Maoricolpus murrayanus ( Tate, 1885 )

Maoricolpus murrayanus ( Tate, 1885) View in CoL

Figure 4A–F View FIGURE 4

Pattern description. Yellow-orange fluorescence. Entirety of shell covered by banded axial waves. Waves are irregular in shape, sometimes connecting to the adjacent wave and other times remaining separate. The waves on each whorl do not align with adjacent whorls, i.e., they are not continuous. Frequently the posterior of the whorl will show a dashed checkerboard-like pattern (arrowheads in Figure 4A, D View FIGURE 4 ), rather than the continuation of the thicker main waves ( Figure 4E, F View FIGURE 4 ). There is also occasionally partial pigmentation in the spiral striae, separate from the main patterning. The inner lip fluoresces solidly.

Comment. The extinct M. murrayanus is morphologically very similar to extant Maoricolpus roseus . The original description of M. murrayanus by Tate (1893a) differentiated it from M. roseus by only “the spiral ornament of the posterior whorls develops into ribs on the anterior whorls”. Garrard (1972) proposed there are strong grounds for considering M. murrayanus and M. roseus as synonymous due to the high morphological similarities. Whilst the protoconch was not preserved in the specimens in this study, the protoconch of both species has previously been described as multispiral, with three to four microscopic flatly globose whorls, apparently sinusigeroid (Garrard 1972). The main argument presented for not synonymising the species is the differing age and geographical ranges (Beu 2009). M. roseus is one of two extant species in the genus Maoricolpus , together with Maoricolpus finlayi . Both are natively endemic to New Zealand, but M. roseus is much more common and has a wider distribution ( Powell 1940; Donald and Spencer, 2014). M. roseus is now a dominant species in New Zealand waters, often the most dominant benthic species present (McKnight, 1969). This is like what is observed in M. murrayanus in the Murbko Marl—it is the most common species present ( Figure 3D View FIGURE 3 for abundance). M. roseus has been anthropogenically introduced to the east-coast of Australia, arriving in Tasmania in the 1920s and now found as far north as Botany Bay (Gunasakera et al., 2005). It is now considered a pest in Australian waters (Bax et al., 2003). M. roseus was previously separated into two subspecies, M. roseus roseus and M. roseus manukauensis , based on slight morphological variances and differences in distribution. Donald and Spencer (2014) used molecular data to conclude these subspecies were not valid, and comprised a single, morphologically variable species. M. roseus has also been merged with a fossil species, the now invalid Maoricolpus proroseus , described from Tertiary rocks of the Gisborne District in the northeast of New Zealand (MolluscaBase eds., 2023). Thus, there is a precedent for a fossil species to be combined with M. roseus . The colour patterning revealed here strengthens the argument that M. murrayanus and M. roseus are a single species with slight morphological variations through time which are insufficiently different to justify separation. The patterns on each species show banded axial waves. Both species show a variability in the presence of a checkerboard-like pattern towards the outer end of the whorl, as described above. This seems to be more commonly present on M. murrayanus than M. roseus but is present on specimens such as the ones in Figure 4H, I View FIGURE 4 .

Essentially all 387 specimens of Murraycolpus murrayanus studied fluoresced very strongly. Unlike most of the other taxa, no bleach treatment was applied to the photographed M. murrayanus specimens as trials found no benefit due to the already highly fluorescent condition.

In situ observation of M. murrayanus underneath UV light also displayed clear fluorescence when viewed in weak shade (see Supplementary Figure 1 View FIGURE 1 ).

Several specimens were found to partially retain the original pigmentation. The most intact of these specimens ( Figure 4F View FIGURE 4 ) shows clearly defined pigmentation on the body whorl and first two spire whorls. The pigment is only present on the photographed side, while the side of the shell with the aperture lacks pigment, likely due to sun exposure. The other shells show a much fainter and smaller area of partial pigmentation. The fluorescence is not as strong in the partially pigmented specimens as it is in the non-pigmented specimens. The shells of modern relative M. roseus do not fluoresce under UV light.