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Paralia (Bacillariophyta) stowaways in ship ballast: implications for biogeography and diversity of the genus.

MacGillivary ML, Kaczmarska I - J Biol Res (Thessalon) (2015)

Bottom Line: Frustule morphology did not segregate species, however, comparisons of sequence fragments and ITS2 secondary structures yielded a new species from North American waters, P. guyana (with four genodemes), and another widely-distributed species, P. marina.Despite this, as of 2009, P. marina was found only in Cheticamp, Nova Scotia, Canada.Second, genetic analysis readily segregated cryptic and semi-cryptic taxa of Paralia, highlighting the usefulness of the molecular approach to species recognition, e.g., in programs monitoring alien introductions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Mount Allison University, 63B York Street, Sackville, NB E4L 1G7 Canada.

ABSTRACT

Background: The genus Paralia Heiberg is one of the most recognizable, widely distributed and commonly reported diatoms from contemporary coastal marine environments and ship ballast. Species discovery has historically been made in diatoms through the recognition of morphological discontinuities between specimens, first using light and later electron microscopy. However, recently, morphologically semi-cryptic species of Paralia were delineated using genetic analyses, among mostly tropical and subtropical sites.

Results: Ten morphological characters of the frustules and sequence fragments from the nuclear genome (conserved 18S regions of ribosomal RNA and the variable internal transcribed spacer [ITS]), and from the RuBisCo large subunit (rbcL) gene of the chloroplast genome were examined. Frustule morphology did not segregate species, however, comparisons of sequence fragments and ITS2 secondary structures yielded a new species from North American waters, P. guyana (with four genodemes), and another widely-distributed species, P. marina. The latter was lecto- and epitypified here because it is most similar to specimens in the type preparation BM1021 representing Smith's concept of the species. Paralia marina and certain genodemes of P. guyana were morphologically cryptic. Only those genodemes of P. guyana that possess prickly separation valves could be morphologically distinguished from P. marina with relative confidence in SEM preparations. All clones established from chains isolated from the ballast sediment of the ships sailing along the Atlantic coast of North America belonged to P. guyana. All DNA sequences of preserved Paralia chains recovered from the three trans-Atlantic voyages (TAVs) samples arriving to eastern Canada from Europe shared 100% identity with P. marina.

Conclusion: First, if the [Formula: see text] = 130592 P. marina cells per ballast tank at the end of the TAVs represents their abundance in ballast tanks of similar crossings and following mid-ocean ballast water exchange, then this diatom, if de-ballasted, exerts a strong and continued propagule pressure on Eastern Canadian coasts. Despite this, as of 2009, P. marina was found only in Cheticamp, Nova Scotia, Canada. Second, genetic analysis readily segregated cryptic and semi-cryptic taxa of Paralia, highlighting the usefulness of the molecular approach to species recognition, e.g., in programs monitoring alien introductions.

No MeSH data available.


Related in: MedlinePlus

SEM images ofParalia marina. Epitype specimens, B40 0040792. (A-C) Mantle view. (A) Uru1. Profile of smooth and spineless separation valve with obscured fenestrae. (B) Helgo1. Interlocking noduliform protrusions of sibling separation valves. (C) Helgo3. Weakly silicified intercalary valves showing areolae perforating basal silica layer (arrow), siliceous outcroppings (black arrowheads) and external pores of rimoportulae (white arrowhead) which are usually more spaced apart than on this specimen; fenestrae unobscured. (D) Helgo1. Internal valve view with rimoportulae (arrow) and striae pores (arrowhead). Scale bars = 2 μm (A,C), 1 μm (B,D).
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Fig4: SEM images ofParalia marina. Epitype specimens, B40 0040792. (A-C) Mantle view. (A) Uru1. Profile of smooth and spineless separation valve with obscured fenestrae. (B) Helgo1. Interlocking noduliform protrusions of sibling separation valves. (C) Helgo3. Weakly silicified intercalary valves showing areolae perforating basal silica layer (arrow), siliceous outcroppings (black arrowheads) and external pores of rimoportulae (white arrowhead) which are usually more spaced apart than on this specimen; fenestrae unobscured. (D) Helgo1. Internal valve view with rimoportulae (arrow) and striae pores (arrowhead). Scale bars = 2 μm (A,C), 1 μm (B,D).

Mentions: In total, 76 clonal isolates and 18 chains of Paralia (approximately 2000 valves altogether) were investigated from natural sediment and plankton samples worldwide and from ship ballast sediments and waters arriving at Atlantic Canadian ports (TAVs; Table 1). Consequently, two species were recovered; a previously described, but broadly delineated entity, Paralia marina, lectotypified here, and a species new to science, P. guyana, represented by four genodemes. These taxa were all morphologically semi-cryptic or cryptic (Figures 1, 2, 3, 4, 5, 6, 7, and 8) and were most reliably delineated based on DNA sequence data analyses.Table 1


Paralia (Bacillariophyta) stowaways in ship ballast: implications for biogeography and diversity of the genus.

MacGillivary ML, Kaczmarska I - J Biol Res (Thessalon) (2015)

SEM images ofParalia marina. Epitype specimens, B40 0040792. (A-C) Mantle view. (A) Uru1. Profile of smooth and spineless separation valve with obscured fenestrae. (B) Helgo1. Interlocking noduliform protrusions of sibling separation valves. (C) Helgo3. Weakly silicified intercalary valves showing areolae perforating basal silica layer (arrow), siliceous outcroppings (black arrowheads) and external pores of rimoportulae (white arrowhead) which are usually more spaced apart than on this specimen; fenestrae unobscured. (D) Helgo1. Internal valve view with rimoportulae (arrow) and striae pores (arrowhead). Scale bars = 2 μm (A,C), 1 μm (B,D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4389653&req=5

Fig4: SEM images ofParalia marina. Epitype specimens, B40 0040792. (A-C) Mantle view. (A) Uru1. Profile of smooth and spineless separation valve with obscured fenestrae. (B) Helgo1. Interlocking noduliform protrusions of sibling separation valves. (C) Helgo3. Weakly silicified intercalary valves showing areolae perforating basal silica layer (arrow), siliceous outcroppings (black arrowheads) and external pores of rimoportulae (white arrowhead) which are usually more spaced apart than on this specimen; fenestrae unobscured. (D) Helgo1. Internal valve view with rimoportulae (arrow) and striae pores (arrowhead). Scale bars = 2 μm (A,C), 1 μm (B,D).
Mentions: In total, 76 clonal isolates and 18 chains of Paralia (approximately 2000 valves altogether) were investigated from natural sediment and plankton samples worldwide and from ship ballast sediments and waters arriving at Atlantic Canadian ports (TAVs; Table 1). Consequently, two species were recovered; a previously described, but broadly delineated entity, Paralia marina, lectotypified here, and a species new to science, P. guyana, represented by four genodemes. These taxa were all morphologically semi-cryptic or cryptic (Figures 1, 2, 3, 4, 5, 6, 7, and 8) and were most reliably delineated based on DNA sequence data analyses.Table 1

Bottom Line: Frustule morphology did not segregate species, however, comparisons of sequence fragments and ITS2 secondary structures yielded a new species from North American waters, P. guyana (with four genodemes), and another widely-distributed species, P. marina.Despite this, as of 2009, P. marina was found only in Cheticamp, Nova Scotia, Canada.Second, genetic analysis readily segregated cryptic and semi-cryptic taxa of Paralia, highlighting the usefulness of the molecular approach to species recognition, e.g., in programs monitoring alien introductions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Mount Allison University, 63B York Street, Sackville, NB E4L 1G7 Canada.

ABSTRACT

Background: The genus Paralia Heiberg is one of the most recognizable, widely distributed and commonly reported diatoms from contemporary coastal marine environments and ship ballast. Species discovery has historically been made in diatoms through the recognition of morphological discontinuities between specimens, first using light and later electron microscopy. However, recently, morphologically semi-cryptic species of Paralia were delineated using genetic analyses, among mostly tropical and subtropical sites.

Results: Ten morphological characters of the frustules and sequence fragments from the nuclear genome (conserved 18S regions of ribosomal RNA and the variable internal transcribed spacer [ITS]), and from the RuBisCo large subunit (rbcL) gene of the chloroplast genome were examined. Frustule morphology did not segregate species, however, comparisons of sequence fragments and ITS2 secondary structures yielded a new species from North American waters, P. guyana (with four genodemes), and another widely-distributed species, P. marina. The latter was lecto- and epitypified here because it is most similar to specimens in the type preparation BM1021 representing Smith's concept of the species. Paralia marina and certain genodemes of P. guyana were morphologically cryptic. Only those genodemes of P. guyana that possess prickly separation valves could be morphologically distinguished from P. marina with relative confidence in SEM preparations. All clones established from chains isolated from the ballast sediment of the ships sailing along the Atlantic coast of North America belonged to P. guyana. All DNA sequences of preserved Paralia chains recovered from the three trans-Atlantic voyages (TAVs) samples arriving to eastern Canada from Europe shared 100% identity with P. marina.

Conclusion: First, if the [Formula: see text] = 130592 P. marina cells per ballast tank at the end of the TAVs represents their abundance in ballast tanks of similar crossings and following mid-ocean ballast water exchange, then this diatom, if de-ballasted, exerts a strong and continued propagule pressure on Eastern Canadian coasts. Despite this, as of 2009, P. marina was found only in Cheticamp, Nova Scotia, Canada. Second, genetic analysis readily segregated cryptic and semi-cryptic taxa of Paralia, highlighting the usefulness of the molecular approach to species recognition, e.g., in programs monitoring alien introductions.

No MeSH data available.


Related in: MedlinePlus