Croissance et capacité reproductive d’<i>Hypnea musciformis</i> (Rhodophyceae, Gigartinale) de la côte atlantique marocaine

Abstract

Growth and reproductuive capacity of Hypnea musciformis (Rhodophyceae, Gigartinale) on the Moroccan Atlantic coast Carrageenan producing seaweeds represent an important biomass along the Atlantic coast of Morocco and are exported as raw material without any local transformation, while agar industry is well developed in the country. The aim of the present work is the valorisation of the more abundant seaweeds and their local transformation. Hypnea musciformis is one of the species studied in the laboratory and a potential applicant for exploitation. The first step before exploitation is to gather information about the biology and growth of this species in natural environment or under controlled conditions in the laboratory. The seasonal growth and reproductive ability of this species have been studied during 2 years on two different locations of Moroccan Atlantic coast. The species was fertile almost all along the year and tetrasporophyte phase predominated. H. musciformis has 2 periods of active growth: the first one at the beginning of summer and the second one, less active, in autumn. The biological cycle is under the influence of different environmental factors as light, temperature, salinity position of the thallus on the seashore and acclimatization response of the seaweed to different habitats.

Reproductive morphology and phenological aspects of one morphological variant of Hypnea pseudomusciformis (Gigartinales, Rhodophyta)

“…Female and male gametophytes of the "nigrescens" variant were frequently found throughout the sampling period. This observation contradicts those of most previous studies of the "musciformis" variant in Brazil (Schenkman 1989;Wallner et al 1992;Reis & Yoneshigue-Valentin 2000;Caires et al 2013b), and those of other Hypnea species throughout the world (Rao 1977;Rangaiah & Rao 1983;Kong & Ang Jr. 2004;Mouradi et al 2008), in which gametophytes were reported to be rare or absent. Already the vegetative fronds were found only in August 2013, despite representing a considerable proportion (~20 %) of the total biomass collected during this month.…”

“…Regarding the reproductive phenology of the "nigrescens" population studied herein, the highest proportion of the total biomass was observed to be made up by tetrasporophytes, followed by female and male gametophytes, and then by vegetative fronds. According to Cecere et al (2000), the dominance of populations by the tetrasporophyte appears to be very common in red algae, and this was also previously reported in natural populations of Hypnea species (Rangaiah & Rao 1983;Schenkman 1989;Wallner et al 1992;Faccini & Berchez 2000;Reis & Yoneshigue-Valentin 2000;Kong & Ang Jr. 2004;Mouradi et al 2008;Caires et al 2013b). Two main hypotheses can explain the predominant occurrence of the tetrasporophytic phase in Hypnea populations: (1) tetrasporophytes may produce more upright thalli per plant and are thus more robust under stressful conditions (Mathieson 1989); or (2) populations maintain themselves mainly by vegetative reproduction (Schenkman 1989).…”

“…Espinoza-Avalos (2005) defined the phenology of macroalgae as the timing of recurring biological events, as well as the underlying causes of their timing by abiotic and biotic factors. Several studies have been conducted to describe the phenology and reproductive biology of Hypnea species (Mshigeni 1976a;b;c;Rao 1977;Rangaiah & Rao 1983;Schenkman 1989;Wallner et al 1992;Reis & Yoneshigue-Valentin 2000;Reis et al 2008;Smith et al 2002;Kong & Ang Jr. 2004;Mouradi et al 2008;Shameel et al 2012;Caires et al 2013b), and most have claimed that their phenology is strongly influenced by environmental factors. At the same time, Forrest & Miller-Rushing (2010) drew attention to the fact that phenology is an important adaptive trait resulting from a complex interplay among an organism's genes and several external environmental factors.…”

The effect of physicochemical parameters and nutrients on the bioecology of Chondracanthus acicularis (Roth) Fredericq at three sites in the Moroccan Atlantic Ocean

“…Furthermore, knowledge of the fertility period will allow establishing a management plan to conserve the species. limited to harvesting and raw material (Mouradi et al, 2008).The carrageenan industry has not experienced a development such as that of the agarophyte algae industry, which represents the leading industrial activity placing Morocco among the world's important producers (El Mtili et al, 2013;Hanif et al, 2014).The main commercial species are Chondracanthus acicularis (C. acicularis) (Roth) Fredericq 1993, Chondracanthus teedei (C. teedii) (Mertens ex Roth) Kützing 1843 and Gigartinapis tillata (G. pistillata) (S.G. G melin) Stackhouse1809, due to the highest carrageenan yields (Pereira, 2013). These three species are characterized by different morphological aspects and can live in the same biotope; however, they are harvested or picked up without distinguishing them from one to another (Guiry, 1984a).Chondracanthus species are characterized by having multiaxial erect thalli emerging from a discoid crustose holdfast, and growth by means of apical or marginal meristems (Bulboa Contador et al, 2020).…”