Reproductive Behavior of the Honeycomb Leatherjacket
Total Page：16
File Type：pdf, Size：1020Kb
Japan. J. Ichthyol. 魚 類 学 雑 誌 41(1): 80-83, 1994 41(1): 80-83, 1 9 9 4 Materials andmethods Reproductive Behavior of the Honeycomb Leatherjacket, Cantherhines pardalis Underwater observations were carried out at a (Monacanthidae), at Kashiwajima, Japan rocky reef off Kashiwajima, southern Shikoku, Japan (32•‹46'N, 132•‹37'E) from June 18 to August 17, Hiroshi Kawasel and Akinobu Nakazono 1991. Kashiwajima is almost at the northern distri- bution limit of Cantherhines pardalis. Although not Department of Fisheries, Faculty of Agriculture , rare, the species was infrequent at Kashiwajima, as Kyushu University,6-10-1 Hakozaki, at Iriomotejima, Kuroshima, Akajima and Sesoko- Higashi-ku,Fukuoka 812, Jap an jima, Ryukyu Islands, Japan (24-27°N), due to its Present address:Natural Historymuseum 1and Institute , cryptic and wary nature (Kawase, personal observa- Chiba, 955-2 Aoba-cho, Chuo-ku, Chiba 260, Japa n tion; See alsomyers, 1989). For the reason given (ReceivedNovember 24, 1993; in revisedform January 20, above, C. pardalis was followed for as long as pos- 1994; acceptedmarch 29, 1994 ) sible when encountered during a study on another filefish, Stephanolepis cirrhifer, in an area of 40m Monacanthid fishes inhabit both temperate and 30m at 10-13m depth, and also on the way •~to and tropical shallow waters. About 95 species are known from the study area and the shore (total observation world wide (Nelson, 1984), including 26 species in time; 300min). In the earlymorning of July 20, a Japan (Matsuura, 1984). Among them, Stephano- pair of C. pardalis, both about 180mm TL (total lepis cirrhifer, Thamnaconusmodestus and Aluterus length), were observed spawning on algae. The monoceros are commercially important species in individuals could be discriminated by a split in the Japan, their spawning behavior in aquaria, and em- dorsal fin, in addition to the female having a swollen bryonic, larval and juvenile development, and abdomen. Detailed observations of the pair were attempted around the spawning site on 10 occasions growth andmortality at the early stage having al- ready been reported (e.g., Takami and Utsunomiya, until August 14, between 0530 h and 0805 h (90min 1969; Tsukashima et al., 1983; Kitada et al., 1985) . per day), but the fishes were located on only 5 of However, reproductive behavior andmating systems these. in the field are not known in these species, having Eggs spawned on July 20, 1991 were collected the been reported only in twomonacanthids, Oxymona- following day, together with the supporting algae, canthus longirostris and Paramonacanthus japonicus and fixed in 10% formalin. The embryonic develop- mental stages were recorded and algal species identi- (Barlow, 1987; Nakazono and Kawase, 1993). These reports indicated differences in spawning sites, fied under a binocularmicroscope. While following C. pardalis on August 2, 1991, discharged excrement parental egg-care, and number of eggs per clutch between the two species. was collected and fixed in 10% formalin. Two The honeycomb leatherjacket, Cantherhines par- individuals (186mm and 172mm TL) were captured on the rocky reef at 5m depth on July 17, 1993. dalis, which has a dark brown body color with a small but conspicuous white spot on the upper edge Both the excrement and stomach contents of the of the caudal peduncle, attains 16 cm SL (standard collected fish were examined under a binocularmi- length). It is distributed from Sagami Bay, Japan to croscope. The two fish were deposited in Natural the Indo-West Pacific (Matsuura, 1984). At Kashi- Historymuseum and Institute, Chiba. wajima, southern Shikoku, Japan, a pair of C. parda- lis, were observed spawning on algae, both parents Results immediately departing the spawning site without egg care. Such behavior is similar to that of O. longi- Displays.-Male Cantherhines pardalis exhibited rostris, which spawns on toxic algae to avoid egg- three types of display (Fig. 1). Onmeeting a second predation (Barlow, 1987). This paper describes the male, each raised the head, expanded the ventral flap spawning behavior of C. pardalis and the nature of and vibrated the first dorsal spine some 3-4 times per the algae on which the eggs were deposited, and second ("vibrating"; Fig. la). Subsequently, recip- related ecological features, including aggressive and rocal charging and pecking often occurred. "Vibrat- courtship displays, home range, food preference and ing" was also performed toward females, probably as egg characteristics. a courtship display. A second courtship display was ― 8 0 ― Reproductive Behavior of Cantherhines pardalis a b Fig. 1. Three types of display of male Cantherhines pardalis. a) Aggressive display of two males ("vibrat- ing"); b) courtship display of a male following a female ("lying"); c) male (left) nuzzling the face of his partner ("nuzzle"), while the female (right) thrusting her snout into tufts of algae ("thrust") before spawning. "lying" (Fig . 1b); wherein a male followed a female Spawning. On July 20, a male was observed fol- with his body in a horizontal position, at the same lowing a female at 0615 h, she wandering back and time changing his usual dark brown body color to forth over an area of about 30m•~20m. The male white, with a conspicuous honeycomb pattern. The exhibited "nuzzle," coinciding with the female "thrust" on the algae third courtship display observed was "nuzzle" (Fig. at several sites, often returning lc); wherein a male pecked at the face and side of the to the same site. When a second male appeared at body of a female, while she thrust her snout repeat- 0618 h, the two males exhibited "vibrating" and edly into tufts of algae covering the rock surface fought intensely for a minute until the intruding ("thrust"). Male "nuzzle" and female "thrust" were male retreated. Spawning occurred at 0622 h, at one observed before spawning. of the sites of 11 m deep where the female had earlier ―8 1 ― H. Kawase & A. Nakazono exhibited "thrust." The male and the female touched with those of Oxymonacanthus longirostris, studied abdomens, the male then slanting his body, and by Barlow (1987). Firstly, females of both species released gametes. Mating lasted only 2-3 seconds. wandered back and forth thrusting their snout re- Both fish left the site immediately, with no parental peatedly into tufts of algae ("thrust") at several sites care being apparent. The male initially followed the before spawning. Barlow (1987) suggested that female, but they separated at 0625 h. female O. longirostris were testing the suitability of The close following of the female by the male, as the algae for eggs, including such aspects as texture, well as male "nuzzle" and female "thrust," was also depth, chemical nature and the presence of other observed around the spawning site from 0630 h to eggs. When female C. pardalis exhibited "thrust," 0735 h on July 23 and from 0650 h to 0800 h on she was often repelled by territorial damselfishes. August 14. However, on both days the female had Occupation of areas within the algae by such territo- not spawned by the conclusion of the observations, rial fishes may limit available spawning sites for C. at which time "nuzzle" and "thrust" were continu- pardalis, thereby resulting in female wandering. ing. The female was often repelled by the territorial Secondly, both O. longirostris and C.pardalis spawn- damselfishes, Chromis fumera and C. weberi, during ed on toxic algae. O. longirostris spawns on some her "thrust" at several sites. species of toxic blue green-algae, probably to prevent Home range. During incidental observations of egg predation (Barlow, 1987). Eggs of C. pardalis the pair on 6 days (200 min), the home ranges of the were attached to brown algae (Dictyotaceae). Sev- male and female overlapped within an area of about eral species of Dictyotaceae, such as Dictyota dicho- 50m•~40m at 8-15 m depth, although they were not toma and Dictyopteris divaricata, are known to be always swimming together. toxic and thus avoided by sea urchins, ear shells and Eggs.-The eggs of Cantherhines pardalis, collect- herbivorous fishes (Hay et al., 1987; Shiraishi et al., ed 25 hr after spawning, were spherical in shape, 0.53 1991). Prostrate thalli of several species of Dictyota 0.01 mm (IF:L SD, n=10) in diameter and had •}3-5 and Dictyopteris have a tendency to form a mono- oil globules, 0.078-0.117mm in diameter. The em- specific community covering the surface of rocks, bryonic body had a pair of optic vesicles and 20 such algal communities being commonly seen at myomeres at a water temperature of 23.7•Ž. The Kashiwajima. It is likely that C. pardalis spawns eggs were demersal and adhesive, being scattered on selectively on such algal communities in order to the algae. The number of the eggs was only 40, prevent egg predation. Spawning on dictyotaceous probably because of loss during collection. The algae algae may also be advantageous for preventing egg species on which the eggs were deposited were all disturbance by conspecifics, because a smaller members of Dictyotaceae (brown algae), i.e., Dicty- amount of dictyotaceous algae was found in C. par- ota dichotoma, Dictyota sp., Dictyopteris sp., and an dalis excrement and stomach contents. unidentified species. Food preference. -Cantherhines pardalis pecked at Acknowledgments algae covering the rock surface in the daytime. Ex- crement and stomach contents examined comprised We are grateful to the Tominaga family for assist- mainly algae, especially red algae. The following 16 ing our stay in Kashiwajima. S. Kawaguchi, Kyushu algal genera (12 families) were recorded: Galaxaura, University, helped in identification of algae. Thanks Gelidium, Jania, Callophyllis, Plocamium, Hypnea, also go to K. Matsuura, National Science Museum, Gracilaria, Ceramium, Acrosorium, Polysiphonia, Tokyo, for useful suggestions concerning the mor- Symphyocladia and Leveillea (Rhodophycophyta), phological features of Monacanthidae.