Observations of a Semi-Aquatic Spider Attack: an Overlooked Fish Predator in A
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Observations of a Semi-Aquatic Spider Attack: An Overlooked Fish Predator in a Well Studied Ecosystem? Amy E. Deacon, Aidan D. Farrell and Douglas F. Fraser Deacon, A. E., Farrell, A. D., and Fraser, D. F. 2015. Observations of a Semi-Aquatic Spider Attack: An Overlooked Fish Predator in a Well Studied Ecosystem? Living World, Journal of The Trinidad and Tobago Field Naturalists’ Club , 2015, 57-59. NATURE NOTES OEVHUYDWLRQ RI D SHPLATXDWLF SSLGHU AWWDFN AQ OYHUORRNHG )LVK 3UHGDWRU LQ D Well-Studied Ecosystem? We describe here a noteworthy spider encounter that Nyffeler and Pusey (2014) reviewed accounts of took place on the bank of the Ramdeen Stream in Trin- VSLGHU SUHGDWLRQ RQ ¿VK ZRUOGZLGH E\ FROODWLQJ SXE- LGDG¶V $ULPD 9DOOH\ ¶´1 ¶´: RQ lished and anecdotal reports. According to this paper, the August, 2014. This stream forms part of one of the most VLJKWLQJ GHVFULEHG KHUH LV WKH ¿UVW UHFRUGHG LQFLGHQFH RI intensively-studied freshwater ecosystems in the tropics; ¿VK SUHGDWLRQ E\ D VSLGHU LQ 7ULQLGDG 7KLV LV PRVW OLNHO\ for more than four decades international researchers have because few people have witnessed the event, and/or that been visiting this valley to discover more about the ecology previous descriptions have remained unpublished rather DQG HYROXWLRQ RI WKH ¿VKHV WKDW LW VXSSRUWV ± SULPDULO\ WKH WKDQ UHÀHFWLQJ WKH DFWXDO UDULW\ RI ¿VK SUHGDWLRQ E\ VSLGHUV Trinidadian guppy Poecilia reticulata DQG WKH NLOOL¿VK The pools in this case are manmade, but mimic pools Rivulus hartii (recently revised as Anablepsoides hartii). that are often found in such habitats and are naturally col- This unrivalled body of research has greatly expanded our RQLVHG E\ ULYXOXV 2YHU WKH FRXUVH RI SRRO YLVLWV E\ WKH understanding of natural selection, evolution and commu- DXWKRUV RYHU WZR \HDUV ¿VKLQJ VSLGHUV ZHUH REVHUYHG LQ nity ecology (Magurran 2005). RI FDVHV DQHFGRWDO HYLGHQFH VXJJHVWV WKLV IUHTXHQF\ A series of semi-naturalistic pools have been construct- is typical of the stream over the past two decades (unpub- ed on the bank of this second-order stream to study interac- lished data). One of the authors (DFF), who has worked in tions between guppies and rivulus as part of another study. this habitat for over two decades, has seen a spider with :KLOH FRQGXFWLQJ D ¿VK FHQVXV RI RQH RI WKHVH SRROV LQ WKH rivulus in its grasp before (unpublished observation) but PLGDIWHUQRRQ DURXQG K D ODUJH PDOH ULYXOXV a never witnessed the attack itself. mm) jumped out of the pool and onto the surrounding leaf $FFRUGLQJ WR 1\IIHOHU DQG 3XVH\¶V UHYLHZ RI UH- litter, attempting to evade the dip net with its characteristic SRUWV RI ¿VK SUHGDWLRQ E\ VSLGHUV FDQ EH DWWULEXWHG WR WKH WDLOÀLS :LWKLQ VHFRQGV EHIRUH LW ZDV SRVVLEOH WR FDSWXUH IDPLO\ &WHQLGDH 7KH YDVW PDMRULW\ DUH DVVRFLDWHG WKH ¿VK D ODUJH VSLGHU KDG OHDSW RQWR LW JUDVSLQJ LW ¿UPO\ with Dolomedes sp. of the family Pisauridae; this family After a few minutes, possibly disturbed by the presence LV DOVR SUHVHQW LQ 7ULQLGDG 6HZODO DQG &XWOHU of the observers, the spider moved a few centimetres to- A. bogotensis is typically found on banks or on aquatic wards the pool and rested on the water (Fig. 1). It then re- vegetation, ready to attack when the surface of the water climbed the bank and remained there, completely still, with LV GLVWXUEHG %U]RVWRZLF] DQG *UHYHQ ,Q D VHSDUDWH WKH PRWLRQOHVV ¿VK VWLOO LQ LWV JUDVS IRU VRPH WLPH )LJ encounter, at the same pool around one year earlier, two The authors are very familiar with R. hartii and have of the authors witnessed a similar spider, poised, abdomen a good intuition for estimating lengths of this species vi- out of the water with its thorax submerged vertically; on VXDOO\ 7KHUHIRUH WKH HVWLPDWHG OHQJWK RI WKH ¿VK PP being disturbed, the spider swam underwater across the was used to calculate the size of the spider using the pool and emerged on the other side. Indeed, A. bogoten- VRIWZDUH SDFNDJH ,PDJH- 5DVEDQG 8VLQJ sis often uses diving to avoid predators as well as for this method, the cephalophorax (combined abdomen and temperature regulation (Brzostowicz et al. DQG KDV WKRUD[ RI WKH VSLGHU PHDVXUHG DERXW PP [ PP ZLWK been observed to stay underwater for considerable peri- a ~120mm legspan. ods (Höfer and Brescovit 2000; Brzostowicz and Greven From our photographs and description, Dr Hubert 7KH DELOLW\ WR PRYH RQ WKH ZDWHU VXUIDFH DQG WR Höfer of the State Museum of Natural History Karlsruhe remain submerged for extended periods seems to be aid- 601. LQ *HUPDQ\ LGHQWL¿HG WKH VSLGHU DV EHLQJ IURP HG E\ D FRDWLQJ RI ¿QH KDLUV WKDW WUDS DLU EXEEOHV DURXQG the family Ctenidae (tropical wolf spiders) of the genus its body. These hairs are also used to detect disturbances Ancylometes JLDQW ¿VKLQJ VSLGHUV DQG RI WKH VSHFLHV in the water and alert the spider to the presence of prey Ancylometes bogotensis .H\VHUOLQJ 7KH LQGLYLGXDO %U]RVWRZLF] DQG *UHYHQ here is a female; the male of this species has white stripes The prey in this case, R. hartii, and the other dominant RQ KLV DEGRPHQ $ ERG\ OHQJWK RI PP LV W\SLFDO IRU species in the habitat, P. reticulata, both belong to the an adult female A. bogotensis (Brzostowicz and Greven &\SULGRQWLIRUPHV ZKLFK DFFRXQW IRU RI DOO LGHQWL- ,W LV IRXQG IURP %ROLYLD WR 1LFDUDJXD DQG LV WKH ¿DEOH ¿VK VSHFLHV LQ VSLGHU SUHGDWLRQ UHSRUWV ZRUOGZLGH only species of this genus to be found in Trinidad (Höfer (Nyffeler and Pusey 2014). A. bogotensis appears to be a and Brescovit 2000). JHQHUDOLVW IHHGHU $V ZHOO DV ¿VK LW LV DOVR NQRZQ WR IHHG 57 58 Living World, J. Trinidad and Tobago Field Naturalists’ Club, 2015 as the pike cichlid Crenicichla frenata DQG WKH ZROI¿VK Hoplias malabaricus are absent. Owing to its ability to breathe cutaneously, R. hartii can evade immediate aquatic SUHGDWRUV E\ ÀLSSLQJ RXW WR ULSDULDQ KDELWDWV *LEE et al. 2011). This behaviour, however, may make them suscepti- ble to predation from semi-aquatic, edge-dwelling spiders. ,W ZRXOG EH RI JUHDW LQWHUHVW WR ¿QG RXW PRUH DERXW WKH distribution and abundance of A. bogotensis, and other ¿VKHDWLQJ VSLGHUV LQ 7ULQLGDG DQG WR EHWWHU XQGHUVWDQG the role they play as predators in aquatic habitats. It would be especially pertinent to address these questions within the Northern Range freshwater ecosystem, given the considerable existing knowledge on other taxa and habitat characteristics in this location. Fig. 1. A. bogotensis resting on the water with a freshly caught ACKNOWLEDGEMENTS NLOOL¿VK R. hartii. The authors are grateful to Dr Martin Nyffeler, Dr Anto- nio Brescovit and Dr Hubert Höfer for their helpful respons- es to our queries and for ultimately helping us to identify the species in question. We are also grateful to Dr Höfer and an anonymous reviewer for constructive comments on the manuscript. Dr Höfer’s website is an excellent resource IRU DQ\RQH ZDQWLQJ WR ¿QG RXW PRUH DERXW WKLV IDVFLQDW- ing group of spiders: http://www.wandering-spiders.net/ REFERENCES Bhukal, R., Rutherford, M.G. and Mohammed, R.S. 2015. Predation on a Freshwater Crab, Dilocarcinus dentatus by Sev- eral Tropical Wolf Spiders, Ancylometes bogotensis (Ctenidae) in Trinidad, W.I. Living World, Journal of The Trinidad and Tobago Field Naturalists’ Club, 2015: Brzostowicz, F. and Greven, H. %HREDFKWXQJHQ DQ GHU Fig. 2. A. bogotensis grasping its prey. Fischerspinne Ancylometes bogotensis .H\VHUOLQJ $UD- neae). Acta Biologica Benrodis on frogs and insects on the water surface (Brzostowicz and Croft, D.P., Morrell, L.J., Wade, A.S., Piyapong, C., Ioannou, *UHYHQ :KLWH et al. 2015) and, as described for the C.C., Dyer, J.R.G., Chapman, B.B., Wong, Y. and Krause, J. ¿UVW WLPH LQ WKLV LVVXH FUXVWDFHDQV %KXNDO et al. 2015). 2006. Predation Risk as a Driving Force for Sexual Segregation: ,Q JHQHUDO ¿VK SUHGDWLRQ E\ VSLGHUV WHQGV WR EH PRUH A Cross-Population Comparison. The American Naturalist, common in the tropics. On average, prey species tend to be WLPHV ORQJHU WKDQ WKH VSLGHU SUHGDWRU 2XU ¿VK ZDV Dugatkin, L.A. and Godin, J.G.J. 3UHGDWRU ,QVSHFWLRQ WLPHV ODUJHU WKDQ RXU VSLGHU ZKLFK LV ZHOO ZLWKLQ WKH Shoaling and Foraging under Predation Hazard in the Trini- rangeࢉ of previous observations (Nyffeler and Pusey 2014). dadian Guppy Poecilia reticulata. Environmental Biology of 7KH VWUHDPV DQG SRROV RI WKH$ULPD 9DOOH\ DUH H[WUHPH- Fishes, O\ ZHOO VWXGLHG LQ WHUPV RI ¿VK DQG SUHGDWLRQ LV RIWHQ D Fraser, D.F. and Lamphere, B.A. ([SHULPHQWDO HYDOXD- focus of these evolutionary ecology studies (e.g. Croft et tion of predation as a facilitator of invasion success in a stream al. 'XJDWNLQ DQG *RGLQ )UDVHU DQG /DPSKHUH ¿VK Ecology 7KLV HQFRXQWHU FRXSOHG ZLWK WKH IUHTXHQF\ DW ZKLFK Gibb, A.C., Ashley-Ross, M.A., Pace, C.M. and Long, J.H. similar spiders are seen poised by our pools, suggests 2011. Fish out of water: terrestrial jumping by fully aquatic that the role of arachnid predators may be underplayed in ¿VKHV Journal of Experimental Zoology Part A: Ecological the literature thus far, and may be an important source of Genetics and Physiology $ mortality and selection in these populations, especially Höfer, H. and Brescovit, A.D. 2000. A revision of the Neotrop- LQ SRROV DQG VWUHDPV ZKHUH WKH PDLQ ¿VK SUHGDWRUV VXFK ical spider genus Ancylometes Bertkau (Araneae: Pisauridae). Nature Notes 59 Insect Systematics and Evolution FKHFNOLVWBRIBVSLGHUVBLQBWULQLGDG KWP $FFHVVHG -XO\ Magurran, A.E. 2005. Evolutionary Ecology: The Trinidadian White, G. 2015. Observation of a spider, Ancylometes bogoten- Guppy. Oxford, Oxford University Press. sis (Ctenidae), preying on the frog Rhinella beebei (Bufonidae) Nyffeler, M. and Pusey, B.J.