Amphoriscus gregorii ( Lendenfeld, 1891 )

Chagas, Cléslei & Cavalcanti, Fernanda F., 2021, Partial taxonomic revision of Amphoriscus Haeckel, 1870 (Porifera: Calcarea) with description of A. decennis sp. nov., Zootaxa 5061 (1), pp. 39-68 : 49-51

Amphoriscus gregorii ( Lendenfeld, 1891)

Ebnerella gregorii Lendenfeld, 1891

Citations and synonymies: Ebnerella gregorii Lendenfeld 1891: 290 , pl. xi, fig. 66, xiv, figs. 117-123. Amphoriscus gregorii Dendy & Row 1913: 782 ; Topsent 1934: 11; Breitfuss 1935: 30; Burton 1963: 133; Klautau et al. 2017: 105; Cóndor-Luján et al. 2019: 1825.

Type material: BMNH 1896.11 .5.18 (paratype). Lesina, Adriatic Sea (The holotype had not been located) .

Type locality: Lesina, Adriatic Sea.

Analysed material: BMNH 1896.11 .5.18 (paratype; two slides containing sections of the skeleton) .

Morphology: The type specimen was not available. However, according to the original description, the sponge has a branched body formed by several tubes with apical osculum and unified at the base ( Lendenfeld 1891). The aquiferous system is syconoid. Amphiblastulae are easily observed in some of the histological sections ( Fig. 6A ).

Anatomy: The cortical skeleton is formed by giant tetractines and has trichoxeas perpendicularly disposed. The cortical tetractines have a long apical actine, which often protrude through the atrial cavity ( Figs. 6B, C, E ). The subatrial region is formed exclusively by triactines ( Fig. 6E ). The atrium presents tetractines with short apical actine and few triactines ( Fig. 6F ).

Spicules ( Tables 2 and 3 ): A figure containing only the spicule categories, in line with common practice, could not be prepared since only slides containing sections of the skeleton were available.

Cortical tetractines: Slightly conical with blunt tips. The paired actines are long and slightly curved, being usually broken for unknown reasons. The unpaired actine is curved and smaller than the paired ones. The apical actine is long and thick, commonly perforating the atrial wall.

Subatrial triactines: Slightly conical to cylindrical, sharp tips. The paired actines are straight or have a slight curvature when touching the atrial wall. The unpaired actine is straight and long, extending up to the cortical region.

Atrial tetractines: Cylindrical and sharp. Paired actines are long and curved. The unpaired actine is straight and smaller or the same size as the paired ones. The apical actine is short and curved.

Atrial triactines: Not abundant, similar in shape to the atrial tetractines.

Remarks: Lendenfeld (1891) described a set of specimens, with the presence of embryos reported for at least one. Sections of this specimen were represented by the author in plate IV, figure 123b ( Lendenfeld 1891), though we cannot unequivocally confirm that it corresponds to the paratype analysed here based solely on the illustration. Our suspicion was raised by the presence of embryos in BMNH 1896.11.5.18, which can be easily observed along the walls of the choanocyte chambers ( Fig. 6 ).

Ebnerella was erected to allocate species of Amphoriscus with diactines ( Lendenfeld 1891). Ebnerella gregorii was the only species originally described to this genus, which was soon abandoned ( Dendy & Row 1913). After analysing the paratype, we figured out that the diactines mentioned by Lendenfeld (1891) correspond to trichoxeas.

Burton (1963) questioned the presence of atrial triactines in A. gregorii . These spicules were confirmed in this study ( Fig. 6F ). They are not abundant and usually have a broken unpaired actine, which makes it difficult to recognise them immediately.

Compared to other species belonging to Amphoriscus , A. gregorii most closely resembles A. bucchichii . They differ mainly by the presence of atrial triactines in the former, while the latter only has atrial tetractines.Additionally, only one category of tetractines can be seen in the cortical region in A. gregorii , while reports on A. bucchichii by Ebner (1887) mention the presence of subcortical tetractines in addition to the cortical tetractines. Amphoriscus chrysalis , A. cyathiscus , A. cylindrus , A. kryptoraphis , A. oviparus , A. salfii , A. synapta , A. testiparus , and A. urna have tetractines in the subatrial region, which are absent in A. gregorii . Amphoriscus elongatus has triactines in the cortical region while A. gregorii has only cortical tetractines. Finally, the recently described species, A. ancora and A. pedunculatus , have anchoring spicules and peduncle, absent in A. gregorii .

Distribution: Lesina, Adriatic Sea ( Lendenfeld 1891) . Corresponding MEOW: Adriatic Sea ( Spalding et al. 2007).

Figures

FIGURE 6. Amphoriscus gregorii (paratype BMNH 1896.11.5.18). A—Section showing the syconoid aquiferous system and (in detail) a stomoblastula. B—Overview of the skeleton. C—Cortical tetractines. The arrow indicates giant tetractines of long apical actine, which often pierce the atrial wall. D—Microdiactines arranged in the cortex. E—Subatrial region with triactines (arrow). F—Tangential section with atrial triactines (arrow) and tetractines. Abbreviations: at—atrium and ct—cortex.

Tables

TABLE 2. Spicule measurements of Amphoriscus gregorii from the original description (Lendenfeld 1891); p—paired; u—unpaired; a—apical.

Spicules	Actines	Length (μm)	Width (μm)
Trichoxeas		25–40	4
Cortical tetractines	p	350–400	20–26
	u	400–450	20–26
	a	480–520	20–26
Subatrial triactines	p	200	16
	u	220–260	5–12
Atrial tetractines	p	200	12
	u	220–260	12
	a	55	12
Atrial triactines	p	200	12
	u	220–260	12

TABLE 3. Spicule measurements of Amphoriscus gregorii (BMNH 1896.11.5.18) provided by the present work. (P)— paratype; p—paired; u—unpaired; a—apical.

Spicules	Actines	Length (μm)				Width (μm)				N
		Min.	Mean	SD	Max	Min.	Mean	SD	Max
BMNH 1896.11.5.18 (P)
Cortical tetractines	p	100.2	249.8	62.2	377.4	14.1	21.2	3.5	27.3	27
	u	32.3	67.9	37.8	152.4	9.5	18.3	4.0	25.1	20
	a	198.1	305.4	75.3	564.9	15.3	20.7	4.2	39.0	30
Subatrial triactines	p	78.5	132.0	29.3	179.7	6.5	13.3	2.8	17.6	25
	u	158.7	236.8	72.7	453.1	9.7	13.7	2.7	19.4	25
Atrial tetractines	p	99.7	165.8	33.7	220.3	4.8	8.4	1.5	9.9	11
	u	62.9	88.2	19.7	118.2	5.6	8.5	1.7	10.3	10
	a	41.5	47.5	5.4	61.8	4.8	7.3	1.4	9.6	11
Atrial triactines	p	101.5	156.0	31.3	182.3	5.5	9.3	1.0	8.2	11
	u	55.0	75.2	13.7	90.1	5.1	9.0	1.3	6.1	10