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Zooplankton of Wellington Harbour, New Zealand

Decapoda

Decapoda

S.O. Natantia

Natant decapod larvae of both oceanic and shallow water origin occur regularly in the Wellington Harbour plankton. These larvae could not be identified with certainty beyond genus and the only reference of value is the reports of the "Terra Nova" (1910) Expedition: "Decapod Larvae" by Gurney, 1924.

Oceanic larvae of the following genera have been obtained:

  • Processa 1sp.
  • Pontophilus 2spp.
  • Sergestes 1sp. (Text-fig. 4, E)
  • Pandalus 2spp.
The larvae of Sergestes sp. occur rarely from July to September, but are absent for the remainder of the year (Text-fig. 7). The larvae of two species of the genus Pandalus occur rarely throughout the year (Text-fig. 7). Early stage Pandalus larvae are more common in October and November, and again in April page 10
Text-fig. 4.—Fig. A, Euphasid larva: 5th "Furcilia" stage. Fig. B, Cirripede Nauplius larva. Fig. C, Heterosquilla spinosa (Wood-Mason): Stage 5 larva. Fig. D, Squilla armata Milne Edwards: Stage 2 "Alima" larva. Fig. E, Sergestes sp.: Late larva.

Text-fig. 4.—Fig. A, Euphasid larva: 5th "Furcilia" stage. Fig. B, Cirripede Nauplius larva. Fig. C, Heterosquilla spinosa (Wood-Mason): Stage 5 larva. Fig. D, Squilla armata Milne Edwards: Stage 2 "Alima" larva. Fig. E, Sergestes sp.: Late larva.

page 11 and May. These oceanic larvae were more abundant in samples taken during a flooding tide and during southerly winds which blow directly into the harbour from the Cook Strait area.

Larvae of shallow water decapod Natantia were common within the harbour, and again these larvae could not be placed with certainty in any genus.

S.O. Reptantia
Section Palinura

Adults of Jasus edwardsi (Hutton, 1875) (according to Holthius (1963)— syn. J. lalandei) are found at Kau Point. Small numbers of first stage Phyllosoma larvae attributed to this species (Text-fig. 5, A) are rare in the September plankton but are absent for the remainder of the year. Later stage Phyllosoma larvae were not found. Dr Pike (Mar. Dept. pers. comm.) has found that "berried" females of J. edwardsi from Island Bay, Wellington, begin to liberate their larvae early in August, and about half the females are spent by the beginning of October. The appearance of first stage Phyllosoma larvae in Wellington Harbour in September agrees with these observations. Jasus edwardsi is the only known representative of the Palinura recorded in Wellington Harbour. Jasus verreauxi (Milne Edwards) is not known to breed as far south as Wellington (Pike, pers. comm.).

S.O. Reptantia
Section Anomura

Larvae of about 18 species of Anomura are found in the Wellington Harbour plankton. Many of these have been identified in the following families:

Galatheidae : ?Munida Leach, 2 or 3 spp.
Porcellanidae : Petrocheles spinosus Miers.
Petrolisthes novaezelandiae Filhol.
Petrolisthes elongatus (Milne Edwards)
Axianassidae : 2 spp.
Laomediidae : Jaxea Nardo, 1 sp.
Callianassidae : Callianassa filholi Milne Edwards
Paguridae : 5 spp.

The larvae of this section (Anomura) are more abundant than those of any other section of the Decapoda, and occur with greater regularity.

Family Galatheidae

The family Galatheidae is represented by two or three species probably belonging to the genus Munida Leach. These occur in the plankton rarely from August to November and in March and April. No larvae were obtained in the intervening months. As the larvae were taken mainly on the flood tide they were probably carried into the harbour by the incoming oceanic water.

From Lebour (1930) the larvae were readily identified as belonging to the Family Galatheidae and probably to the genus Munida, but they possessed features differing from those of the typical Munida larvae and rather more characteristic of the genus Galathea Fabricius.

The first species, of which a stage five (final stage) zoea larva measuring 6.5mm in length has been illustrated (Text-fig. 5, B) has a rostrum with a much broader base than is usual for Munida, and it is rather more typical of Galathea. The antennal scale is also more like that of Galathea, and is shorter and broader than in known Munida larvae. On the other hand the telson is longer and narrower and has more posterior setae than is usual in either Munida or Galathea larvae.

A stage four larva obtained from the Wellington plankton is very similar to the illustrated stage five larva. However this larva measured only 3.8mm in length. A length increase of 2.7mm is hardly possible in successive larval stages, so it is page 12
Text-fig. 5.— A, Jasus edwardsi (Hutton): Stage 1 "Phyllosoma" larva. Fig B, ?Munida sp.: Stage 5 zoea larva. Fig. C, Axiid larva: Stage 2 zoea. Fig. D, Jaxea sp.: Stage 1 zoea larva.

Text-fig. 5.— A, Jasus edwardsi (Hutton): Stage 1 "Phyllosoma" larva. Fig B, ?Munida sp.: Stage 5 zoea larva. Fig. C, Axiid larva: Stage 2 zoea. Fig. D, Jaxea sp.: Stage 1 zoea larva.

page 13 probable that these two larvae are of different species belonging to the same genus. However they have not been separated for the purposes of this study.

The second species from the Wellington plankton has a rostrum and antennal scale rather more typical of Galathea than of Munida, but the long slender shape of this larva and the form of its telson identify it with the genus Munida.

Hence, when obtained, the adults of these larvae will also have characters that differ appreciably from the typical Munida gregaria which is so plentiful in the outside deeper water fauna. The early post larva of this species occurs in dense swarms in the Tory Channel area and around Banks Peninsula in December. Its larvae should therefore be present in abundance some three months earlier (September and October). The breeding season of M. gregaria and the two (probably three) species from the Wellington Harbour should therefore coincide. The larvae of M. gregaria have been described by Rayner (1935), and the species given here certainly do not compare with these. As M. gregaria appears to be the only species of Munida recorded for New Zealand, the Wellington larvae must belong to an unrecorded species. However when fully identified these larvae could conceivably belong to a genus other than Munida.

During the Victoria University of Wellington deep water biological investigations in Cook Strait (1954-1957) adults of eight or nine galatheid species representing the genera Munida, Galathea and Uroptychus Henderson, and possibly several unknown genera were collected. None of these have yet been described. From the Bay of Plenty, Pike (pers. comm.) has recorded the genus Munidopsis Whiteaves, as well as species of Munida, Galathea, and Uroptychus which were not obtained during this University's work in Cook Strait. Hence there are four or more genera and twelve or more species of Galatheidae occurring in New Zealand waters which have not been described as adults. Of these the larvae of Munida gregaria only are known (Gurney, 1939; Zoo. Rec. 1940–).

Family Porcellanidae

The zoea larvae of Petrocheles spinosus Miers, Petrolisthes novaezelandiae Filhol and Petrolisthes elongatus (Milne Edwards), with their enormously long rostrum and posterior carapace spines, are among the most distinctive decapod larvae in the plankton. The larvae of these three species have been described in detail (Wear, 1964a, 1964b, 1965).

Petrocheles spinosus larvae are present from July through to January of each year. However these larvae are rare (Text-fig. 7) and occur only in some samples.

The zoea larvae of Petrolisthes novaezelandiae are found in the plankton throughout the year. Few larvae are recorded in August, but they are common in September and October, very common in November, December and January, and common from February through to April. However these larvae are usually rare in May, June and July (Text-fig. 7). Occasional tows may catch P. novaezelandiae larvae in great abundance, especially during November and December.

Petrolisthes elongatus zoea larvae first appear in September, but they are rare from this month until the end of November. Few larvae are recorded in December and January, but they are common in February and rare in March. From April to August they are not recorded (Text-fig. 7).

Family Axianassidae

Two species of axiid larvae were recognised in the Wellington plankton.

The first species (Text-fig. 5, C) is rare in August and October, and is common only in September. It is absent for the remainder of the year. This larva compares with a larva described by Gurney (1924, p. 149, fig. 59, c, d, e) which was taken in considerable numbers from Three Kings Islands, and from Spirits Bay, near North Cape. Gurney was unable to place this larva in a genus.

page 14

The second species is represented by a few larvae in October and November samples from Wellington Harbour, but in December they are rare. This larva is not recorded for the remainder of the year. This species is very similar to two species described by Gurney (1924) from Three Kings Islands and the Bay of Islands. Gurney has provisionally identified these larvae as Iconaxiopsis sp., and the second species from Wellington Harbour is sufficiently similar to these to warrant its inclusion in the genus Iconaxiopsis.

There have been no adult Axianassidae described from New Zealand waters.

Family Laoemediidae

One of the most common and conspicuous larval decapod species in the summer plankton is the striking, long-necked, Lucifer-like larva to which the name of "Trachelifer" was given by Brook (1889). "Trachelifer" larvae were taken from the Bay of Islands by the "Terra Nova" Expedition of 1910, and these were assigned by Gurney (1924) to the Family Laoemediidae on the basis of their resemblance to the larvae of Jaxea nocturna (Chierghin), and attributed to the genus Jaxea Nardo. Larvae caught in Wellington Harbour (Text-fig. 5, D), when reared, moulted to a juvenile of the genus Jaxea having adult features of this genus.

The larvae of Jaxea sp. first appear rarely in September and few are recorded in October and November. They are abundant in December and January, common in February, and rare in March. From April to August these larvae are not found in the plankton (Text-fig. 7). A single 20 minute horizontal plankton tow in late December or in January may produce over 5,000 "Trachelifer" larvae. During these two months considerably fewer larvae were found in occasional samples from other areas in the harbour. The abundance of first and second stage larvae caught at Stations One and Two suggests that adults are present in considerable numbers in the substrate of Kau Bay and Mahanga Bay.

No adult species of Jaxea have yet been described from New Zealand waters. However, Pike (pers. comm) has obtained an undescribed Jaxea in 40 fathoms to 90 fathoms in several North Island localities. I also obtained seven adults from Evans Bay, Wellington Harbour, in July, 1964. Five of these were caught at night in an otter trawl in soft mud at a depth of six fathoms, and the remaining two were taken from the stomach of a male dogfish (Mustelus antarcticus). The characters of the juvenile reared from Wellington larvae compare closely with those of the adult species obtained by me and by Dr Pike.

Family Callianassidae

Callianassid larvae from the Wellington Harbour plankton (Text-fig. 6, A) were identified as Callianassa filholi Milne Edwards by hatching first stage larvae from an ovigerous female. Later stage larvae were obtained from the plankton and reared through to the juvenile stages. A few of these larvae first appear in the July plankton. They are very common in August, abundant in September, and very common from October through to late December. They are still common in January but rare in February and March, and absent from April to June (Text-fig. 7).

C. Devine (pers. comm.) in his M.Sc. thesis studies on C. filholi at New Brighton, Christchurch, in 1962, found adults of this species only between the high and low tide marks. I found no evidence of adults living intertidally on Scorching Bay, or on any of the smaller sandy beaches on the western side of Wellington Harbour. Small populations of C. filholi are known to occur on the sandy beaches of the eastern side of the harbour. However in August and September, early stage larvae occur abundantly at Stations One and Two, usually in large swarms, and it is improbable that these are liberated on the eastern side of the harbour. Relatively few larvae were found in plankton samples from other page 15 harbour localities. Hence the possibility of C. filholi favouring a sub-littoral habitat in Wellington Harbour must now be considered.

Callianassid Crustacea have been recorded from most of the oceans and from habitats which range from 400 fathoms to between the tide marks (de Man, 1928). Habitat varies considerably from species to species. Hailstone and Stephenson (1961) found that C. australiensis was strictly intertidal, and Dahl (1953) found the intertidal habitat to characterise the genus. However, Gustafson (1934) records that C. subterranea in the Gullmar fjord, Sweden, is restricted to depths of 30 to 35 metres.

Family Paguridae

Our knowledge of the systematics of the New Zealand Paguridae is still confused, and relies mainly on the work of Filhol (1885). This family is badly in need of revision before the adults can be identified with certainty. Dawson (Oceanographic Inst.) and Pike (Mar. Dept.) have informed me (pers. comm.) that Dr Forest (Paris) is at present revising the New Zealand Paguridae, and much of the material is in his possession pending publication.

Characters of pagurid larvae are given by Gurney (1924, p. 182), MacDonald, Pike and Williamson (1957), and Pike and Williamson (1959). As in all decapod Crustacea, larval forms provide a very valuable indication of the number of distinct species, and preliminary work has resulted in the recognition of five pagurid species in the Wellington Harbour plankton. Three of these species occur commonly from September to December and again in April and May, but are rare for the remainder of the year. A fourth species is common in October and November only, and the fifth species is rare and occurs only during the spring (September to November). However the family Paguridae is represented in the plankton all the year round (Text-fig. 7). One of the three more common species is illustrated (Text-fig. 6, B) and is a larva of the "Pagurus bernhardus" type (MacDonald, Pike, and Williamson, 1957, pp. 219–226, figs. 2, 3).

Three species of zoea larva were reared in the laboratory to the megalopa stage, which in the Paguridae is known as the "Glaucothoe" larva. One of these survived to the first juvenile hermit stage but this lacked sufficient adult characters for identification.

S.O. Reptantia
Dromiacea

"The systematic position of the Dromiacea has, on the evidence of adult anatomy, been a subject of considerable difference of opinion, and they have been associated on the one hand with the Anomura and on the other hand with the Brachyura" Gurney (1924, p. 188).

Gurney (1924, 1942), Lebour (1934), and Pike and Williamson (1960), consider that the Dromiacea must be removed from the Brachyura with which they are currently classified. However the Dromiacea are difficult to place in the Anomura and cannot be placed in the Thalassinidea. Pike (1947) from detailed anatomical comparisons with Anomura, Dromiacea, and Brachyura, and Gurney (1942) both derive the Dromiacea from "the anomuran section of the Thalassinidea". However larval evidence suggests that the Dromiacea should be separated from the Brachyura and classified as a separate group apart from the line of descent of the Brachyura.

A dromiid larva occurs rarely in the Wellington Harbour plankton in spring and autumn. It is considered to be of oceanic origin as it is more plentiful in samples from Palliser Bay and Island Bay. This larva is certainly a dromiid, but there have been no adult dromiids described from New Zealand waters. However Hale (1927) records Petalomera wilsoni (Fulton and Grant) from South Australia, page 16 and Pike (pers. comm.) has found this species in shallow water down to 40 fathoms in Tasman Bay. The generic characters of Petalomera larvae are unknown, but they will undoubtedly follow the general dromiid pattern. These Wellington larvae may well belong to P. wilsoni.

The characters of this larva support the separation of the Dromiacea from the Brachyura, and further, on the basis of several "pagurid" characters it supports Pike and Williamson (1960) who consider that the Paguridea, Galatheidea, and Dromiacea may have differentiated from a common pre-thalassinid ancestor.

This larva will be the subject of future work.

S.O. Reptantia
Section Brachyura

With the exception of the Dromiacea, all brachyuran larvae conform to a general morphological pattern which is remarkably uniform throughout the whole group (Gurney, 1924; Lebour, 1928). Basically the larvae have dorsal, rostral and paired lateral carapace spines. Variation in the form of these spines, or the absence of one or more of these spines, are the primary characters used in the separation of families and genera. Specific distinction is based on secondary characters such as the form of the telson, the spines on the abdominal segments, the length of the antennal endopodite, and the chromatophore pattern.

The high degree of endemism among New Zealand Brachyura and the lack of literature concerning the larvae of these endemic groups makes identification impossible without either hatching the eggs of identified ovigerous females, or rearing the larvae to a juvenile stage which can then be referred to an adult species. There is an urgent need for further work in this field.

The zoea and megalopa larvae of about 32 brachyuran species can be distinguished in the Wellington Harbour plankton. This is more than the number of adult species recorded for the Wellington area. The majority of these larvae could not be identified. However, the few genera and species identified belong to the following families:

Cancridae : Cancer novaezealandiae (Jacquinot and Lucas).
Pinnotheridae : Pinnotheres sp.
Pinnotheres novaezealandiae Filhol.
Hymenosomidae : Halicarcinus edwardsi Filhol.
Halicarcinus 2 spp.
Grapsidae : Hemigrapsus edwardsi (Hilgendorf).
Cyclograpsus lavauxi Milne Edwards.
Xanthidae : Heterozius rotundifrons Milne Edwards.

Among the fauna are several families and genera in common with the Plymouth fauna of the United Kingdom, possessing larval stages comparable with those belonging to corresponding Plymouth groups (Lebour, 1928). Several of the above families were identified from Lebour's descriptions, but families such as the Grapsidae and the Hymenosomidae are not represented in the United Kingdom.

Family Cancridae
Genus Cancer L.

Larvae in the Wellington Harbour plankton were identified as Cancer novaezealandiae (Jacquinot and Lucas) after rearing the megalopa larva to a juvenile crab in the laboratory. These larvae first appear rarely in July or in August, but in September and October they are common. Few larvae are recorded in November, and in December they are again rare. From April through to June this species is not recorded (Text-fig. 7).

The zoea larvae are similar to known larvae of the genus Cancer in having dorsal, rostral, and paired lateral carapace spines which are all well developed. The smooth dorsal and rostral spines are long and straight, and the lateral pair page 17
Text-fig. 6.—Fig. A, Callianassa filholi MilneEdwards: Stage 1 zoea larva. Fig. B, Pagurid Larva: Stage 3 zoea. Fig. C, Cancer novaezealandiae (Jacquinot and Lucas): Megalopa larva. Fig. D, Pinnotheres novaezealandiae Filhol: Telson of zoea larva. Fig. E, Halicarcinus sp.: Final stage zoea larva. Fig. F, Halicarcinus sp.: Telson of zoea larva. Fig. G, Hemigrapsus edwardsi (Hilgendorf): Final zoea larva. Fig. H. Heterozius rotundifrons Milne Edwards: Stage 1 zoea larva.

Text-fig. 6.—Fig. A, Callianassa filholi MilneEdwards: Stage 1 zoea larva. Fig. B, Pagurid Larva: Stage 3 zoea. Fig. C, Cancer novaezealandiae (Jacquinot and Lucas): Megalopa larva. Fig. D, Pinnotheres novaezealandiae Filhol: Telson of zoea larva. Fig. E, Halicarcinus sp.: Final stage zoea larva. Fig. F, Halicarcinus sp.: Telson of zoea larva. Fig. G, Hemigrapsus edwardsi (Hilgendorf): Final zoea larva. Fig. H. Heterozius rotundifrons Milne Edwards: Stage 1 zoea larva.

page 18 are straight but shorter. The antennal exopodite is about one-third the length of the spinous process, and the telson has two lateral spines in all zoeal stages. The megalopa larva (Text-fig. 6, C) is characterised by its long, posteriorly-directed dorsal carapace spine, eight setae on the last pair of pleopods, and long setae on the dactylopodite of the fifth pair of pereiopods.
Family Pinnotheridae
Genus Pinnotheres Latreille

Larvae of two species of this genus are found in the Wellington plankton. These larvae are rare in August, few in September and October, and common in November. Few larvae are recorded in December and January, and by February and March they are again rare. From April to July no Pinnotheres larvae were found in the plankton (Text-fig. 7).

The zoea larvae of the genus Pinnotheres are characterised by their very small size, their great reduction or absence of carapace spines, and their tri-lobed telson (Text-fig. 6, D). They are very similar to the zoea larvae of the genus Halicarcinus (Text-fig. 6, E) but readily separated from these by the shape of the telson.

One of the Wellington species cannot be distinguished from the zoea larva of P. novaezealandiae Filhol described by Bennett (1964, pp. 78–79). There is therefore little doubt that the Wellington larvae are of this species. The second zoea larva is probably of P. schauinslandi Lenz, as this is the only other adult of the genus Pinnotheres recorded for New Zealand (Bennett, 1964).

Family Hymenosomidae
Genus Halicarcinus White

The larvae of H. edwardsi Filhol, and two other species of this genus occur in the plankton throughout the year. These larvae are common in July, very common in August and September, common in October, and very common in November. Few are recorded during December, but they are once more common in January and February. However, few of these larvae are recorded between March and June (Text-fig. 7).

One zoea larva from the Wellington Harbour plankton was identified as H. edwardsi by comparing planktonic larvae with larvae hatched from an ovigerous female by J. C. Yaldwyn. These hatched larvae were kindly lent to the author by Dr Pike. The remaining two planktonic larval species were very similar to the larvae of H. edwardsi, and undoubtedly of the genus Halicarcinus. A late stage zoea larva of Halicarcinus sp. is illustrated (Text-fig. 6, E).

Zoea larvae of the genus Halicarcinus are very similar in their primary characters to those of the genus Pinnotheres. However Halicarcinus zoeae are distinguished by their long, rectangular, forked telson without lateral lobes (Text-fig. 6, F). The zoea larva from Spirits Bay which Gurney (1924, p. 195) records as "Brachyura incertae sedis" was determined by Lebour (1928) as "almost certainly a Pinnixia". However, Bennett (1964) has pointed out that as adults, this genus is unknown in New Zealand, and that at present Gurney's record cannot be fully elucidated. It now seems likely that Gurney's larva is of the family Hymenosomidae, having all the primary characters shown by identified larvae of the genus Halicarcinus.

Family Grapsidae
Genus Hemigrapsus Dana

The zoea larvae of Hemigrapsus edwardsi (Hilgendorf) are rare in the September plankton, few in October, and common from November into January. Few larvae are recorded in February and March and the species is again rare in April, but absent for the remainder of the year (Text-fig. 7).

page 19

The larvae were identified by rearing a final stage zoea through to a juvenile crab. Quite remarkable success was achieved with the rearing of this species. On 1 May 1964, a reared crab was 15 months old and in the 13th juvenile crab stage. Larvae were also hatched from ovigerous females. A final stage zoea larva is illustrated (Text-fig. 6, G).

Family Xanthidae
Genus Heterozius Milne Edwards

Zoea larvae of Heterozius rotundifrons Milne Edwards (Text-fig. 6, H) are few in the plankton from November through to February. They are rare in March and April and absent for the remainder of the year (Text-fig. 7). Larvae were reared from identified ovigerous females and subsequently identified in the plankton.