Meridionale Staples, 2014, gen. nov.

Genus Meridionale gen. nov.

Figure 2 F

Etymology. From Latin- Méridionale, southern. The generic name recognizes the Southern Hemisphere collection sites of all species assigned to the genus. This contrasts to the predominantly northern hemisphere Boreal-Arctic distribution of Pseudopallene species.

Diagnosis. Trunk smooth, compact, strongly arched in lateral view with an overall ‘hunched’ appearance, without spiniform projections, lateral processes typically separated by about half own basal diameter or less, often separated from trunk by suture lines separating trunk and lateral processes, cephalon strongly angled downward from the trunk, anterior region swollen, narrowing sharply to a short, constricted neck, lateral processes about as long as their greatest width, narrowly but distinctly separated. Abdomen short, often shield-shaped, not reaching beyond fourth lateral processes. Ocular tubercle moderately low, with laid-back appearance, apical surface sloping downward towards anterior, dorsal papillae usually conspicuous. Proboscis tip mamilliform, with setiferous fringe variably present on outer surface. Palps absent. Chelifores directed forward and downward from the cephalon, hanging vertically or facing backwards, scapes angled outwards, with conspicuous proximal constriction present in females; chelae carried in front of proboscis and transversely opposed to scapes, palm large, often swollen, fingers digitiform and variably opposed to palm, margins heavily sclerotized, sometimes with marginal lobe on one or both fingers. Oviger strigilis spines compound, terminal claw distally blunt or acute, with stout, saw-like teeth fringing both distal margins. Legs smooth or with spinules, surface rarely irregular. Tibia 2 longer than tibia 1 and femur, auxiliary claws absent. Femoral cement glands not evident. Genital pores conspicuous. Juvenile moveable fingers highly modified; proboscis tapering distally, tubiform.

Associated with arborescent bryozoans.

Type species. Meridionale laevis (Hoek, 1881).

Species included: M. ambigua (Stock, 1956a), M. brevicephala (Staples, 2008); M. chevron (Staples 2007); M. constricta (Arango and Brenneis 2013); M. difficile (Arango, 2009); M. dubia (Clark, 1963) species inquirenda; M. flava (Arango and Brenneis 2013); M. gracilis (Arango and Brenneis, 2013); M. harrisi (Arango and Brenneis 2013); M. inflata (Staples, 2005); M. laevis (Hoek, 1881); M. pachychiera (Haswell, 1885); M. reflexa (Stock, 1968); M. tasmania (Arango and Brenneis 2013) and M. watsonae (Staples, 2005).

Remarks. Meridionale laevis was the first species collected in Australian waters to be assigned to Pseudopallene. Based on an understanding at that time that the chelifore scapes were two-segmented, Schimkewitsch (1909) reassigned this species to the monotypic genus Pallenella. Only the number of scape segments separated Pallenella from Pseudopallen e and since then specimens with one-segmented scapes were assigned to Pseudopallene; most often to P. ambigua. Staples (2005) demonstrated that the scape segments of M. laevis were in fact one-segmented and the genera were synonymized. The type locality for M. laevis and M. ambigua is Bass Strait. The holotype of M. laevis has now been reexamined and based on existing collections the species is also known from South Australian waters. Examination of the M. laevis holotype has also enabled comparison with the previously examined holotype of M. ambigua. Expanded descriptions and additional figures of both species are provided.

As amply demonstrated by Arango and Brenneis (2013) colour and markings in life can be good species indicators but reliance on colour alone as a definitive character should be used with caution. Apart from M. harrisi, body patterns in the genus are few and mostly restricted to bandings and variable red striping on predominantly yellow bodies. Based on personal observations by the author, the majority of species are monochromatic; typically yellow, orange/brown and shades of red. Observations of colour changes attributed to diet are not uncommon but there are examples in species from other families where a colour change takes place independently of gut content. In these examples the actual colour patterns mostly remain stable. The dominant colour forms of Anoplodactylus evansi, Clark, 1963 seem to be variable, ranging along the east Australian coast from predominantly red in the south (Fig 2 A) to both red and blue forms being present in more northern waters (Fig. 2 B). The vivid colours in eastern waters change to pastel shades in the west. Likewise, variation is found in the colour of Pallenopsis macneilli Clark, 1963 (Figs.2 C, 2D). Based on photographic records, an undetermined species of M eridionale from N.W. Western Australian waters has similar markings to M. harrisi but the colour is in pastel shades of orange and yellow. Colours are quickly lost in most specimens preserved in ethanol and no significance should be attached to Stock’s (1956) failure to mention colour in his description of M. ambigua.

There are two basic but variable forms of oviger claw in Meridionale. A slender, strongly tapered form (see Staples, 2005, fig 2G) and a broad, distally rounded form (see Staples, 2005, fig 4G). The claws are otherwise morphologically similar with teeth or crenulations present on the distal margins.

In terms of species diversity and abundance the genus is best represented in southern Australian waters suggesting that the genus had its origin in this region. The relatively few and isolated records in tropical waters suggest a northward migration perhaps facilitated by eddies and localized near-shore currents that avoid the predominant north-south flowing currents along the Australian coastline; the East Australian current and the Leeuwin current along the west coast.

Meridionale dubia is based on subadult specimens of what may now be a described species. Based on our present limited knowledge and because of the dramatic morphological changes that take place between the subadult and adult stages it will be difficult to establish the true identity of these forms on which this species was based. The status of this species would best be resolved by molecular means but given the age and small size of the specimens this may not be achievable. The species is assigned to species inquirenda.

Meridionale laevis was well described by Hoek but the opportunity is taken here to record additional observations and to provide images of the holotype. Re-examination of the type specimens and additional material also enables further comments on M. laevis, M. ambigua, M. harrisi and M. tasmania.

Distribution. Moreton Bay, Queensland; the southern and western Australian coastline from Tasmania to Ningaloo reef in north-western Australia.