A massive subtidal aggregation of hermit crabs in Surprise Atoll lagoon, New Caledonia

[2015]

A unique aggregation of hermit crabs is described at Surprise Atoll lagoon, New Caledonia.

A massive subtidal aggregation of hermit crabs in Surprise Atoll lagoon, New Caledonia

Coral Reefs (2015) 34:917
By Nathaniel Evans, Antoine Gilbert, Serge Andréfouët, Gustav Paulay
April 11, 2015

Many hermit crab species can form large aggregations, sometimes numbering thousands of individuals (e.g., Gherardi and Vannini 1992). Research suggests that such clustering behavior can reduce predation risk and positively influence feeding, reproduction, and shell exchange. While clustering is well documented among lineages inhabiting terrestrial and intertidal zones, it remains poorly studied at subtidal depths where the greatest hermit crab diversity exists. Thelimited work that has examined this behavior across multiple habitats found clustering to be rare or entirely absent among species occupying subtidal depths (including in six Dardanus species; Barnes and Arnold 2001, but see Ramsay et al. 1997). Here, we report clustering behavior in the subtidal hermit crab species Dardanus scutellatus (H. Milne Edwards, 1848) that formed a massive aggregation of tens of thousands of individuals from 10 to 15 m depth (Fig. 1). Observations were made at approximately 0830 hrs, November 24, 2013 in the remote Surprise Atoll of Entrecasteaux Reef (New Caledonia), on a gently
sloping lagoon bottom of sand-covering pavement near 18.4775S, 163.0835E. Though our survey was verylimited (<25 min, covering approximately 250 m), we did not visually locate the end of this cluster. We also saw no obvious signs of a significant food source that might have attracted these crabs. No other benthic fauna was observed, but sea snakes swam through the area. To our knowledge, such a large subtidal aggregation has never been formally reported, although scientific divers recorded a similar event 15 December 2009 in a similar habitat on Beautemps-Beaupre´ Atoll (Laboute, pers. comm.). The novelty of this observation emphasizes that our knowledge of clustering behavior in hermit crabs remains incomplete.

From Mangrove Mud to Meaningful Work: Desta’s J.A.M.I.N. Journey

Some students I remember for their grades, their quick answers, or a moment that made the whole class laugh. Others I remember for the way they stepped into the mangroves.

Desta was the kind of student who thrived outdoors. While some students hesitated at the edge of the mud, he walked right in. And when he inevitably got stuck — because everyone does — he didn’t get frustrated. He laughed. Covered in mud, holding mangrove propagules in his hands, he embraced the experience fully.

Even then, it was clear that he was connecting with the environment in a way that went beyond the lesson plan…

From Students to Stewards: A Full-Circle Moment for J.A.M.I.N.

There are certain faces you never forget.

Over the years, hundreds of students have stepped into mangrove forests with us through the Jamaica Awareness of Mangroves in Nature (J.A.M.I.N.) program. I may not always remember every name, but I remember the expressions — the hesitation before stepping into thick mud, the laughter when someone loses a shoe, the look of surprise when they catch that unmistakable sulfur smell rising from the mangrove soil…