The New Zealand Natant Decapod Crustacea; Systematics, Distribution and Relationships

Abstract

Sixty-two species are recorded from the New Zealand region, here defined as the North, South and Stewart Islands, the Chatham Islands and the New Zealand Subantarctic Islands. Thirty-three of these are new records added as a result of this study, ten being described here as new species. Hymenopenaeus sibogae, Aristaeomorpha foliacea, Gennadas gilchristi, G. kempi, Sergestes cf. S. seminudus, S. potens, S. japonicus, Pasiphaea notosivado, P. barnardi, Rhynchocinetes ikatere, Acanthephyra quadrispinosa, Systellaspis debilis, Notostomus cf. N. westergreni, Campylonotus rathbunae, Periclimenes youngi, P. bathamae, P. alertae, Processa moana, Hippolyte multicolorata, Ogyrides delli, Plesionika martia, Parapandalus costelloi and Pontophilus indicus are new to the New Zealand fauna, while species of Alpheopsis, Alpheus, Sclerocrangon (2), Pontophilus (4), Prionocrangon and a genus and species of Bresilioida are described as new. The family Rhynchocinetidae is amended to take the new bresilioid genus, and a new genus is proposed for Pandalus magnoculus Bate, thus leaving Pandalus as a restricted, northern hemisphere genus. The caridean families Pasiphaeidae, Campylonotidae, Processidae and Ogyrididae are new to the fauna. Three families, the Sergestidae, Alpheidae and Crangonidae are studied in particular detail. In the Sergestidae, Sergestes potens and S. japonicus are uniform scarlet species without internal luminescent organs (organs of Pesta) and are referred to the subgenus Sergia, here formally defined. Sergestes arcticus and S. cf. S. seminudus are parti-coloured red and transparent species which possess organs of Pesta and are referred to the subgenus Sergestes s.s. here formally defined. A synopsis of the 57 species recognised in Sergestes is given. The Alpheidae is now represented by five species, the shelf genus Alpheopsis being new to the fauna. Betaeus aequimanus, Alpheus socialis and A. novaezealandiae are redescribed, the latter being an Australian species taken in the Auckland area, but not seen from New Zealand for 50 years. All recent references to A. novaezealandiae refer to a new species of Alpheus common in the northern mangrove swamps. Two cases of natural reversal of chela asymmetry in A. socialis are interpreted as modifications of small chelae towards the specialised form of the large chela in response to the loss of the large chela on the opposite side. Sclerocrangon and Prionocrangon are archibenthal genera new to the New Zealand Crangonidae. Pontophilus with 9 species is now the largest genus in New Zealand, new species being described in the groups with two dorsal carapace spines and three dorsal carapace spines respectively, while a new group with four such spines is represented by a further new species. Pontophilus australis, P. chiltoni, P. pilosoides, P. indicus and Pontocaris lacazei are redescribed, but Pontophilus challengeri was not represented in the material available. The new species of Prionocrangon is a blind, white, burrowing form with a specialised filter-feeding mechanism. The colour in life of 24 species is recorded in detail and colour notes made from preserved specimens are given for a further nine species. The distribution of pigmented photophores is described in the bathypelagic species Gennadas gilchristi, G. kempi, Sergestes potens, Oplophorus novaezeelandiae and Systellaspis debilis. In addition to the possession of dermal photophores, O. novaezeelandiae was observed in life to eject a luminous 'cloud' of material anteriorly with the exhalent branchial current. Of the seven species which occur in New Zealand, intertidal waters, five (Palaemon affinis, Betaeus aequimanus, Alope spinifrons, Hippolyte multicolorata and Alpheus socialis) appear to be widely distributed throughout the country, but two are restricted in their geographic distribution to particular marine provinces. Thus the abundant, burrowing, new northern Alpheus characterises the Aupourian province, while Nauticaris marionis in the intertidal is characteristic of the subantarctic Antipodean province. Three shelf species (Hippolyte bifidirostris, Pontophilus australis and P. chiltoni) appear to be restricted to shallow water of less than 10 fathoms, while the shelf proper has a fauna of at least 23 species, with seven of these of these (Solenocera novaezealandiae, Aristaeomorpha foliacea, the new Processa, Rhynchocinetes balssi, the new Rhynchocinetes, the new Parapandalus and Pontocaris lacazei) apparently restricted to the Aupourian marine province. Five commercially usable species are suitable for investigation as the basis of a fishery. Aristaeomorpha foliacea from the shelf and slope of the North Auckland west coast, the new Parapandalus from the Bay of Plenty shelf, Hymenopenaeus sibogae from the Bay of Plenty continental slope, Sergestes potens from Cook Strait deep waters and Campylonotus rathbunae from deep waters off the east coast of the South Island, are all large forms similar to proved commercial species in other parts of the world. Disregarding the 17 oceanic species in the New Zealand check-list, the 45 benthic species are made up of 73% endemic forms, 9% virtually cosmopolitan, 7% wide-ranging Indopacific, 7% restricted Australasian, 2% Eastern Pacific and 2% subantarctic species. Taking the 32 intertidal and shelf species alone, the endemicity in the benthic group increases to 81%. Our immediate systematic relationships appear to be primarily with the Australian fauna and to a very small extent with a circum-subantarctic fauna, while our ultimate systematic relationships are clearly with the general Indopacific fauna. The archi-benthal assemblage, with Sclerocrangon, characteristically an arctic and northern temperate genus, associated on the Chatham Rise with the equatorial genus Prionocrangon, is unique from the generic points of view, at least in the Southern Hemisphere.