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The high diversity of sex chromosomes and sex determination systems among haplotilapiines suggests that this large cichlid clade is a good model for investigating the evolution of genetics of sex determination. Nonetheless, information about sex determination in this clade remains sparse. The present study reports a microsatellite marker that is closely associated with sex in Xenotilapia rotundiventralis from Lake Tanganyika, Africa. This study is the first to suggest the role of linkage group 17 in sex determination in haplotilapiine cichlids.

Telmatochromis temporalis is a cichlid fish endemic to Lake Tanganyika. Two morphs of this species, normal and dwarf, form a good model for the study of ecological speciation through divergent natural selection on body size. This study reports a third morph of this species, slender morph, which was collected from deep waters off Kasenga, Zambia, whereas the normal morph inhabits shallow waters of the same locality. This study examined morphological characters and mitochondrial DNA sequences in 18 populations of the three T. temporalis morphs and two closely related species. The slender morph was morphologically similar to the normal and dwarf morphs of the same species, but clearly differed from closely related species. Genetic analyses showed that the slender morph was closest to but significantly different from the parapatric normal morph, suggesting reproductive isolation between them. Due to the lack of colour differences between morphs and of obvious geographical barriers between habitats, reproductive isolation between these morphs may be attributed to ecological factors, rather than sexual or geographical segregation. Further studies examining the evolution of the slender morph may deepen our knowledge of initial stages of speciation, like in the dwarf morph.

The cuckoo catfish Synodontis multipunctatus and S. grandiops are endemic to Lake Tanganyika and the only known nonavian vertebrates that exhibit obligate interspecific brood parasitism. Seven maternal mouth-brooding cichlid fish species are reported to be natural hosts of the parasitic catfish and share a common reproductive behaviour that the catfish exploits: cichlid females spawn eggs on the bottom, allowing the catfish female to place her eggs near the cichlid eggs, and the cichlid females collect the catfish eggs by mouth together with their own eggs. However, so far it has not been reported that the cuckoo catfish exploit different spawning behaviours. The genus Cyprichromis consists of five maternal mouth-brooding species endemic to Lake Tanganyika, most of which spawn and collect eggs in open water. This study reports that the cuckoo catfish also parasitizes the open-water spawning Cyprichromis coloratus, although it may not be a regular host.

Rhodeus ocellatus kurumeus is a small cyprinid fish endemic to the Japanese archipelago. This fish frequently hybridizes with an exotic subspecies Rhodeus ocellatus ocellatus, and non-introgressed populations of R. o. kurumeus have greatly decreased. Previous studies based on mitochondrial and nuclear DNA identified introgressed populations and inferred phylogenetic relationships, but these approaches may lead to underestimates of introgression or ambiguous results owing to the small number of genetic markers used. The present study applied double digest restriction site-associated DNA (ddRAD) sequencing to assignment tests and phylogenetic inferences. Data matrices can vary in size and content depending on the strategies used to process ddRAD sequences; therefore, we prepared 25 data matrices with various processing strategies. The assignment tests based on the 25 data matrices resulted in similar assignment patterns and provided evidence for introgression in some populations that had been identified as non-introgressed populations in previous studies. The maximum-likelihood (ML) phylogenetic trees differed in robustness and topology among the 25 matrices; interestingly, ML trees with low statistical support reflected geographical distributions of fish better than ML trees with high statistical support. These results indicate that ddRAD sequencing can detect introgression with greater sensitivity than conventional DNA markers, that ddRAD sequencing is useful for phylogenetic inference among closely related populations within a subspecies, and that statistically robust ML trees do not necessarily reflect the true phylogeny. Application of ddRAD data to conservation genetics and evolutionary history of this subspecies are also discussed.

Background Telmatochromis temporalis is a cichlid fish endemic to Lake Tanganyika. The normal and dwarf morphs of this fish are a clear example of ongoing ecological speciation, and body size plays an important role in this speciation event as a magic trait. However, the genetic basis underlying this trait has not been studied. Results Based on double-digested restriction-site associated DNA (ddRAD) sequencing of a hybrid cross between the morphs that includes F0 male, F0 female, and 206 F2 individuals, we obtained a linkage map consisting of 708 ddRAD markers in 22 linkage groups, which corresponded to the previously reported Oreochromis niloticus chromosomes, and identified one significant and five suggestive quantitative trait loci (QTL) for body size. From the body-size distribution pattern, the significant and three of the five suggestive QTL are possibly associated with genes responsible for the difference in body size between the morphs. Conclusions The QTL analysis presented here suggests that multiple genes, rather than a single gene, control morph-specific body size. The present results provide further insights about the genes underlying the morph specific body size and evolution of the magic trait during ecological speciation.

The dwarf morph of Telmatochromis temporalis uses empty snail shells as shelters and spawning sites. This morph varies in body colour from pale to dark within populations. Pale individuals are likely to be cryptic on sandy-brown backgrounds through colour matching, but adaptive significance of dark individuals is unknown. The present study proposes two hypotheses for the occurrence of dark individuals: crypsis in darkness inside shells (darkness matching) and crypsis in irregular patterns consisting of shell shadows on sandy-brown backgrounds (pattern matching). The former hypothesis is less likely to be the main factor evolving dark bodies, because body darkness was not correlated with the amount of time that the fish remained within shells. Body darkness was correlated with shell density in their habitats, supporting the latter hypothesis because dark individuals may be able to mingle with shell shadows effectively at sites where shells were abundant. This study also found that body darkness was environmentally induced; therefore, this fish may shift between these anti-predator tactics (crypsis of pale individuals on sandy-brown backgrounds through colour matching and crypsis of dark individuals in irregular shadow patterns through pattern matching) by changing body darkness in response to shell density.

Nuchal humps occur in various fish groups, but their functions are rarely studied. Both sexes of Cyphotilapia gibberosa, a cichlid fish endemic to Lake Tanganyika, possess nuchal humps. This study morphologically analysed the humps of this species to assess the primary factors responsible for hump development. Semi-landmarks showed that the size of male humps positively correlated with body condition, and thicknesses of hypodermises implied that the humps were larger in males than in females. These facts suggest that sexual selection on male humps is intense. Semi-landmarks showed that the humps were less prominent in females than in males, and that the transformation of nuchal humps with growth (becoming more prominent) ceased at medium body size in females. These facts suggest that sex recognition likely plays a role in the evolution of the uniform humps of large females, because, according to this hypothesis, a morphologically moderate hump may be favoured. If male humps also function as a sex recognition trait, the transformation of nuchal humps is expected to cease at a certain body size, as did female humps. However, the male humps became continuously more prominent from the smallest to the largest individuals examined. The body size at which hump transformation stops or at which extreme hump shape interferes with sex recognition may be outside of the size range of the present samples. A prominent nuchal hump may also function as a species recognition trait, because sympatric cichlid species do not develop nuchal humps as prominent as this species. In short, the present morphological analyses do not contradict the hypotheses that C. gibberosa individuals recognise conspecifics and their sex from the shapes of the nuchal humps, and that females prefer males with larger humps.

Masquerade is a strategy whereby prey animals resemble environmental objects (e.g. twigs, bird droppings and stones) or inedible animals to avoid predatory attack. However, most studies of this strategy have been restricted to only a few animal groups. Therefore, novel examples are required to elucidate the diversity of masquerade strategies. Neolamprologus furcifer is a maternal nest-brooding cichlid inhabiting shaded areas of large rocks in Lake Tanganyika. In contrast to the cryptic, dark brown adults, the small young have well-defined white stripes on their brown trunk in nest territories where many white-striped snails Reymondia horei are present. We hypothesized that young N. furcifer masquerade as the model snail R. horei. We found four results consistent with our hypothesis. (1) The size, coloration, shape and posture of the young fish resembled those of the snail. (2) Experimental removal of the model snail from territories caused females to attack predators more frequently than before the removal, indirectly suggesting the protective value of the young fish's coloration. (3) Parental females selectively removed nonmodel snails from their territory, probably causing the higher density of R. horei observed at nest sites. (4) Guarded young had black/white coloration only in populations where the model snails were present. Therefore, we suggest that young N. furcifer masquerade as the model snail R. horei. This study describes a novel masquerade pattern in which the protective value is improved by, and beneficial to, a third party.

Delayed dispersal of offspring from the natal territory is an important process in the evolution of cooperative breeding. Ecological constraints such as habitat saturation can promote delayed dispersal. Thus far, the role of predation risk in the evolution of cooperative breeding systems has received less attention, although it is understood as an important ecological factor shaping dispersal patterns and social structure in animals. To bridge this gap, we analysed group structure and dispersal patterns of helpers within a population of the cooperatively breeding cichlid Neolamprologus obscurus. We conducted behavioural observations for a period of 3 months at two study sites within this population, which differed in predation risk and availability of unoccupied space. Furthermore, by combining field observations with molecular analyses, we assessed group structure to unravel the dispersal patterns of helpers. At the high predation risk location, we found that helpers (1) had a lower dispersal propensity, (2) dispersed shorter distances and (3) were generally larger. Furthermore, molecular analyses and body size measurements suggest that helpers may stay longer in the natal territory under high predation risk than under low predation risk. Groups contained more helpers in the high predation risk site, which indicates that high predation pressure leads to delayed dispersal of helpers. Unoccupied potential dispersal areas were larger in the high predation risk site, suggesting that habitat saturation did not account for the dispersal patterns. Our results suggest that predation pressure is the main factor limiting the dispersal of helpers in the cooperatively breeding cichlid fish N. obscurus, and might be overlooked in other studies focusing on the evolution of cooperative breeding systems.

The huge monophyletic group of the East African cichlid radiations (EAR) consists of thousands of species belonging to 12-14 tribes; the number of tribes differs among studies. Many studies have inferred phylogenies of EAR tribes using various genetic markers. However, these phylogenies partly contradict one another and can have weak statistic support. In this study, we conducted maximum-likelihood (ML) phylogenetic analyses using restriction site-associated DNA (RAD) sequences and propose a new robust phylogenetic hypothesis among Lake Tanganyika cichlid fishes, which cover most EAR tribes. Data matrices can vary in size and contents depending on the strategies used to process RAD sequences. Therefore, we prepared 23 data matrices with various processing strategies. The ML phylogenies inferred from 15 large matrices (2.0×10(6) to 1.1×10(7) base pairs) resolved every tribe as a monophyletic group with 100% bootstrap support and shared the same topology regarding relationships among the tribes. Most nodes among the tribes were supported by 100% bootstrap values, and the bootstrap support for the other node varied among the 15 ML trees from 70% to 100%. These robust ML trees differ partly in topology from those in earlier studies, and these phylogenetic relationships have important implications for the tribal classification of EAR.

The fish genus Orestias is endemic to the Andes highlands, and Lake Titicaca is the centre of the species diversity of the genus. Previous phylogenetic studies based on a single locus of mitochondrial and nuclear DNA strongly support the monophyly of a group composed of many of species endemic to the Lake Titicaca basin (the Lake Titicaca radiation), but the relationships among the species in the radiation remain unclear. Recently, restriction site-associated DNA (RAD) sequencing, which can produce a vast number of short sequences from various loci of nuclear DNA, has emerged as a useful way to resolve complex phylogenetic problems. To propose a new phylogenetic hypothesis of Orestias fishes of the Lake Titicaca radiation, we conducted a cluster analysis based on morphological similarities among fish samples and a molecular phylogenetic analysis based on RAD sequencing. From a morphological cluster analysis, we recognised four species groups in the radiation, and three of the four groups were resolved as monophyletic groups in maximum-likelihood trees based on RAD sequencing data. The other morphology-based group was not resolved as a monophyletic group in molecular phylogenies, and some members of the group were diverged from its sister group close to the root of the Lake Titicaca radiation. The evolution of these fishes is discussed from the phylogenetic relationships.

With about 1,300validlydescribedspecies,butatleast2,200 species known, cichlid fishes (Cichlidae) repre-sent the second most species-rich family of freshwaterfishaftertheCyprinidae(2,700describedspecies),andaccount for about 13% of extant freshwater fishdiversity. They are naturally distributed from Centraland South America, across Africa to Madagascar, andsouthern India. Throughout this distributional range,they have repeatedly demonstrated their capacity offorming adaptive radiations—explosive speciationwith niche partitioning—generating an outstandingvariation of body shapes, color patterns, behavior, andecomorphological specializations (e.g., Schliewenet al., 1994; Danley & Kocher, 2001; Joyce et al.,2005; Barluenga et al., 2006; Muschick et al., 2012;Lo´pez-Ferna´ndez et al., 2013). This extraordinarydiversity and an often stunning pace of speciationmakes cichlid fishes particularly well suited forstudying the factors and mechanisms underlyingpopulation differentiation, diversification, and spe-ciation. They are now well established among theprime model systems in evolutionary biology research(Kocher, 2004; Seehausen, 2006). With the develop-ment of an increasing number of genetic and genomicresources, including the recent sequencing of severalcichlid genomes (Brawand et al. 2014), cichlids willreceive even greater attention in future evolutionaryand ecological research.This special issue comprises sixteen studies with aparticular focus on behavior, ecology, and/or evolu-tionary biology of cichlid fishes. Together, theyadvance our knowledge of the mechanisms generatingand maintaining the tremendous diversity of thisfreshwater fish family.Over the last few decades, a multitude of studieshave employed various approaches to shed light on thefactors responsible for the stunning diversity withinthis family. An elaborate reproductive behavior and ahighly developed pharyngeal jaw have long beenrecognized as important key factors for the cichlids’evolutionary success (Liem, 1973; Keenleyside

Based on morphological and molecular analyses of a Petrochromis fish (Cichlidae) from the southern end of Lake Tanganyika, this fish is considered a taxonomic species distinct from the six known congeners. A new scientific name is proposed for this fish. A key to the seven Petrochromis species is included.

The infraorbitals (IOs) of four species endemic to Lake Tanganyika were examined and on the basis of this information and previous morphological and molecular studies, the tribe Greenwoodochromini is synonymized with the tribe Limnochromini and a new combination for Limnochromis abeelei and Limnochromis staneri is proposed: Greenwoodochromis abeelei and Greenwoodochromis staneri. The revised tribe Limnochromini, comprising 10 species belonging to seven genera, is characterized by IOs representing types G and I. The revised genus Greenwoodochromis, which consists of four species, is characterized by IOs representing type I.

The substrate-brooding cichlid fish Telmatochromis temporalis in Lake Tanganyika demonstrates a simple example of ecological speciation between normal and dwarf morphs through divergent natural selection on body size. The dwarf morph most likely evolved from the ancestral normal morph; therefore, elucidating the evolution of its small body size is a key to understanding this ecological speciation event. Previous studies suggest that the small body size of the dwarf morph is an adaptation to the use of empty snail shells as shelters (males) and spawning sites (females), but this idea has not been fully evaluated. Combining original and previously published information, this study compared likelihood values to determine the primary factor that would be responsible for regulating the body size of the dwarf morph. Male body size is most likely regulated by the ability to turn within shells, which may influence the predation avoidance of adult fish. Females are smaller than males, and their body size is most likely regulated by the ability to lay eggs in the small spaces within shells close to the shell apices where predation risk on eggs is lower. This study provides new evidence supporting the hypothesis that different natural selection factors affected body size of the different sexes of the dwarf morph, which has not been reported in other animal species.

Divergent natural selection is thought to play a vital role in speciation, but clear,measurable examples from nature are still few. Among the many possible sources ofdivergent natural selection, predation pressure may be important because predators areubiquitousinfoodwebs.Here,weshowevidencefordivergentnaturalselectioninaLakeTanganyika cichlid, Telmatochromis temporalis, which uses burrows under stones orempty snail shells as shelters. This species contains normal and dwarf morphs at severallocalities. The normal morph inhabits rocky shorelines, whereas the dwarf morphinvariably inhabits shell beds, where empty snail shells densely cover the lake bottom.Geneticevidencesuggestedthatthedwarfmorphevolvedindependentlyfromthenormalmorph at two areas, and morphological analysis and evaluation of habitat structurerevealed that the body sizes of morphs closely matched the available shelter sizes in theirhabitats.Thesefindingssuggestthatthetwomorphsrepeatedlyevolvedthroughdivergentnatural selection associated with the strategy for sheltering from predators.Keywords: adaptation, Africa, geometric morphometrics, microsatellite, mitochondrial DNA,shell bedReceived 3 September 2008; revision received 18 March 2009; accepted 17 April 2009

Benthochromis horii, a new cichlid species is described based on 19 type specimens from the deep waters of Lake Tanganyika. It differs from its congeners by having smaller eyes and longer snout (eye length usually shorter than snout length v. equal to or longer than snout length in Benthochromis tricoti and Benthochromis melanoides), and more dorsal fin rays (total number of spines and soft rays in dorsal fin usually 30 or 31 v. usually 28 or 29 in B. tricoti and B. melanoides). Large males of the new species differ from those of congeneric species in terms of their body colour pattern and long pelvic fins. This species has been confused with B. tricoti and has been traded as an aquarium fish.

The road surface repair material of cold hardening type was tested for workability such as self-leveling, hardened properties, and hardening time for opening the traffic. The flow test was suitable for testing on self-leveling characteristics and the allowable flow time for the characteristic was 4 to 10 s and the handling time after mixing was 10 min at 20°C. The properties of hardened repair material were almost the same as those of a dense-grade hot asphalt mixture. The rutting resistance was superior to the dense-grade hot asphalt mixture. Flexural property and strength of this road repair material were satisfactory for bonding on the existing road surface. Its hardening time could be evaluated by using the durometer with semi-globular shape type of press needle and the hardness for early opening the traffic was approximately 85 at 60 min after finishing the repair work at 20°C.

The Identification System for Tanganyikan Cichlids (ISTC) is a computer system that identifies the species of Tanganyikan cichlids based on five meristic and three descriptive characters. An index I i is proposed as the degree of proximity between an unidentified specimen and species i. For calculating this index, the system allows the use of the following: (i) the range data including the largest and smallest values of meristic characters; and (ii) the meristics, between which the correlations are unknown. Therefore, a large amount of data accumulated in literature can be used. This system is sufficiently practical, although the methods are simplified and mathematically coarse.

Lepidiolamprologus mimicus n. sp. is described from material collected along the Zambian coast of Lake Tanganyika. It is distinguished from congeners by its unique color pattern of bright yellow fins, a brownish-tan flank coloration and large, dark brown spots along the flanks, in addition to a series of meristic and morphometric characters. Lepidiolamprologus mimicus n. sp. exhibits an interesting feeding ecology, in which individuals blend into schools of their prey, yellow-finned cyprichromines, with the aid of similar coloration. This is the first instance of aggressive mimicry reported for lamprologines.

Six- and seven-band morphs have been identified in a cichlid, Cyphotilapia frontosa, that is endemic to Lake Tanganyika. These color morphs have allopatric distributions; the six-band morph is widespread in the northern half of the lake while the seven-band morph is restricted to Kigoma on the east coast of the lake. Because no specimens of the seven-band morph have been available for taxonomic study except for the holotype of C. frontosa, the taxonomic status of these morphs has not been discussed. In a recent survey at the lake, 21 specimens of the seven-band morph were collected. A comparison of these with existing collection specimens of the six-band morph showed significant differences in morphometric and meristic characters; however, because all characters largely overlapped between these morphs, they are regarded as conspecific.

The road surface repair material of cold hardening type was tested on the workability such as self-leveling, hardened properties and hardening time for opening the traffic. The flow test was suitable for testing on self-leveling characteristics and the allowable flow time for the characteristic was 4 to 10seconds and the handling time after mixing was 10minutes at 20degree Celsius. The properties of hardened repair material were almost the same as those of dense grade hot asphalt mixture. The rutting resistance was superior to dense grade hot asphalt mixture. Flexural property and strength of this road repair material were satisfactory for bonding on the existing road surface. The hardening time of this repair material could be evaluated by the durometer with semi-globular shape type of press needle and the hardness for opening the traffic was about 85 at 60minutes after finishing the repair work at 20degree Celsius.

Cyprichromis coloratus, a new cichlid species, is described based on 41 type specimens from the Zambian coast of Lake Tanganyika. It differs from Cyprichromis microlepidotus by having fewer scales in the longitudinal line (41-44 v. 59-70 in C. microlepidotus) and upper lateral line (31-36 v. 47-59), from Cyprichromis leptosoma by more dorsal-fin spines (14-15 v. 11-13 in C. leptosoma) and longitudinal line scales (41-44 v. 38-40), from Cyprichromis pavo by fewer dorsal-fin spines and soft rays (29-31, usually 30, in total v. 30-32, usually 31, in C. pavo), and from Cyprichromis zonatus by shallower body depth [24-0-28-5 (26-4 ±1-1) % of standard length v. 24-5-30-5 (28.4 ±1-3) % in C. zonatus] and smaller eye [eye length 25-2-30-9 (27-2 ± 1-1) % of head length v. 27·9-33·3 (30·2 ± 1·2) %]. The new species is also separable from C. microlepidotus, C. pavo and C. zonatus by absence of distinct small spots on the body (v. pearl grey and yellowish small spots along scale rows on body at least in males of C. microlepidotus and C. pavo), its distinct dichromatism (particularly on the caudal fin) between males of the same population (v. dichromatism absent in C. zonatus) and absence of vertical bands (v. three or four distinct vertical bands beneath dorsal fin base in live males of C. zonatus). Cyprichromis coloratus n. sp. also exhibits sexual dimorphism, females having a larger head and males having longer pelvic fin, differences which are discussed in relation to reproductive behaviour. A key to the five species of Cyprichromis is included. A lectotype is designated for Cyprichromis leptosoma.

The recent increase in numbers of individuals of a piscivorous bird, the great cormorant Phalacrocorax carbo hanedae, around Lake Biwa has affected the commercial catch of ayu Plecoglossus altivelis altivelis. The food habits of the bird were studied based on 66 stomachs in 1998 and 2001–2002, and a seasonal variation in food contents was observed. The proportion of ayu in stomachs increased after April, and became most dominant during July and August (0.62 in proportion of weight, 0.85 in frequency of occurrence). In contrast, ayu was not found in the stomachs after late October. The increase of ayu in individuals and density in the surface layer of the pelagic zone of the lake during spring was considered as a trigger for the change of the food habits of the birds. The feeding impact of great cormorant on ayu in Lake Biwa was estimated to be approximately 46 t during April to June, and 310 t in July and August. During the main period for the commercial ayu catch (November to the following June), the estimated mass consumed by the bird is much smaller in comparison with the commercial catch.

A detailed morphological comparison of Trematochromis schreyeni only known from its holotype, collected at the north-western end of Lake Tanganyika, and 'Ctenochromis benthicola described from the same region, and some additional material led to the conclusion that the two species were conspecifics. Consequently, T. schreyeni is considered to be a junior synonym of 'C.' benthicola, an endemic species to the lake. A redescription of'C.' henthicola is also given. A statistical test comparing a single specimen and several specimens is difficult to carry out, because no variation is known in T. schreyeni. The present study, therefore, calculated Mahalanobis' distance between the holotype of T. schreyeni and specimens of 'C.' benthicola, and applied the Χ 2 test.

Neolamprologus cancellatus, a new cichlid species, is described on the basis of eight specimens from the Zambian coast of Lake Tanganyika. The new species is characterized by a subtruncate caudal fin and a body that is slender (depth 22.3–25.2% in standard length) and easily distinguishable from its congeners by having 7–8 anal fin spines, 34–37 scales in longitudinal line, 33 total vertebrae, and a gridlike body pattern on a pale brownish body color. This species is only known to inhabit the shallow (2–7 m depth), rocky bottom of Wonzye Point in the southern part of the lake.

The phylogenetic relationships among two Paracyprichromis and five Cyprichromis species, included in the Tanganyikan cichlid tribe Cyprichromini, were investigated using morphological features. The previously proposed diagnostic characters of Paracyprichromis are not synapomorphies, because the nonelongated swim bladder is plesiomorphic, the numbers of dorsal and anal fin rays and scales on longitudinal line and around the caudal peduncle overlap with those of Cyprichromis, and these counts and number of vertebrae are all included within the ranges of other Tanganyikan cichlids. The monophyly of Paracyprichromis is supported by a unique condition of infraorbitals to this genus. Additionally, the monophyly of Cyprichromis was reconfirmed by one of the previously proposed diagnostic characters, the presence of an elongated swim bladder.

A second species of Cyphotilapia (Cichlidae) is described from Lake Tanganyika. The new species is clearly distinct from Cyphotilapia frontosa in having three scale rows between the upper and lower lateral lines at center of body (vs two rows in C. frontosa). Furthermore, a greater number of scales on the longitudinal line (34–36 vs 33–35), fewer outer teeth on the upper jaw (31–52 vs 39–62), higher body (43.3–51.2% SL vs 38.2–46.5%), longer predorsal (37.5–44.9% SL vs 37.1–42.7% SL), longer dorsal-fin base (57.1–64.6% SL vs 53.8–60.9% SL) and longer pectoral fin (36.0–47.2% SL vs 31.3–41.7%) also distinguish the former species. The distribution of the new species is restricted to the southern half of Lake Tanganyika, whereas C. frontosa is allopatrically distributed in the northern half of the lake.

The relationships among 53 genera of Tanganyikan cichlid fishes were analyzed based on internal and external morphological features. Comparison of the morphological cladistic tree with a previously proposed classification showed 5 of 12 tribes to be nonmonophyletic. Sixteen tribes were recognized, the changes in classification being that Trematocarini was treated as a junior synonym of Bathybatini; 5 new tribes were established for each of the following genera, Benthochromis, Boulengerochromis, “Ctenochromis” benthicola, Cyphotilapia, and Greenwoodochromis; “Ctenochromis” horei was transferred from Haplochromini to Tropheini; and “Gnathochromis” pfefferi was transferred from Limnochromini to Tropheini. The revised classification was supported by previously proposed molecular trees.

The phylogenetic relationships among 13 species of the Tanganyikan cichlid genus Xenotilapia and 12 related genera were investigated based on internal and external morphological features. Xenotilapia is paraphyletic unless Asprotilapia, Enantiopus, and Microdontochromis are treated as junior synonyms. The expanded Xenotilapia is characterized by four infraorbitals, in which the anteriormost bone bears four or five sensory pores and does not overlap the elongated second bone.

Cyprichromis zonatus, a new cichlid species, is described on the basis of 21 specimens from the Zambian coast of Lake Tanganyika. It differs from its congeners, Cyprichromis leptosoma, Cyprichromis microlepidotus, and Cyprichromis pavo, by having 39–43 scales in longitudinal line (vs 57–71 in C. microlepidotus), 29–36 upper lateral line scales (vs 49–60 in C. microlepidotus), usually 14 or 15 dorsal fin spines (vs 12 or 13 in C. leptosoma, usually 16 in C. pavo), a generally deeper body (24.5–30.3% SL vs 23.1–26.2% in C. microlepidotus, 24.5–26.4% in C. pavo), deeper caudal peduncle (9.9–11.1% SL vs 8.4–9.9% in C. microlepidotus, 9.3–9.9% in C. pavo), longer pectoral fin (27.1–33.0% SL vs 23.1–27.4% in C. leptosoma, 23.0–27.3% in C. microlepidotus), caudal fin dichromatism absent (vs blue and yellow dichromatism in male C. leptosoma), and three or four distinct vertical bands beneath the dorsal fin base in live males (vs absent or very indistinct in other species).

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.

The external morphology, osteology, and myology of the African fluvial genus Teleogramma are described, and its familial allocation is discussed. Teleogramma is included in the family Cichlidae by loss of a major structural association between adductor mandibulae sections 2 and w, and by having an insertion of a large ventral division of adductor mandibulae section 2 onto the anguloarticular, expanded head of the fourth epibranchial, transversus dorsalis subdivided into four parts, functionally decoupled premaxillae and maxillae, the stomach's extendible blind pouch, the left-hand exit to the anterior intestine, the first intestinal loop at the left side, two epurals, seven branched rays on each upper and lower caudal fin lobe, free first uroneural from a united element of first preural and ural vertebra, and third preural vertebra fused with its haemal spine. Seven synapomorphies supporting the monophyly of Teleogramma are indicated, including the absence of or very low supraoccipital crest, the presence of a nostril tube, nonextended supraoccipital anteriorly, absence of extensive cartilaginous cap on the anterior border of the second epibranchial, presence of a beaklike projection on the cleithrum, caudal branched slip of epaxialis that inserts onto the upper two or three branched rays on the upper lobe of the caudal fin, and flexor dorsalis superior, which inserts onto the lower four unbranched rays on the upper lobe of the caudal fin.

A focus on pair bonds between males and females is fundamental to study the evolution of social organization. Because pair bonds are generally identified from direct observations of pairs that maintain physical proximity, pair bonds may have been overlooked in animals that do not exhibit such visible pairs. The Lake Tanganyika cichlid fish Xenotilapia rotundiventralis forms schools that consist of mouthbrooding and non-brooding adults in mid-water, and visible pairs are not recognized. A previous study suggested that mouthbrooding females transfer fractions of the young to males when the young become large. However, it remains a mystery whether the mating pairs maintain pair bonds so that the females can transfer the young to their mates. To answer this question, we conducted a parentage analysis using 10 microsatellite markers. The analysis showed that the mouthbrooding adults were most likely genetic fathers and mothers of the young in their mouths. This finding suggests that the female-to-male shift of young takes place between mating partners, and thus the mating pairs maintain pair bonds at least until the shift of young. The present study is the first to detect pair bonds in animals in which physical proximity has not been observed., 分子で発見した夫婦の「絆」～ある熱帯魚でのはなし. 京都大学プレスリリース. 2011-11-23.

Restriction site-associated DNA (RAD) sequences from entire genomes can be used to resolve complex phylogenetic problems. However, the processed data matrix varies depending on the strategies used to determine orthologous loci and to filter loci according to the number of taxa with sequence data for the loci, and often contains plenty of missing data. To explore the utility of RAD sequences for elucidating the phylogenetics of variously related species, we conducted RAD sequencing for the Ohomopterus ground beetles and attempted maximum-likelihood phylogenetic analyses using 42 data matrices ranging from 1.6 × 104 to 8.1 × 106 base pairs, with 11–72% missing data. We demonstrate that robust phylogenetic trees, in terms of bootstrap values, do not necessarily result from larger data matrices, as previously suggested. Robust trees for distantly related and closely related taxa resulted from different data matrices, and topologically different robust trees for distantly related taxa resulted from various data matrices. For closely related taxa, moderately large data matrices strongly supported a topology that is incompatible with morphological evidence, possibly due to the effect of introgressive hybridization. Practically, exploring variously prepared data matrices is an effective way to propose important alternative phylogenetic hypotheses for this study group.

Theoretically, competition can initiate divergence in habitat use between individuals of a species, leading to restricted gene flow and eventual speciation. Evidence that sister species differ in habitat use is commonplace and consistent with this mechanism, but empirical experimental support is surprisingly scarce. Here we provide evidence that competition has taken a key role in the evolution of genetically distinct ecomorphs of the Lake Tanganyika cichlid fish Telmatochromis temporalis. Experiments show that differences in substrate use between a large-bodied rock-living ecomorph and a neighbouring small-bodied shell-living ecomorph are mediated by size-dependent competition that drives assortative mate-pair formation. Specifically, adults of the larger ecomorph outcompete adults of the smaller ecomorph on favoured rock substrate, compelling the smaller adults to use shell habitat. These results support a role for competition in maintaining reproductive isolation, and highlight the need to identify ecological processes that impose selection to improve our understanding of speciation and adaptive radiation.

Two cichlid fishes from Lake Tanganyika,Xenotilapia sima Boulenger, 1899 andX. boulengeri (Poll, 1942) are often confused owing to insufficient information on the diagnostic morphological characters for each species. Morphological and morphometric analyses showed thatX. sima differs fromX. boulengeri in having a greater number of teeth and anal and pectoral fin soft rays, thicker caudal peduncle, larger eyes, and a shorter snout and anal fin base.

Microdontochromis rotundiventralis, a new species of cichlid fish, is described on the basis of 13 specimens from Nkumbula Island, Lake Tanganyika (Zambia). It is distinct from its only congener,M. tenuidentatus, in having two (rarely one) rows of teeth on both jaws, a rounded distal margin on the pelvic fin, the outermost pelvic fin soft ray length 1.23–1.43 times the innermost ray, a deeper body (depth 26.8–29.1% standard length) and the anal fin with 9 (rarely 8 or 10) soft rays.

Phenotypic polymorphisms can be applied to study the micro-evolutionary forces that maintain genetic variation and can mediate speciation, but it can be difficult to determine the genetic basis of polymorphisms. Recently, restriction-site-associated DNA (RAD) sequencing has become popular, which can easily produce multiple single nucleotide polymorphisms from whole genomes. Here, we combined RAD sequencing, allele-specific PCR and Sanger sequencing to determine the genetic basis underlying male colour dimorphism of a Lake Tanganyika cichlid fish, Cyprichromis leptosoma. Our analyses using both a cross-family (two parents and 12 F2 males) and 64 wild individuals do not contradict a hypothesis that two alleles of one-locus control male colour dimorphism. Also, the locus may be located on a genome region that experiences reduced levels of recombination. Although more analyses will be needed to conclude these findings, this study is the first to suggest the genetic basis of a colour polymorphism using RAD sequencing.

The cichlid fish, Astatotilapia burtoni, can acclimate and reproduce in both the K(+)-, Na(+)-, and Ca(2+)-rich waters of Lake Tanganyika (pH 8.9-9.2) and the surrounding rivers where K(+), Na(+), and Ca(2+) concentrations are low (pH 6.5). In this study, we compared sperm motility features among A. burtoni inhabiting the lake, those living in the surrounding rivers, and those from rivers that acclimates to lake water. Sperm of all three groups required extracellular Ca(2+) ([Ca(2+)]o) for sperm motility activation. However, involvement of K(+) and Na(+) were different. In sperm motility initiation of lake population, the decrease in Na(+) and increase in K(+) concentrations corresponding to a decrease in [Na(+)]o/[K(+)]o was required. In contrast, sperm motility in both the river population and those acclimated to lake water were activated only by a decrease in [Na(+)]o, suggesting that motility initiation cues regarding Na(+) and K(+) are different among populations within same species. One probable reason why the difference of initiation cues is that the concentration of K(+) in the river water (40 mM) is lower than that in the lake water (110 mM). These results suggest that sperm flagellar activation cascades of river and lake populations within this species differ as a result of adaptations to different ionic environments.