Crossaster japonicus Fell 1958

The significance of Crossaster japonicus and Northern Hemisphere species

Fell (1958) identified sufficient similarity between Crossaster multispinus and the North Pacific Crossaster japonicus (Fisher, 1911) to argue that the latter was a synonym of the former. This was met with disagreement by Rowe & Gates (1995) who returned the two species to their original status. O’Hara (1998) agreed with Rowe & Gates (1995) in further retaining the two species as separate.

A phylogenetic treatment using mitochondrial and nuclear genes surveyed North Atlantic Crossaster papposus and Crossaster squamatus (D̂derlein, 1900), including exemplars of Southern Hemisphere Crossaster multispinus and Crossaster campbellicus in their analysis of Northern Hemisphere species (Ringvold & Moum 2020) concluding that they were closely related and possibly sister species. Crossaster japonicus was not among the species surveyed but has been historically considered as morphologically similar to Crossaster papposus (Fisher, 1911). In contrast Mah & Foltz (2011b) found Crossaster multispinus, Crossaster borealis, and Crossaster papposus on three separate clades suggesting that the northern and southern Crossaster species are very different from one another.

Molecular phylogenetic reviews have shown varying results when comparing asteroid species in the same genus from northern and southern hemispheres. Porania, sensu Clark & Downey (1992) included Arctic and Antarctic species. However, following phylogenetic work by Mah & Foltz (2014) this was found to be paraphyletic, including two divergent lineages resulting in the Antarctic taxon being returned to the genus Glabraster. In contrast, a phylogenetic overview of Hippasteria species (Foltz et al. 2013; Mah et al. 2014) in northern and southern hemispheres revealed that multiple species were part of a widely distributed single species.

More robust sampling of relevant Northern and Southern Hemisphere species will be necessary to more fully test relationships between lineages in order to fully determine their diversification patterns and to test the monophyly of Crossaster.

Occurrence

South Africa, Marion Island, Tristan de Cunha, Gough Islands, Bass Strait, Tasmanian coast, Southeast coast of Australia, New South Wales, Tasmania, off Cape Hawke, Western Australian coast, Macquarie Island, New Zealand. 80–1152 m.

USNM 1123438, East of Auckland Islands, New Zealand, South Pacific Ocean, −50.858, 166.7, 135– 139 m. Coll. R/V Eltanin, 19 Feb. 1965. 20 dry specs. R=5.1 r=2.0, R=3.5 r=1.7, R=4.3 r=1.7, R=4.6 r=1.8, R=4.4 r=1.8, R=3.7 r=1.7, R=3.7 r=1.5, R=5.3 r=2.3, R=2.2 r=1.0, R=1.7 r=0.8, R=1.1 r=0.5, R=1.1 r=0.4, R=1.2 r=0.4, R=1.0 r=0.4, R=1.2 r=0.4, R=0.9 r=0.5, R=1.2 r=0.5, R=1.3 r=0.5 R=0.8 r=0.3, R=1.0 r=0.3, 11 arms, R=3.4 r=1.2, R=0.8 r=0.3, 10 arms, R=3.8 r=1.6, R=0.8 r=0.4, 12 arms.

USNM 1122439, East of Auckland Islands, New Zealand, South Pacific Ocean, −50.858, 166.7, 135– 139 m. Coll. R/V Eltanin, 19 Feb. 1965. 1 dry spec. R=3.1 r=1.5, 11 arms.

USNM 1122443, Macquarie Island, New Zealand, South Pacific Ocean, −54.525, 159.025, 494− 714 m. Coll. R/V Eltanin, 10 Feb. 1965. 2 dry specs. R=1.8 r=0.7, 10 arms, R=1.0 r=0.5, 9 arms.

USNM 1122950, East of Auckland Islands, New Zealand, South Pacific Ocean, −50.858, 166.7, 135– 139 m. Coll. R/V Eltanin, 19 Feb. 1965. 1 dry spec. R= 5.2 r=2.3, 11 arms.

USNM 1521168, Hjort Seamount, Macquarie Island, −56.333, 156.483, 833– 842 m. Coll. R/V Eltanin, 12 Feb. 1965. 1 dry spec. R=1.4 r=0.5, 9 arms.

WAM Z105079, Ningaloo, Western Australia. −34.625556, 119.974444, 1074.6 m. Coll. A.M. Hosie & A. Hara, 12 Feb. 2020. 1 wet spec. R=4.6 r=1.2.

MV F270825, Baseline, Tasmanian Seamounts, Tasmania, Australia. −44.106111, 146.203611, 965− 940 m. Coll. Coll. A. Williams, A.A. Weber & R-L Erickson, CSIRO, R/V Investigator, 6 Dec. 2018. 2 wet specs. R=1.7 r=0.8, 10 arms. R=0.7 r=0.3, 10 arms.

MV F 270830, Central north Tasmanian Seamounts, Tasmania, Australia. −44.153056, 147.195, 1000−1038 m. Coll. A. Williams, A.A. Weber & R-L Erickson, CSIRO, R/V Investigator, 27 Nov. 2018. 1 wet spec. R=0.6 r=0.2, 10 arms.

MV F270824, Pedra southern Flank, Tasmanian Seamounts, Tasmania, Australia. −44.267778, 147.108889, 915−1182 m. Coll. A. Williams, A.A. Weber & R-L Erickson, CSIRO, R/V Investigator, 25 Nov. 2018. 2 wet specs. R=2.1 r=0.8, 10 arms, R=2.3 r=0.8, 10 arms.

MV F270831 Baseline, Tasmanian Seamounts, Tasmania, Australia. −44.096111, 146.679722, 560 m. Coll. A. Williams, A.A. Weber & R-L Erickson, CSIRO, R/V Investigator, 8 Dec. 2018. 2 wet spec. R=0.6 r=0.2, 10 arms, R=0.3 r=0.2, 11 arms.