Characterization of macroalgal epiphytes on <italic>Thalassia testudinum</italic> and <italic>Syringodium filiforme</italic> seagrass in Tampa Bay, Florida

Won Boo Yeon; Yates Kim K.; Fredericq Suzanne; Cho Tae Oh

doi:10.4490/algae.2010.25.3.141

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Characterization of macroalgal epiphytes on Thalassia testudinum and Syringodium filiforme seagrass in Tampa Bay, Florida

DOI : 10.4490/algae.2010.25.3.141
Author: Won Boo Yeon, Yates Kim K., Fredericq Suzanne, Cho Tae Oh
Organization: Won Boo Yeon; Yates Kim K.; Fredericq Suzanne; Cho Tae Oh
Publish: ALGAE Volume 25, Issue3, p141~153, 01 Sep 2010

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ABSTRACT

Seagrass epiphyte blooms potentially have important economic and ecological consequences in Tampa Bay, one of the Gulf of Mexico’s largest estuaries. As part of a Tampa Bay pilot study to monitor the impact of environmental stresses,precise characterization of epiphyte diversity is required for efficient management of affected resources. Thus, epiphyte diversity may be used as a rational basis for assessment of ecosystem health. In May 2001, epiphytic species encompassing green, brown and red macroalgae were manually collected from dense and sparse seagrass beds of Thalassia testudinum and Syringodium filiforme. A total of 20 macroalgal epiphytes, 2 Chlorophyta, 2 Phaeophyta, and 16 Rhodophyta,were found on T. testudinum and S. filiforme seagrass at the four sampling sites (Bishop Harbor, Cockroach Bay, Feather Sound, and Mariposa Key). The Rhodophyta, represented by 16 species, dominated the numbers of species. Among them, the thin-crusted Hydrolithon farinosum was the most commonly found epiphyte on seagrass leaves. Species number, as well as species frequency of epiphytes, is higher at dense seagrass sites than sparse seagrass sites. Four attachment patterns of epiphytes can be classified according to cortex and rhizoid development: 1) creeping, 2) erect,3) creeping & erect, and 4) erect & holding. The creeping type is characterized by an encrusting thallus without a rhizoid or holdfast base. Characteristics of the erect type include a filamentous thallus with or without a cortex, and a rhizoid or holdfast base. The creeping and erect type is characterized by a filamentous thallus with a cortex and rhizoid. A filamentous thallus with a cortex, holdfast base, and host holding branch is characteristics of the erect and holdfast attachment type. This study characterized each species found on the seagrass for epiphyte identification.
KEYWORD

epiphytes , Florida , seagrass , Syringodium filiforme , Tampa Bay , taxonomy , Thalassia testudinum

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INTRODUCTION

Seagrass meadows are very productive ecosystems of which a large proportion is often attributed to epiphytes(Heijs 1984, Leliaert et al. 2001). Seven seagrass species occur in Florida: Syringodium filiforme, Halodule beaudettei, Halophila johnsonii, Thalassia testudinum, Halophila decipiens, Halophila engelmannii and Ruppia maritima (Virnstein and Cairns 1986, Dawes et al. 1995). Seagrass affects sedimentation by baffling currents with long leaves and providing substrates suitable for diverse epiphytic biota (Land 1970, Almasi et al. 1987, Koch 1999,Hemminga and Duarte 2000). Among these, T. testudinum (Banks ex Konig) and S. filiforme (Kutzing) dominate in the Caribbean Sea and Gulf of Mexico (Eiseman 1980).

Seagrass epiphytes are very important components of the meadows. At least 113 epiphytes and up to 120 macroalgal species have been identified from Florida seagrass blades and communities, respectively (Dawes 1987). Although lists and ecological studies about epiphytes on T. testudinum and S. filiforme have been conducted, studies have not reported detailed characterization of macroalgal epiphytes on these grasses.

This paper characterizes macroalgal epiphytes and determines attachment patterns on seagrass blades of T. testudinum and S. filiforme. This study also compares macroalgal species composition between sites of sparse and dense seagrass beds.

MATERIALS AND METHODS

During the spring of 2002, seagrass shoots of T. testudinum and S. filiforme with epiphytes were collected from different subtidal biotopes at four sites around Tampa Bay, Florida, USA: Bishop Harbor, Cockroach Bay, Feather Sound, and Mariposa Key. To compare dense and sparse sites, seagrass beds were sampled by 50 cm × 50 cm quadrates. All samples were labeled and preserved in a 4% formaldehyde seawater solution for morphological observation. A detailed study of the epiphytes was carried out in the laboratory. Under a stereomicroscope, all epiphytes were separated from the seagrass leaves by gentle scraping. Epiphytes were stained with 1% aqueous aniline blue for anatomical study, characterization of macro-algal epiphytes, and species identification. Twenty-five seagrass leaves were selected and collected from each sparse and dense site. The number of all epiphytes on each blade was counted to compare species

[Table1.] Comparison of epiphyte attachment patterns on Syringodium filiforme and Thalassia testudinum

abundance of epiphytes between sparse and dense sites.

RESULTS AND DISCUSSION

  > Epiphytic species composition, species abundance,and attachment pattern

As shown in Table 1, a total of 20 macroalgal epiphytes (2 Chlorophyta, 2 Phaeophyta, and 16 Rhodophyta) are found in T. testudinum and S. filiforme seagrass beds at the four sampling sites. Of them, four taxa, Acrochaetium, Griffithsia, Gayliella, and Ceramium, are not identified to species level because only single or small sized plants were found. Thus, sample size is insufficient for identification.This is relatively restricted when compared to other similar studies in Florida. Humm (1964) observed 113 species on T. testudinum in South Florida, and Ballantine and Humm (1975) mentioned 66 epiphytes on the 4 seagrass species in Florida. In this study, the number of epiphytes is less than in previous studies because previous research studies were conducted over several seasons.

Rhodophyta exceeds 80% at the total species number. Of them, the thin-crusted Hydrolithon farinosum is the most commonly found epiphyte on seagrass leaves. It is similar to other results that indicate crustose Corallinaceae are the dominant epiphytic species on seagrasses (Heijs 1984, Leliaert et al. 2001). Although the epiphyte species of the genus Spyridia and Hypnea have been reported as drift macroalgae in seagrass systems (Dawes et al. 1985), they are also typical epiphytes on the seagrass in this study.

The total species number of epiphytes on each narrow S. filiforme and wide T. testudinum is similar. However, epiphytic composition differs strongly between T. testudinum and S. filiforme even though they were collected from the same locality. Enteromorpha flexuosa, Sphacelaria rigidula, Griffithsia sp., and Ceramium sp. are found only on S. filiforme seagrass beds, while Cladophora prolifera,Hydrolithon farinosum, Hypnea valentiae, and Heterosiphonia crispella are found only on T. testudinum seagrass beds.

Species number, as well as species frequency, of epiphytes is higher at dense seagrass sites than sparse seagrass sites. Fourteen epiphytes were identified from dense sites of S. filiforme seagrass beds, while 11 were identified from sparse sites. Five species, E. flexuosa, S. rigidula, Gayliella sp, Ceramium sp. Herposiphonia tenella, were collected only from dense sites, while two others, Acrochaetium sp., Griffithsia sp., were only collected from sparse sites. Fifteen epiphytes were identified from dense sites of T. testudinum seagrass beds, while 12 were identified from sparse sites. Four species, C. prolifera, Hypnea musciformis, H. valentiae, H. tenella, were collected from dense sites, while Heterosiphonia crispella was only collected from sparse sites. Since density of seagrass blades causes modifications of physical factors such as water movements, and it increases the possibil-

[Fig.1.] Abundance of epiphytic macroalgae expressed as the total number of individuals found on 25 Thalassia testudinum from each dense and sparse site.

ity of attachment of macroalgal epiphytes to seagrass blades, a larger number of epiphytes may occur in dense sites. Species frequency of epiphytes on each blade of T. testudinum is also larger in dense sites (Fig. 1)

As summarized in Table 1, four attachment patterns of epiphytes can be classified according to development of cortex and rhizoid: 1) creeping, 2) erect, 3) creeping & erect, and 4) erect & holding. The creeping type is characterized by an encrusting thallus without a rhizoid or holdfast base. This type is found in Hydrolithon farinosum. The erect type is characterized by a filamentous thallus with or without a cortex, and a rhizoid or holdfast base. This type is found in E. flexuosa, C. prolifera, Hincksia mitchelliae, S. rigidula, Stylonema alsidii, Hypnea spinella, H. valentiae, Champia parvula, Polysiphonia flaccidissima, H. crispella, Chondria collinsiana, Acrochaetium sp., and Griffithsia sp. The creeping and erect type is characterized by a filamentous thallus with a cortex and rhizoid. This type is found in Centroceras gasparrinii,H. tenella, Gayliella sp., and Ceramium sp. The erect and holdfast type is characterized by a filamentous thallus with a cortex, holdfast base, and host holding branch. This type is found in H. musciformis and Spyr-

idia filamentosa. Epiphytes with erect attachment patterns are common at dense sites, while epiphytes with creeping and erect attachment patterns are common at sparse sites.

  > List and characterization of epiphytes

Although most of these epiphytic species have previously been reported from Florida (Dawes 1987, Littler and Littler 2000), we characterize each species with detailed morphology.

  > Chlorophyta

Enteromorpha flexuosa (Wulfen) J. Agardh 1883 (Fig. 2 & 3)Basionym: Ulva flexuosa Wulfen 1803.

[Fig. 2.] Vegetative thallus.

[Fig. 3] Cross section view. Scale bars represent: Fig. 2 1 mm; Fig. 3 100 ㎛

[Fig. 4.] Vegetative thallus

[Fig. 5.] Upper part of thallus

[Fig. 6.] Dichotomous branching

[Fig. 7.] Trichotomous branching. Scale bars represent: Fig. 4 l mm; Fig. 5 100 μm; Fig. 6 40 μm; Fig. 7 40 μm

[Fig. 8.] Vegetative thallus with tapering apices (arrows).

[Fig. 9] Reproductive thallus

[Fig. 10] Branch with plurilocular sporangia (S). Scale bars represent: Fig. 8 0.5 mm; Fig. 9 100 μm; Fig. 10 40 μm.

[Fig. 11] Vegetative thallus

[Fig. 12.] Slender biradiate propagula (P). Scale bars represent: Fig. 11 0.5 mm; Fig. 12 100 μm.

The thallus is slender, erect, and about 1 cm high. Blades taper toward base and are cylindrical and hollow. Rhizoids form a tightly knit basal pad.

Cladophora prolifera (Roth) Kutzing 1843 (Figs 4-7) Basionym: Conferva prolifera Roth 1797; 182.

The thallus is filamentous, pseudo-dichotomous or pseudo-trichotomous, branching, erect, and about 1 cm high. Filaments are straight to slightly curved. Rhizoids are formed from basal cells.

  > Phaeophyta

Hincksia mitchelliae (Harvey) P. C. Silva in Silva et al. 1987 (Figs 8-10)

Basionym: Ectocarpus mitchelliae Harvey 1852; 142.

The thallus is filamentous tufts or mats, erect, and 0.5 cm high. Filaments are irregularly branched, and taper toward apices. Plurilocular sporangia are cylindrical, rarely stalked, and lateral on filaments.

Sphacelaria rigidula Kutzing 1843 (Fig. 11 & 12)

The thallus is filamentous, erect, and 0.3 cm high. Filaments are straight and cylindrical. Propagules have 2-3 cylindrical arms.

  > Rhodophyta

Stylonema alsidii (Zanardini) Drew 1956 (Fig. 13 & 14) Basionym: Bangia alsidii Zanardini 1839; 136.

The thallus is erect, pseudodichotomously branched, and 0.2-0.3 cm high. Cells are discoid to ellipsoid.

Acrochaetium sp. (Fig. 15-17)

The thallus is filamentous, erect, and 0.3-0.5 cm high. Cells are cylindrical or rod-shaped. Monosporangia are basal in lateral clusters and develop adaxially at the upper part of the cell.

Hydrolithon farinosum (J. V. Lamouroux) Penrose & Y. M. Chamberlain 1993 (Fig. 18-24) Basionym: Melobesia farinose J. V. Lamouroux 1816; 315.

The thallus is prostrate, thin, crusts, develops from an initial four-celled structure, and measures 0.3-0.5 cm diam. Tetrasporangial conceptacles are hemispherical and tetrasporangia are zonately divided.

Hypnea musciformis (Wulfen) J. V. Lamouroux 1813 (Figs 25-29) Basionym: Fucus musciformis Wulfen in Jacquin 1791; 154.

The thallus is tangled, wiry, erect, then coiled, and about 10-15 cm high. Apices are slightly upcurved, flattened hooks. Holdfast is disc-like, becoming more tangled by the coiled apex.

H. spinella (C. Agardh) Kutzing 1847 (Fig. 30-33) Basionym: Sphaerococcus spinellus C. Agardh 1822; 323.

The thallus is wiry, erect, and 5-6 cm. Apices are tapering and pointed, but not upcurved. Branchlets are spine-like and numerous. Holdfast is disc-like.

H. valentiae (Turner) Montagne1841 (Fig. 34-36) Basionym: Fucus valentiae Turner 1808-1809; 17.

The thallus is tough, wiry, erect, and 7-8 cm high. Apices are tapering and pointed, but not upcurved. Branchlets are spine-like and star-shaped with up to six points. Holdfast is disc-like.

Champia parvula (C. Agardh) Harvey 1853 (Fig. 37-50)Basionym: Chondria parvula C. Agardh 1824; 207.

The thallus is gelatinous, alternately branching, erect, and about 3-5 cm high. Branches are cylindrical to slightly flattened. Apices are bluntly pointed. Segments are swollen or barrel-shaped. The inner wall is lined with faint longitudinal filaments with sparsely scattered and oval gland cells. Spermatangia are in swollen spermatangial sori and produced from cortical cells. Cystocarps are protuberant with wide ostioles. Tetrasporangia are spherical, tetrahedrally divided, and produced on the inner side of cortical cell.

Griffithsia sp. (Fig. 51)

The thallus is monosiphonous, dichotomous, erect, and 1 cm high. Sterile filaments are whorled at upper ends of segments and trichotomously branched.

Centroceras gasparrinii (Meneghini) Kutzing 1849 (Figs 52-58)

The thallus is filamentous, dichotomous, creeping and erect, and 2-4 cm high. Apices are incurved. The cortex is complete and has whorled spines. Spermatangia are in the terminal clusters of the node. Tetrasporangia are spherical, produced from periaxial cells, and protected by involucral branchlets. Recently, Won et al. (2009) resurrected this species based on morphological and molecular evidence.

Gayliella sp. (Figs 59 & 60)

The thallus consists of prostrate axes giving rise to erect axes, and is 0.2-0.3 cm high. The axis has four periaxial cells. Three cortical initials are produced per periaxial cell. Of them, basipetal cortical cells are produced horizontally and grow basipetally. This species is similar to Gayliella transversalis (Collins and Hervey) T. O. Cho and Fredericq reported from Key West, Florida by Cho et al. (2008), in that it may be distinguished by branching pattern.

Ceramium sp. (Figs 61 & 62)

The thallus is simple, filamentous, pseudo-dichotomous, creeping and erect, and 0.5 cm high. Cortication is incomplete. Two cortical cells are acropetally produced from a peraxial cell.

Herposiphonia tenella (C. Agardh) Ambronn 1880 (Fig. 63)Basionym: Hutchinsia tenella C. Agardh 1828; 105.

[Fig. 13] Vegetative thallus.

[Fig. 14] Upper part of thallus with branch initials (arrow). Scale bars represent: Fig.13 40 μm; Fig. 14 40 μm.

[Fig. 15] Vegetative thallus

[Fig. 16] Upper part of thallus with monosporangia (arrows).

[Fig. 17.] Lower part of thallus with holdfast. Scale bars represent: Fig. 15 100 μm; Fig. 16 40 μm; Fig. 17 40 μm

[Fig.18] Vegetative thallus.

[Fig. 19] Four celled initials

[Fig. 20] Cross section view of thallus on seagrass

[Fig. 21] Female conceptacle

[Fig. 22] Cross section view of female conceptacle

[Fig. 23.] Tetrasporangial conceptacle

[Fig. 24] Cross section view of tetrasporangial conceptacle having tetrasporangia (T). Scale bars represent: Fig. 18 100 μm; Fig. 19 10 μm; Fig. 20 40 μm; Fig. 21 20 μm; Fig. 22 40 μm; Fig. 23 20 μm; Fig. 24 40 μm.

[Fig. 25] Vegetative thallus

[Fig. 26] Curved apex

[Fig. 27] Coiled apex.

[Fig. 28] Tangled branches (arrow).

[Fig. 29.] Cross section view of thallus. Scale bars represent: Fig. 25 1 mm; Fig. 26 0.5 mm; Fig. 27 0.5 mm; Fig. 28 1 mm; Fig. 29 50 μm.

[Figs 30] Vegetative thallus

[Fig. 31.] Upper part of thallus

[Fig. 32] Spine-like branchlets (arrows) on middle part of thallus

[Fig. 33] Cross section view of thallus. Scale bars represent: Fig. 30 1 mm; Fig. 31 1 mm; Fig. 32 0.5 mm; Fig. 33 50 μm.

[Fig. 34] Vegetative thallus

[Fig. 35.] Stellate branchlets (arrows) on middle part of thallus

[Fig. 36] Cross section view of thallus. Scale bars represent: Fig. 34 1 mm; Fig. 35 0.5 mm; Fig. 36 50 μm.

[Fig. 37.] Vegetative thallus

[Fig. 38.] Surface showing the scattered small cells

[Fig. 39.] Cross section view through node.

[Fig. 40] Cross section view through internode

[Fig. 41] Longitudinal section view of upper thallus

[Fig. 42.] Longitudinal section view of nodal part.

[Fig. 43] Longitudinal section view showing gland cell (arrow head) and longitudinal filaments (arrow).

[Fig. 44.] Male branch with spermatangial sori.

[Fig. 45] Surface of spermatangial sori

[Fig. 46.] Cross section of male branch with spermatangia (S).

[Fig. 47.] Female thallus with cystocarp (C).

[Fig. 48.] Longitudinal section of cystocarp with carpospores

[Fig. 49.] Surface of tetrasporic thallus with tetrasporangia (T).

[Fig. 50.] Cross section of tetrasporic thallus showing tetrasporangium developed from cortical cell. Scale bars represent: Fig. 37 1 mm; Fig. 38 40 μm; Fig. 39 50 μm; Fig. 40 50 μm; Fig. 41 100 μm; Fig. 42 50 μm; Fig. 43 20 μm; Fig. 44 0.5 mm; Fig. 45 40 μm; Fig. 46 40 μm; Fig. 47 100 μm; Fig. 48 100 μm; Fig. 49 100 μm; Fig. 50 20 μm.

[Fig. 51.] Griffithsia sp.

[Fig. 52.] Vegetative thallus.

[Fig. 53] Cross section view through cortical node

[Fig. 54.] Cross section view through internode

[Fig. 55.] Creeping part of lower thallus having rhizoids (R).

[Fig. 56.] Cortical node with spermatangia (S) of male thallus

[Fig. 57.] Tetrasporangial thallus

[Fig. 58.] Tetrasporangia (T) with involucral branches (arrows) in abaxial side. Scale bars represent: Fig. 52 0.5 mm; Fig. 53 20 μm; Fig. 54 20 μm; Fig. 55 100 μm; Fig. 56 40 μm; Fig. 57 0.5 mm; Fig. 58 50 μm.

[Fig. 59] Vegetative thallus

[Fig. 60] Creeping and erect parts of thallus. Scale bars represent: Fig. 59 50 μm; Fig. 60 100 μm.

[Fig. 61.] Vegetative thallus

[Fig. 62.] Cortical nodes. Scale bars represent: Fig. 61 100 μm; Fig. 62 20 μm.

[Fig. 63.] Herposiphonia tenella

[Fig. 64.] Thallus.

[Fig. 65.] Apex with prominent scar cells (arrow).

[Fig. 66] Cross section of thallus

[Fig. 67.] Cystocarp. Scale bars represent: Fig. 64 0.5 mm; Fig. 65 40 μm; Fig. 66 20 μm; Fig. 67 100 μm.

[Fig. 68.] Vegetative thallus.

[Fig. 69.] Surface of axis

[Fig. 70.] Tangled branches (arrow). Scale bars represent: Fig. 68 0.5 mm; Fig. 69 40 μm; Fig. 70 1 mm.

[Fig. 71.] Vegetative thallus

[Fig. 72.] Branchlet. Scale bars represent: Fig. 71 0.5 mm; Fig. 72 100 μm.

The thallus is tangled, prostrate, creeping and erect, and 0.5 cm high. Branching is irregularly alternate. Rhizoids arise from each node.

Polysiphonia flaccidissima Hollenberg 1942 (Figs 64-67)

The thallus is filamentous, erect, and 0.3 cm high. Branching is irregularly alternate with four pericentral cells. Scar cells are common between segments and apical filaments are highly branched. Cystocarps are spherical and on short stalk.

Spyridia filamentosa (Wulfen) Harvey in W. Hooker 1833 (Fig. 68-70) Basionym: Fucus filamentousus Wulfen 1803; 64.

The thallus is filamentous, erect and then coiled, and about 7 cm high. Branchlets are delicate and unbranched, with incomplete cortication.

Heterosiphonia crispella (C. Agardh) M. J. Wynne 1985 (Fig. 71 & 72) Basionym: Callithamnion crispellum C. Agardh 1828; 183.

The thallus is delicate, erect, not corticated, and 0.4 cm high. Branchlets are deciduous, and dichotomously to alternately branched. Our material is at a young plant stage.

Chondria collinsiana M. Howe 1920 (Fig. 73-85)

The thallus is solitary, erect, and 0.8-1.2 cm high. There are 5-6 pericentral cells. Apices are truncate to slightly rounded and tufted with dichotomously branched fila-

[Fig. 73] Vegetative thallus.

[Fig. 74.] Surface view of thallus

[Fig. 75] Apex.

[Fig. 76] Cross section of thallus.

[Fig. 77.] Apical cell (arrow) of branch

[Fig. 78.] Male thallus

[Fig. 79] Male apex with flat disc like spermatangial sorus (arrows).

[Fig. 80.] Spermatangial sorus with spermatangia (S).

[Fig. 81] Female thallus

[Fig. 82.] Young cystocarp (C).

[Fig. 83.] Tetrasporic thallus

[Fig. 84.] Cross section of tetrasporic thallus with tetrasporangia (T).

[Fig. 85.] Tetrasporangium developed from a pericentral cell (P). Scale bars represent: Fig. 73 0.25 mm; Fig. 74 40 μm; Fig. 75 100 μm; Fig. 76 50 μm; Fig. 77 20 μm; Fig. 78 0.5 mm; Fig. 79 100 μm; Fig. 80 100 μm; Fig. 81 40 μm; Fig. 82 100 μm; Fig. 83 0.5 mm; Fig. 84 100 μm; Fig. 85 50 μm.

ments. Tetrasporangia are spherical, tetrahedrally divided, and produced on branchlets. Spermatangial sori are disc-shaped, circular to oval, flat, and form at the base of apical filaments. Cystocarps are on the short stalk and spherical to oval.

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[Table1.] Comparison of epiphyte attachment patterns on Syringodium filiforme and Thalassia testudinum
[Fig.1.] Abundance of epiphytic macroalgae expressed as the total number of individuals found on 25 Thalassia testudinum from each dense and sparse site.
[Fig. 2.] Vegetative thallus.
[Fig. 3] Cross section view. Scale bars represent: Fig. 2 1 mm; Fig. 3 100 ㎛
[Fig. 4.] Vegetative thallus
[Fig. 5.] Upper part of thallus
[Fig. 6.] Dichotomous branching
[Fig. 7.] Trichotomous branching. Scale bars represent: Fig. 4 l mm; Fig. 5 100 μm; Fig. 6 40 μm; Fig. 7 40 μm
[Fig. 8.] Vegetative thallus with tapering apices (arrows).
[Fig. 9] Reproductive thallus
[Fig. 10] Branch with plurilocular sporangia (S). Scale bars represent: Fig. 8 0.5 mm; Fig. 9 100 μm; Fig. 10 40 μm.
[Fig. 11] Vegetative thallus
[Fig. 12.] Slender biradiate propagula (P). Scale bars represent: Fig. 11 0.5 mm; Fig. 12 100 μm.
[Fig. 13] Vegetative thallus.
[Fig. 14] Upper part of thallus with branch initials (arrow). Scale bars represent: Fig.13 40 μm; Fig. 14 40 μm.
[Fig. 15] Vegetative thallus
[Fig. 16] Upper part of thallus with monosporangia (arrows).
[Fig. 17.] Lower part of thallus with holdfast. Scale bars represent: Fig. 15 100 μm; Fig. 16 40 μm; Fig. 17 40 μm
[Fig.18] Vegetative thallus.
[Fig. 19] Four celled initials
[Fig. 20] Cross section view of thallus on seagrass
[Fig. 21] Female conceptacle
[Fig. 22] Cross section view of female conceptacle
[Fig. 23.] Tetrasporangial conceptacle
[Fig. 24] Cross section view of tetrasporangial conceptacle having tetrasporangia (T). Scale bars represent: Fig. 18 100 μm; Fig. 19 10 μm; Fig. 20 40 μm; Fig. 21 20 μm; Fig. 22 40 μm; Fig. 23 20 μm; Fig. 24 40 μm.
[Fig. 25] Vegetative thallus
[Fig. 26] Curved apex
[Fig. 27] Coiled apex.
[Fig. 28] Tangled branches (arrow).
[Fig. 29.] Cross section view of thallus. Scale bars represent: Fig. 25 1 mm; Fig. 26 0.5 mm; Fig. 27 0.5 mm; Fig. 28 1 mm; Fig. 29 50 μm.
[Figs 30] Vegetative thallus
[Fig. 31.] Upper part of thallus
[Fig. 32] Spine-like branchlets (arrows) on middle part of thallus
[Fig. 33] Cross section view of thallus. Scale bars represent: Fig. 30 1 mm; Fig. 31 1 mm; Fig. 32 0.5 mm; Fig. 33 50 μm.
[Fig. 34] Vegetative thallus
[Fig. 35.] Stellate branchlets (arrows) on middle part of thallus
[Fig. 36] Cross section view of thallus. Scale bars represent: Fig. 34 1 mm; Fig. 35 0.5 mm; Fig. 36 50 μm.
[Fig. 37.] Vegetative thallus
[Fig. 38.] Surface showing the scattered small cells
[Fig. 39.] Cross section view through node.
[Fig. 40] Cross section view through internode
[Fig. 41] Longitudinal section view of upper thallus
[Fig. 42.] Longitudinal section view of nodal part.
[Fig. 43] Longitudinal section view showing gland cell (arrow head) and longitudinal filaments (arrow).
[Fig. 44.] Male branch with spermatangial sori.
[Fig. 45] Surface of spermatangial sori
[Fig. 46.] Cross section of male branch with spermatangia (S).
[Fig. 47.] Female thallus with cystocarp (C).
[Fig. 48.] Longitudinal section of cystocarp with carpospores
[Fig. 49.] Surface of tetrasporic thallus with tetrasporangia (T).
[Fig. 50.] Cross section of tetrasporic thallus showing tetrasporangium developed from cortical cell. Scale bars represent: Fig. 37 1 mm; Fig. 38 40 μm; Fig. 39 50 μm; Fig. 40 50 μm; Fig. 41 100 μm; Fig. 42 50 μm; Fig. 43 20 μm; Fig. 44 0.5 mm; Fig. 45 40 μm; Fig. 46 40 μm; Fig. 47 100 μm; Fig. 48 100 μm; Fig. 49 100 μm; Fig. 50 20 μm.
[Fig. 51.] Griffithsia sp.
[Fig. 52.] Vegetative thallus.
[Fig. 53] Cross section view through cortical node
[Fig. 54.] Cross section view through internode
[Fig. 55.] Creeping part of lower thallus having rhizoids (R).
[Fig. 56.] Cortical node with spermatangia (S) of male thallus
[Fig. 57.] Tetrasporangial thallus
[Fig. 58.] Tetrasporangia (T) with involucral branches (arrows) in abaxial side. Scale bars represent: Fig. 52 0.5 mm; Fig. 53 20 μm; Fig. 54 20 μm; Fig. 55 100 μm; Fig. 56 40 μm; Fig. 57 0.5 mm; Fig. 58 50 μm.
[Fig. 59] Vegetative thallus
[Fig. 60] Creeping and erect parts of thallus. Scale bars represent: Fig. 59 50 μm; Fig. 60 100 μm.
[Fig. 61.] Vegetative thallus
[Fig. 62.] Cortical nodes. Scale bars represent: Fig. 61 100 μm; Fig. 62 20 μm.
[Fig. 63.] Herposiphonia tenella
[Fig. 64.] Thallus.
[Fig. 65.] Apex with prominent scar cells (arrow).
[Fig. 66] Cross section of thallus
[Fig. 67.] Cystocarp. Scale bars represent: Fig. 64 0.5 mm; Fig. 65 40 μm; Fig. 66 20 μm; Fig. 67 100 μm.
[Fig. 68.] Vegetative thallus.
[Fig. 69.] Surface of axis
[Fig. 70.] Tangled branches (arrow). Scale bars represent: Fig. 68 0.5 mm; Fig. 69 40 μm; Fig. 70 1 mm.
[Fig. 71.] Vegetative thallus
[Fig. 72.] Branchlet. Scale bars represent: Fig. 71 0.5 mm; Fig. 72 100 μm.
[Fig. 73] Vegetative thallus.
[Fig. 74.] Surface view of thallus
[Fig. 75] Apex.
[Fig. 76] Cross section of thallus.
[Fig. 77.] Apical cell (arrow) of branch
[Fig. 78.] Male thallus
[Fig. 79] Male apex with flat disc like spermatangial sorus (arrows).
[Fig. 80.] Spermatangial sorus with spermatangia (S).
[Fig. 81] Female thallus
[Fig. 82.] Young cystocarp (C).
[Fig. 83.] Tetrasporic thallus
[Fig. 84.] Cross section of tetrasporic thallus with tetrasporangia (T).
[Fig. 85.] Tetrasporangium developed from a pericentral cell (P). Scale bars represent: Fig. 73 0.25 mm; Fig. 74 40 μm; Fig. 75 100 μm; Fig. 76 50 μm; Fig. 77 20 μm; Fig. 78 0.5 mm; Fig. 79 100 μm; Fig. 80 100 μm; Fig. 81 40 μm; Fig. 82 100 μm; Fig. 83 0.5 mm; Fig. 84 100 μm; Fig. 85 50 μm.