Order DICTYOCERATIDA Minchin, 1900

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Diagnosis

Demospongiae in which a spongin fibre skeleton, which makes up a significant proportion of the body volume, is universally present and is constructed on an anastomosing plan. The skeleton develops from multiple points of attachment and, except in two genus where primary fibres are absent, is organised as a hierarchy of primary, secondary and sometimes tertiary elements. In one family the reticulate skeleton is supplemented by fine collagenous filaments dispersed throughout the mesohyl. Fibre construction is homogeneous lacking pith with growth laminae tightly adherent and just detectable, or pithed and strongly laminated with pith grading into bark, consecutive laminae are marked but remain adherent to each other (Bergquist, 1980b: Fig. 2a). Pith is structurally and chemically distinct from that seen in fibres of Verongida and Dendroceratida. The choanocyte chambers are either diplodal or eurypylous. Cells of the mesohyl are moderately to weakly diversified, never showing the range of structural types seen in Dendroceratida or Verongida. Larvae are incubated parenchymellae with complex histology and a posterior ring or cap of long cilia. Sponge texture is characteristically compressible and tough, never heavily collagenous throughout, hard when debris is incorporated, soft when the skeleton is reduced in proportion to soft tissue mass. There is always a marked differential pigmentation, with surface layer dark and the interior ranging from white through cream to pale brown or pale to bright yellow. In terms of biochemistry the group is characterised by a very low sterol content and a diverse range of terpenes within the lipid fraction.

ID Keys

KEY TO FAMILIES

(1)Without hypercalcified basal skeleton ----------------------------------------------------------------------- 2
With a hypercalcified basal skeleton -------------------------------------------------- Verticillitidae, Vaceletia

(2)Fine collagenous filaments present in addition to the fibre skeleton --------------------------- Irciniidae
Lacking filaments --------------------------------------------------------------------------------------------------- 3

(3)Fibres concentrically laminated with laminae clearly defined ---------------------------------------------- 4
Fibres homogeneous, without marked laminations ------------------------------------------------- Spongiidae

(4)Choanocyte chambers small, spherical.(diplodal) ---------------------------------------------- Thorectidae
Choanocyte chambers large, oval (eurypylous) ---------------------------------------------------- Dysideidae

Diagnosis References

Cook, S.D.C. & Bergquist, P.R. 2002. Order Dictyoceratida Minchin, 1900. 1021 in Hooper, J.N.A. & van Soest, R.W.M. (eds). Systema Porifera: A guide to the classification of sponges. New York : Kluwer Academic/Plenum Publishers Vol. 1. [1021]

Vacelet, J. 2002. Recent 'Sphinctozoa', Order Verticillitida, Family Verticillitidae Steinmann, 1882. pp. 1097-1098 in Hooper, J.N.A. & van Soest, R.W.M. (eds). Systema Porifera: A guide to the classification of sponges. New York : Kluwer Academic/Plenum Publishers Vol. 1. [1097]

General References

Cook, S.D.C. & Bergquist, P.R. 2002. Order Dictyoceratida Minchin, 1900. 1021 in Hooper, J.N.A. & van Soest, R.W.M. (eds). Systema Porifera: A guide to the classification of sponges. New York : Kluwer Academic/Plenum Publishers Vol. 1.

Wörheide, G. 2008. A hypercalcified sponge with soft relatives: Vaceletia is a keratose demosponge. Molecular Phylogenetics and Evolution 47: 433-438 [433]

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