Pycnogonid J. associated Mar. Biol. with Ass.hydroids India, 50 (1) : 17 - 22, January - June 2008 17 The pycnogonid (Endeis mollis Carpenter, 1904) associated with hydroids from the inshore waters of Visakhapatnam, India S. Veena, P. Kaladharan*, Prathibha Rohit and G. Syda Rao Visakhapatnam Regional Centre of CMFRI, Pandurangapuram, Visakhapatnam - 530 003, Andhra Pradesh, India. E-mail : *kaladharanep@gmail.com Abstract The sea spider or pycnogonid, identified as Endeis mollis Carpenter, 1904 were isolated from hydroids colonized for over 45 days on a large floating cage installed at Visakhapatnam inshore area at a depth of 10-12 m. More than 50% of the population consisted of males carrying egg mass. Occurrence of E. mollis off Visakhapatnam as well as their association with hydroids in Indian waters is reported for the first time. Keywords: Pycnogonids, sea spiders, Endeis mollis, hydroids, floating cage, off Visakhapatnam Introduction Pycnogonids are a strange group of marine arthropods belonging to the phylum Arthropoda and class Pycnogonida (Gr. pyknos = crowded; gony = knee), which means ‘knobby knees’. These sea spiders resemble the terrestrial spiders but have a skinny body. They are rarely observed as they are small and cryptic, or hidden amongst other organisms, moving slowly over seaweeds, corals, sponges or hydroids. Pycnogonids are usually white or else cryptically coloured in relationship to the colonies of the animals they feed on (Bamber, 1992); Earth-Life, 2007). Most pycnogonids are small, but a few deep-sea forms reach up to 70 cm diameter across the legs. Larvae of pycnogonid species are reported as internal parasites of cnidarians but adults are solitary and free living but often live in close association with invertebrate food hosts or seaweeds, bryozoans, hydroids, and in sediment that is on the surface of stones (Ronald, 2003). Vizhinjam coast is known to harbor a rich diversity of pycnogonid species with three species of Pallenopsis, two species of Anoplodactylus and Parapallene kempi (Kurien, 1948). Occurrence of Nymphopsis acinacispinatus and Anoplodactylus sexatilis is also reported from the Arabian Sea (Kurien, 1953) and Anoplodactylus sandromagni from Trivandrum (Krapp, 1996). Four species of pycnogonids Endeis ghaziei, E. meridionalis, E. flaccidus, E. mollis and Anoplodactylus investigatoris were reported from Madras waters by Rajagopal (1963) and Daniel and Sen (1975). Among the phytal fauna associated with the littoral algae off Visakhapatnam, pycnogonids Anoplodactylus sp., Amothea sp. and Pycnogonum indicum were recorded during 1967-1968 (Sarma, 1972). Propallene kempi Calman is a widely distributed form in tropical and temperate waters and is also reported from the east coast of India (Daniel and Sen, 1975). In this paper, we report the occurrence of a pycnogonid Endeis mollis Carpenter, 1904 in association with hydroids seen infested on a HDPP net mesh of large floating cage installed in Visakhapatnam inshore waters. Material and methods The specimens of pycnogonids were collected from a large floating net cage stocked with the fry of the Asian seabass (Lates calcarifer) off Visakhapatnam (17°422’ N lat. and 83°192’ E long.) at a depth of 10-12 m. The sample size of E. mollis collected from the floating cage was 5-7 adults on an average from each hydroid colony. Around 360-400 adult spiders were counted from a 100 Journal of the Marine Biological Association of India (2008) S. Veena et al 18 Description of the specimen All the pycnogonids belonged to a single species and were identified as Endeis mollis Carpenter. The taxonomic position of the sea spider is as follows: Kingdom Phylum Subphylum Class Order Family Genus Species Fig. 1. Hydroids infested on HDPP ropes of net cage cm2 area of the net stage. The cage was moored in the sea for more than 45 days. The HDPP ropes of the net cage were fully infested with hydroids (Fig. 1) and a few bryozoans, polychaetes, juvenile crabs, barnacles and goose barnacles. The foulants attached to the net from three sides of area 100 cm2 were handpicked and preserved in containers with 70% (v/v) ethanol. Examination of hydroids under the stereomicroscope revealed the adherence of pycnogonids on hydroids (Fig. 2). For photographic documentation, an Olympus Canon Ixus 400 camera fitted on Olympus stereomicroscope was used. The identification of the specimens was made using the taxonomic key prepared by Stock (1968). Fig. 2. Pycnogonid-hydrozoan association - Animalia Arthropoda Chelicerata Pycnogonida Pantopoda Endeidae Endeis mollis (Carpenter, 1904) The body was long, narrow and the colour was pale green to brownish. The proboscis was as long as the body. The specimens had 4 pairs of legs, leg span being nearly about three times the length of body (Figs. 3 and 4), two pairs of eyes and moderately long proboscis about half the length of body. The abdomen was a small extension at the posterior side. Legs were slender without strong spines and with isolated spinules or setae. The longer segment being at least 4 times as long as wide, tibia-2 was at most 1¼th times as long as tibia-1. Propodus was curved and not apically produced. Auxiliary claws were at least 1/3rd of the main claw (Fig. 5). Femur was straight and without a distal spur. Femoral cement gland pores were present in one row. Collar was well developed. The body was translucent. The ovigerous legs, present only in the males of this group, arose at the ventral side and wrapped around the egg mass. The size of Fig. 3. Endeis mollis Journal of the Marine Biological Association of India (2008) Pycnogonid associated with hydroids 19 species was ruled out due to morphological dissimilarities. A list of pycnogonid species reported so far from Indian waters is presented in Table 1. Discussion Fig. 4. Endeis mollis showing proboscis and ovigerous legs Fig. 5. One of the legs magnified to show the main and auxiliary claws the specimens from proboscis to anus ranged from 10-192µ. Chelifores and palps were absent which are characteristic to the families Pycnogonidae and Endeidae. However, in the Endeidae family members, the chelifores are present in the juvenile stages but absent in the adults. The samples consisted of brooder males carrying egg mass (>50%), females (40%) and the rest were juveniles. Though pycnogonid-hydrozoan associations have been previously described from other countries, this is the first report from the Indian waters. The species Endeis mollis is also being reported for the first time from Visakhapatnam waters. During identification of the present specimens, the possibility of the previous recorded Pycnogonids, also known as whip scorpions are most commonly placed as a sister taxon to the remaining extant arthropods. There are more than 1,300 species of pycnogonids described, including one fossil species from the Jurassic Period and it is believed that there are many more species to be discovered mainly from remote deep sea habitats (Encyclopædia Britannica, 2007). The known species are traditionally distributed in 80 genera in eight or nine families - Ammotheidae, Austrodecidae, Callipallenidae, Colossendeidae, Nymphonidae, Phoxichilidiidae, Pycnogonidae, Rhynchothoracidae and Endeididae, a monogeneric family sometimes included in Phoxichilidiidae. However, phylogenetic studies are challenging the monophyly of these families (Arango and Wheeler, 2007). The most prominent external feature of pycnogonids is the proboscis. It is a moveable organ and shows wide variation in size and shape among families. The shape and internal structure has been related to specialized feeding habits, sometimes specific to a particular host among parasitic species (Fry, 1965; Staples and Watson, 1987). Adult pycnogonids either suck the juices through the long proboscis from soft-bodied invertebrates or browse on hydroids and bryozoans. A few pycnogonids feed on algae but most are carnivorous, using the cuticular teeth present at the tip of proboscis to pierce the host’s skin before sucking out body fluids (Myers, 2001). The sex organs are found in the long joints of legs. Males and females can be easily differentiated by the absence of ovigers in females of the families Phoxichilidiidae and most Pycnogonidae species. The presence of cement glands on the femora indicates a male (Arango, 2001). Hermaphrodites of Aschorhynchus corderoi are also reported to occur (Miyazaki and Makioka, 1993). Journal of the Marine Biological Association of India (2008) The observed species is able to tolerate the S. Veena et al 20 Table 1. List of pycnogonid species reported from the Indian coast Species Achelia boschi Ammothella omanensis Amothea sp. Anoplodactylus sp. Anoplodactylus cribellatus Anoplodactylus sexatilis Anoplodactylus petiolatus Anoplodactylus eroticus Anoplodactylus investigatoris Anoplodactylus sandromagni Callipallene pectinata /Pallene pectinata Callipallene(?) echinata Colossendeis colossea Colossea macerrima Endeis flaccidus Endeis meridionalis Endeis mollis Endeis ghaziei Eurycyde flagella Nymphopsis acinacispinatus Nymphon andamanense Distribution Arabian Sea Arabian Sea Visakhapatnam Visakhapatnam Vizhinjam, Andaman Sea, Arabian Sea Arabian Sea Vizhinjam Gulf of Mannar Madras Trivandrum Arabian Sea Reference Stock, 1992 Stock, 1992 Sarma, 1972 Sarma, 1972 Kurien, 1948, 1953 Daniel & Sen, 1975 Kurien, 1953 Kurien, 1948 Stock, 1968 Daniel & Sen, 1975 Krapp, 1996 Calman, 1938 Arabian Sea Andaman Sea Arabian Sea, Andaman Sea, Laccadive Sea Madras Madras Madras, Gulf of Mannar, Nicobar, Visakhapatnam Madras Andaman Sea Arabian Sea Arabian Sea, Andaman Sea Calman, 1938 Daniel & Sen, 1975 Nymphon foxi Nymphon arabicum Nymphon longicaudatum Pallenopsis (Bathypallenopsis) annandalei Pallenopsis (Bathypallenopsis) safari Pallenopsis alcocki Arabian Sea Arabian Sea Gulf of Mannar Laccadive Sea Pallenopsis crosslandi Pallenopsis ovalis Parapallene kempi Vizhinjam Andaman Sea Bay of Bengal, Waltair, Orissa, Gulf of Mannar, Vizhinjam, Arabian Sea All along the east coast of India Gulf of Mannar Arabian Sea Arabian Sea Arabian Sea, Andaman Sea Arabian Sea Propallene kempi Pycnogonum indicum Pycnogonum moolenbeeki Pycnogonum tesselatum Rhopalorhynchus kroeyeri Seguapallene echinata Gulf of Mannar Vizhinjam, Andaman Sea Journal of the Marine Biological Association of India (2008) Daniel & Sen, 1975 Daniel & Sen, 1975 Daniel & Sen, 1975 Daniel & Sen, 1975; Calman, 1938; Present Authors Rajagopal, 1963 Nakamura & Chullasorn, 2000 Kurien, 1953 Calman, 1938; Daniel & Sen, 1975 Calman, 1938 Calman, 1938 Daniel & Sen, 1975 Daniel & Sen, 1975 Stock, 1984 Kurien, 1948; Daniel & Sen, 1975 Kurien, 1948 Daniel & Sen, 1975 Kurien, 1948; Kurien, 1953 Daniel & Sen, 1975 Daniel & Sen, 1975 Stock, 1992 Stock, 1968 Calman, 1938 Calman, 1938 Pycnogonid associated with hydroids extreme wave currents in this area. It is not clear at the moment as to the depth of habitat of these species in these waters, since we found them attached to hydroids on the floating cage (10-12m). Of the six species of pycnogonids observed within a depth of 30m at Vizhinjam, Parapallene kempi Calman was the only common species and the other 5 (Pallenopsis sp., Pallenopsis alcocki Calman, Pallenopsis crosslandi Carpenter, Anoplodactylus cribellatus Calman, Anoplodactylus petiolatus, Krøyer) were either rare or casual visitors to the locality (Kurien, 1948). Thus far, at Visakhapatnam Bay there have been two records of the presence of pycnogonids (Kurien, 1948; Sarma, 1972). The present report is intended to supplement previous information on these species along the Indian waters. Since the pycnognids colonize extensively on hydroids and other primary settlers, they may be browsed by some reef fishes as well as the fish farmed in the cage. Their metabolic exudates can attract many types of microflora and fauna. In the pycnogonids, 20-hydroxyecdysone, 20hydroxyecdysone-2-acetate and other ecdysteroids have been identified at high levels in cuticular glands (Tomaschko, 1994). Upon mechanical disturbance these animals secrete ecdysteroids from the gland to the environment and, since these compounds have a strong antifeedant effect, the pycnogonids avoid being consumed by crabs. These animals are not necessarily rare in the wild, but are cryptic, small and easily overlooked. The current species and the list shown in this paper give only a glimpse of the pycnogonid species diversity in the Indian waters. Much more work remains to be done and several new species of this uncommon genus are awaiting to be added to the list of pycnogonids from the Indian waters. Acknowledgements The authors thank the Director, CMFRI for his encouragements. 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