Hymedesmia Bowerbank, 1864

Salani, Sula, Willenz, Philippe, Fernandez, Julio C. C. & Hajdu, Eduardo, 2022, Three new Hymedesmia Bowerbank, 1864 (Demospongiae, Poecilosclerida Hymedesmiidae) from the Southeast Pacific (Peru and Chile), Zootaxa 5165 (2), pp. 217-240 : 219-238

Genus Hymedesmia Bowerbank, 1864

Type species. H. (H.) zetlandica Bowerbank, 1864 (by monotypy).

Diagnosis. Mostly thinly encrusting; ectosomal skeleton composed of smooth ectosomal tornotes strewn at the surface and forming bundles in the choanosome; choanosomal basal skeleton hymedesmioid, composed of one, two, or three sizes of acanthostyles standing singly erect on the substrate; microscleres, when present, are arcuate isochelae and/or sigmas (one species has microstrongyles). Chelae can occasionally form dense aggregations in the ectosome. Modified from van Soest (2002).

Remarks. Van Soest’s (2002) diagnosis is amended here to account for the possible thickly encrusting habit, occurrence of a third category of acanthostyles, the possibility that chelae may form dense aggregations, and the rare occurrence of microstrongyles These characters can be observed from the new species described below.

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Legend: m- meters; * - when the article does not give the coordinate, it is measured at the midpoint of the location

Identification key for Hymedesmia spp. from the Kerguelen Islands, South-eastern Pacific, South-western Atlantic, South Georgia and the Antarctic

1a With microscleres.................................................................................... 2

1b Without microscleres................................................................................. 13

2a Ectosomal tornotes 500 µm long or bigger...................................... H. (H.) antarctica Hentschel, 1914

2b Ectosomal tornotes may occasionally approach 400 µm but usually are much smaller............................... 3

3a Largest acanthostyles approaching 500 µm long or bigger..................................................... 4

3b Largest acanthostyles around 400 µm long or smaller........................................................ 7

4a Microscleres are arcuate isochelae only................................................................... 5

4b Microscleres include small unguiferate isochelae too.............................. H. (H.) decepta ( Kirkpatrick, 1907)

5a Ectosomal tornotes oxeote.............................................................................. 6

5b Ectosomal tornotes strongylote............................................................ H. (H.) leptochela

6a Largest acanthostyles only marginally larger than 500 µm, no thicker than 25 µm, and smooth only close to the point........................................................... H. (H.) mariondufresni Boury-Esnault & van Beveren, 1982

6b Largest acanthostyles over 600 µm, up to 40 µm thick, and smooth on the apical two thirds of the shaft....................................................................... H. (H.) noramaloneae Goodwin, Berman & Hendry, 2019

7a Microscleres include forms (sigmas, microstrongyles) other than arcuate isochelae........... H. (H.) santarositae sp. nov.

7b Microscleres are arcuate isochelae only................................................................... 8

8a Acanthostyles up to 250 µm only........................ H. (H.) laptikhovskyi Goodwin, Jones, Neely & Brickle, 2016

8b Acanthostyles frequently larger than 300 µm............................................................... 9

9a Arcuate isochelae larger than 30 µm (up to 37)................................... H. (H.) gaussiana Hentschel, 1914

9b Arcuate isochelae up to 30 µm, or much smaller........................................................... 10

10a Stouter acanthostyles over 30 µm thick............................ H. (H.) barnesi Goodwin, Brewin & Brickle, 2012

10b Stouter acanthostyles no thicker than 15 µm............................................................... 11

11a Ectosomal tornotes; arcuate isochelae scattered, mean dimensions 15–16 µm.................. H. (H.) peruana sp. nov.

11b Ectosomal strongyles; arcuate isochelae concentrated at the surface, mean dimensions 21–22 µm.................... 12

12a Live colour light orange (peach), arcuate chelae stout, and frequently nearly semi-circular, up to 27 µm....................................................................... H. (H.) croftsae Goodwin, Jones, Neely & Brickle, 2016

12b Live colour reddish-orange (annatto-seeds), arcuate chelae slender, not semi-circular, up to 25 µm H. (H.) humboldti sp. nov.

13a Acanthostyles I 210–700 µm................................................... H. (S.) fristedti ( Topsent, 1916)

13b Acanthostyles I always smaller than 500 µm............................................................... 14

14a Ectosomal styles (190–250 µm; acanthostyles I ≤ 360 µm, acanthostyles II ≤ 145 µm)...................................................................... H. (S.) lissostyla ( Bergquist & Fromont, 1988) , sensu Bertolino et al. (2020)

14b Ectosomal diactines (205–282 µm or quite larger).......................................................... 15

15a Ectosomal oxeas (205–282 µm)................................... H. (S.) pharos Goodwin, Brewin & Brickle, 2012

15b Ectosomal strongyles (296–328 µm or quite larger)......................................................... 16

16a Ectosomal strongyles (336–432 µm), acanthostyles (160–400 x 10–12 µm, shaft only)........................................................................................... H. (S.) ernsthentscheli Van Soest & Hooper, 2020

16b. Ectosomal strongyles (296–328 µm), acanthostyles I (352–480 x 25 µm, shaft only), acanthostyles II (128–144 x 9–10 µm)................................................................. H. (S.) hentscheli Van Soest & Hooper, 2020