Sponges (Porifera) are considered to be one of the most primitive forms of
animals. They lack differentiated cells, and can reform if disassociated
by (for example) shoving them through a sieve. On the other hand they
cannot be considered colonies of single-celled organisms, as they have
definite structures, bodies with more-or-less set shapes consisting of
networks of pores and channels through which water is pumped; the
individual cells feeding separately by filtering food from the water in
these channels. They are the only extant group of animals with a fossil
record that extends significantly into the Precambrian. Calcareous Sponges, Calcarea, are Sponges that have skeletons composed of calcium carbonate.
In a paper published in the journal ZooKeys on 22 January 2020, Yan-Ling Chu, Lin Gong, and Xin-Zheng Li, of the Institute of Oceanology, University, and Center for Ocean Mega-Science of the Chinese Academy of Sciences, and Laboratory for Marine Biology and Biotechnology at the Pilot National Laboratory for Marine Science and Technology, describe a new species of Calcareous Sponge from Shandong Province, China.
The family Leucosoleniidae is characterised by a branched and rarely anastomosed cormus and asconoid aquiferous system (branching and rarely connected tube-shaped body, whith pores covering the surface through which wated is taken in, then expenlled through the central tube vents) ; there is neither a common cortex nor a delimited inhalant or exhalant aquiferous system. The family includes three genera: Ascyssa, Ascute, and Leucosolenia. These can be easily distinguished by their skeletons: the skeleton of Ascyssa contains only diactines (needle-shaped skeletal elements with two points); the skeleton of Ascute exhibits giant longitudinal diactines forming a continuous layer on the external surface, and includes triactines and tetractines (three and four pointed skeletal elements); and the skeleton of Leucosolenia lacks any of the obvious characteristics of the other two genera. Instead, the skeleton of Leucosolenia is characterised by being composed of diactines, triactines and/or tetractines, without a reinforced external layer on the tubes.
The genus Leucosolenia comprises 40 living species worldwide, of which only three species, Leucosolenia microspinata, Leucosolenia salpinx, and Leucosolenia parthenopea, were named after 1950; 11 species were described by Ernst Haeckel between 1870 and 1872. The literature of this genus is relatively old, and the descriptions contained therein of the species of Leucosolenia were simple, almost without details and illustrations of the body shapes and spicules. Thus, a taxonomic revision of this genus is very difficult, and to date, no worldwide revision of the genus has been made.
Fifteen known species of Leucosolenia have been recorded from the Pacific. Seven species, Leucosolenia. eleanor, Leucosolenia minuta, Leucosolenia mollis, Leucosolenia pyriformis, Leucosolenia serica, Leucosolenia tenera, and Leucosolenia ventosa, have been reported from the Japanese waters; Sagimi Sea, Wakayama Prefecture, Onagawa Bay, Mie Prefecture, Matsushima Bay, Izushima, and Wagu Miye Prefecture, respectively. Leucosolenia macquariensis was reported from the west coast of Macquarie Island; Leucosolenia. australis was reported from Comau Fjord in Chile; Leucosolenia albatrossi was reported from Copper Island and the Komandorski Islands in the Aleutian Chain; Leucosolenia echinata and Leucosolenia. rosea were reported from New Zealand; Leucosolenia lucasi was reported from Port Phillip Heads, Australia; Leucosolenia nautilia was reported from California; and Leucosolenia feuerlandica was reported from Tierra del Fuego, South America. Thus the majority of the Leucosolenia species reported from the Pacific are found on the coasts of Japans. The specimens from which the new species is described were found in the Yellow Sea, very close to Japan.
Distribution of Leucosolenia (A) location in the Pacific Ocean (B) detail of the localities on the Japanese coast: (1) Komandorski Islands (Leucosolenia albatrossi); (2) Comau Fjord (Leucosolenia australis); (3) Cook Strait, Poverty Bay, Kawakawa (Leucosolenia echinata); (4) Francisco Bay, California; Sukumo ôsima, Kôti Prefecture, Sagimi Sea (Leucosolenia eleanor); (5) Tierra del Fuego (Leucosolenia feuerlandica); (6) Port Phillip Heads, Australia, and New Zealand (Leucosolenia lucasi); (7) Macquarie Island (Leucosolenia macquariensis); (8) Wakayama Prefecture (Leucosolenia minuta); (9) Onagawa Bay (Leucosolenia mollis); (10) Monterey Bay, California (Leucosolenia nautilia); (11) Mie Prefecture (Leucosolenia pyriformis); (12) New Zealand (Leucosolenia rosea); (13) Yodomi, Sagami Sea (Leucosolenia serica); (14) Matsushima Bay, Onagawa Bay, Izushima (Leucosolenia tenera); (15) Wagu Miye Prefecture (Leucosolenia ventosa); (*) Qingdao (new species). Chu et al. (2020).
The new species is described upon the basis of two specimens collected from a scallop-breeding pond on southeastern Shandong Peninsula in 1984 and 1988, and stored in the collection of the Marine Biological Museum of the Institute of Oceanology of the Chinese Academy of Sciences.
For examination of the spicules, a small piece of specimen was cut and placed in a 1.5 mL microcentrifuge tube to which 1000 μL of sodium hypochlorite (bleach) solution was added. The mixture was then vortexed, placed at environmental temperature, and vortexed occasionally during incubation until it was completely lysed. Next, the sample was centrifuged at 8000 rpm for 2 minutes, the supernatant was poured off, 1000 μL of distilled water was added, and the sample was again centrifuged at 8000 rpm for 2 minutes. This procedure was repeated four times, then the spicules were washed three times with 96% ethanol and then the spicules were preserved in one third ethanol solution.
Scanning electron microscopy was performed with a Hitachi S3400N. Preserved spicules for scanning electron microscopy were adhered to stubs with double-sided carbon conductive tape and coverslip. After dehydration, the spicules were coated with gold in a Hitachi MC1000.
Measurements of at least 20 spicules of each type were performed using a Nikon Eclipse Ni optical microscope with a micrometric eyepiece. The length from the tip to the base and the thickness at the base of each actine were measured. Photographs were taken with a Zeiss Stemi 2000-c stereomicroscope and a Nikon Eclipse Ni-U optical microscope equipped with a digital camera to evaluate difference between the length of the unpaired and paired actines of each type of triactine. For comparison with the new species, Chu et al. only selected those species of Leucosolenia reported from the Pacific Ocean.
The new species is named Leucosolenia qingdaoensis, where 'qingdaoensis' means 'from Qingdao', in reference to the city in Shandong where it was discovered. This Sponge is arborescent, consisting of many thin-walled tubes, which are copiously ramified but never anastomosed. The Sponge occurs as growth form. The oscula are terminal on erect tubes. The colour of the Sponge is white after being preserved in alcohol and in vivo. The external walls of the tubes are hairy, with diactines protruding at right or oblique angles from the body; the surface is minutely hispid, and the consistency is soft and fragile. The specimen described measures 21.32 × 3.38 mm (height × width). The wall of the Sponge body is very thin, and there is no fully developed inhalant system, the gap between the skeleton and the cell on the wall arrange evenly; only a small amount of cells is distributed on the thin sponge skeleton, which is a typical asconoid feature. All internal cavities of the Sponge are lined by choanocytes.
Leucosolenia qingdaoensis, (A) holotype, (B) paratype, (C) detail of oscula (stereo microscope), (D) detail of root-like structures (stereo microscope), (E) detail of oscula (optical microscope), (F) detail of rootlike structures (optical microscope); arrowhead pointing at the ostium. Chu et al. (2020).
The skeleton consists of multifarious diactines, sagittal triactines of two types, sagittal tetractines with bent apical actines and triactine-like basal actines; together these form the wall of the ascon-type Sponge body.
In the apical osculum, there are paired actines of triactines and tetractines, some additional tangential diactines, together forming a clear line dividing the apical oscula, and some radial diactines projecting beyond the apical osculum with different length.
In the Sponge body, the triactines and tetractines are regularly arranged, their paired actines are parallel to the apical oscula, and the unpaired actines point downward, with slight folding allowed, but never overlapping; in contrast to the triactines and tetractines, the diactines are arranged more irregularly but generally point downward.
In the root-like structures, the arrangement of triactines and tetractines is the same as that in the body, but the arrangement of diactines is different; most of them tangentially project beyond the surface, which results in the surface having a slightly hispid (bristly) appearance.
By observing the sponge tissue taken from different parts, it is clear that as the diameter of the tubes decreases, the contents of small diactines and small triactines increase. This observation can suggest that in the growth zone spiculogenesis is more intense.
There is only one type of diactine, though the diactines vary in size and shape, their width varies from 24 μm to 61 μm, the length of diactines vary from 43 μm to 421 μm but half of the diactines present a length of 200–300 μm. The shapes of the diactines are straight or slightly curved in different directions. The variation in Leucosolenia is very common and considerable.
Spicules of Leucosolenia qingdaoensis. (A1)–(A3) diactines; (B1) triactines of type 1; (B2) triactines of type 2; (C1)–(C2) tetractines. Chu et al. (2020).
Two types of triactines are present, with actines straight or undulated. Their ends are generally sharp or asymmetrical. The paired actines are slightly curved. Some deformations are present. Type 1 triactines have paired actines longer than unpaired actines: the unpaired actines are 42–105 × 3–5 μm; the paired actines are 63–105 × 3–5 μm. Type 2 triactines have unpaired actines longer than paired ones: unpaired actines are 76–129 × 3–4 μm; paired actines are 60–104 × 3–4 μm.
A relatively small number of tetractines were observed, approximately 10 per 100 spicules, with straight and fusiform actines. The tetractines are similar to triactines but with the addition of apical actines, the apical actines are fairly stout and short, sharply pointed and curved: unpaired actines are 93–119 × 2–5 μm; paired actines are 50–93 × 2–5 μm; apical actines are 11–29 × 2–5 μm.
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