FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 



Remarks on Synonymy and Variability 



Dana (1849, 1853, 1855) described the male 

 and female of P. plumata as separate species 

 based on specimens obtained from several 

 equatorial localities (in the Atlantic Ocean: 

 lat. 08°30'N to 00°, long. 23° to 18°W; 

 00°15'N, 31°00'W; 01°00' to 04°30'S, 17°30' 

 to 21°30'W; 04°30'S, 25°00'W). Our efforts to 

 use his descriptions and illustrations to sepa- 

 rate the two species in our Atlantic collections 

 were fruitless. Moreover, Dana's specimens of 

 Pontellina are apparently lost (T. E. Bowman, 

 in litt.). 



The present concept of P. plumata originates 

 from Giesbrecht's (1892) redescription and 

 synonymy which have been generally accepted. 

 Hence we regard his description of the species 

 as the basis for the type species of the genus. 



Several authors have noted morphological 

 variation in jo/« /»afo, observations that may indi- 

 cate that they had examined specimens of two 

 or more of the four species we recognize in the 

 genus. Thus, Dana (1853) reported that the 

 furcal rami were relatively longer in males 

 from the Cape of Good Hope region than in 

 males from the Pacific Ocean. Giesbrecht (1892) 

 found that the posterolateral corners of ThIV-V 

 were longer in males from the Pacific than in 

 those from waters off Naples. Tanaka (1964) 

 mentions differences in the posterolateral cor- 

 ners of ThIV-V in both sexes of plumata. Mori 

 (1937) believed the differences he encountered 

 in specimens of Pontelliua were a function of 

 ontogeny. On the other hand, a number of 

 authors have published illustrations which 

 appear to be based solely on plu))iata specimens 

 (e.g., Giesbrecht, 1892; Brodsky, 1962; Grice, 

 1962; Park, 1968). 



Distribution 



dance estimates ranged from 0.002 to 0.4 adults 

 per m-' water strained, the median being 0.02. In 

 the sets of samples selected for quantitative 

 analysis (Figure lb) the species appeared in- 

 frequently and in minimal numbers in the 

 eastern tropical Pacific. In the remainder of the 

 equatorial Pacific and in the Indian Ocean 

 plumata was found in about half of the samples 

 examined. 



Values of mean abundance in temporally 

 and geographically related sets of samples usual- 

 ly exceeded 0.02 per m-' of water strained (see 

 Figure 35, Table 14). With regard to the Atlan- 

 tic Ocean our impressions from the available 

 nonquantitative collections is that the abundance 

 of plumata is not appreciably different from 

 that in the Indian and Pacific Oceans. 



The widespread co-occurrence of three sibling 

 species (described below) imposes serious reser- 

 vations on the use of previously published 

 records of plumata. It would be best to consider 

 earlier records primarily as evidence of the 

 occurrence of the genus, a useful attribute con- 

 sidering the virtual absence of the genus at 

 latitudes above 40°. 



PONTELLINA PLATYCHELA SP.N. 



(Figures 6 and 7) 



Specimens seen: 168 adult females, 466 adult 

 males. 



Standard measurements: specimens randomly 

 selected from localities spanning the 

 observed geographical area of distribution. 



Total length (TL), mm: 



Standard 

 Mean error Speci- 



(x) Range 



Female 

 Male 



1.70 

 1.56 



error 



1.54-1.96 0.0173 

 1.41-1.74 0.0089 



mens 



30 



57 



Prosome-urosome length ratio (PUR): 



P. plujuata exhibits a warm-water circum- 

 global distribution bounded in the north and 

 south roughly by the subtropical convergence 

 zones of each hemisphere (Figure 5). Adults 

 were frequent in occurrence but relatively low 

 in abundance. For example, in 131 zooplankton 

 samples containing the species from the Indian 

 and Pacific Oceans (Indian Ocean Standard Net 

 and CalCOFI Standard Net zooplankton sam- 

 ples; tows through the epipelagic layer) abun- 



Female 



Posterolateral corner of ThIV-V ending in a 

 relatively minute dentiform process extending 

 posteriad or weakly medioposteriad (Figure 



75 



