Siphonaria carbo Hanley, 1858

Jenkins, Bruce & Köhler, Frank, 2024, Hidden in plain sight: Systematic review of Indo-West Pacific Siphonariidae uncovers extensive cryptic diversity based on comparative morphology and mitochondrial phylogenetics (Mollusca, Gastropoda), Megataxa 13 (1), pp. 1-217 : 98-100

Siphonaria carbo Hanley, 1858

( Figs 38A–E , 39A–B )

Siphonaria carbo Hanley 1858a: 24 (type locality unknown).— Hanley 1858b: 151; Paetel 1889: 428; Kilburn & Rippey 1982: 134; Chambers & McQuaid 1994a: 264; Bosch et al. 1995: fig. 860; Coan & Kabat 2012: 336; White & Dayrat 2012: 61.

Siphonaria nigerrima Smith 1903: 356, pl. 15, figs 4, 5 (type locality: Umhlali, Natal (Burnup) [ South Africa]).—Hubendick 1947: 162, fig. 2; Trew 1983: 3; Chambers & McQuaid 1994a: 265, fig. 1M; Teske et al. 2007: 223, 225, fig. 2; 2011: 5026; White & Dayrat 2012: 66.

Siphonaria tenuicostulata Smith 1903: 356, pl. 15, figs 14, 15 (type locality: Umhlali, Natal (Burnup) [ South Africa]).— Hubendick 1947: 161, fig. 1; Kilburn & Rippey 1982: 134; Allanson 1958: 166; Trew 1983: 4; Chambers & McQuaid 1994a: 265, fig. 1N; Teske et al. 2007: 223, 225, fig. 2; 2011: 5028, White & Dayrat 2012: 68.

Siphonaria anneae Tomlin1944:92–93 (type locality Umpangazilali [ South Africa]).— Allanson 1963: 70; Chambers & McQuaid 1994a: 265, fig. 1H, I, 3C; Teske et al. 2007: 223, 225, fig. 2; 2011: 5028, White & Dayrat 2012: 61.

Siphonaria (Patellopsis) nigerrima — Hubendick 1945: 70; Chambers & McQuaid 1994b: 418; Chambers et al. 1996: 3; 1998: 51.

Siphonaria (Patellopsis) tenuicostulata — Hubendick 1945: 70; 1946: 35, pl. 6, figs 18–19; Chambers & McQuaid 1994b: 418; Chambers et al. 1996: 3; 1998: 51.

Siphonaria (Patellopsis) carbo — Hubendick 1946: 35, pl. 6, figs 16–17; Allanson 1958: 150, 167, 170, fig. 14.

Siphonaria (Patellopsis) dayi Allanson 1958: 169 , pl. 1b, 2b, figs 5, 16 (type locality: Inhaca Island, Delagoa Bay [ South Africa]).— Chambers & McQuaid 1994a: 265, fig. 1L; 1994b: 418; Chambers et al. 1996: 3; 1998: 51.

Siphonaria (Patellopsis) anneae — Allanson 1958: 150, 166, pl. 1b, 2b, fig. 3, 13; Chambers & McQuaid 1994b: 418; Chambers et al. 1996: 3; 1998: 51.

Siphonaria dayi — Teske et al. 2007: 223, 225, fig. 2; 2011: 5028, White & Dayrat 2012: 62.

Material examined. Type material. Holotype of Siphonaria carbo Hanley, 1858 ; coll. Cuming ( NHMUK 1981009 , Fig. 38A ).

Lectotype of Siphonaria nigerrima Smith, 1903, present designation, from Umhlali , KwaZulu-Natal, South Africa; donated J H. Ponsonby ( NHMUK 1903.9.9.15 , Fig. 38B ). Two paralectotypes, same data as lectotype ( NHMUK 1903.9.9.16–17 ).

Eight syntypes of Siphonaria tenuicostulata Smith, 1903 from Umhlali , KwaZulu-Natal, South Africa; donated J H. Ponsonby ( NHMUK 1903.9.9.7 ( Fig. 38C , largest syntype)–14) .

Other, non-type material. Mozambique: Inhaca , Ponta do Farol, 25°58.2’S, 32°59.4’E MM6 ( MNHN IM-2019-1489 29p, MNHN IM-2019-16164 p [M586], MNHN IM-2019-16165 p [M587]) .

Taxonomic remarks. Hubendick (1946: 35) treated S. nigerrima as a synonym of S. carbo Hanley, 1858 . Which was confirmed later in the taxonomic revision of Teske et al. (2007) based on comparative morphology and mitochondrial phylogenetics. They added the species S. anneae and S. tenuicostulata to the synonymy of this species, which is also accepted herein. The largest syntype of S. nigerrima is herein designated as the lectotype ( Fig. 38B ) for the stabilisation of the name (Art. 74.1 of the Code). This type specimens matches the typical characteristics of S. carbo ( Fig. 38A ) in size, shape, height, colour ( Fig. 38B ). Our analysis of topotypical specimens of S. nigerrima confirms its status as a synonym of S. carbo . Previously, Chambers & McQuaid (1994a: 264) incorrectly stated that S. carbo was described from the Caribbean and ‘does not occur on South African shores’. This observation is not accepted herein. Based on examinations of topotypic samples matching the morphological characteristics of S. dayi ( Fig. 38D, E ), this taxon is also placed in the synonymy of S. carbo .

External morphology (preserved). Foot sole grey, paler to foot edge; mantle translucent, pigmentation absent on foot wall, mantle edge, pneumostome; faint pigmentation over centre of cephalic folds.

Shell ( Figs 38A–E ; Table S9). Small to medium sized (max sl mean = 12.5 mm, SD = 6.0 mm, n = 5), circular ovate, height tall; apex offset central, apical sides convex, protoconch direction weakly homostrophic to central (n = 1), shell whorl dextral; exterior dark metallic brown/grey, often pale brown; primary ribs with 0–2 finer in between secondary ribs, interstices similar colour, growth striae prominent; radial colour bands distinct, darker at apex and shell margin; rib count (mean = 48, SD = 7.8, n = 5), majority primary ribs, ridges weakly raised, rounded; siphonal ridge indistinct, formed by paired primary ribs, primary ribs broaden weakly, project weakly beyond shell lip (especially siphonal ridge) to scallop and corrugate shell edge. Interior of shell evenly dark brown to grey ( Fig. 38A–B ), may also display off-white rays on shell margin align under primary/secondary ribs, extending to spatula ( Fig 38C ); siphonal groove distinct, shallow, often paler than margin; ADM scar clear, similar to margin and spatula; CMS convex; whitening and thickening of shell lip not observed.

Reproductive system ( Fig. 39A; n = 1). Positioned within coelom under the respiratory cavity, hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts between RAM and extending over BM; GA large, AO indistinct and appears part of GA, singular prominent GP, ED short, centrally bent; ED enters at upper end of GA, AO, GA and ED all muscular white tissue; EG very large, elongated, folded, soft white tissue; single thick elongated blunt flagellum F1 appears as extension of ED at EG join; BD and CD connect closely together into GA close to ED junction, both ducts smooth, featureless, wide, slightly bent, pass together between inner foot wall and outer side of RAM ( BD over CD) connecting into MG / AG; BC large, bulbous, white opaque test, embedded along with part of BD in soft white folds of MG; HD short, wide, unpigmented, heavily lobed, links soft white folded AG to smaller yellowish granular HG; SV embedded in AG close to BC.

Spermatophore ( Fig. 39B ). Broad head with short flagellum (length = 1.29 mm, n = 1); head section bulbous but flattened, test thin, smooth, featureless; tapering section merges head to flagellum; head longer, wider than flagellum (head length = 0.77 mm, n = 1; flagellum length; 0.53 mm, ~ 59% of SMP length; head width = 362 μm, flagellum width = 149 μm); 2 SPMs held in cream gelatinous mass in BC of one specimen [M587].

Radula. Dentition formula 36:1:36 (Hubendick 1947: 162 as ‘ S. nigerrima’), 36:1:36 ( Hubendick 1946: 35 as ‘ S. carbo ’) and 40:1:40 ( Hubendick 1946: 35, 1947: 162 as ‘ S. tenuicostulata ’).

Comparative remarks. Collectively, the works of Allanson (1958), Chambers & McQuaid, (1994a: 264) and Teske et al. (2007, 2011: 5025) clarified the taxonomy of South African Siphonaria species, which is followed herein except that S. dayi is treated as a junior synonym of S. carbo . Our study does not include analyses of the South African species S. concinna , S. oculus and S. serrata ; refer to Teske et al. (2007, 2011) for comparisons. We found that S. carbo ( pectinata group, unit 94) is the sister species of S. itampoloensis sp. nov. in our phylogenetic tree ( Figs 1 , 4 ). Both species together form the sister lineage of S. asghar . Siphonaria carbo differs from S. itampoloensis by COI distances of ≥ 5.1% and from S. asghar by distances of ≥ 11.1% (Table S8). Siphonaria carbo differs from S. itampoloensis by having a darker, lower shell with finer ribbing, a wider BD, larger EG, and a larger, elongate BC. Siphonaria carbo has been found in sympatry with two congeners in Mozambique. For comparisons with S. capensis and S. plana refer to comparative remarks under these species. The shape of the SPM of S. carbo closely resembles that of other species, such as S. funiculata , S. zelandica , S. acmaeoides , S. lateralis , and S. tasmanica . However, Siphonaria carbo has a smaller ED / EG and broader CD /BD’s than these species. The RS of ‘ S. tenuicostulata’ (= S. carbo ) figured in Hubendick (1945: 21, fig. 22) corresponds well with the typical anatomy of this species except for details of the CD / BD / GP / GA junction, which Hubendick (1946: fig. 20) showed to be wider and with the ducts more separated. Hubendick (1947: 161) considered the RS of ‘ S. tenuicostulata ’ (fig. 1) and ‘ S. nigerrima ’ (fig. 2, epiphallic parts absent), from Umhlali Natal, to be a ‘closely related’ species ‘only showing differences in small details’. Hubendick (1947) figured a RS matching that of S. carbo shown here ( Fig. 39A ) more closely than any other species. Allanson (1958: 167) stated that the distal genitalia of S. anneae were ‘Exactly similar to S. teniucostulata ’ referring to ‘ S. tenuicostulata ’ from Oman figured in Bosch (1982: 141; 1991: 75). However, these figures are incorrectly assigned to S. tenuicostulata (= S. carbo ) because this location is well outside the known distribution of this species.

Distribution and habitat. Recorded from tropical and subtropical coasts of southeastern Africa ( Fig. 25 ). Found on exposed rocky shores across mid to upper littoral levels.

Figures

FIGURE 1. Maximum Likelihood phylogram based on analyses of a concatenated sequence data set of 16S and COI. Branches are collapsed at the species level. Branch labels give unit numbers and accepted species names. Numbers on branches indicate branch support employing 10,000 ultrafast bootstraps.Available genus-group names are shown next to their type species. Scale bar indicating modelled sequence divergence.

FIGURE 4. Maximum Likelihood phylogram (partial, species not collapsed). Clades C–F (normalis, lateralis and pectinata groups) of the tree shown in Fig. 1. Branch labels give specimen identifiers for new sequences or Genbank accession numbers for imported sequences from other studies and geographic regions (see Tables S1–S2 for details). Identical haplotypes are merged into single tips. Numbers on branches indicate branch support by employing 10,000 ultrafast bootstraps. Clade names give unit numbers and accepted species names. Scale bar indicating modelled sequence divergence.

FIGURE 25. Known occurrence records of S. viridis, S. normalis, S. radians, S. scabra, S. funiculata, S. kurracheensis and S. carbo.

FIGURE 38. Shells of S. carbo and S. exulum. A–E. S. carbo. A. Holotype NHMUK 1981009. B. Lectotype of S. nigerrima NHMUK 1903.9.9.15. C. Largest syntype of S. tenuicostulata NHMUK 1903.9.9.7. D–E. Mozambique, Inhaca. D. IM 2019- 16165 [M587]. E. MNHN IM 2019-16164 [M586]. F–T. S. exulum, F. Holotype NHMUK 1900.3.19.27. G. NI, TS, AM C.585026 [M220]. H. NI, TS, AM C.585025 [SK041]. I. Holotype of S. raoulensis CM M.3666. J. Holotype of S. cheesemani CM M.3660. K. Holotype of S. macauleyensis CM M.3663. L. Holotype of S. macauleyensis perplexa CM M.3661. M. Holotype of S. amphibia CM M.3665. N. Syntype of Parellsiphon innocuus AM C.103708. O. Kermadec Is, Raoul Is, TS, AM C.475847 [M513]. P. Kermadec Is, South Meyer Is, TS, AM C.475848 [M512]. Q. NI, TS of S. innocuus AM C.585020 [M217]. R. Protoconch, AM C.585029 [SK010]. S. NI, animal. T. NI, in situ. Unlabelled scale bars = 10 mm.

FIGURE 39. Reproductive morphology of S. carbo, S. belcheri, S. exulum and S. nuttallii. A–B. S. carbo, Mozambique, MNHN IM 2019-16165 [M587]. C–D. S. belcheri, Pakistan, Karachi. C. AM C.585500 [SK146]. D. AM C.595930 [SK533]. E–H. S. exulum. E. NI, TS, AM C.585025 [SK041]. F. LHI, AM C.546717 [SK052]. G–H. Kermadec Is, Raoul Is, TS of S. raoulensis. G. AM C.475847 [M513]. H. AM C.475848 [M512]. I–J. S. nuttallii, Hawaii, Maui, TS. I. AM C.584898 [SK211]. J. AM C.584895 [M471, SK273]. Unlabelled scale bars = 1 mm.