The First Zoeal Stage of Campylonotus rathbunae Schmitt and Its Bearing on the Systematic Position of the Campylonotidae (Decapoda, Caridea)

Transactions of the Royal Society of New Zealand : Zoology, Volume 7, Issue 16, 25 January 1966, Page 209

The First Zoeal Stage of Campylonotus rathbunae Schmitt and Its Bearing on the Systematic Position of the Campylonotidae (Decapoda, Caridea)

R. B. Pike

D. I. Williamson

By

and

[Received by the Editor, 2 July 1965.]

Abstract

The larva of Campylonotus rathbunae, which was hatched in captivity, bears a general resemblance to some larvae of the Pandalidae and also shows a number of primitive features. Affinities with the Oplophoridae in the form of the maxillule and maxilla and in the number of thoracic exopods support the inclusion of the Campylonotidae in the Oplophoroida rather than in the Palaemonoida.

Authorities are divided on the systematic position of the family Campylonotidae, and in recent classifications it has been included in the Palaemonoida by Holthuis (1955) and in the Hoplophoroida (=: Oplophoroida) by Balss (1957). Information on larvae of the family was not previously available, but, as pointed out by Gurney (1942), “the adult anatomy is already fully known, and the larva alone can provide new evidence of relationship ”. The single zoeal stage described in the present contribution permits the first assessment of the larval affinities of the Campylonotidae.

Campylonotus rathbunae Schmitt

Campylonotus rathbunae Schmitt; Yaldwyn, 1960: 20—27, figs. 2, 3.

Adult. Three ovigerous females were trawled from a depth of about 730 m, 17.5 km east of White Island, Bay of Plenty, New Zealand, on 30 September 1962. Larvae hatched from one of these females almost immediately after capture; most of these died incompletely emerged from the pre-zoeal cuticle, but five specimens apparently representing the normal stage I zoea were obtained. None of the larvae or adults lived for more than one hour after capture.

Stage I zoea (Fig. 1).

Colour, bright orange-red; cornea of eye, black Length, 7.0-7.Bmm.

Rostrum slender, smooth, projecting more than Imm beyond eyes. Anteroventral margin of carapace without pterygostomian spine but with about 18 denticles. No other carapace spines or denticles; surface finely granular.

Abdominal somites 2-5 with dorsal part of posterior margin expanded; posterior and ventral margins fringed with large denticles. A large lateral spine on each side of sth somite; two dorsal setae on each of somites 2 and 3. Telson fairly broad, with shallow median indentation; 7 + 7 posterior processes armed with setules; posterior margin with many short spinules.

Eyes well developed, sessile. Each antennule projects beyond eye by distance about equal to length of eye. Peduncle of antennule unsegmented, smooth; inner distal margin with a stout plumed seta; outer ramus a segment, bearing three aesthetes and one plumed seta. Endopod of antenna much shorter than antennule, broad proximally and narrower distally, ending in a large plumed seta and a very short inner spine. Exopod about three times as long as broad, extending beyond antennule but not as far as tip of rostrum; indistinctly segmented at tip; no terminal spine; 2 setae on outer margin, 10 setae on distal third of inner margin (including tip). Large ventral spine at base of endopod, shorter spine at base of exopod.

Mandible with distinct molar and incisor portions and a lacinia mobilis. Maxillule with over 20 setae on coxal endite, about 14 spines and 3 setae on basal endite; palp of three distinct segments bearing 0,2, 3 setae respectively; exopod absent. Coxa of maxilla with large proximal endite bearing about 20 setae and small but distinct distal endite bearing 2 setae and a small spine; two basal endites each with about 10 setae; palp with indications of five segments, complete division between first and second, partial division between second and third, one seta at base of palp and 3,2, 1,2, 2, on respective segments; exopod bearing 29 or 30 plumed setae and terminating proximally in a stout flagellum with long setules.

Maxillipeds with endopods indistinctly segmented; that of 3rd maxilliped as long as exopod; exopods with 8, 16, 18 setae respectively. All five peraeopods distinctly biramous, unsegmented; endopods of Ist and 2nd show indications of chelae and bear a few terminal setae; other endopods and all exopods without setae. Epipods on maxillipeds but not on peraeopods; five pairs pleurobranchs distinguishable, other gills not developed.

No abdominal appendages.

Affinities of the Larva

The larva described above is large for a stage I zoea, and it is well developed with respect to the number of spines and setae on the maxillule and maxilla, the presence of large rudiments of all peraeopods and of gills. Although from a developmental point of view it is well advanced, from an evolutionary aspect it is among the most primitive of caridean larvae in that the palp of the maxillule is completely divided into three segments, that of the maxilla is incompletely divided into five segments and all peraeopods bear large rudimentary exopods which probably become functional in later zoeal stages. In spite of these primitive features there is no trace of an exopod on the maxillule.

The long slender rostrum, the fringes of denticles on the carapace and abdominal somites, the form of the mandible and the presence of a long exopod on the 3rd maxilliped are all features which the zoea of C. rathbunae shares with a number of larvae of the Pandalidae. The fringes of denticles are particularly reminiscent of the condition found in larvae of Pandalus platyceros Brandt (c.f. Berkely, 1930: 26), P. stenolepis Rathbun (c.f. Gurney, 1942: 207) and the unidentified “ Pandalidae, species 1” (Gurney, 1924: 113) ( “ Pandalid larva, species 2” Dakin & Colefax, 1940; 159). We have, indeed, seriously considered the possibility that the latter species may be a member of the Campylonotidae, but the form of the antenna, the lack of segmentation of the palps of the maxillule and maxilla and the absence of denticles on the ventral margins of the abdominal somites seem to favour its retention in the Pandalidae. The posterior peraeopods are not developed in the described stages of Gurney’s species 1 and therefore the number of exopods is not known. Not more than four pairs of exopods are present on the peraeopods of known pandalid larvae (Pike & Williamson, 1964)

Although the zoea of C. rathhunae has the general appearance of a pandalid larva, its appendages closely resemble those of larval Oplophoridae (c.f. Gurney, 1939, 1942; Gurney & Lebour, 1941). In the Oplophoridae, as in C. rathhunae, there is no exopod on the maxillule; the endites on the maxilla are developed to about the same extent in larvae of Acanthephyra A. Milne Edwards and Campylonotus Bate, and the palps of both the maxillule and maxilla are very similar in these two genera except that they are more completely segmented in the latter. The exopod of the maxilla has a stout proximal flagellum in the stage I zoea of the oplophorid genera Systellaspis Bate, Oplophorus H. Milne Edwards and Hymenodora M. Sars, as in Campylonotus. The presence in the zoea of well developed exopods on all peraeopods is a further important point of resemblance between Campylonotus and the Oplophoridae. It will thus be seen that larval characters give considerable support for grouping the Campylonotidae and the Oplophoridae in the same superfamily, as advocated by Borradaile (1907) and Balss (1957).

Holthuis (1955) grouped the Campylonotidae with the Palaemonidae and Gnathophyllidae in the superfamily Palaemonoida. Features of larvae of the Palaemonidae (c.f. Gurney, 1938, 1942; Gurney & Lebour, 1941) are that the posterior margin of the telson is never deeply indented; the antennal endopod usually ends in a short spine and a seta in stage I; the maxillule is without trace of exopod; the maxilla bears only one coxal endite; the palps of the maxillule and maxilla bear few setae, show little trace of segmentation, and are often small; exopods are absent from the sth, or 4th and sth, peraeopods; in many species one or two pairs of posterior peraeopods are longer than the anterior pairs and are developed before them. No larvae of the Gnathophyllidae are known. The form of the telson and antennal endopod and the lack of an exopod on the maxillule may be regarded as linking the zoea of C. rathhunae with the Palaemonidae, although these characters of the telson and maxillule are also common in several other families of the Caridea. The larval mouthparts of C. rathhunae are, however, much more primitive and generally very different from those of the Palaemonidae and there is a gradual decrease in the size of the peraeopods from the Ist to the sth, at least in stage I. These differences appear to preclude the possibility of close relationship between the Campylonotidae and the Palaemonidae.

Literature Cited

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Berkeley, A. A., 1930. The postembryonic development of the common pandalids of British Columbia. Contr. Can. Biol. Fish. 6: 79-163. Borradaile, L. A., 1907. On the classification of the decapod crustaceans. Ann. Mag. nat. Hist., (7) 19: 457-486.

Dakin, W. J., and A. N. Golefax, 1940. The plankton of the Australian coastal waters off New South Wales. Part I. Pubis. Univ. Sydney Dept. Zool., Monogr. I: 1-215, figs. 1-305, pis. 1-4.

Gurney, R., 1924. Crustacea, Part IX.—Decapod larvae. Nat. Hist. Rep. Br. Antarct. Terra Nova Exped. (Zool.) 8 (2): 37-202, figs. 1-78.

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1939. Bibliography of the larvae of decapod Crustacea, i-vi, 1-123. (Ray Society, London.)

1942. Larvae of decapod Crustacea ; i-vii, 1-306, figs. 1-222 (Ray Society, London).

and M. V. Lebour, 1941. On the larvae of certain Crustacea Macrura, mainly from Bermuda. /. Linn. Soc., 41 : 89-181, figs. 1-26.

Holthuis, L. 8., 1955. The recent genera of caridean and stenopodidean shrimps (class Crustacea, order Decapoda, supersection Natantia) with keys for their determination. Zool. Verh., Leiden, 26: 1-157, figs. 1-105.

Pike, R. 8., and D. I. Williamson, 1964. The larvae of some species of Pandalidae (Decapoda). Crustaceana, 6: 265-284, figs. 1-283.

Yaldwyn, J. G., 1960. Crustacea Decapoda Natantia from the Chatham Rise: A deep water bottom fauna from New Zealand. Bull. N.Z. Dept. sci. ind. Res., 139 (1): 13-53, figs. 1-10.

R. B. Pike, Zoology Department, Victoria University of Wellington, Wellington.

D. I. Williamson, Marine Biological Station, Port Erin, Isle of Man, British Isles.