Genetic diversity and differentiation of nine populations of the hard clam (Meretrix petechialis) assessed by EST-derived microsatellites

BACKGROUND: Meretrix petechialis is one of the commercially important marine bivalves. In this study, we selected six highly polymorphic EST-derived microsatellite markers to assess the genetic diversity and population differentiation on nine wild populations of Meretrix petechialis. RESULTS: The number of alleles detected per-locus ranged from 4 to 30 (mean NA = 27.5) with a total of 165 alleles. The mean value of observed and expected heterozygosities varied from 0.717 to 0.861 and from 0.797 to 0.856, respectively. Meanwhile, the result of Neighbor-joining and overall FST = 0.214 (P < 0.01) reveled that M. petechialis populations from GX are the farthest populations, a certain degree of genetic variation among individuals in each population and the genetic differentiation is significant. CONCLUSIONS: GX population has high genetic diversity among individual, and there are certain differences in genetic characteristics among different populations. This study will provide a basis for the domestication and cultivation of genetic diversity of M. petechialis population and the protection of clam germplasm resources.

Parasitism by a Digenea in Lucina pectinata (Mollusca: Lucinidae) / Parasitismo por um Digenea em Lucina pectinata (Mollusca: Lucinidae)

Abstract Lucina pectinata is an important economic resource in the Brazilian coast. This study reports parasitism caused by a Digenea in this species. The specimens (n = 470) were collected in December 2012 in a mangrove swamp of the Cachoeira River estuary, Bahia, Brazil. They were measured along the anterior-posterior axis (length), and after macroscopic analysis for parasites and diseases cuts of 5 mm were fixated in Carnoy's solution and processed by routine histology technique wherein sessions of 7 μm were stained with Harris hematoxylin and eosin (H&E). The tissues were examined using an optical microscope. The mean length of L. pectinata was 4.0 ± 0.53 cm. Microscopic analysis showed sporocysts containing both germ balls as cercariae of an unidentified Digenea (Platyhelminthes), these in various stages of development. The prevalence was 1.48% (7/470). In a parasitized specimen was macroscopic evidence of tissue densification of gills. The sporocysts were observed in mantle, gills, digestive gland and gonads, with evident alteration/destruction of tissues, including parasitic castration. There were no other parasites found, which is probably related to inaccessibility and chemical conditions in which lives L. pectinata, i.e., between 10 and 20 cm in mangrove sediment.

Resumo Lucina pectinata é um importante recurso econômico na costa brasileira. Este estudo relata parasitismo causado por um Digenea nesta espécie. Os exemplares (n = 470) foram coletados em dezembro de 2012 em um manguezal do estuário do Rio Cachoeira, Ilhéus, Bahia. Estes foram medidos quanto ao eixo ântero-posterior (comprimento) e após análise macroscópica quanto a parasitos e enfermidades, cortes transversais de 5 mm foram fixados em solução de Carnoy e processados por técnica rotineira de histologia, sendo que sessões de 7 μm foram coradas com hematoxilina de Harris e eosina (HE). Os tecidos foram examinados em microscopia de luz. A média de comprimento de L. pectinata foi de 4,0 ± 0,53 cm. A análise microscópica evidenciou esporocistos de um Digenea (Platyhelminthes) não identificado, contendo massas germinativas e cercárias, estas em vários estágios de desenvolvimento. A prevalência foi de 1,48% (7/470). Um dos exemplares parasitado apresentou adensamento dos tecidos nas brânquias. Os esporocistos foram observados no manto, brânquias, glândula digestiva e gônadas, causando evidente alteração/destruição de tecidos, inclusive castração parasitária. Não foram observados outros parasitos, o que está provavelmente associado à inacessibilidade e condições químicas em que vive este hospedeiro, isto é, entre 10 e 20 cm no sedimento do manguezal.

Parasitism by a Digenea in Lucina pectinata (Mollusca: Lucinidae)

Abstract Lucina pectinata is an important economic resource in the Brazilian coast. This study reports parasitism caused by a Digenea in this species. The specimens (n = 470) were collected in December 2012 in a mangrove swamp of the Cachoeira River estuary, Bahia, Brazil. They were measured along the anterior-posterior axis (length), and after macroscopic analysis for parasites and diseases cuts of 5 mm were fixated in Carnoys solution and processed by routine histology technique wherein sessions of 7 m were stained with Harris hematoxylin and eosin (H&E). The tissues were examined using an optical microscope. The mean length of L. pectinata was 4.0 ± 0.53 cm. Microscopic analysis showed sporocysts containing both germ balls as cercariae of an unidentified Digenea (Platyhelminthes), these in various stages of development. The prevalence was 1.48% (7/470). In a parasitized specimen was macroscopic evidence of tissue densification of gills. The sporocysts were observed in mantle, gills, digestive gland and gonads, with evident alteration/destruction of tissues, including parasitic castration. There were no other parasites found, which is probably related to inaccessibility and chemical conditions in which lives L. pectinata, i.e., between 10 and 20 cm in mangrove sediment.

Resumo Lucina pectinata é um importante recurso econômico na costa brasileira. Este estudo relata parasitismo causado por um Digenea nesta espécie. Os exemplares (n = 470) foram coletados em dezembro de 2012 em um manguezal do estuário do Rio Cachoeira, Ilhéus, Bahia. Estes foram medidos quanto ao eixo ântero-posterior (comprimento) e após análise macroscópica quanto a parasitos e enfermidades, cortes transversais de 5 mm foram fixados em solução de Carnoy e processados por técnica rotineira de histologia, sendo que sessões de 7 m foram coradas com hematoxilina de Harris e eosina (HE). Os tecidos foram examinados em microscopia de luz. A média de comprimento de L. pectinata foi de 4,0 ± 0,53 cm. A análise microscópica evidenciou esporocistos de um Digenea (Platyhelminthes) não identificado, contendo massas germinativas e cercárias, estas em vários estágios de desenvolvimento. A prevalência foi de 1,48% (7/470). Um dos exemplares parasitado apresentou adensamento dos tecidos nas brânquias. Os esporocistos foram observados no manto, brânquias, glândula digestiva e gônadas, causando evidente alteração/destruição de tecidos, inclusive castração parasitária. Não foram observados outros parasitos, o que está provavelmente associado à inacessibilidade e condições químicas em que vive este hospedeiro, isto é, entre 10 e 20 cm no sedimento do manguezal.

Determination of Free Inorganic Cadmium Ions in Marine Bivalves by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry / 分析化学

Abstract A new method was established to determine the free inorganic cadmium ion ( Cd2+) in marine bivalves using high performance liquid chromatography and inductively coupled plasma mass spectrometry ( HPLC-ICP-MS) . The free Cd2+ in shellfish was ultrasonic extracted for 40 min by 10 mmol/L Tris buffer solution ( with 0. 1 mol/L NaCl, pH=7. 5), and the separation of Cd2+ was achieved using an IonPac CS5A analytical column with an IonPac CG5A guard column. The mobile phase consisted of 50 mmol/L C2 H2 O4 and 95 mmol/L LiOH. The new method had a good linear relationship with the correlation coefficient of 0. 999 and the standard recoveries of Cd2+ were all above 84. 6%. The free Cd2+ content in several kinds of marine bivalves was determined using the method and the results showed that the percentage of free inorganic Cd2+ to the total Cd content in samples with high Cd content was higher than those with low Cd content.