Lim, Shirley S. L.

The functional morphology of maxilliped-setation in three species of fiddler crabs—Petruca panamensis, Leptuca terpsichores and L. beebei— collected from Panama were studied using a comparative ecomorphological approach. The coverage of spoon-tipped (ST) and plumose (P) setae on the inner surface of the second maxilliped were noted, and the abundance of each setal type was enumerated, with crab carapace width as the covariate. These attributes were then related to the sediment particle size characterization of their respective collection sites for an ecomorphological comparison. All three species have mixed setation, albeit in different proportions of coverage. For L. terpsichores, the ST:P coverage was consistently ca. 70%:30% whereas there was approximately equal coverage of both setal types (i.e., 50% ST:50% P) on the maxillipeds of L. beebei and P. panamensis. Analysis of Covariance (ANCOVA) results of setal counts between the sexes in each species showed that the number of ST and P setae did not differ significantly between males and females, indicating an absence of sexual dimorphism in mouthpart setae. When all three species were compared—sexes combined within each species— ANCOVA results reveal that for any crab of a given size, there were significantly more ST setae on the second maxilliped of L. terpsichores (sediment from sampling site classified as ‘moderately-sorted medium sand’) than L. beebei (sediment from sampling site classified as ‘moderately-sorted fine sand’) and P. panamensis (a rocky-habitat species); no significant difference was detected between ST abundance in the latter two species. Current results provide unequivocal quantitative evidence that the abundance of ST setae can be an indicator to differentiate habitats down to the level of different sand-grain size, i.e., medium sand versus fine sand habitats of L. terpsichores and L. beebei, respectively. Both L. beebei and P. panamensis had significantly fewer ST setae than L. terpsichores, possibly because the former two species’ habitats have sediments with sand grains that are less coarse than the latter’s. On rocks, P. panamensis does not produce pseudofecal pellets as they directly swallow food materials pinched from the rock surfaces without sorting, rendering the role of ST setae of secondary importance. The three species did not differ significantly in P setae abundance, suggesting that the adaptive function of this type of setae to habitat characteristics remains debatable. The significance of ST setae as an ecomorphological adaptation for efficient food extraction from sandy sediments is, thus, evident in L. terpsichores. As for other two species—L. beebei and P. panamensis—that live in environments with finer sediment grain sizes, the adaptive role of ST setae is of diminished functional importance. Fiddler crab species with mixed setal types may have greater potential to exhibit feeding plasticity should their habitats be threatened.

The temporal-spatial resource use patterns of juvenile and adult Ocypode gaudichaudii were studied by comparing the zonation patterns and activity budgets of the two life stages at Culebra Beach, Panama. Burrow distribution of the crabs during the day and at night was studied over six months. Diurnal activity budgets of 46 crabs (22 juveniles and 24 adults) were determined by observing seven predominant behaviors upon emergence from their respective burrows when the burrow zone is uncovered after the tide recedes. The behaviors comprise three foraging-related activities (i.e., deposit-feeding, scavenging, and probing for food), the maintenance of burrow, walking, staying within the burrow, and resting at the burrow entrance. Juvenile crabs occupied a higher intertidal zone than the adults and had a higher emergence rate at night. This temporal-spatial habitat partitioning could possibly reduce intraspecific competition between the two life stages, thereby enabling their coexistence in the habitat as well as increasing the survival rate of the juveniles, potentially raising the carrying capacity of the population at Culebra Beach. All 46 crabs—regardless of life stage—spent the highest mean proportion of time on foraging-related activities. Out of the three feeding-related behaviors, adults spent most time on deposit-feeding while juveniles spent most time probing. Only juveniles scavenged. In both life stages, a similar proportion of time was spent maintaining the burrow and staying within the burrow.

Larder hoarding behavior in central place foragers has been widely studied in vertebrates, albeit, not as extensively as scatter hoarding. However, scant information is available for the invertebrate taxa, especially aquatic species. We investigated this phenomenon via an in situ food supplementation experiment in a community of two sympatric fiddler crabs, Austruca annulipes (n = 80; 40 males and 40 females) and Gelasimus vocans (n = 60; 30 males and 30 females), in a Singapore mangrove patch with an intermediate resource level. As the semiterrestrial intertidal crabs can only forage after emergence from their burrows during exposure period, the duration of time available for feeding is finite and constitutes an important constraint in the optimization of food intake. The activity budget (in terms of time spent on feeding activities, all above-ground non-feeding activities, and burrow-sequestration) as well as the occurrence (if any) of larder hoarding behavior in these two species after they first emerged were recorded by hourly intervals (three hours of observation) to determine the effect of time left for foraging on larder hoarding. Regardless of species, A. annulipes and G. vocans spent most of the time feeding when the tide was out, despite overall significant behavioral heterogeneity (multivariate analyses using ANOSIM) indicating that both species prioritized hunger satiation over other activities. Our results also showed that although the two sympatric crabs live in the same mangrove area with similar food resource levels, only A. annulipes larder hoarded. The propensity to larder hoard did not differ significantly between the sexes, nor among the three time periods of the feeding duration. Gelasimus vocans, one of the species of crabs known to form feeding droves, did not larder hoard at all. We propose that A. annulipes is a species that can deploy larder hoarding as a foraging strategy when it encounters valuable food resources, and such a strategy is highly advantageous for the species as it generally inhabits sandy habitats that are poor in nutrient levels. Hence, larder hoarding can be considered a mixed evolutionarily stable strategy (ESS) adopted by A. annulipes. In contrast, G. vocans that commonly inhabits muddy sediments—with a high level of food resources—did not larder hoard, even when provided with supplemented food, suggesting perhaps that its mixed ESS is droving behavior.

There are several definitions of Problem Based Learning (PBL). For example, those of the Basudur Simplex Model, Kaufman and Swartz. The common features are: 1) Find and define the problem; 2) Examine facts and possibilities; 3) Consider alternative solutions; 4) Implement the best solution and 5) Problems should be related to the “real world”. However, in the natural sciences and mathematics, one often proceeds from “real world” problems to the conceptualisation of the abstract. Conceptualisation of the abstract is one of the tenets of the natural sciences and mathematics. Perhaps it is required less in the biological sciences, but it is increasingly required in physics and almost entirely in mathematics. The usual definitions of PBL have to be adapted to take into account the fact that conceptualisation of the abstract, rather than solving “real world” problems, is the end-product of many problems in the scientific disciplines. We give examples and counter-examples of the applicability of PBL integrated with information technology in our disciplines.

In this paper, we discuss our efforts in curriculum development of an environmental science module that will be conducted in a networked teaching and learning environment, complemented by laboratory sessions and field work. The aim of the curriculum is to promote collaborative and distributed learning of environmental science that emphasizes the acquisition of higher order thinking skills. Some aspects of the curriculum that will be highlighted include the contents of an interactive multimedia teaching system for self-paced learning, and scenario generators that allow the participants to experiment with hypothetical environmental situations.

This report details the three keys aspects of the project ─ (a) the ideas and motivation of teachers to carry out inquiry, (b) students ideas about science learning in school, and (c) factors that could enhance science teacher professional development to carry out inquiry. In elementary science classrooms, we showed that: (1) while teachers express moderate to strong intention to teach science through inquiry they are constrained by numerous components in their classroom context, including goals of instruction, curriculum integration, learning environment, lesson strategies, student disposition and teacher disposition; (2) students value hands-on and collaborative experiences for learning science, suggesting a pedagogy characterized by clear learning goals and valuing a sense of community among learners; and (3) further training should focus on how to, more than why, teach through inquiry, adopting a paradigm that is responsive to different contexts.

Biology is a difficult and boring subject for many students and university enrollments for the discipline all over the world have not been encouraging for the past decade. One of the main reasons for the poor "image" of biology has always been blamed on the descriptive and jargon-filled nature of the discipline. With the current emphasis on the life sciences in Singapore, there is a dire need to review and develop biology teaching strategies that would facilitate the learning of the discipline as well as improve the attitudes of students to the subject and to themselves.

In this study, some major theories on the improvement of biology teaching are outlined. This is followed by a systematic review of specifically designed teaching strategies such as (1) the word roots system to overcome the terminology syndrome; (2) appropriate use of multimedia; (3) problem based learning (PBL); (4) outdoors and field based laboratories and, assessment strategies.

Results of a survey administered to the author's students showed that students were highly positive about the learning, teaching and assessment strategies implemented in the modules that the author taught (i.e., NAB311 "Invertebrate Zoology", BAB203 "Lower and Higher Animals", NAB319 "Ecology and Biostatistics" and NRE381 "Research Exercise"). Further modifications in the curricula of the various modules to improve the teaching of biology were briefly discussed based on the results of the survey and current literature.

In this paper, we characterize the inquiry practices of four elementary school teachers by means of a pedagogical framework. Our study surfaced core components of inquiry found in theoretically-driven models as well as practices that were regarded as integral to the success of day-to-day science teaching in Singapore. This approach towards describing actual science inquiry practices - a surprisingly neglected area - uncovered nuances in teacher instructions that can impact inquiry-based lessons as well as contribute to a practice-oriented perspective of science teaching. In particular, we found that these teachers attached importance to (a) preparing students for investigations, both cognitively and procedurally; (b) iterating pedagogical components where helping students understand and construct concepts did not follow a planned linear path but involved continuous monitoring for learning; and (c) synthesizing concepts in a consolidation phase. Our findings underscore the dialectical relationship between practice-oriented knowledge and theoretical conceptions of teaching/learning thereby helping educators better appreciate how teachers adapt inquiry science for different contexts.

An oil spill occurred in the Straits of Singapore (one of the world’s busiest shipping lanes) on 25 May 2010. Pre- and post-oil spill population parameters (i.e., abundances, densities, burrow diameters, location of burrows with respect to shore height and size-distribution gradient) of the ghost crab Ocypode ceratophthalmus on two adjacent beaches at East Coast Park, Singapore, were compared to study the extent of impact and subsequent recovery rate. The ghost crab population, which was decimated after the oil spill, rebounded within three months to densities close to those that were observed prior to the oil spill. The lower boundary of the recolonised population in September 2010 and January 2011 shifted upshore by about 0.4 m from that documented in September 2006. The zone that was recolonised was between 2.6 m and 2.8 m above Chart Datum in January 2011, directly above the upper limit of the region contacted by the spilled oil, indicating that the crabs avoided settling in sediments that contained oil residues. No distinct size distribution gradient on the shore was observed in the pre- and postspill populations. This study confirms that the abundance and distribution of O. ceratophthalmus provide reliable, sensitive and effective indications of the conditions of beach habitats.

The feeding strategies of Ocypode gaudichaudii at two sandy beaches, Culebra Beach (CB) and Playa Venao (PV) in Panama, were studied via three experiments. Two separate manipulative in situ experiments were conducted to determine how the densities of food resources and the size of the supplemented food offered to the crabs can affect their diet and food handling behavior. The third experiment, a transplantation study, was also conducted to determine the plasticity of the feeding behavior of the displaced crabs. In the first experiment, freshly-emerged crabs showed different feeding modes when washed-sediment was seeded with different densities of diatoms and rove beetles, which suggests that they are optimal foragers. Crabs hoarded food in the second experiment when food augmentation was performed, in which small and large food pellets were placed around the burrows at the beginning and end of the crabs’ feeding cycle. All freshly-emerged crabs from both sites foraged on the small pellets outside their burrows and did not cache food; when pellets were provided at the end of the feeding cycle, crabs from CB fed on some of the small pellets and returned to their burrows with the uneaten pellets left on the surface, whereas crabs at PV picked up all the small food pellets and transferred them into their burrows over several trips before plugging their burrow entrances. Only the crabs from PV carried the large food pellets supplemented at the start and end of the feeding cycle into their burrows. In contrast, the crabs at CB often left behind the partially-eaten pellets on the sand surface, probably due to the increased risk of predation associated with the prolonged handling time of the large food pellets. Excavation of the burrows of the crabs that hoarded food showed that all the pellets were deposited at the bend of the burrows, indicating that they were not consumed immediately. Crabs that fed in droves at PV stopped droving and foraged around their burrows after being transplanted to CB. This is the first documentation of food hoarding in a sandy beach macroinvertebrate at a resource-impoverished habitat. The plasticity of feeding strategies adopted by the painted ghost crab in response to different densities of food resources in the habitat could be an adaptation to the dynamic sandy beach environment.