Family HYMEDESMIIDAE Topsent, 1928

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Family HYMEDESMIIDAE Topsent, 1928

Compiler and date details

2010 - John N.A. Hooper, Queensland Museum, Brisbane, Queensland, Australia; Felix Wiedenmayer (1994), Naturhistorisches Museum Basel, Basel, Switzerland; updated by John N.A. Hooper (1999)

Introduction

Sponges in Hymedesmiidae Topsent, 1928 show persistently encrusting growth. The oscula and ostia may be borne on papillae, or the ostia may be grouped over the subdermal cavities. Spined bases of intermingled large choanosomal styles (Hooper & Wiedenmayer 1994: figs 17, 18) and smaller acanthostyles (Hooper & Wiedenmayer 1994: fig. 22) are embedded in a basal layer of spongin, standing perpendicular to the substrate. Smooth, often polytylote, diactinal (tornotes, anisotornotes or oxeas; Hooper & Wiedenmayer 1994: figs 7, 8, 10) or sometimes monactinal spicules (styles), occur singly or form bundles on the surface. Microscleres include palmate, arcuate or unguiferous isochelae (Hooper & Wiedenmayer 1994: figs 66, 67, 69), sigmas (Hooper & Wiedenmayer 1994: figs 79, 80), forceps (Hooper & Wiedenmayer 1994: fig. 91), and sometimes also anisochelae (Hooper & Wiedenmayer 1994: fig. 73). Toxas are never present.

Sponges of this family are widely distributed in the world's oceans, occurring from intertidal habitats to depths of at least 2450 m (Hartman 1982). Twenty-two nominal genera are included in this family, although only 13 are presently recognised, seven of which have published Australian records. The present concept of the family is in urgent need of revision. It is undoubtedly artificial, containing disparate chelae types, with the only common theme being an encrusting hymedesmoid skeletal architecture. The genus Hymedesmia is particularly common in coral rubble and in the interstices of coral reefs, and there are potentially many species of this genus although only relatively few have been recorded so far in the Australian region.

The family is reviewed in Topsent (1928), Brien et al. (1973), Bergquist (1978), Hartman (1982) and Van Soest (1984); New Zealand species are revised by Bergquist & Fromont (1988).

Diagnosis

Encrusting, massive and branching sponges; surface with characteristic groups of pores (areoles) (shared with Crellidae). Megascleres smooth diactinal spicules (oxeote, tylote or strongylote, occasionally stylote tornotes), grouped together or scattered in the ectosome, but never forming a crust, lying perpendicular, tangential, or paratangential to the surface, and acanthostyles, which may typically occur in a larger size class, which is often partly smooth in the pointed half, and a smaller size, which is usually entirely spined. Diactinal spicules forming thinner or thicker plumose or plumo-reticulate tracts or columns in the choanosome, with only a thin coat of spongin, or without optically visible spongin. Columns usually consist of spicules identical to those in the ectosome, but sometimes these are replaced by acanthostyles. They may or may not be echinated by 1–2 sizes of acanthostyles. At the base of the sponge there is usually a spongin plate closely adhering the substrate and echinated by single acanthostyles or groups or bundles of acanthostyles. Microscleres may include arcuate isochelae and sigmas.

ID Keys

KEY TO GENERA
(1) Spicules exclusively smooth styles and strongyles, no microscleres or acanthose spicules ---------Hemimycale
Microscleres and/or spined spicules present ---------------------------------------------------------------------------------- 2

(2) Microscleres are profusely ornamented chelae or derivates------------------------------------------------------------ 3
Microscleres if present are smooth-shafted -----------------------------------------------------------------------------------4

(3) Skeleton structure hymedesmioid, i.e., with single acanthostyles erect on the substratum ---- Acanthostyles
Skeleton consistst of columns of tornotes without acanthostyle --------------------------------- Pseudohalichondria

(4) All spicules smooth, spined spicules absent ------------------------------------------------------------------ Hamigera
Lightly or more heavily spined spicules present ------------------------------------------------------------------------------- 5

(5) Acanthostrongyles present forming a basal mass or reticulation ------------------------------------- Plocamionida
No acanthostrongyles or basal reticulation ------------------------------------------------------------------------------------ 6

(6) Skeleton hymedesmioid, i.e., with acanthostyles singly erect on the substratum ------------------ Hymedesmia
Skeleton plumose or plumoreticulate, acanthostyles, if present, echinating the choanosomal tracts, incorporated in the skeletal columns or strewn in the interior, not singly erect on the substrate ---------------------------------------- 7

(7) Accessory acanthose spicules (acanthostyles, acanthoxeas) present, strewn in the interior, not localized; choanosomal styles smooth or microspined -------------------------------------------------------------------- Spanioplon
Acanthostyles localized in echinating position, or incorporated in the skeletal tracts ----------------------------------- 8

(8) Acanthostyles only in skeletal columns or tracts ------------------------------------------------------------------------ 9
Acanthostyles echinating the columns or tracts or strewn randomly ---------------------------------------------------- 10

(9) A single category of acanthostyles ------------------------------------------------------------------------------ Phorbas
Two distinct categories of acanthostyles ----------------------------------------------------------------------- Myxodoryx

(10) Acanthostyles in echinating position --------------------------------------------------------------------------- Phorbas
Acanthostyles in the columns and strewn in the interior, not echinating -------------------------------- Kirkpatrickia