Melobesioideae Bizzozero, 1865:109

Mateo-Cid, Luz Elena, Mendoza-González, A. Catalina & García-López, Deisy Y., 2014, Systematic survey of Lithothamnion, Melobesia and Mesophyllum species (Hapalidiaceae, Corallinales, Rhodophyta) recorded along the Atlantic coast of Mexico, Phytotaxa 164 (4), pp. 226-238 : 227-234

Subfamily Melobesioideae Bizzozero, 1865:109

Lithothamnion Heydrich 1897: 412

Lithothamnion crispatum Hauck (1878: 289) Figs. 1–6

Basionym: Lithophyllum crispatum (Hauck) Hauck 1885: 270

Heterotypic synonyms: see Basso et al. (2011)

Type Locality: Rovigno, Adriatic Sea

Description: Thalli belongs rhodolith with fruticose to foliose growth form. The protuberances are cylindrical to compressed, up to 15 mm long and up to 3 mm wide at their flared, distal end. Thallus is pseudoparenchymatous, monomerous and dorsiventrally organized; haustoria are unknown. The crustose portion of the thallus is 200–500 µm thick, with a medulla (ventral region) 50–100 µm thick, composed of filaments running more or less parallel to the thallus surface. The mean size of medullar cells is 19 µm in length and 10 µm in diameter. The ventral filaments curve toward the thallus surface to form a zoned dorsal region (cortex). Cortex cells measure 14.5–23.5 µm in length and 7–18 µm in diameter. Epithallial cells occur singly: they are flattened and flared and measure 3–5.5 µm in length and 7–14.5 µm in wide. Subepithallial initials longer than or as long as their inward derivatives. Cells of adjacent medulla and cortex are connected by cell fusions. Secondary pit connections and trichocytes have not been observed. The conceptacle roof is slightly protruding above the surrounding thallus surface, 20–50 µm thick, and composed of four to six layers of cells filaments lining the pore canals differ from other roof cell filaments in usually consisting of only two to three cells. In the Mexican material, the size of multiporate conceptacle chambers is 270–720 µm in diameter and 100–315 µm in height. Gametangial plants dioecious; 500–600 µm thickness, with the same vegetative structure as the vegetative plants; spermatangia produced in conceptacles in different thalli, spermatangial conceptacles uniporate, buried in the pseudoparenchymatous tissue or protruding, apiculate, scattered, elliptical chambers 450–500 µm diameter and 50–150 µm high, male conceptacle showing dendroid (branched) spermatangial systems on the floor, and simple (unbranched) spermatangial systems on the walls and roof of the conceptacle. Spermatangia are 2–3µm in diameter.

Remarks: The vegetative and reproductive features of our specimens correspond to those reported by Basso et al. (2011) from Mediterranean Sea material. These authors indicated that L. crispatum not only occurs in the Mediterranean, also is known to occur throughout the Atlantic and Indian Ocean and eastward to the Pacific coast of Australia.

Geographical distribution: Adriatic, Croatia, France, Greece, Italy, Spain, Algeria, Libya, Turkey, Mauritania, Sudan, New Zealand, Australia, South Africa, Tanzania, Revillagigedo Islands, Maldives, Panama, Brazil ( Basso et al. 2011, Guiry & Guiry 2014).

Examined material: Mexico. Campeche: Campeche Banks , 11-June-2005, Mendoza González & Mateo Cid ( ENCB 19635 ) ; 14-June-2005, Mendoza González & Mateo Cid ( ENCB 19646 ) ; Quintana Roo: Mujeres Island , 14-August-1997, Searles ( ENCB 20101 ) .

Lithothamnion occidentale (Foslie) Foslie (1908: 3–4) Figs. 7–9

Basionym: Lithothamnion fruticulosum var. occidentale Foslie 1904: 12

Homotypic synonyms: Lithothamnion fruticulosum var. occidentale Foslie 1904: 12

Type Locality: Cruz Bay , St. John Island, US Virgin Islands .

Description: Thalli constitute rhodoliths, unattached, smooth and glossy and irregularly branched, others highly branched. Branches terete and 1–2 mm in diameter. Thallus is pseudoparenchymatous, haustoria are unknown. Branches with a medulla composed of plumose filaments running more or less parallel to the thallus surface. The mean size of medullar cells is 14–16 µm in length and 17–18 µm wide. The ventral filaments curve toward the thallus surface to form a zoned dorsal region (cortex). Cortex cells measure 35–37 µm in length and 15–19 µm in diameter. Epithallial cells occur singly: they are flattened and flared and measure 6–8 µm in length and 7–10 µm wide. Subepithallial cells are rounded-shape. Cells of adjacent medulla and cortex are connected by cell fusions. Secondary pit connections and trichocytes have not been observed. The multiporate conceptacle chamber is 240– 330 µm in diameter and 170–180 µm high. The conceptacle roof is protruding above the surrounding thallus surface, 40–50 µm thick, and composed of two or three layers of cells filaments lining the pore canals differ from other roof cell filaments in usually consisting of only two to three cells. Tetrasporangia 70–80 µm high and 30–35 µm wide.

Remarks: Fragmented thallus was observed, representing the likely form of propagation of this species.

Geographical distribution: Florida, North Carolina, South Carolina, Cuba, Hispaniola, Puerto Rico, Brazil, Colombia, Venezuela, Indonesia ( Taylor 1960, Guiry & Guiry 2014).

Examined material: Mexico. Veracruz: Enmedio Island, Sacrificios Island ( Ortega et al. 2001: 155) ; Yucatán: Alacranes Reef ( Ortega et al. 2001: 155) ; Campeche: Campeche Banks , 09-June-2005, Mendoza González & Mateo Cid ( ENCB 19646 ) ; Quintana Roo, Puerto Morelos ( Ortega et al. 2001: 155); Mujeres Island , 14-August- 1997, Searles ( ENCB 18590 ) .

Lithothamnion sejunctum Foslie (1906: 3) Figs. 10–14

Type Locality: St. Croix , US Virgin Islands .

Description: Thalli are encrusting grown on intertidal rocks, following the contour of the substrate, without protuberances, attached to the substratum ventrally by cell adhesion, 180–250 µm thick. Thallus with monomerous construction; in transversal section medullar cells 30–38 µm long and 7–9 µm wide. Cortical cells 10–12 µm high and 6–7.5 µm wide. Subepithallial cells compressed, epithallial cells 2.5–3.5 µm high and 7–8 µm wide. Adjacent filaments linked by cell fusions, secondary pit-connections and trichocytes absent. The multiporate conceptacle chamber is 150–170 µm in diameter and 70–80 µm high. The conceptacle roof is protruding above the surrounding thallus surface, 50–70 µm thick, and composed of three or four layers of cells filaments lining the pore canals differ from other roof cell filaments in usually consisting of only two to three cells. Tetrasporangia 45–50 µm high and 20–25 µm wide.

Remarks: Taylor (1960) mentions that the thalli of L. sejunctum are epilithic and encrusting. Also, dimensions of tetrasporangial conceptacles are similar to those cited of Taylor. This is a new record for Mexico and represents the third record since it was first described.

Geographical distribution: Virgin Islands, Brazil ( Taylor 1960, Guiry & Guiry 2014).

Examined material: Mexico. Veracruz: Verde Island , 24-April-1966, Chávez & Ramírez ( ENCB 20072 ) ; Cabezo Sur Reef , 12-November-2008, Castillo & Coronado ( ENCB 20074 ) . Quintana Roo: Cayo Norte , 11-July-1982, Huerta Múzquiz ( ENCB 18682 ) ; Cayo Centro , 08-July-1982, Huerta Múzquiz ( ENCB 18688 ) .

Melobesia Heydrich 1897: 408

Melobesia membranacea (Esper) J.V. Lamouroux (1812: 186) Figs. 15–18

Basionym: Corallina membranacea Esper 1796 : pl. Corallina XII

Homotypic Synonyms

Corallina membranacea Esper 1796

Epilithon membranaceum (Esper) Heydrich 1897

Lithothamnion membranaceum (Esper) Foslie 1898

Heterotypic Synonyms

Hapalidium roseolum Kützing 1843

Melobesia corticiformis Kützing 1849

Hapalidium roseum Kützing ex Areschoug 1852

Melobesia rosea Rosanoff 1866

Lithothamnion corticiforme (Kützing) Foslie 1898

Melobesia hildenbrantioides (P.L.Crouan & H.M.Crouan) Foslie 1898

Melobesia coccinea (P.L.Crouan & H.M.Crouan) Foslie 1898

Epilithon corticiforme (Kützing) Heydrich 1908

Type Locality: West coast of France ( Dawson 1960:8) .

Description: Thallus pseudoparenchymatous, encrusting without protuberances, rounded, contiguous thalli ever overlapped. Continuous margin without orbital ridges which is confused with the substratum, lobed, crenate edge. Intertidal habitat epiphytic on leaves of Thalassia testudinum . Internal organization dorsiventral, thallus dimerous: composed of two distinct groups of filaments: a single ventral layer of laterally cohering filaments composed of rectangular cells: 10–12 µm length and 5–7µm wide; and a second layer composed by epithallial cells: triangular or elliptical (partially covering the mother cell lying beneath), erect filaments: absent or reduced to few cells. Tetrasporangial conceptacles: multiporate (7–18 pores), hemispherical with flat roof, numerous, raised, spread on surface or grouped and confluent. Old conceptacles break leaving small oval cavities with raised edge, tetrasporangial chamber: 90–100 µm diameter and 50–60µm high. Tetrasporangia 26–50 µm high and 15–26 µm wide.

Remarks: Melobesia membranacea was the commonest species in this study, observed at several localities. It was also the most frequently recorded species in earlier studies, probably because M. membranacea is readily recognized by multiporate conceptacle. Melobesia appears to be widespread, but many records require confirmation.

Geographical distribution: Florida, México, Virgin Islands, Panamá, Venezuela, Brazil. Ireland, Great Britannia, New Zealand, Australia, Angola ( Guiry & Guiry 2014).

Examined material: Mexico: Veracruz Monte Pío ( Sánchez-Rodríguez 1965: 12); Enmedio Island, Verde Island, Sacrificios Island ( Ortega et al. 2001: 155); Campeche, Campeche ( Ortega et al. 2001: 155); Yucatán: Dzilam de Bravo, 15-April-2007, Mendoza González & Mateo Cid ( ENCB 20094); Alacranes Reef, 27-June-1961, Azis & Humm ( ENCB 20093); Quintana Roo: Laguna Nichupté, 01-August-1984, Mendoza González & Mateo Cid ( ENCB 20076); Playa del Carmen, 03-November-1984, Mendoza González & Mateo Cid ( ENCB 20075); Punta Valencia, Ascensión Bay, 14-March-2009, Acosta Calderón ( ENCB 20090); Punta Sacrificios, 16-April- 2012, Mendoza González, García López & Mateo Cid ( ENCB 20097); Vigía Chico, 18-May-1998, Mendoza González & Mateo Cid ( ENCB 19327); Mujeres Island, 13-October-1983, Huerta Múzquiz, Mendoza González & Mateo Cid ( ENCB 20095); Cozumel Island, San Juan Beach, 03-November-1984, Mendoza González & Mateo Cid ( ENCB 20078); Chen Río, 21-June-2010, Mendoza González, Mateo Cid & Trinidad Calderón ( ENCB 20092).

Mesophyllum Lemoine 1928:251

One species representing the genus Mesophyllum was identified during the present study.

Mesophyllum mesomorphum (Foslie) Adey (1970: 25) Figs. 19–24

Basionym: Lithothamnion mesomorphum Foslie 1901: 5–6

Homotypic Synonym: Lithothamnion mesomorphum Foslie 1901

Type locality: Bermuda; [no other locality data]

Description: Thalli are foliose, up to least 2 cm in extent, weakly attached and grow with major parts of their thallus unattached. The surface of the thallus is smooth, protuberances are lacking. The margins are always free and have a whitish border (cuticle). Growing on Flahaultia sp. , collected by SCUBA at 11 m deep. The thallus is organized dorsiventrally and reaches 120–300 µm in thickness and composed of a predominantly coaxial medulla 80–200 µm thick, where cells form arching decumbent tiers in length series, medullar cells are 15–20 µm length and 10–12 µm wide; cortical cells are 6–9 µm length and 7–9 µm wide. The epithallium develop one or two layers of cells, epithallial cells are roundish to slightly flattened, 7–9 µm in diameter and 7–9 µm length. Fusions between medullar and cortex cells are common. Trichocytes and secondary pit connections are absent. Multiporate conceptacles are perforated by 60–90 pores develop bisporangia, within chambers that are 400–750 µm in diameter and 300–350 µm high and bisporangia are 110–120 µm high 50–60 µm wide. Pores are 45–50 µm length and 8–10 µm in apical diameter, in superficial view the pores of the conceptacle are surrounded by 6–7 rosette cells, in section roof the cells lining the pore canal are rounded and different in size and shape to contiguous epithallial cells. Gametangial thalli not observed.

Remarks: M. mesomorphum is easily distinguishable by its habit almost free, thallus lamellate, epithallium distromatic and the diameter of chambers’ bisporangial of 400–750 µm in diameter. However, the diameters of the sporangial chambers recorded by Taylor (1960) of 100–140 µm in diameter do not match with our specimens.

Geographical distribution: Mexico: Veracruz Enmedio Island (Lehman & Tunnell 1992); Quintana Roo Puerto Morelos ( Dreckmann et al. 1996); Cozumel Island ( Mateo-Cid et al. 2006); Caribbean Islands, Colombia ( Wynne 2011), Comoros, Seychelles, Korea, Australia, New Zealand, Hawaii and Federate States of Micronesia ( Guiry & Guiry 2014).

Examined material: Mexico; Campeche: Campeche Banks , 15-June-2005, Mendoza González & Mateo Cid ( ENCB 19201 ) ; Quintana Roo, Cozumel Island , Colombia Reef, 20°13’53”N, 87°01’09”W; 21-March-1994, Searles ( ENCB 18725 ) .

Figures

FIGURES 1–6. Lithothamnion crispatum, Campeche Banks (ENCB 19635). 1) Habit of a plant encrusting pebbles. 2) Habit of three rhodoliths. 3) Section through the thallus showing a strongly coaxially medulla (brace). 4) Section throughout dorsal region note cellular fusion (arrow). 5) Section through mature tetrasporangial conceptacle.6) Mature male conceptacle with spermatangial filaments on the floor and roof of the chamber

FIGURES 7–9. Lithothamnion occidentale, Campeche Banks (ENCB 19646). 7) Habit of two rhodoliths. 8) Transversal Section of branches, note the medulla (arrow) and cortex. 9) Section through mature tetrasporangial conceptacle, note the tetrasporangium (arrow) and in the box at the top right note two pore canal (arrows). FIGURES 10–12: Lithothamnion sejunctum, Banco Chinchorro (ENCB 18682). 10) Habit of a plant encrusting rocks. Brace indicated a species of Lithophyllum. 11) Section through the thallus showing monomerous construction, note the medulla (brace). 12) Section through dorsal region note the cortex (arrow).

FIGURES 19–24. Mesophyllum mesomorphum, Cozumel Island (ENCB 18725). 19) Habit of foliose thalli attached to red algae. 20) Section through the thallus showing a strongly coaxially medulla (brace). 21) Section through dorsal region noted the cortex (arrow). 22) Section through bisporangial conceptacle shows mature bisporangium (arrow). 23) Enlarged section through bisporangial conceptacle showing pore canal lined by elongated cells (arrow). 24) Detail of a pore canal of a multiporate roof shows from above, is surrounded by 6 rosette cells (arrows).