Ichthyol Res (2009) 56:227–231 DOI 10.1007/s10228-008-0088-4

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Increased energy investment in testes following territory acquisition in a maternal mouthbrooding

Haruki Ochi Æ Tomohiro Takeyama Æ Yasunobu Yanagisawa

Received: 30 June 2008 / Revised: 5 November 2008 / Accepted: 7 November 2008 / Published online: 20 December 2008 Ó The Ichthyological Society of Japan 2008

Abstract Underwater observations conducted in Lake territory. It is concluded that energy investment in testes is Tanganyika showed that males of a maternal mouthbroo- delayed for somatic growth until territory acquisition. ding cichlid, fasciolatus, defended a mating territory for at least several months, but left at approxi- Keywords Energy allocation Investment in testes mately noon every day. After the experimental removal of Somatic growth Competition for mating territory males from their territories, new owners occupied the Cichlid vacated territories within several days. New owners exhibited higher body-condition factors and fat indices than the original owners. These results suggest that the new Introduction owners had not previously occupied a territory, considering the physical exhaustion of owners owing to the energy Organisms can adjust the timing of sexual maturity. This expenditure on territory maintenance and mating behaviors life history phenomenon may occur because organisms and a limited time for feeding. Original owners had heavier have a limited amount of energy available for growth, testes than new owners, despite similar body sizes. This maintenance, and reproduction, and thus tradeoffs exist disparity in testis weight suggests that energy investment in among these conflicting activities (Stearns 1992). In fishes, testes increases following territory acquisition. Among environmental factors such as light and temperature can be males that newly occupied a territory during the observa- cues for promoting sexual maturity (Bye 1984; Snelson tion period, larger individuals occupied territories sooner, 1989). Fish sexual maturity is also influenced by social suggesting that large body size facilitates competition for interactions (Fishelson 1970; Borowsky 1973, 1978; Fricke and Fricke 1977;Sohn1977). For example, competition for territory between males may produce a situation in which the level of energy investment in testes changes following H. Ochi (&) territory acquisition. In many fish species the maintenance 4-4-7 Higashimon-cho, Imabari, Ehime 794-0033, Japan of mating territories is a key male strategy for gaining e-mail: [email protected] access to females (Loiselle and Barlow 1978; McKaye T. Takeyama 1984; Thresher 1984; Grant 1997; Kuwamura 1997). Many Graduate School of Science, Kyoto University, Sakyo-ku, studies suggest that mating territories are secured through Kyoto 606-8502, Japan male–male competition (McKaye 1983; Hert 1990; Rossiter 1994; Karino 1996), and large fish often have an Y. Yanagisawa Department of Biology and Earth Sciences, Ehime University, advantage over smaller fish in contests for territory (Turner 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan and Huntingford 1986; Turner 1994; Neat et al. 1998; Maan et al. 2001). In species in which there are surplus Present Address: males seeking mating territories, male energy investment T. Takeyama Graduate School of Science and Technology, Niigata University, in gonads may be delayed to favor investment in somatic 8050 Nino-cho, Ikatashi, Niigata 950-2181, Japan growth until the acquisition of territory, assuming a 123 228 H. Ochi et al. tradeoff between energy investment in growth and sexual speed), lateral display (an owner shows the side of the maturity in male fish. We examined whether the acquisi- curved body to a visitor, which may put its snout close to tion of territory triggers increased investment of energy in the anal fin of the owner), leading (an owner leads a testes in a maternal mouthbrooding cichlid, Petrochromis visitor to the spawning site with a shaking tail pointed at fasciolatus. the fish), quivering (an owner quivers the curved body to Petrochromis fasciolatus, endemic to a visitor), and rush (an owner rushes to a visitor without (Poll 1986), does not maintain a feeding territory, unlike physical contact). Petrochromis fasciolatus is sexually other congeneric species. Instead, the fish forms shoals monochromatic; thus, sex could not be determined during composed of both sexes and raids the territories of other the underwater observations, except for those fish that algivorous to feed on epilithic algae (Kohda and were engaged in mating behaviors. However, because Takemon 1996). The male defends a mating territory in territorial males were usually larger than females (H. which a rock surface is used as a spawning site (Kuwamura Ochi, personal observation), unidentified fish that were of 1986). The female visits the territory to spawn and then approximately territorial male size are herein referred to leaves soon after spawning with the eggs in her mouth. In as ‘‘male-sized,’’ and smaller sized fish are referred to as our study site, this species was common, and many males ‘‘female-sized.’’ established mating territories in the shallow rocky area. A Removal experiments were conducted within the study preliminary investigation suggested the presence of surplus plot during morning hours from 9 December 2002 to 8 males seeking mating territories. January 2003. During this period, the removal of owners In Lake Tanganyika, we conducted underwater obser- was conducted one to eight times successively at each of 14 vations of individual males to describe fish behavior and territories. A total of 35 owners (14 original and 21 new social interactions at their territories to estimate the dura- owners) were caught with a gill net. Immediately after the tion and stability of territory maintenance, and then to removal of owners, the behavior of newcomers that entered determine the presence of competition for territory. In ownerless territories was observed for 60 min (n = 26); addition, males were artificially removed from their terri- the observation ended in 30 min when no fish stayed there. tories, and the timing and manner of new-owner During each dive, the presence or absence of new owners reoccupation of the vacated territories were recorded. in vacated territories was noted after the former owner was Testis weight was compared between the original and new removed. Newcomers were regarded as new owners when territory owners to determine if increased energy invest- they were seen staying at territories on 2 consecutive ment in testes occurred following territory acquisition. We observation days. discuss the strategy of limited energy investment in testes Measurement of specimens. All fish caught for the until territory acquisition in relation to large body size as removal experiment were also used for the measurements an advantage in competition for territory. described below. In total, 27 original owners and 24 males that had newly occupied territory (new owners) were caught for comparison of physical condition. For 15 Materials and methods of the 27 original owners, standard length (SL; mm) and weights (wet; g) of total body (B), testes (T), and fat in Underwater observations and removal experiments. the abdominal cavity (F) were measured in the laboratory Underwater observations were conducted using SCUBA within 5 h after the collection. Only SL was measured at Nkumbula Island (8°450S, 31°050E) near Mpulungu, with a ruler, in the field, for the remaining 12 original Zambia, on 62 days from October 2002 to January 2003. owners. Of the 24 new owners, 21 were caught within Territories of Petrochromis fasciolatus were confined to 2 days, and 3 were caught between 8 and 18 days after rocky-bottomed habitats at depths of 6 to 12 m. A territory occupation. Standard length, B, T, and F were 40 m 9 10-m study plot, subdivided with string into measured in the laboratory within 5 h after the collection 2.5 m 9 2.5 m, was placed at depths ranging from 7 to for all fish caught within 2 days, with the exception of 11 m. At the onset of observations, each of 31 territory one, for which only SL was measured. Only SL was owners (original owners) in the study plot was individu- measured, in the field, for those new owners caught after ally distinguished by the patterns of lateral body stripes. 8–18 days. All fish (except a new owner) of which only During each dive, the presence or absence of males in the SLs were measured were released immediately after territories and their mating behaviors were noted. To measurement. The remaining caught fish were killed by record behavior, a 30-min observation was conducted suffocation in a small plastic bag. The body condition twice (2 owners) or three times (19 owners) between factor (K) was calculated as K = 105 (B - T)SL-3, the 6 -3 07:00 and 12:00 h. Five observed behaviors were fat index (IF)asIF = 10 F SL , and the gonadosomatic approach (an owner approaches a visitor with a normal index (GSI) as GSI = 104 TB-1. 123 Energy investment in testes in cichlid 229

Results Table 1 The number of cases in which newcomers occupied vacated territories after 35 removals of an owner Territory maintenance and interactions between owners New owners Occupied a territory Totals and visitors. At the beginning of observations, 31 By the first In later Petrochromis fasciolatus males held mating territories in or observation daya observation daysb near the study plot. The nearest distance between spawning sites was 3.0 m (±1.0 SD, n = 31). After the initial identi- Neighboring territory 11 2 13 fication, 13 males continued to hold their territories until the owners end of the observation period (66–80 days), and 14 males Unidentified males 20 0 20 held theirs until experimental removal (39–79 days). The Totals 31 2 33 remaining four fish disappeared from their territories for New owners were not found during the observation period in two cases unknown reasons after 19, 23, 37, and 53 days, respectively. a First or 2nd day after removal During this observation period, no fish established territories b Third or 11th day after removal at other sites than those where original owners had once occupied territories. Males usually left their territories Table 2 The number of bouts of interactions observed between between 08:00 and 12:00 h, were absent in the afternoon, and newcomers just after removal of an owner from his territory (cases 1– returned to the same territories by the next morning. 3) and on the next day (case 4) Owners were usually swimming or floating within the Observation timea Case 1 Case 2 Case 3 Case 4 territories, 1–2 m above the bottom substrate. These fish 0753–0834 0800–0838 0835–0837 0709–0937 were feeding in their territories only 0.6% of the time (±0.5 SD, n = 21). When a female-sized conspecific fish Interaction came to the territory, the owner performed quivering [16% Unilateral 3100 quivering of encounters (n = 191)], leading (42.5%), approach Mutual quivering 0 3 0 3 (9.1%), lateral display (5.5%), or rush (26.9%) behaviors. Unilateral lateral 10 2 0 1 During the observation period, spawning occurred three display times (06:45, 08:30, and 09:00 h) at the rock surfaces in the Mutual lateral 61427 territories. No sneaking behavior was observed. Unidenti- display fied male-sized fish occasionally intruded into a territory. Rush 8 3 0 0 Owners responded to them with quivering [3.6% of Fight 5 3 0 7 encounters (n = 56)], leading (3.6%), approach (3.6%), a Time when two or three newcomers were present in a territory lateral display (62.5%), or rush (26.8%) behaviors. Visitors soon left the territory. Removal experiments. In most cases (33 of 35 cases), the sides of their curved bodies (mutual lateral display). after the removal of an owner, a neighboring owner This behavior was repeated frequently. Furthermore, (n = 13) or an unidentified male (n = 20) occupied the newcomers would bite each other (fight). vacant territory within several days (Table 1). Of the 13 Somatic and gonadal conditions of original and neighbors, 3 abandoned their original territories, and the unidentified new owners. Unidentified new owners that remaining 10 occupied both new and original territories. Of took territories from predecessors for unknown reasons the 20 unidentified males, 7 performed leading behavior (n = 4) and those that occupied territories after the within several days following the occupation. experimental removals (n = 20) had body lengths (SL) Male-sized fish appeared during 10 of the 26, 30- or 60- similar to those of the original owners (range 124–141 mm, min observations conducted just after the removal of own- mean ± SD 132 ± 4 mm, n = 24; range 126–138 mm, ers. Of these ten cases, two or three newcomers remained in 132 ± 3 mm, n = 27, respectively; t-test, t =-0.521, the vacated territory in three cases (multiple entries), one P = 0.6044). The body weights of two groups were also newcomer (a neighboring owner or an unidentified male) very similar (new owners: range 73–108 g, 85 ± 11 g, occupied the territory in two cases, and in five cases, one n = 20; original owners: range 75–100 g, 85 ± 6g, male temporarily came to the territory, but left quickly. n = 15; t-test, t = 0.114, P = 0.9098). Multiple entries, similar to the three cases of multiple The K of unidentified new owners was significantly newcomers cited above, occurred once on the day fol- higher than that of the original owners (Fig. 1a; t-test, lowing removal. In cases of multiple entries, newcomers t = 2.462, P = 0.0192). Similarly, the IF of unidentified were observed simultaneously quivering their curved new owners was also significantly higher than that of the bodies at each other (mutual quivering) (Table 2). In original owners (Fig. 1b; t-test, t = 3.844, P = 0.0005), addition, fish would swim ahead of one another and display and the 95% confidence intervals did not overlap. 123 230 H. Ochi et al.

Fig. 1 a Body condition factors (K) and b fat indexes (IF) (mean values with 95% confidence intervals) of original owners and unidentified new owners. The sample sizes are provided at the top

Fig. 2 Testis weights of original owners (filled circle) and uniden- Fig. 3 Correlation between the standard length of unidentified new tified new owners (open circle). A regression line for unidentified owners and the order of occupation of a territory. A male that new owners is provided occupied a territory earlier is assigned a lower number in the order of occupation of a territory. Males that occupied territories on the same Testis weight and body size (SL) were positively cor- day are assigned the same order related in unidentified new owners (Fig. 2; n = 20, 2 r = 0.255, F = 6.156, P = 0.0232), but no correlation Values of both K and IF indicated that unidentified new was found in original owners (n = 15, r2 = 0.027, owners exhibited better body conditions than the original F = 0.367, P = 0.5549). The testes of the original owners owners. Physical exhaustion of mating territory owners rel- (0.144 ± 0.024 g, n = 15) were significantly heavier than ative to non-owners has been demonstrated in another those of the new owners [0.087 ± 0.031 g, n = 20; maternal mouthbrooding cichlid (Karino 1996). Current ANCOVA: effect of body size: F = 6.594, df = 1, body condition reflects the daily activities of the fish. While P = 0.0151; effect of male status (original or new owner): in the territories, Petrochromis fasciolatus males spent only a F = 31.872, df = 1, P \ 0.0001]. short time feeding and engaged in various energy-consuming Larger unidentified males tended to occupy territories activities, such as courtship, mating, and territory defense. earlier (Fig. 3; Spearman rank correlation coefficient: Fish usually maintained mating territories for at least several rs =-0.807, P \ 0.0001). Neither K, IF, nor GSI signifi- months. Such long-term territory maintenance likely results cantly correlated with the order of occupation of territories in the deterioration of body conditions of the owners, despite by unidentified new owners (rs = –0.277, P = 0.2371; being free from territorial activities during the afternoon. In rs = –0.381, P = 0.096; rs =-0.221, P = 0.3501, contrast, non-owners do not consume energy for territorial respectively). activities and probably participate in a feeding shoal during the day, because the common behavioral states of male-sized fish observed during the day were territory owners or par- Discussion ticipants in a feeding shoal (H. Ochi, personal observation). Therefore, it is likely that non-owners maintain better Despite similar body sizes, the original owners of territo- physical conditions than owners. The observed higher values ries had heavier testes than the new owners. This result of K and IF for unidentified new owners suggest that most suggests that an increased energy investment in testes were probably non-owners before acquiring a territory. In follows the acquisition of territory, provided that the new addition, differences in testis weight between original own- owners were non-owners before we observed them occu- ers and unidentified new owners indicate that an increased pying territories. investment of energy in testes follows territory acquisition. 123 Energy investment in testes in cichlid 231

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Env Biol Fish 8:81–96 Acknowledgments The fieldwork was conducted under the McKaye KR (1984) Behavioural aspects of cichlid reproductive research agreement between the Fisheries Department of Zambia and strategies: patterns of territoriality and brood defence in Central the Japanese research team ‘‘MANENO.’’ We thank the staff of Lake American substratum spawners and African mouth brooders. In: Tanganyika Research Unit of Fisheries Research Institute, Mpulungu, Potts GW, Wootton RJ (eds) Fish reproduction: strategies and Zambia, for facilities and assistance during the field work. We are tactics. Academic Press, London, pp 245–273 also grateful for technical assistance on drawing of the figures from S. Neat FC, Huntingford FA, Beveridge MMC (1998) Fighting and Miyagawa, T. Murakami, and K. Saito. Useful comments on the assessment in male cichlid fish: the effects of asymmetries in manuscript were provided by two anonymous referees. H. Ochi par- gonadal state and body size. 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