BASAL LAOPHONTID EVOLUTION 



51 



holothurian Actinopyga agassizii (Selenka) [as Miilleria Agassizii], 

 he considered it to be essentially free-living. He noted the distinctly 

 hirsute appearance and recognized a similarity between Esola and 

 Cleta Claus, placing the genus in the 'Harpactiden'. Monard (1927) 

 placed the genus in the Laophontidae but erroneously stated in the 

 generic key that the antennule is 5-segmented. Later he professed 

 that Esola was really a 'hirsute Laophonte', differing from its 

 congeners only by the 1 -segmented PI exopod and its commensal 

 lifestyle with holothurians (Monard, 1935). Nicholls (1941ft) also 

 regarded the genus as a 'derivative' of Laophonte, however main- 

 tained the generic name pending a redescription of the type species. 



The genus remained monotypic until Lang's (1944, 1948) revi- 

 sion of the Laophontidae which added 8 Laophonte species to the 

 genus: L. hirsuta Thompson & A. Scott, L. longiremis T. Scott, L. 

 typhlops Sars, L. bulligera Farran, L. rosei Monard, L. spelaea 

 Chappuis, L. bulbifera Norman, and L. rhodiaca Brian. Lang ( 1 948) 

 regarded the latter two species as synonyms of E. longicauda. He 

 maintained E. longicauda, E. bulligera and E. rosei as distinct 

 species for convenience rather than conviction, believing that future 

 examination might well show all three to be mere forms of the same 

 species. Lang ( 1 944) divided the genus into two groups, the spelaea- 

 group, including only E. spelaea, and the longicauda-group, 

 accommodating all other species. 



Nicholls (1941ft) had adopted a more artificial approach in his 

 revision of the Laophontidae, subdividing the genus Laophonte 

 Philippi into five subgenera on the basis of the endopodal setation of 

 the P3, and to a lesser extent also that of P2 and P4. He referred L. 

 rosei, L. bulligera, L. bulbifera, L. typhlops and L. longiremis to the 

 nominate subgenus Laophonte, more specifically to the typhlops- 

 group which also included L. elongata Boeck, L. thoracica Boeck 

 and L. barbata Lang. In the subgenus Mesolaophonte Nicholls he 

 placed L. spelaea which he believed to occupy an isolated position 

 due to the presence of 5 setae on the distal endopod segment of P4. 

 Finally, he regarded both L. hirsuta and L. rhodiaca as species 

 inquirendae, the former because it was inadequately described, the 

 latter because it was only known from the male. This system was 

 heavily criticized by Lang (1948: 1620-1621) in a postscript to his 

 monograph. A similar unnatural division of the genus Laophonte 

 had also been proposed by Sewell ( 1 940), using P 1 exopod segmen- 

 tation as the primary divisive character. 



With the exception of Vervoort (1964) most authors have 

 uncritically accepted Lang's (1948) decision to consider E. 

 longicauda as a variable and cosmopolitan species. Wells & Rao 

 (1987) regard the species as 'highly distinctive pan-temperate/ 

 tropical' and express severe doubts about Mielke's (1981) justifica- 

 tion for establishing E. longicauda galapagoensis. Mielke (1997) 

 hinted at the possibility off. longicauda being a complex of several 

 closely related species and our examination appears to substantiate 

 his conjecture. In this revision we have restricted the genus Esola to 

 E. longicauda and to those species which have mistakenly been 

 synonymized with the type or were incorrectly described under that 

 name. The major diagnostic characters of these species are tabulated 

 in Table 1. Only E. bulbifera will be described in detail below; the 

 descriptions of the other species will be largely confined to the 

 differences with this species. 



Diagnosis. Laophontidae. Body cylindrical; posterolateral cor- 

 ners of 9 genital double-somite and second abdominal somite 

 laterally and backwardly produced. Integument of cephalothorax 

 and body somites with dense pattern of spinules and setules. Ros- 

 trum large, partly delimited at base. Four pairs of integumental 

 cup-shaped pores present: anterodorsally on cephalothorax, near 

 ventrolateral margins of cephalic shield, laterally on genital (6) or 



genital double-somite ( 9) and ventrally on caudal rami. Anal oper- 

 culum spinulose. Caudal rami modified in 9, often forming bulbous 

 expansions dorsally, ventrally and medially; rectangular and longer 

 than wide in 6. 



Sexual dimorphism in body shape, antennule, P3 endopod, P5, 

 P6, genital segmentation and caudal rami. 



Antennules slender; 6- or incompletely 7-segmented in 9, 

 subchirocer and 7-segmented in 3; segment 1 with 2-3 spinous 

 processes along posterior margin; with aesthetasc on segment 4 ( 9) 

 or 5 (8) and as part of apical acrothek on distal segment; segment 5 

 6 swollen, bearing modified spine on anterior outgrowth; proximal 

 aesthetasc fused to 2 setae. Antenna with 4 setae on exopod; 

 allobasis with abexopodal seta. Labrum with overlapping scales 

 distally and dense pattern of spinules proximally. Mandible with 

 short 1- or 2-segmented palp; endopod free or incorporated, repres- 

 ented by 2-3 setae; exopod usually absent, sometimes represented 

 by single seta; basis represented by 1-2 setae. Maxillule with 

 minute, defined exopod. Maxilla with 3 endites on syncoxa; endopod 

 represented by 4 setae. Maxilliped slender; syncoxa with 2 setae; 

 entire palmar margin with spinules; endopodal claw elongate. 



PI with 2-segmented exopod bearing 4-5 setae on exp-2 and 

 elongate endopod; enp-1 without inner seta, enp-2 with minute seta 

 and long, slender claw. P2-P4 with 3-segmented exopods and 2- 

 segmented endopods. P2 basis with very long outer spine. Outer 

 spine of P2-P4 enp-2 very long and setiform. P3 endopod 6 3- 

 segmented; enp-2 with inner seta and outer, dentate or smooth, 

 spinous apophysis. Armature formula as follows: 



Exopod 



Endopod 



P2 

 P3 

 P4 



0. 1 . 1 23 

 0.1.223 

 0.1.223 



[0-l].221 

 [0-l].321 

 [0-l].221 



[(J: [0-1]. 1.220] 



P5 9 with separate rami; exopod elongate, with 6 setae/spines; 

 baseoendopod slightly developed, with 4 setae/spines. P5 6 without 

 endopodal lobe; exopod short, with 1 inner, 2 apical and 2 outer 

 elements. 



P6 9 forming opercula closing off paired genital apertures; with 

 one seta and 2 small processes at outer corner. P6 6 asymmetrical; 

 membranous flaps with 2 setae. 



TYPE SPECIES. Esola longicauda Edwards, 1891 [by monotypy]. 



OTHER SPECIES. Esola bulbifera (Norman, 1 9 1 1 ); E. galapagoensis 

 Mielke, 1981 grad. nov.; E. profunda sp. nov.; E. canalis sp. nov.; E. 

 lobata sp. nov., E. vervoorti sp. nov. 



Species inquirendae. E. longicauda Edwards, 1 89 1 sensu Noodt 

 (1955);£. longicauda Edwards, 1891 var.sensu Vervoort (1964); E. 

 longicauda Edwards, 1891 sensu Wells & Rao (1986); Esola spec. 

 sensu Mielke (1997). 



Esola longicauda Edwards, 1891 



TYPE LOCALITY. Unspecified shallow water locality in Bahamas. 



TYPE material. Edwards (1891) found both sexes but the material 

 is presumably lost. 



Lang (1948) pointed out Edwards' observational errors in his de- 

 scription of the PI such as the presence of 4 setae on the inner margin 

 of the proximal endopod segment and the 1 -segmented exopod. 

 Using the insertion site of the endopod as a reference point Lang 

 inferred that Edwards had incorporated the proximal exopod seg- 

 ment into the basis and that the outer basal seta is in reality exopodal. 



