Ascoleucetta amitsba (Hôzawa, 1929) Hozawa, 1929

Cavalcanti, Fernanda F., Rapp, Hans Tore & Klautau, Michelle, 2013, Taxonomic revision of Leucascus Dendy, 1892 (Porifera: Calcarea) with revalidation of Ascoleucetta Dendy & Frederick, 1924 and description of three new species, Zootaxa 3619 (3), pp. 275-314 : 302-303

Ascoleucetta amitsba (Hôzawa, 1929) comb. nov.

Diagnosis: Cortex with conspicuous inhalant apertures. Skeleton composed of three categories of triactines and two of tetractines.

Synonymies: Leucosolenia amitsbo : Hôzawa 1929: 283; Tanita 1943a: 375; Tanita 1943b: 79; Burton 1963: 216; Leucascus amitsbo: Rapp 2004: 124 .

Type material: Tokyo Science Faculty #17 (holotype; Sagami Sea, Japan).

Type locality: Sagami Sea, Japan.

Description: As mentioned before, the redescription of Ascoleucetta amitsba could not be made as the type material is lost (R. Ueshima, personal communication). According to the original description (Hôzawa 1929), the cormus is formed by anastomosed choanocyte tubes. The consistency is firm in the outer part and soft in the inner part. The inhalant apertures are regularly distributed on the sponge surface, and measure from 400 to 1000 μm. The osculum is apical and surrounded by a membrane.

The skeleton is composed of three categories of triactines and two categories of tetractines. Giant triactines compose the cortical skeleton. Inside, small triactines and tetractines are present forming the choanosomal skeleton. The atrial skeleton is composed of triactines and rare tetractines which were considered different from those in the choanosome (Hôzawa 1929).

Spicules (according to the original description; Figure 18 ):

(i) Cortical triactines: Frequently regular. Actines are cylindrical to slightly conical, with sharp tips. Measurements: 220–500 μm (length) x 20–30 μm (width);

(ii) Choanosomal triactines: Regular. Actines are straight, cylindrical, with sharp tips. Measurements: 100–160 μm (length) x 8–10 μm (width);

(iii) Choanosomal tetractines: Similar to the choanosomal triactines. The apical actine is straight and measures 60–150 μm (length) x 4–6 μm (width);

(iv) Atrial triactines: Regular. Actines are straight, cylindrical, with sharp tips. Measurements: 140–240 μm (length) x 6–8 μm (width);

(v) Atrial tetractines: Similar to the atrial triactines. There is no information on the apical actine.

Remarks: Ascoleucetta amitsba was recently transferred to the genus Leucascus (Rapp 2004) . In fact, according to Hôzawa (1929), the cormus is formed by anastomosed choanocyte tubes, and presents both cortex and atrium without choanocytes. Nevertheless, with the revalidation of the genus Ascoleucetta suggested by the present work, we propose the new combination A. amitsba due to the presence of large cortical spicules.

Hôzawa (1929) mentioned that A. amitsba was close to A. ventricosa . He said that the differences between these species were the width of the cortical triactines, and the presence of “trichoxea” (microdiactines) in the latter. After the taxonomic revision of both species we observed that they present very distinct categories of spicules. Ascoleucetta amitsba is composed of three types of triactines and two of tetractines, while A. ventricosa has microdiactines, two types of triactines and one of tetractines. Moreover, the cortical triactines of A. amitsba varies from 220 to 500 μm, and in A. ventricosa it varies from 136.5 to 388.5 μm. The width of the choanosomal spicules also varies: 15.6 to 23.4 μm (triactines) and 15.5 to 20.8 µm (tetractines) in A. ventricosa , and 8.0 to 10.0 μm (both triactines and tetractines) in A. amitsba .

Distribution: North-West Pacific Ocean: Sagami Sea (Hôzawa 1929), and Kosikijima, Kagosima Prefecture (Tanita 1943a)— Japan. Spalding et al. (2007) corresponding ecoregions: Central Kuroshio Current.

Figures

FIGURE 18. Ascoleucetta amitsba. Schematic representation of the spicules (modified from Hôzawa 1929). A, Cortical triactines; B, Triactines of the choanocyte tubes; C, Tetractines of the choanocyte tubes; D, Atrial triactines; E, Atrial tetractines.