Mycale (Aegogropila) prognatha, Van & Aryasari & De, 2021

Van, Rob W. M., Aryasari, Ratih & De, Nicole J., 2021, Mycale species of the tropical Indo-West Pacific (Porifera, Demospongiae, Poecilosclerida), Zootaxa 4912 (1), pp. 1-212 : 20-23

Mycale (Aegogropila) prognatha sp.nov.

Figs 9 a–d, 10a–g

Material examined. Holotype ZMA Por. 15822, Mauritius, Chenal du Trou d’Eau Douce , reef, 20.24°S 57.80°E, depth 8–10 m, coll. J.H. Stock, 7 February 1964 (color violet).

Description. Lobate, massive ( Fig. 9a ), consolidating algae and bryozoans, which provide much of the support. Size of the mass 10 x 5 x 2 cm. Live color cited as violet by its collector, orange beige in alcohol. Surface optically smooth, slightly bumpy, generally lipostomous, but with a few slightly raised oscules. Consistency firm, probably due to the enclosed algae and bryozoans.

Skeleton. The usual ectosomal aegogropila-skeleton ( Fig. 9b ) of intercrossing spicule tracts is present. Tracts are 50–70 µm in diameter (8–10 spicules), forming meshes of 300–600 µm in size. Rosettes of anisochelae I are common in the ectosome and are 60–110 µm in diameter. Few subectosomal spicule tracts are present, only some bundles supporting the ectosomal skeleton. The choanosomal skeleton is largely replaced by algal thallus threads ( Fig. 9c ), with many loose megascleres and microscleres strewn among them.

Spicules ( Figs 9d , 10 a–g). Mycalostyles, anisochelae in three categories, sigmas in two categories, toxas and toxodragmas.

Mycalostyles ( Figs 10a,a 1 ), similar to those of M.(Ae.) orientalis : moderately robust, with faint constriction below an elongated, barely swollen head, 318– 342.9 –381 x 8– 10.3 – 11 µm.

Anisoschelae I ( Fig. 10b ), rather robust, alae well-developed, and the shaft straight and free for about 45% of the spicule length, with outwardly curved upper median alae, 49– 52.3 – 57 µm.

Anisochelae II ( Figs 10c ), differentiated in two overlapping types, one approximately similar to those of M. (Ae.) orientalis with narrow shape and broad median alae, the other more robust, with upper median ala rather narrow and the upper lateral alae broadly developed, with lower median ala broad and with slightly incurved rim, the two types in overlapping sizes, 23– 26.4 – 30 µm .

Anisochelae III ( Figs 10d,d 1 ), characteristically with upper median ala overlapping the lower median ala, and tapering proximally towards a pointed ending, lower median ala with median protrusion; free shaft approximately 1/3 of the length of the spicule, size rather uniform, 9– 12.6 – 14 µm.

Sigmas I ( Fig.10e ), robust, rather narrow, with strongly curved apices, 96– 107.1 – 111 µm, up to 10 µm in thickness.

Sigmas II ( Figs 10f ), thin, rather evenly curved, in a large size range but not clearly divisible in size categories, 15– 24.3 – 36 µm.

Toxas ( Figs 10g,g 1 ), shallow-curved, in a large size range but not clearly divisible in separate sizes, smaller toxas partially arranged in toxodragmas ( Figs 10g 1 ), tending to be diamond-shaped (‘double’ toxodragmas), sizes 36– 64.9 – 132 µm, the larger sizes have a thickness up to 2 µm.

Etymology. The species name is an adjective derived from ‘prognath’, a medical term referring to a protruding jaw condition in humans. We consider this an apt description of the condition found in the anisochelae III.

Distribution and ecology. Mauritius, shallow reef locality.

Remarks. The specimen resembles specimens assigned here to M. (Ae) orientalis , but it differs substantially in (1) having two shapes of anisochelae II, (2) prognath anisochelae III, and (3) toxodragmas. The skeleton is also peculiar in being fortified by algal thallus. Live color is violet in stead of the orange color in M. (Ae.) orientalis . There is resemblance in anisochelae II between the two Oman specimens of M. (Ae.) orientalis , which are also relatively robust, perhaps evidence of the existence of a distinct Indian Ocean population which could include the present specimen. However, additional features such as the toxodragmas, and especially the peculiar shape of anisochelae III, are absent in these specimens.

Mycale aegagropila sensu Wilson 1925 , here considered to belong to M. (Ae.) orientalis , was mentioned to possess a few toxodragmas, a further indication that our new species is close to M. (Ae.) orientalis .

Prognath anisochelae III remind of the condition in the Caribbean species Mycale (M.) arndti Van Soest, 1984 as demonstrated in Hajdu & R̹tzler’s (1998) fig. 3g.

Figures

FIGURE 1. A. Numbers of available specimens for the present study from the collections of the Naturalis Biodiversity Center distributed over Indo-West Pacific Marine Ecoregions (MEOWS, cf. Spalding et al. 2007). B. Ditto for type specimens and additional specimens from other institutions consulted for this study.

FIGURE 9. Mycale (Aegogropila) prognatha sp.nov., holotype ZMA Por. 15822 from Mauritius, a, massively lobate habitus encrusting coral debris (scale bar = 1 cm), b, light microscopical view of ectosomal skeleton including rosettes of anisochelae I, c, light microscopical view of cross section of choanosomal skeleton and spicules showing strong presence of algal tissue, d, light microscopical view of spicules, including anisochela II, numerous prognath anisochelae III, numerous sigmas II of smaller and larger sizes, and toxodragma.

FIGURE 10. Mycale (Aegogropila) prognatha sp.nov., holotype ZMA Por. 15822 from Mauritius, SEM images of spicules, a, mycalostyle, a1, details of mycalostyle, b, anisochela I in front view, c, anisochelae II showing size range of larger robust and smaller spicules, d, ‘prognath’ anisochela III (all anisochelae in same magnification), d1, a range of shapes found in the ‘prognath’ anisochelae III, e, sigma I, f, size range of sigma II, g, size range of toxas, g1, size and shape range of toxodragmas.