Showing 1 - 2 of 2 Items

Date: 2002-02-07

Creator: Amy S. Johnson, Olaf Ellers, Jim Lemire, Melissa Minor, Holly A., Leddy

Access: Open access

The shape of sea urchins may be determined mechanically by patterns of force analogous to those that determine the shape of a water droplet. This mechanical analogy implies skeletal flexibility at the time of growth. Although comprised of many rigid calcite plates, sutural collagenous ligaments could confer such flexibility if the sutures between plates loosened and acted as joints at the time of growth. We present experimental evidence of such flexibility associated with weight gain and growth. Over 13-, 4-, and 2-week periods, fed urchins (Strongylocentrotus droebachiensis) gained weight and developed looser sutures than unfed urchins that maintained or lost weight. Further, skeletons of fed urchins force-relaxed more than did those of unfed urchins and urchins with loose sutures force-relaxed more than those with tight sutures. Urchins (Strongylocentrotus franciscanus) fed for two and a half weeks, gained weight, also had looser skeletons and deposited calcite at sutural margins, whereas unfed ones did not. In field populations of S. droebachiensis the percentage having loose sutures varied with urchin diameter and reflected their size-specific growth rate. The association between feeding, weight gain, calcite deposition, force relaxation and sutural looseness supports the hypothesis that urchins deform flexibly while growing, thus determining their drop-like shapes.

Date: 2022-01-01

Creator: Maynor Alberto Loaisiga Bojorge

Access: Open access

For most of their histories, Costa Rica and Honduras were primarily agricultural societies with little economic diversification. However, around 1990, after the implementation of Washington Consensus reforms, the economies of both nations began to diverge. Costa Rica’s economy rapidly expanded for the following 30 years, while Honduras remained stagnant. Through a New Institutional Economics approach, I argue that institutional differences between Costa Rica and Honduras are responsible for the impressive economic growth Costa Rica has been able to achieve in the past few decades. Specifically, early political developments in Costa Rica have deeply imbedded relatively egalitarian values into the population, helping shape formal and informal inclusive political institutions. Meanwhile, Honduras experienced the development of extractive political institutions, as political and economic power was heavily concentrated in the hands of a select few. These political institutions were crucial during the implementation stages of Washington Consensus reforms, as strong and inclusive political institutions attracted Foreign Direct Investment that helped propel the Costa Rican economy and materialize its position as an outlier in the region. In contrast, lack of institutional guarantees discouraged foreign investors from investing money into the Honduran economy. Through a deep dive into the political histories of both nations, from European discovery to modernity, I conclude that the political institutions of these Central American nations have determined their economic growth paths.