Hwey-Lian Hsieh

Nucleotide Sequences of Ribosomal Internal Transcribed Spacers and Their Utility in Distinguishing Closely Related Perinereis Polychaets (Annelida; Polychaeta; Nereididae)

Abstract: Nucleotide sequences of a segment of the rRNA transcription unit spanning from the 3′ end of the 18S rDNA to the 5′ end of 28S rDNA were determined for four species of Perinereis polychaetes: P. aibuhitensis, P. floridana, and two undescribed species, Perinereis sp1 and sp2. The 5.8S rDNA sequences are identical among the four species. Intraspecific variability was low with the Kimura 2-parameter (K2P) distance, ranging from 0 to 0.0138 for ITS1 and 0 to 0.0247 for ITS2. The interspecific nucleotide difference was significantly higher than those within species, with a mean K2P of 0.172 for ITS1 and 0.204 for ITS2, suggesting that comparisons of ITS regions can be used to evaluate the phylogenetic relationships among Perinereis species. Both neighbor-joining and parsimony analyses of ITS variability indicate a close relationship between the two undescribed species of Perinereis. These findings highlight the utility of the ITS sequence in conjunction with other morphological and ecological characters to delineate species boundaries among closely related polychaetes.

Larval Growth of the Coconut Crab Birgus Latro with a Discussion on the Development Mode of Terrestrial Hermit Crabs

Abstract With intensified harvesting and environment deterioration during the past two decades, a rapid decline in the number of coconut crabs, Birgus latro, which is a protected species listed in the IUCN Invertebrate Red Data Book, has occurred on many islands. Thus, it is important to protect this species by establishing conservation areas and/or replenish natural population by larval cultivation. In this study, the development modes were analyzed and the effect of enriched diet on larval growth and survival were examined. Two types of zoeal development patterns were found. In general, zoeae took 29-33 days to complete five zoeal stages and metamorphose to glaucothoes. However, some zoeae directly metamorphosed from the 3rd zoeal to glaucothoe stage in 25∼28 days. Morphologically, these zoeae with accelerated development had thoracic appendages that appeared like the fifth stage zoeae, but with the telson, antennule, and antenna similar to those of the third stage zoeae. When fed Artemia nauplii enriched with nutritious substances, the zoeae had significantly greater survivorship and sizes, particularly at the fourth and fifth zoeal stages. Accelerated development may suggest early adaptation to a terrestrial lifestyle. The adaptation of larval development related to glaucothoe size and zoeal life span is also compared and discussed for eight terrestrial hermit crab species of Coenobitidae. The comparison suggests four adaptive modes of larval development and these are described as mangrove adaptation, larger glaucothoe adaptation, smaller glaucothoe adaptation, and hypersaline adaptation. The selective advantage of each mode may reflect a response to the uniqueness of each specific habitat.

Effects of semidiurnal tidal circulation on the distribution of holo- and meroplankton in a subtropical estuary

We examined how tidal changes and which physical factors affected holo- and meroplankton assemblages in a subtropical estuary in Taiwan in February 1999. A factor analysis showed that during tidal flooding, the water mass properties changed from low salinity (5–16) and high particulate organic carbon (POC, 2.6–4.5 mg L−1) content to increasing salinity and high total suspended matter content (29.0–104.5 mg L−1). With a receding tide, the water became more saline again, and its velocity increased (from non-detectable to 0.67 m s−1). One-way ANOVA showed that the distributions of four dominant taxa were affected by the ebb tide and exhibited two distinct groups. The first group consisted of non-motile invertebrate eggs and weakly swimming polychaete sabellid embryos and larvae (at densities of 1.25–1.40 ind. L−1), while the second consisted of better-swimming copepods and polychaete spionid larvae (at densities of 0.70–1.65 ind. L−1). A canonical correlation analysis demonstrated that the former group occurred at sites with greater freshwater input, higher POC content and greater depth, whereas the latter group was significantly associated with sites subject to seawater and faster flows. We propose that a two-layered circulation process and tidally induced oscillations in water movements might account for the distributional differences between these two groups.

Population Subdivision of the Tri-Spine Horseshoe Crab, Tachypleus tridentatus, in Taiwan Strait

Abstract The genetic structure of the Asian tri-spine horseshoe crab, Tachypleus tridentatus, was investigated in three populations of Taiwan Strait using mitochondrial (mt) AT-rich region DNA sequences. We examined 23 individuals from Kinmen, an island located on the western side of Taiwan Strait, and 12 each from Tiexianwei and Dongwei near Magong Island in the Penghu Archipelago, in the middle of Taiwan Strait. DNA sequence analysis of 369 base pairs (bp) of the mt AT-rich region revealed 10 haplotypes among the 47 individuals, with a mean haplotypic diversity (h) of 0.626± 0.075 and nucleotide diversity (π) of 0.0039± 0.00055. Pairwise F-statistics (FST) revealed significantly high gene flow between Kinmen and Dongwei (FST=–0.0351, p>0.05, Nem=∞), but marked population subdivision and restricted gene flow between Kinmen and Tiexianwei (FST=0.1382, p<0.05, Nem=3.1176). Between populations at Magong Island, gene flow was moderate (FST=0.0634, p>0.05, Nem=7.3913). Mismatch distribution analysis indicated that the relatively low haplotype and nucleotide diversity observed in the Tiexianwei T. tridentatus population can be attributed to a recent bottleneck, probably due to isolation of Tiexianwei in semi-closed Magong Bay that prevents gene flow from neighboring populations.

GONADAL STATE OF THE OYSTER CRASSOSTREA ANGULATA CULTIVATED IN TAIWAN

ABSTRACT Reproductive health of the common cupped oyster Crassostrea angulata cultivated in Taiwan was estimated through histological examination and semiquantitative analysis of their gonads. Oysters were collected in 4 aquaculture sites along the western coast of Taiwan (Hsiangshan, Chiku, Beimen, and Putai), where the major sources of industrial pollution are located, and off Penghu Island in the southern part of the Taiwan Strait, a comparatively clean resort area. The oysters from Hsiangshan had the lowest gonad maturity index (GMI) and the highest index of pathological alterations (IPA; P < 0.001); greater numbers of oysters with undifferentiated gonads (30%) and a green mantle (66.7%) were also present here. Most prominent gonad pathologies were atresia of oocytes and hemocytic infiltration of gonadal tissue. Oysters from Penghu had the highest GMI and the lowest IPA, whereas oysters from Chiku, Beimen, and Putai had intermediate values. Soft tissues of oysters from Hsiangshan contained 3,761.0 ± 1,201.0 µg/g dry weight Cu, 3,761.0 ± 1,201.0 µg/g Zn, and 1.5 ± 0.06 µg/g Cd, which is about 17 times, 3 times, and 1.5 times greater than the corresponding metal concentrations in the tissues of oysters from Penghu. Gametogenesis impairment in oysters cultivated in Taiwan are likely caused by environmental pollution.

Tungsten and other heavy metal contamination in aquatic environments receiving wastewater from semiconductor manufacturing

Through analyses of water and sediments, we investigate tungsten and 14 other heavy metals in a stream receiving treated effluents from a semiconductor manufacturer-clustered science park in Taiwan. Treated effluents account for ∼ 50% of total annual river discharge and <1% of total sediment discharge. Dissolved tungsten concentrations in the effluents abnormally reach 400 μg/L, as compared to the world river average concentration of <0.1 μg/L. Particulate tungsten concentrations are up to 300 μg/g in suspended and deposited sediments, and the corresponding enrichment factors are three orders of magnitude higher than average crust composition. Surprisingly, the estimated amount of tungsten exported to the adjacent ocean is 23.5 t/yr, which can approximate the amount from the Yangtze River should it be unpolluted. This study highlights the urgency of investigating the biological effect of such contamination.

Biotic communities of freshwater marshes and mangroves in relation to saltwater incursions: implications for wetland regulation

An ecosystem-level study was conducted in the Guandu wetlands insubtropical coastal Taiwan to examine how salinity influences the abundance,diversity, and structure of biotic communities. We surveyed eight permanentstudy sites, spanning freshwater marshes, to the gate on the dyke, andmesohaline mangroves representing a gradient of the extent of saltwaterincursions. Analyses of abiotic variables showed that salinity was the primarydetermining factor for discriminating habitat types in the wetlands, butcommunities differed in their sensitivity to salinity. The composition of plantand insect communities was most affected by the salinity gradient, suggestingthe utility of these communities for ecological monitoring of saltwaterincursions. However, spatial changes in communities at higher trophic levels,including macrobenthos, mollusks, fish, and birds, could not be explained simplyby the salinity gradient. Instead, changes in these communities were morerelevant to the composition of other biotic communities. Our results show thatspecies richness and diversity of plant communities were higher in the marshesthan in the mangroves. Nevertheless, insect communities censused in themangroves had higher diversity, despite lower abundance and species richness.Macrobenthos surveyed in the mangroves showed higher biomass and number of taxa.Mollusks and fish were also more abundant at sites near the gate compared to themarsh sites. This suggests that maintaining a tidal flux by means of gateregulation is necessary for conserving the spatial heterogeneity andbiodiversity of coastal wetlands.

Diversity and Composition of Sulfate- and Sulfite-Reducing Prokaryotes as Affected by Marine-Freshwater Gradient and Sulfate Availability

Sulfate- and sulfite-reducing prokaryotes (SSRP) communities play a key role in both sulfur and carbon cycles. In estuarine ecosystems, sulfate concentrations change with tides and could be limited in tidal freshwater reach or deep sediments. In a subtropical estuary of northern Taiwan in December 2007, we examined the compositional changes of SSRP communities. We examined three sites: from the lower estuarine brackish-water reach (site GR and mangrove vegetation site, GM) to the upper estuarine tidal freshwater reach (site HR), as well as from surface to a 50-cm depth. The partial sequence of sulfite reductase (dsrB) genes was used as a molecular marker of SSRP, linked to polymerase chain reaction and denaturing gradient gel electrophoresis (DGGE) techniques. SSRP communities of the DGGE profiles varied with sites according to one-way analyses of similarities (Global R = 0.69, P = 0.001). Using cluster analysis, the DGGE profile was found to show site-specific clusters and a distinct depth zonation (five, six, and two SSRP communities at the GM, GR, and HR sites, respectively). SSRP composition was highly correlated to the combination of salinity, reduced sulfur, and total organic carbon contents (BIO-ENV analysis, rs = 0.56). After analyzing a total of 35 dsrB sequences in the DGGE gel, six groups with 15 phylotypes were found, which were closely related to marine-freshwater gradient. Moreover, sequences neighboring sulfite-reducing prokaryotes were observed, in addition to those affiliated to sulfate-reducing prokaryotes. Four phylotypes harvested in HR resembled the genus Desulfitobacterium, a sulfite-reducing prokaryote, which failed to use sulfate as an electron acceptor and were active in freshwater and sulfate-limited habitat. The other five phylotypes in the HR reach belonged to the sulfate-reducing prokaryotes of the genera Desulfatiferula, Desulfosarcina, Desulfovibrio, and Desulfotomaculum, which appeared to tolerate low salinity and low sulfate supply. SSRP phylotypes at the mangrove-vegetated GM site (five phylotypes in two groups) were phylogenetically less diverse, when compared with those at the non-mangrove-vegetated GR site (three phylotypes in three groups) and the tidally influenced freshwater HR site (nine phylotypes in five groups). Phylotypes found at GR and GM were all affiliated to marine sulfate-reducing prokaryote strains of the genera Desulfofaba, Desulfobotulus, Desulfatiferula, Desulfosarcina, and Desulfotomaculum. Notably, a phylotype recorded in the surface sediment at GR resembled the genus Desulfobulbus, which was recorded from freshwater environment consisting of the freshwater input at GR during ebb tides.

Larval development and substrate preference at settlement in Pseudopolydora diopatra (Polychaeta: Spionidae)

Summary Natural populations of the spionid Pseudopolydora diopatra commonly inhabit tube-caps of the onuphid Diopatra bilobata and are rare in bare sand in Taiwan. Morphological changes during larval development and substrate preference by competent spionid larvae were studied in the laboratory from December 1990-January 1992. Larvae were planktotrophic and became competent to complete metamorphosis and settlement at the 12–15 setiger stage in 10–12 days when reared at 22–25°C. Competent larvae had fewer provisional setae but modified setae were present on the fifth setiger. In addition, the prototroch was still present, but the telotroch had disappeared. Experiments on substrate selection showed that larvae preferred the tube-caps of Diopatra to sand substrates. The physical characteristics of the tube-caps were architecturally complicated and rough on the surface. The tube-caps provided a stable, firm and long-lasting habitat for P. diopatra. When the tube-caps were disassembled, the larvae still favore...

Current Status of Tachypleus tridentatus in Taiwan for Red List Assessment

The horseshoe crab, Tachypleus tridentatus, once thrived on the west coast of Taiwan as evidenced by history, literature, colloquial language, daily usage and places named after it. After more than 15 years of efforts to conserve its populations, the horseshoe crab population remains threatened. A study on juvenile density changes in the Guningtou Horseshoe Crab Conservation Area in Kinmen Island showed that over 7 years from 2003 to 2009, the juvenile population declined rapidly from 0.30 individuals/m2 in 2003 to between 0.02 and 0.17 individuals/m2 in 2004–2009. Adult population surveys and scattered landing reports on fishing wharfs produced only about several tens individual catches at the most, implying a very limited adult distribution in waters surrounding Taiwan. The threats to T. tridentatus in Taiwan include habitat loss, habitat deterioration due to armored shorelines, pollution, Spartina invasion and human consumption. Conservation actions implemented include: habitat protection and improvement, population enhancement, education, and listing the horseshoe crab as a protected species. We now recommend designating new protected areas on the western and northeastern coasts of Kinmen Island as our studies show that these coasts possess beaches with the highest potential for spawning. We also strongly suggest that instars up to the third instar stage are appropriate for release, because they survive better in the field.