Fig. 1
Positions of 14 homologous landmarks of the head used in geometric morphometric analyses. Photo of Sternarchella orthos (FMNH 115236). Scale bar = 15 mm.
Fig. 2
Illustrations of neurocrania in lateral view of species in the Sternarchella calhamazon clade. a.
Sternarchella patriciae (MUSM 45234) showing the ‘crown of thorns’ at the border of the parietal and supraoccipital bones. b.
Fig. 3
Dorsal view of the brachial basket in four species of Sternarchella.
a.
Sternarchella patriciae (MUSM 45234). b.
Sternarchella orinoco (USNM 228727). c.
Sternarchella schotti (UF 116570). d.
Sternarchella orthos (USNM 228871).
Fig. 4
Radiographs of holotypes of two Sternarchella species showing condition of displaced hemal spines at posterior margin of body cavity. a.
Sternarchella terminalis holotype (CAS 54912). b.
Sternarchus schotti holotype (NMW 65335).
Fig. 5
Phylogenetic tree of
Sternarchella resulting from a maximum parsimony analysis of the 76 morphological characters in Appendix 1 (
S1). Bremer supports shown to the left of nodes. Clades labeled by letters and names as in text and
Tab. 1.
Fig. 6
Radiographs of six of the nine valid Sternarchella species.
a.
S. orthos (USNM 228871).
b.
S. schotti (NMW 65335, holotype).
c.
S. sima (AMNH 3864, holotype).
d.
S. orinoco (USNM 228727). e.
S. calhamazon (INPA 37898, holotype).
f.
S. patriciae (MUSM 45239, holotype).
Fig. 7
Sternarchella patriciae holotype (MUSM 45239). a. Lateral view of the body, b. Head and anterior portion of body, c. Caudal region showing two rows of intermuscular bones (Myb), the anal-fin base (AFB) and the continuous caudal peduncle membrane (CPM).
Fig. 8
Map of collection localities of species in the S. calhamazon species group. Sternarchella rex (triangles), S. patriciae (stars), and S. calhamazon (circles). Note: 1, the S. calhamazon species group is restricted to the Amazon basin; 2, the allopatric distribution of the sister species S. calhamazon and S. patriciae; and 3, S. calhamazon is represented at more sites than other members of the S. calhamazon species group. Base map of drainages provided by Conservation Science Program, World Wildlife Fund US; inset depicts elevations in gray shades.
Fig. 9
Type locality of Sternarchella patriciae on the Río Madre de Dios, in front of Puerto Maldonado (Tambopata Department) near the confluence of the Tambopata River. Specimens were collected at about 10 m depth using a 12 foot shrimp trawl.
Fig. 10
Biplot of length to end of anal-fin (LEA) vs. caudal peduncle depth (CPD) for eight species of Sternarchella showing the separation between S. calhamazon from white water, S. calhamazon from black water (BW), and seven other Sternarchella species in CPD.
Fig. 11
Sternarchella rex (ANSP 200294). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region. Scale bars = 1.5 cm.
Fig. 12
Photographs heads of live specimens of four syntopic species of Sternarchella from the vicinity of Tefé, Amazonas, Brazil. a.
Sternarchella rex holotype (MCP 49422). b.
Sternarchella schotti (MCP 49429. c.
Sternarchella calhamazon (MCP 49420. d.
Sternarchella orthos (MCP 49436). Scale bar = 10 mm. The flanks of this fish were considerably paler moments before this photograph was taken.
Fig. 13
Amazon River margin habitat near type locality of Sternarchella rex in Tefé, Brazil. Specimens were collected using 50 x 6 m or 50 x 8 m beach seine nets operated in the mid-channel and edges of whitewater floodplain channels of the río Solimões-Japurá confluence, and on beaches of the río Japurá near its confluence with the río Solimões (Amazon).
Fig. 14
Head-to-tail electric organ discharge (ht-EOD) waveforms (left) of Sternarchella rex, with corresponding power spectral density (PSD) computed by 65536-point Fast Fourier Transform from a 3s digital recording (right).
Fig. 15
Sternarchella calhamazon (USNM 373113). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region showing two rows of intermuscular bones in the caudal peduncle and the continuous caudal peduncle membrane. Scale bars = 1 cm.
Fig. 16
Sternarchella duccis (ANSP 200514). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region. Scale bars = 1 cm.
Fig. 17
Map of collection localities of S. orthos (triangles), S. schotti (circles), and S. duccis (stars). Note these three species are broadly sympatric throughout the Eastern and Western Amazon, with S. orthos also present in the upper Madeira and Lower Orinoco, and S. schotti known from a single specimen in the Meta River, Orinoco basin. Note also, S. orthos is represented at more sites than S. schotti.
Fig. 18
Sternarchella orinoco (USNM 228727). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region showing a single row of intermuscular bones in the caudal peduncle and the discontinuous caudal peduncle membrane. Scale bars = 1 cm.
Fig. 19
Map of collection localities for specimens in the S. sima group. Sternarchella sima (circles), S. orinoco (stars), and S. raptor (triangles). Note most specimens of the S. sima group have been collected near the mouths of the Amazon and Orinoco rivers.
Fig. 20
Sternarchella orthos (USNM 228871). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region showing a single row of intermuscular bones in the caudal peduncle, and the discontinuous caudal peduncle membrane. Scale bars = 1 cm.
Fig. 21
Results of geometric morphometric analysis of Sternarchella orthos from river basins of northern South America. a. PC1 corresponds to variation in position of mouth, anus, and posterior head margin. b. PC2 corresponds to variation in opercle width, and position of anus and anal-fin origin.
Fig. 22
Head-shape variation in
Sternarchella orthos from three hydrogeographic regions of Greater Amazonia.
a. Principal components analysis. Position of mouth, anus, and posterior head margin load heavily on PC1, and opercle width and position of anus and anal-fin on in PC2 (
Fig. 7). EA, Eastern Amazon (green); OR, Orinoco (red); WA, Western Amazon (blue), upper Madeira included in EA on both morphometric and hydrogeographic grounds. Note the partial separations among the three populations.
b. Geographic distributions and representative phenotypes of
S. orthos in the three regions.
c. Significant correlation (p= 0.045) between morphometric and river distance among five locations (symbols in panel B). Morphometric distances from CVA of head shape data; river distances as thalweg measured in Google Earth.
Fig. 23
Sternarchella raptor (ANSP 200511). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region. Scale bars = 1 cm.
Fig. 24
Sternarchella schotti in lateral view (INPA 15801). a. Lateral view of the body. b. Lateral view of the head. c. Lateral view of the caudal region showing a single row of intermuscular bones in the caudal peduncle and a discontinuous caudal peduncle membrane. Scale bars = 1.5 cm.
Fig. 25
Sternarchella sima paratype (AMNH 3864). a. Lateral view of the body, b. Lateral view of the head, c. Lateral view of the caudal region showing a single row of intermuscular bones in the caudal peduncle and a discontinuous caudal peduncle membrane. Scale bars = 1 cm.
Tab. 1
Summary of taxonomic data on valid species of Sternarchella.
Tab. 2
Morphometrics and meristic measurements for Sternarchella patriciae. Ranges include holotype.
Tab. 3
Morphometrics and meristic measurements for Sternarchella rex. Ranges include holotype.
Tab. 4
Morphometrics and meristic measurements for Sternarchella calhamazon.
Tab. 5
Morphometrics and meristic measurements for Sternarchella duccis.
Tab. 6
Morphometrics and meristic measurements for Sternarchella orinoco.
Tab. 7
Morphometrics and meristic measurements for Sternarchella orthos.
Tab. 8
Morphometrics and meristic measurements for Sternarchella raptor.
Tab. 9
Morphometrics and meristic measurements for Sternarchella schotti.
Tab. 10
Morphometrics and meristic measurements for Sternarchella sima.
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