Ernstia pyrum, Sanamyan & Sanamyan & Martynov & Korshunova, 2019

Sanamyan, Karen, Sanamyan, Nadya, Martynov, Alexander & Korshunova, Tatiana, 2019, A new species of Ernstia (Porifera: Calcarea) described from marine aquarium, Zootaxa 4603 (1), pp. 192-200 : 194-198

Ernstia pyrum sp. nov.

( Figures 1–3 , Table 2 )

urn:lsid:zoobank.org:act:1B70AF30-D9DB-42CF-98AE-173D1D0776C4

Material examined. Holotype: ZIN 11879, marine aquarium, on “live stones” imported from Indonesia (more accurate location is not available), 17 January 2019 . Paratypes: ZIN 11880, same data, 1 specimen; ZMMU G-259, same data, 1 specimen ; ZIN 11881, same data, 24 specimens .

Etymology. The specific epithet pyrum (pear in Latin) refers to the shape of most specimens of this sponge.

General morphology. The cormus is yellow, oval, pear-shaped or, occasionally somewhat less regular compact mass made up of tightly anastomosed thin tubuli ( Fig. 1A, B ). It is attached to the substratum by a wider basal part or by a side, usually upright. The consistence is not especially soft, compressible. Overall size is up to 2 cm in its greatest dimension, but usually smaller, most specimens 10–12 mm in height and 5–8 mm in diameter. All tubuli are of about the same diameter (0.2–0.3 mm), no water collecting tubes are recognizable on the surface or in the sections. Usually one terminal osculum is present, up to 6 mm long and 2–3 mm in diameter, rarely several oscular tubes are developed. There is a rather voluminous atrial cavity delimited by clear atrial membrane without choanocytes ( Fig. 1A, C ). No cells with granules are present.

Skeleton. The skeleton has no special organization and is composed of triactines, tetractines and often, but not always, trichoxeas. Trichoxeas are present only on the surface, some of them protrude perpendicularly or obliquely to the surface of the sponge but most are parallel to it ( Fig. 2C ). The walls of the tubuli are built by a few layers of triactines and tetractines. The apical actines of the tetractines protrude into the tubule lumen ( Fig. 2D ). Triactines are the most numerous spicules, the ratio of triactines to tetractines on the surface and internal layers (choanosome) is rather stable and varied from 5:1 to 5.7: 1 in several measured specimens. Tetractines occur in somewhat higher frequency in the wall of the atrial cavity but still are two times less numerous here than the triactines. The size of triactines and tetractines differs in different regions of the sponge: the spicules in the wall of the atrial cavity and, especially, in the oscular membrane and are noticeably larger than the spicules in the other parts of the body.

Spicules ( Table 2 , Fig. 2 ).

Triactines. Equiangular and mostly equiradiate. They possibly may be divided into two categories: the spicules with the short and wide conical actines and sharp tips, and the spicules with the long narrow cylindrical, sometimes slightly undulating actines and usually blunt tips. However there are all transitions between these extremities and we failed to delimit these categories clearly either by size or by the shape ( Fig. 2A ) and measured them together as a single category.

Tetractines. Similar to the triactines and show the same size and shape variations. Apical actine is needle-like, smooth, long (80–120 µm), thin, straight and sharp.

Trichoxeas. Thin, long and straight.

Habitat. Numerous specimens of this species were found on so called “live stones” (lime stones consisting mostly of dead parts of stony corals collected at coral reefs), imported from Indonesia for marine aquarium trade. They rapidly proliferate in the so called “reef aquarium” with stony corals and marine fishes at the conditions required to maintain stony corals: water temperature 25–27ºC, salinity 35‰, low level of inorganic nutrients (concentration of inorganic nitrate is about 2 ppm, inorganic phosphate less than 0.05 ppm). These sponges prefer dim places but may occur on well-lit areas too.

Type locality. Article 76.1.1. of the International Code of Zoological Nomenclature ( ICZN, 1999) says for the species based on the specimens transported by humans: “the type locality is the place from which the name-bearing type [...] began its unnatural journey”. The type locality for Ernstia pyrum sp. nov. is therefore assigned to Indonesia from where the “living stones” with this species were imported .

Remarks. Molecular sequence data render this species as belonging to the genus Ernstia and being closely related to E. citrea Azevedo, Padua, Moraes, Rossi, Muricy & Klautau, 2017 described from Rocas Atoll, Brazil ( Fig. 3 ). Indeed, in life these two species appear to be very similar, both have compact yellow cormus composed of tightly anastomosed tubuli and a long terminal osculum (see Azevedo et al. 2017, Figure 16E). As perceived from the published photographs ( Azevedo et al. 2017, Figures 10A, B and 16E), E. citrea has less tightly anastomosed tubuli forming larger meshes on the surface of the sponge than in E. pyrum sp. nov. The diameter of the tubuli in E. citrea is said to be 3 mm, but according to scale bars on the above mentioned photographs this is an obvious mistype, probably should be 0.3 mm i.e. about the same as in E. pyrum sp. nov. The triactines and tetractines of E. pyrum sp. nov. show significantly greater range of size variations (38–185 µm) than those of E. citrea (67–108 µm). Further, the spicules with long cylindrical actines, occurring in the oscular and atrial wall of E. pyrum sp. nov., are not reported for E. citrea .

Other similar yellow Ernstia species with tightly anastomosed tubuli are E. arabica Voigt, Erpenbeck & Wörheide, 2017 from the Red Sea, E. solaris Azevedo, Padua, Moraes, Rossi, Muricy & Klautau, 2017 from the SW Atlantic off Brazil, and E. klautauae Van Soest & De Voogd, 2015 from Indonesia. According to molecular data they all group together but are less related to E. pyrum sp. nov. than E. citrea ( Fig. 3 ). Morphological differences are as follows: E. solaris has smaller and significantly less variable spicules than E. pyrum sp. nov., triactines and tetractines are in almost the same proportion ( Azevedo et al. 2017); E. arabica and E. klautauae have tri- and tetractines with conical actines, no spicules with long cylindrical actines are mentioned, tetractines either dominate or are in the same proportion as triactines ( Voigt et al. 2017; Van Soest & De Voogd 2015; 2018).

Figures

FIGURE 1. Ernstia pyrum sp. nov. A, holotype sectioned longitudinally, note well developed atrium; B, three paratypes, in live; C, histological section of the atrial wall, note the absence of choanocytes; D, histological section of a tubule lined by choanocytes.

FIGURE 2. Ernstia pyrum sp. nov. A, triactines; B, tetractines; C, surface of the sponge, note numerous trichoxeas; D, inner wall of the atrium, note long apical actines of the tetractines projecting into the lumen of tubuli.

FIGURE 3. Maximum Likelihood tree inferred from the ITS rDNA sequences under the GTR model of Ernstia species (available in GenBank and generated in the present study) and three Ascandra species (as an outgroup). Bootstrap values are indicated.