The Marine Fauna of New Zealand. Squat lobsters (Crustacea, Decapoda, Chirostyloidea)

Marine squat lobsters belonging to the two superfamilies, Galatheoidea Samouelle, 1819 and Chirostyloidea Ortmann, 1892, are conspicuous elements of marine environments at most latitudes and depths. Current global diversity estimates stand at around 1300 species of galatheoids and 345 hirostyloids. The rate of discovery has not decreased in recent years; a recent book on squat lobster biology highlighted gaps in regional inventories of species, citing the New Zealand region as an example.

All species of superfamily Chirostyloidea of the New Zealand Exclusive Economic Zone (EEZ) are reviewed and inventoried from new and historical collections and revised where necessary. Collections within the National Institute of Water and Atmospheric Research (NIWA) Invertebrate Collection (NIC), the Museum of New Zealand Te Papa Tongarewa (NMNZ), Auckland War Memorial Museum Tāmaki Paenga Hira (AKM), and the Australian Museum (AM), have yielded well over 1700 catalogued specimens, some of which are from the Australian EEZ and International Waters, and from depths ranging from 20 to 2340 m. This work provides the first comprehensive monographic account of the New Zealand Chirostyloidea, spanning nearly 150 years of collections (1874–2017).

Prior to this study, 38 species from two of the four families of the Chirostyloidea were known from the New Zealand region. The New Zealand chirostyloid fauna now covers three of the four families (except Kiwaidae) and comprises 86 species in eight genera: Chirostylus Ortmann, 1892, Gastroptychus Caullery, 1896, Heteroptychus Baba, 2018, Uroptychodes Baba, 2004, Uroptychus Henderson, 1888, Eumunida Smith, 1883, PseudomunidaHaig, 1979 and Sternostylus Baba, Ahyong & Schnabel, 2018. Uroptychus nitidus (A. Milne-Edwards, 1880) is herein designated type species for the genus. Twenty-six species are new to science and 23 represent new distribution records. All available material is examined and listed, all species are illustrated, and diagnoses and keys are provided. A wider phylogenetic study of the group is under way but preliminary results of DNA barcoding are used as a molecular taxonomy tool and discussed.

Chirostyloidea are typically associated with other macroinvertebrates, most commonly with large antipatharians or alcyonaceans and occasionally sponges, which are usually concentrated on marine habitats such as seamounts or deep-sea ridges. Some of their life history characteristics (abbreviated larval stages for three of the four families) and their evident resource-association have been linked to increased range restrictions and potentially higher rates of diversification than for galatheoids.

As expected, the New Zealand chirostyloid fauna shows a close biogeographic affinity with that of the tropical south-west Pacific and eastern Australia. A few species are widespread in the Indo-West Pacific and over 40% are currently considered endemic. Results of the present study demonstrate a considerably higher species richness than previously known for the New Zealand EEZ, more than doubling the known fauna of the region. Many global regions remain entirely or partially unstudied, implying that a huge potential for species discovery remains. The New Zealand region is comparatively well-sampled, although some areas remain unstudied. It is suspected that only a small number of species might be added to the regional chirostyloid diversity in the future. Major work remains, however, with the inventory of outstanding Galatheoidea squat lobsters.