The time course of carpogonial branch and carposporophyte development in Callithamnion cordatum (Rhodophyta, Ceramiales)

Morphological and molecular studies demonstrate that the tribe Ptiloteae (Ceramiaceae, Ceramiales) is polyphyletic. The Ptiloteae, sensu stricto, occur only in the Northern Hemisphere and all Southern Hemisphere representatives belong in other tribes. Three genera (Euptilota, Seirospora, and Sciurothamnion) are transferred to the Euptiloteae Hommersand et Fredericq, trib. nov., and the Callithamnieae is revised to include three Ptilota‐like genera, Georgiella, Falklandiella, and Diapse, and two new genera. Heteroptilon Hommersand, gen. nov. is erected to receive Euptilota pappeana Kützing 1849 and Aglaothamnion rigidulum De Clerck, Bolton, Anderson et Coppejans 2004 from South Africa, and Aristoptilon Hommersand et W. A. Nelson, gen. nov. is established to receive Euptilota mooreana Lindauer 1949 from New Zealand. The principal difference between the Euptiloteae and the Callithamnieae is seen in the earliest stages after fertilization. The fertilized carpogonium enlarges and forms a pair of tube‐like protuberances directed toward the auxiliary cells that are cut off as connecting cells in the Euptiloteae, whereas in the Callithamnieae the carpogonium usually divides into two cells, each of which cuts off a small connecting cell that fuses with an adjacent enlarging auxiliary cell. Nuclei are terminal in spermatangia of the Euptiloteae, subtended by mucilaginous vesicles, and are medial in the Callithamnieae situated between apical and basal vesicles. The Euptiloteae and Callithamnieae (including the Ptilota‐like members) are each strongly supported in maximum‐likelihood tree topologies resulting from analyses of combined 18S rDNA, 28S rDNA, 16S rDNA, and rbcL data sets. Their sister relationship is also well supported.

Section: Discussioncontrasting

confidence: 94%

PROPOSAL OF THE EUPTILOTEAE HOMMERSAND ET FREDERICQ, TRIB. NOV. AND TRANSFER OF SOME SOUTHERN HEMISPHERE PTILOTEAE TO THE CALLITHAMNIEAE (CERAMIACEAE, RHODOPHYTA)¹

Hommersand

Freshwater

Lopez-Bautista

et al. 2006

“…Karyogamy after fertilization also seems to be a rapid process. Karyogamy after attachment of spermatia to the trichogyne occurred in Palmaria in 180 min (Mine and Tatewaki 1994), in Aglaothamnion oosumiense within 2–3 h (Kim and Kim 1999), and in Callithamnion in 5–10 h (O'Kelly and Baca 1984).…”

Section: Natural Fertilizationmentioning

confidence: 99%

RECENT ADVANCES IN FERTILIZATION ECOLOGY OF MACROALGAE¹

Santelices

2002

Our understanding of natural patterns of fertilization in seaweeds has increased substantially over the last 10 years due to new approaches and methods to characterize the nature and frequency of fertilization processes in situ , to recognize the conditions and mechanisms enhancing fertilization success, and to anticipate population and community consequences of the patterns of natural fertilization. Successful reproduction in many species depends on a delicate juxtaposition of abiotic and biotic conditions. Important abiotic factors are those triggering gamete release (e.g. single or interacting effects of light quality and water movement) and those affecting gamete viability or concentrations (e.g. salinity effects on polyspermy blocks; gamete dilution due to water movement). Examples of important biotic components are synchronous gamete release, efficiency of polyspermy-blocking mechanisms, population density of sexually fertile thalli, interparent distances, and male-to-female ratios. Field data indicate fertilization frequencies of 70%-100% in broadcasting-type seaweeds (e.g. fucoids) and 30%-80% in brooding-type (red) algae. Red algal values are higher than previously thought and challenge presently accepted explanations for their complex life histories. Important population and community questions raised by the recent findings relate to the magnitude of gene flow and exchange occurring in many micropopulations that seemingly breed during periods of isolation, the physiological basis and population effects of male-to-male competition and sexual selection during fertilization of brooding seaweeds, and the effects of massive gamete release, especially in holocarpic seaweeds, on benthic and planktonic communities. Comparative studies in other algal groups are now needed to test the generality of the above patterns, to provide critical pieces of information still missing in our understanding of natural fertilization processes, and to elucidate the evolutionary consequences of the different modes of reproduction (e.g. brooders vs. broadcasters).

“…In Callithamnion corymbosum ( J. E. Smith) Lyngbye (Oltmans 1898) and Aglaothamnion halliae (Collins) Aponte, Ballantine and J. N. Norris (Hommersand 1997), the transfer of the diploid nucleus from the carpogonium to the auxiliary cell by means of small connecting cells and the subsequent formation of a residual cell on the auxiliary cell mirrors these processes as they occur in Sciurothamnion. Unlike Aglaothamnion and Callithamnion , however, the fertilized carpogonium of Sciurothamnion does not undergo a mitosis followed by cytokinesis (O'Kelly and Baca 1984, Hommersand 1997), although this is also true for Seirospora (Aponte and Ballantine 1991, 1995, Kraft 1988) and Carpothamnion (Wollaston 1992, as Thamnocarpus ). The carpogonia of two representatives of the Ptiloteae, Georgiella and Euptilota , apparently also do not divide after fertilization (Moe and Silva 1983, Hommersand and Fredericq 2001).…”

Section: Discussionmentioning

confidence: 99%

MORPHOLOGY AND SYSTEMATICS OFSCIUROTHAMNION STEGENGAEGEN. ET SP. NOV. (CERAMIACEAE, RHODOPHYTA) FROM THE INDO‐PACIFIC¹

Clerck¹,

Kraft²,

Coppejans³

2002

A new ceramiaceous alga, Sciurothamnion stegengae De Clerck et Kraft, gen. et sp. nov., is described from the western Indian Ocean and the Philippines. Sciurothamnion appears related to the tribe Callithamnieae on the basis of the position and composition of its procarps and by the majority of post‐fertilization events. It differs, however, from all current members of the tribe by the presence of two periaxial cells bearing determinate laterals per axial cell. Additionally, unlike any present representative of the subfamily Callithamnioideae, no intercalary foot cell is formed after diploidization of the paired auxiliary cells. The genus is characterized by a terminal foot cell (“disposal cell”), which segregates the haploid nuclei of the diploidized auxiliary cell from the diploid zygote nucleus. The nature of three types of foot cells reported in the Ceramiaceae (intercalary foot cells containing only haploid nuclei, intercalary foot cells containing haploid nuclei and a diploid nucleus, and terminal foot cells containing only haploid nuclei) is discussed.