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Marine Spider - Desis martensi (L. Koch, 1872) 


"The spider was collected by Dr. von Martens on coral reefs at Singapore... The species is remarkable in that it has established itself in these reefs, which are only temporarily uncovered by the sea."1


Desis martensi, commonly known as the reef spider or marine spider, is one of the few marine spider species in the world, and can be found along the intertidal zones of Singapore. It was first described by Dr. Ludwig Carl Christian Koch in 1872. 2

Figure 1: Desis martensi specimen observed on a coral on Lazarus Island.

Photo credits: Ria Tan. Permission Granted

General Characteristics


Adults usually grow up to around 1cm (body length). 4 Its cephalothorax and chelicera are smooth and coloured with a deep maroon hue, while its abdomen and eight legs are covered in numerous fine hairs and are grey in colour, with an occasional pinkish tint.4

  • Photo with labels of the various parts e.g. cephalothorax, chelicera, abdomen, legs, spinnerets, eyes

Etymology


The species is named after German marine zoologist Dr Eduard von Martens, who discovered and collected the species in Singapore in 1861. It was then described by German entomologist and arachnologist Dr. Ludwig Carl Christian Koch in 1872. 1

Distribution


Desis martensi is native to Singapore, with its distribution limited to the Singapore strait. They are the only marine spider in Singapore. 5

Figure 4: Flickr map illustrating recent locations on Singapore where Desis martensi was photographed.

Taken from Wild Singapore's Flickr.com tags. Edited by Kieron Gabriel Ng.

Desis martensi was mostly sighted on the southern shores of Singapore: Sentosa (where it was first discovered), Labrador Nature Reserve's rocky shores, and the Southern Islands, with one recent sighting on Pulau Ubin. Additionally there were a few older records of sightings in the other areas along the coasts of Singapore: Tuas, East Coast Park (Not shown). 

One source has also claimed that they have been sighted along some coastlines in the Indonesian archipelago. However, this is unverified.5   

Conservation


Status

Desis martensi has not yet been evaluated by the IUCN red list.

However, it is listed as 'Vulnerable' in the Singapore Red Data Book 2008. 3

The species itself has little to no direct interaction with human beings, apart from being spotted by people exploring the intertidal zone. However, it is indirectly affection by the actions of human beings. The main threats to Desis martensi populations include land reclamation and beach enhancement projects.3

Importance to Singapore

Very few scientific studies have been conducted on Desis martensi. However, it holds great scientific importance as one of the few marine spider species present, and insights could also be gleamed from studying it's developmental processes or morphological adaptations to surviving in the intertidal habitat. 6 Thus, it is important that we protect the habitats that this spider is found in and attempt to reduce the impact of detrimental anthropogenic effects on populations such as land reclamation or pollution. 

Potential Future Efforts

As this is one of the few marine spiders in the world, and is a marine spider found exclusively in Singapore, efforts to raise public and stakeholder awareness would prove to be quite successful. As Desis martensi does not have an official common name, giving the spider a Singapore-related common name such as 'Singapore Marine Spider' or 'Singapore Reef Spider' might raise national interest and aid in conservation efforts as well.  

As the conservation status was only evaluated locally in the Singapore Red Book, it could also be useful for IUCN to conduct an evaluation as well. 

Habitat


Desis martensi is classified as a marine spider and can be found in the inter-tidal zone, in habitats such as rocky shores or coral reefs, hiding inside hollow corals or rocks, which they seal up using waterproof silk, during high tide.7 These holes are thought to be a result of Lithophaga sp. (date mussels), which bore into rock or corals.1

Desis martensi are thought to not have permanent 'nests', and might switch holes depending on prey availability. Bristowe, 1931 proposed that they would simple drag prey to the nearest available Lithophaga sp. hole after capture. 7

During low tide, they are often found scurrying around the surface of corals or rocks, or scuttling across the water surface, trying to find prey before the tide rises again. 1

Like all spiders, Desis martensi also possesses spinnerets and is able to spin webs. However, rather than for prey capture, Desis martensi utilize their webs to line the inside and outside of their nests in corals or rocks, or for sealing up holes during high tide to create air chambers.1

Furthermore, although Desis martensi is found in the intertidal habitat, and is considered to be a marine spider, it does not have the ability to respire by taking in dissolved oxygen from seawater like many other aquatic arthropods do. Thus it relies on creating air pockets or air chambers in hollow rocks or corals with waterproof webbing in order to survive high tide.8 9 1 However, it has been observed to immediately gather an air bubble when suddenly submerged in order for respiration. Similarly, fully submerging the spider will cause it to panic and attempt to reach the surface.10 9


  • Role in ecological niche?

Biology


Feeding Habits

Desis martensi, like all spiders, are carnivores, and have been observed to consume small marine invertebrates the are abundant across the intertidal zone, such as sea slaters (Figure 5 and 6). It has also been observed venturing onto the shore to hunt prey such as crickets (Figure 7).  4 They have also been observed to consume amphipods and small crabs. 7

These spiders are venomous, and are able to inject a potent toxin into their targets which paralyses them, making it easier to carry them off to nearby holes for safe consumption.11

Locomotion

They move about like normal spiders on solid substrate or in shallow water. However, they have been observed to jump from rock to rock if the tide gets too high. 7

Figure 8: Video of active Desis martensi specimens observed on St John's Island in Singapore.

Video credit: Kieron Gabriel Ng.


Desis martensi are also able to effortlessly skate across the surface of the water due to the presence of long hairs on each of their legs that prevent them from breaking the surface tension of the water (Figure 9).7

Reproduction

Desis martensi have a complex mating ritual where the males engage in 'sparring' behaviour with females. 12 Males aim to grip the chelicerae of the females with their own chelicerae, and pivot her onto her back, whereby he will mount her and begin the insemination process; inserting both palps successively (Figure 8).12

Figure 10: Drawing of Desis martensi copulation position from Bristowe, 1931. The male spider (above) is shaded in black while the female spider (below) is in white.

After mating is completed, females spin a thick waterproof silk cocoon and seal their eggs inside it.12 Each female spider is able to lay from thirty to fifty yellowish eggs at once. 12

Diagnostic


Spiders from the family Desidae can be identified with the following dichotomous key (below; Figure 11).

Figure 11: Dichotomous key of littoral spider families. Taken from Cheng, 1976.13


The behaviour of these spiders with regards to using silk to seal up holes made by Lithophaga sp. is also unique to two littoral spider families - Desidae and Agelenidae. 13

Spiders in the genus Desis are all fully marine spiders, and they generally have very similar morphological appearances due to living in similar environments, such as their elongated hairy legs that allow them to skate across the surface of the water, as well as the general characteristics of spiders in the family Desidae.14 They are also characterised by their large, forward-projecting chelicerae, widely-spaced spinnerets and a large colulus (vestigial reduced cribellum). 13

Figure 12: Drawing of Desis martensi from Bristowe, 1930.14















Figure 2: Desis martensi specimen observed on a seagrass bed on St John's Island. 

Photo credits: Ria Tan. Permission Granted


Figure 3: Desis martensi specimens observed on St John's Island in Singapore.

Photo credit: Kieron Gabriel Ng.














Figure 5: Desis martensi specimen eating a shrimp on Kusu Island. 

Photo credits: Ria Tan. Permission Granted


Figure 6: Desis martensi specimen eating a sea slater in Sentosa (Tanjung Rimau). 

Photo credits: Ria Tan. Permission Granted


Figure 7: Desis martensi specimen eating a cricket on Kusu Island. 

Photo credits: Ria Tan. Permission Granted


Figure 9: Desis martensi skating across the surface of the water at Cyrene reef.

Photo credits: Ria Tan. Permission Granted

Taxonomy & Systematics


Description


Original Description (German) (L. Koch, 1872)

The original full-length description by L. Koch in 1872 (in German) can be found here. (T4254-Desismartensi-file-1.pdf)2 The description is from pages 347-351.

English Description (Workman, 1986)

Workman, 1986 provides another description of the spider in English, with diagrammatical representation.

Figure 13: Description of Desis martensi by Workman, 1986.9

Species Concept

As the original description by L Koch occured in 1872, he likely described Desis martensi using the morphological species concept or typological species concept, based on the morphology of the spider, as the description was carried out before the biological species concept (or most other species concepts) were published. 

Type Information


The Desis martensi type specimen was collected from Singapore; on coral reefs surrounding the land mass that is presently known as Sentosa.5

It is unknown where the holotype currently is. However, syntype specimens could possibly be at the British Museum as there is information that specimens collected from Singapore were sent there.1

The type of the genus Desis is the species Desis maxillosa described by Fabricus, 1793. 15

History


Dr. Eduard von Martens first discovered Desis martensi in October 1861 after he and a colleague (Dr. Johnswick) broke open fragments of coral in the shores of Singapore. They were stunned to see several small spiders scurrying away, and initially assumed that they had brought the spiders into the intertidal zone on their clothes.1 Dr. von Martens then sent specimens to Dr. Ludwig Carl Christian Koch who described it in 1872. 1 Desis martensi was initially described as 'Desis martensii' by Koch. The second 'i' was dropped in subsequent publications mentioning the spider. It it not known why. 2

Phylogeny


Desis martensi is one of fourteen species in the genus Desis

Figure 14: Diagrammatic representation of Desis species. Information from World Register of Marine Species (WoRMS). Diagram done by Kieron Gabriel Ng. 16

Additionally, some databases also list Desis hartmeyeri (Simon 1909) in the genus Desis. However, WoRMS lists it as nomen dubiem (doubtful/ uncertain name). 17 Furthermore, some postulate that up to one third of the aforementioned species may be synonyms. More research is needed in order to resolve this. 13

The genus Desis is situated in the family Desidae (Walckenaer, 1837).18 Although the genus Desis may be one of the more well known littoral spider genera, the family Desidae is known to be one of the most difficult to characterize taxonomically. 13 Despite years of effort and study by scientists, the family Desidae remains one of the more broadly circumscribed and less well supported spider families.19 However, Wheeler et al., 2017 recently found that the genus Desis was quite distinct, and was the most divergent, from the other genera in the family Desidae (e.g. compared to sister groups Barahna and Poaka). 19

  • PUT IN THE WHEELER PAPER TREE - TO FAMILY LEVEL

Proposed Future Research

  • Further phylogenetic analysis of the Desis genus / Desidae family 
    • Future research will be needed to carry out proper phylogenetic analysis of the Desis genus. Current research on Desis martensi is sorely lacking.
  • Genetic analysis of this species - not in genbank (only desis formidabilis Histone 3 sequence inside)
  • Update resources - web of science BOLD etc not updates
  • When did the spiders become marine?

Scientific Classification


Kingdom: Animalia

Phylum: Arthropoda

Class: Arachnida

Order: Araneae

Family: Desidae

GenusDesis (Walckenaer, 1837)

Binomial Name


Desis martensi 

(L. Koch, 1872)

Glossary


Technical terms here

Other Resources


Encyclopedia of Life

NParks Flora and Fauna Web

The Biodiversity of Singapore 

Wild Singapore 

World Spider Catalog

References


Footnotes
Ref Notes
1 Pocock, R. I. (1902). On the Marine Spiders of the Genus Desis with Description of a new Species. Proceedings of the Zoological Society of London, 2, pp. 98-106. London: London Academic Press. [ a b c d e f g h i ]
2 Koch, L. (1872). Die Arachniden Australiens, nach der Natur beschrieben und abgebildet. Bauer & Raspe, Nürnberg 1, 105-368, pl. 8-28. [ a b c ]
3 Davison, G. W. H., Ng, P. K. L. & Ho, H. C. (2008). The Singapore Red Data Book (2nd Edition). Singapore: Nature Society (Singapore). 285pp [ a b c ]
4 Tan, R. (2016). Marine Spider. Retrieved November 15, 2018, from http://www.wildsingapore.com/wildfacts/arachnida/desis.htm [ a b c ]
5 Nparks Flora & Fauna Web. (2013). Desis martensi L. Koch, 1872. Retrieved November 15, 2018, from https://florafaunaweb.nparks.gov.sg/special-pages/animal-detail.aspx?id=353 [ a b c ]
6 Nparks Flora & Fauna Web. (2013). Desis martensi L. Koch, 1872. Retrieved November 15, 2018, from https://florafaunaweb.nparks.gov.sg/special-pages/animal-detail.aspx?id=353
7 Bristowe, W. (1931). LXI.—Notes on the biology of spiders.—IV. Further notes on aquatic spiders, with a description of a new species of Pseudoscorpion from Singapore. Annals and Magazine of Natural History,8(47), 457-465. doi:10.1080/00222933108673422 [ a b c d e ]
8 Tan, R. (2016). Marine Spider. Retrieved November 15, 2018, from http://www.wildsingapore.com/wildfacts/arachnida/desis.htm
9 Workman, T. (1896). Malaysian spiders. Belfast, pp. 25-104. [ a b c ]
10 Bristowe, W. (1931). LXI.—Notes on the biology of spiders.—IV. Further notes on aquatic spiders, with a description of a new species of Pseudoscorpion from Singapore. Annals and Magazine of Natural History,8(47), 457-465. doi:10.1080/00222933108673422
11 Tan, L. W. H., & Ng, P. K. L. (1988). A Guide to Seashore Life. Singapore Science Centre, 160p. 
12 Bristowe, W. S. (1931). 68. The Mating Habits of Spiders: A Second Supplement, with the Description of a New Thomisid from Kritkatau. Proceedings of the Zoological Society of London,101(4), 1401-1412. doi:10.1111/j.1096-3642.1931.tb01070.x [ a b c d ]
13 Cheng, L. (1976). Marine Insects. UC San Diego: Scripps Institution of Oceanography. Retrieved from https://escholarship.org/uc/item/1pm1485b [ a b c d e ]
14 Bristowe, W. (1930). XXXIV.—Notes on the biology of spiders.—II. Aquatic spiders. Annals and Magazine of Natural History,6(33), 343-347. doi:10.1080/00222933008673222 [ a b ]
15 Fabricius, J. C. (1793). Entomologiae systematica emendata et aucta, secundum classes, ordines, genera, species adjectis synonimis, locis, observationibus, descriptionibus. Hafniae 2, 407-428.
16 WoRMS Editorial Board (2018). World Register of Marine Species. Available from http://www.marinespecies.org at VLIZ. Accessed 2018-12-02. doi:10.14284/170 
17 WoRMS Editorial Board (2018). World Register of Marine Species. Available from http://www.marinespecies.org at VLIZ. Accessed 2018-12-02. doi:10.14284/170 
18 Walckenaer, C. A. (1837). Histoire naturelle des insectes. Aptères. Paris 1, 1-682.
19 Wheeler, W. C., Coddington, J. A., Crowley, L. M., Dimitrov, D., Goloboff, P. A., Griswold, C. E., Hormiga, G., Prendini, L., Ramírez, M. J., Sierwald, P., Almeida-Silva, L. M., Álvarez-Padilla, F., Arnedo, M. A., Benavides, L. R., Benjamin, S. P., Bond, J. E., Grismado, C. J., Hasan, E., Hedin, M., Izquierdo, M. A., Labarque, F. M., Ledford, J., Lopardo, L., Maddison, W. P., Miller, J. A., Piacentini, L. N., Platnick, N. I., Polotow, D., Silva-Dávila, D., Scharff, N., Szűts, T., Ubick, D., Vink, C., Wood, H. M. & Zhang, J. X. (2017). The spider tree of life: phylogeny of Araneae based on target-gene analyses from an extensive taxon sampling. Cladistics 33(6): 576-616. doi:10.1111/cla.12182 [ a b ]

This page was authored by Ng Weng Loong Kieron Gabriel (kieron_gabriel@yahoo.com)
Last curated on 1st December 2018

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