Lab II. Morphology and Ecology

Home , Marine botany, Pneumatocyst, Thallus

Objective To identify algae, you will need to know some phycological terms. There are several ways to describe algae: (a) morphologically, using external and internal characteristics, and (b) ecologically, by distribution and habitat. The following lab exercises will introduce you to external and internal algal morphology. As a reference for the field, ecology and distribution terms for algae are included at the end of this section. These terms will aid in identification of algae, as well as in understanding their morphological features.

Notebook Requirement- 11 drawings 1) 2 thallus forms (not branching) 2) 2 branching forms 3) 2 holfast type 4) 1 pneumatocyst type 5) Pterosiphonia (draw thallus under dissecting scope) 6) Apical cell 7) 2 Unknowns (draw & steps to key)

A) External Morphology Terms (macroscopic) A thallus is a term for the mass of cellular tissue forming a plant body without true stems, roots, leaves, or vascular system. A variety of terms used to describe thallus morphology follo ws, with species examples. 1) Thallus Forms Articulated/Geniculate Calcified segments connected by uncalcified joints. (Corallina) Bladed Flattened leaf-like thallus or thallus part, may have a stipe. (Laminaria) Branching Alga with axillary divisions. (Ptilota) Catenate arranged in single series (Stephanocystis) Crustose Grows flat along the substrate; crust-like. (Ralfsia, Non-geniculate corallines) Bl a d e Filamentous Thread or hair-like, having a single row of cells. (Cladophora, Chaetomorpha) Foliose A sheet of cells; blade-like, no stipe. St i pe monostromatic One cell thick. (Porphyra, Monostroma) distromatic Two cells thick. (Ulva) polystromatic Many cells thick. (Mazzaella) Ho l d f a s t Prostrate/procumbent Trailing on the ground; procumbent. (Codium setchellii) Saccate Sac-like. (Halosaccion) Single cell Microalgae. (diatom, cyanobacterium, Porphyridium) Stipitate Having a stipe—a thick, stem-like structure bearing other structures like blades (Laminaria) Stoloniferous Proliferating by vegetative branches that creep along the substrate and establish new plants. (Laminaria sinclairii) Tubular Thallus made up of a tube of cells, hollow in center. (Scytosiphon) Upright In an erect position or posture; vertical or nearly so; pointing upward (Gastroclonium)

Macrocystis integrifolia demonstrates stoloniferous growth. (Now M. pyrifera, intertidal growth form demonstrates phenotypic plasticity in response to sand) 2) Branching Forms As well as being a useful tool for identification, branching form indicates the growth habit and meristem type of an alga. Here are the main branching forms you’ll encounter.

Simple Pectinate Distichous Or Pinnate Dichotomous Monopodial Sympodial Whorled Percurrent Microcladia Neorh odom ela, Cumagloia Plocamium Bryops is Fucus Gelidium Ceramium borealis Odonthalia

Dichotomous/Bifurcate Branching by forking in pairs. May be equally or irregularly dichotomous. (Fucus, Silvetia) Distichous Branching on both sides of an axis, may be irregular.

opposite Branches oppose each other on the main axis. alternate Branches alternate on the main axis.

Irregular No detectable branching pattern. (Chondracanthus canaliculata, Mastocarpus) Monopodial Having a distinct main axis of continual growth and giving off branches. (Microcladia, Neorhodomela) Pectinate/Secund Having unilateral branching on one side of the axis, like the teeth of a comb. The side branches may be equal or unequal in length. (Plocamium violacea, Microcladia borealis, apical tip of Macrocystis pyrifera)

Macrocystis pyrifera apical tip Plocamium violacea Examples of pectinate branching.

Percurrent Extending through entire length of structure, usually said of a persistant axis. Pinnate Feather-like, regular branching, with distichous laterals on a central axis

opposite Branches oppose each other on the main axis. alternate Branches alternate on the main axis.

Reticulate Net-like. (Hydroclathrus) Simple Unbranched, undivided thallus or blade. (Ulva, Laminaria) Sympodial Developing so that the apparent main axis does not extend by continuous terminal growth, the former axis usually diverging and ending as a secondary branch. (Ceramium) Verticillate/Whorled Radial branches attached at a common level on the main axis, or branches spiraling off the main axis. (Neorhodomela, Rhodomela, Odonthalia)

from Seashore Plants of California

3) Holdfast Characteristics A holdfast is a structure by which an alga attaches to the substratum. Some algae may be free- floating, and therefore have no distinct holdfast. Basal disk Disk at base of plant attaches to substrate. (Fucales) Discoid Disc-shaped. Haptera The network formed by multiple hapteron clasping the substrate (often rock). Hapteron A single branch within a holdfast, singular of haptera. (Laminaria setchelii)

Haptera }(plural) Hapteron (singular)

Simple modified basal cell One cell attaches to substrate. (Chaetomorpha, Codium) Stolon/Rhizome Creeping vegetative branch occurring at holdfast, giving rise to new plants. (Laminaria sinclairii)

B) Internal Morphology Terms (Microscopic) Anticlinal Pattern of cell division perpendicular to surface of plant. Apical cell(s) Cell(s) at apex of alga, often the site of cell division. May be acute/sharp (Pikea, below); blunt (Gelidium); sunken apical pit (Osmundea, Fucus); obscured by terminal branchlets or trichoblasts (Polysiphonia); conspicuous (Sphacelaria).

Pikea apical cells. UCSC Marine Botany Course.

Coenocytic/Siphonous Plant with multinucleate cell; few or no cross walls. (Codium, Bryopsis) Cortex Pigmented outer layer of cells in cross section. Corticated Having a cortex. Sometimes used to describe the elaboration of the polysiphonous

4 condition; continued proliferation of pericentral cells (Osmundea, Odonthalia, Polysiphonia, Ceramium) Distromatic Sheet of cells is two layers thick. (Ulva) Epidermis Outer layer of cells on some plants. (Laminaria) Filamentous growth Thread-like. (Chaetomorpha—uniseriate, Bangia—multiseriate) Medulla Nonpigmented cells internal to cortex, often of varying size and shape. Midrib The thickened longitudinal axis of flattened branch or blade (Fucus) Midvein A delicate median line of cells, the blade thicker though this region then on either side (Delesseria) Monostromatic Sheet of cells is one layer thick. (Porphyra, Enteromorpha) Multiaxial Thallus has several longitudinal medullary filaments, each derived from an apical cell. (Plocamium) Multiseriate Consisting of several rows of cells in longitudinal series in one or two planes. Parenchymatous 3-dimensional cell division, forming a thallus of adjacent cells with a common origin. In reds, most of the subclass Bangiophycidae are parenchymatous. (Porphyra, below)

Porphyra is parenchymatous. Image courtesy Christina Delgado, UCSC Marine Botany Course.

Periclinal Cell division parallel to surface of plant. Polysiphonous Composed of tiers of vertically elongated cells; lateral pericentral cells surround a central axis. Unique to red algae. (Polysiphonia, Ceramium) Polystromatic Sheet of cells many layers thick. (Mazzaella) Pseudoparenchymatous Thallus formed from filaments that have a common origin, may be a tangle of filaments. In red algae, the Subclass Florideophycidae is pseudoparenchymatous. (Cryptopleura, Nemalion, Gelidium)

Pseudoparenchymatous mass of filaments in Mazzaella. Image courtesy Emily Loufek, UCSC Marine Botany Course.

Uniaxial Thallus has one longitudinal central filament forming the axis. (Endocladia muricata)

Endocladia muricata is uniaxial. Image courtesy Christina Delgado, UCSC Marine Botany Course.

Uniseriate Cells occurring in a single row.

Anatomy of Algae and Plants Because most students learn about land plants before studying algae, they may find it useful to compare anatomical features of the two groups.

Typically, photosynthesis in land plants occurs in leaves or stems in the chloroplast-laden mesophyll layer under the epidermis (see image below). In a stem, the outer cells of the plant are structurally supported by an inner cortex, which is vascularized to transport water and nutrients around the plant.

Algae have a meristoderm layer similar to land plant epidermis, but the algal meristoderm is photosynthetic. A thick layer of cortex gives support to the meristoderm, but there is little or no vascularization of the algal cortex. Towards the center of the algal stipe or leaf lie cells or filaments called the medulla (see photo and illustrations below).

Land plant leaf showing epidermis and mesophyll layers. From James D. Mauseth, Plant Anatomy.

Sarcodiotheca gaudichaudii cross section. Courtesy Julia Bell.

Internal cellular structure for two red algae. a. Sarcodiotheca gaudichaudii (3 mm); b. Rhodymenia sp. (0.5 mm); C = cortex, IM = inner medulla, OM = outer medulla, M = medulla. From Seashore Plants of California, by E. Yale Dawson and Michael S. Foster.

C) Biogeographic Distribution Boreal Growing in northern, colder waters. Cosmopolitan Found in many parts of the world. Tropical Growing in near-equatorial, warmer waters. Temperate Growing in regions between either tropic and its corresponding polar circle, in moderate temperatures.

D) Tidal Distribution Intertidal/Littoral Lying between high and low tide levels, exposed at low tide. In the Monterey area, between about +4.5 feet (1.4 m) and -1.5 feet (0.5 m). Subtidal/Sublittoral Below the lowest low-tide level. E) Substrate Habitat Benthic Attached to substratum, not planktonic. Endophytic Living on and deriving nourishment from another plant. Epiphytic Growing on surface of another plant, usually not parasitic. Hypolithic Living on lower surface of rocks. Neritic Living in coastal ocean waters. Pelagic Living in the open ocean. Parasitic Living on or in another plant and harming it by using its metabolites. Planktonic Drifting, unattached. Psammiphytic Living on sand. Saxicolous/Epilithic Living on rock.