Nesting Behavior of Acapulco damselfish (Stegastes acapulcoensis): pairs defend nests more vigorously than solitary males

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Nesting Behavior of Acapulco damselfish (Stegastes acapulcoensis): pairs defend nests more vigorously than solitary males

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Nesting Behavior of Acapulco damselfish (Stegastes acapulcoensis): pairs defend nests more vigorously than solitary males
Translated Title:
Comportamiento de anidamiento del pez damisela de Acapulco (Stegastes acapulcoensis): las parejas defienden sus nidos más vigorosamente que machos solitarios
Cech, Lauren
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Subjects / Keywords:
Tropical fish ( lcsh )
Pez tropical ( lcsh )
Pomacentridae ( lcsh )
Costa Rica--Guanacaste--Santa Elena Bay
Costa Rica--Guanacaste--Bahía Santa Elena
EAP Fall 2016
EAP Otoño 2016


Unique pair behavior was observed in Stegastes acapulcoensis, the Acapulco damselfish, in the reefs of Santa Elena Bay of Costa Rica. Observations and video were collected on aggression and territoriality demonstrated by both male-female pairs and solitary males guarding eggs. Agonistic chases and chase distance were recorded over four days during snorkeling expeditions. Results compared parental care behavior (pairs versus solitary) with aggressive chases and chase distance. Solitary male Acapulco damselfish chase significantly less times than paired. Additionally, the paired males chase significantly farther than solitary. Males were observed to defend territory and eggs using aggressive chases, while paired females remained within the nest. These data and behavioral differences may suggest that pair behavior is an effective defensive strategy, likely motivated by a common goal of ensuring survival of offspring. Furthermore, pair defense may be influenced by differences in parental investment and contribution to reproductive success. ( ,,, )
Un comportamiento único en pareja de Stegastes acapulcoensis, el pez damisela de Acapulco, se observó en los arrecifes de la Bahía de Santa Elena de Costa Rica. Se tomaron observaciones y videos del comportamiento agresivo y territorialidad demostrados por parejas de machos-hembras y también machos solitarios cuidando masas de huevos. Las persecuciones agonísticas y la distancia de persecución en el mar se registraron durante cuatro días de buceo. Los resultados compararon el comportamiento de cuidado parental (parejas contra machos solitarios) con respecto a persecuciones agresivas y distancia de persecución. Los machos solitarios persiguieron significativamente menos veces que los machos emparejados. Además, los machos emparejados persiguieron significativamente más lejos que los machos solitarios. Se observó que los machos defendían el territorio y los huevos usando persecuciones agresivas, mientras que sus parejas hembras quedaban cerca del nido. Estos datos y las diferencias de comportamiento demuestran que el comportamiento de las parejas es una estrategia defensiva, y es probable que sea motivada por un objetivo común de asegurar la sobrevivencia de la progenie. Finalmente, la defensa proporcionada por las parejas puede estar influenciada por el costo de cuidar sus huevos y la contribución positiva al éxito reproductivo.
Student affiliation: University of California, Davis
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Nesting Behavior of Acapulco damselfish ( Stegastes acapulcoensis ) : pairs defend nes ts more vigorously than solitary males Lauren Adela Cech Department of Molecular and Cellular Biology University of California, Davis EAP Tropical Biology and Conservation Program, Fall 2016 16 December 2016 ABSTRACT Unique pair behavior was observed in Stegastes acapulcoensis the Acapulco damselfish, in the reefs of Santa Elena Bay of Costa Rica. Obse rvations and video were collected on aggression and territoriality demonstrated by both male female pairs and solitary males guarding eggs. Agonistic c hases and chase distance were record ed over four days during snorke ling expeditions. Results c ompared parental care behavior (pairs versus solitary) with aggressive chases and chase distance. Solitary male Acapulco damselfish chase significantly less times than paired Additionally, the paired males chase significantly farther than solitary. Males were observed to defend territory and eggs using aggressive chases while paired females remained with in the nest. These data and behavioral differences may suggest that pair behavior is an effective defensive strategy, likely motivated by a common goal of ensuring survival of offspring Furthermore, pair defense may be influenced by differences in parental investment and c ontribution to reproductive success. C omportamie nto de anidamiento del pez damise l a de Acapulco ( Stegastes acapulcoensis ): la s par eja s d efiende n su s nidos m ‡s vigorosamente que machos solita r i os RESUMEN Un comportamiento œnico en pareja de Stegastes acapu lcoensis el pez damisela de Acapulco, se observ— en los arrecifes de la Bah’a de Santa El ena de Costa Rica. Se tomaron observaciones y video s del comportamiento agresivo y territorialidad demostrados por parejas de machos hembras y tambiŽn machos solitarios cuidando masas de huevos. Las persecuciones agon’sticas y la distancia de persecuci—n en el mar se registraron durante cuatro d’as de buceo Los resultados compararon el comportamiento de cuidado parental (pare ja s contra machos solitarios) con r especto a persecuciones agresivas y distancia de persecuci—n. Los machos solitarios per s iguieron significativamente menos veces que los machos emparejados Adem‡s, los machos emparejados persiguieron significativamente m‡s lejos que los mach os solitarios. Se observ— que los machos defend’an el territorio y los huevos usando persecuci ones agresivas, mientras que sus parejas hembras quedaban cerca del nido. Estos datos y las diferencias de comportamiento demuestran que el comportamien to de la s pare ja s es una estrategia defensiva, y es probable que sea motivada por un objetivo comœn de asegurar la sobrevivencia de la progenie Finalmente, la defensa proporcionada por la s pare ja s puede estar influenciada por el costo de cuida r sus huevos y la contribuci—n positi va al Žxito reproductivo.


Stegastes acapulcoensis Parental Care Cech 2 INTRODUCTION The r isks of reproducing in the ocean are numerous. Congregations of spawning fish could attract predators. F ish es sear ching for a mate may leave territories or young unatte nded. E gg clutches, the eggs laid after reproductive spawni ng, have no means of defending themselves from egg predators once they are released into the water However, fish exhibit strategies that make their clutche s less vulnerable to attack The fish of the family Pomacentridae, also called da mselfish, for example have a range of behaviors regarding clutch protection T he most conspicuous strategy involves parental defense behavior within the damselfish's territory For example, a damselfish may protect their clutch against conspecifics or smal l predators, like wrasses, by chasing them away with antagonistic swimming behavior (Haley, 2002) These chases have been studied as a measure of territoriality between damselfish (Itzkowitz 1986; Horne, 1995), and could further be used to gauge aggressio n of parents towards predators. Two main types of reproductive behavior distinguish parental defense of eggs In the first behavior, a solitary male defends a territory that will serve as the spawning site. The male courts a female, who then leaves after t he clutch has been laid. Only the male remains to care for and defend the eggs. This solitary nesting behavior is typical of the colonial Dascyllus and Chromis (Fishelson, 1998) In the second behavior, both a male and female are involved throughout the re productive cycle. Both sexes defend the territory spawn, and care for eggs in the nest until they hatch. This secon d nesting behavior is most typical of Amphiprion and Premnas symbiotic anemone fish that are territorial throughout life and likely have p ermanent bonding (Robertson 1972 ). Other species (i.e. Chromis dimidiatus ) exhibit pair nesting behavior, but they are the exceptions to their genus ( Avidor, 1974 ) Regardless of parental care type, mentioned from here on as paired or solitary nesting beha vior, literature demonstrates male damselfish execute the majority of territorial defensive behavior of clutc hes during the breeding season (Avidor, 1974) In the genus Stegastes solitary nesting types have been used as model systems for studying damselfi sh male parental care. Stegastes leucostictus S. nigricans, S. partitus in particular, have shown that single males vigorously defended clutches against conspecifics and egg predator s (Knapp, 1991; Itzkowitz, 1986; Horne, 1995) As currently known w ithin Stegastes females likely visit and pair with males only for the t ime needed to spawn (Horne, 1995 ). For example, female S. partitus and S. altus stay a maximum of 30 60 minutes at male nests to complete spawing, leavi ng immediately after completion (Itzkowitz, 1995; Knapp, 1991 ; Kohda, 1988 ). There are no empirical studies regarding female visitation times or pair prevalence, specifically for Stegastes acapulcoensis. There has been one mention of distinct pairing during the breeding term of S. acapul coensis a species known to have solitary male parental care typical of Stegastes (Breder 1966) I have observed Stegastes acapulcoensis also known as Acapulco damselfish, pairs lasting beyond 3 + hour s in which no spawning occured This appeared to be bo th longer than typical and behaviorally unexpected based on characteristics of this genus. The S. acapulcoensis pairs appeared to exhibit aggressive behavior towards conspecifics and other threats just as solitary Acapulco males do when defending clutches These similar behaviors suggest that S. acapulcoensis may demonstrate parental care in two ways: (1) solitary male or a (2) male female pair Also, differences in pair bonding duration may indicate a defensive strategy (pers. obs.), especially if paired S. acapulcoensis have greater reproductive success ( Perrone, 1979) Many Stegastes damselfish ( i.e. S. dorsopunicans S variabilis & S. leucostictus ) use aggressive swimming behaviors to demonstrate territoriality and protect clutches against


Stegastes acapulcoensis Parental Care Cech 3 conspecific s and egg predators (Barte ls, 19 84; Emery, 1973; Itzkowitz, 1986 1995) Thus quantities of agonistic chases done by pairs and solitary Acapulco damselfish may help indicate differences in aggression between these nesting types In an attempt to explain t he incidence of extended pair bonding, I examine the differences in clutch defense by paired and solitary Stegastes acapulcoensis using chase quantity. I compare the behaviors of solitary and pair parental nest guarders, as well as demonstrations of aggres sion and territoriality. My main questions are: (1) Do Stegastes acapulcoensis pair bond during breeding season? (2) Do pairs of S. acapulcoensis defend clutches more vigorously? MATERIALS AND METHODS My study system, Stegastes acapulcoensis can be found in the waters of the Santa Elena Bay in the Northwestern province of Guanacaste in Costa Rica. Acapulco damselfish typically frequent water columns above regions of rocky outcrops and coral heads in depths of 1.5 to 40 m, feeding on algal gar dens within their territories (Breder 1966 ; see Figure 1 ). Stegastes females are oviparous, and typically make forays from their own territories to male territories in search of a suitable mate and spawning site during breeding season (Karino, 1995) Consp ecific males may also try to approach another male's territory, but are frequently chased away immediately (Haley, 2002). Sexual dichromatism and dimorphism are not obviously apparent in S. acapulcoensis so I determined sex by reproductive and territorial behavior. I call nesting Acapulco damselfish that perform aggressive displays or chases towards conspecifics as males, and fish that are allowed peacefully within the territory as breeding females. I noticed slight differences in coloration between paired males and females (i.e. aggressive chasers had more cream colored posteriors), but variability existed between nests so I did not focus on coloration as a determinant of sex. Figure 1: This photo shows a clutch (white substrate indicated by green arrow) being guarded by a male (far right, cream posterior) and female (center, beige posterior) pair. Red substrate is algae guarded within the male's territory.


Stegastes acapulcoensis Parental Care Cech 4 This study was performed over 4 days from the 20 th to 24 th of November 2016 at two rocky coral reef locations within the Santa Elena Bay Costa Rica One site commonly known as Bajo Rojo is an isolated reef surrounded by open waters, composed of large ro ck substrate intermittently covered in low profile algal gardens. Large horizontal slabs of rock pattern the outcrop and offer crevice sanctuaries for fish trying to hide or seeking rest from the strong current. Depths of the site reach 8 meters during hig h tide. The second location, known as Isla David is a reef with variable rock substrate (i.e. long, flat rock slabs to large boulders) and a depth of approximately 6m at high tide. Differences in substrate offer a variety of current and predator cover for fish. Isla David appears to have more l ow profile algal growth compared to Bajo Rojo with a majority of algae growing between boulders and covering above and below flat rock Damselfish common (25+ fish) to these areas are the Acapulco damselfish, Giant damselfish ( Microspathodon dorsalis ), and Panamic Sergeant Major ( Abudefduf saxatilis ). Breeding males guard nests, as previously mentioned. Females deposit a monolayer of eggs by brushing their cloaca directly to slanted (approx. 45 85 degrees from horizo ntal) substrate within the male's territory (pers. obs. Itzkowitz, 1985 ) I identifi ed potential nest sites by observing Acapulco damsel fish behavior and reef substrate I free dived to confirm the presence of clutches and record the number of Acapulco damselfish within the nest. I examined a small sample of eggs under a dissecting microscope at 40x magnification to confirm their identity. To compare differences in nesting behavior of pairs and solitary Acapulco damselfi sh, I recorded two aspects of chase quantity during ten minute intervals between the hours 0900 and 1300 First, I recorded the number of chases done by an Acapulco male. A chase occurs each ti me a nest dwelling Acapulco leaves the site to rapidly pursue o r deter another fish. Species (type and number) swimming within 2 meters of the nest were noted, as well as whether or not they approached the nest site. I considered approach behaviors to be when a fish nibbled on algal substrate or neared (< 0 .3 meters) the clutch area. Second, I recorded the distance an Acapulco male chased another fish. I measured chase distance using a water submersible diver's tape. During my preliminary observations of S. acapulcoensis nests, I used large rocks to represent distance s (one to two meters) around the clutch location. In the rest of my observations I used large natural rock to mark distances ( 0 .5, 1, 1.5 meters) around the nest. I recorded chase distance based on rock placement, as well as distance measured with the dive r's tape when possible. I found and observed eleven different nest sites in this study, seven of which were at Isla David. All data were recorded with a waterproof notebook and pencil, and time was monitored with a waterproof watch. During my preliminary observations, male and female Acapulco damselfish behavior did not appear to be affected by my presence except when I moved closer than one meter and they hid Acapulco damselfish noticed my presence more quickly when I was at their eye level. Therefore, a ll subsequent observations done were done further than 1.5 meters away and close to the surface. Additionally, I used waterproofed GoPro Hero 3 and Canon digital camera to record data. Similarly, these were placed more than 1 meter from the nest. Cameras w ere weighed down and stabilized using natural rock and zip ties. If nesting Acapulco damselfish approached the camera, I either moved it further away or allowed time (3 5 min) for acclimation after approaches stopped b efore starting data collection. Videos from the GoPro and camera were analyzed frame by frame in iMovie for Mac OSX f or more observations on pair behavior and aggressive chase behavior


Stegastes acapulcoensis Parental Care Cech 5 Other fish species that occurred more than 3 times within 5 meters of a nest included Lutjanus sp., spotted green grouper (species unknown), Bodianus diplotaenia Thalassoma lucasanum white bodied, yellow and black tailed butterflyfish (species unknown), Microspathodon dorsalis and Abudefduf saxatilis I have observed S. acapulcoensis males chasin g M. dorsalis A. saxatalis and individuals from schooling butterflyfish RESULTS Parental Care Results from the 11 sampled nests show there are two forms of parental care in Stegastes acapulcoensis : paired or solitary. Paired Acapulco damselfish consistently occupy the nest and show few to no signs of aggress ive behavior towards each other. Females did not visit solitary male nests, except on one occasion where the female positioned herself near the clutch for 2 minutes, left and did not return. No nest had more than 2 Acapulco damselfish at a time, and nest protectors never changed during my observations. Based on my observations and video fo otage, there were 7 pairs and 4 solitary males guarding ne sts My data demonstrates the ma jority of the Acapulco damselfish was paired. I visited two nests with paired Acapulco damselfish repeatedly over the four days, and both remained as pairs. I cannot confirm that the females were the same throughout I can c onfirm that pairs were spawning because the eggs had developing embryos. Use of a compound and dissecting microscope at various magnification confirmed that eggs (.5 mm x 1 mm) were ovoid in shape, of yellow cream coloration, and attached to substrate with a thin fibrous filament of the same color. Video footage of both paired and solitary male S. acapulcoensis nests allowed closer examination of damselfish behavior. In the paired nest video s Acapulco damselfish showed distinct swimming behavior in the pr esence of a large approaching predator (often a div er coming to adjust a camera). I observed males outside of territory rapidly swim towards their nest as a predator approached. At the same time, I observed initially stationary females quickly swim from th e clutch location to join the male's side as they swam back into the clutch area together. On one occasion, the male turn ed to face the approaching predator. Males and females that I observed had distinct differences in movement when no apparent threat was present Males often move about the territory, spending time outsi d e in the alg al garden and the clutch area. Females remain under the shelf of the nest, close to or directly under the clutch area. In the solitary male nest video s I observed single S. ac apulcoensis spending a great majority of the time within the clutch area of the nest. In the ten minute interval of one video the solitary male left the nest (> 1.5 meters from clutch) for 58 seconds However, there may be trade offs in chasing threats ve rsus not chasing at all. This may explain why solitary males were not observed to chase as much, since they could be saving more energy by not chasing excessively every threat that comes by. Perhaps solitary males would then be able to defend true threats later on, rather than being exhausted. In both pairs and solitary males, aggressive chase swimming behavior could be described as rapid direct movement towards a threat. Three motions primarily characterized the agonistic chase. First, forward motion powe red by rapid flicking of the caudal fin. Second, a pause in motion w ith only pectoral fin movement as the threat fled. Third, a slow swim back to the clutch area using caudal fin movement I observed stationary periods during aggressive chases and relaxed swimming around the territory. After stationary periods, I observed Acapulco damselfish feed on algae or perform additional agonistic behaviors. Perhaps male and female Acapulco


Stegastes acapulcoensis Parental Care Cech 6 Proportion of Chases Made by Paired and Solitary Males !" !#$" !#%" !#&" !#'" (" !"#$#"%&#'(#)(%#%*+(,-*./( 0&.%*',/( !" !#$" !#%" !#&" !#'" (" !"#$#"%&#'(#)(%#%*+(,-*./.( damselfish observe the environment for threats or foraging opportunities during stationary periods. Chases and Chase Distance Chase data is composed of conspecific chases and heterospecific chases for a total of 63 recorded chases Chases done by male S. acapulcoen sis hold the majority of total chase data, and more than 50% of the chases were of conspecifics for both paired and solitary male Acapulco damselfish (Figure 2 A) I analyzed difference s in the total number of chases in a ten minute interval by paired and s olitary males and found the averages (# of total chases / interval) were different. Solitary males chased an average of 3.5 times a minimum of 2 and a max imum of 4 per interval (Figure 3 ). Paired males chased an average of 7.5 times a mi nimum of 4 and a max of 12 per interval There is a significant difference between t he average number of chases made by solitary and paired males (two sided t= 3.3, df= 9, p= 0 .01, conf. level= 95% ). Furthermore, solitary Acapulco damselfish chase less than paired Acapulco damselfish by (1.2, 6.9) chases. Calculations of total chase distance co nsist of both conspecific chase distances and heterospecific chase distances per ten minute observation interval. On a case by case basis, conspecific chase distance ranges were no farther than heterospecific chase distance ranges (Appendix) Paired males chased farther in total because, as mentioned above, paired males chased more per interval than solitary males chased. More than 50% of the total chase dist ance was of conspecifics for both pai red and solitary males (Figure 2 B). I analyzed the differences of chase distance based on paired and solitary males and found the averages (chase distance / interval) (Figure 4 ). Solitary males chased an average of 3.7 meters, a minimum of 2.0 and a max of 4.9 meters per interval. Paired males chased an average of 8.0 meters, a minimum of 4.0 and a max of 11.9 meters per interval. On average, paired S. acapulcoensis chase farther than solitary males (two sided t= 3.2, d f= 9, p= 0. 01, conf. level= 95% ). Furthermore, paired males chase farther than solitary by (1.2, 7.3) meters, on average. Figure 2 : Graph A shows proportion of chases (x/63) attributed to paired or solitary Acapulco males Graph B shows proportion of total chase distance attributed to paired or solitary males Solid white columns are all chases, while chevron pattern indicates conspecific chases exclusively A B Paired Solitary Paired Solitary All chases Conspecific chases only


Stegastes acapulcoensis Parental Care Cech 7 Figure 4 : Graphic incorporates all chases done by individuals and shows the range of chase distances of solitary and paired male Acapulco damselfish within the ten minute intervals. Dark bars are averages for solitary and paired males (3.7 and 8.0 m/ interval, respectively) while error bars indicate the range of chase d istance. Number of Chases Based on Parental Care Type Behavior Figure 3 : This graphic incorporates all chase data and shows the average number and range of chases made by solitary and paired Acapulco males Black bars denote the average number of chases, while error bars denote the range of the data set. Solitary Paired Range of Chase Distance per Interval by Solitary and Paired Males Solitary Paired Chase Distan ce (m) per interva l (min) N u m be r of C ha se s


Stegastes acapulcoensis Parental Care Cech 8 DISCUSSION In answer to my initial questions, my results suggest that Stegastes acapulcoensis pair during breeding season and that pairs more actively and vigorously defend their clutch. Based on available literature and personal communicat ion regarding S. acapulcoensis it is unusual to have found so many male female pairs over an extended period of time (Breder, 1966; Knapp, 1991; Itzkowitz, 1985, 1995; Horne, 1995; Eva Salas, Omar C hassin pers. comm. ). I hypothesize that the prevalence of this behavior can be explained by advantages of defensive collaboration and by parental investment. In short, defensive collaboration can best be explained as a joint, organized effort to defend a common object or purpose. In the case of Stegastes acap ulcoensis pairs, one may assume that the common factor is protection of the clutch, and pairs behave in such a way that demonstrates this. The higher level of aggression of paired A capulco damselfish demonstrated by chase number and distance suggests t hat pairs may be able to defend nests more effectively than solitary males. Additionally, i f paired male S. acapulcoensis consistently chase threats while females remain close to the clutch (as seen in the pair videos), this may suggest that coordinated behavi ors make pairs more defensively effective. It has been suggested that threats to egg safety determines parental roles in nest care (Perrone, 1979), which supports the behaviors demonstrated by male female Acapulco damselfish pairs when predators or threats were present. Perhaps because solitary paternal nest care is the most prevalent care type in Stegastes the male role in pair defense is to chase threats. The advantage of this collaborative defense may be that paired males can move more flexibly in the a bsence of visible threats with less risk to clutch safety than a solitary male would have. This is because additional defense in the nest, provided by the presence of the female, may allow males to forage more or explore the surrounding environment for pot ential threats to nest safety. It has been suggested that paired clutch care happens only if two parents working together are at least two times as successful as a single parent who invests in offspring alone (Perrone, 1979). This supports the above advant age of collaborative defense if the paired Acapulco damselfish are twice as reproductively or defensively successful as solitary males. Examples of reproductive or defensive success could be higher numbers of clutch survival or higher rates of predator det errence. Indeed, greater numbers of fish may be an effective factor to reducing predation when predators are solitary and have low prey capacity (Brock, 1960). In short, if two Acapulco damselfish are present to guard the clutch from a solitary egg predato r, they will have a greater chance at chasing it off because of strength in numbers. If t his predator manages to eat or injure the first line of defense, the male, and has low prey capacity (i.e. eats or attacks prey only once per day), then the female sti ll remains to guard the eggs. In order to see if pairs are twice or more times as effective as solitary Acapulco damselfish, more research should compare clutch size and survival, or effectiveness of predator deterrence. The prevalence of pair behavior m ay also be explained by male and female parental investment. Parental investment is governed by parental fitness. If a female decides to devote time to caring for young, rather than finding another male to mate with, then her investment focuses on increasi ng the number of surviving offspring. In the case of male Stegastes acapulcoensis and all other male parental caregivers, future fitness is i ncreased when offspring survive, so one may assume that protection and defense of the clutch should be their main objective Male Stegastes acapulcoensis and related species in Stegastes such as S. leucostictus must often defend against conspecific males attempting to spawn with breeding females or


Stegastes acapulcoensis Parental Care Cech 9 fertilize clutch eggs not yet inseminated by the father (Itzkowitz 1985, 1995; Karino, 1995) In addition to the number of offspring males father, another limiting factor of male reproductive success is the numb er of females with whom they can mate (Knapp, 1991) If a conspecific mates with a female before the nest holding male can, then his reproductive fitness is lowered. Since territorial males increase paternity likelihood and reproductive success by denying conspecific approaches to clutches and females, an Acapulco damselfish male is more likely to chase any conspecific entering his territory. Paired Acapulco damselfish may then be more effective at defending their clutch because the presence of the female e ncourages the male to be more aggressive. This likely explains why pairs chased more and farther both in total and towards conspecifics. It has also been suggested that parental roles in nest care are affected by certainty of paternity in territorial speci es (Perrone, 1979 ; Gross, 1985 ). An Acapulco damselfish male would be less likely to invest time into his clutch if he was not certain of his genetic contribution. This may be especially true of solitary males caregivers if they do not defend as vigorously against threats, as suggested by my data, especially because there is no second line of defense to protect the clutch when he is foraging, chasing, or outnumbered While male reproductive success is limited by female availability, female reproductive succ ess is limited by the number of eggs she can produce (Knapp, 1991). This suggests that females are usually the more discriminating sex, and can afford to evaluate aspects of male parental potential. Females may pair bond with males before spawning to deter mine if they effectively defend their territory. Good territorial defense may indicate that the male can protect her offspring, and therefore likely increase her fitness. This female behavior is seen in S. nigricans and S. leucostictus (Karino, 1995; Horne 1995), and in both cases the female evaluates male territory, courtship behavior, and aggression. There is no comparable set of data for S. acapulcoensis so it would be useful to investigate more aspects of female evaluative behavior to explain why fema les choose to form a pair bond, and to possibly understand why bonds last for certain times. For example, in nests wit h paired Acapulco damselfish an examination of characteristics in the male's territory (i.e. algal cover, clutch size present, nest size) or male behavior (i.e. aggression, spawning time, promiscuity) may help confirm that females form longer bonds with males with large clutch sizes and high aggression. Results along those lines could explain the trends seen in my data where pairs exhibited more vigorous nest defense. There is still much to learn from this system There is currently no explanation for why Stegastes acapulcoensis females remain as pairs for as long as I observed. In the genus Stegastes S. partitus females reside within nests for periods of on ly 30 60 minutes before they leave (Knapp, 1991 ). Most of the S. partitus females, and similarly behaving species ( Stegastes leucostictus ), use this time t o exclusively complete clutches (Knapp, 1991; Itzkowitz, 1995), which was not a beh avior I observed in pairs over the four days I conducted my study. This means that female Acapulco damselfish likely have some other motivation for pair bonding besides clutch completion. I believe this motivation is assurance of clutch survival, based off both defensive collaboration and aspects of parental investment. In the future I hope to study this species, as well as others with unusual parental care patterns, in an attempt to explain the larger question of how fish develop distinct roles in care of offspring. ACKNOWLEDGMENTS This project would not ha ve been conceivable without this program and the exceptional individuals that form it. I express both gratitude and admiration for everyone's positivity and commitment.


Stegastes acapulcoensis Parental Care Cech 10 I would like to thank my advisor Frank Joyce for his guidance throughout my data collection, as well as for challenging me to be a better biologist. I am grateful for the companionship of Emily Miao and Erica Weed during my project Our camaraderie kept m e motivated and inspired many of the questions central to my study. I would also like to recognize the whole Lara family for their unwavering kindness during both my homestay and expeditions for data collection. Finally, I appreciate the exchanges I had w ith Eva Salas and Omar Chassin, which assisted in aiding many of my findings.


Stegastes acapulcoensis Parental Care Cech 11 Work s Cited Avidor, A., Fishelson, L., Popper, D. "Biosociology and ecology of pomacentrid fishes around the Sinai Peninsula (northern Red Sea)." Journal of Fish Biology (1974 ) 6: 119 133. Bartels, P.J. "Extra territorial movements of a perennially territorial damselfish, Eupomacentrus dorsopunicans Poey." Behavior (1984) 91, 2: 312 322. Breder, C.M. and D.E. Rosen. "Modes of reproduction in fishes." T.F.H Publications (1966) p 941. Brock, V.E. and Riffenburgh, R.H. "Fish Schooling: A possible factor in reducing predation." ICES Journal of Marine Science (1960) 25: 307 317. Emery, A.R. "Comparative ecology and functional osteology of fourteen species of damselfish (Pisces: Poma centridae) at Alligator Reef, Florida Keys." University of Miami, Rosenstiel School of Marine and Atmospheric Science (1973) 650 765 Fishelson, L. "Behavior, socio ecology, and sexuality in damselfishes (Pomacentridae)." Italian Journal of Zoology (1998) 65: 387 398. Gross, M.R. and Sargent, R.C. "The evolution of male and female parental care in fishes." American Zoology (1985) 25: 807 822. Haley, M.P. and MŸller, C.R. "Territorial behavior of beaugregory damselfish ( Stegastes leucostictus ) in response to egg predators." Journal of Experimental Marine Biology and Ecology (2002) 273: 151 159. Horne, E.A. and Itzkowitz, M. "Behavior of the female beaugregory damselfish ( Stegastes leucostictus )." Journal of Fish Biology (1995) 46: 457 461. Itz kowitz, M. "Aspects of the Population Dynamics and Reproductive Success in the Permanently Territorial Beaugregory Damselfish." Marine Behavior and Physiology (1985) 12:1, 57 69. Itzkowitz, M. and Makie, D. "Habitat structure and reproductive success in th e Beaugregory damselfish." Journal of Experimental Marine Biological Ecology (1986) 97: 305 312. Karino, K. "Male male competition and female mate choice through courtship display in the territorial damselfish Stegastes nigricans Ethology (1995) 100: 126 138. Knapp, R.A, and Warner, R.R. "Male parental care and female choice in the bicolor damselfish, Stegastes partitus : bigger is not always better." Animal Behavior (1991) 41: 747 756. Kohda, M. "Diurnal periodicity of spawning activity of permanently territorial damselfishes (Teleostei: Pomacentridae)." Environmental Biology of Fishes (1988) 21: 91 100. Perrone, M.J. and Zaret, T.M. "Parental Care Patterns of Fishes." The American Naturalist (1979) 113, 3: 351 361. Robertson, D.R. "Field observations o n the reproductive behavior of a Pomacentrid fish, Acanthochromis polyacanthus. (1972) Dept. of Zoology, U. of Queensland


Stegastes acapulcoensis Parental Care Cech 12 APPENDIX


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