Rev. Acad. Canar. Cienc, XI (Nums. 3-4), 113-119 (1999) THE OCCURRENCE IN WATERS AROUND THE CANARYAND CAPEVERDE ISLANDS OFAMPHIONIDESREYNAUDII, THE SOLE SPECIES OF THE ORDER AMPHIONIDACEA (CRUSTACEA: EUCARIDA). J. A. Lindley* and F. Hernandez** *Centre forCoastal and Marine Sciences, Plymouth Marine Laboratory, The Hoe, Plymouth, PL1 3DH, ReinoUnido. **Departamento de BiologiaMarina, Museo de Ciencias Naturales. OAM. Cabildo de Tenerife, Aptdo. Correos 853, 38003 SantaCruz de Tenerife, Canarias. ABSTRACT The Eucaridean Order Amphionidacea includes only one known species,Amphionides reynaudii. One of the characteristics distinguishing the Order is strong sexual dimorphism. This species is found in all oceans between 36°N and 36°S, the zoeas living near the surface but the adults at great depth. A specimen ofa zoea was taken during the TFMCBM/981 Cabo Verde Cruise offSan Nicholas island (NW ofthe Cape Verde Archipelago). The zoea was of a late developmental stage originally described as the penultimate zoea but subsequent work indicated that it was the last zoeal stage of the female. The present specimen had setose pleopods developing within the non-setose cuticle, confirming thatitis the last zoea. RESUMEN El Orden Eucarideo Amphionidacea, una de cuyas caracteristicas mas distintivas es su acusado dimorfismo sexual, incluye solo una especie conocida, Amphionides reynaudii. Esta N se distribuye por todos los oceanos entre 36 y 36 S, las zoeas cerca de la superficie, mientras que los adultos prefieren vivir a gran profundidad. En el curso de la campana TFMCBM/98 Cabo Verde (incluida en el Proyecto Macaronesia 2000 del Museo de Ciencias Naturales), un especimen de zoea de este interesante orden fue recolectado en una pesca planctonica cerca de la isla de San Nicolas (NO del Archipielago). La zoea fue originalmente descrita como en penultima fase de desarrollo, aunque trabajos mas exhaustivos pusieron de manifiesto que se trataba de la fase final de una hembra (9), puesto que el especimen presentaba pleopodos setosos desarrollandose dentro de una cuticula no setosa, caracteristica que confirmaeste estadio. 1 ThiscruisehasbeensupportedbytheMacaronesia2000ProgramoftheNatural SciencesMuseumofTenerife (O.A.M.C.) 113 INTRODUCTION 1.- Amphionides renaudii was first described asAmphion reynaudii on the basis oflarvae from the Indian Ocean (MILNE EDWARDS [5]). Subsequently larvae were identified as 4 species before the adult was described and named asAmphionides valdiviae ZIMMER [9]. A full account of larval development (HEEGAARD [3]) demonstrated that all the previously described forms could be referred to a single species with a distribution in all oceans between 36°N and 36°S. WILLIAMSON [7] has given an account ofthe varying opinions as to the taxonomic position ofAmphionides. Initially itwas thoughtthat they were close to the Phyllosomalarvae ofPalinuridea, then that they were larvae ofPolycheles (Eryoneicus larvae are now known to be the larvae ofthis genus), orrelated to Sergestids or the Caridean larval genus Eretmocaris. Following the description of the adult, Amphionides was considered to be a Caridean, albeit forming a distinctive family or sub-tribe. WILLIAMSON raised it to the status of an Order, the Amphionidacea, on the basis ofsexual dimorphism, the distinctive form ofthoracic brood pouch in the female, the thoracic limbs, the abdominal pleura, the branchiae and the nature of the larvae. The Amphionidacea thus become one ofthree Orders, with the Euphausiacea and Decapoda, in the SuperorderEucarida, The larval stages mainly occur in the epipelagic zone. HEEGAARD [3] concluded that they were most abundant in the upper 30m, WILLIAMSON [7] found that most occurred above 100m. No evidence has been presented for differences in vertical distributions between these stages. The adults however usually occur much deeper. ZIMMER [9] found them at about 4000m depth. HEEGAARD [3] gave a range of 2000-5000m where he would expect new record of adults, although the he recorded one adult female at about 60m depth. WILLIAMSON found specimens in closing nets sampling between 700 and 1700m and open nets sampling from 3700m depth to the surface. GURNEY [1] recorded 3 specimens from between 2700m andthe surface. 1.1. Records from the easternAtlanticnearthe Canary and Cape VerdeIslands A specimen was taken in a diurnal haul (24C98D reference) with a triple no-closing netWP-2 (200 u standardforthe mesozooplankton with adiameteropen mouth 56 cm/bynet, 114 6658 m3 water filtered in 1000 meters ofhaul selon the information of a flowmeter installed) between 1000 m depth to surface (bottom 1200 meters) at the station 16° 38' 90" N and 24° W 49' 36" (off San Nicolau Island) at 15,55 p.m. on September 24, 1998 during a TFMCBM/98 Cabo Verde-Cruise, supportedby the Natural Sciences MuseumofTenerife on the "Corvette" ship as part of a MACARONESIA 2000 PROGRAM. The specimen captured was identified as alate zoea stage ofthe type describedby HEEGAARD [3] as azoeaXII. There are previous records of the species near the Canary Islands and Cape Verde Islands from ZIMMER [9], GURNEY [1], HEEGAARD [3] and WILLIAMSON [7]. ZIMMER recorded adults near Madeira and off Cape Palmas. GURNEY'S records were of larvae from the Canary Islands (29°27'N, 15°07'W) and Cape Verde Islands (14°39'N 25°51'W). HEEGAARD recorded both adults and larvae near the Canary Islands. WILLIAMSON examined specimens from samples taken south-west of Cape Verde within the area 10°14'-11°35'N, 19°51'-21°26'W and one sample from south-west of the Canary Islands (25°00'N, 19°36'W). He also reported that metamorphosed specimens were taken in the region of Cape Verde, Senegal by FOXTON (unpublished) (in Addendum to WILLIAMSON [7]). 1.2. Morphology The early zoea stages closely resemble caridean larvae (HEEGAARD [3]). According to WILLIAMSON [8] thoracopods 1 and 2 (the first and second maxillipeds) are well separated inAmphionides but are close together in the Caridea. At about the sixth zoea stage the carapace starts to become dorso-ventrally flattened, a characteristic that contributed to the suggestion of a relationship to phyllosoma larvae (WILLIAMSON [7]). No chelae or pseudochelae develop in the later stages in contrast with the late zoea stages ofCaridea. The work of GURNEY [1 & 2] and LEBOUR [4] indicated that there were 9 zoea stages but HEEGAARD described 13 "mysis" (zoea) stages. WILLIAMSON [7] concluded that the number ofstages may be variable and that HEEGAARD's stages XII and XIII are not successive stages but the last zoeal stages of the female and male respectively. There is one immature post-larval stage (megalopa) in the female. The zoeas range in size from 4.0mm to 25.0mm (male last zoea). HEEGAARD [3] concluded that the first zoea was the first free 115 living stage. However GURNEY [2] noted the occurrence ofa stage with no rostrum without further description or illustration and HEEGAARD speculated on the possibility of the existence ofa short-lived "promysis" (prezoea) stage. The carapace of the adult female is extremely thin and nearly always badly damaged in net caught specimens. The descriptions by GURNEY [1], HEEGAARD [3] and WILLIAMSON [7] have depended on examination of several specimens with differing patterns ofdamage. The carapace is inflated to form what WILLIAMSON [7] interpreted as a brood chamber. The absence of eggs from any of the >100 specimens examined by various authors is evidence that the eggs are not attached to the pleopods, as they are in most decapods, but are retained loose in the thoracic brood chamber and have been lost when the delicate carapace was damaged. The mouthparts and digestive system are vestigial and none of the thoracic limbs are functional maxillipeds so it is unlikely that the adult female feeds. The abdomen andpleopods are robust in contrast with the thorax. The firstpleopods are much enlarged, uniramous, U-shaped at the distal end and reaches far forward into the carapace. They may form a partial closure of the brood chamber in life (WILLIAMSON [7]). As yet there is no record of an undamaged female and no specimen has been taken with eggs retained in the brood chamber. Availability of such specimens would provide the opportunity to confirm aspects ofthe biology ofthe species thatremain uncertain. WILLIAMSON [7] concluded that the stage described by ZIMMER [9] and GURNEY [2] as the female and by HEEGAARD [3] as the first post-larval stage, is in fact the male. Ifit were not sexually mature it would be considered to be a megalopa according to Williamson's (1969) system. The carapace is more inflated than in the zoeal stages but less so than in the female, The mouthparts and alimentary system appear fully functional, but there aarree nnoo sseettaaee oonn tthhee eeppooxxiitteess oofftthhee 22 ttoo 77 tthhoorraaccooppooddss.. TThhe pleopods are setose andthe 1 resembles the others exceptforthe small size ofthe endopod. The present specimen is illustrated in Figure 1. The total length of the specimen is 24.1mm, the carapace length is 13.3mm and its width is 4.3mm, the abdomen was 7.1mm long and the telson length is 3.7mm. The equivalent measurements for this stage given by HEEGAARD [3] were 23mm, 13mm, 4mm, 8mm and 2.5mm respectively. HEEGAARD gave a full description ofthe appendages ofthis stage. There are setose pleopods developing 116 within the non-setose cuticle, confirming WILLIAMSON'S [7] opinion that this is indeed the lastzoea stage. Examples of earlier zoea stages described by HEEGAARD [3] and the adult female, adapting the figure from WILLIAMSON [7] with amendments consistent with HEEGAARD'S figure ofthat stage are givenin Figure 2. REFERENCES 2. [1] GURNEY, R., 1936. Larvae of decapod Crustacea, 2. Amphionidae. Discovery Rep. 12, 392-399. [2] GURNEY, R., 1942. The larvae ofthedecapod Crustacea. Ray Society. 308pp. [3] HEEGAARD, P., 1969. Larvae ofdecapod Crustacea. 2. Amphionidae. Dana Rep., 11, 1- 82. [4] LEBOUR, M.V., 1950. Notes on some larval decapods (Crustacea) from Bermuda.-II Proc. Zool. Soc. Lond. 120, 743-747. [5] MILNE EDWARDS, H., 1832. Note sur un noveau genre de Crustaces de l'ordre des Stomatopodes.Annls. Soc. Ent. France. 1, 336-340. [6] WILLIAMSON, D.I., 1969. Names of larvae in the Decapoda and Euphausiacea. Crustaceana, 16, 210-213. [7] WILLIAMSON, D.I., 1973.Amphionides reynaudii (H. Milne Edwards), representative of aproposed new orderofEucaridan Malacostraca. Crustaceana, 25, 35-50. [8] WILLIAMSON, D.I., 1982, Larval morphology and Diversity. In: The Biology of Crustacea, Vol. 2, Embryology, Morphology and Genetics. D.E. Bliss ed., Academic Press, New York, pp 43-110. [9] ZIMMER, C, 1904.Amphionides valdiviae n.g. n. sp. Zool. Anz. 28, 225-228. ACKNOWLEDGEMENTS 3. Special mention to our colleagues in the TFMCBM/98 Cape Vert Cruise, Dr. Sebastian Jimenez and Mr. Pedro Ortega for their collaboration during the sampling 117 Figure 1. Amphionides reynaudii zoea from sample 24C98 D (1000-0m) in the TFMCBM/98 Crusie. (a) Lateral view with bases ofthoracopods shown and numbered (1 is a maxilliped, 2 and 3 were described by Heegaard as maxillipeds but are not functional feeding appendages ansd are 4-7 are pereiopods) details of appendages are described by Heegaard (1969). (b) Dorsal view ofcarapace. Scalebar=5mm Figure 2 (next page). Amphionides reynaudii. a) Zoea I after Heegaard (1969), scale bar lmm, b) Zoea II after Heegaard (1969) scale bar 1mm, c) adult female modified from Williamson (1973) andHeegaard (1969). Scale bar 5mm. 118 a 119