Leucetta Haeckel, 1872

Borojevic, Radovan & Klautau, Michelle, 2000, Calcareous sponges from New Caledonia, Zoosystema 22 (2), pp. 187-201 : 193-195

Genus Leucetta Haeckel, 1872

TYPE SPECIES. — Leucetta (Leucettaga) primigenia Haeckel, 1872 by subsequent designation (Dendy & Row 1913).

DIAGNOSIS. — Leucettidae with a homogeneous organisation of the wall and a typical leuconoid aquiferous system. There is neither a clear distinction between the cortex and the choanoskeleton, nor the presence of a distinct layer of subcortical inhalant cavities. The atrium is frequently reduced to a system of exhalant canals that open directly into the osculum.

Leucetta microraphis (Haeckel, 1872) ( Fig. 5 )

Leucetta primigenia var. microraphis Haeckel, 1872 .

MATERIAL EXAMINED. — Several large specimens. LOCALITIES. — Common in the south-west lagoon, Banc Gail, stn 114, 35 m and Baie Sainte Marie.

DESCRIPTION

The collection contains several large specimens, characterized by their massive form, a smooth surface in which the giant triactines can be readily seen, and a very hard and coarse consistency. They are typical of the genus, and resemble closely the specimens we described previously from New Caledonia (Borojevic 1967). Both the cortical and the choanosomal skeletons are composed of numerous giant and small triactines, scattered irregularly. Many giant triactines are present throughout the choanosome, giving it a very firm texture ( Fig. 5 ). The aquiferous system is composed of rather narrow inhalant and exhalant canals that permeate a dense choanosome containing small spherical choanocyte chambers. Larger exhalant canals contain tetractines whose basal system is similar to the choanosomal triactines. The apical actine of the tetractines is short, thin, and curved at the distal part towards the osculum.

Spicules ( Fig. 5 )

Giant triactines, regular, measuring 1230 (± 456) / 85 (± 28) µm. Small triactines, regular, measuring 449 (± 56) / 39 (± 3.4) µm (as are the tetractines).

REMARKS

Numerous Leucetta species with triactines of two different sizes have been described from all the tropical and subtropical seas, under different names, probably representing a complex of species whose classification is very difficult due to the small number of morphological descriptors that can be used to distinguish them. In addition, in the tropical Atlantic region, similar sponges are found that have both giant triactines and tetractines, and that have usually been placed in the species described originally as Leucaltis floridana Haeckel, 1872 . In our earlier studies, we proposed placing all these sponges in a single cosmopolitan species L. microraphis (Borojevic 1967; Borojevic & Peixinho 1976). However, subsequent genetic studies have shown that such an extensive lumping was wrong, and that it does not correspond to genetically defined species (Solé-Cava et al. 1991; Klautau et al. 1994). Consequently, the whole complex of tropical and subtropical Leucetta deserves revision. Until an extensive morphological and genetic comparative study of this complex becomes available, we propose the following division according to spicule types and geographical distribution.

Leucetta microraphis Haeckel, 1872 , sensu Lendenfeld (1885) and Dendy (1892) includes the Pacific species. In the original description, Haeckel (1872) has grouped all the Leucetta with regular equiangular and equiradiate triactines in the species L. primigenia , among which the subspecies L. microraphis and L. megaraphis had two types of triactines of very different sizes. No localities were attributed to the described subspecies, but the Indo-Pacific origin, and in particular the south coast of Australia were cited. In the description of Australian Calcarea, Lendenfeld (1885) proposed elevating L. microraphis to the species level, and this position was subsequently confirmed by Dendy (1892) who reported the species from Port Phillip Heads. In the same study, Dendy included Leuconia dura Poléjaeff, 1883 as a synonym of L. microraphis . Poléjaeff (1883) reported this species from Bermuda and the Torres Straits, and we now consider that the specimen from Australia belongs to the “ microraphis ” complex; while the specimen from Bermuda belongs to the tropical Atlantic complex described below. Borojevic (1967) has previously proposed including the sponge described by Poléjaeff (1883) as Pericharax carteri var. homoraphis from Tristan da Cunha, in the species L. microraphis , as well as the sponge described by Carter (1886) as L. floridana var. australiensis and subsequently renamed by Dendy (1892) as L. carteri . We now prefer to follow Dendy & Row (1913) in retaining them provisionally as valid species. Haeckel (1872) indicated that occasional choanosomal tetractines could be found in L. microraphis , with rather a long apical actine, and Dendy (1892) confirmed this finding. Therefore, the presence of tetractines in our specimen supports its identification as L. microraphis .

Leucetta floridana (Haeckel, 1872) , characterized by the presence of both giant cortical triactines and tetractines, was originally described from Florida, and subsequently reported in the studies of Calcarea from the West Indies and tropical West Atlantic coasts. Borojevic & Peixinho (1976) have analysed an extensive series of specimens from North-East Brazil, and discussed the variability of the relative quantity of giant tetractines. However, since Australian and New Caledonian specimens never have giant tetractines, we now consider that the two species should be distinguished, and the sponges we described as L. microrhaphis from Brazil (Borojevic & Peixinho 1976) should be included into the “ floridana ” complex. Leucetta floridana was also reported for Wasin, East Africa, by Jenkin (1908). Its description is quite short, and the identity of this African species remains to be verified.

Leucetta chagosensis Dendy, 1913 ( Fig. 6 )

Leucetta pyriformis Dendy, 1913 .

L. infrequens Row & Hôzawa, 1931 .

MATERIAL EXAMINED. — Many large specimens from localities 110, 113, 571, 1523.

LOCALITIES. — South-west coast, Dumbea, coral reefs, stn 113. – Dumbea, lagoon, stn 1523. – Nouméa, Redika Island, stn 110, 20 m. – St Vincent, external coral reef, stn 571.

DESCRIPTION

The collection contains several specimens of this sponge, which is reported to be common in the coral reef lagoons. The colour in life is bright yellow, but the preserved specimens are white or brown. The smaller specimens are pyriform, the larger ones are elongate and reach 6 / 2.5 cm. They generally have a single or only a few naked oscula. The surface is either very regular and smooth or bearing small protuberances (photo in Lévi 1998: 77). The sponge wall is 0.3 to 1 cm thick, surrounding a wide central atrium, with a smooth surface bearing the large openings of the exhalant cavities. The inhalant pores are small, opening to larger inhalant cavities that run under the thin cortex. The inhalant canals are tubular, running perpendicular to the surface. The general organization of the wall is somewhat reminiscent of the clathrate structure found in Leucascus , with a distinct radial organization. The exhalant canals are more irregular, hispid due to the presence of tetractines, widen in the proximity of the atrium and form irregular exhalant cavities. The skeleton is composed of triactines of two sizes ( Fig. 6 ). The difference between the two categories of triactines is much smaller than that observed in L. microraphis . The larger triactines are frequent in the cortex, and rather scarce in the choanosome, but the quantity of internal large triactines varies among different specimens. Tetractines with a thin apical actine are found only in the wall of exhalant canals.

Spicules ( Fig. 6 )

Large triactines measuring 480 (± 80) / 38 (± 3.9) µm; small triactines measuring 145 (± 25) / 15 (± 1.2) µm; tetractines with the basal system slightly smaller than triactines, and a slender apical actine.

REMARKS

As previously stated (Borojevic 1967), we have found tetractines in the exhalant canals of the specimens of L. chagosensis described by Dendy (1913) from the Chagos Islands, as well as from the Abrolhos Islands (Dendy & Frederick 1924), and deposited in the Natural History Museum, London. We also pointed out that the larger triactines may be more or less frequent in the choanosome. Consequently, we consider that L. chagosensis is characterized by a regular form; subcortical inhalant cavities; radial organisation of the choanosome as defined by parallel interdigitating inhalant and exhalant canals; the presence of two types of triactines, and of tetractines only in the exhalant canals. In this interpretation of L. chagosensis , we consider that L. pyriformis Dendy, 1913 and L. infrequens Row & Hôzawa, 1931 are probably synonyms of this species, commonly found in the Indo-Pacific region.

Figures

FIG. 5. — Leucetta microrhaphis (Haeckel, 1872). Triactines of the sponge wall. Giant triactines are present in the cortex and throughout the choanosome. Scale bar: 80 µm.

FIG. 6. — Leucetta chagosensis Dendy, 1913. Triactines of the sponge wall. Note a larger triactine, most frequent in the cortical skeleton. Scale bar: 80 µm.