Trade off

Parrotfish promote coral growth by controlling the abundance of algae on coral reefs. Although the importance of parrotfish herbivory on coral reefs has been noted; the feeding behavior of parrotfish is not fully understood. What is known is that territorial parrotfish defend the reef slope, forcing nonterritorial parrotfish to move to shallower water to feed. Ecological studies of predator-prey interactions suggest a correlation between risk and foraging behavior. The parrotfish on the reefs in Bonaire demonstrate a risky feeding behavior in the shallow sub-tidal zone that increases the risk of predation by osprey. A chain transect was used to determine the percent cover of algae in the shallow sub-tidal zone and reef flat. The percent cover of algae is greater in the shallow sub-tidal zone, meaning there is more food available in the habitat with higher risk of predation. In the shallow subtidal, parrotfish feed on turf algae and Padina in the same proportion as they occur on the benthos, meaning parrotfish are not feeding preferentially when in the shallow sub-tidal. To determine if there were diurnal feeding patterns in the shallow sub-tidal, observations were made 3 times per day. Initial phase parrotfish used the shallow sub-tidal zone more than terminal phase parrotfish and yellowtail parrotfish were the most abundant species. The species and phase that were most abundant may be a reflection of parrotfish populations on the reefs of Bonaire or a higher degree of crypsis. Tide levels had an impact on when the parrotfish could feed. Though most feeding occurred during morning and noonday hours, high and transitional tides were only found during these two time frames, which may explains the diurnal feeding behavior.

This student research was retrieved from Physis: Journal of Marine Science V (Spring 2009)19: 27-31 from CIEE Bonaire.

Sponges have a remarkable capacity to rapidly regenerate in response to wound infliction. In addition, sponges rapidly renew their filter systems (choanocytes)

to maintain a healthy population of cells. This study describes the cell kinetics
of choanocytes in the encrusting reef sponge Halisarca caerulea during early regeneration (0–8 h) following experimental wound infliction. Subsequently, we investigated the spatial relationship between regeneration and cell proliferation over a six-day period directly adjacent to the wound, 1 cm, and 3 cm from the wound. Cell proliferation was determined by the incorporation of 5-bromo-20-deoxyuridine (BrdU). We demonstrate that during early regeneration, the growth fraction of the choanocytes (i.e., the percentage of proliferative cells) adjacent to the wound is reduced (7.0 ± 2.5%) compared to steady-state, undamaged tissue (46.6 ± 2.6%), while the length of the cell cycle remained short (5.6 ± 3.4 h). The percentage

of proliferative choanocytes increased over time in all areas and after six days of regeneration choanocyte proliferation rates were comparable to steady-state tissue. Tissue areas farther from the wound had higher rates of choanocyte proliferation than areas closer to the wound, indicating that more resources are demanded from tissue in the immediate vicinity of the wound. There was no diVerence in the number of proliferative mesohyl cells in regenerative sponges compared to steady-state sponges. Our data suggest that the production of collagen-rich wound tissue is a key process in tissue regeneration for H. caerulea, and helps to rapidly occupy the bare substratum exposed by the wound. Regeneration and choanocyte renewal are competing and negatively correlated life-history traits, both essential to the survival of sponges. The eYcient allocation of limited resources to these life-history traits has enabled the ecological success and diversification of sponges.