Nardoa arabica, Voigt et al., 2017

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160: 55-59

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Nardoa arabica


Ernstia arabica Voigt et al., 2017 

Figures 28a–c View Figure , 29a–c View Figure , 30a–e View Figure

Ernstia arabica Voigt et al., 2017: 9  , figs 5a–e.

Material examined. ZMAAbout ZMA Por. 13640, Israel, Coral Garden , Gulf of Aqaba, depth 1.5 m, scuba, coll. M. Wunsch, field nr. AQ140, 15 July 1998  ; ZMAAbout ZMA Por. 13642, Egypt, Ras Mohammed, Shark Observatory , depth 15 m, scuba, coll. M. Wunsch, field nr. RM 222, 23 July 1998  .

Description. There are two, rather different specimens from the Gulf of Aqaba, which are assumed to be members of this species. Because of the differences we describe them separately. Cormus of ZMAAbout ZMA Por. 13640 ( Fig. 28a View Figure ) small yellow cushions connected by thinner stolon-like parts, structure compact made up of tightly anastomosed thin tubuli ( Fig. 28b View Figure ). Oscules centrally located on the cushions and slightly elevated. Lateral size of cormus up to 2.5 x 1 cm, thickness about 5–8 mm. ZMAAbout ZMA Por. 13642 is a flatly encrusting cormus ( Fig. 30a View Figure ) consisting of tightly anastomosed thin tubuli. Pale yellow in life, dirty white in alcohol. Several broader tubuli lead to a few wide oscules slightly raised above the cormus. Lateral size 5 x 4 cm. Constency soft.

Aquiferous system. Asconoid.

Skeleton. ( Figs 28b–e View Figure ) Walls of tubuli in both specimens are thin ( Fig. 28c View Figure ), consisting of one–two spicule layers ( Figs 28d View Figure , 30b View Figure ) with a mixture of tri- and tetractines; the apical actines of the latter are protruding into the tubule lumina ( Fig. 28c View Figure ) forming a dense palisade ( Fig. 28e View Figure ). Consistency firm.

Spicules. ( Figs 29a–c View Figure , 30c–e View Figure ) Triactines and tetractines, the latter present in clearly larger numbers. No distinct trichoxeas were found.

Triactines equiradiate and equiangular, with conical actines, some verging toward tripod-shape.

Actine sizes of ZMA Por. 13640 ( Fig. 29a View Figure ) measure 89– 98 –105 x 9 – 11.2 –13 µm.

Actine sizes of ZMA Por. 13642 ( Figs 30c View Figure ) measure 102– 125 –165 x 11 – 16.4 –26 µm.

Tetractines of similar shape and size to the triactines, equiangular, with conical actines.

Actines of the basal triradiate system in ZMA Por. 13640 ( Figs 29b View Figure ) measure 87– 94 – 99 x 9 – 10.3 –12 µm, apical actines ( Fig. 30c View Figure ) smooth, straight, 66– 76 – 91 x 5 – 6.6 –8 µm.

Actines of the basal triadiate system in ZMA Por. 13642 measure ( Figs 30d View Figure ) 67– 127 –182 x 9 – 15.2 –27 µm; apical actines ( Fig. 30e View Figure ) shorter, thinner and sharper, 23– 38 – 59 x 3 – 5.7 –11 µm.

Distribution and ecology. Israelian Red Sea, Saudi Arabian and Egyptian Red Sea ( Voigt et al. 2017), down to 15 m.

Remarks. The present specimens closely resemble the type in most aspects, except for the absence of trichoxeas. These were also not consistently present in the type material ( Voigt et al. 2017). A small further difference is the length of the apical actine of the tetractines, which has a greater range in the type material (up to 156 µm). The two present specimens differ subtly in the habitus and the smaller-thinner vs. the larger and more robust spicules. Voigt et al. (2017) described and measured the spicules of specimens from the Northern and Southern Red Sea and found triactines and tetractines having actine lengths between 38 and 116 µm, and apical actines between 56 and 156 µm, while our own specimens have these data respectively 67–182 µm and 23–91 µm.

Unfortunately, we were unable to obtain partial 28S rRNA sequences for these specimens. Below we compare E. arabica  with Western Indian Ocean specimens identified as the closely related Ernstia naturalis Van Soest & De Voogd, 2015.


Universiteit van Amsterdam, Zoologisch Museum














Nardoa arabica

Van, Rob W. M. & De, Nicole J. 2018


arabica Voigt et al., 2017 : 9

: 9