Guido Bressan

Phytoceanographical observations on coralline algae (Corallinales) in the Mediterranean sea

Tabulations (species X bioceanographical areas) of the coralline algae were drawn up based on an analysis of specific literature (more than 250 entries) from all bioceanographical areas of the Mediterranean Sea; direct collection by means of scuba diving and specimen exchanges. 52 species of Corallinales occur in this area. The phytoceanographical distribution of coralline algae in the Mediterranean Sea is not uniform as it is possible to identify areas rich in different species and species which are widespread to a greater or lesser extent in the area considered. During this work it was noted that Mediterranean species at high bioceanographical specificity were present. Some species are of high bioceanographical value because they are characteristic only to some of these areas, as:Titanoderma byssoides f. byssoides,Lithophyllum trochanter (sensu H. Huvé) andTenarea tortuosa. Moreover, there are also characteristic transition areas such as: the Alboran Sea, the South Adriatic Sea and the southern part of the East Mediterranean. Excluding the presence of Atlantic species which are the most abundant, from a chorological point of view it can be noted that the number of Cosmopolitan species varies little while the number of Mediterranean species is higher in all the western sectors of the Mediterranean Sea.RiassuntoUn’analisi di letteratura specialistica (più di 250 pubblicazioni) raccolta da tutte le aree bioceanografiche del Mediterraneo, il campionamento diretto in immersione con ARA e alcuni scambi di erbari hanno permesso di redigere una tavola sinottica (specie X aree bioceanograriche) della distribuzione nel Mar Mediterraneo di 52 specie di Corallinales. Si nota che tale distribuzione non è omogenea, poiché si possono individuarc sia aree a diversa ricchezza specifica, che specie più o meno comuni alle aree considerate. Alcune di queste specie sono ad alto valore bioceanografico perché peculiari solo di alcune di queste aree, come ad es.:Titanoderma byssoides f. byssoides, Lithophyllum trochanter (sensu fi. Huvé) eTenarea tortuosa. Ma ci sono anche aree di transizione caratteristiche quali: il Mare d’Alboran, l’Adriatico méridionale e il Mediterraneo orientale settore méridionale. Escludendo le specie Atlantiche, che sono le più abbondanti, si puo notare, da un punto di vista corologico, che il numero di specie Cosmopolite varia poco mentre il numéro di specie Méditerranée è maggiore in tutti i settori del Mediterraneo occidentale.

Inventario delle Corallinales del Mar Mediterraneo: considerazioni tassonomiche

Abstract Inventory of Corallinales of the Mediterranean Sea: taxonomic aspects. - The aim of the present work is the drawing up of a critical inventory of Corallinales of the Mediterranean Sea. This research has been based upon a census of 320 works published since 175 years, upon direct collections and sample exchanges. A census of 88 species of Corallinales (with forms and varieties), made up on the basis of about 5000 records, has been taken. 34 of the 88 species are considered “species dubiae aut rariter inventae”, it has been reported also “species inquirendae” and “species addendae”. From this census it results that there are some taxonomic problems about genera attributions (Lithophyllum, Pseudolithophyllum, Titanoderma, Neogoniolithon, Spongites, Goniolithion, Leptophytum), species attributions of articulated Corallinales (Corallina elongata, C. officinalis e Haliptilon squamatum) and non-articulated Corallinales (Fosliella ischitana, Lithophyllum (Titanoderma) trochanter, Spongites fruticulosus)....

Seasonal Variations of Cystoseira barbata (Stackhouse) C. Agardh Frond Architecture

The practical assessment of the biogenic structural complexity poses some problems in non-symmetrical or three-dimensional macroalgae. This study represents the first attempt to measure quantitatively the phenology and the plasticity of Cystoseira barbata (Stackhouse) C. Agardh in the Mediterranean Sea. This canopy-forming brown alga is characterised by a ramified monopodial cauloid and a dendroid frond. To analyse the morphological-spatial changes in time and the plasticity of C. barbata an experiment was conducted in a protected sea area of the Northern Adriatic Sea on thalli taken from a natural population and a transplanted one, re-located in deeper water. The three-dimensional complexity of thalli and the frond architecture were analysed by means of quantitative structural (total area, perimeter) and spatial (intercepting area, volume and interstitial area) attributes. A preliminary assessment of the primary production of the basiphyite-epiphyte system was investigated by a volumetric analysis. The thalli showed a seasonal pattern characterised by a marked phenological variation of the fronds, both in size and in shape. The seasonal trend was comparable in the both populations studied, with fronds largest in spring–summer, whereas the fall of phylloids and branchelets occurs in autumn–winter. Also the abundance of algal epibionts on the host varied seasonably and depended mainly on the life-form of Cystoseira fronds, where complex fronds encouraged more abundant associated epibionts. The morphological variability of different individuals was also investigated using some bio-structural indices. These indices were proposed as useful for a more detailed description of the phenology of C. barbata and for a better evaluation of the potential micro-spatial and structural habitat available inside the fronds. The proposed protocol and the quantitative descriptors analysed may be employed in physiological or ecological studies, being useful for a standardisable classification of a habitat’s complexity. The analysed spatial and structural attributes, as well as the definition of the complexity of C. barbata, enable the evaluation of the area available for the attachment and shelter of epibionts together with the number and type of potential habitats.

Affinità floristica dei tipi di vegetazione bentonica della Cala di Mitigliano (Massa Lubrense, Napoli)

Abstract Floristic affinity of bentonic vegetational types of Cala di Mitigliano (Massa Lubrense Napoli). — We have studied the bentonic plants community in the Cala di Mitigliano. It appears that some species compositions repeat themselves with a certain regularity. This fact lets us recognize and consequently classify them. In Cala di Mitigliano we took an interest and considered only such species compositions. We calculated, in them and between them, the coefficient of affinity by SORENSEN (1948). The cluster analysis by average linkage and the use of an index of «individualisation» (Feoli, ined.) based on floristic comparison showed that the species compositions, although we chose such ones to describe the vegetation, equally change gradually from place to place.

Ricerche sul genere Fosliella (Corallinaceae - Rhodophyta): Fosliella cruciata sp. nov.

Abstract Research on genus Fosliella (Corallinaceae - Rhodophyta): Fosliella cruciata sp. nov.—The present paper deals with various populations algae of genus Fosliella belonging to the living in the Gulf of Trieste. Systematic investigations have been carried out to compare these populations with already known species of the same genus. The population studied belonging to a new species, Fosliella cruciata. Which differs above all in growth of germinative disk, and shape of tricocytes and of tectal cells.

‘Periphyton’ Colonization: Principles, Criteria and Study Methods

When submerged in sea water, all objects, whether artificial or natural, are soon covered by fouling. Some workers consider sediment and silt deposited on substrata to be‘fouling’and use the term‘biofouling’for animal and plant aggregates. In terms of a biocenosis biofouling cannot be defined as a distinctive biological entity since it varies in accordance with a multitude of environmental factors (Relini, 1977).

Osservazioni sugli stadi iniziali della morfogenesi in coltura di alcune specie del genere Peyssonnelia Decaisne

Abstract Researches on the morphogenesis of the genus Peyssonnelia Decaisne. — This paper reports the first result on morphogenetic researches in cultures of 3 species of the genus Peyssonnelia Decne. The development of Peyssonnelia rubra (Grev.) J. Ag. is of «Dumontia type »(CHEMIN, 1937) that one of Peyssonnelia squamaria (Gmelin) Decne. and of Peyssonnelia inamoena Pilger of «Naccaria type». According to our cultures results the morphogenesis of genus Peyssonnelia is of two type. Sample of P. squamaria and P. inamoena are collected in the gulf of Trieste (Nord Adriatic Sea) those of P. cfr. rubra in the Morlaix Bay (English Channel). Taxonomic value of the results are discussed.

Helminthocladia hudsonii (C. Ag.) J. Ag.: prima segnalazione per il Mediterraneo

Abstract Helminthocladia hudsonii (C. Ag.) J. Ag. new for the Mediterranean Sea. – In this paper the genus Helminthocladia (Florideae, Nemalionales) is for the first time recorded for the Mediterranean Sea. H. hudsonii was collected in the Straits of Messina near Villa S. Giovanni (Italy) at 3 mts depth (5 august 1970). Data on the habitat, geographic distribution, structure and reproduction of this species are reported.

Chorological observations on endemic Mediterranean coralline algae: Climatic influences

Differing distribution patterns of red surface coralline algae in the Mediterranean Sea would seem to imply an accentuated reactivity of these species to different ecological factors. This work sets out to determine whether the distribution of Mediterranean coralline algae may possibly be related with average surface seawater temperature. The Endemicity ratio, which expresses the different proportions of Cosmopolitan species (Cos) to Mediterranean species (Med), has been calculated. The study of changes in the Endemicity ratio (0.38 ≤Er ≤ 0.80) has highlighted a gradient between this ratio and the bioceanographical areas considered. By using correspondence analysis (AOC), it has been noted that there is:a) a greater concentration of Mediterranean species which seems to characterize the North West, South West, Middle West and South East Mediterranean areas;b) a greater concentration of Cosmopolitan and Atlantic species which seems to characterize the North, Middle and South Adriatic. On the basis of this investigation it seems that climatic conditions (temperature in particular) has tostered the progressive isolation and speciation development that has led to the endemicity of current Mediterranean Corallinales.RiassuntoLa diversa distribuzione di Corallinales superficiali del Mar Mediterraneo sembra mostrare un’accenruata reattività di queste specie all’iniluenza di diversi fattori ecologici. Scopo di questo lavoro è di determinare 1e relazioni che 1a distribuzione delle Corallinales mediterranee puo avere con 1a temperatiira media superficiale del mare. E stato calcolato il rapporto di Endemicità quale espressione di prevalenza delle specie Cosmopolite (Cos) sulle specie Mediterranee (Med). Lo studio delle variazioni di questo rapporto (0.38 ≤ Er ≤ 0.80), ha permesso di evidenziare un gradiente tra il rapporto stesso e le aree bioceanografiche considerate. L’uso dell’analisi delle corrispondenze (AOC) ha reso possibile l’individuazione di:a) un area di maggior concentrazione di specie Mediterranee, che sembra caratterizzare i settori occidentale i scttentrionale, centrale e méridionale) e orientale méridionale del Mediterraneo;b) un’area di maggior concentrazione di specie Cosmopolite cd Atlantiche che sembra caratterizzare il mare Adriatico (settentrionale, centrale e meridionale). Sulla base di queste ricerche sembra che 1e condizioni climatiche - la tempe-ratura in particolare - abbiano indotto il progressivo isolamento e speciazione, che stanno alla base délia Endemicità rilevata.

La polarité cellulaire dans la progénèse des Fosliella (Corallinacées)

Abstract Cellular polarity of the progenesis of Fosliella (Corallinaceae). – In this work, the author describes the initial phases of the development in culture of the spores of Fosliella (Corallinaceae). A synoptical table concerning the morphological variations of the Dumontia-type germination (Chemin, 1937) in different species of Corallinaceae (Fosliella included) is presented here. A further division of the Dumontia-type development into concentric, parallel and perpendicular types (including in the last one the modes described by Cabioch, 1972) is suggested here. The author gives a definition, progenesis, describing the phase preceding the morphogenesis.