Kornfield et al.: Cape lobster taxonomy 



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Telson with dorsal setae distributed in 3 longitu- 

 dinal tracts, central and submarginal on either side; 

 central tuft proximally in midline and another near 

 each anterolateral corner; sparse similar setae on 

 abdominal pleura; lateral ramus of uropod with ven- 

 tral submarginal row of setae laterally. 



Eyes with distal edge of cornea slightly exceeding 

 level of basicerite tip; this tip reaching to midlength 

 of narrowly rounded antennal scale exceeded by its 

 very strong anterolateral spine (rarely doubled) 

 reaching distal edge of penultimate article in anten- 

 nular peduncle; latter falling short of distal margin 

 of terminal article in antennal peduncle. 



Epistome with median anterior spine closely 

 flanked at either side by shorter rounded spine. 



Cheliped of pereopod 1 having fixed finger with 

 narrowed extensor margin set off by shallow submar- 

 ginal groove. Palm with compound row of low for- 

 ward pointing spines and tubercles on flexor surface, 

 similar development on extensor edge originating at 

 carpal condyle and running along proximal margin 

 of palm, across its basal end, and distally for a dis- 

 tance along palm. 



Oviducal opening on coxa of pereopod 3 oval; its 

 axes 1.3 x 1.8 mm on measured female noted below. 



Pleopod 1 with distal article broader than shaft 

 and hollowed mesially, forming flattened tubular 

 opening when appressed to opposite member, tip ir- 

 regularly rounded. Pleopod 2 with appendix 

 masculina on mesial aspect of endopod bearing tuft 

 of strong setae at apex. 



Uropods with protopodite bearing 2 strong spines 

 overhanging proximal end of mesial and lateral ra- 

 mus respectively. 



Variation — There is minor variation in development 

 of spines, tubercles, etc., among the two females and 

 two males examined. According to Stebbing (1900), 

 sides of the rostrum may have 5, 6, or 7 spines on 

 the margin. Density of setae on exoskeletal parts is 

 subject to considerable variation, owing perhaps to 

 recency of molting, age, or abrasion after preservation. 



Color — Color of a living animal is shown in Figure 1. 

 Published records summarized by Holthuis (1986) 

 indicate that color may depart considerably from that 

 shown here: coral-red to tawny or reddish yellow, 

 which may have resulted from postmortem changes; 

 or, in the fresh state, "of a rather dark olive colour, 

 not dissimilar to that of the Northern lobster" 

 Gilchrist (1918:45). 



Molecular characterization — Comparative analysis 

 of a portion of the 16s ribosomal RNA gene from 

 mitochondrial DNA (mtDNA) was conducted by 



using standard protocols (Kocher et al., 1989). Mito- 

 chondrial DNA's purified by CsCl ultracentrifugation 

 (Lansman et al., 1981) were amplified by PCR with 

 the conserved primers 16sar and 16sbr of Palumbi 

 et al. (1991). Following asymmetric amplification 

 (Homarus americanus and H. gammarus) or cycle- 

 sequencing (Homarinus capensis), DNA's were manu- 

 ally sequenced by the dideoxy chain-termination 

 method of Sanger et al. (1977). Aligned sequences 

 are presented in Figure 4. Sequence divergence be- 

 tween taxa was estimated by using the two-param- 

 eter method of Kimura (1980). Sequence divergence 

 between Homarus americanus and H. gammarus was 

 1.3%, whereas average divergence between these two 

 species and Homarinus capensis was 9.7%. The 16s 

 rRNA gene is one of the most slowly evolving regions 

 of the mtDNA molecule (Xiong and Kocher, 1994); 

 this conservative property makes it particularly use- 

 ful for comparative studies among distantly related 

 taxa. Though there is no formal recognition of equiva- 

 lence between levels of sequence divergence and taxo- 

 nomic rank (Hillis and Moritz, 1990), it is clear that 

 the relative magnitude of divergence can be a useful 

 taxonomic indicator (Avise, 1994). The magnitude of 

 sequence differentiation that we observed between 

 H. capensis and the two North Atlantic taxa strongly 

 suggested the existence of two discrete clades. Mo- 

 lecular divergence reinforced our conclusions from the 

 reexamination of the morphology of these species. 



Remarks — Morphological differences between 

 Homarinus capensis and the two species of Homarus 

 are clear cut. Perhaps the most obvious differences 

 are that Homarinus capensis has a dense coat of se- 

 tae on the outer surface of the palms and on other 

 articles of the chelipeds (PI), and scattered setae 

 distributed over the carapace, tail fan, sixth abdomi- 

 nal segment, and pleurae of the remaining abdomi- 

 nal segments; Homarus americanus and H. gam- 

 marus are smooth and glabrous. The telson of Ho- 

 marinus has subparallel sides and its exposed sur- 

 face bears many obsolescent transverse rugae (Fig. 

 3); the telson of Homarus species has sides converg- 

 ing toward the tip, giving a subtriangular shape. 

 First pleopods are more elongate and slender in 

 Homarus species than in Homarinus (Fig. 2). 



The two species of Homarus attain large size (Wolff, 

 1978), whereas Homarinus capensis appears to be 

 much smaller at maturity. No ovigerous females of 

 H. capensis have been found, but openings of the 

 oviducts are at least twice the size of those on com- 

 parably sized specimens of the species of Homarus 

 (see Kado et al., 1994). This suggests that there are 

 fewer eggs with accelerated larval development in 

 Homarinus capensis relative to slower larval devel- 



