Feeding preferences of the herbivorous crab Grapsus albolineatus:the differential influence of algal nutrient content and morphology

Abstract

The tropical rocky shore crab Grapsus albolineatus selectively consumes rare filamentous algae over more abundant foliose algae during the wlnter in Hong Kong. Laboratory experiments have shown that growth of G. albolineatus is enhanced and mortality reduced when given a diet of filamentous algae as opposed to fohose algae. In the laboratory, G. albolineatus consumed filamentous algae (Enteromorpha clathrata, Hincksia mitchelliae and Chaetomorpha antennina) in greater amounts than any foliose algae (Dermonema frappieri, Pterocladia tenuis, Porphyra suborbiculata. Ulva fasciata, Endarachne binghamiae) in both multiple choice and no choice experiments. The most energy-rich alga was Pterocladia, while Porphyra had the highest protein content. Filamentous algae had lower overall nutrient contents than foliose algae. Consumption rates for Enteromorpha and Hincksia were, however, sufficiently higher than for Porphyra, which ensured that the net intake of nutrients per day was greater. Even though protein assimilation efficiency was higher for Porphyra than Hincksia, G. alboljneatus assimilated more protein, per day, from Hjncksia. When the confounding effects of morphology and nutrient value were separated, by offenng the crab choices of commercially available algae (Laminaria sp.) cut into different forms (foliose and filamentous), G. albolineatus showed a strong preference for the filamentous form, despite both forms having the same nutrient value. Preference for filamentous forms is likely to be constrained by the morphology of the chelae, which have delicate tips, and appear unable to tear foliose algae. Algal morphology, therefore, appears to be of prime importance and the nutrient content and digestibility of algae of secondary importance in determining the feeding preferences of G. albolineatus. The high consumption rate of filamentous algae outweighs their relative nutrient deficiencies, indicating that they are better suited to meeting the physiological needs of the crab than foliose algae.

Food Habits of Two-Year-Old Chinese Mitten Crab (Eriocheir sinensis) Stocked in Lake Bao'an, China

“…This may also be possible for juvenile mitten crabs. In other crab species, algae often appeared in food remains, such as carnivorous Portunuspelagicus (Wu and Shin 1998), herbivorous Grapsus albolineatus (Kennith and Williams 1996), and omnivorous Pleuroncodes planipes (Anomura, Galatheidae) (Aurioles-Gamboa and Perez-Flores 1997). Studies of the stomach contents of P planipes, showed that in March, the most abundant diatom genera were Nitzschia, Melosira and Cocconeis in that order, which accounted for 74% of the relative importance index.…”

Macroalgal traits and the feeding and fitness of an herbivorous amphipod: the roles of selectivity, mixing, and compensation

“…Marine algae vary considerably in their nutritional, chemical, and structural composition, thus providing a heterogeneous and variable food resource for marine herbivores (Hay & Fenical 1988, Neighbors & Horn 1991, Paul 1992, Bolser & Hay 1996, Kaehler & Kennish 1996, Kennish & Williams 1997, Wakefield & Murray 1998, Poore & Steinberg 1999. Because herbivores eat foods that are much lower in nutrients than their own tissues (Southwood 1973, Mattson 1980, White 1993, Sterner & Hessen 1994, Gulati & DeMott 1997, they display a diversity of behavioral and physiological adaptations to cope with the low nutritional value of their foods (Mattson 1980, White 1993.…”

Geographic variation in decoration selectivity of Micippa platipes and Tiarinia cornigera in Japan

“…It is unlikely that food preferences are driving decoration preferences, since preferences for food and decoration were decoupled, both in our study and in a previous study of Micippa and Tiarinia (Sato & Wada 2000). Handling time considerations might be important; morphology has been known to strongly influence food selection in grapsid crabs (Kennish & Williams 1997), and some authors suggest that handling time constraints could influence preferences in decorator crabs (Stachowicz & Hay 2000, Cruz-Rivera 2001. Indeed, the fleshy turf morphology of H. pannosa species may be easier to cut and handle than Corallina pilulifera, which is calcified.…”

“…Both species bear hooked setae over the majority of their carapace, and they decorate these setae with small turf algae found in the intertidal (Dudgeon 1980, Sato & Wada 2000. Species composition and abundance of algae in this region shifts seasonally (Kennish 1997, Sato & Wada 2000; algal coverage is generally lowest in the summer, when intertidal areas are dominated by small and/or juvenile turf algae, and highest in winter, when arborescent brown algae such as Sargassum spp. dominate.…”

“…Although this necessitated direct comparisons of alga wet-mass (crab utilization) with alga percent cover (field availability), the species of algae used in the study had similar morphologies (low-growing turf), and relative percent cover/wet-mass relationships were similar. Although we use percent cover data in all graphs, we also converted percent cover data to biomass data using formulae (Kennish 1997) published for similar species of algae in Hong Kong that were qualitatively similar to the volume-mass conversion factors calculated for Shirahama algae (M. Sato unpubl. data), and ran all calculations and statistics using percent mass data.…”