Microcotyle justinei n. sp. (Monogenea: Microcotylidae) from the Gills of the Cardinal Fish Apogon imberbis (Teleostei: Apogonidae) off the Algerian Coast of the Western Mediterranean

PURPOSE

A new monogenean Microcotyle justinei n. sp. (Monogenea: Microcotylidae) is described based on specimens found on the gill filaments of the cardinal fish Apogon imberbis (Apogonidae) off the Algerian coast of the Western Mediterranean.

METHODS

Monogeneans were examined, measured and drawn for a comparative morphological study with other species of Microcotyle and characterised molecularly using a partial fragment of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. The identification of fish was confirmed by molecular barcoding using the cox1 gene.

RESULTS

The new species is distinguished from all other species of the genus by a combination of features, such as the number and size of the clamps, the shape and size of the genital atrium and the number of testes. The molecular analysis of the cox1 gene sequences showed that interspecific differences between Microcotyle justinei n. sp. and published sequences of Microcotyle spp. was greater than 8.8%, strongly suggesting that the new species is distinct from other congeners with sequences available on GenBank.

CONCLUSION

The morphological and molecular analyses support the status of M. justinei as a new species. The present finding extends the list of Microcotyle spp. to 72.

Ocular pathology in aquarium fish with a focus on the Syngnathidae and Apogonidae families

This study catalogued ocular pathology in fish histopathology submissions to a specialist diagnostic service and investigated associations with species and systemic disease, with a focus on species of conservation interest. Cross-tabulations and Fisher's exact tests were used to identify associations among the variables and results are reported as prevalence ratios (PRs) with 95% confidence intervals (CI). Of 12,488 reports reviewed, ocular histology examination was available for 4,572 submissions, in which histopathological ocular lesions were identified in 18% (813/4572). Most diagnoses (701/813; 87%) were in marine fish. Inflammatory conditions were most common (608/813; 75%), with identification of a bacterial aetiology in 42% (255/608) and a parasitic aetiology in 30% (183/608). Most bacterial infections were due to mycobacteriosis (153/255; 60%) and most parasitic infections were due to scuticociliatosis (114/184; 62%). The Syngnathidae, Centriscidae and Cichlidae families were each more likely than all other families combined to be diagnosed with ocular manifestations of mycobacteriosis (PRs = 2.6, 4.4 and 2.9, respectively, P <0.0001 for each). The Syngnathidae were also more likely to be diagnosed with ocular scuticociliatosis (PR = 1.9, P <0.0001). Fifty-four percent (39/72) of ocular mycobacteriosis and 38% (9/24) of gas bubble disease cases affected threatened or near threatened Syngnathidae species. The Apogonidae were more likely than any other family to have ocular iridovirus (PR = 10.3, 95% CI = 5.5-19.4, P <0.0001) and neoplasia (PR = 8.2, 95% CI = 4.2-16.3, P <0.0001). The endangered Banggai cardinalfish (Pterapogon kauderni) accounted for 13/15 ocular iridovirus and 16/18 mycobacteriosis cases in this family. All cases of neoplasia in the Apogonidae occurred in pajama cardinalfish (Sphaeramia nematoptera). These results should inform clinical diagnosis of ocular disease in aquarium fish and influence training for aquarists, highlighting ocular pathology as a potential early warning of systemic disease. The findings also have direct/indirect consequences for the welfare and conservation of some of these popular flagship fish species.

Extra-pair mating in a socially monogamous and paternal mouth-brooding cardinalfish

Many vertebrates form monogamous pairs to mate and care for their offspring. However, genetic tools have increasingly shown that offspring often arise from matings outside of the monogamous pair bond. Social monogamy is relatively common in coral reef fishes, but there have been few studies that have confirmed monogamy or extra-pair reproduction, either for males or for females. Here, long-term observations and genetic tools were applied to examine the parentage of embryos in a paternally mouth-brooding cardinalfish, Sphaeramia nematoptera. Paternal care in fishes, such as mouth-brooding, is thought to be associated with a high degree of confidence in paternity. Two years of observations confirmed that S. nematoptera form long-term pair bonds within larger groups. However, genetic parentage revealed extra-pair mating by both sexes. Of 105 broods analysed from 64 males, 30.1% were mothered by a female that was not the partner and 11.5% of broods included eggs from two females. Despite the high paternal investment associated with mouth-brooding, 7.6% of broods were fertilized by two males. Extra-pair matings appeared to be opportunistic encounters with individuals from outside the immediate group. We argue that while pair formation contributes to group cohesion, both males and females can maximize lifetime reproductive success by taking advantage of extra-pair mating opportunities.

Cryptic lineages in the Wolf Cardinalfish living in sympatry on remote coral atolls

Coral reef health and biodiversity is under threat worldwide due to rapid climate change. However, much of the inter- and intra-specific diversity of coral reefs are undescribed even in well studied taxa such as fish. Delimiting previously unrecognised diversity is important for understanding the processes that generate and sustain biodiversity in coral reef ecosystems and informing strategies for their conservation and management. Many taxa that inhabit geographically isolated coral reefs rely on self-recruitment for population persistence, providing the opportunity for the evolution of unique genetic lineages through divergent selection and reproductive isolation. Many such lineages in corals and fish are morphologically similar or indistinguishable. Here, we report the discovery and characterisation of cryptic lineages of the Wolf Cardinalfish, Cheilodipterus artus, from the coral atolls of northwest Australia using multiple molecular markers from mitochondrial (CO1 and D-loop) and nuclear (microsatellites) DNA. Concordant results from all markers identified two highly divergent lineages that are morphologically cryptic and reproductively isolated. These lineages co-occurred at daytime resting sites, but the relative abundance of each lineage was strongly correlated with wave exposure. It appears, therefore, that fish from each lineage are better adapted to different microhabitats. Such cryptic and ecologically based diversity appears to be common in these atolls and may well aid resilience of these systems. Our results also highlight that underwater surveys based on visual identification clearly underestimate biodiversity, and that a taxonomic revision of the Cheilodipterus genus is necessary.

Homing is not for everyone: displaced cardinalfish find a new place to live

It was tested whether the pajama cardinalfish Sphaeramia nematoptera (Apogonidae) could home by displacing individuals up to 250 m within and among isolated reefs. Contrary to expectations, only two of 37 (5·4%) displaced S. nematoptera returned home and another 16 (43·2%) were found to have joined other social groups and did not home after 26 months of observations; while over the same period, 94% of control S. nematoptera remained associated with home corals, demonstrating strong site attachment. Hence, while this species has the potential to return home, being able to do so may not be as critical as previously assumed.