Larval Appearance of the Sea Urchin Loxechinus Albus in Chiloé Island, Chile
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Aquaculture Sci. 57（3），371－382（2009） Larval Appearance of the Sea Urchin Loxechinus albus in Chiloé Island, Chile 1 Sohei KINO Abstract: To obtain basic information about propagation for the Chilean sea urchin, Loxechinus albus, distribution of echinopluteus larvae of this species was investigated from 1986 to 1989 in the eastern coastal waters of Chiloé Island, Chile. Echinopluteus larvae of three sea urchins: L. albus, Pseudechinus magellanicus and Arbacia dufresnei were observed in the waters. The larva of L. albus was distinguished from the other two species mainly by the difference in skeletal rod structure. The larvae of this species were observed for almost a year, and the 4-armed larvae appeared mainly from November to January. The metamorphic larvae were observed only once in October 1988 in Hueihue in the investigation period. The number of larval appearance in the southern waters was larger than that in the northern waters. Key words: Loxechinus albus; Sea urchin; Echinopluteus larva; Metamorphic larva Sea farming is currently the main counter- not observed in the investigational waters. measure for the propagation of sea urchins. In Though there are many reports of the spawn- Chile, the sea urchin, Loxechinus albus is one ing season in L. albus (Gutiérrez and Otsu 1975; of the most important fisheries resources, and Bückle et al. 1978; Bay-Schmith et al. 1981; due to the need for propagation, artificial seed Guisado and Castilla 1987; Zamora and Stotz production of this species was studied (Zamora 1992; Oyarzún et al. 1999; Kino and Agatsuma and Stotz 1994; Cárcamo 2004). To succeed 2007), there are few reports for the larval and in propagation of the target species, it is very juvenile periods in natural waters. As for the important to clarify the reproduction system, natural larva of L. albus, the qualitative appear- and to investigate the ecology from spawning ance in the spawning season in Chiloé Island through to juvenile via the larval period. and Guaitecas was reported (Bay-Schmith et al. According to Larraín (1975), four species of 1981), and the annual appearance of 4-armed sea urchin, L. albus, Pseudechinus magellanicus, larvae in Chiloé Island was also reported (Kino Arbacia dufresnei and Tetrapygus niger are dis- and Agatsuma 2007). However, no complete tributed in the investigational waters. Under report of the 4-armed stage through to the artificial rearing conditions, the larval morphol- metamorphic stage was found. McEdward and ogy of L. albus (Arrau 1958; Bückle et al. 1976; Miner (2007) reviewed echinoid larval ecology, Guisado and Castilla 1987) and A. dufresnei but there are many unknowns regarding natu- (Bernasconi 1942) have been reported, while ral L. albus larva, and the recruitment system those of P. magellanicus and T. niger were not of this resource is not clear. In this study, the reported. Therefore, identification of sea urchin period and quantity of larval appearance were larvae appearing in the waters was tried except investigated in eastern coastal waters of Chiloé for the larva of T. niger, of which adults were Island. Received January 27, 2009: Accepted April 27, 2009. 1 INTEM Consulting, Inc., Tokyo 160-0023, Japan. E-mail: [email protected] 372 S. Kino focused on the Gulf of Ancud and the Gulf of Materials and Methods Corcovado, respectively. During Period-III, it was carried out only at the Hueihue-A, Queilen Larval appearance was surveyed at 14 locali- and Quellón sites. ties (26 sites) from June 1986 to March 1989 Planktonic larvae were collected at inter- (Fig. 1). Among these localities, in Hueihue, vals of 3–4 days at least, except for the three seven sites (D-J) at an interval of 1.5 km months during July–September 1988. Larvae to 10.5 km offshore were also studied from were collected two or three times per investi- December 1986 to March 1987. Numbers and gation by vertical hauls of a Kitahara-Plankton durations surveyed are shown in Fig. 2. The net (xx13, 25 cm diameter) from a depth of 20 durations were different among the localities m to the surface at each site. The filtering rate and sites, mainly divided into the three periods: was assumed to be 100%. The larvae collected June 1986–June 1987 (Period-I), July 1987–June were fixed immediately with 5% neutral forma- 1988 (Period-II) and October 1988–March 1989 lin seawater. The number of L. albus larvae by (Period-III). During periods I and II, the surveys each developmental stage was counted using a Hueihue 10.5 km offshore 1 Hueihue Hueihue 2 Linao 1.5 km A A B D C 。 B 110 1 km Linao 3 Quemchi 1 Quemchi 2 3 4 Dalcahue 4 B A 5 6 7 5 Teupa A Guaitecas Channel Moraleda B Republic of CHILE 6 7 Queilen Quellon' Chadmo Yaldad Cailin Tranqui I. Cailin I. Paula Centinela Coldita I. Laitec I. Chaullin I. Chaullin Laitec 3 km 3 km Fig. 1. Localities and sites (●) for Loxechinus albus larvae collection in eastern coastal waters of Chiloé Island, Chile. Larval Appearance of Loxechinus albus 373 Number surveyed Duration surveyed by month Locality Site by period 1986 1987 1988 1989 III III J J A S OND J FMAMJ J A S OND J FMAMJ J A S OND J FM Period-I Period-II Period-III Hueihue A 64 48 25 B 34 C 8 D 46 E-J 59 Linao A 13 B 8 Quemchi 9 Dalcahue A 13 B 9 Teupa A729 B524 Queilen 54 83 50 Quellon' 56 82 44 Chadmo 18 Centinela 16 Chaullin 16 Paula 23 Cailin 19 Laitec 21 Yaldad 9 68 Fig. 2. Number and duration surveillance, of Loxechinus albus larvae at each locality and site in eastern coastal waters of Chiloé Island, Chile. projector (Nikon V12), a biological microscope oral rods of L. albus and P. magellanicus were and/or a dissecting microscope. The number fenestrated, while those of A. dufresnei were of larvae was calculated as the mean number non-fenestrated. The body rods of L. albus and per vertical haul. To differentiate the three A. dufresnei were jointed at the end of body, species of larvae, L. albus, P. magellanicus and while those of P. magellanicus were straight. A. dufresnei in the waters, complete 4-armed Recurrent rods were found in L. albus and A. larvae were obtained in a laboratory by artificial dufresnei. In the 6-armed stage, L. albus and fertilization, and taxonomic identification was P. magellanicus added one pair of postero- performed using the structure of the skeletal dorsal arms with fenestrated rods. However, A. rods of these larvae in the 4-armed stage. As for dufresnei larvae did not have a 6-armed stage, the larvae after the 6-armed stage, they were but did have an 8-armed stage having one pair mainly differentiated by characteristic skeletal of postero-dorsal and postero-lateral arms. In rods (the body rod, the post-oral rod and the the 8-armed stage of L. albus, two anterior cili- ventral transverse rod), formation of ciliated ated bands between the right post-oral arm and bands, and the existence of pedicellaria, besides left one, and other two ciliated bands between the characteristic 4-armed stage. Former stud- the right postero-dorsal arm and left one were ies about the morphology of L. albus larvae found. In P. magellanicus, four anterior ciliated (Arrau 1958; Guisado and Castilla 1987) were bands developed around each base of the two also checked. post-oral arms and two postero-dorsal arms. A. dufresnei larvae developed into the 10-armed Results stage with one pair of pre-oral arms. The cili- ated bands of A. dufresnei did not develop as in Identification of L. albus larvae the other two species. In the metamorphic stage Morphological characteristics of L. albus, P. of L. albus, five primary spines were lined circu- magellanicus and A. dufresnei at each develop- larly without pedicellaria at the end of the body. mental stage (except the 6-armed stage) are In P. magellanicus, the posterior transverse rods shown in Fig. 3. In the 4-armed stage, post- developed like a pectin-skeleton. In A. dufresnei, 374 S. Kino (a)(b)(c) (d)(e) 2 1 4 7 7 6 12 6 A Not observed 3 12 10 9 9 8 13 13 8 14 4 1 2 R 6 7 11 6 7 3 B 12 12 14 8 10 8 11 14 R 13 13 14 15 1 2 6 4 R 6 7 7 C 3 14 9 8 8 10 16 5 9 10-armed 15 Fig. 3. Morphological characteristics of the larvae of Loxechinus albus (A), Pseudechinus magellanicus (B) and Arbacia dufresnei (C) by developmental stage in random scale; (a) 4-armed stage, (b) skeletal rod side view of the 4-armed stage, (c) 8-armed stage, (d) metamorphic stage, and (e) metamorphosing larvae. 1: post-oral arm, 2: antero-lateral arm, 3: postero-dorsal arm, 4: pre-oral arm, 5: postero-lateral arm, 6: post-oral rod, 7: antero-lateral rod, 8: body rod, 9: recurrent rod, 10: ventral transverse rod, 11: posterior transvers rod, 12: anterior ciliated band, 13: posterior ciliated band, 14: spine, 15: pedicellaria, 16: tube foot, R: arm rod the postero-lateral arms elongated to approxi- December, respectively. In Queilen, the number mately 2.5 mm, while the post-oral arms elon- of 6-armed larvae reached a peak of 8.0 individu- gated to approximately 4 mm. Metamorphosing als in December. In Hueihue-A, B and D, Teupa-A larvae of P. magellanicus and A. dufresnei were and B and Yaldad fewer 4, 6 and 8-armed (－＜ 3.7 observed to have posterior transverse rods (P.