Amphimedon nanaspiculata ( Hartman, 1955 ) Hartman, 1955

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 31-33

Amphimedon nanaspiculata ( Hartman, 1955) comb. nov.

Figures 19 a–c

Axinella nanaspiculata Hartman, 1955: 180 , figs 5, 7, 10.

? Haliclona viridis ; Wells et al. 1960: 209, fig. 8 (not: Amphimedon viridis Duchassaing & Michelott, 1864 ).

Material examined. RMNH Por. 9297, 9893, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station D33, 6.9433°N 55.9483°W, Agassiz trawl, depth 60–62 m, bottom sand, shells, 4 May 1966 ; RMNH Por. 9861, 9963, 9975, 9987, 10504, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F40, 7.0033°N 56.4417°W, depth 59 m, bottom sand, 6 May 1966 ; RMNH Por. 9866, 10501, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F45, 6.4417°N 56.5467°W, depth 34 m, Van Veen grab, 7 May 1966 ; RMNH Por. 9875, 10516, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F46, 6.312°N 56.57°W, depth 25–29 m, bottom sand, 7 May 1966 ; RMNH Por. 9876, 9896, 9952, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station G7, 7.28°N 56.7933°W, depth 64 m, bottom sand, 7 May 1966 ; RMNH Por. 9935, 9946, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 63, 7.5833°N 57.0667°W, depth 71 m, sandy bottom, 31 August 1970 ; RMNH Por. 9958, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station H53, 7.0083°N 56.97°W, depth 38 m, bottom coarse sand with shells, 10 May 1966 (2 specimens) ; RMNH Por. 9997, 9998, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station C18, 6.2217°N 55.8333°W, depth 30 m, bottom sand, 25 April 1966 .

Description. Erect-arborescent sponge ( Fig. 19 a), with a short stalk and long, sparingly dividing branches. Specimens have the tendency to branch in one plane and may have short side branches ( Fig. 20 a1). Oscules of 2–3 mm diameter are scattered along the branches in a low frequency and flush with the surface. Surface punctate, optically smooth but microscopically hispid. Size of largest specimen (RMNH Por. 9876, Fig. 19 a) is 35 cm high, 16 cm wide, with stalk up to 3 cm long and individual branches up to 23 cm long and up to 1.5 cm in diameter, tapering to bluntly rounded endings of about 0.5 cm diameter. Branches may occasionally anastomose or have short side branches. Color (in alcohol) variably darker or lighter shades of brown. Consistency limp, soft.

Skeleton. Surface skeleton ( Fig. 19 b) a three-dimensional reticulation of spicule tracts of 10–35 µm thickness (1–7 spicules), forming unequal and ill-developed polygonal meshes of widely different sizes, 70–350 µm in diameter. Choanosomal skeleton ( Fig. 19 c) with strong ascending tracts, up to 70 µm in thickness (up to 10 spicules) interconnected irregularly by thinner tracts of up to 40 µm in thickness (up to 4 spicules). The reticulation forms meshes of widely different sizes, 100–600 µm in diameter. Spongin is variably merely binding or entirely enveloping the spicule tracts, depending of location in the skeleton and of individual sponges. Many loose spicules are present in the skeleton.

Spicules. Oxeas only.

Oxeas ( Fig. 19 d), slightly curved, usually sharply pointed, in a large size range, 99– 143 –189 x 4 – 6.49 –9 µm. Size variation is observed within and among specimens.

Distribution and ecology. Guyana Shelf, Gulf of Campeche, possibly North Carolina, on sandy bottom at 12–71 m depth.

Remarks. Hartman’s (1955) descriptions and figures, with additional images provided by Eric Lazo-Wasem of the Yale Peabody Museum at Harvard, U.S.A., together are sufficiently clear to make this identification with confidence. The shape and size, the details of the surface, oscules and skeleton, and the habitat (sandy-shelly bottom) all match. The spicule sizes cited by Hartman (56–132 x 3–7 µm) are somewhat lower than the present sizes (99–189 x 4–9 µm), but there is considerable overlap. Some of the Guyana specimens have spicule size ranges almost identical to those of the Yucatan holotype.

This species is closely related to Amphimedon viridis Duchassaing & Michelotti, 1864 , widely distributed in shallow water throughout the Central West Atlantic region, because limp consistency and skeletal and spicular characters are similar. Nevertheless there are several clearly distinct features precluding assignment of the present specimens to that species. The habit is arborescent-ramose with long, limp branches and most oscules flush with the surface. A. viridis may have repent branches, but is never arborescent, and its oscules are predominantly on volcanoe-shaped lobes.

Wells et al. (1960) reported an erect branched specimen found on the beach of North Carolina as Haliclona (= Amphimedon ) viridis . Although their drawing shows the specimen to be branched in all directions, it nevertheless may be close or similar to the present specimens. They suggested, no doubt based on a remark by De Laubenfels (1950) (p. 3), that the Bermuda species Pachychalina micropora Verrill, 1907 could be synonymous with A. viridis and would have ‘encrusting, massive and branching’ forms. However, Verrill’s description mentions only ‘encrusting, or small convex or lobate masses’, not branching. Verrill’s material has not been recently recognized with certainty in any sponge collection (see discussion in De Laubenfels 1950, p. 3), and his Pachychalina species remain Niphatidae incertae sedis.

Other branching Amphimedon species of the Central West Atlantic are Amphimedon compressa Duchassaing & Michelotti, 1864 (with junior synonym Amphimedon arborescens Duchassaing & Michelotti, 1864 ) and Amphimedon complanata (Duchassaing, 1850) (with junior synonyms Spngia fusca Duchassaing & Michelotti, 1864 , Spongia manus Duchasaing & Michelotti, 1864 , and Pachychalina variabilis Dendy, 1887 ). These two species have much more spongin in their skeletons and have much firmer consistency. Their forms are more variable, including broader shapes and fewer branches. For more character differences see Van Soest 1980 (pp. 26–34, pls IV–V).

Figures

FIGURE 19. Amphimedon nanaspiculata (Hartman, 1955), a, habitus of RMNH Por. 9876 (scale bar = 1 cm), a 1, of RMNH Por. 9985 (scale bar = 1 cm), b – c, light microscopic images of skeleton, b, surface skeleton of RMNH Por. 9896, c, cross section of RMNH Por. 9985, d, SEM image of oxea.

FIGURE 20. Niphates erecta Duchassaing & Michelotti, 1864, a, habitus of RMNH Por. 9895 (scale bar = 1 cm), a 1, of RMNH Por. 9877 (scale bar = 1 cm), b, light microscopic image of cross section of peripheral skeleton of RMNH Por. 9905, c – d, SEM images of spicules, c, oxeas, d, sigma.