Cesira Perrone

The prostrate system of the Gelidiales: diagnostic and taxonomic importance

Abstract Despite numerous recent studies on the Gelidiales, most taxa belonging to this order are still difficult to distinguish when in the vegetative or tetrasporic state. This paper describes in detail the morphological and ontogenetic features of the prostrate system of the order with the aim of validating its diagnostic and taxonomic significance. Observations were made on fresh, liquid preserved and cultured thalli. The morphology of the attachment system and the characteristics of rhizoid ontogeny have proven to be useful diagnostic and taxonomic characters. Species belonging to Gelidium, Pterocladia and Pterocladiella bear true attachment organs consisting of cells of both exogenous and endogenous origin. In the family Gelidiellaceae, in contrast, attachment to the substratum is effected by single independent exogenous rhizoids. The attachment rhizoids of the Gelidiales, both exogenous and endogenous, are of the same cell type, and are the so-called hyphae, historically considered typical of the family Gelidiaceae only. A new subdivision of the Gelidiales into three families is proposed here, with the amendment of both Gelidiellaceae and Gelidiaceae, and the Pterocladiaceae fam. nov.

TWO SOLIERIACEAN ALGAE NEW TO THE MEDITERRANEAN: AGARDHIELLA SUBULATA AND SOLIERIA FILIFORMIS (RHODOPHYTA, GIGARTINALES)1

Two Atlantic species found in the Mediterranean Sea were ascribed to the family Solieriaceae on the basis of morphological features. In the extensive drifting beds of the Mar Piccolo basin (Taranto, Ionian Sea), Agardhiella subulata (C. Agardh) Kraft et Wynne and Solieria filiformis (Kützing) Gabrielson were the dominant species in summer. There were no attached populations, and perennation was ensured only by vegetative propagation. Characteristics of the outer cortex and chromatophores were useful for distinguishing the taxa at the species level and are recommended for recognition of sterile specimens.

Parviphycus albertanoae sp. nov. (Gelidiales, Rhodophyta) from the Mediterranean Sea

Abstract: Parviphycus albertanoae sp. nov. was described from the southern Adriatic Sea, Italy on the basis of morphological and molecular data. The new species formed dense tufts at the upper intertidal level on rocky substrata, exposed to intense wave action. Distinctive morphological characters were compressed upright axes closely arising from short stolons, numerous first-order branches and clavate tetrasporangial sori at main and lateral apices. Phylogenetic analysis of mitochondrial cox1 and plastid rbcL sequence data revealed that P. albertanoae was clearly separated from the congeners of the genus, corroborating the morphological distinctness.

How the unattached form of Acanthophora nayadiformis (Rhodophyta : Ceramiales) produces storage and perennating organs

In the Mar Piccolo of Taranto (southern Italy, Mediterranean Sea), an enclosed basin with lagoonal features, Acanthophora nayadiformis is one of the major components of the free-living seaweed community to which the related attached population does not contribute consistently. Loose thalli of A. nayadiformis exhibit morphological features very different from those of the attached specimens and possess a peculiar vegetative cycle including an overwintering phase. Free-living morphs are characterized by monopodial stoloniferous growth; in contrast, both determinate and indeterminate branching as well as the typical ramisympodial growth pattern of the species are lacking. In autumn, free-living thalli fragment giving rise to stolon pieces which undergo deep structural changes in their sub-apical parts including both storage of floridean starch and extensive cortical thickening. Soon afterwards the uncorticated parts decay, whilst the modified fragments are able to overwinter and give rise to new fronds during next spring.

Growth pattern assessment in the genus Acanthophora (Rhodophyta, Ceramiales)

C. Perrone, E. Cecere and G. Furnari. 2006. Growth pattern assessment in the genus Acanthophora (Rhodophyta, Ceramiales).Phycologia 45: 37–43. DOI: 10.2216/04-45.1 The results of a morphological study, mainly based on the growth pattern and shape of both apical zone and branch primordia of all the terete species of Acanthophora, are presented here. This study shows that species are mainly distinguished on the basis of developmental features such as monopodial vs sympodial growth pattern and not by characters such as the presence or absence of spines on the main axes and the morphology of the stichidial ramuli previously generally used to distinguish the species of this genus, and which have proved to be of no diagnostic value. A key to the species of Acanthophora based on both the results of the present research and easily detectable characters is also proposed.

Morphology of Acanthophora nayadiformis (Ceramiales, Rhodophyta)

Abstract Acanthophora nayadiformis is a perennial species of red alga that overwinters by means of a rhizomatous prostrate system; both reproductive and vegetative plants are also able to spread by means of specialized vegetative propagules that have never been reported in other Acanthophora species. A detailed study of thallus morphology has highlighted four kinds of primordia in this species, distinct in shape, size and origin, that develop into as many different types of branches. Thallus growth is at first monopodial, shifting to ramisympodial in most plants. Even the morphological variation observed among tetrasporiferous branches is caused by the type and development of their parent primordia, which confirms the extreme inadequacy of this feature for taxonomic or diagnostic use at species level.

Sulla formazione di galle nella rigenerazione di Pterocladia capillacea (Gmel.) Born. et Thur. in coltura

Abstract Galls and regeneration in P. capillacea. – Galls arose from some cultured segments of Pterocladia capillacea in winter trough regeneration from cut-surfaces, especially at the proximal end. Bacteria were always present on the thallus and inside the old galls. They might be the agents of cecidogenesis, even though we never obtained galls in segments treated with these agents. We suggest that gall formation can be induced by bacteria only in winter, when the stimulus of natural differentiation appears to be very low.

Note ecologiche su Petroglossum nicaeense (Duby) Schotter (Phyllophoraceae)

Abstract Ecological researches on Petroglossum nicaeense. — Some environmental variables of the biotope where P. nicaeense grows are described; that is a superficial cave of the coastline of Bari (Adriatic). The distribution of this species in the Mediterranean is outlined and a classification of this alga on the basis of the criterion of the biological types is tried.

Germinazione «In Vitro» di Carpospore di Petroglossum Nicaeense (Duby) Schotter

Abstract In vitro development of carpospores of Petroglossum nicaeense (Duby) Schotter. This paper describes the germination of carpospores of P. nicaeense (Phyllophoraceae) and the development on glass of new tetrasporophytes to the size of 3–4 mm. Different patterns of development are observed: 1) formation of one or two rizoidal filaments which give rise to an adhesive disc; 2) formation of a morula, of limited growth, and of rizoidal filaments which then originate adhesive discs; 3) formation of a morula which originates a single frond, and formation of filaments that do not form adhesive discs. Eventually, the discs give rise to one or more outgrowths that develop into erect fronds. These fronds reach a 4 mm length 3 months after germination.

Developmental morphology of Acanthophora nayadiformis (Rhodophyta, Ceramiales): Sympodial growth and propagule germination

Abstract The A. nayadiformis thallus is peculiar due both to its morphological organization and to the production of specialized vegetative propagules resembling turions of aquatic dicotyledons. Propagules have proved to be useful culture inocula for morphogenetic research. They germinate quickly when cultured under optimal conditions, growing in a polar fashion, producing uprights from their distal buds and axes with rhizoids from the proximal ones. The thallus growth pattern in A. nayadiformis at first involves a monopodial arrangement of determinate branches followed by ramisympodial growth at all thallus levels with an unpredictable model. There is not, in fact, a fixed ‘sympodial unit’ which reiterates itself in the ramisympodia, thus giving rise to great morphological diversity. Both irradiance and temperature have a significant effect on propagule bud growth rate, but not on their developmental morphology. In contrast, changes in the apex morphogenetic trend, such as transformation from the stolon apex into the upright kind and sympodial growth, are promoted by long-day conditions and largely suppressed under short-day regimes. The short-day inhibition of upright growth seems to be a specialized mechanism for over-wintering in a resistant vegetative phase.