the common name for cumaceans alludes to one of their distinctive features, i.e. resemblance to a comma when preserved. that is, they have an enlarged front section (head and part of the thorax) followed by a rather narrow posterior section (remainder of thorax and abdomen).
comma shrimps live on the seafloor with their bodies generally slightly submerged in the sediment. they feed on diatoms, pieces of seaweed, foraminiferans, and detritus, which they collect from the sediment surface. For the most part, they will stay hidden in the sediment during the day, and some will make extended trips into the overlying water after sunset. the reasons for these excursions are not precisely known, but include moulting and searching for mates. in fact, in some cumacean families, the body morphology of the mature male is completely modified for swimming, suggesting that at that stage the animal rarely visits the sediment. Swimming cumaceans are vulnerable to fish predation, and mature males are commonly found in fish stomachs.
the cumacean body is one of the more modified of the higher crustaceans.
anteriorly, the head and three segments of the thorax are covered with a carapace.
as a result, the normal feeding appendages of the head are augmented by three thoracic appendages (known as maxillipeds) that are also used for feeding. the first of these is also highly modified for respiration. that is, the epipod, which is not present in amphipods and is reduced in isopods, is greatly enlarged in cumaceans as a branchial lobe. Respiration occurs as the branchial lobe is moved back and forth underneath the sides of the carapace.
the remaining thoracic segments bear appendages that function as walking legs. in some cases, especially in mature males, these legs will also have an outer branch, the exopod, that is used to aid in swimming. the abdomen is generally long and thin. abdominal appendages are either pleopods, if they occur on one or more of the first five segments, and uropods when present on the last segment. pleopods are not present in the females of species that occur in New Zealand, and may or may not be present on some or all segments in the males. a final, post-abdominal segment, the telson, may be present as a separate structure, or it may be fused to the last abdominal segment.
cumaceans are rare in the fossil record. there are two species known from the Jurassic, but they are more or less similar to a modern cumacean family, suggesting that the group as a whole is quite old. On the other hand, cumaceans are among the last of their line to have evolved, so it possible that all peracarids were present by the end of the paleozoic.
as with other members of the superorder peracarida, cumaceans carry their young in a brood pouch, with the young hatchling looking like a miniature version of the adult minus the last pair of thoracic legs. Because of this direct development, cumacean species are generally not very widespread, and some genera are restricted to individual continents or ocean basins. Some families, such as the Bodotriidae and Nannastacidae, are primarily warm-temperate to tropical, while others such as the lampropidae and diastylidae are most diverse in colder oceans. all families are represented in the deep sea, but lampropids show the greatest diversity in that environment.
New Zealand cumacea
the first cumaceans known from New Zealand were described by George thomson (1892), who had spent a couple of days dredging in the Bay of islands in 1883. Not being able to sort the material for some time, his two species went undiscovered for several years. it would be another decade before Zimmer (1902) would describe an additional two species, collected by prof. dr thilenius from the Bay of plenty and deposited in the Berlin museum. the biggest contribution, to this day, of our knowledge of New Zealand cumaceans was made by W. t.
calman, who, over a 10-year period (calman 1907, 1908, 1911, 1917), described 17 species from material sent to him by G. m. thomson and henry Suter. Norman Jones, a prolific cumacean worker, described a new species and added a new record from the chatham islands area (Jones 1960). he added five new species and two new records to the New Zealand fauna in his now classic monograph covering material in the collections of the former New Zealand Oceanographic institute (now part of NiWa), the Zoology departments of auckland and canterbury Universities, and the then dominion museum, Wellington (Jones 1963). a further eight deep-water species were described by Jones (1969) from material collected in the tasman Sea by the Galathea Expedition.
Over the intervening 31 years, many samples containing cumaceans have been taken in the waters of New Zealand’s EEZ and stored in the NiWa invertebrate collection, Wellington. Until this present review, no one had taken the challenge of working up this material. most of the new material examined was collected in the deep waters of the New Zealand microcontinent and contains much that is new, both at species and genus levels. From these collections, four new species of Gynodiastylidae were found and described in a recent monograph of the family by Gerken (2001). Several other new taxa have been sorted from the collections and will be described in future papers.
Of the eight currently recognised cumacean families, only six are represented in New Zealand waters. (the ceratocumatidae is known only from abyssal depths in the atlantic and indian Oceans and the pseudocumatidae are so far exclusively Eurasian–atlantic in distribution.) the Gynodiastylidae is the smallest of the families represented in New Zealand, with only seven species, and the diastylidae the largest, with 19 species formally known (and at least another six species remain to be characterised). Some remarks are now offered for each family, based on historical records as well as new findings from NiWa material.
Family Bodotriidae: Subfamily Bodotriinae. members of this subfamily occur in all oceans, primarily in shallow water, but also in the deep sea. New Zealand is quite unusual in having only one (Cyclaspis) of the 13 genera represented in its fauna. this is most likely because the other genera are primarily warm-water and have invaded temperate waters only at the edges of their distributions.
Because of the long isolation of the New Zealand microcontinent, temperate-water invasion would have been difficult. On the other hand, Cyclaspis is found in tropical to cool-temperate shelf waters as well as the cold waters of the deep sea, so its radiation in New Zealand waters might be expected. the level of endemicity is high in absolute numbers, but species in this genus are usually found in one, maybe two, zoogeographic provinces. Few new species are likely to be found in shelf waters, with most additions to the fauna coming from bathyal depths. if another genus is to be added, it will most likely be something completely new.
Family Bodotriidae: Subfamily Vaunthompsoniinae. this subfamily is largely austral in its distribution and is found from tropical-shelf habitats to cold bathyal waters. Only one New Zealand shelf species is known, and it is not endemic.
One of the two bathyal species is endemic, as are both abyssal species. it is unlikely that more than one or two additional shelf species will be found, but the deep-water fauna could continue to contribute new genera and species.
Family Diastylidae. Of the seven genera represented, one (Colurostylis) is
Some New Zealand representatives of cumacean families.
Bodotriidae: A (female), B (male), Cyclaspis elegans; c (female), D (male), Cyclaspis thompsoni.
Diastylidae: e (female), Diastylis acuminata (Diastylidae); F (female), G (male), Colurostylis pseudocuma.
Gynodiastylidae: H (female), Gynodiastylis milleri. Lampropidae: I (female), Hemilamprops pellucida.
Leuconidae: J (female), K (male), Paraleucon suteri. Nannastacidae: L (female), Campylaspis rex; M (male), Nannastacus pilgrimi.
A–K, M, from Jones 1960; L, from Gerken & Ryder 2002
endemic. the others are broadly distributed in the colder waters of the world ocean. the genera Makrokylindrus and Vemakylindrus are exclusively bathyal or deeper. Specific endemicity is very high (18 of 19 known species) for this family considering the widespread nature of the genera. in addition, diastylids are very abundant and at least one or two individuals can be found at any benthic sampling station.
Family Gynodiastylidae. this is a predominantly southern hemisphere family (but ranges as far west as the persian Gulf and east to Japan) and exhibits its greatest radiation in southern australia. there are seven endemic species in New Zealand shallow waters, of which three are in the widespread genus Gynodiastylis.
One of the new species, in the genus Allodiastylis, was found at bathyal depths.
Family Lampropidae. the lampropids are a worldwide, cold-water, primarily deep-sea group. the taxonomy of the family is in need of serious revision, so some of the species found in the current study may be assigned to new endemic genera when revision is completed. prior to this study only one lampropid, Hemilamprops pellucidus, was known from New Zealand. it is a widely distributed southern hemisphere species. Bathyal waters, however, have so far produced eight new species and one new genus (Gerken 2010), suggesting that the chatham Rise and campbell plateau have much higher-than-average lampropid diversity.
Family Leuconidae. this family has very high generic endemicity (three of six genera) in New Zealand, especially in shelf waters. Further, the endemic genera are morphologically advanced within the family, anchoring a group (clade) where the male second antenna becomes reduced in length and modified so it can be used to grasp the female during mating. this trend continues in other eastern pacific genera, with the second antenna possessing a more complete grasping structure in one Japanese genus and finally culminating in a western North american slope-dwelling genus where the grasping structure is all that is left of the appendage. all species of leuconids are endemic, with the single exception of Eudorella truncatula, which is surely an introduced species, broadly distributed in the North atlantic and North pacific. this family does not seem to be well represented in New Zealand bathyal samples, in contrast to what is seen in northern hemisphere waters.
Family Nannastacidae. there are two groups of genera in this family in New Zealand – deposit-feeding Cumella and its relatives and carnivorous Campylaspis and its relatives. Of the deposit-feeders, only one genus, Scherocumella, has been found in shallow waters, and two genera were found in the bathyal samples. this group seems to be under-represented in New Zealand. in contrast, there are at least six species of the carnivorous genus Campylaspis and two of Procampylaspis.
the radiation within these genera is typical of that seen in other shelf and slope cold-water environments in both northern and southern hemispheres.
all species in this family are endemic. the finding of a species of Styloptocuma extends the range of this genus into the pacific.
in summary, there are two groups of cumaceans in the New Zealand fauna – the highly endemic species and genera of shallow water and the continental shelf, and the bathyal and abyssal species that belong to genera and families that are widespread throughout the cold deep waters of the world. Notably, within one family, the leuconidae, there has developed a specialised morphology among the males that seems to have spread northwards in the eastern pacific, culminating in advanced forms in Japan. Finally, New Zealand lacks representatives of many warm-temperate genera, even though it has a warm-temperate zoogeographic province and the Kermadec islands within its EEZ. this may be a consequence of the geological history of the microcontinent, which, after it became isolated, went through a cooling period, thus eliminating resident warm-water species.
Gaps in knowledge of New Zealand cumacea
the cumacean fauna of New Zealand’s EEZ currently comprises 31 genera (two not yet named) and 74 species, not all formally named. Of these, about half, i.e.
15 genera and 37 species, are from shelf waters. in 1999, a brief collection by les Watling in a few areas of the North and South islands produced one new species of Colurostylis. additional collecting is probably not likely to result in the addition of more than 10 new species from shelf depths, with the possible exception of Stewart island and the subantarctic islands, which so far remain unexplored with respect to cumaceans. the relatively few samples (ca. 15) obtained by Watling have so far yielded 31 new species and two new genera, with the diastylidae still to be studied in detail. None of the species in the new NiWa and Watling samples can be matched to the eight species Jones (1969) described from the tasman Sea, suggesting either that there is a high level of endemicity between the east and west deep waters of New Zealand or that the deep-water fauna is very diverse. Neither of these hypotheses is unlikely. Because they brood their young, cumacean species are highly restricted to zoogeographic provinces in shallow water, and may well be restricted to individual tectonic plates in deep water. Since cumacean diversity is generally highest in the Southwestern pacific, one might expect the overall diversity of bathyal waters to be much higher, at least by a factor of two, than that which has been observed to date. in addition, the lack of correspondence between the shallow New Zealand and southern australian faunas lends credence to the fact that there is little natural water-borne transport of cumaceans. most likely the shelf-dwelling cumaceans of New Zealand evolved in situ from whatever stock was present after Zealandia (the New Zealand continental mass) separated from antarctica about 56 million years ago.