Pectispongilla gagudjuensis, Manconi, R., Cubeddu, T. & Pronzato, R., 2016

Manconi, R., Cubeddu, T. & Pronzato, R., 2016, Australian freshwater sponges with a new species of Pectispongilla (Porifera: Demospongiae: Spongillida), Zootaxa 4196 (1), pp. 61-76 : 69-74

Pectispongilla gagudjuensis n. sp. Manconi & Pronzato

Figs 1 b, 6, 7, 8, 9; Tables 1, 2, 4

Material. Type material NTM ZOO 2024, NTM ZOO 2680, NTM ZOO 4338, NTM ZOO 4339, NTM ZOO 4340 from a small unnamed dry creek, 12°43’S 132°46’E ( Fig. 1 , site b) along the Kakadu Highway, North of Malabanjbanjdju, Kakadu National Park , Alligator River Region , Northern Territory, 11.vii.1998, leg. Luca Pronzato. Some slides and stubs (DTRG-FW568 a, b, c, d, e) are deposited in the authors’ collection.

Comparative material. Pectispongilla botryoides NTM Z001405 (DTRG-FW646) and part of the latter as AM Z3504 (DTRG-FW701), Tanami Gorge, 19°58’S 129°39’E, Camel Waterhole , Northern Territory , 25.v.1970, leg. P. Latz, S. Parker & D. Howe, det. A.A. Racek; AM Z2905, Manchester Lake, Queensland , 6.ix.61, det. A.A. Racek (DTRG-FW700). P. aurea var. subspinosa , syntype, BMNH 14.11 .24.34 (ex ZEV 3790/7), Kochi (ex- Cochin), Ernakulam , Kerala, SW India (DTRG-FW401) ; USNM 34578 , Penney collection 90124, schizosyntype, dry, Kochi (ex-Cochin), Ernakulam , Kerala, SW India (DTRG-FW553) ; ZMB 7981 from BMNH 14.11 .24.34, alcohol, Kochi (ex-Cochin), Ernakulam , Kerala, SW India (DTRG-FW515).

Etymology. The specific epithet refers to the native word Gagudju (from which Kakadu) derived from the name of one of the ca. thirty old native languages of the flood plain area in the Arnhem Land.

Diagnosis. Pectispongilla gagudjuensis n. sp. is characterised by two types of short skeletal megascleres (acanthostrongyles and acanthoxeas), absence of microscleres, free gemmules, mature botryoidal gemmuloscleres with disto-lateral apices as irregular concavities grouped to form a botryum, and growth form as a small hollow cup in dry condition.

Description. Growth form encrusting as minute almost flat cushions (max. 1 cm in diameter) scattered and strictly adhering to substrata by basal spongin plate. Surface smooth. Consistency hard and fragile. Colour white. Oscul e apical, single, central, large (300–350 µm in diameter). Ectosomal skeleton compact and dense arrangement of spicules more or less tangential. Choanosomal skeleton vaguely reticulate network of spicules joined by scanty spongin. Spongin scanty except for basal spongin plate and gemmular theca. Megascleres of two types. Dominant acanthostrongyles [90–168 (135±19) x 8–13 (10±4) µm] almost straight to notably bent (boomerang-like shaped), spiny by few scattered short spines sometimes more dense at the tips. Acanthoxeas (mucronate acanthostrongyles?) [130–205 (163±19) x 5–12 (8.5±1.9) µm] less frequent, gradually to abruptly pointed, with short spines from scattered to more dense at the tips. Microscleres absent. Gemmules free (up to 8 for each specimen), small (200–350 µm in diameter), subspherical after rehydration with gemmuloscleres more or less radially embedded. Foramen single with a short tube and a well developed collar. Gemmular theca thick, trilayered. Outer layer with a variable amount of compact spongin, as a honeycomb-like surface due to the partial emergence of distal botryoidal apices of gemmuloscleres. Pneumatic layer as an irregular network of anastomosing thin spongin fibres. Inner layer of sublayered compact spongin. Gemmuloscleres botryoidal (mature) to pseudo-botryoidal (immature) [26–46 (36±4) x 2–3 (2.9±0.29) µm] with smooth, straight to slightly bent shafts and a range of variable shape at the convex side of each tip according with the age of the spicules. Immature gemmuloscleres with disto-lateral arrangement of simple small spines in rows (pseudo-botryum); botryum-like tips in growing spicules with a progressive increase of siliceous webs joining spines one to each other; true botryoidal tips with a cluster of well developed rounded concavities in more aged gemmuloscleres.

Remarks. A comparative analysis of Pectispongilla gagudjuensis n. sp. showed that it matches only in part diagnostic traits of the other species of the genus ( Table 4 ). The skeletal megascleres are shorter than the other species of the genus and the gemmules are the largest of the genus. Microscleres are absent in P. gagudjuensis n. sp., whereas microscleres of P. aurea Annandale, 1909 and P. subspinosa Annandale, 1912 are smooth to microspined oxeas ( Penney & Racek 1968, p. 78–79) and those of P. stellifera Annandale, 1915 range from microspined oxeas to subspherical tubercled spherasters ( Penney & Racek 1968, p. 79). Compared with the Australian P. botryoides Haswell, (1882) and the other species of the genus the gemmuloscleres of the new species have the shorter shafts. Moreover the gemmuloscleres of P. gagudjuensis are characterized by displaying the entire range of the various tip morphs ( Fig. 8 ) hitherto recorded in the other four species of Pectispongilla i.e. from small spines in rows (immature gemmuloscleres) up to well developed botryoidal-like apices (mature spicules). The peculiar body architecture deeply diverges from Pectispongilla species and all other Spongillida i.e. reduced in dry condition to an almost hollow cup with megascleres to form the body wall and containing only free gemmules and a few spicular tracts. This morpho-functional trait has never been hitherto described for the family Spongillidae and is comparable only to the Baikalian Swartschewskia papyracea (Dybowsky, 1880) in dry condition. This body architecture, closely adhering to the substratum by a thin spongin basal plate, indicates its functional role as a protective device for gemmules during the long, harsh dry season. Its morpho-functional role is comparable to that performed by the gemmular cages of megascleres enveloping the gemmular theca found in other genera of Spongillida. P. gagudjuensis however diverges in the depth of the gemmular cage architecture described for other genera (e.g. Corvospongilla Annandale, 1911 ; Heterorotula Penney & Racek, 1968 ; Uruguayella Bonetto & Ezcurra De Drago, 1969 ; Pachyrotula Volkmer-Ribeiro & Rützler, 1997 ).

In synthesis, exclusive traits of P. gagudjuensis n. sp. in comparison with those of the other Pectispongilla species are as follows: i) single apical oscular aperture, ii) presence of free gemmules in the hollow internal space of the dry body, iii) megascleres of two types i.e. acanthoxeas and dominant acanthostrongyles, iv) short length of megascleres (ca. half of those of other species), v) largest gemmules of the genus, vi) shorter shafts of gemmuloscleres in the genus (see Annandale 1915 and Penney & Racek 1968). The diagnosis of the genus is here emended adding the presence of spiny strongyles among megascleres.

Genus Pectispongilla Habitat. Lotic , temporary creek. Several dry, scattered small specimens under pebbles, cobbles, and boulders, from 1 to 6 per substratum. Sponges were absent from the surveyed horizontal rocky bed and timbers. Encrusting bryozoans, with statoblasts, on the same substrata but not strictly associated to the sponges, were also collected and preserved together with the sponges.

Geographic distribution. P. gagudjuensis n. sp. is known only from the type locality. The disjunct Oriental, Australasian, and far east Palaearctic biogeographic pattern of Pectispongilla (5 species) seems to indicate Gondwanan origins and is restricted to the south-western Indian sub-region and Australia with an enclave in Korea and Japan ( Annandale 1911, 1915; Penney & Racek 1968; Racek 1969; Manconi & Pronzato 2002, 2007, 2015) ( Fig. 9 ). P. botryoides Haswell, 1882 is reported exclusively from Australia ( Tables 1–2). Two species P. aurea Annandale, 1909 and P. stellifera Annandale, 1915 are endemic to restricted areas in the SW-Indian subregion, while P. subspinosa Annandale, 1911 is known from SW-India, Japan, and Korea ( Tables 1–2).

Figures

FIGURE 1. Study area and sampling sites in the Kakadu National Park, Arnhem Land, Northern Territory. (a) record of Radiospongilla cfr. philippinensis Billabong at Mamukala Wetlands 12 ° 38 ’ S 132 ° 35 ’ E, 7 km east of the South Alligator River south off the Arnhem Highway; (b) type locality of Pectispongilla gagudjuensis n. sp., a small unnamed creek along the Kakadu Highway, north of Malabanjbanjdju 12 ° 43 ’ S 132 ° 46 ’ E.

FIGURE 8. Pectispongilla gagudjuensis n. sp. (A) Gemmular outer layer with scantly developed spongin cover; (B) Gemmular outer layer of compact spongin with foramen; (C) Gemmule (cross section); (D) Gemmular theca (cross section); (E) Gemmular foramen; (F) Gemmular surface with emerging botryoidal gemmuloscleres tips; (G) Fibrous spongin network in the pneumatic layer of the gemmular theca; (H) Gemmuloscleres at different phase of growth, from immature with rows of spines (top, left) to variably mature showing growth phases of the botryum up to rounded concavities grouped at spicules tips as perfect botryum.

FIGURE 9. Biogeographic pattern of Pectispongilla restricted to Australia and Indian sub-region with an enclave in Korea and Japan.

Tables

TABLE 4. Genus Pectispongilla. Morphotraits and geographic range of the Australian P. gagudjuensis n. sp. from the Kakadu National Park versus species ascribed to the genus.

	P. aurea	P. stellifera	P. subspinosa	P. botryoides	P. gagudjuensis n. sp.
Megascleres µm	smooth oxeas 270–320 x 13–16	acanthoxeas 270–320 x 13–16	acanthoxeas 270–320 x 13–16	acanthoxeas rarely smooth 200–300 x 8–13	acanthostrongyles 90–168 x 8–13 acanthoxeas 130–205 x 5–12
Microscleres µm	rhomboid acanthoxeas 45–52 x 1.5–2.5 22–24 x 3–3.5	acanthoxeas 52–56 x 2.5–4 Tubercled spherasters 8–13	rhomboid acanthoxeas 45–52 x 1.5–2.5	rhomboid acanthoxeas 30–95 x 2	absent
Gemmuloscleres µm	pseudo-botryoidal (immature?) 31–37 x 2.5–4	pseudo-botryoidal (immature?) 31–37 x 2.5–4	pseudo-botryoidal (immature?) 31–37 x 2.5–4	botryoidal (mature) to pseudo-botryoidal (immature) 30–38 x 2.5–4	botryoidal (mature) to pseudo-botryoidal (immature) 26–46 x 2–3
Gemmules µm (diameter)	190–220	190–220	190–220	150–200	200–350
Geographic range	SW-India	SW-India	SW-India, Japan, Korea	Queensland Australia	Northern Territory Australia
References	Penney & Racek, 1968	Penney & Racek, 1968	Penney & Racek, 1968	Racek, 1969	Present paper