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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 spiders in the world that 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. 5 The original species name 'martensi' originally had two 'i's, and was written as 'martensii' but the second 'i' was eventually dropped.2 1

Habitat


Desis martensi 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.6 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. 6 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. 5

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. 5

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.7 8 5 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.9 8

Figure 4: Video of active Desis martensi specimens observed on St John's Island in Singapore.

Video credit: Kieron Gabriel Ng.

Distribution


Desis martensi is native to Singapore. However, it has been found recently along some coastlines in indonesian archipelago. 10

Figure 5: Flickr map illustrating recent locations on Singapore where Desis martensi was photographed.

Taken from Flickr.com. Edited by Kieron Gabriel Ng.

Desis martensi was mostly sighted in the South 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 1 or 2 older records of sightings in the other areas along the coasts of Singapore: Tuas, East Coast Park (Not shown). 

TBC Turn this into a google maps instead

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. 11

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

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. 10

Biology


Feeding Habits

Desis martensi are carnivores, and have been observed to consume small marine invertebrates the are abundant across the intertidal zone, such as sea slaters. It has also been observed venturing onto the shore to hunt prey such as crickets.  7 They have also been observed to consume amphipods and small crabs. 6 These spiders are venomous, and are able to inject a paralyzing toxin into their prey.12

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. 6 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).13

Reproduction

Desis martensi have a complex mating ritual where the males engage in 'sparring' behaviour with females. 14 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).14

Figure 10: Drawing of Desis martensi copulation position from Bristowe, 1931. 

After mating is completed, females spin a thick waterproof silk cocoon and seal their eggs inside it.14 Each female can lay from thirty to fifty yellowish eggs at once. 14

Description


The original description by L. Koch in 1872 (in German) can be found here.

  • INSERT THE ORIGINAL GERMAN DESCRIPTION HERE 

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

Figure 11: Description of Desis martensi by Workman, 1986.8

Diagnostic


Spiders in the genus Desis generally have very similar morphological appearances.15

Figure 12: Drawing of Desis martensi from Bristowe, 1930.

TBC Species Concepts

TBC Comparison Table

Type Information


The type specimen was collected from Singapore; on coral reefs surrounding the land mass that is now known as Sentosa.10 It is unknown where the holotype currently is. However, it could possibly be at the British Museum.1

The type of the genus Desis is the species Desis maxillosa described by Fabricus, 1793. 16

History


Dr. Eduard von Martens first discovered Desis martensi 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

  • Changed family


Phylogeny


Desis martensi is situated in the family Desidae (Walckenaer, 1837).17 The family Desidae is one of the more broadly circumscribed and less well supported spider families despite years of effort and study by scientists.18 Recently, Wheeler et al., 2017 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). 18

  • PUT IN THE WHEELER PAPER TREE - TO FAMILY LEVEL

Proposed Future Research


  • Motivate more future studies
    • Common name for easy science communication/ outreach
    • Outreach to Singaporeans - make people aware of this spider
  • Evaluate IUCN threat
  • Further phylogenetic analysis of the Desis genus / Desidae family 
    • Future research will be needed to carry out proper phylogenetic analysis of the Desis family. 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?

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. (1833). On the Marine Spiders of the Genus Desis with Description of a new Species. In Proceedings of the Zoological Society of London(pp. 98-106). London: London Academic Press. [ a b c d e ]
2 Koch, L. (1872a). Die Arachniden Australiens, nach der Natur beschrieben und abgebildet. Bauer & Raspe, Nürnberg 1, 105-368, pl. 8-28. [ a b ]
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 ]
4 Tan, R. (2016). Marine Spider. Retrieved November 15, 2018, from http://www.wildsingapore.com/wildfacts/arachnida/desis.htm [ a b ]
5 Pocock, R. I. (1833). On the Marine Spiders of the Genus Desis with Description of a new Species. In Proceedings of the Zoological Society of London(pp. 98-106). London: London Academic Press. [ a b c d ]
6 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 ]
7 Tan, R. (2016). Marine Spider. Retrieved November 15, 2018, from http://www.wildsingapore.com/wildfacts/arachnida/desis.htm [ a b ]
8 Workman, T. (1896). Malaysian spiders. Belfast, pp. 25-104. [ a b c ]
9 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
10 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 ]
11 Davison, G. W. H., Ng, P. K. L. & Ho, H. C. (2008). The Singapore Red Data Book (2nd Edition). Singapore: Nature Society (Singapore). 285pp
12 Tan, L. W. H., & Ng, P. K. L. (1988). A Guide to Seashore Life. Singapore Science Centre, 160p. 
13 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
14 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 ]
15 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
16 Fabricius, J. C. (1793). Entomologiae systematica emendata et aucta, secundum classes, ordines, genera, species adjectis synonimis, locis, observationibus, descriptionibus. Hafniae 2, 407-428.
17 Walckenaer, C. A. (1837). Histoire naturelle des insectes. Aptères. Paris 1, 1-682.
18 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 ]








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 6: Desis martensi specimen eating a shrimp on Kusu Island. 

Photo credits: Ria Tan. Permission Granted


Figure 7: Desis martensi specimen eating a sea slater in Sentosa (Tanjung Rimau). 

Photo credits: Ria Tan. Permission Granted


Figure 8: 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

This page was authored by Ng Weng Loong Kieron Gabriel (kieron_gabriel@yahoo.com)
Last curated on 16th November 2018

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