Colour variation is incongruent with mitochondrial lineages: cryptic speciation and subsequent diversification in a Gulf of California reef fish (Teleostei: Blennioidei)

The Gulf of California endemic reef fish, Acanthemblemaria crockeri (Blennioidei, Chaenopsidae), reportedly has two colour morphs, one with melanic lateral spots ('Gulf' morph) and one with orange spots ('Cape' morph). In this study, we recorded colour morph in both males and females and collected mitochondrial DNA sequence data for cytochrome c oxidase I (COI) and tRNA-Pro/D-loop of specimens from throughout the Gulf to explore the genetic basis of the colour morphs. Two highly divergent (HKY + I distance = 11.9% for COI), reciprocally monophyletic lineages were identified, consistent with the presence of two parapatric species. A 30-km gap between the distributions of mitochondrial lineages roughly corresponds to a hypothesized former seaway across the Baja California peninsula north of La Paz, although the estimated divergence time (1.84 million years ago) is more recent than the hypothetical seaway (3–4 million years ago). Surprisingly, the distribution of mitochondrial species is not congruent with the distribution of either male or female colour morphs. Our analysis also revealed significant population differentiation within both species and no shared haplotypes among populations. The northern Gulf species includes four populations (NB, CB, NM and CM) corresponding to northern and central Baja and northern and central mainland sites, while the Cape species includes two populations (SB and SM) corresponding to the Baja and mainland sides of the southern Gulf. The NB/CB division corresponds to a hypothesized Plio–Pleistocene mid-peninsular seaway. The level of genetic divergence documented in this lineage is extraordinary for a marine fish with a pelagic larval stage within a semi-enclosed basin.     

Nest-site size as a short-term constraint on the reproductive success of paternal fishes

Synopsis Because female signal blennies, Emblemaria hypacanthus (Pisces: Chaenopsidae), exhibited a preference for the larger of two males in laboratory mate-choice experiments, male reproductive success was predicted to be positively correlated with male size in field populations. This prediction was met at one field site, but not a second where shelter size, rather than male size, was the primary correlate of male reproductive success. This finding appeared to be the consequence of the relatively small size of shelters (vacant gastropod shells) at the second site. At this site, significantly more males had their shelters filled with eggs and variance in male reproductive success was lower than at the first site. Limited area for deposition of eggs is potentially an important constraint on the short-term reproductive success of paternal males of shelter- or crevice-spawning fishes.     

Morphology of the male reproductive system of, Coralliozetus angelica (Pisces, Blennioidei, Chaenopsidae)

The testis, the seminal vesicles and the spermatic duct of Coralliozetus angelica (Böhlke & Mead) are described. The testis and the seminal vesicles are not arranged in pairs but are single. The testis is situated on the left side of the animal and consists of chambers instead of tubules. The seminal vesicle on the right side is composed of two different types (seminal vesicle 1 and 2) which are not connected with each other     

Reconciling molecules and morphology: molecular systematics and biogeography of Neotropical blennies (Acanthemblemaria)

Neotropical reef fish communities are species-poor compared to those of the Indo-West Pacific. An exception to that pattern is the blenny clade Chaenopsidae, one of only three rocky and coral reef fish families largely endemic to the Neotropics. Within the chaenopsids, the genus Acanthemblemaria is the most species-rich and is characterized by elaborate spinous processes on the skull. Here we construct a species tree using five nuclear markers and compare the results to those from Bayesian and parsimony phylogenetic analyses of 60 morphological characters. The sequence-based species tree conflicted with the morphological phylogenies for Acanthemblemaria, primarily due to the convergence of a suite of characters describing the distribution of spines on the head. However, we were able to resolve some of these conflicts by performing phylogenetic analyses on suites of characters not associated with head spines. By using the species tree as a guide, we used a quantitative method to identify suites of correlated morphological characters that, together, produce the distinctive skull phenotypes found in these fishes. A time calibrated phylogeny with nearly complete taxon sampling provided divergence time estimates that recovered a mid-Miocene origin for the genus, with a temporally and geographically complex pattern of speciation both before and after the closure of the Isthmus of Panama. Some sister taxa are broadly sympatric, but many occur in allopatry. The ability to infer the geography of speciation in Acanthemblemaria is complicated by extinctions, incomplete knowledge of their present geographic ranges and by wide-spread taxa that likely represent cryptic species complexes.     

Water flow controls distribution and feeding behavior of two co-occurring coral reef fishes: I. Field measurements

The interaction of flowing water with reef topography creates a continuum of flow microhabitats that can alter species distributions directly via transport of organisms or propagules, or indirectly by modulating the availability of critical resources. To examine how water flow affects the distribution and feeding performance of two species of planktivorous tube blennies (Chaenopsidae), flow speed and turbulence were measured within the feeding areas of Acanthemblemaria spinosa and A. aspera at three sites within Glover’s Reef, Belize. Although co-occurring, A. spinosa occupies topographically high locations (e.g., upright coral skeletons) while A. aspera occupies topographically low shelters in the coral pavement. Boundary layer theory predicts that A. spinosa should experience higher flow (and a higher flux of planktonic food) relative to A. aspera; however, complex topography and oscillatory flow require that this prediction is tested directly in the field. Within each site, the flow experienced by A. spinosa was, indeed, faster and more turbulent than that experienced by A. aspera at site-specific intermediate wave heights. When waves were small, gentle velocity gradients produced similar flows for the two species. When waves were high, flow was uniformly fast through the water column due to thinning of the benthic boundary layer. Plankton availability was similar for the species, with the exception of a greater abundance of harpacticoid copepods at the shelters of A. aspera. Quantitative behavioral observations suggest that the foraging strategies employed by the two fishes exploit the prevailing hydrodynamic conditions. For example, A. spinosa, the stronger swimmer of the two, attacks nearly 100% of the time in the water column where it can exploit the higher flux of plankton associated with faster flows, while A. aspera attacks primarily toward the reef surface where currents are likely to be slower and it can exploit more abundant benthic prey. Communicated by Biology Editor Dr. Mark McCormick     

Trophic ecomorphology in eastern Pacific blennioid fishes: character transformation of oral jaws and associated change of their biological roles

Synopsis The ecomorphological relationships between the oral jaws and food spectra were highlighted in 34 species of Gulf of California blennioid fishes (5 Tripterygiidae, 13 Labrisomidae, 11 Chaenopsidae and 5 Blenniidae). Twenty-nine species are microcarnivorous, two are omnivorous browsers, two are algae grazers and one was an ‘ectoparasite’ feeder. The spectrum of oral (as opposed to pharyngeal) jaw (OJA) morphology ranges from plesiomorphic, suction-feeding (relatively large, protrusible jaws, with many coniform-caniniform teeth) to apomorphic, biting (relatively small, non protrusible jaws, with a single row of incisiform teeth). As species with similar morphology may widely differ in food, it is concluded, that morphology is not a reliable predictor for ecology in this case. With the exception of a few specialists, species with apomorphic, biting OJA utilize sessile items in addition to mobile categories and thus show a higher food diversity as compared to species with plesiomorphic OJA. Thus in the present case morphological differentiation goes along with ecological generalization. Only three blenniid species with the most apomorphic OJA may be considered as specialized also with regard to food resource utilization. Transformation of morphological characters and the ecological role of the OJA of blennioids may serve as a model to illustrate the steps required to achieve a biting-browsing and grazing feeding apparatus in many taxa of modern acanthopterygian reef fishes.