No abstract

No abstract

Sensory organs in Annelida are very diverse and may be useful for assessments of morphological adaptation and character evolution. We used several methods to provide new insights into processes underlying the evolutionary radiation of anterior sensory organs in Sabellariidae. The presence and morphological diversity of the median organ (MO) found in the group was reviewed in order to test its phylogenetic significance and possible relationships to the distribution and ecological traits of the lineages. To test the intraspecific phenotypic plasticity of the MO, molecular analyses were conducted that focused on mitochondrial and nuclear genes from populations of Idanthyrsus australiensis exhibiting variation in the morphology of the MO. We used an integrative microscopical study of the ontogeny of Sabellaria alveolata to describe the anterior sensory structures present in the larvae and the morphological changes occurring before, during, and after settlement. In larval stages, the palps and the dorsal hump (DH) exhibit distinct innervation. The larval DH organ, which is likely to play a major role in chemoreception for settlement, is interpreted as being the incipient form of the adult MO. These results suggest that annelid sensory organs including the MO may be useful for phylogenetic and developmental investigations.Additional key words: chemoreception, gregarious settlement, marine invertebrates, polychaetes, radiation of lineages Invertebrate Biology 135(4): 423-447.

No abstract

A new species of the Marphysa sanguinea group, M. iloiloensis n. sp. (Annelida: Eunicida: Eunicidae), is described from the Marine Annelids Hatchery of the Southeast Asian Fisheries Development Center, Aquaculture Department (SEAFDEC- AQD), Iloilo Province, Philippines. It represents the first record of this group in the Philippines. The new species is most similar morphologically to M. hongkongensa Wang, Zhang & Qiu, 2018, but can be distinguished from it by having fewer branchial filaments, a pair of faint eyes (absent in M. hongkongensa), and in slight differences in jaw morphology and chaetation. The embryos of the new species develop inside a jelly cocoon attached to the entrance of the adult burrow; this is the first time that egg-containing cocoons have been found in any species of the sanguinea-group. Phylogenetic analysis based on the mitochondrial gene cytochrome c oxidase subunit I (COI) revealed that Marphysa iloiloensis n. sp. is genetically distinct from all other analysed Marphysa species and forms a sister group to M. hongkongensa. A revised identification key to members of the sanguinea-group in Southeast Asia is provided.

A new Phyllodesmium species, P. jakobsenae nov. sp., is described from North Sulawesi, Indonesia. The new species is associated with the octocoral Xenia sp. Its external morphology is similar to other Phyllodesmium species inhabiting Xenia colonies, especially to P. hyalinum Ehrenberg, 1831, but cerata morphology and color, tooth and jaw morphology as well as the digestive glandular branching system within the cerata clearly distinguishes this new species. Behavioural notes are given and spawning is described. Active photosynthesis due to zooxanthellae (Dinophyceae of the genus Symbiodinium) in the digestive gland was measured in situ with a Diving-PAM (Pulse Amplitude Modulated Fluorometer). Experiments with P. jakobsenae indicate a symbiotic relationship with zooxanthellae at least for some days. These results are discussed in comparison to another Xenia inhabiting species, Phyllodesmium crypticum Rudman, 1981. Histological investigation of the digestive diverticula within the cerata of the new species also indicate a high effectiveness of the symbiosis.

No abstract

The Mediterranean fan worm,Sabella spallanzanii(Gmelin, 1791), is a highly invasive pest species introduced to Australia and New Zealand, with the ability to alter marine ecosystems by outcompeting native species for food and space.Sabella spallanzaniihas been established in southern Australia for decades, but was discovered in Botany Bay (NSW, eastern Australia) in 2013. In New Zealand,S. spallanzaniiwas first detected in March 2008. Using cytochrome c oxidase subunit 1 (COI) sequences, we investigate the phylogeography of the Australian and New Zealand populations ofS. spallanzanii, including the possible origins of the recent incursions in both countries. Australian and New ZealandS. spallanzaniishow minimal genetic diversity (0.2% divergence) and were dominated by two main haplotypes suggesting a commonality. Our molecular data are insufficient by themselves to identify fine-scale invasion pathways in antipodeanS. spallanzanii, but the similar, minimal haplotype diversity in combination with well-constrained field survey data suggests that the New Zealand incursion originated from southern Australia, rather than as a new incursion from the Mediterranean Sea. This highlights the importance of ongoing marine biosecurity surveillance and monitoring as well as improvements to biosecurity protocols for international and domestic vessels. The origin of the eastern Australian (Botany Bay) incursion is plausibly derived from either southern Australia or as a ‘return’ from New Zealand, and requires further, more detailed investigation.