Systematics of the tribe Trematocarini (Perciformes: Cichlidae) from Lake Tanganyika, Africa Tetsumi Takahashi Domestic Research Fellow, Japan Science and Technology Corporation, Lake Biwa Museum, Shiga Prefecture, 1091 Oroshimo, Kusatsu, Shiga 525-0001, Japan (e-mail:
[email protected]) Received: December 10, 2001 / Revised: March 18, 2002 / Accepted: April 4, 2002
Ichthyological Research ©The Ichthyological Society of Japan 2002
Ichthyol Res (2002) 49: 253–259
Abstract Phylogenetic relationships among eight Trematocara species and a single Telotrematocara species included in the Tanganyikan cichlid tribe Trematocarini were investigated on the basis of morphological features. The monophyly of the tribe is supported by the presence of hypertrophied sensory pores on the head, tendon “c” of adductor mandibulae section 1, a single scale row between the upper lateral line and body axis, great depth of the anteriormost infraorbital (reversed in Trematocara caparti and T. stigmaticum), and the absence of a lower lateral line. Trematocara is paraphyletic unless Telotrematocara is treated as a junior synonym. Key words
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Trematocarini · Telotrematocara · Synonymy · Lake Tanganyika
he cichlid tribe Trematocarini Poll, 1986 includes two endemic genera in Lake Tanganyika, Trematocara Boulenger, 1899 and Telotrematocara Poll, 1986, with eight and one species of small or moderate-sized mouthbreeders, respectively. Trematocarini is unusual among Tanganyikan cichlids in having hypertrophied sensory pores in the cephalic sensory system, tendon “c” of adductor mandibulae section 1, a small number of upper lateral line scales, and the absence of a lower lateral line (Stiassny, 1981; Poll, 1986). The genus Trematocara was monotypic when proposed, based on T. marginatum Boulenger, 1899. Subsequently, eight additional species have been described: T. unimaculatum Boulenger, 1901, T. nigrifrons Boulenger, 1906, T. stigmaticum Poll, 1943, T. caparti Poll, 1948, T. kufferathi Poll, 1948, T. macrostoma Poll, 1952, T. variabile Poll, 1952, and T. zebra De Vos et al., 1996. Bailey and Stewart (1977) indicated that Trematocara macrostoma was unique within the genus in having minute conical teeth on the dentigerous area extending onto the external surface of the premaxilla and a large mouth in which the maxilla extended posteriorly to below the pupil. Subsequently, Poll (1986) created a new genus Telotrematocara for Trematocara macrostoma in recognition of the unique characters of that species emphasized by Bailey and Stewart (1977). Poll (1986) furthermore created the tribe Trematocarini to include both genera, redefined the genus Trematocara for the remaining seven species, and indicated contrasting characters between genera: teeth not extending onto the external surface of the premaxilla and a short maxilla not reaching the anterior one-third of the eye. Neither the monophyly of Trematocara as redefined nor the status of the aforementioned characters was tested cladistically. In fact, De Vos et al. (1996) doubted the validity of Telotrematocara because one of the diagnostic characters,
the extended dentigerous area on the premaxilla, also occurs in some individuals of Trematocara marginatum and T. stigmaticum. Using a morphological approach to examine the phylogenetic position of Trematocarini within the Cichlidae, Stiassny (1981) suggested that Trematocara [equal to Poll’s (1986) Trematocarini], Bathybates Boulenger, 1898, and Hemibates Regan, 1920 formed a monophyletic group, Hemibates being the sister group of Trematocara on the basis of shared unique conditions of the first levator internus, palatine-mesethmoid ligament, and rostral cartilage on the premaxillae. Based on a genetic analysis, Nishida (1997) supported the monophyly of Trematocarini ⫹ Bathybates ⫹ Hemibates but suggested that a monophyletic group composed of Bathybates and Hemibates was the sister group of Trematocarini. This study attempted to resolve the phylogenetic relationships of species of the tribe Trematocarini on the basis of internal and external morphological characters, using Bathybates and Hemibates as outgroups. A new classification for Trematocarini is proposed based on this phylogeny.
Materials and Methods All specimens examined were obtained from university and museum collections. Ingroups comprised all nine described Trematocarini species and outgroups comprised Bathybates fasciatus, B. graueri, B. minor, and Hemibates stenosoma. To determine the synapomorphies supporting Trematocarini, representatives of ten Tanganyikan cichlid tribes were examined: Astatotilapia burtoni (Haplochromini), Cyprichromis leptosoma (Cyprichromini), Ectodus
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descampsi (Ectodini), Eretmodus cyanostictus (Eretmodini), Gnathochromis permaxillaris (Limnochromini), Haplotaxodon microlepis (Perissodini), Lamprologus lemairii (Lamprologini), Oreochromis (Oreochromis) niloticus (Tilapiini), Tropheus moorii (Tropheini), and Tylochromis polylepis (Tylochromini). A single specimen of each species was dissected, with the exception of Trematocara kufferathi, for which only type specimens were available. In undissected specimens, some internal morphology could be determined through the thin, slightly transparent skin (sensory canals, infraorbitals, and epaxial muscle). Dissections and drawings of specimens were done using a binocular microscope (Nikon SMZ-1000). Osteological characters were examined in specimens stained with Alizarin Red-S in 75% ethyl alcohol or 50% 2-propanol. Osteological and myological terminologies followed Johnson et al. (1996) and Winterbottom (1974), respectively. The term “anteriormost infraorbital” is used instead of “lacrimal.” Standard length and lower jaw length followed Barel et al. (1977), upper jaw length being measured from the anterior tip of the premaxilla to the posterior tip of the maxilla when the mouth was closed. Scale rows counted between the upper lateral line and body axis excluded those positioned on the lateral line and axis. Measurements were made with dividers to the nearest 0.1 mm. A data matrix of 14 characters for all 13 taxa was analyzed with PAUP (version 4.0b4a; Swofford, 2000) using the branch-and-bound algorithm, with equal character weighting. To avoid imposing unjustified models of evolution of multistate characters, they were treated as unordered. A question mark in the matrix is used to indicate missing data, such resulting from the structure being internal, dissection impossible, the character not being resolvable by radiography, and the absence of information in the literature. Trees were rooted by comparisons with the outgroups. Consistency (CI) and retention indices (RI) were generated for the phylogeny as a whole and for each character using PAUP. Materials examined. All specimens were collected from Lake Tanganyika, Africa; asterisks after individual registration numbers indicate dissected specimens. Numbers in parentheses following the scientific name of each species indicate the number of specimens examined. Institutional abbreviations follow Leviton et al. (1985), except for Lake Biwa Museum, Shiga Prefecture, Japan (LBM). Ingroup taxa.—Trematocarini. Telotrematocara macrostoma (1): UMMZ 196106* (88.0 mm SL, Chituta Bay, Zambia, 18 May 1972); Trematocara caparti (3): HUMZ 128583 (45.3 mm SL, Gitaza, Burundi, 60 m depth, 18–19 Oct. 1993), MRAC 111528*, 111529 (47.0–48.4 mm SL, 5 miles east of d’Albertville, Congo, 1 June 1947); T. kufferathi (2): MRAC P.111554, 111555 (paratypes, 45.4–50.0 mm SL, Kazele, Congo, 25 May 1947); T. marginatum (6): HUMZ 128704, 128717, 128729*, 128730, 128736, 128745 (43.8–49.0 mm SL, Gitaza, Burundi, 5–10 m depth, 24–25 Sept. 1993); T. nigrifrons (6): HUMZ 125658, 125659, 125661, 125663*, 125665, 125666 (66.0–74.1 mm SL, Zambia, 1992); T. stigmaticum (5): HUMZ 128683* (45.5 mm SL, Gitaza, Burundi, 2–5 m depth, 13–14 Oct. 1993), HUMZ 128719, 128721, 128724, 128755 (41.5– 45.5 mm SL, Gitaza, Burundi, 5–10 m depth, 24–25, Sept. 1993); T. unimaculatum (6): HUMZ 125760* (90.9 mm SL, Zambia, 1992), HUMZ 128453, 128454, 128479, 128482, 128484 (73.4–86.7 mm SL,
T. Takahashi Gitaza, Burundi, 70 m depth, 8–9 Oct. 1993); T. variabile (2): MRAC 93-152-P-82*, 93-152-P-83 (64.0–65.3 mm SL, Malagarazi, Tanzania, 20 Aug. 1993); T. zebra (2): MRAC 96-083-P-760*, 96-083-P-761 (55.1– 59.5 mm SL, Luhanga, Congo, 30 m depth). Outgroup taxa.—Bathybatini. Bathybates fasciatus (4): HUMZ 116685 (188.2 mm SL, Uvira market, Congo, 17 Aug. 1990), HUMZ 123202 (154.7 mm SL, Chituta Bay, Zambia, 30 m depth, 9 Oct. 1992), HUMZ 123127 (158.3 mm SL, off Nkumbula Is., Zambia 30 m depth, 22 Sept. 1992), HUMZ 138010* (144.9 mm SL, Pemba, Congo, 28 Dec. 1994); B. graueri (4): HUMZ 116686, 116693* (119.2–136.4 mm SL, Uvira market, Congo, 17 Aug. 1990), HUMZ 122977 (155.0 mm SL, Nkumbula Is., Zambia, 65 m depth, 8 Sept. 1992), HUMZ 123134 (122.7 mm SL, off Nkumbula Is., Zambia, 30 m depth, 22 Sept. 1992); B. minor (4): HUMZ 116683 (133.6 mm SL, Uvira market, Congo, 17 Aug. 1990), HUMZ 123199 (151.5 mm SL, Chituta Bay, Zambia, 30 m depth, 9 Oct. 1992), HUMZ 123249 (140.4 mm SL, Chituta Bay, Zambia, 50 m depth, 11 Oct. 1992), HUMZ 125382* (140.8 mm SL, Chituta Bay, Zambia, 55–60 m depth, 13 Oct. 1992; Hemibates stenosoma (4): HUMZ 123094 (175.5 mm SL, Mbete Bay, Zambia, 19 Sept. 1992), HUMZ 123189 (154.8 mm SL, Chituta Bay, Zambia, 30 m depth, 9 Oct. 1992), HUMZ 125365* (150.6 mm SL, Chituta Bay, Zambia, 55–60 m depth, 13 Oct. 1992), HUMZ 125750 (102.2 mm SL, Zambia, 1992). Comparative materials examined.—Cyprichromini. Cyprichromis leptosoma (2): HUMZ 125341* (80.0 mm SL, Mbete, Zambia, 12 Sept. 1992), HUMZ 157401 (82.0 mm SL, Mutondwe, Zambia, 25 Oct. 1995). Ectodini. Ectodus descampsi (1): HUMZ 116672* (70.4 mm SL, Mboko, Congo, 10 Aug. 1990). Eretmodini. Eretmodus cyanostictus (2): HUMZ 125254* (67.0 mm SL, Nkumbula Is., Zambia, 18 Sept. 1992), LBM 25025, 73.3 mm SL (Kasenga, Zambia, 5 m depth, 25 Oct. 2000). Haplochromini. Astatotilapia burtoni (1): HUZM 125825* (60.8 mm SL, Zambia, 1992). Lamprologini. Lamprologus lemairii (3): HUMZ 128372* (165.8 mm SL, Rasi, Cape Banza, Congo, 0–5 m depth, 29 Sept. 1993), LBM 25462 (98.3 mm SL, Kasenga, Zambia, 2 m depth, 10 Nov. 2000), LBM 26317 (90.7 mm SL, Cape Kaku, Zambia, 27 Dec. 2000). Limnochromini. Gnathochromis permaxillaris (3): HUMZ 123122 (125.6 mm SL, Kasenga, Zambia, 19 Sept. 1992), HUMZ 123243, 123245* (123.8–136.4 mm SL, Chituta Bay, Zambia, 50 m depth, 11 Oct. 1992). Perissodini. Haplotaxodon microlepis (2): HUMZ 128381* (192.4 mm SL, Rasi, Cape Banza, Congo, 0–5 m depth, 29 Sept. 1993), LBM 25882 (120.3 mm SL, Cape Kaku, Zambia, 14–17 m depth, 29 Nov. 2000). Tilapiini. Oreochromis (Oreochromis) niloticus (1): HUMZ 116860* (131.1 mm SL, Kavimvira, Congo, 7 Sept. 1990). Tropheini. Tropheus moorii (3): HUMZ 122563* (98.7 mm SL, Nkumbula Is., Zambia, 12 Aug. 1992), LBM 25632 (89.9 mm SL, Wonzye, Zambia, 3 m depth, 20 Nov. 2000), LBM 25943 (80.6 mm SL, Wonzye, Zambia, 2–3 m depth, 2 Dec. 2000). Tylochromini. Tylochromis polylepis (1): HUMZ 125794* (95.3 mm SL, Zambia, 1992).
Results Characters for analysis and additional variations. Characters and state numbers correspond to the numbers in the data matrix (Table 1). The consistency and retention indices for each character follow the character description in the format (CI, RI); when equivalent, only one number is shown. Among all the observed internal and external mor-
Systematics of Trematocarini
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Table 1. Character matrix of Trematocarini and outgroups for cladistic analysis Character numbers 1–5
6–10
11–14
Trematocarini Telotrematocara macrostoma Trematocara caparti Trematocara kufferathi Trematocara marginatum Trematocara nigrifrons Trematocara stigmaticum Trematocara unimaculatum Trematocara variabile Trematocara zebra
10011 121b0 12221 10021 12ab1 12120 10011 11021 10021
01010 11011 11011 11110 11010 11010 01100 11110 01000
1110 1111 11?? 1110 1111 1111 1100 1110 1100
Outgroups Bathybates fasciatus Bathybates graueri Bathybates minor Hemibates stenosoma
00000 00000 00000 00000
00000 00000 00000 00000
0001 0000 0001 0000
a, “0&1”; b, “1&2”
Fig. 1. Lateral view of infraorbitals of (A) Telotrematocara macrostoma, (B) Trematocara variabile, (C) T. stigmaticum, (D) T. kufferathi, and (E) Bathybates minor
phological features, 14 informative characters for the cladistic analysis were found. Three additional variations, although uninformative for the analysis, are also described owing to their significance in the discussion of the validity of the genus Telotrematocara. Character 1: sensory pores on infraorbitals.—0, not hypertrophied; 1, hypertrophied. The sensory canal on the infraorbitals is extremely thick, opening through hypertrophied sensory pores, adjacent pores being almost in contact in the Trematocarini (Fig. 1A–D). In the outgroup taxa, the
sensory canal is thin and the pores not hypertrophied (Fig. 1E). (1.000) Character 2: sensory canal of infraorbitals.—0, present on all infraorbitals; 1, present on anterior two infraorbitals; 2, present on anteriormost infraorbital only. The sensory canal is present on all infraorbitals in Telotrematocara macrostoma, Trematocara marginatum, T. unimaculatum, T. zebra, and all outgroups (Fig. 1A,E), on the anterior two infraorbitals in Trematocara variabile (Fig. 1B), and on the anteriormost infraorbital only in other Trematocarini taxa (Fig. 1C,D). (1.000) Character 3: number of sensory pores on anteriormost infraorbital.—0, five or six; 1, four; 2, three. The sensory canal on the anteriormost infraorbital opens through five sensory pores in Telotrematocara macrostoma, Trematocara marginatum, T. unimaculatum, T. variabile, and T. zebra (Fig. 1A,B), four in Trematocara caparti and T. stigmaticum (Fig. 1C), and three in T. kufferathi (Fig. 1D). In T. nigrifrons, four or five sensory pores were observed, the character being coded as “0&1.” In the outgroup taxa, sensory pores on the bone usually number five, although six were observed in two specimens of Bathybates minor (Fig. 1E). (1.000) Character 4: number of infraorbitals.—0, six or more; 1, five; 2, four. The number of infraorbitals is five in Telotrematocara macrostoma and Trematocara unimaculatum (Fig. 1A), four in T. kufferathi, T. marginatum, T. stigmaticum, T. variabile, and T. zebra (Fig. 1B–D). In T. caparti and T. nigrifrons, four or five infraorbitals are present, the character being coded as “1&2.” In the outgroup taxa, infraorbitals number from six to eight (Fig. 1E). (0.800, 0.750) Character 5: shape of second infraorbital.—0, depth less than length; 1, depth greater than or equal to length. The infraorbitals are broad, the depth of the second being greater than or equal to its length in all Trematocarini (Fig. 1A,B,D), except T. caparti and T. stigmaticum, which have narrow infraorbitals, the depth of the second being less than its length (Fig. 1C). In the outgroup taxa, the infraorbital bones are narrow (Fig. 1E). (0.500, 0.800 in nine maximum parsimonious trees, 0.333, 0.600 in six maximum parsimonious trees) Character 6: number of sensory pores on preopercle.—0, seven; 1, eight. The sensory canal of the preopercle opens through seven sensory pores in Telotrematocara macrostoma, Trematocara unimaculatum, T. zebra, and outgroup taxa (Fig. 2A), but through eight in the remaining Trematocarini taxa (Fig. 2B). (1.000) Character 7: tendon “c” of adductor mandibulae section 1.—0, absent; 1, present. Tendon “c” of adductor mandibulae section 1 (illustrated by Stiassny, 1981: Fig. 11), which is inserted onto the medial face of the anteriormost infraorbital, is present in Trematocarini. In the outgroup taxa, tendon “c” is absent. (1.000) Character 8: lower jaw.—0, protruding; 1, level with upper jaw. The anterior tip of the lower jaw is level with the upper jaw in Trematocara marginatum, T. unimaculatum, and T. variabile, but protrudes beyond the latter in the remaining Trematocarini and the outgroup taxa. (0.500) Character 9: size of outer teeth on premaxilla.—0, large; 1, small. Teeth on the premaxilla arrange in several rows. The
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Fig. 2. Lateral view of preopercle of (A) Telotrematocara macrostoma and (B) Trematocara marginatum
Fig. 4. Dorsal view of head of (A) Trematocara marginatum and (B) T. caparti. NLF0, NLF3, neurocranial lateral line foramen 0 and 3, respectively
Fig. 3. Anterior view of premaxillary teeth on middle of alveolar process in (A) Trematocara zebra and (B) T. variabile. i, inner tooth; o, outer tooth
teeth on the outermost row (outer teeth) are longer and thicker than those on the inner rows (inner teeth) in Trematocara unimaculatum, T. zebra, and the outgroups (Fig. 3A). In the remaining Trematocarini, the outer teeth are the same size as or shorter than the inner teeth (Fig. 3B). (1.000) Character 10: epaxialis on dorsal part of head.—0, reaching neurocranial lateral line foramen 0; 1, not reaching neurocranial lateral line foramen 0. The epaxialis muscle extends onto the dorsal part of the head, reaching neurocranial lateral line foramen 0 (sensu Barel et al., 1977) and the posterior wall of the sensory canal between neurocranial lateral line foramina 0 and 3 in most Trematocarini and all outgroups (Fig. 4A). In Trematocara caparti and T. kufferathi, however, the muscle fails to reach
foramen 0 and the sensory canal (Fig. 4B). (0.500, 0.000 in nine maximum parsimonious trees, 1.000 in six maximum parsimonious trees) Character 11: lower lateral line.—0, present, 1, absent. The lower lateral line is absent in Trematocarini species but present in the outgroup taxa. (1.000) Character 12: number of scale rows between upper lateral line and body axis.—0, four to six; 1, one. Trematocarini taxa all have a single scale row between the upper lateral line and body axis. In the outgroup taxa, the scale rows number four to six. (1.000) Character 13: neural and hemal spines of fourth preural vertebra.—0, thin; 1, broad. In Trematocara unimaculatum, T. zebra, and outgroups, the neural and hemal spines of the fourth preural vertebra are as thin as those on more anterior vertebrae (Fig. 5A), whereas they are broader than the latter in the remaining Trematocarini (Fig. 5B). Trematocara kufferathi, which was not examined, is coded as “?”. (1.000) Character 14: supraneural.—0, present; 1, absent. Among the Trematocarini, a single supraneural is usually present just anterior to the neural spine of the anteriormost vertebral centrum, but is absent in Trematocara caparti, T. nigrifrons, and T. stigmaticum. Trematocara kufferathi was not examined and is coded as “?”. Among the outgroup taxa, Bathybates graueri and Hemibates stenosoma have a
Systematics of Trematocarini
257 Table 2. Upper and lower jaw lengths relative to head length (UJL %HL and LJL %HL) in the tribe Trematocarini and outgroup taxa
Fig. 5. Lateral view of caudal skeleton of (A) Trematocara unimaculatum and (B) T. marginatum. h1 to 5, first to fifth hypurals
single supraneural, that element being absent in B. fasciatus and B. minor.(0.500, 0.750) Additional variation 1: mouth size.—The mouth is extremely large in Telotrematocara macrostoma, the posterior corner almost reaching level with the eye center (upper and lower jaw lengths 47.6% and 58.7% of head length, respectively; Table 2), and small in Trematocara marginatum, the posterior tip not extending to level with the anterior margin of the eye (upper and lower jaws 30.4–32.9% and 37.1– 38.8% of head, respectively). In other Trematocarini and the outgroups, the mouth size ranges between Telotrematocara macrostoma and Trematocara marginatum, the upper and lower jaw lengths being 32.0–42.8% and 41.0–52.1% of the head length, respectively. This variation was not appropriate for the cladistic analysis, because each large and small mouth type was found in a single species only, the variation therefore being uninformative for an analysis based on unordered character cording. Additional variation 2: first and second hypurals.—The first and second hypurals are separated in Trematocara
UJL %HL
LJL %HL
Trematocarini Telotrematocara macrostoma Trematocara caparti Trematocara kufferathi Trematocara marginatum Trematocara nigrifrons Trematocara stigmaticum Trematocara unimaculatum Trematocara variabile Trematocara zebra
47.6 34.5–34.6 35.5–35.9 30.4–32.9 39.6–42.8 37.7–40.3 33.2–36.5 36.3–38.1 37.5–39.4
58.7 44.0–46.8 46.2–47.0 37.1–38.8 47.8–51.4 46.1–49.1 41.0–44.5 42.9–43.4 46.5–48.5
Outgroups Bathybates fasciatus Bathybates graueri Bathybates minor Hemibates stenosoma
35.4–35.7 34.2–36.4 38.5–41.7 32.0–34.4
44.4–46.2 45.8–48.0 47.6–52.1 43.5–45.0
Fig. 6. Lateral view of premaxilla of (A) Trematocara unimaculatum and (B) Telotrematocara macrostoma
unimaculatum (Fig. 5A) but fused in the remaining Trematocarini species and outgroup taxa (Fig. 5B). This variation was not appropriate for the cladistic analysis, because separated hypurals were found in a single species only. Additional variation 3: teeth on upper jaw.—Upper jaw teeth usually limited to the ventral surface of the premaxilla in Trematocarini and the outgroup taxa (Fig. 6A), extend to the lateral surface of the premaxilla in Telotrematocara macrostoma and Trematocara stigmaticum (Fig. 6B). However, De Vos et al. (1996) reported polymorphism of this feature in Trematocara stigmaticum. Being limited, therefore, to a single species, this variation was not appropriate for the cladistic analysis. Cladistic analysis. As a result of the analysis, 15 maximum parsimonious trees were obtained (TL ⫽ 25, CI ⫽ 0.8000, RI ⫽ 0.8936). A strict consensus tree is shown in Fig. 7. State 1 of characters 1, 5, 7, and 11 in Trematocarini were interpreted as synapomorphies because they were not
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Trematocara variabile, state 2 being a synapomorphy supporting a clade including T. caparti, T. kufferathi, T. nigrifrons, and T. stigmaticum. State 1 of character 8 homoplastically supports two clades, one including Trematocara unimaculatum and another including T. marginatum and T. variabile. Characters 3 and 10 vary within the sister group of Telotrematocara macrostoma. Optimizations of these characters were not possible because the interrelationships within the clade remain unresolved. Character 14 could not be optimized within the ingroup because of the unknown character states in Trematocara kufferathi and the nonresolution of the interrelationships within the sister group of Telotrematocara macrostoma.
Discussion Fig. 7. Strict consensus tree of 15 cladograms generated by parsimony analysis of 14 morphological characters for nine species of tribe Trematocarini (ingroup) and four outgroup taxa (tree length 25, consistency index 0.8000, retention index 0.8936), with three alternative classification hypotheses. Character numbers, with plesiomorphic (left) and apomorphic (right) state numbers in parentheses, correspond to those listed in Table 1. Characters 3, 4, 5, 10, and 14 not or only partially indicated, owing to uncertain optimization (see text for details)
observed in other Tanganyikan cichlid fishes examined. Among these characters, character 5 represents a reversal in Trematocara caparti and T. stigmaticum; optimization of this character between these taxa was uncertain, however, because the relationship between the taxa was unresolved. As regards character 12, the number of scale rows between the upper lateral line and body axis was one in Trematocarini (state 1), but four to six in outgroups (state 0). In other Tanganyikan cichlids examined, the scale rows always number two or more (two in Asprotilapia burtoni, Ectodus descampsi, Eretmodus cyanostictus, Gnathochromis permaxillaris, Lamprologus lemairii, Oreochromis (Oreochromis) niloticus, and Tropheus moorii, three in Tylochromis polylepis, four in Cyprichromis leptosoma, and five in Haplotaxodon microlepis). Therefore, the state 1 of this character was also interpreted as synapomorphies supporting Trematocarini. Character 4 exists as state 1 and/or 2 in all the ingroup taxa but as 0 in all outgroup taxa. In other Tanganyikan cichlid fishes examined, all three character states were found [state 0 in Cyprichromis leptosoma, Haplotaxodon microlepis, Oreochromis (Oreochromis) niloticus, Tropheus moorii, and Tylochromis polylepis; state 1 in Astatotilapia burtoni; state 2 in Ectodus descampsi and Eretmodus cyanostictus]. Because the phylogenetic position of a clade including Trematocarini ⫹ Bathybates ⫹ Hemibates is still uncertain within Tanganyikan cichlids, optimization of this character was not possible. State 1 of characters 9 and 13 supports a clade including Telotrematocara macrostoma and its sister group, whereas state 1 of character 6 supports the monophyly of a sister group of T. macrostoma. State 1 of character 2 is an autapomorphy of
Poll (1986) recognized two genera, Trematocara (type species: T. marginatum) and Telotrematocara (type species: T. macrostoma), in the tribe Trematocarini, defining the former as having a relatively small mouth and upper jaw teeth not occurring on the lateral surface of the premaxilla. These characters are in fact plesiomorphic, being found in the outgroup taxa (additional variations 1 and 3 in Results) and other Tanganyikan cichlid fishes. Thus, they were inappropriate for defining Trematocara. Furthermore, the present cladogram indicates that Poll’s (1986) Trematocara does not form a monophyletic group, Telotrematocara macrostoma being embedded within current members of the former genus (see Fig. 7). Accordingly, Poll’s classification of Trematocarini should be revised. A new classification based on the present cladogram may follow one of three courses. Telotrematocara can be treated as a synonym of Trematocara, thereby recognizing only a single genus in the tribe Trematocarini (classification A of Fig. 7). Alternatively, if Telotrematocara is treated as a valid genus, a new genus should be established for Trematocara unimaculatum and T. zebra, thereby recognizing three genera (classification B of Fig. 7), or two new monotypic genera should be recognized, for Trematocara unimaculatum and T. zebra, respectively, thereby recognizing four genera (classification C of Fig. 7). In consideration of classification B, no synapomorphies supporting a clade composed of Trematocara unimaculatum and T. zebra were found, so the establishment of a new genus for these two species would be unfounded. As for classification C, the characters possibly supporting separate genus-level status for these two species are discussed in turn. Trematocara zebra was diagnosed by six characters (De Vos et al., 1996), but three count characters overlap with those of other species of Trematocara (12– 13 gill rakers versus 9–12 in T. marginatum, 8 openings of sensory canal on the infraorbitals versus 8–9 in T. marginatum, and 7–8 anal fin soft rays versus 8–9 in T. kufferathi) (De Vos et al., 1996). Another character, a high dorsal fin, appears to be a general condition in Trematocara (De Vos et al., 1996: Fig. 5). The remaining two diagnostic characters, the vertical bands on the body and the elongated anal soft ray, are both unique in the Trematocarini. Because morphological aspects of T. zebra are known only from its
Systematics of Trematocarini
original description (De Vos et al., 1996), and the variations of these two characters has not been documented sufficiently, I think these characters are inappropriate for defining a new genus for T. zebra. These features commonly vary with locality, growth, and sex in Tanganyikan cichlids (Poll, 1956; Kohda et al., 1996). As for the second species, two character states distinguish T. unimaculatum from the remaining Trematocarini species [upper and lower jaws level (state 1 of character 8) and separated hypurals 1 and 2 (additional variation 2)]. State 1 of character 8 also occurs homoplastically in T. marginatum and T. variabile, and separation of hypurals 1 and 2 has often been observed in other African cichlids (Vandewalle, 1973). Because the phylogenetic position of a clade Trematocarini ⫹ Bathybates ⫹ Hemibates is still uncertain within African cichlids, the optimization of separated hypurals could not be decided, the condition being either an autapomorphy of T. unimaculatum or plesiomorphic for the clade Trematocarini ⫹ Bathybates ⫹ Hemibates. Either optimization being possible, the variation was determined as insufficient for defining a new genus comprising T. unimaculatum. Therefore, classification C was rejected, given the paucity of diagnostic characters for two new genera based on Trematocara unimaculatum and T. zebra. Other classifications based on the present cladogram all require the establishment of a new genus for T. unimaculatum and/or T. zebra, or two new genera for each species. Such classifications must be rejected for the same reasons as given for the classifications B and C. On the other hand, the tribe Trematocarini was supported by five synapomorphies [hypertrophied sensory pores on infraorbitals (state 1 of character 1), extreme depth of anteriormost infraorbital (state 1 of character 5; reversed in Trematocara caparti and T. stigmaticum), presence of tendon “c” of adductor mandibulae section 1 (state 1 of character 7), absence of lower lateral line (state 1 of character 11), and a single scale row between the upper lateral line and body axis (state 1 of character 12)], generic ranking for the same clade being possible owing to the presence of apomorphies (classification A of Fig. 7). Accordingly, Telotrematocara is here treated as a junior synonym of Trematocara, the latter being the only genus now recognized in the tribe Trematocarini. Acknowledgments I express my sincere thanks to Dr. K. Amaoka (formerly HUMZ) and Prof. K. Nakaya (HUMZ) for their valuable advice and the loan of specimens examined, to Drs. J. Snoeks, G.G. Teugels (MRAC), and W.L. Fink (UMMZ) for the loan of specimens, to
259 Drs. G.S. Hardy (Ngunguru, New Zealand) and M.J. Grygier (LBM) for their advice and comments on the manuscript, to Assistant Prof. H. Imamura (The Hokkaido University Museum) for his analysis of the phylogenetic relationships presented in this study, and to Messrs. M. Aibara and Y. Furuyama (HUMZ) for their kind assistance. This study was partly supported by a Grant-in-Aid for Overseas Scientific Survey from the Ministry of Education, Science, Sports and Culture, Government of Japan.
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