Crambe panamensis, Maldonado, Carmona, van Soest & Pomponi, 2001

Maldonado, Manuel, Carmona, M. Carmen, Van Soest, Rob W. M. & Pomponi, Shirley A., 2001, First record of the sponge genera Crambe and Discorhabdella for the eastern Pacific, with description of three new species, Journal of Natural History 35 (9), pp. 1261-1276 : 95-97

Crambe panamensis n. sp.

Material collected. USNM 51470 , paratype HBOM-003:00951 .

Type locality. Pacific coast of Panama, Gulf of Chiriqui, Isla Montuosa 7 ° 27.992 ' N, 82 ° 15.629 ' W). Paratypes collected at a nearby site (7 ° 27.932 ' N, 82 ° 15.611 ' W).

Etymology. The species name refers to the geographical location of the type locality.

Description. The holotype is a 14 ✕ 10 cm, encrusting sponge that was growing on a living thorny oyster. It was pinkish red when alive, and faded in ethanol. In the many living individuals observed in situ, the ectosome was epithelium-like, translucent, with spacious subectosomal cavities that collapse after fi xation; oscula were distended, slightly raised, 1-2 mm in diameter; groups of exhalant canals converged towards the oscula showing a radial pattern, as typically seen in other species of Crambe . Ostia were not visible with the naked eye, but under magni fi cation, they were visible in aerolated areas, 400-600 μm diameter, that were scattered all over the sponge surface. The surface is microscopically hispid.

The skeleton consists of four spicule types, as follows:

(1) Ectosomal subtylostyles: 117-208 μm ✕ 2.5 -3.5 μm; straight, relatively isodiametric, with an oval subtyle, and with a tapering, sharp point ( figure 1a, b ). Feeble vestiges of microspines, which are hard to see even under magni fi cation, surround the point ( figure 1b ).

(2) Choanosomal tylostyles: 180-300 μm ✕ 6.5 -12 μm; straight or somewhat curved, slightly fusiform, with an irregularly shaped, well-marked tyle ( figure 1c ).

(3) Astroclone desmas: in a wide variety of growth stages ( figure 1d -h ). Fully formed desmas have a well-developed centrum, from which four to seven main actines radiate, along with one in four additional, shorter processes (actines or ornamental spines?), up to a maximum of eight radiating processes. Fully grown actines, if in contact with other desmas, develop a fl at, terminal expansion called zygome plate ( figure 1e -f ); zygomes articulate inter-spicule contacts to build up a network of interlocked, but not fused, desmas. If actines contact no nearby spicule, actinal ends remain unexpanded and blunt ( figure 1e ). Early developing stages of astroclone desmas, which were fairly common in the sponges collected, resemble oxyasters with four to eight irregular, blunt actines ( figure 1g, h ). Fully grown desmas measure up to 65 μm in largest diameter, with some early developing stages as small as 26 μm across.

(4) Isochelae: 20-22 μm; with three to fi ve well-formed, anchorate teeth ( figure 1i ). These spicules are infrequent in the sponges.

The arrangement of the spicule types within the sponges consists of a basal stratum of more or less interlocked astroclones that rests on a basal spongin layer from which short tracts of subtylostyles cored by one or several main choanosomal tylostyles ascend. Ascending tracts become hispid tufts when they reach the sponge surface. Isochelae are very scarce and occur mostly in the ectosome.

Habitat. This species is fairly common at the collection site (Isla Montuosa, Pacific coast of Panama), particularly on overhangs, vertical walls, and sites moderately exposed to sunlight, at depths of 10-30 m. It grows on rocks, but also overgrows living barnacles and oysters.

Taxonomic remarks. The fact that Crambe panamensis n. sp. produces desmas with only radiating arms (i.e. astroclones) clearly distinguishes this species from all three Mediterranen species ( table 1 ), Crambe crambe , Crambe tuberosa and Crambe tailliezi , which produce only sphaeroclone desmas (i.e. desmas with all actines curved towards the substratum, when fully developed).

Astroclones similar to those of Crambe panamensis n. sp. occur in two other species, Crambe erecta and Crambe acuata . Because C. erecta , a species only known by its holotype from the East Coast of Africa (North Kenya Bank), produces isochelae in two size categories, whereas C. panamensis produces only one category, the speci fi c distinction is clear.

Differentiation between the skeleton of Crambe panamensis n. sp. and that of Crambe acuata is somewhat more complicated. The latter species, known from the South Atlantic ( Namibia and South Africa), the Red Sea and Madagascar, shows an enormous skeletal variability between populations ( table 1 ). South Atlantic populations of C. acuata are characterized by ectosomal and choanosomal tylostyles, abundant astroclones, a single category of isochelae, and microxeas ( Lévi, 1960, 1963; Uriz, 1988). Populations from the Red Sea and Aldabra (northern Madagascar) produce ectosomal and choanosomal tylostyles, isochelae in two size categories, very few astroclones (see Vacelet et al., 1976) and no microxeas ( Lévi, 1958, 1961). The population from Tulear (southern Madagascar) produces spicules as those described above, but with isochelae in a single size and microxeas in variable abundance, depending upon individuals (dubious species assignations, according to Vacelet et al., 1976, are not considered here). Because of the skeletal differences explained above, the Indian Ocean populations of C. acuata were originally described as Folitispa acuata Lévi, 1958 , whereas the South Atlantic populations were described as Crambe chelastra Lévi, 1960 . This synonymy was proposed by Vacelet et al. (1976) and has been accepted ever since, although a review of such a taxonomic decision would be advisable if new material is collected ( Maldonado and Uriz, 1996; Lévi, personal communiction).

The absence of microxeas in C. panamensis n. sp. differentiates it from the South Atlantic and Tulear populations of Crambe acuata ( table 1 ). The new species can also be differentiated from Red Sea and Aldabran populations of C. acuata , because the latter two, though also lacking microxeas, produce isochelae in two size categories ( Lévi, 1958, 1961), whereas only one size category is present in C. panamensis ( table 1 ). Taxonomic differentiation is also supported by the widely disjunct geographical distribution between the eastern Pacific populations of the new species and the nearest populations of C. acuata in Madagascar and the Red Sea. Indeed, the presence of this new species on the Pacific coast of Panama, along with the occurrence of a New Zealand fossil species known from Tertiary strata, strongly suggest that the genus Crambe , also known from the Mediterranean, the eastern South Atlantic, the Red Sea and the western Indian Ocean, was perhaps once widespread in the Tethys Sea and has persisted to the Recent with relative success in some biogeographical regions. This idea is consistent with recent experimental work that has shown that concentration of silicic acid in surface waters of modern oceans is insufficient for the sublittoral species Crambe crambe to produce its desmas ( Maldonado et al., 1999). Such a fi nding suggests that the genus Crambe ━or a direct, close ancestor━appeared in a shallow-water environment that was still rich in dissolved silica, predating the chronic silicon exhaustion characteristic of surface water in modern oceans and that was caused by the expansion and diversi fi cation of the diatoms over the Cretaceous ( Harper and Knoll, 1975; Maliva et al., 1989; Maldonado et al., 1999).

Figures

FIG. 1. Spicules of Crambe panamensis n. sp.: (a) point and tyle of an ectosomal subtylostyle; (b) point of a subectosomal subtylostyle with feeble spines (sp); (c) tyle of a choanosomal tylostyle, where vestiges of a tubercle (tb) can be seen; (d-f) fully grown astroclones with diversely developed actines that show both zygomes (z) and blunt ends (be); (g) early developing stage of an astroclone; (h) comparative view of fully grown desmas (gd) and early developing stages (dd); (i) isochela.