Latrunculia

Samaai, Toufiek, Janson, Liesl & Kelly, Michelle, 2012, New species of Latrunculia from the Agulhas shelf, South Africa, with designation of a type species for subgenus Biannulata (Demospongiae, Poecilosclerida, Latrunculiidae), Zootaxa 3395, pp. 33-45 : 36-37

Genus Latrunculia du Bocage, 1869

Diagnosis. Encrusting or hemispherical sponges, with trumpet-shaped or cylindrical oscules, and broad meandering or sucker-shaped areolate porefields. Surface is velvety, texture soft, cakey, colour in life liquorish black to brown, dark emerald, khaki or olive green. Choanosomal skeletal architecture consists of megascleres arranged in an irregular broad-meshed reticulation of wispy tracts that lack spongin reinforcement. Ectosomal skeleton is an oblique to tangential layer of megascleres, which are styles, usually slightly sinuous and irregular along the length, occasionally polytylote, occasionally lightly acanthose and/or terminally spined. Microscleres are anisodiscorhabds disposed predominantly in a palisade with the manubrium and basal whorl buried in the outer ectosome. Anisodiscorhabds have six substructures that may merge or fuse to varying degrees; the manubrium, basal whorl, median whorl, subsidiary whorl, apical whorl and the apex, usually a tuft of spines. The manubrium is the most basal part of the microsclere, above which lies a basal whorl. Between the basal and apical whorls lie the median and subsidiary whorls, which are typically unequal in diameter (the median whorl is always the larger), and located on the upper half of the spicule shaft. The morphology of the whorls is diverse; they may be composed of spines (smooth, acanthose or serrated) or frilly brackets (smooth or acanthose) with denticulate or spined margins. These frilly brackets may be flat, undulating, or angled obliquely to the shaft. The whorls completely surround the shaft, or may be partially or fully incised. In addition to the typical anisodiscorhabd, there may be large spined metasterlike oxydiscorhabds, acanthomicroxeas, or aciculodiscorhabds in which the apex elongates to form a spine, or a form that has numerous whorls along the shaft (emended from Samaai et al. 2006).

Remarks. In the majority of Latrunculia species, the developing anisodiscorhabd has 4 primary progenitors, resulting in a range of substructures in the mature microsclere (see Alvarez et al. 2002: figs 6d, 8f, 8g, 9d, 12c; Samaai et al. 2004: fig. 2; 2006: figs 6k, 6l). In L. (L.) cratera , type species of the subgenus Latrunculia , there are at least six distinct substructures (manubrium, basal whorl, median whorl, subsidiary whorl, apical whorl and an apex) (see Samaai et al. 2006: fig. 1a) ( Fig. 1 , left). Specifically, the apical progenitor emerges as the apical whorl and apex, and the basal progenitor emerges as the manubrium and basal whorl in the mature spicule.

These six substructures may merge or fuse to varying degrees along the shaft of the anisodiscorhabd, and this arrangement forms the basis upon which new subgenera can now be consistently recognised and defined within Latrunculia . The ornamentation and morphology of substructures, the morphology and ornamentation of the megasclere, and the presence of additional microsclere forms, may provide additional characters that support these subgeneric differences. It remains to be seen whether the several quite distinctive forms of inhalant aquiferous structures seen in the genus Latrunculia (broad meandering craters vs elevated trumpet-shaped porefields) and exhalent oscules (simple circular oscules with flush or raised margins that may be either thick or membranous), support the current subgeneric distinctions. Observations thus far indicate that there is no partitioning of the type of aquiferous structure to either subgenus in New Zealand ( Alvarez et al. 2002) or South African ( Samaai et al. 2003; 2006) species. The diagnosis of genus Latrunculia has been refined and expanded accordingly, to accommodate the present and future potential subgeneric distinction.

Figures

FIGURE 1. Comparison of typical microsclere morphology of species in Latrunculia subgenera, showing the six substructures that characterise all anisodiscorhabds, whether differentiated or undifferentiated: Left, Latrunculia (Latrunculia) triverticillata Alvarez et al. 2002; Right, Latrunculia (Biannulata) kaakaariki Alvarez et al. 2002.