Piggybacking Pycnogonids and Parasitic Narcomedusae on Pandea Rubra (Anthomedusae, Pandeidae)
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Plankton Benthos Res 2(2): 83–90, 2007 Plankton & Benthos Research © The Plankton Society of Japan Piggybacking pycnogonids and parasitic narcomedusae on Pandea rubra (Anthomedusae, Pandeidae) FRANCESC PAGÈS1†, JORDI CORBERA2 &DHUGAL LINDSAY3* 1 Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta 37–49, 08003, Barcelona, Catalunya, Spain 2 Carrer Gran 90, 08310 Argentona, Catalunya, Spain 3 Marine Biology and Ecology Research Program, Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natushima-cho, Yokosuka, 237–0061, Japan †Deceased Received 26 October 2006; Accepted 30 January 2007 Abstract: Associations between pycnogonids and the mesopelagic anthomedusan Pandea rubra are reported from two in situ video footage records off the Pacific coast of northern Japan, and from a plankton sample collected in the Weddell Sea (one juvenile of the pycnogonid Pallenopsis (Bathypallenopsis) tritonis). This is the first pelagic record of a pycnogonid in the Southern Ocean and the first record of an association between pycnogonids and a hydroidomedusa at mesopelagic depths. Taxonomic descriptions of both host and associate are given. Two early stages of a parasitic nar- comedusa adhered to the medusan subumbrella are also reported. Possible origins for the pycnogonid-medusa associa- tion are postulated. Key words: Antarctica, anthomedusa, association, Japan, mesopelagic, pycnogonid Hedgpeth (1962) suggested that bathypelagic pycnogo- Introduction nids are parasites or commensals upon larger organisms, Pycnogonids are marine arthropods that are usually ben- possibly medusae, as previous observations had shown that thic in habitat. However, occasionally they are observed the larval stages of pycnogonids can be parasitic on hy- swimming in coastal surface waters (Clark & Carpenter droidomedusae in coastal waters (Lebour 1916, Oshima 1977) or are found in plankton samples collected in upper 1933, Okuda 1940). Later, Child and Harbison (1986) waters (Lebour 1916, Ohshima 1933, Franc 1951). Records demonstrated, from in situ observations and material col- of pycnogonids in deep-water plankton samples are lected at mesopelagic depths by a manned submersible, that unusual. Hedgpeth (1962) summarized only six records P. calcanea parasitizes the scyphomedusan Periphylla peri- of bathypelagic pycnogonids, almost all concerning the phylla (Péron and Lesueur). They considered it probable occurrence of Pallenopsis (Bathypallenopsis) calcanea that other Pallenopsis species would be found living in the Stephensen in Atlantic and Pacific waters. Stock (1964) de- water column and that the long, pointed distal extremities scribed P. juttingae from a plankton sample collected in the of the legs in this subgenus suggested parasitism on plank- Bay of Biscay. Mauchline (1984) found P. calcanea, P. sco- tonic cnidarians. The two observations of pycnogonids rest- paria Fage and P. tritonis Hoek in bathypelagic samples ing on the exumbrella of the anthomedusan Pandea rubra at from the northeastern Atlantic Ocean. Recently, the occur- mesopelagic depths in Japanese waters and their simultane- rence of P. tritonis, P. calcanea, P. juttingae, P. mollisima ous videotaping by a remotely-operated vehicle (ROV) (Hoek), P. scoparia and perhaps P. tydemani Loman has allow us to infer with confidence that the juvenile specimen been reported from mesopelagic depths in the North At- of P. tritonis collected in the same plankton sample as P. lantic (Bamber 2002a, 2000b). Our discovery of a young rubra in the Weddell Sea, was originally associated with male of P. tritonis in a plankton sample collected at this medusan substratum. Pandea rubra is known to occur mesopelagic depths in the Weddell Sea is therefore notable throughout the world’s oceans, with the exception of the as it is the first pelagic record of a pycnogonid from the Arctic, usually in deep waters. Southern Ocean. To report this co-occurrence, we describe the immature specimen of Pallenopsis tritonis and the Pandea rubra * Corresponding author: Dhugal J. Lindsay; E-mail, [email protected] specimen, and propose possible origins of this pycnogonid- 84 F. P AGÈS, J. CORBERA & D. LINDSAY anthomedusan association. Likewise, two vesicle-shape Japanese specimens structures adhered to the medusan subumbrella and identi- fied as parasitic narcomedusan larvae are described. In situ high definition video footage of two pycnogonids perched on the exumbrella of a specimen of P. rubra (Fig. 1A) was taken south of Hokkaido Island, Japan Materials and Methods (41°00.37ЈN, 144°41.27ЈE), below Oyashio Current-de- Antarctic specimens rived waters at 14:22 by the ROV HyperDolphin (JAM- STEC) at 792 m depth on Dive 98 (22 April 2002). Sam- One immature specimen of the pycnogonid Pallenopsis pling was attempted but was unsuccessful. Physico-chemi- tritonis and one specimen of the anthomedusan Pandea 2 cal parameters of the environment were as follows: temper- rubra were collected by a Multinet (0.25 m open mouth, Ϫ ature 2.96°C, salinity 34.25, dissolved oxygen 3.67 ml L 1, 100 mm mesh size) in the Weddell Sea on 15 January 1993 Ϫ sigma-t 27.29 kg m 3. A second individual of this anthome- during the Polarstern cruise Antarktis X/7. The haul depth dusan species (Fig. 1B) was observed and sampled at 15:18 range was 1,000–500 m and bottom depth was 1,434 m. The at 868 m depth (temperature 2.86°C, salinity 34.29, dis- geographic position was 68°38.7ЈS 55°27.67ЈW, o ff the Ϫ Ϫ solved oxygen 3.54 ml L 1, sigma-t 27.33 kg m 3) during Larsen Ice Shelf. Water temperature ranged from Ϫ0.4 to the same dive and the in situ identification of the medusan 0.4°C, and salinity from 34.60 to 34.64 (Boehme et al. was confirmed on board the vessel. 1995). Both specimens were preserved in 4% formalin. A second observation of two pycnogonids piggybacking on P. rubra (Fig. 1C, D) was made off the east coast of Fig. 1. In situ images of the mesopelagic anthomedusa Pandea rubra Bigelow, 1913; A, aboral view taken at 792 m depth dur- ing ROV HyperDolphin Dive 98 with one adult and one juvenile (?) pycnogonid attached; B, at 868 m depth within a gate sampler (Lindsay 2003) during ROV HyperDolphin Dive 98; C, at 913 m depth during ROV HyperDolphin Dive 105 with one adult and one juvenile (?) pycnogonid attached; D, another frame grab of the same individuals as in C. Pycnogonids and narcomedusae on Pandea rubra 85 northern Honshuu (39°51.97ЈN, 144°21.77ЈE), below a sigma-t 27.32 kg mϪ3. warm core eddy of the Kuroshio Current, between 16:11 and 16:19 by the ROV HyperDolphin (JAMSTEC) at 913 m Results depth on Dive 105 (01 May 2002). An egg-bearing male and a smaller pycnogonid of just under half the size of the Systematic account male were observed attached to the aboral end of the exum- Phylum Arthropoda von Siebold, 1845 brella at the level to which the subumbrella extends. Sam- Class Pycnogonida Latreille, 1810 pling was attempted but was unsuccessful. Physico-chemi- Family Pallenopsidae Fry, 1978 cal parameters of the environment were as follows: temper- Genus Pallenopsis Wilson, 1881 ature 3.34°C, salinity 34.34, dissolved oxygen 0.81 ml LϪ1, Subgenus Bathypallenopsis Stock, 1975 Fig. 2. Pallenopsis (Bathypallenopsis) tritonis; A, trunk in dorsal view; B, trunk in lateral view; C, third leg with tibial spines shown at higher magnification; D, chela; E, distal leg segments. 86 F. P AGÈS, J. CORBERA & D. LINDSAY Pallenopsis (Bathypallenopsis) tritonis Hoek, 1883 0.95–1.23 and 3 compared with 3.31–6.55, respectively). However, the tibial spines are denticulated distally as ob- Description of the Antarctic specimen served in specimens of P. tritonis from the northern hemi- sphere and the above mentioned differences may be due to Immature. Trunk segmented, smooth (Fig. 2A). Lateral the early stage of development. It is also similar to P. cal- processes slightly longer than their diameters, without tu- canea, but this last species does not have auxiliary claws. bercles or spines, and separated by more than half their di- ameters (Fig. 2B). Neck rounded. Ocular tubercle at the an- Phylum Cnidaria Verrill, 1865 terior extreme of segment, bearing four eyes and two latero- Class Hydroidomedusae Claus, 1877 distal papillae. Proboscis two thirds of trunk length, wider Sub-class Anthomedusae Haeckel, 1879 proximally and slightly oriented downwards (Fig. 2B). Ab- Order Filifera Kühn, 1913 domen almost horizontal, with few, small setae extending Family Pandeidae Haeckel, 1879 beyond distal rim of first coxa of fourth leg. Pandea rubra Bigelow, 1913 Chelifores long, scape consisting of 2 well-articulated segments, second segment slightly longer than the first, Description of the Antarctic specimen with some small distal setae (Fig. 2B). Chela palm with few setae near the movable finger (Fig. 2D). Fingers well Umbrella dome-shaped, 15 mm in height, 14 mm wide curved, longer than the palm, tips overlapping. Lateral palp (Fig. 3A). Mesogloea thin but consistent. Exumbrella trans- buds short. Oviger not fully developed, 9-segmented, with- parent, smooth, without cnidocyst tracks. Stomach brown- out setae. ish in preserved specimen, cruciform, with wide base, Second coxa of the third leg longer than both first and hanging down to one fourth of the subumbrellar cavity. third coxa together (Fig. 2C). Femur with some small Mouth with four lips very crenulated. Mesenteries short. spines that increase in length and number towards the sec- Radial canals four, wide, jagged. Gonads not discernible. ond tibia, the latter being the longest segment. Tibial spines Fourteen tentacles, all equal, with wide triangular basal with distal denticulation. Tarsus very short with a long ven- bulbs and abaxial spurs. Velum medium. tral spine and a few short setae (Fig. 2E). Propodus straight, with two strong proximal spines on the heel and five small Remarks spines on the sole.