Reproductive ecology and endocrinology of the garibaldi damselfish, Hypsypops rubicundus (Pomacentridae)

I examined two aspects of the reproductive behavior of the garibaldi, Hypsypops rubicundus, a temperate marine damselfish with male parental care. My primary objective was to determine the relationship between female choice and male parental investment in the care of offspring. In particular, I sought to determine: (1) how the presence and developmental stage of eggs already in the nest influences female spawning site choice; (2) how male investment in current offspring varies with the number and developmental stage of eggs in his nest; and (3) how patterns of mate choice and parental investment contribute to the reproductive success of each sex. Because male courtship and parental care behaviors change during a nesting cycle, a secondary objective was to indentify associated hormonal changes that potentially cause this change in behavior. Female garibaldi showed a strong preference to spawn in nests with early stage eggs over empty nests or those with predominantly late-stage eggs. Within nests containing eggs in multiple stages of development, females always deposited their eggs among the youngest eggs in the nest. Male garibaldi exhibited behavioral tactics that would increase the mortality of eggs deposited in empty nests (first clutches) or in older broods (late clutches) and thus favor such female preference. These include: (1) cannibalism of single-clutch broods; (2) cannibalism of older eggs early in the brood-cycle; (3) cannibalism of younger eggs late in the brood-cycle; (4) increased attentiveness of larger broods; and (5) increased aggressiveness in defense of larger broods. These behaviors are consistent with the predictions of parental investment theory that males invest in current offspring in a way that maximizes the net (current plus future) benefits of paternal care. Male garibaldi actively courted females when their nests were empty. However, courtship rates declined as males acquired eggs and as those eggs aged. This was concomitant with an increase in parental egg fanning. Levels of both testosterone and 11-ketotestosterone were positively related to levels of courtship activity and inversely related to male parental egg-fanning

Factors influencing spawning site choice by female Garibaldi, Hypsypops rubicundus (Pisces: Pomacentridae)

The garibaldi, Hypsypops rubicundus, is a sexually monochromatic pomacentrid found in rocky subtidal areas of Southern and Baja California. During the spawning season, males attempt to attract females to a nest of red algae located within individually defended territories. Females were observed to enter the nests of several males before selecting one for spawning and were significantly more likely to spawn in nests that contained eggs in the early stages of development than nests with no eggs or with late stage embryos. Among empty nests, the density of red turf algae and the number of nesting males surrounding the nest were inversely related to the amount of time elapsed until a nesting male acquired the first clutch of a brood. The percentage of long algae in the nest was positively related to this measure. These results demonstrate active female choice of spawning site by female garibaldi and suggest that certain characteristics of the male-defended nest influence this choice

Low Susceptibility of Invasive Red Lionfish (Pterois volitans) to a Generalist Ectoparasite in Both Its Introduced and Native Ranges

Escape from parasites in their native range is one of many mechanisms that can contribute to the success of an invasive species. Gnathiid isopods are blood-feeding ectoparasites that infest a wide range of fish hosts, mostly in coral reef habitats. They are ecologically similar to terrestrial ticks, with the ability to transmit blood-borne parasites and cause damage or even death to heavily infected hosts. Therefore, being highly resistant or highly susceptible to gnathiids can have significant fitness consequences for reef-associated fishes. Indo-Pacific red lionfish (Pterois volitans) have invaded coastal habitats of the western tropical and subtropical Atlantic and Caribbean regions. We assessed the susceptibility of red lionfish to parasitic gnathiid isopods in both their native Pacific and introduced Atlantic ranges via experimental field studies during which lionfish and other, ecologically-similar reef fishes were caged and exposed to gnathiid infestation on shallow coral reefs. Lionfish in both ranges had very few gnathiids when compared with other species, suggesting that lionfish are not highly susceptible to infestation by generalist ectoparasitic gnathiids. While this pattern implies that release from gnathiid infestation is unlikely to contribute to the success of lionfish as invaders, it does suggest that in environments with high gnathiid densities, lionfish may have an advantage over species that are more susceptible to gnathiids. Also, because lionfish are not completely resistant to gnathiids, our results suggest that lionfish could possibly have transported blood parasites between their native Pacific and invaded Atlantic ranges

Enhanced understanding of ectoparasite–host trophic linkages on coral reefs through stable isotope analysis

Parasitism, although the most common type of ecological interaction, is usually ignored in food web models and studies of trophic connectivity. Stable isotope analysis is widely used in assessing the flow of energy in ecological communities and thus is a potentially valuable tool in understanding the cryptic trophic relationships mediated by parasites. In an effort to assess the utility of stable isotope analysis in understanding the role of parasites in complex coral-reef trophic systems, we performed stable isotope analysis on three common Caribbean reef fish hosts and two kinds of ectoparasitic isopods: temporarily parasitic gnathiids (Gnathia marleyi) and permanently parasitic cymothoids (Anilocra). To further track the transfer of fish-derived carbon (energy) from parasites to parasite consumers, gnathiids from host fish were also fed to captive Pederson shrimp (Ancylomenes pedersoni) for at least 1 month. Parasitic isopods had δ13C and δ15N values similar to their host, comparable with results from the small number of other host–parasite studies that have employed stable isotopes. Adult gnathiids were enriched in 15N and depleted in 13C relative to juvenile gnathiids, providing insights into the potential isotopic fractionation associated with blood-meal assimilation and subsequent metamorphosis. Gnathiid-fed Pedersen shrimp also had δ13C values consistent with their food source and enriched in 15N as predicted due to trophic fractionation. These results further indicate that stable isotopes can be an effective tool in deciphering cryptic feeding relationships involving parasites and their consumers, and the role of parasites and cleaners in carbon transfer in coral-reef ecosystems specifically

Field observation of predation on an adult Caribbean purplemouth moray eel by a nurse shark

Although predation on coral reefs has been widely studied, predation events are rarely observed. This is especially true for large and thus less common predators such as sharks, and nocturnal and/or cryptic predators (Martin and Hammerschlag 2012). Moray eels (Muraenidae) are crevice-dwelling mesocarnivores that typically feed at night, primarily upon smaller fish, octopuses, squid, and crustaceans. However, it is unclear whether moray eels themselves are subject to predatio

Localized Defecation in Territorial Herbivorous Fishes

The spatial patterns of feces deposition have been well studied in many terrestrial organisms, while few studies have examined these behaviors in marine fishes. Territorial animals tend to feed within their respective territories. Thus, individuals are faced with the decision of defecating within their territory, where they live and feed, or outside where they are potentially more susceptible to predation. In this study, we conducted behavioral observations on three species of damselfishes to quantify defecation rates and to investigate the spatial distribution of defecation events relative to territory location on Caribbean coral reefs. Defecation rates were low in the early morning and steadily increased throughout the day, peaking in the late afternoon. All 108 observed defecation events occurred outside of the territory. Additionally, 73% of individuals (n = 52) utilized the same location in successive defecation events, which is a significant departure from what would be expected were they defecating in randomly selected locations. Daily defecation rates follow previously determined rates for diurnal coral reef fishes and are closely linked to feeding behavior. However, the spatial patterns of damselfish defecation are likely related to territory maintenance, predator avoidance, or parasite avoidance. This is only the second study to investigate the spatial distribution of fecal matter in damselfishes

Territory revisits reduce intrusion during spawning trips by female yellowtail damselfish, Microspathodon chrysurus

When territory owners temporarily leave their territories, intrusion often increases. Periodic returns (revisits) may reduce intrusion, but not necessarily, because this tactic might increase total time away from the territory. The effectiveness of revisits also depends on a subsequent delay in the return of intruders. Adult female yellowtail damselfish briefly leave their territories in the early morning every 3 days to spawn. Some females make a single trip; others return to their territory several times before they finish spawning. To determine how much time females spent on revisits and whether it reduced intrusion, we observed revisits by multiple-trip females and compared intrusion on the territories of spawning and experimentally caged single-trip and multiple-trip females. If revisits reduce intrusions, multiple-trip females should have higher intrusions when caged than when spawning. If revisits show adaptive plasticity, caged single-trip females should have lower intrusion rates than caged multiple-trip females. Not counting the first trip to the male's nest and the final return trip, we estimated that spawning multiple-trip females averaged 86% of their time at the male's nest, 11% back in the territory and 3% travelling. When owners were spawning, territories of both single- and multiple-trip fish received about 5–7 min of intrusion. When owners were caged, intrusion increased significantly only on territories of multiple-trip females. We consider this the first direct evidence that revisits during temporary absences reduce intrusion on territories, suggesting that revisiting is a plastic trait that females may vary in response to intruder pressure