Leucilla agitata, Sim-Smith & Hickman & Kelly, 2021

Sim-Smith, Carina, Hickman, Cleveland & Kelly, Michelle, 2021, New shallow-water sponges (Porifera) from the Galápagos Islands, Zootaxa 5012 (1), pp. 1-71 : 60-61

Leucilla agitata sp. nov.

( Figs. 29–30 ; Table 12)

Material examined. Holotype — MCCDRS9408, Punta Vicente Roca , Isabela Island, 0.049° S, 91.558° W, 5–10 m, 19 Jun 2001.

Type locality. Isabela Island .

Habitat and distribution. Only known from type locality; 5–10 m. Found growing on hard surfaces.

Description. Digitate-branching sponge with small tubes, 10 mm high and 2–4 mm in diameter, arising from a spreading basal mass. Some tubes may branch several times. A single oscule is present at the apex of each tube, opening into a tubular atrium ( Fig. 29A–B ). Colour in life and in ethanol, cream. Texture is firm, crunchy, scratchy to the touch, compressible.

Skeleton. Cortical skeleton has a perpendicular layer of microdiactines at the surface that are organised into tuffs. Small cortical triactines are also scattered at the surface ( Fig. 29D ). Large cortical tetractines are arranged so their basal triradiate system is tangential to the surface and the apical actine is pointing towards the centre of the sponge. The tips of the largest spicules may go all the way through the atrial skeleton where the body wall is narrow ( Fig. 29E ).

The choanosomal skeleton is inarticulate, consisting of the apical actines of the cortical tetractines and the moderately large sagittal triactines, and rarely tetractines, arranged so their apical actines are pointing outwards ( Fig. 29E ).

The atrial skeleton is formed by small, slender saggital triactines and tetractines. Tetractines are arranged so their basal system is tangential with the atrial surface and their apical actine is pointing inwards towards the atrium ( Fig. 29F ).

Spicules. Cortical microdiactines, curved and flattened, with one end rounded and one end pointed. The round- ed half of the spicule has serrated edges ( Fig. 30A–B ).

Cortical triactines, sagittal with conical actines. There is little difference in length between the paired and unpaired actines ( Fig. 30D ).

the actines is measured at the widest part. A minimum of twenty spicules per category are measured.

Cortical tetractines, sagittal, large with conical actines that may be wavy. The angles of the basal rays are variable ( Fig. 30C ).

Subatrial tri- and tetractines, sagittal with conical actines. The unpaired actine is relatively long. Triactines are more common than tetractines ( Fig. 30E–F ).

Atrial tri- and tetractines, sagittal with long slender actines. Length of the unpaired actine is much shorter than the paired actines. Tetractines have a very short apical actine ( Fig. 30I–J ).

Etymology. Named for the morphology of the sponge in situ, which resembles a mass of waving hands (Latin adjective agreeing with Leucilla = ‘agitated, disturbed, excited’).

Remarks. Only two species of Leucilla have been described from the eastern Pacific, which can be differentiated from L. agitata sp. nov. as follows:

• L. mancoraensis Cóndor-Luján, Azevedo, Hajdu, Hooker, Willenz & Klautau, 2019 from Peru lacks microdiactines;

• L. nuttingi ( Urban, 1902) from California possesses large oxeas (1250 × 25 µm) and smaller atrial tri- or tetractines (rays 20–100 µm long).

Juvenile specimens of Paraleucilla can be mistaken for species of Leucilla , which are very similar except they possess a disorganised inner skeleton that develops as the body wall thickens ( Lanna et al. 2017). Only one species of Paraleucilla has been described from the eastern Pacific: P. tarazonai Cóndor-Luján, Azevedo, Hajdu, Hooker, Willenz & Klautau, 2019 from Peru. That species is a massive, ramified sponge that possesses large diactines in addition to microdiactines, very slender cortical triactines, and subatrial triactines that have a shorter unpaired actine (80–300 µm) than L. agitata sp. nov.

Figures

FIGURE 29. Leucilla agitata sp. nov. holotype, MCCDRS9408: A. Deck photo. B. Close up of a portion of the holotype, preserved. C. Cross section showing the inarticulate skeleton. D. Cross section of the cortex (cx) showing the tuffs of microdiactines (white arrow) and ectosomal triaenes (black arrow). E. Cross section showing the large cortical tetractines that can reach all the way to the atrium (at). F. Cross section of the atrial skeleton showing the subatrial tri- and tetractines (white arrow), and the apical actines of atrial tetractines protruding into the atrium (black arrow).

FIGURE 30. Leucilla agitata sp. nov. holotype, MCCDRS9408: A. Microdiactines. B. Close up of the serrated tip of the microdiactine. C. Cortical tetractines. D. Cortical triactines. E. Subatrial triactine. F. Subatrial tetractine. G. Atrial tetractine. H. Atrial triactine.