A phylogeny of fossil and living neocoleoid cephalopods

Coleoid cephalopod phylogeny is well studied via both molecular and morphological data, yet although some agreement has been reached (e.g. that extant Decapodiformes and Octopoda are monophyletic) many details remain poorly resolved. Fossil coleoids, for which much data exists, have hitherto not been incorporated into analyses. Their inclusion is highly desirable for the support of neontological phylogenies, to better reconstruct character-state histories, and to investigate the placement of the fossil groups themselves. In this study we present and analyse a morphological data matrix including both extinct and extant taxa. Homology assumptions in our data are discussed. Our results are presented both with and without the constraint of a monophyletic Decapodiformes imposed. When analysed with this constraint our results are strikingly congruent with those from molecular phylogeny, for instance placing Idiosepius in a basal position within Decapodiformes, and recovering Oegopsida and Bathyteuthoidea (although as grades). Our results support an Octopodiformes clade (“vampire squid” Vampyroteuthis as sister to Octopoda) and an octopodiform interpretation for most fossil coleoids. They suggest the fossil sister taxon to the octopods to be Plesioteuthididae. Most fossil higher taxa are supported, although many genera, especially within suborder Teudopseina, appear para- or polyphyletic.Preprint5,250

Actin Gene Family Evolution and the Phylogeny of Coleoid Cephalopods (Mollusca: Cephalopoda)

Phylogenetic analysis conducted on a 784-bp fragment of 82 actin gene sequences of 44 coleoid cephalopod taxa, along with results obtained from genomic Southern blot analysis, confirmed the presence of at least three distinct actin loci in coleoids. Actin isoforms were characteri zed through phylogenetic analysis of representative cephalopod sequences from each of the three isoforms, along with translated actin cDNA sequences from a diverse array of metazoan taxa downloaded from GenBank. One of the three isoforms found in cephalopods was closely related to actin sequences expressed in the muscular tissues of other molluscs. A second isoform was most similar to cytoplasmic-specific actin amino acid sequences. The muscle type actins of molluscs were found to be distinct from those of arthropods, suggesting at least two independent derivations of muscle actins in the protostome lineage, although statistical support for this conclusion was lacking. Parsimony and maximum-likelihood analyses of two of the isoforms from which \u3e30 orthologous coleoid sequences had been obtained (one of the cytoplasmic actins and the muscle actin) supported the monophyly of several higher-level coleoid taxa. These included the superorders Octopodiformes and Decapodiformes, the order Octopoda, the octopod suborder Incirrata, and the teuthoid suborder Myopsida. The monophyly of several taxonomic groups within the Decapodiformes was not supported, including the orders Teuthoidea and Sepioidea and the teuthoid suborder Oegopsida. Parametric bootstrap analysis conducted on the simulated cytoplasmic actin data set provided statistical support to reject the monophyly of the Sepioidea. Although parametric bootstrap analysis of the muscle actin isoform did not reject sepioid monophyly at the 5% level, the results (rejection at P = 0.068) were certainly suggestive of sepioid nonmonophyly

The evolution of coleoid cephalopods and their present biodiversity and ecology

The present status of phylogeny and classification in coleoid cephalopods and the effect of evolution on the present ecology and biodiversity in the group are examined. The basis of knowledge of cephalopod phylogenywas formulated by Naef in the early 1920s, and his ideas and the progress made in the intervening 75 years are investigated. In the process, the roles that transitions between pelagic and benthic habitats played in the evolution of cephalopods are noted, and the possibility is advanced that the most recent “oceanic anoxic event” may have established a time marker for the divergence of some oegopsid families. The major advances since Naef’s work are: 1. The unusual nature of Vampyroteuthis has been recognized; 2. The sister-group relationship between the Neocoleoidea and the Belemnoidea has been established, but requires further confirmation;3. Monophyly has been confirmed for the Decapodiformes (new name), Octopodiformes and Octopoda by molecular and morphological methodologies; 4. The dates of origin of the Belemnoidea, Neocoleoidea, Sepioidea and fossil teuthoids have been extended to considerably earlier times. The major unsolved phylogenetic problems in need of immediate attention are the position of the Myopsida, relationships within the Sepioidea, the identification of the basal nodes within the Oegopsida, and the relationships of most “fossil teuthoids.

The phylogeny of coleoid cephalopods inferred from molecular evolutionary analyses of the cytochrome c oxidase I, muscle actin, and cytoplasmic actin genes

Although the fossil record of early cephalopods is rich and demonstrates the dominance of the group in Paleozoic times, the mainly soft-bodied coleoids (Cephalopoda: Coleoidea) are poorly represented. Therefore, little is known of the evolutionary history of coleoids through paleontology and current classifications of the subclass are based primarily on the morphology of extant representatives. A molecular phylogenetic analysis of the Coleoidea was therefore warranted. Phylogenetic relationships within the Coleoidea were constructed using molecular sequence data from one mitochondrial and two nuclear genes: cytochrome c oxidase I (COI) and two unlinked actin genes (Actin I and Actin II, respectively). A 657 base-pair portion of the COI gene was examined for 55 coleoid taxa encompassing a broad spectrum of diversity in the subclass. The COI gene exhibited the most rapid evolutionary rate among the three genes examined. Eighty-two sequences from a 784 base-pair portion of three paralogous actin genes were obtained from 44 terminal taxa. The Actin I gene was highly conserved and provided information for determining deep-level relationships. The Actin II gene was intermediately conserved and exhibited a broad range of sequence divergence than the COI and Actin I genes. The evolution of the actin gene family in cephalopods was compared to that in other molluscs, protostomes, and deuterostomes. Analyses of actin gene family evolution provided evidence that the Actin I gene encodes a muscle-type of actin, and that the Actin II gene encodes a cytoplasmic actin. These analyses also supported at least two independent derivations of muscle-type actins during the evolution of the protostome lineage. The following conclusions were drawn from the results of phylogenetic analyses: (1) the cephalopod subclass Coleoidea is monophyletic; (2) the order Octopoda is monophyletic and is sister group to the monotypic order Vampyromorpha; (3) the Decapodiformes, consisting of the orders Teuthoidea and Sepioidea, is monophyletic; (4) the orders Teuthoidea and Sepioidea are polyphyletic; (5) the teuthoid suborders Myopsida and Oegopsida are monophyletic and polyphyletic, respectively; (6) the Myopsida and the oegopsid families Chtenopterygidae and Bathyteuthidae are more closely related to the sepioid families Spirulidae, Sepiidae, and Sepiolidae, than they are to other teuthoid groups

Cephalopod classification and taxonomy

Chambered nautilus, cuttlefishes, squids and octopus are the four major groups of cephalopods, which belong to the highly evolved class of phylum Mollusca. Cephalopods are the third largest molluscan class after bivalves and gastropods and consist of more than 800 species (Lindgren et al. 2004). The fossil record contains about 17,000 named species of cephalopods. Although the diversity of cephalopods is very much reduced in the modern era, cephalopods are found to occur in all the oceans of the world from the tropics to the polar seas and at all depths ranging from the surface to below 5000m. Cephalopods were dominant predators millions of years before fish appeared. The earliest cephalopods were primitive shelled nautiloids which evolved in the Late Cambrian period. The living cephalopods range in size from 25mm (Southern pygmy squid, Idiosepius notoides) to more than 12m (Colossal squid, Mesonychoteuthis hamiltoni) in length

Comparative Analysis of Chromosome Counts Infers Three Paleopolyploidies in the Mollusca

The study of paleopolyploidies requires the comparison of multiple whole genome sequences. If the branches of a phylogeny on which a whole-genome duplication (WGD) occurred could be identified before genome sequencing, taxa could be selected that provided a better assessment of that genome duplication. Here, we describe a likelihood model in which the number of chromosomes in a genome evolves according to a Markov process with one rate of chromosome duplication and loss that is proportional to the number of chromosomes in the genome and another stochastic rate at which every chromosome in the genome could duplicate in a single event. We compare the maximum likelihoods of a model in which the genome duplication rate varies to one in which it is fixed at zero using the Akaike information criterion, to determine if a model with WGDs is a good fit for the data. Once it has been determined that the data does fit the WGD model, we infer the phylogenetic position of paleopolyploidies by calculating the posterior probability that a WGD occurred on each branch of the taxon tree. Here, we apply this model to a molluscan tree represented by 124 taxa and infer three putative WGD events. In the Gastropoda, we identify a single branch within the Hypsogastropoda and one of two branches at the base of the Stylommatophora. We also identify one or two branches near the base of the Cephalopoda

O enigma da "reação espermatofórica": breve síntese do conhecimento sobre a estrutura e o funcionamento dos espermatóforos dos cefalópodes (Mollusca: Cephalopoda)

Cefalópodes coleóides (lulas, sépias e polvos) produzem espermatóforos muito complexos que são transferidos à fêmea durante a cópula por meio do hectocótilo, um apêndice modificado nos machos. Durante a transferência à fêmea, ocorre a chamada "reação espermatofórica", complexo processo de evaginação do aparato ejaculatório do espermatóforo, que conduz à exteriorização da massa espermática e corpo cimentante. A presente revisão sintetiza o conhecimento acerca da morfologia e funcionamento desta estrutura exclusiva dos coleóides, identificando lacunas e definindo estratégias que possibilitem avanços na área. Poucos trabalhos abordam com detalhes a morfologia e anatomia funcional dos espermatóforos dos cefalópodes, grande parte do conhecimento acerca da estrutura do espermatóforo tendo sido gerada por trabalhos clássicos do século XIX e início do século XX. Investigações acerca do funcionamento dos espermatóforos são consideravelmente mais raras, estando o conhecimento básico sobre a reação espermatofórica restrito a apenas 19 espécies de coleóides. A revisão da literatura especializada permite sugerir que existem dois tipos básicos de fixação de espermatóforos em Decapodiformes (lulas e sepióides): fixação superficial e implante profundo (ou intra-dérmico). Na fixação superficial, comum em diversas espécies (e.g., Loliginidae, Sepiidae, Ommastrephidae), a base dos espermatângios é aderida ao tecido-alvo aparentemente por meio do corpo cimentante, a partir de substâncias adesivas e, em alguns casos, estruturas de fixação. No implante profundo, comum em alguns grupos de lulas oceânicas e de águas profundas (e.g., Architeuthidae, Cranchiidae, Octopoteuthidae, Sepiolidae), os espermatóforos implantam-se inteiramente no corpo da fêmea, de forma autônoma. Permanece desconhecido o mecanismo responsável pelo implante profundo. Em Octopodiformes (polvos), o espermatóforo é inserido no gonoduto feminino, alcançando a glândula oviducal, onde estão localizadas as espermatecas, ou a cavidade do ovário. Como o funcionamento extracorpóreo dos espermatóforos depende exclusivamente da intrincada estrutura e organização de seus componentes (e.g., membranas e túnicas), somente investigações detalhadas dessas estruturas proverão as bases para a compreensão do funcionamento e da exata função do complexo espermatóforo dos coleóides. Recomenda-se o desenvolvimento de um protocolo simples e eficiente para coloração e preparação total de espermatóforos, de forma que seja possível expandir as descrições morfológicas do espermatóforo em estudos taxonômicos e anatômicos, permitindo, portanto, ampliação do conhecimento acerca desta enigmática estrutura.Coleoid cephalopods (squids, cuttlefishes, and octopods) produce elaborate spermatophores, which are transferred to the female during mating with the aid of a modified appendage called hectocotylus. During transfer, the spermatophores undergo the so-called spermatophoric reaction, i.e., a complex process of evagination of the ejaculatory apparatus that, ultimately, leads to the extrusion of the cement body and sperm mass. The present review summarizes the bulk of our knowledge on the morphology and functioning of this exclusive coleoid character, identifying gaps and defining strategies to stimulate advancements in this area. Few detailed morphological studies regarding this structure have yet been conducted, and much of the knowledge on the coleoid spermatophore was generated by classical studies of the 19th and early 20th centuries. Furthermore, investigations on the functioning of this structure are even rarer, the basic knowledge of the spermatophoric reaction being restricted to 19 species. There seems to be a consensus in the literature that two types of attachment of spermatophores occur in decapodiforms (i.e., squids and sepioids): superficial attachment, and deep (or intradermal) implantation. In superficial attachment, the base of the spermatangia ends up attached on the surface of the female's body, by means of the adhesive contents and, in some cases, attachment structures of the cement body; this type is found in several groups of decapodiforms (e.g., Loliginidae, Ommastrephidae, Sepiidae). In deep implantation, the spermatangia penetrate autonomously the integument, embedding themselves completely into the female tissue; this strategy is common to some oceanic and deep-sea species (e.g., Architeuthidae, Cranchiidae, Octopoteuthidae, Sepiolidae). The mechanism responsible for deep implantation remains unknown. In octopodiforms (octopods), the spermatophore is inserted inside the lumen of the female gonoduct, reaching the oviducal gland, where the spermathecae are located, or the ovarian cavity. Since the extracorporeal functioning of coleoid spermatophores must rely entirely on the intricate structure and organization of the tunics, membranes, and other structures composing the spermatophore, only detailed investigations of these components would provide the basis for comprehending its mechanics. This paper recommends the development of a specific, efficient protocol for whole-mount staining and permanent preparation of coleoid spermatophores, in order to enable expansion of spermatophore morphological descriptions in taxonomic and anatomical studies, and therefore enhance the knowledge of this unique, still enigmatic structure.IBUSP - Departamento de ZoologiaCAPES PROAP-200

Tactical tentacles: new insights on the processes of sexual selection among the Cephalopoda

The cephalopods (Mollusca: Cephalopoda) are an exceptional class among the invertebrates, characterised by the advanced development of their conditional learning abilities, long-term memories, capacity for rapid colour change and extremely adaptable hydrostatic skeletons. These traits enable cephalopods to occupy diverse marine ecological niches, become successful predators, employ sophisticated predator avoidance behaviours and have complex intraspecific interactions. Where studied, observations of cephalopod mating systems have revealed detailed insights to the life histories and behavioural ecologies of these animals. The reproductive biology of cephalopods is typified by high levels of both male and female promiscuity, alternative mating tactics, long-term sperm storage prior to spawning, and the capacity for intricate visual displays and/or use of a distinct sensory ecology. This review summarises the current understanding of cephalopod reproductive biology, and where investigated, how both pre-copulatory behaviours and post-copulatory fertilisation patterns can influence the processes of sexual selection. Overall, it is concluded that sperm competition and possibly cryptic female choice are likely to be critical determinants of which individuals' alleles get transferred to subsequent generations in cephalopod mating systems. Additionally, it is emphasised that the optimisation of offspring quality and/or fertilisation bias to genetically compatible males are necessary drivers for the proliferation of polyandry observed among cephalopods, and potential methods for testing these hypotheses are proposed within the conclusion of this review. Further gaps within the current knowledge of how sexual selection operates in this group are also highlighted, in the hopes of prompting new directions for research of the distinctive mating systems in this unique lineage