounding oceanic waters. Larvae of the crab Grapsus grapsus and of the holopelagic shrimp Sergestes edwardsi are abundant in superficial waters of the archipelago and have previously been shown to be good indicators of the inlet and adjacent oceanic waters, respectively. We investigated the horizontal, diel and temporal distribution of these species at Saint Paul’s Rocks. Horizontal surface hauls were conducted from 2003 to 2005, in the inlet and at four increasing distances from the archipelago, in the morning and at night, using a 200-μm mesh net. Larvae of G. grapsus were identified in samples from all expeditions and abundance was found significantly higher at night in the inlet site. Only larvae in the first zoeal stage were found in samples, highlighting the importance of the area for this species reproduction. On the contrary, the distribution of larvae of S. edwardsi was typical of a holopelagic species, which are permanent residents of the water column and spawn in oceanic areas, indicating that the islands are of little influence to them.     

Molecular and Biochemical Diversity Among Isolates of Radopholus spp. from Different Areas of the World

Eleven isolates of Radopholus similis from various banana-growing areas around the world and one isolate of R. bridgei from turmeric in Indonesia were compared using DNA and isoenzyme analysis. The polymerase chain reaction (PCR) was used to amplify a fragment of ribosomal DNA (rDNA), comprising the two internal transcribed spacers (ITS) and the 5.8S gene. Restriction fragment length polymorphisms (RFLPs) in this rDNA fragment were used to compare the 10 isolates. The analysis of this rDNA region revealed little variation among the isolates tested. However, data also were obtained by random amplified polymorphic DNA (RAPD) analysis of total DNA, and a hierarchical cluster analysis of these data arranged the R. similis isolates into two clusters. The first cluster consisted of isolates from Nigeria, Cameroon, Queensland, and Costa Rica; the second was comprised of isolates from Guinea, Guadeloupe, the Ivory Coast, Uganda, and Sri Lanka. The isolate of R. bridgei from turmeric in Indonesia appeared to be more divergent. This grouping was consistent with that obtained when phosphate glucose isomerase (PGI) isoenzyme patterns were used to compare the R. similis isolates. The results from both RAPD analysis and PGI isoenzyme studies indicate that two gene pools might exist within the R. similis isolates studied. No correlation could be detected between the genomic diversity as determined by RAPD analysis and either geographic distribution of the isolates or differences in their pathogenicity. The results support the hypothesis that R. similis isolates have been spread with banana-planting material.