BASAL LAOPHONTID EVOLUTION 



105 



found in salt-marsh and mudflat habitats within river estuaries 

 (Noodt, 1957; Barnett, 1968; Bodin, 1976) or in brackish lagoons 

 (Heip, 1969; Hamond, 1972), tolerance to oligohalinity may have 

 appeared convergently only twice in the family. Both colonization 

 events presumably occurred early in the evolution of the family (Fig. 

 32), however their nature is fundamentally different. The evolution- 

 ary success of the Troglophonte lineage has clearly remained limited, 

 both in dispersal and speciation. It can be considered as a freshwater 

 incursion without further radiation or diversification. The second 

 invasion of low salinity environments is cosmopolitan in scope and 

 probably of Tethyan origin, containing the genera Onychocamptus 

 Daday and Folioquinpes Fiers & Rutledge (Lee & Huys, 1999). 



Little is known about the possible dispersal of Laophontidae in 

 marine caves. Pesta (1959) reported E. rosei from a submarine cave 

 near Naples and several unidentified Laophontidae were recorded 

 by Huys (1996) from the anchialine Walsingham Cave on Bermuda. 

 Examination of samples from Caye Chapel Cave in Belize, the type 

 locality of the recently discovered family Novocriniidae (Huys & 

 Iliffe, 1998), resulted in the discovery of a single male belonging to 

 a new genus of Esolinae. The new genus has several characters in 

 common with Archilaophonte such as the presence of a spinous 

 process on the second antennulary segment, the displacement of the 

 outermost endopodal seta on the maxillule, the presence of 3 setae 

 on the maxillipedal syncoxa, PI with 2-segmented exopod and 

 elongate enp-2, P2 enp-2 with only 1 inner seta and presence of a 

 very long apophysis on P3 endopod. Phylogenetic analysis identi- 

 fied the Belize genus unambiguously as the sistergroup of 

 Archilaophonte, suggesting the evolution of an independent 

 cavernicolous lineage in the western Atlantic. 



The genus Archesola is exclusively boreo-arctic in distribution 

 and restricted to the Atlantic basin, with a single known outlier from 

 the Black Sea (Por, 1959). Its southernmost limit based on reliable 

 records is Norfolk (England), however, confirmation of the doubtful 

 records of A. longiremis from the south coast of England (Wells. 

 1961, 1963, 1970) and North Carolina (Coull, 1971) may extend this 

 limit further southward. The genus occurs primarily at higher lati- 

 tudes, showing limited dispersal in Arctic waters such as the White 

 Sea (Brotskaya, 1961; Chislenko, 1967). It is suggested that the 

 strongly discontinuous, bipolar distribution of the two basal clades, 

 with Archesola restricted to northern Europe and Archilaophonte to 

 the Antarctic, indicates a wider, perhaps continuous, horizontal 

 zonation of primitive stenothermal esolinids at greater depths. This 

 trend of 'Equatorial Submergence' appears to be supported by the 

 discovery of Bathyesola in the deep tropical western Pacific, the first 

 lineage to diverge after Archesola (Fig. 32). 



A major event in the evolution of the Esolinae was the episode of 

 rapid speciation within the genus Esola. This event is revealed as a 

 polychotomy in the cladogram (Fig. 32) although it is clear that the 

 low resolution is partly attributable to the abundance of missing 

 entries for several taxa which are known from one sex only (Table 

 3). Many of these species are small-sized (Table 1 ) and adapted to a 

 mesopsammic life-style in shallow subtidal localities and sandy 

 beaches, while others are frequently found associated with algal 

 substrates. Results show that only a fraction of the species is known. 

 Although the genus assumes a cosmopolitan distribution it is pre- 

 dominantly restricted to the circum-tropical belt. This zone coincides 

 with the former Tethyan seaway separating the northern and south- 

 ern continents, which continued into Palaeogene times with free 

 marine continuity along its length not being interrupted until the 

 beginning of the Neogene. One Pacific-Caribbean subgroup, com- 

 prising E. longicauda, E. galapagoensis and Esola sp. (Fig. 32), 

 probably originated from an ancestral stock in the western Pacific. 

 From there, eastward dispersal was greatly influenced by tectonic 



plate movement, particularly the formation of the Caribbean plate at 

 the beginning of the Oligocene. This was established by decoupling 

 of the eastward protruding tongue of the East Pacific plate, causing 

 the formation of a subduction zone along what is now the western 

 coast of southern Central America, and the subsequent westward 

 motion of North and South America past a nearly stationary Carib- 

 bean plate (Malfait & Dinkelman, 1972; Coney, 1982). The entry of 

 the ancestor of E. longicauda into the Caribbean must have preceded 

 the closing of the Panama land bridge approximately 3.1-3.5 Ma 

 (Keigwin, 1978). 



Applanola displays a more disjunct distribution than its sistergroup 

 Esola, provided that Pesta's (1916) record from the Gulf of Guinea 

 is correct. The dorsoventrally depressed body, robust maxillipeds 

 and powerful PI endopod indicate that A. hirsuta may be loosely 

 associated with invertebrate hosts. Thompson & A. Scott (1903) 

 obtained the species from washings of pearl oysters and other 

 dredged invertebrates but did not present any firm evidence for a 

 clear association. 



ACKNOWLEDGEMENTS. Dr Danielle Defaye (Museum National d'Histoire 

 Naturelle. Paris), Dr Chad T. Walter (National Museum of Natural History, 

 Washington D.C. ), Karen Gowlett-Holmes (South Australian Museum) and Dr 

 Mark Holmes (National Museum of Ireland) kindly made type and other 

 material available. Dr Richard Hamond (Norfolk, U.K.) provided us with 

 specimens of E. bulbifera and A. typhlops. The material of Bathyesola 

 compacta was collected during the STARMER II expedition to the Fiji Basin 

 (chief scientist: L. Laubier). One of us (W.L.) acknowledges financial support 

 from the Korea Research Foundation provided for the programme year 1 997. 



REFERENCES 



Alheit, J. & Scheibel, W. 1 982. Benthic harpacticoids as a food source for fish. Marine 



Biology, Berlin 70(2): 141-147. 

 Barnett, P.R.0. 1 968. Distribution and ecology of harpaetieoid copepods of an intertidal 



mudflat. Internationale Revue der gesammten Hydrobiologie 53: 177-209. 

 Bodin, P. 1976. Les Copepodes Harpactico't'des (Crustacea) des cotes Charentaises 



(Atlantique). Donne'es ecologiques et biologiques sur les especes principales. Bulle- 

 tin du Museum national d'Histoire naturelle. Paris (3)353 (= Ecologie generate 29): 



1^15. 

 . 1997. Catalogue of the new marine harpaetieoid copepods. Studiedocumenten 



van het K.B.I.N, 89: 1-304. 

 Brian, A. 1928a. Descrizione di specie nuove o poco conosciute di Copepodi bentonici 



del mare Egeo. (Nota preliminare). Bollettino dei Musei di Zoologia e Anatomia 



comparata delta R. Universitd di Genova (2)7( 18): 1-37. 



. 1928b. I Copepodi bentonici marini. Archivio zoologico italiano 12: 293-343. 



Brotskaya, V.A. 1961. Materialy po faune Harpacticoida (Crustacea, Copepoda) 



Velikoi salmy i prilezheshchikh uchastkov Belogo morya. Contributions to the fauna 



of Harpacticoidea (Crustacea: Copepoda) of the Velikaya Salma Strait and of 



adjacent region of the White Sea. Biologiya Belogo Morya (= Trudy belomorskoi 



biologicheskoi Stantsii. M.G.U.) 1: 109-129. 

 Chappuis, P.A. 1938. Subterrane Harpacticoiden aus Sud-Italien. Bullelinul Societdjii 



de $tiinfe din Cluj 9: 1 53- 1 8 1 . 

 Chislenko, L.L. 1967. Garpaktitsidy (Copepoda Harpacticoida) Karelskogo 



poberezh'ya Belogo morya. [Copepoda Harpacticoida of the Karelian coast of the 



White Sea. Issledovaniya Fauny Morei 7(15): 48-196. 

 Coney, P.J. 1982. Plate tectonic constraints on the biogeography of Middle America 



and the Caribbean region. Annals of the Missouri Botanical Garden 69: 432-443. 

 Coull, B.C. 1971. Meiobenthic Harpacticoida (Crustacea, Copepoda) from the North 



Carolina continental shelf. Cahiers de Biologie marine 12(2): 195-237. 

 Douwe, C. van 1 929. Marine Litoral-Copepoden: Zur Verbreitung des Genus Laophonte 



Philippi im Mittelmeer. Zoologischer Anzeiger 83(1 1-12): 283-294. 

 Drzycimski, I. 1969. Harpacticoida (Copepoda) wod morskich okolic Bergen 



(Zachodnie Wybrzeze Norwegii) i ich ekologia. Harpacticoida (Copepoda) of sea 



waters in Bergen region (West Coast of Norway) and their ecology. (Polish with 



English and Russian summaries). Wyzsza Szkola Rolnicza w Szczecinie 17: 1-72. 

 Edwards, C.L. 1891. Beschreibung einiger neuen Copepoden und eines neuen 



copepodenahnlichen Krebses, Leuckartella paradoxa. Archiv fiir Naturgeschichte 



57: 75-104. 



