Family MICROCIONIDAE Carter, 1875

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Family MICROCIONIDAE Carter, 1875

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

Microcionids have encrusting, massive, lobate, fan-shaped (Hooper & Wiedenmayer 1994: fig. 3) and branching growth forms. The ectosomal skeleton is composed of styles (Hooper & Wiedenmayer 1994: figs 17, 18, 20) or anisoxeas (Hooper & Wiedenmayer 1994: fig. 19) (exceptionally oxeas; Hooper & Wiedenmayer 1994: fig. 5), in erect bundles, forming a continuous crust, lying tangentially or sparsely dispersed on the surface. The subectosomal skeleton is relatively poorly developed. The choanosomal skeleton has well-developed spongin fibres which form hymedesmoid, microcionid, plumose, plumo-reticulate, reticulate or axially condensed tracts. Spongin fibres are cored by smooth or partially spined large styles, and echinated by smooth, wholly or partially spined small styles (Hooper & Wiedenmayer 1994: fig. 22) or modified forms (acanthoxeas or acanthostrongyles; Hooper & Wiedenmayer 1994: fig. 14) embedded perpendicular to fibres. Microscleres typically are palmate isochelae, sometimes with modifications (anchorate-like, arcuate-like, Isodictya-like or unguiferous isochelae (Hooper & Wiedenmayer 1994: figs 66–69, 85), but not true forms of these spicules), and also toxas (Hooper & Wiedenmayer 1994: figs 89, 90), and in a few species microxeas (Hooper & Wiedenmayer 1994: fig. 105) (which may be highly modified toxas). Sexual reproduction where known is exclusively viviparous.

This family is possibly the most abundant and diverse of any family of Porifera. Approximately 560 nominal species have been described, of which about 460 are probably valid, and there are over 50 other known (collected) undescribed species in the Indo-West Pacific alone. Species in the family are widely distributed in all the world's oceans, although there are two peaks of biodiversity: one in the tropical Indo-Malay and Australian region, and the other in the north-western Atlantic (Hooper & Lévi 1994). They have been recorded from intertidal habitats to depths of at least 2460 m (Hartman 1982).

The Microcionidae fauna of Australia is unusually diverse, with over 150 species known for the Australian shelf and islands, and many more undescribed species. Small, encrusting Clathria species are particularly common in the interstices of coral reefs, bonding and/or bioeroding the coralline substrate, and it is likely that numbers of species will rise dramatically once investigators focus on that habitat.

Of more than 80 nominal genera included in Microcionidae at one time or another, of which 72 are currently recognised as (potentially) appropriately referred to the family, most of these have been merged with other well established taxa (e.g. Lévi 1960a; Simpson 1968; Van Soest 1984; Hooper 1988, 1990). Eight of these, with 12 subgenera, are now recognised (Clathria (with subgenera Clathria, Wilsonella, Microciona, Dendrocia, Axosuberites, Isociella, Thalysias);Antho (with 3 subgenera Antho, Acarnia, Isopenectya); Echinoclathria, Holopsamma, Artemisina, Echinochalina (with 2 subgenera Echinochalina, Protophlitaspongia); Hooper, 1996), two without Australian records (Pandaros; Ophlitaspongia s.s.; the latter resurrected recently by Howlett & Chambers (1998) exclusively for NE. Atlantic species).

The priority of Microcionidae over Clathriidae is indisputable under the rules and recommendations of the ICZN (Article 40, but not clause 40a since Microcionidae and Ophlitaspongiidae de Laubenfels, 1934 were used by Thomas (1969) and Hoshino (1981) in place of Clathriidae). This was clarified by Wiedenmayer (1977), and accepted in several recent publications (Hooper 1990, 1996; Hooper et al. 1990, 1992). The emended definition of Microcionidae (including also Ectyoninae Wilson, 1925) restricts the family to genera which possess predominantly smooth monactinal ectosomal and choanosomal spiculation. It excludes many microcionid-like genera which have true diactinal ectosomal megascleres and true arcuate or anchorate isochelae microscleres (of relevance to the Australian fauna are the genera Acarnus and Megaciella; cf. Hallmann 1920; Hooper 1987, 1990), but only barely differentiates taxa with modified or reduced quasi-diactinal (e.g. Echinochalina (Echinochalina)) or quasi-monactinal auxiliary megascleres (e.g. Echinochalina (Protophlitaspongia)) (Hooper 1988, 1990, 1996). Similarly, the distinction is barely sufficient to differentiate some Microcionidae (e.g. Axociella, sensu stricto) and some Raspailiidae (e.g. Raspailia, sensu stricto) (Hooper 1991; and refer to Raspailiidae in this work). Bergquist & Fromont (1988) emphasised skeletal architecture and certain aspects of spicule geometry in their revision of New Zealand microcionids, and recognised genera such as Clathria, Microciona, Dictyociona, Rhaphidophlus (=Thalysias) and Pseudanchinoe as being distinct, whereas Hooper (1988, 1990, 1996) gave weight to geometry, origin of megascleres and their distribution within the skeleton, and recognised only 7 genera and 12 subgenera, within a phylogenetic framework. This is followed in the present work.

Recent revisions include Van Soest (1984); Bergquist & Fromont (1988; who define Clathriidae and describe New Zealand species, some of which have Australian records); Wiedenmayer (1989); and those of Hooper (1988, 1990, 1996), Hooper & Lévi (1993) and Hooper et al. (1992). Other relevant works are those of Hentschel (1923); Lévi (1960, as Clathriidae, a key review of European species); Brien et al. (1973, as Clathriidae); Bergquist (1978) and Hartman (1982) (both as Clathriidae); and Van Soest et al. (1984, define and discuss the Clathriidae).{Hooperj1996a}

Diagnosis

Microcionina with encrusting, lobate, arborescent or flabellate growth forms. Skeleton differentiated into choanosomal (axial), subectosomal (extra-axial) and ectosomal regions. Axial skeleton formed by unispicular or multispicular tracts of choanosomal (principal) megascleres, typically coring spongin fibres or sometimes simply bound together by collagen. Fibres echinated by (acantho-) styles (accessory spicules). Skeletal structures include isodictyal, renieroid, reticulate, plumo-reticulate, plumose or hymedesmioid, but never radial. Subectosomal (extra-axial) skeleton formed by tracts of subectosomal (auxiliary) spicules, usually dispersed outside of fibres, rarely well organised but usually with some degree of difference between axial and extra-axial regions. Ectosomal skeleton ranges from membraneous, or with protruding larger (subectosomal auxiliary) spicules, or with a special category of smaller (ectosomal auxiliary) spicules. Principal megascleres monactinal, predominantly smooth or only partially spined, occasionally vestigial or absent completely, supplemented by another category of acanthose diactinal spicules, or sometimes replaced by detritus. Auxiliary megascleres usually monactinal, rarely quasidiactinal, smooth shaft and basal spines, more slender than choanosomal spicules. Echinating styles or subtylostyles smooth, partially or completely spined. Renieroid skeleton composed of acanthose or occasionally smooth styles or ‘dumbell’ spicules. Microscleres include toxas of several morphologies (including raphidiform and rarely microxeote toxas), and palmate isochelae. Some species have modified chelae, arcuate-like or anchorate-like, a result of torsion of the shaft and detachment of alae, but these are exceptional. Larvae viviparous.

ID Keys

KEYS TO MICROCIONIDAE
Key to subfamilies
(1) With a single primary skeletal structure: reticulate, plumo-reticulate, plumose hymedesmioid, microcionid or axially compressed--------------------------------------------------------------------------------------------- Microcioninae
With a secondary renieroid spongin fibre and/or spiculose skeleton overlaying a primary reticulate, plumo-reticulate, plumose or hymedesmioid spiculo-spongin skeleton ------------------------------------------------- Ophlitaspongiinae

Key to genera and subgenera
(1) Choanosomal skeleton more-or-less undifferentiated, unstructured ---------------------------------- Artemisina
Choanosomal skeleton well structured, ranging from hymedesmioid to reticulate, but lacking any differentiated components ---------------------------------------------------------------------------------------------------------------------- 2
Choanosomal skeleton well structured, predominantly reticulate, differentiated into two distinct structural components (e.g., primary renieroid skeleton overlaid by secondary plumose or radial skeletons) ----------------- 7

(2) Choanosomal fibres cored by one or more category of principal spicules ------------------------------------------- 3
Choanosomal fibres cored by auxiliary spicules partially (or sometimes wholly) replaced by detritus --------------- 5
Choanosomal fibres cored by auxiliary spicules identical to those in ectosomal and subectosomal skeletons ------ 6
Choanosomal fibres form a ladder-like isodictyal reticulation, but only primary fibres cored by plumose columns of megascleres and transverse fibres virtually clear ------------------------------------------------------ Ophlitaspongia
Choanosomal fibres or skeletal tracts cored by auxiliary spicules different from those in peripheral skeleton ------------------------------------------------------------------------------------------------------------------------ Pandaros

(3) Choanosomal skeleton without any marked axial compression or differentiated axial and extra-axial regions ------------------------------------------------------------------------------------------------------------------------------------ 4
Choanosomal skeleton with noticeably compressed axis and well differentiated axial and extra-axial (radial, plumose or plumoreticulate) regions; lacking echinating megascleres ------------------------------ Clathria (Axosuberites)
Choanosomal skeleton evenly renieroid reticulate throughout, with well developed spongin fibres cored by smooth principal styles; lacking echinating megascleres --------------------------------------------------- Clathria (Isociella)
Choanosomal skeleton hymedesmioid or microcionid, with basal layer of spongin lying on substrate without ascending fibre nodes ranging to ascending non-anastomosing columns of spongin fibres; bases of principal styles perpendicular to the substrate or forming plumose tracts in ascending fibres, and with acanthostyles or smooth styles echinating megascleres, differentiated from principal styles coring fibres ---------- Clathria (Microciona)

(4) With a single category of subectosomal auxiliary spicule forming the ectosomal skeleton, producing tangential, paratangential or plumose tracts; choanosomal skeleton predominantly reticulate or plumo-reticulate -------------------------------------------------------------------------------------------------------------- Clathria (Clathria)
With two categories of auxiliary spicules, smaller ectosomal spicules generally overlaying larger subectosomal spicules forming discrete bundles or continuous palisade on surface ---------------------------- Clathria (Thalysias)

(5) Echinating acanthostyles differentiated from principal spicules coring fibres -------------- Clathria (Wilsonella)
Echinating styles or acanthostyles identical to principal styles coring spongin fibres ------------------- Holopsamma

(6) Echinating acanthostyles differentiated from auxillary spicules coring the fibres --------- Clathria (Dendrocia)
Fibres cored by a single category of auxillary styles identical to those forming subectosomal and ectosomal skeletons, and echinated by smooth styles derived from principal spicules ------- Echinochalina (Echinochalina)
Fibres cored by a single category of auxiliary oxeas or styles different from principal oxeas, anisoxeas or styles that echinate fibres --------------------------------------------------------------------- Echinochalina (Protophlitaspongia)

(7) Primary skeleton renieroid, cored by axially or basally compressed tracts of acanthostyles; secondary skeleton subisodictyal or plumo-reticulate, cored by smooth principal styles in plumose tracts ---------------- Antho (Antho)
Primary skeleton renieroid, cored by axially or basally compressed tracts of acanthostrongyles; secondary skeleton subisodictyal or plumo-reticulate, cored by smooth principal styles in plumose tracts -------------- Antho (Acarnia)
Primary skeleton composed of axially compressed spongin fibres cored by renieroid tracts of sparsely spined principal styles intermingled with plumose or plumo-reticulate tracts of smooth principal styles, overlaid by secondary extra-axial plumose skeleton cored by larger smooth principal styles ------------------------- Antho (Isopenectya)
Primary renieroid reticulate skeleton cored by smooth principal styles and echinated by identical spicules, with secondary radial extra-axial skeleton on exterior edge of skeleton cored only by larger smooth principal styles --------------------------------------------------------------------------------------------------------------------- Echinoclathria