JENKINIDAE, Borojevic & Boury-Esnault & Vacelet, 2000

Borojevic, Radovan, Boury-Esnault, Nicole & Vacelet, Jean, 2000, A revision of the supraspecific classification of the subclass Calcaronea (Porifera, class Calcarea), Zoosystema 22 (2), pp. 203-263 : 229-230

Family JENKINIDAE n. fam.

TYPE GENUS. — Jenkina BrØndsted, 1931 by original designation.

DIAGNOSIS. — Leucosoleniida with a syconoid, sylleibid or leuconoid organization. The thin wall surrounding the large atrial cavity is supported by tangential atrial and cortical skeletons, and essentially an inarticulate choanoskeleton consisting of unpaired actines of the subatrial triactines and/or tetractines, and occasionally with small radial diactines. The proximal part of the large radial diactines that protrude from the external surface, or the tangential triactines

cx

scattered irregularly in the cortex, may also form the choanoderm. Large cortical tetractines or subcortical pseudosagittal triactines are not present.

DESCRIPTION

We propose the family Jenkinidae for a group of sponges characterized by an inarticulate choanoskeleton ( Fig. 25 ). Dendy & Row (1913) considered this character not to be relevant at the generic level, and only BrØndsted (1931) proposed separating the leuconoid sponges with an inarticulate skeleton into the genus Jenkina . However, a primary inarticulate type of choanoskeleton is a characteristic of the family Amphoriscidae , in which it is always associated with the presence of large cortical tetractines (Borojevic & Boury-Esnault 1987). Dendy (1913) and Dendy & Row (1913) underlined the difference between the sponges of the genus Leucilla that have an inarticulate type of choanoskeleton and which derive from Amphoriscus , and those with an articulate skeleton, by transferring the former group to the genus

cx ss as

Leucandra (placed now into the new genus Leucandrilla ). They thus implied that the inarticulate type of the choanoskeleton, and not the cortical tetractines, is the primary characteristic of the family Amphoriscidae . We now consider that the inarticulate type of sponge wall organization, with a thin choanoderm and well-defined atrial and cortical skeletons, is a consequence of a particular type of growth, and is not a secondary reduction of the sponge wall thickness during evolution. Consequently, sponges with this organization should be separated from those with a massive type of growth as is observed in the Grantiidae . While in the Amphoriscidae the cortical skeleton is always supported by large tetractines, in the Jenkinidae it can be thin (e.g. Jenkina , Leucascandra ), or reinforced by large diactines or triactines (e.g. Uteopsis and Anamixilla , respectively). It should be emphasized that young specimens of Grantiidae , and the suboscular region of adult Grantiidae in which the sponge grows longitudinally, can have an inarticulate skeleton that becomes an articulate one when sponge is fully grown. Conversely, the Jenkinidae are characterized by an inarticulate skeleton in the fully-grown sponges. As mentioned previously the growth of these long tubular sponges into a large branched cormus such as observed in Leucascandra , Anamixilla and Uteopsis is a consequence of the restriction of their radial growth, and this is unique in the Leucosoleniida .

Figures

FIG. 25. — Diagram of the Jenkinidae-type of skeleton. Abbreviations: a, atrium; as, atrial spicules; ss, subatrial spicules; cx, cortex.