Mycale (Aegogropila) antiae Urgorri & Díaz-Agras 2019, new species

Mycale (Aegogropila) antiae new species

Diagnosis. Mycale (A.) antiae sp. nov. possesses mycalostyles, 3 types of anisochelae: I, II and III, microxeas in dragmata and raphides in trichodragmata. Ectosomal tangential reticulation is triangular or polygonal and coanosomal skeleton of longitudinal axial tracts with feathered fan-like plurispicular bundles.

Type locality. Fornelos (Ría de Ferrol, NW Iberian Peninsula) on rocky bottoms between 17 and 20 m deep (43° 28’ 02’’ N; 008° 18’ 50’’ W). Holotype and Paratype 1: 16/03/2017. Paratypes 2–20: 05/04/2017.

Type material and deposition. Holotype: FoRdeF-00- 160317 (MHN-USC-10109) preserved in 70% ethanol, a piece in 100% ethanol for DNA, 36 preparations of sclerites, tracts and fragments for their study under SEM, five preparations of sclerites for OM and a fragment scanned in the Micro-CT. Dimensions.- Base: 56.2 x 28.1 mm; Height: 45.1 mm; Branch: 149.8 mm.

Paratype 1: FoRdeF-01- 160317 (MHN-USC-10110-01) preserved in 70% etanol, the whole specimen was scanned in the Micro-CT. Dimensions.- Base: 28.4 x 26.4 mm; Height: 22.9 mm; Branch: absent.

Paratype 2: FoRdeF-02- 050417 (MNCN 1.01/1.015.) preserved in 70% ethanol. Dimensions.- Base: 77.7 x 44.5 mm; Height: 34.3 mm; Branch: absent.

Paratype 3: FoRdeF-03- 050417 (MNCN 1.01/1.019.) preserved in 70% ethanol. Dimensions.- Base: 65.2 x 42.4 mm; Height: 69.5 mm; Branch: 105.8 mm.

Paratype 4: FoRdeF-04- 050417 (MNHN-IP-2015-1411) preserved in 70% ethanol. Dimensions.- Base: 43.5 x 38.5 mm; Height: 20.3 mm; Branch: 98.9 mm.

Paratype 5: FoRdeF-05- 050417 (ZSM 20181411) preserved in 70% ethanol. Dimensions.- Base: 31.6 x 29.7 mm; Height: 18.5 mm; Branch: absent.

Paratype 6: FoRdeF-06- 050417 (MHN-USC-10110-06) preserved in 70% ethanol. Dimensions.- Base: 48.1 x 34.4 mm; Height: 42.1 mm; Branch: 71.8 mm.

Paratype 7: FoRdeF-07- 050417 (MHN-USC-10110-07) preserved in 70% ethanol. Dimensions.- Base: 54.2 x 32.7 mm; Height: 43.8 mm; Branch: 93.0 mm.

Paratype 8: FoRdeF-08- 050417 (MHN-USC-10110-08) preserved in 70% ethanol. Dimensions.- Base: 54.8 x 26.5 mm; Height: 37.1 mm; Branch: 62.2 mm.

Paratype 9: FoRdeF-09- 050417 (MHN-USC-10110-09) preserved in 70% etanol, a branch end scanned in the Micro-CT. Dimensions.- Bases: 51.4 x 36.7 mm and 33.3 x 29.4 mm; Height: 40.1 mm; Branch: 109.6 mm.

Paratype 10: FoRdeF-10- 050417 (MHN-USC-10110-10) preserved in 70% ethanol. Dimensions.- Base: 53.6 x 17.4 mm; Height: 35.2 mm; Branch: 50.4 mm.

Paratype 11: FoRdeF-11- 050417 (MHN-USC-10110-11) preserved in 70% ethanol. Dimensions.- Base: 36.2 x 22.1 mm; Height: 21.5 mm; Branch: 186.6 mm.

Paratype 12: FoRdeF-12- 050417 (MHN-USC-10110-12) preserved in 70% ethanol. Dimensions.- Bases: 20.3 x 16.3 mm and 43.5 x 26.2 mm; Height: 45.1 mm; Branch: 40.2 mm.

Paratype 13: FoRdeF-13- 050417 (MHN-USC-10110-13) preserved in 70% ethanol. Dimensions.- Bases: 85.7 x 34.3 mm and 49.1 x 32.7 mm; Height: 50.8 mm; Branch: 128.9 mm.

Paratype 14: FoRdeF-14- 050417 (MHN-USC-10110-14) preserved in 70% ethanol. Dimensions.- Base: 46.7 x 31.6 mm; Height: 36.7 mm; Branch: 50.2 mm.

Paratype 15: FoRdeF-15- 050417 (MHN-USC-10110-15) preserved in 70% ethanol. Dimensions.- Base: 52.1 x 35.7 mm; Height: 33.6 mm; Branch: 52.4 mm.

Paratype 16: FoRdeF-16- 050417 (MHN-USC-10110-16) preserved in 70% ethanol. Dimensions.- Base: 55.2 x 33.6 mm; Height: 35.9 mm; Branch: 44.8 mm.

Paratype 17: FoRdeF-17- 050417 (MHN-USC-10110-17) preserved in 70% ethanol. Dimensions.- Base: 44.3 x 31.2 mm; Height: 29.5 mm; Branch: 22.7 mm.

Paratype 18: FoRdeF-18- 050417 (MHN-USC-10110-18) preserved in 70% ethanol. Dimensions.- Bases: 54.2 x 28.6 mm and 34.1 x 28.6 mm; Height: 51.6 mm; Branch: 47.9 mm.

Paratype 19: FoRdeF-19- 050417 (MHN-USC-10110-19) preserved in 70% ethanol. Dimensions.- Bases: 27.2 x 14.3 mm and 20.3 x 13.2 mm; Height: 40.5 mm; Branch: 47.4 mm.

Paratype 20: FoRdeF-20- 050417 (MHN-USC-10110-20) preserved in 70% ethanol, a piece in 100% ethanol for DNA. Dimensions. Base: 24.8 x 19.1 mm; Height: 39.1 mm; Branch: 37.1 mm.

A microscopic preparation was made of Paratypes 1, 4, 5, 6, 8, 9 to measure the spicules at SEM, and of each of the 20 Paratypes a microscopic preparation was made for their study and dimensions under OM.

The Holotype, the Paratypes 1, 6–20 and all microscopic preparations for SEM and OM have been deposited at the Museo de Historia Natural of the Universidade de Santiago de Compostela, Galicia, Spain (MHN-USC). Paratypes 2 and 3 has been deposited at the Museo Nacional de Ciencias Naturales, Madrid, Spain (MNCN), Paratype 4 at the Museum National d'Histoire naturelle, Paris, France (MNHN) and Paratype 5 at the Zoologische Staatssammlung München, Germany (ZSM).

Derivatio nominis. The species is dedicated to Antía Urgorri, daughter of the first author who recently became mother of a baby girl called Adriana.

Description. Habitus . The general macroscopic appearance is apricot-coloured, slightly orange or yellowish, 215 Séguy (1936) (R: 255, G: 195, B: 76), with multiple small sulphur yellow spots, 286 Séguy (1936) (R: 235, G: 236, B: 119), ranging from 0.2 to 4.0 mm and scattered over the entire surface of the sponge, except around the oscula (Figs. 2 A–E, G, J). After fixation in 70% ethanol, the general colour turns ash grey, 235 Séguy (1936) (R: 120, G: 107, B: 90), and the yellow spots turn slightly greyish white, 680 Séguy (1936) (R: 231, G: 228, B: 226), (Figs. 2F, H). Mild consistency, barely mucous, resistant but slightly brittle. Smooth, semi-transparent surface, with a dense tangential multispicular reticulation, with inhalant pores (ostia) of variable sizes barely visible in the meshes and with subectosomal canals forming furrows with a diameter between 0.4 and 1.5 mm, running among the yellow sulphur spots and visible under the surface (Figs. 2 G–J). In the specimens fixed in 70% ethanol, the subectosomal canals depress, reinforcing their visibility (Fig. 2H).

The general structure of the sponge consists of a massive base from which one or several long digitiform processes, more or less branched or even anastomosing emerge, reaching a maximum height of about 69.5 mm in the type series. The massive base is firmly attached to the rocky substratum, but the sponge grows on or around structures of other species or inert objects (Figs. 2B, C, D, E). At first sight the studied specimens have been observed growing around the base of the gorgonia L. lusitanica, on the conical papillae of the sponge C. penicillus, on the ascidian Stolonica socialis Hartmeyer, 1903, on the hydrozoan Sertularella gayi (Lamouroux, 1821), on the tube of the polychaete Spiochaetopterus sp., on the arborescent bryozoa Omalosecosa ramulosa (Linnaeus, 1767) and Buskea dichotoma (Hincks, 1862) and around fishing lines. By means of the Micro-CT it was observed that Paratype 1 grew around two tubes of the polychaete Sabellaria alcocki Gravier, 1906, on the calcareous shells of the cirripede Verruca stroemia (Müller, 1776) and the shell of the bivalve Hiatella arctica (Linnaeus, 1767) (Figs. 8E, G).

The simplest form of M. antiae sp. nov. is represented by two specimens (Paratypes 1 and 5) which show only a massive base more or less irregularly conical, with no ramifications and ending in a single large osculum in the apex (Fig. 2A). Paratype 2 shows an extensive base that gathers several conical bases growing around the papillae of C. penicillus, some of which are fully covered whereas others are only partially covered. In this case, the osculum is also located apically next to the free region of the papilla (Fig. 2B). The rest of type series of M. antiae sp. nov. comprise larger specimens with one or several joined massive bases, of conical and cylindrical shape more or less irregular and vertically more elongated, whose height depends on the surrounding structure, being the highest ones those growing on the gorgonia L. lusitanica or the papillae of C. penicillus (Figs. 2 C–E). However, it can be said that most specimens are lower than the diameter of the base seated on the substratum. Almost all specimens present one or several long digitiform branches, which mostly arise from the apical area near the osculum and a few from the basal area. The short branches stand erect vertically, horizontally or obliquely upwards, but the long branches, which are larger, end resting on the substratum, except when there are erect elements to grasp on (gorgonians) (Fig. 2 C–E). Almost all branches bifurcate or trifurcate at their ends. Larger branches can ramify again and occasionally form lunula-like anastomoses. Paratypes 9, 12, 13, 18 and 19 have two separate bases which are connected at the top by one or two branches (Figs. 2 C–D). The size of the sponge ranges from the smallest with a base of 28.4 x 26.4 mm and 22.9 mm in height, to the largest with a base of 65.2 x 42.4 mm and 69.5 mm in height.

In addition to the single apical osculum of the massive bases (Fig. 2A), the longest and largest branches have one or two oscula that are well separated in the upper region (Figs. 2 C–D): very large oscula, between 2.5 and 6.7 mm, with an elevated rim membranous and depigmented; the final openings of the subectosomal exhalant canals can be clearly seen in situ. When touched in vivo in the laboratory, they close like a sphincter, leaving the rims wrinkled, whereas in the specimens fixed in 70% ethanol they close in a conical shape, leaving the mycalostyles that support the membranous rim clearly visible (Fig. 2F).

Spicules. The distribution of the spicule sizes of the Holotype and Paratypes 1–20 are listed in Tables 2 and 3 and Fig. 7.

Megascleres: Mycalostyles of a single category are the only megascleres (Fig. 3) which are long and smooth subtylostyles, with an average length of 342.8 µm; those fully developed range between 300–400 µm (Figs. 3 A–D and Fig. 7A). Mycalostyles of less than 300 µm in length also appear with moderate frequency. The grainy appearance of their pointed ends (Figs. 3 E–F) may indicate they are still developing. All mycalostyles are fusiform, slightly curved, with one acerate pointed end and the other end, the head, with a slightly globular dilatation, whose shape varies according to the length of the spicule, from very oblong in the small ones to oval in the large ones (Figs. 3 G–N). When the shaft is larger than 3 µm, it is wider than the head; however, when it is inferior to 3 µm, the head is wider (Fig. 7C). The longer spicules are not necessarily the wider ones (Figs. 3 A–B). Sometimes some deformed heads show lateral expansion (Figs. 3 O–R) and are the only ones, wider than 3 µm, where the width of the head is greater than or equal to the shaft (Fig. 7C, see arrows).

Microscleres: Three types of anisochelae: I, II and III, raphides in trichodragmata and microxeas in dragmata.

Anisochelae I: It is the largest and most abundant anisochela in the sponge, with an average length of 46.0 µm, ranging from 38.7 µm in the shortest to 54.3 µm in the longest, although most (50%) range between 44–47 µm (Fig. 7B and Table 2). In a large 51.2 µm long spicule, the head occupies 55.5% of the total length, the shaft 28.9% and the foot 15.6% (Fig. 4Y). Strong shaft of oval section, rectilinear in lateral view and with slightly widened ends in front view, slightly wider in its connection with the lateral alae of the foot than with those of the head (Figs. 4 A–D, Y). The shaft extends in the head at an angle of 164°–166° (Figs. 4E). The head is palmate, robust, deltoid-shaped. The larger the spicule is, the more rounded the vertices, the broader the base and the less accuminated the apex (Figs. 4 A–D). Lateral alae of the head are totally fused to the shaft. Basal portion of the lateral alae project slightly backwards, which causes two small depressions on the sides of the shaft continuation into the head, forming a soft and barely noticeable medial prominence (Fig. 4F). The free parts of the alae are arcuate forwards and show slightly curved margins. Symmetrical frontal ala, are ovate and a third narrower (66%) than the lateral alae as a whole, with the margins arcuate inwards, especially in the lower 2/3, but less arcuate than the lateral alae. The frontal ala forms an angle between 35.5° and 45.5° with the axis of the head shaft; both are internally joined by a narrow buttress, with the lower free margin arched. The buttress joins the shaft of the head at the upper third of the length and joins the frontal ala at the 2/3 of its upper length, resulting in a soft depression in the medial exterior of the frontal ala (Figs. 4E, F, Y, 6F).

The foot is much shorter than the head, with a short shaft of 8.0 µm (Fig. 4Y) slightly deviated from the shaft axis at an angle of 165°–170° only perceptible when the spicula is seen sideways (Figs. 4E, 6F). In relation to the longitudinal axis of the shaft of the spicula, the antero-posterior axis of the foot set is slightly inclined forwards forming an angle of approximately 118°–121° (Figs. 4E, F, 6F). The lateral alae of the foot are curved forwards, forming the set of the two alae with their axis, a semicircular rectangle of blunt vertices, with the basal margin thickened and the upper free margin thinned. Frontal ala of the foot curved backwards, also forming a rectangular semicircle but higher, with blunt vertices, thickened and arched basal margin and thinned and rectilinear or slightly curved upper margin (Figs. 4 A–F, 6F). The frontal ala of the foot is slightly inclined forwards so that the lateral and frontal alae margins, which are very close (Figs. 4E, Z, 6F), are farther apart superiorly (1.5–2 µm) than inferiorly (0.4–0.5 µm). The central axis of the lateral alae and the frontal ala of the foot are internally joined by a buttress of oblong section, inferiorly rectilinear, almost at the margin of the alae and arched at the upper third of the height of the foot in its middle region (Figs. 4Z, 6F). In the not completely formed spicules (Fig. 4D) the alae of the head and foot are less curved, the frontal ala of the head is accuminated and the frontal ala of the foot shows a minute protuberance.

Palmate anisochelae I are organized in the subectosome in rosettes (Fig. 6F), arranged radially under the nodes of reticulation, in the divergent plurispicular fan-like bundles and sometimes around one or two mycalostyles (Figs. 8 B–J). Anisochelae I are joined together by appositioning of their feet. Eighteen rosettes have been studied, with a diameter between 84.3 and 111.3 µm (Fig. 7H) and the number of anisochelae counted in each rosette varied between 12 and 22 (Table 3). However, taking into account that some anisochelae have become detached in the process of manipulation and mounting and by observing those presenting a more regular set, it can be affirmed that the number of anisochelae per rosette is always higher than 20. Apparently, the arrangement of the anisochelae in the rosettes does not have a specific order. In some rosettes it was observed that several anisochelae had two to four longitudinal folds on the medial external face of the frontal ala of the foot. Rosettes are very frequent in the sponge and in certain areas are very abundant having counted 14, 15 and 17 rosettes per mm 2.

Anisochelae II: It is the middle-sized anisochela and the most scarce in the sponge, with an average length of 23.3 µm, ranging between 19.4 µm the shortest and 27.7 µm the longest, although the majority (75%) ranges between 21–25 µm (Fig. 7D and Table 2). In the fully formed anisochelae II, the head occupies 60% of the total length, the shaft 20% and the foot 20% (Fig. 4 H–N). The shaft is short, strong, oval, rectilinear or slightly curved inwards; frontally with slightly widened ends, slightly wider in its connection with the lateral alae of the foot than with those of the head. The shaft continues straight with the foot and forms an angle of 154°–158° with the head showing a small hump at their connection (Figs. 4 L–M).

Palmate head, from oval to egg-shaped in front view and conical in side view (Figs. 4 H–N). Lateral alae of the head totally fused to the shaft, with the basal portion of the lateral alae projecting slightly backwards and with a barely noticeable medial prominence, corresponding to the head shaft, which reaches almost the spicula apex. Side margins of the lateral alae are almost parallel and strongly curved forwards, whereas the lower margins, which are not curved, form a 120° angle with the shaft. Frontal ala symmetrical, flattened, egg-shaped and barely narrower (15%) than the whole set of lateral alae. Narrow side margins curved inwards with the lower front 1/5 of the ala projecting slightly forwards (Figs. 4 H–N). The frontal ala forms an angle between 28° and 31° with the axis of the head shaft. The ala and the shaft are internally connected by a narrow buttress with a very arched lower free margin, which joins the frontal ala medially like a crest at 4/5 of its length, just as far as the frontal ala is projected forwards, although it has not been possible to observe the connection of the buttress with the head shaft (Figs. 4 H– N).

The foot is much shorter than the head (1/3) and rectilinear with the shaft axis (Figs. 4 L–M). In relation to the longitudinal axis of the spicula shaft, the antero-posterior axis of the foot set is slightly inclined forwards forming an angle of approximately 112°–117°. The lateral alae of the foot are curved forwards, forming the set of the two alae with its axis a rectangular semicircle of blunt vertices. Foot frontal ala with side margins curved backwards, forming a quadrangular arch, but 25% higher than the lateral alae, with the blunt vertices and the upper margin not curved, with a denticular protuberance slightly or not protruding, and the lower margin slightly curved (Figs. 4 H– K). The frontal ala is inclined forwards, so that the side and frontal ala margins have a greater separation above (1 µm) than below (0.25 µm). The central axis of the lateral alae and the frontal ala of the foot are internally joined by a buttress inferiorly rectilinear and blunt and superiorly arched, with a thin margin ascending up the interior middle region of the frontal ala to almost the end of the denticular protuberance (Figs. 4 L–M).

Anisochelae III: It is the smallest anisochela with an average length of 12.7 µm, ranging from 10.1 µm the shortest to 15.7 µm the longest, although the majority (50%) ranges between 12–13 µm (Fig. 7D and Table 2). In anisochelae III, the head occupies 55% of the total length, the shaft 19% and the foot 26% (Figs. 4 O–X). However, this proportionality refers to the lateral alae of the head and foot, since the frontal ala of both have a variable length depending on the size of the denticular protuberance of each one (Figs. 4 O–X). Shaft short, strong, with an apparently flabelate section, slightly curved backwards and frontally of the same width along its entire length. In side view, the shaft is continued with the foot and the head, whose set forms laterally a circular segment at an angle of 75° (Figs. 4 S–T) at the outer margin of the shaft. Head palmate, frontally oblong and hood-shaped in side view (Figs. 4 O–X). Lateral alae of the head totally fused to the outer margins of the shaft. Shaft interiorly protruding in ¼ of the basal length (Figs. 4R, X). Externally, it shows a longitudinal medial crest as far as almost the spicula apex, forming an apical inflection in the curvature of the circular segment of the shaft, head and foot set (Fig. 4 T– U). Superior margin of the semicircular lateral alae and side margins are obtuse and slightly curved forwards.

Frontal ala of the head is symmetrical, oblong with the semicircular upper margin and the lower margin with a medial denticular protuberance of variable length (Figs. 4 O–U). Frontal ala as wide and long as the lateral alae set, not including the lower denticular protuberance. Side margins of the frontal ala are obtuse (Fig. 4R), slightly curved inwards in the obtuse region. The margins of the upper halves of the lateral and frontal alae are connected, except for a short inferior section, the next to the vertex of the obtuse angle, which is barely separated by 0.3–0.7 µm (Figs. 4 R–T). From the vertex of the obtuse angle, the margins of the frontal ala diverge from the lower half of the lateral alae, forming an angle of 94°–97°. The frontal ala presents externally a medial crest, similar to that of the lateral alae and also with similar apical inflection. However, it is shorter inferiorly where the margin projects forming the denticular protuberance (Fig. 4P) which varies in length from one spicula to another (0.4–1.4 µm), from a simple blunt tip to a digitiform prominence (Figs. 4 O–U). Laterally, the head forms an angle of 40° to 45° between the frontal and lateral alae which are internally connected by a narrow and short buttress with an arched lower free margin (Fig. 4X).

The foot is shorter than half the length of the head and shows a continuous curvature with the shaft axis (Figs. 4 S–T). In relation to the longitudinal axis of the spicula shaft, the antero-posterior axis of the foot set is slightly inclined forwards forming an angle of approximately 115°–118° (Figs. 4 S–T). The lateral alae of the foot are very curved forwards, forming a flabelled set with the side and inferior margins forming a regular curve, whereas the upper margin is strongly inclined until its upper connection with the shaft (Figs. 4 O–X).

Frontal ala of the foot rounded, with the side margins curved backwards and topped with a medial denticular protuberance of variable length (0.25–1.1 µm) from a small mamelon to a digitiform prominence, which gives the whole set a racket shape (Figs. 4 O–X). Frontal ala of the foot tilted forward, so that the lateral and frontal alae margins are proportionally farther apart (less distance 0.20–0.45 µm) than in anisochelae I and II. The connecting shaft of the lateral alae of the foot protrudes inwards in ¼ of the upper length (Figs. 4 P–R). The buttress starts a little later and connects to the interior of the frontal ala of the foot. This buttress is straight, wide, with blunt margins in its lower region and arranged at the same level as the lateral and frontal alae, whereas above it is narrow, arched and ascending to the base of the denticular protuberance (Figs. 4 R–W).

There is an approximate proportionality between the average length of the three anisochelae; thus, anisochela I (x̄: 46 µm) has twice the average length of anisochela II (x̄: 23.3 µm) and this doubles the average length of anisochela III (x̄: 12.7 µm). However, this proportion does not exist in relation to width; although anisochela I (x̄: 19.9 µm) is four times wider than anisochela III (x̄: 5.1 µm), anisochelae II (x̄: 8.5 µm) does not have the same correlation, as it is proportionally narrower than anisochelae I and III (Fig. 7B, D and Table 2). No rosettes of anisochelae II and anisochelae III have been observed; these always appear scattered throughout the sponge, both in the coanosome and in the subectosome.

Raphides in Trichodragmata: Raphides are the most abundant spicules in the sponge, with an average length of 39.4 µm, ranging between 31.4 µm the shortest and 45.7 µm the longest, although the majority (75%) ranges between 36–43 µm (Fig. 7E and Table 2). Very thin with an average diameter of 0.34 µm, varying from 0.30 µm to 0.48 µm and progressively reducing this width at each end by 20% of the raphide length. Not rectilinear longitudinally, as they show the three-dimensional shape of a two-wave curve with very small amplitude of oscillation. Each end of the raphide ends in a fine harpoon, with an average length of 0.7 µm (55%), ranging from 0.5 to 0.9 µm, and with a single spine, always on the convex side of each wave, with a length of 0.1 µm (Figs. 5A, B, E, F). Raphides are very flexible; when scattered on a slide they show strong curvatures without cracking or breaking. Some are held together in the shape of a wavy band (Fig. 6A, see arrows).

Raphides are always grouped in trichodragmata, they are never loose in the sponge. Trichodragmata are fusiform, with an average length of 41.3 µm, ranging from 34.3 to 48.4 µm. However, the majority (70%) ranges from 38 to 44 µm, with an average diameter width of 5.4 µm in 50% of their average length and with both ends pointed (Fig. 7E and Table 2). Raphides are always organized in packages, closely joined in bundles which keep their undulating shape. However, they show different lengths within the same trichodragma, being the shortest the external ones and the longest the central ones, which determines the pointed shape of each end of the trichodragma which looks fully bristled with the spines of the harpoons always directed towards the exterior (Figs. 5 C–D). Raphides have been counted in six scattered trichodragmata whose number varies between 94 and 120. Trichodragmata are located exclusively in the yellow sulphur spots under the subectosome on the entire surface of the sponge, where they are accumulated in a very high number, i.e. the yellow spots are clusters of trichodragmata (Fig. 6B). When the spots are cut or broken, the trichodragmata spill out in live specimens as if they were a fluid. If a small fragment of the live sponge is placed between the slide and the slide cover in seawater, and pressed lightly, it can be observed under OM that the entire surface of the slide cover area is filled with trichodragmata. Clustered trichodragmata in formation have also been observed around the yellow spots (Figs. 5S, 6G)

Microxeas in dragmata: Microxeas are the least abundant spicules in the sponge, with an average length of 11.7 µm, measuring the shortest 1.8 µm and the longest 26.7 µm, although most (56%) vary between 10–16 µm (Fig. 7F and Table 2). They are rigid, rectilinear, fusiform and pointed at both ends, with an average diameter of 0.5 µm, ranging from 0.2 µm to 0.7 µm. 75% show a width of 0.5–0.6 µm (Figs. 5 G–P).

Microxeas are always grouped in dragmata and thus called microxeadragmata; they are never loose in the sponge. Microxeadragmata are formed by microxeas in parallel packages of bundles being the longest those of the centre and the smallest those of the periphery (Figs. 6 C–E). Although 350 microxeas of the Holotype and 190 of the Paratypes have been measured at SEM, only 15 microxeadragmata were observed at SEM, treating small fragments of the coanosome with 5% KOH directly on the slide to prevent the clustered particles from scattering. It has not been possible to verify a specific location of the microxeadragmata in the sponge coanosome, although some have been observed attached or very close to the shaft of the mycalostyles in the coanosome (Fig. 6D).

In the 15 microxeadragmata, the number of visible microxeas that ranged from 40 to 87 (Table 3) has been counted, recording the length of the longest and shortest microxeadragmata (Fig. 7G). Although the number of microxeas per microxeadragmata is not significant because only visible microxeas can be counted, there is a relationship between the length of the largest and smallest microxea, since in 75% the largest microxea is 1.5x to 2x the length of the smallest one (e. g. 5.9–11.0 µm and 11.2–17.3 µm). An oval formation attached to the shaft of a mycalostyle, which may correspond to microxeadragmata in formation, has been observed twice (Fig. 5T).

Skeleton: The ectosomal skeleton consists of interwoven mycalostyles in bundles forming a triangular or polygonal tangential reticulation and the coanosomal skeleton consists of longitudinal axial tracts, with fan-like plurispicular feathery bundles, perpendicular to the surface of the sponge. The tangential reticulation of the ectosome is formed by bundles of uni or pauci-spicular mycalostyles, forming a mesh of triangular or polygonal spaces (Figs. 2J, 8A, 9A). The paucispicular bundles are formed by 3 to 8 mycalostyles (width: 26.4–54.5 µm) which tend to show a longitudinal interwoven arrangement delimiting elongated rhomboidal areas whose longest axis is 458.7–732.8 µm and shortest axis is 129.5–327.8 µm (Figs. 8A). The rhomboidal areas are crossed by one or two mycalostyles which, when arranged more or less transversally, subdivide them into smaller triangular areas and to a lesser extent quadrangular or pentagonal areas of 35–230 µm with a larger axis. Thus, the ectosome acquires the characteristic tangential reticulation of the subgenus Aegogropila, which is perceptible almost at first sight. The ectosomal membrane cannot be easily separated and the ends of the mycalostyles never portrude from it. The subectosomal canals, trichodragmata clusters and rosettes of anisochelae I located under the reticulation nodes, around the shaft of 1 or 2 mycalostyles or in the divergent plurispicular fan-like bundles are located under the membrane. No rosettes have been observed under the ectosomal membrane in the yellow areas of trichodragmata clusters. The inhalant pores (ostia) are found in the membrane of the areas of the ectosome reticulum. Pores round, circular, oval or pyriform; 226 pores have been measured ranging their largest diameter between 10.2 and 79.0 µm, although 70% of the pores diameter vary between 30 and 60 µm. Oscula are very large (2.5–6.7 mm) and scarce. Their membranous margin is supported by numerous mycalostyles arranged radially with the sharp end pointing towards the margin of the osculum (Fig. 8H).

M. (A.) antiae sp. nov. Mycalostyles I Anisochelae II III Raphides Trichodragmata Microxea Holotype 185.7–342.8–403.4 x 38.7–46.0–54.3 x 19.4–23.3–27.7 x 10.1–12.7–15.7 x 31.4–39.4–45.7 x 34.3–41.3–48.4 x 1.8–11.7–26.7 x hw: 1.1–5.5–8.2 x w: 15.5–19.9–23.0 w: 6.7–8.5–11.3 w: 3.8–5.1–6.8 w: 0.3–0.34–0.48 w: 4.5–5.4–7.8 w: 0.2–0.5–0.7 sw: 0.8–6.5–10.3 n= 150 n= 50 n= 50 n= 120 n= 60 n= 350 n= 220; 60; 60 Paratype 1 317.7–344.4–385.8 x 43.3–48.3–51.6 x 21.5–22.8–25.8 x 11.8–13.0–15.4 34.3–39.8–45.5 37.1–42.4–49.2 x 3.5–4.4–5.8 hw: 5.9–7.0–8.3 x w: 16.9–20.0–22.9 w: 6.8–8.5–10.4 w: 5.0–6.9–8.6 sw: 7.3–8.4–10.0 n= 20 n= 20 n= 20 n= 20 n= 20 n= 20 n= 20

Paratype 1 330.0–365.5–405.0 x Paratype 2 315.0–356.0–395.0 x Paratype 3 330.0–375.3–400.0 x Paratype 4 340.0–363.3–385.0 x Mycalostyles hw: 5.0–6.8–11.3 x Mycalostyles hw: 6.3–7.7–11.3 x Mycalostyles hw: 3.8–7.2–10.0 x Mycalostyles hw: 5.0–7.9–11.3 x

n= 20 sw: 7.5–8.4– 10.0 n = 20 sw: 7.5–9.4– 12.5 n = 20 sw: 3.8–8.0– 11.3 n = 20 sw: 7.5–9.1–12.5

Paratype 5 315.0–358.5–385.0 x Paratype 6 310.0–356.5–395.0 x Paratype 7 305.0–365.5–390.0 x Paratype 8 330.0–358.8–385.0 x Mycalostyles hw: 5.0–7.9–12.5 x Mycalostyles hw: 5.0–7.1–8.8 x Mycalostyles hw: 6.3–7.4–8.8 x Mycalostyles hw: 6.3–7.4–11.3 x

n= 20 sw: 7.5–9.6– 12.5 n = 20 sw: 6.3–8.8– 10.0 n = 20 sw: 7.5–8.6– 10.0 n = 20 sw: 7.5–8.5–11.3

Paratype 9 310.0–350.8–400.0 x Paratype 10 330.0–359.5–380.0 x Paratype 11 315.0–348.3–390.0 x Paratype 12 320.0–350.3–390.0 x Mycalostyles hw: 5.0–7.0–8.8 x Mycalostyles hw: 6.3–7.8–11.3 x Mycalostyles hw: 3.8–6.4–8.8 x Mycalostyles hw: 5.0–7.1–8.8 x

n= 20 sw: 7.5–8.5– 10.0 n = 20 sw: 7.5–8.8– 11.3 n = 20 sw: 6.3–7.4– 10.0 n = 20 sw: 5.0–7.6–10.0

Paratype 13 325.0–364.0–400.0 x Paratype 14 310.0–358.3–400.0 x Paratype 15 305.0–355.5–385.0 x Paratype 16 325.0–353.8–395.0 x Mycalostyles hw: 6.3–7.6–10.0 x Mycalostyles hw: 5.0–7.6–8.8 x Mycalostyles hw: 5.0–7.0–10.0 x Mycalostyles hw: 5.0–7.1–10.0 x

n= 20 sw: 6.3–8.4– 11.3 n = 20 sw: 7.5–8.5– 10.0 n = 20 sw: 5.0–8.0– 10.0 n = 20 sw: 6.3–8.0–11.3

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The irregular choanosomal skeleton consists of ascending tracts of multispicular fibres of mycalostyles and secondary extensions of feathery tracts of mycalostyles that diverge near the surface and support the ectosomal skeleton without going through it. The tracts of multispicular fibres that make up the skeleton of the sponge are exclusively made up of interwoven mycalostyles, mostly arranged in the same direction, and bound with spongin (Fig. 8C, D, F, J). They have a rounded section and a very variable calibre, measuring the largest diameter up to 394.9 µm and the thinnest 26.1 µm. The main ascending tracts are those with the largest calibre, greater than 200 µm, and extend sinuously to near the surface of the sponge or near the end of the digitiform branches (Figs. 8 E–F 9G). As the sponge grows in volume, the main tracts branch out into two or more similarly sized ascending tracts, which at different heights reinforce the structure by means of cross-connections of medium size between 80 and 200 µm, strengthening these cross-connections with small buttresses (25–80 µm) (Figs. 8C). A complex network of small and médium interconnected tracts also originates from the ascending tracts. Besides forming a complex structure, they delimit spaces through which the system of exhalant and inhalant canals extends (Fig. 8D).

In the digitiform branch of Paratype 9 studied by micro-computed tomography, the presence of main large ascending tracts is observed running through the central area of the branch, close to each other and arranged more or less linearly along the largest transverse axis of the branch (Figs. 9G, H, E). The ascending main tracts also originate a complex web of smaller tracts that radially diverge to the surface (Figs. 9J, K). In the transverse sections, it can be seen how they delimit and support the exhalant and inhalant canals (Figs. 9B, C, D). When comparing the skeletal arrangement of Fig. 9E and the disposition of the canals of Fig. 9F at the end of the branch, it can be seen that the spaces are coincident. The large exhalant canals are the most superficial (Figs. 9C, D, J, K).

Around the ectosome, all tracts, including the main ascending ones, open perpendicularly to the surface of the sponge in divergent plurispicular fan-like bundles, forming a feathery skeleton that supports the ectosome, and delimits the subectosomal canals (Figs. 8J, 9 L–M). This choanosomal feathery skeleton also supports trichodragmata clusters under the ectosome (Fig. 9N, see arrow). In the uprooted specimens observed in vivo in the laboratory and especially in those fixed in 70% ethanol, the surface is conulous at the points corresponding to the end of the main ascending tracts (Fig. 8E). In the ectosome and especially in the coanosome, small foreign elements were observed, mainly sediment grains (see white dots in Figs. 8E, 9 G–H), frustules of large diatoms and a small bivalve, Musculus discors (Linnaeus, 1767).

DNA sequence data: The cox1 –5’ sequence for specimen Paratype 20 DNA is available under GenBank accession number MK177497.

Habitat and associated fauna: The habitat of Mycale (Aegogropila) antiae sp. nov. is a rocky platform of granodiorites, subject to moderate hydrodynamism, between 17 and 20 m deep, where a forest of the gorgonian Leptogorgia lusitanica (Stiasny, 1937) is located. Due to its proximity to a sandy-muddy sedimentary bottom, the surface of the rock is covered by a light layer of fine sediment. The community under the gorgonian forest is devoid of large algae, but shows a wide diversity of sessile invertebrate species where certain species of sponges are abundant Cliona celata Grant, 1826, Adreus fascicularis (Bowerbank, 1866), Polymastia boletiformis (Lamarck, 1815), Desmacidon fruticosum (Montagu, 1814), Ciocalypta penicillus Bowerbank, 1862 and Haliclona (Haliclona) oculata (Linnaeus, 1759), the cnidaria Dynamena pumila (Linnaeus, 1758), Sertularella gayi (Lamouroux, 1821), Aglaophenia acacia Allman, 1883, Actinothoe sphyrodeta (Gosse, 1858), Epizoanthus arenaceu s (Delle Chiaje, 1823), Caryophyllia smithii Stokes & Broderip, 1828, Eunicella verrucosa (Pallas, 1766) and Alcyonium digitatum Linnaeus, 1758, the bivalve Mimachlamys varia (Linnaeus, 1758), the polychaete Sabellaria alcocki Gravier, 1906 and the ascidian Stolonica socialis Hartmeyer, 1903 and also other species of vagile invertebrates like the molluscs Calliostoma zizyphinum (Linnaeus, 1758), Turritella communis Risso, 1826, Tritia reticulata (Linnaeus, 1758), Trapania tartanella (Ihering, 1886), Cadlina laevis (Linnaeus, 1767) and the echinoderms Marthasterias glacialis (Linnaeus, 1758), Echinus esculentus Linnaeus, 1758 and Holothuria forskali Delle Chiaje, 1823.

In addition to settling and growing on species with hard structures (vide supra in habitus), Mycale (Aegogropila) antiae sp. nov. presents a wide variety of associated flora and fauna. Paratypes 2, 4, 7, 12 and 18 showed as epibionts very small orbicular red algae: Rhodymenia pseudopalmata (Fig. 2B), whose rizoids penetrate the sponge. However, in Galicia it is another species, R. holmesii, the one that preferably lives on Porifera, especially on Cliona celata. As regards the fauna, the most frequent epizoic species are the ophiuroid echinoderm Ophiothrix fragilis (Abildgaard, 1789) which moves around the base and surface of the sponge and the peracarid crustacean Leucothoe spinicarpa (Abildgaard, 1789) which lives in the cavities of the sponge. Both species were present in great abundance in all the specimens of the type series, with 71 and 34 specimens of each one respectively. Leucothoe spinicarpa is an amphipod of cosmopolitan distribution that has already been cited in association with other sponge species, including Mycale (Carmia) microsigmatosa Arndt, 1927, although it was also found associated with other marine animals (Ribeiro et al. 2003).

Three specimens of the nudibranch mollusc Marionia blainvillea (Risso, 1818) were also found to use the cavities at the base of the sponge only as a shelter, since this nudibranch feeds on cnidarians and among them on gorgonians. Also, the presence as epibionts of a specimen of the hermit crab Pagurus bernhardus (Linnaeus, 1758), two specimens of the bivalve Musculus discors (Linnaeus, 1767), the polychaetes Exogone naidina Örsted, 1845, Polydora sp. and Harmothoe sp., several specimens of Gromia spp., a species of a harpacticoid copepod and nine siphonostomatoid copepods of two species of the family Asterocheridae could also be proven. The members of this family are a very wide variety of host taxa but the most frequent are sponges, cnidarians and echinoderms (Boxshall & Halsey 2004).

Distribution: The type locality where Mycale (Aegogropila) antiae sp. nov. was collected is the only known mention of its distribution area. However, taking into account that the authors have been diving in the type locality of Fornelos (Ría de Ferrol) at least 3 or 4 times annually for the last 40 years and that they had never before detected the presence of this species so easily visible in situ, it may be considered as an allochthonous species on the eastern North Atlantic coast, which has been recently introduced into the Ría de Ferrol and consequently, Mycale (Aegogropila) antiae sp. nov. is a species not described in its natural distribution area.

Obviously, we do not know the entry route of Mycale (Aegogropila) antiae sp. nov., but in Galicia there are numerous non-native species introduced into the marine environment, mainly by the import of species for aquaculture, such as associated species, or introduced in ballast water or in the fouling of the ship hulls, given the intense international maritime traffic of the ports of Galicia (Bañón 2012). Likewise, the introduction through dispersion in non-biodegradable objects, as Carlton et al. (2017) found in the Pacific Ocean, should not be ruled out.