New findings on the fore-leg evolution of assassin bugs

Gardena_thumbnailAssassin bugs (Reduviidae) have evolved a rich arsenal of weaponry for prey capture in their 178 million years of diversification. With about 7,000 known species worldwide, the corresponding variety of strategies to take down their next meal consist of lethal combinations of deceit and different ways to incapacitate their prey.

A team of researchers, including our museum entomologists, Hwang Wei Song and Rudolf Meier, published their latest findings on how the assassin bugs’ fore-leg evolved to the diversity we see today.

Scadra costalis_thumbnailThe fore-legs of the assassin bugs are often involved in prey capture, and have undergone remarkable modifications, presumably as an adaptation to a range of hunting techniques. Some assassin bugs possess a pair of enlarged fore-legs, frequently armed with spines or stiff bristles that aid in grasping prey. However, there are also fore-legs that look unmodified, in some cases coupled with the ability to produce or obtain sticky secretions as an alternative method to trap prey. Attempts to explain for the observed variety in leg modifications across the entire group were not formally tested until now.

In the study, specialized leg structures that are hypothesized to be involved in prey capture were tested to see if the loss of one can be explained by the replacement with another. To trace the evolution of the fore-leg structures, the phylogeny (evolutionary relationships) of assassin bugs was first reconstructed using a novel method combining transcriptomic RNA-derived data (all expressed genes of an individual) and a conventional DNA dataset (Sanger sequencing-derived). This results in the establishment of deep phylogenetic relationships that proved elusive previously.


Fossula spongiosa (fs) in different assassin bug species.

With this latest phylogeny, a specialized leg structure called the “fossula spongiosa”, a spongy pad thought to improve the grip on prey, is shown to be most primitive and already present in the last common ancestor of all assassin bugs. This structure was then lost multiple times throughout the history of assassin bug diversification. Surprisingly, this is not necessarily replaced by other leg modifications. Our results indicate other behavioural and structural adaptations may have a stronger influence shaping the fore-legs. This finding now shifts the attention towards testing the role of other predatory adaptations such as the toxicity of the saliva injected to immobilize prey on the raptorial leg evolution of assassin bugs.

This study was funded by Singapore’s Ministry of Education AcRF Tier 1 grant, US National Science Foundation’s “Partnership in Enhancement of Expertise in Taxonomy” and Assembling Tree-of-Life grants.


Original paper:
Zhang, J. et al. Evolution of the assassin’s arms: insights from a phylogeny of combined transcriptomic and ribosomal DNA data (Heteroptera: Reduvioidea). Sci. Rep. 6, 22177; doi: 10.1038/srep22177 (2016)

Temasekia: 50 Plants and Animals Native to Singapore available in stores

Back by popular demand—Temasekia: 50 Plants and Animals Native to Singapore is on its second print run!

Temasekia cover

The book is now available at the LKCNHM Museum Shop, NUS Multi-Purpose Co-operative Society Ltd (Science, LT27), Kinokuniya SingaporeSelect Books and Nature’s Niche.

More about the book:

Temasekia: 50 Plants and Animals Native to Singapore celebrates the biodiversity of Singapore and discoveries throughout the nation’s history. The species featured in this book were described from specimens collected from Singapore, with some bearing a scientific name related to the history, geography, folklore or cultural heritage of Singapore. A select few are found only in Singapore and nowhere else in the world. All these organisms are the life and soul of the land first known as Temasek, which was the earliest name of the island and settlement located on the present day Singapore. These are the “original Singaporeans”.

Split Identity: The Flower Crab is Actually Four

The commonly eaten flower crab or swimming crab actually comprises 4 species.

Portunus Lai et al

These crabs that were all formerly known as Portunus pelagicus are now A) Portunus pelagicus, B) P. segnis, C) P. reticulatus, and D) P. armatus. Photo by Joelle Lai.

This research finding recently featured on The Straits Times was published in the Raffles Bulletin of Zoology in 2010 by museum staff Dr Joelle Lai, Prof Peter Ng and Dr Peter Davie of the Queensland Museum.

It shows the importance of biodiversity research and its applications in the management of commercial fisheries, particularly of the concern about over-harvesting.

Read the Straits Times report here:

Read the original research paper here:  A Revision of the Portunus pelagicus (Linnaeus, 1758) species complex (Crustacea: Brachyura: Portunidae), with the recognition of four species.

A Roadkill Record of a Hairy-Nosed Otter from Selangor, Peninsular Malaysia

Dr Tan Heok Hui from the Lee Kong Chian Natural History Museum documented a roadkill of a hairy-nosed otter (Lutra sumatrana)

Unlike some of the more commonly encountered species of otters, the hairy-nosed otter is an elusive and rarely encountered animal throughout its native range in Southeast Asia.

The dead otter was a female 1.2m in length and its location was less than four meters away from the nearest water source, a black water creek running parallel to the road. the dampness of its coat of fur probably suggests that the otter met its end right after it left the creek and onto the road.

This record was recently published in the IUCN/SCC Otter Specialist Group Bulletin and you can read more about the article here!