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  • 1
    Electronic Resource
    Electronic Resource
    Genetic evidence of self-fertilization in the sea anemone Epiactis prolifera (1984)
    Springer
    Marine biology 84 (1984), S. 175-182 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biochemical genetic variation provided evidence for the mode of reproduction of brooded young in the sea anemone Epiactis prolifera Verrill, 1869. Individuals of E. prolifera are female when small but hermaphroditic when large (i.e., gynodioecious); juveniles are brooded externally on the column. Brooding individuals collected from 6 intertidal sites (5 in central California and 1 in Washington State, USA) in the spring and summer of 1980 were assayed for gene-enzyme variation by starch-gel electrophoresis. Three of 12 enzyme loci were polymorphic; phosphoglucose isomerase appeared to be encoded by two, closely linked loci. Genotypic frequencies deviated markedly from expected random mating proportions. Only three heterozygotes were found; two were heterozygous at all three polymorphic loci, and the other was polymorphic at the two PGI loci. All 158 juveniles from 25 brooding individuals were assayed (2–19 juveniles per parent). Juveniles on homozygous adults were always identical to their parent. However, brooded young of heterozygous individuals were not identical to their parent. but showed 1:2:1 phenotypic segregation ratios consistent with reproduction by self-fertilization. This genetic evidence together with findings of marked heterozygote deficiencies and genetic identity of homozygous adults and their brooded young supports the conclusion that E. prolifera usually reproduces by self-fertilization, and cross-fertilization is rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393002
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular systematics of six Calanus and three Metridia species (Calanoida: Copepoda) (1995)
    Springer
    Marine biology 121 (1995), S. 655-664 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The discrimination of species of the copepod genus, Calanus (Copepoda; Calanoida), is problematical-especially in regions of sympatry. Although the species of Calanus exhibit exceptional morphological similarity, they are quite distinct in genetic character. The DNA base sequences of the mitochondrial large subunit (16S) ribosomal RNA (rRNA) gene unambiguously discriminated C. finmarchicus (Gunnerus 1765), C. glacialis (Jaschnov 1955), C. marshallae (Frost 1974), C. helgolandicus (Claus 1863), C. pacificus (Brodsky 1948), C. sinicus (Brodsky 1965), and C. hyperboreus (Kroyer 1838). Sequence differences among Calanus species for this gene portion range from 7.3% (between C. glacialis and C. marshallae) to 23.9% (between C. glacialis and C. sinicus). Differences among conspecific individuals were approximately 1 to 2%. [These sequence data were determined between April and November 1993; the sequenced domain is similar to that published previously in Bucklin et al. (1992) but are derived from analysis of additional individuals.] Statistical analysis of the sequence data using a variety of tree-building algorithms separated the taxa into one group of species corresponding to the C. finmarchicus group (C. finmarchicus, C. marshallae, and C. glacialis) and another ungrouped set of species corresponding to the C. helgolandicus group (C. helgolandicus, C. pacificus, and C. sinicus). The C. helgolandicus group may be older than the C. finmarchicus group, making the tree topology less reliable in this area. Calanus hyperboreus was an outlier; Nannocalanus minor (Claus 1863) was the outgroup. Similar analysis of Metridia species confirmed that M. lucens (Boeck 1864) and M. pacifica (Brodsky 1948) are distinct species; M. longa (Lubbock 1854) was still more divergent. These sequence data will allow the design of simple, molecular tools for taxonomic identifications. Diagnostic characters, assayed by rapid molecular protocols, will enable biological oceanographers to answer important questions about the distribution and abundance of all life stages (as well as patterns of reproduction) of morphologically similar species, such as those of Calanus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349301
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  • 3
    Electronic Resource
    Electronic Resource
    Distribution and relative abundance of Pseudocalanus moultoni and P. newmani (Copepoda: Calanoida) on Georges Bank using molecular identification of sibling species (1998)
    Springer
    Marine biology 132 (1998), S. 97-106 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sibling species, Pseudocalanus moultoni (Frost, 1989) and P. newmani (Frost, 1989), occur sympatrically on Georges Bank. Taxonomic discrimination of the species relies on subtle morphological characteristics, making routine identification of the species very difficult. DNA sequence variation of two mitochondrial genes, 16S rRNA and cytochrome oxidase I (COI), reliably discriminated P. moultoni and P.␣newmani. Levels of DNA sequence variation for both genes were consistent with those between species of calanoid copepods. A molecular systematic protocol (based on allele-specific PCR amplification) was designed from the COI sequences and used to discriminate females of the two species. The distributions and relative abundances of the two species were mapped for April 1996 based on samples of 15 to 30 females from 12 collections across Georges Bank. The results of this study indicated that P. moultoni females predominated along the northern flank of Georges Bank, while P. newmani females were common on the southern flank, deeper than the 60-m isobath.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050375
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  • 4
    Electronic Resource
    Electronic Resource
    Biochemical genetic evidence for a third species of Metridium (Coelenterata: Actiniaria) (1982)
    Springer
    Marine biology 66 (1982), S. 1-7 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Systematic relationships within the sea anemone genus Metridium have been problematical for many years. The genus has been considered to consist of a single, highly variable species, M. senile (L.), which has been divided into several somewhat arbitrary morphs. One, the “clonal” morph, is characteristically small, found in shallow water and reproduces both sexually and asexually. Another, the “solitary” morph, may grow very large, is found to great depths and has been thought to reproduce primarily, if not exclusively, sexually. The existence of a second species, M. exilis, described by Hand (1955), has been questioned (Riemann-Zuerneck, 1975). In the present study, the taxonomic status of the morphs and species of Metridium was examined by starch-gel electrophoresis to analyze genic variation at 16 enzyme loci in samples of the two morphs of M. senile and M. exilis collected at 3 locations on the Pacific coast of the USA (Bodega Bay, California; Monterey Bay, California; Puget Sound, Washington) and at 1 location on the Atlantic coast of the USA (Maine). Intrapopulation levels of gene enzyme variation were quite high (P 0.95=47.9,, and H=15.1), and some genetic differentiation among geographically separated populations of a single morph was seen, particularly between Atlantic and Pacific coast populations of the clonal M. senile. However, genetic differentiation (D) among pooled populations of M. exilis, clonal M. senile and solitary M. senile was much greater (D=1.14). Thus, the genus Metridium contains not one highly variable species but three distinct species, each with a relatively narrower ecological range and a relatively less variable morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397248
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic differentiation of populations of the planktonic copepod Labidocera aestiva (1985)
    Springer
    Marine biology 84 (1985), S. 219-224 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Planktonic populations of the calanoid copepod Labidocera aestiva show significant biochemical genetic heterogeneity along the Atlantic coast of the USA. In summer, 1981, copepods were collected by surface tows at Beaufort Inlet, North Carolina; Fort Pierce Inlet, Florida; and Vineyard Sound, Massachusetts. Genetic variation within each population and genetic differentiation among the three populations were studied by micro-acrylamide gel electrophoresis of six loci encoding four enzymes. All six enzyme loci were polymorphic when all populations were considered together, but the North Carolina population was monomorphic at two loci. High genetic variability was indicated by the following: (1) the number of alleles per locus averaged over all loci was 2.57±0.26 SD; (2) the average proportion of loci for which the frequency of the most common allele was not greater than 0.95 was 0.78±0.10; (3) the frequency of heterozygous individuals was 0.25±0.07. Genetic differentiation among population samples in the three regions was demonstrated in several ways: allele frequencies at one aminopeptidase-I locus, Lap-1, differed significantly among samples of the three populations, and there were unique alleles of high frequency at this locus in two population samples. Values of the statistic of genetic distance (D) averaged 0.20±0.08 for pairwise comparisons between all samples. Compared to expected heterozygosity if individuals across the entire range sampled mated at random, there were highly significant heterozygote deficiencies at five of the six loci. Genetic differentiation of populations of L. aestiva may result from (1) differential selection on populations in the three regions, or (2) restricted gene flow between the populations. Gene flow may be limited by geographic separation or differences in life history, such as seasonal presence in the plankton and diapause egg production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392490
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  • 6
    Electronic Resource
    Electronic Resource
    Taxonomic and systematic assessment of planktonic copepods using mitochondrial COI sequence variation and competitive, species-specific PCR (1999)
    Springer
    Hydrobiologia 401 (1999), S. 239-254 
    Details
    ISSN: 1573-5117
    Keywords: mitochondrial DNA ; cytochrome oxidase I ; competitive PCR ; copepoda ; taxonomy ; marine zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Accurate taxonomic identification of species at all life stages is critical to understand and predict the processes that together determine marine community dynamics. However, zooplankton assemblages may include numerous sibling and congeneric species distinguished by subtle morphological characteristics. Molecular systematic databases, including DNA sequences of homologous gene regions for selected taxonomic groups, allow the design of rapid protocols to determine species' diversity and identify individuals. In this study, the DNA sequence of a 300 base-pair region of the mitochondrial cytochrome oxidase I (COI) gene was determined for eight species of three genera of calanoid copepods: Calanus finmarchicus, C. glacialis and C. helgolandicus; Neocalanus cristatus, N. flemingeri and N. plumchrus; and Pseudocalanus moultoni and P. newmani. The DNA sequences differed between congeneric species by 13 – 22% of the nucleotides; the protein sequences differed by zero to five amino acid substitutions. Both the DNA and amino acid sequences resolved the evolutionary relationships among congeneric species; relationships among the genera were not well-resolved by this region of mtCOI. Using the same conserved primers, the only amplification product for C. finmarchicus was an aberrant sequence (and putative pseudogene) which differed from the C. finmarchicus COI sequence by 36% of the nucleotides and 32 amino acid substitutions. Species-specific oligonucleotide primers were designed for Calanus spp. (which cannot be distinguished at larval stages) and Pseudocalanus spp. (which are difficult to distinguish even as adults). Individual copepods were identified using competitive, multiplexed species-specific polymerase chain reactions (PCR) in two studies of co-occurring sibling species. The first study confirmed the presence of three Calanus spp. in Oslofjord, Norway and found a predominance of C. helgolandicus. The second study determined patterns of distribution and abundance of Pseudocalanus spp. on Georges Bank in the NW Atlantic and showed that P. moultoni predominated in shallow and coastal waters, while P. newmani was more abundant in offshore regions flanking the Bank. Competitive, species-specific PCR is a useful tool for biological oceanographers. This simple, rapid, and inexpensive assay may be used to identify morphologically-similar individuals of any size and life stage, and to determine a species' presence or absence in pooled samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003790411424
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