Thoosa, HANCOCK, 1849

Carballo, José Luis, Cruz-Barraza, José Antonio & Gómez, Patricia, 2004, Taxonomy and description of clionaid sponges (Hadromerida, Clionaidae) from the Pacific Ocean of Mexico, Zoological Journal of the Linnean Society 141 (3), pp. 353-397 : 385-388

THOOSA HANCOCK, 1849

Synonymy: see Rützler (2002a)

Type species: Thoosa cactoides Hancock, 1849

Diagnosis: Sponges are always papillate. Tylostyles may be missing in some specimens, populations or species. There are many types and variations of microscleres, but most commonly there are amphiasters and oxyasters. Amphiasters are mostly tylote, with microspination on the terminal bulbs, yet variations in different species include smooth oxeote rays. Oxyasters have a very small centre with slender projecting rays 1–6 Mm long. The common reduction of rays can lead to centrotylote sigmoid or tylostylote forms. Because rays tend to be curved, biradiate forms often appear like bird wings. Accessory microscleres in some species may include microxeas and pseudosterrasters (microspined spheres or rhabds) ( Rützler, 2002a).

THOOSA CALPULLI SP. NOV.

( FIG. 21 )

Material examined: MNCN-1.01/239, Islas Isabeles (Nayarit), 21∞46¢35¢¢N-105∞51¢42¢¢W, 20 m depth, 21.xi.1999, boring into dead corals. LEB-ICML- UNAM-417, Islas Isabeles (Nayarit), 21∞46¢35¢¢N- 105∞51¢42¢¢W, 20 m depth, 21.xi.1999, boring into dead corals .

Description: Sponge growing in alpha stage, with small papillae from 0.5 to 0.9 mm in diameter, very regularly formed. They are rarely visible externally and never fused. The species excavates coral substrates, forming irregular or regular cavities that are 0.8–1.3 mm. Colour is pale yellow in alcohol.

Skeletal characters: (i) Amphiasters with seven microspined rays at each side of the shaft ( Fig. 21A ). Two shape categories exist but measurements overlap. One category has thick actins ending in spiny knobs with a sharp point (18.7–21 by 13–13.5 Mm), and the other has more slender amphiasters, bearing small conical spines at the ends (10.5–23 by 7.5–16.5 Mm). (ii) Smooth oxyasters have a small centrum. They are biradiate like bird wings, triradiate, tetraradiate or symmetric with six rays ( Fig. 21B ). Rays measure 16– 49.5 by 2–2.5 Mm; (iii) Centrotylote oxea are slightly spined ( Fig. 21C, D ), in two size categories: (a) 30–46.5 by 3 Mm; (b) 133.5–270 by 5–6.7 Mm. (iv) Smooth oxeas.

Etymology: The word calpulli comes from the Nahuatl which meant the joining in marriage during the Mexica era in Tenochtitlan; referring to the joining of the sponge with the coral substrate.

Remarks: see below.

Distribution: Islas Isabeles (Pacific Ocean, Mexico).

THOOSA MISMALOLLI SP. NOV.

( FIGS 22 , 23 )

Material examined: MNCN-1.01/240, Los Arcos (Puerto Vallarta, Jalisco), 20∞32¢73¢¢N-105∞18¢47¢W, intertidal, 23.i.2001, boring into dead corals. LEB- ICML-UNAM-361, Los Arcos (Puerto Vallarta, Jalisco), 20∞32¢73¢¢N-105∞18¢47¢W, intertidal, 23.1.2001, dead corals. LEB-ICML-UNAM-483, Antiguo Corral del Risco ( Punta de Mita , Nayarit), 20∞46¢20¢¢N-105∞32¢49¢¢W, 4 m depth, 06.iv.2002, boring into dead corals. LEB-ICML-UNAM-524, Los Arcos (Puerto Vallarta, Jalisco), 20∞32¢73¢¢N- 105∞18¢47¢W, 4 m depth, 10.iv.2002, boring into shells of Crassostrea sp .

Description: Excavating sponge on coral substrate found only in alpha stage. Papillae are small, from 1.3 to 3.5 mm in diameter, most frequently circular in form, and 0.5–2 mm apart. Fusion of papillae has not been observed. The species is very difficult to observe ‘ in situ ’ due to the small size of its papillae. However, if the coral is fragmented, the bright orange tissue of the sponge is visible to the naked eye.

Skeletal characters: The spiculation is typical of the genus. (i) Amphiasters have 14 tylote nodules, seven at each side of the shaft. They can be separated in two shape categories: thick tylote amphiasters, with very reduced spines or with very short spines (19.5–24 Mm long ¥ 10.5–18 Mm wide) ( Fig. 22 ). In some cases the amphiasters look like nodules with a verrucose surface (9–18 Mm long ¥ 6–10.5 Mm wide), and slender amphiasters, with a verrucose surface. (ii) Oxyasters in two categories ( Fig. 23A ): (a) the reduced type; with smooth and microspined rays which have an elongated or irregular centre at the junction, these are biradiate, triradiate, tetraradiate forms, rays measure 21– 30 ¥ 1.5–3 Mm; (b) oxyasters in symmetric forms with six rays, each ray 13.5–15 ¥ 2.5 Mm. Some oxyasters have microspined rays, and swollen tips. (iii) Centrotylote oxea are smooth and/or spined, these are like an oxyaster ray in appearance, total longitude is 69– 70.5 ¥ 1.5–3 Mm. The oxeas can end in a sharp or blunt point ( Table 11). A low proportion of slender tylostyles were found. They measure 254 ¥ 4 Mm on average (7 Mm head width) ( Fig. 23B ).

Etymology: The specific epithet refers to the village of Mismaloya from the Bahía de Banderas (Jalisco, Mexico).

Distribution: Bahía de Banderas (Jalisco, Mexico). east Pacific Ocean.

Remarks: There have been very little reports of the genus Thoosa around the world, e.g. T. mollis , T. armata , T. cactoides , T. bulbosa , T. fisheri Topsent, 1891 , T. amphiasterina , without mentioning the erroneous allocation names, like T. hancocki (= Cliothosa hancocki ) ( Topsent, 1887), as well as other Thoosa species which have a different spiculation not proper to the genus, which is probably the case of Thoosa socialis ( Carter, 1880) with rough microspined circular discs. Moreover, all of them are located in an unclearly stated geographical area, far distant from the present Pacific location. It is difficult to attempt a comparison of the different species because collections are too old or are lost ( Rützler & Stone, 1986). A species similar to T. calpulli sp. nov. is T. armata Topsent, 1891 , which has tylostyles (lacking in T. calpulli ), and a very different ornamentation of the amphiasters. Thoosa calpulli presents small, conical spines; in contrast, T. armata has larger curved spines. Another close species could be Thoosa amphiasterina Topsent, 1920 , which has very similar amphiasters. However, T. amphiasterina has no oxyasters nor centrotylotes oxeas. The closest species to T. mismalolli sp. nov. seems to be T. bulbosa Hancock, 1849 from the Indo- Pacific, but this species has oxyasters of the reduced type with oversized rays (70 Mm), and no centrotylote oxeas. Thoosa mismalolli and T. calpulli are the first records of Thoosa for the east Pacific. These two are excavating sponges on calcareous substrates, appearing in small papillae, and only present in the alpha stage of growth. Larger growth forms have not been found over a period of 25 years of observing different sponges along the Mexican Pacific coast.

Figures

Figure 21. Thoosa calpulli sp. nov.: A, amphiasters with microspined rays; B, different forms of smooth oxyasters; C, small spined oxea; D, smooth and spined centrotylote oxeas.

Figure 22. Thoosa mismalolli sp. nov.: different forms of nodulose amphiasters.

Figure 23. Thoosa mismalolli sp. nov.: A, different forms of oxyasters and oxeas; B, head and tip of tylostyles.