Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 71-79). Also available via the World Wide Web.

Durante los años 1996 y 2003 el sistema marino costero se caracterizó por la ocurrencia de eventos importantes y extremos como El Niño 1997-1998(EN 1997-98) y La Niña 1999-2000(LN 1999-00), que unidos al sistema de afloramiento constituyen los principales factores determinantes de la variabilidad oceanográfica y condicionantes de la vida, en nuestro mar. En este marco de variabilidad local se realizó la investigación, referente al proceso de asentamiento larval del macrobentos marino, se trabajó con tres especies de la familia Mitylidae: Aulacomya ater, Semimytilus algosus y Brachidontes granulata, elegida por ser una familia representativa del subsistema bentónico costero. La investigación constó de dos etapas: la primera fue el seguimiento temporal de las densidades de asentamiento larval de cada especie; y la segunda en la relación del asentamiento con la variabilidad física local, empleando para esto sustrato artificial y ubicándonos en una estación fija dentro de Bahía Independencia, Pisco- Perú. De manera independiente se caracterizaron periodos significativos y se analizó el comportamiento biológico, y la variabilidad hidrográfica local junto a la disponibilidad de alimento fitoplanctónico, respectivo para cada periodo. Se pudo determinar al final, que la ocurrencia del evento El Niño 1997-98, alteró la estacionalidad, intensidad y frecuencia en los pulsos de asentamiento de las tres especies, mientras que en los años de ocurrencia del evento La Niña 1999-00 las densidades de asentamiento de Aulacomya ater y Semimytilus algosus, se mostraron muy similares entre sí, no encontrando en ninguno de los casos relación con la variabilidad física local. / --- During the period between 1996-2003, our coastal marine system was characterized for the ocurrence of the importants and extreme events as El Niño 1997-1998 (EN 1997-98) and La Niña 1999-2000 (LN 1999-00), that together with our upweling system, are the principal factors determining the oceanic variability, and conditions of life. Our investigations analyzed the larval settlement of the marine macro benthos about three specimens if the family Mytilidae: Aulacomya ater, Semimytilus algosus and Brachidontes granulata, were choose for do and representative family of the benthonic subsystems. This investigations have two parts, the first is the temporal following of the densities of settlement of three specimens of the mitylidae family, this family was chosen because is a good representantive of the benthic subsystems coast; and the second part is how the physics oceanographic local variability answer; employing artificial substrate in a marine station, into bahía Independencia, Pisco – Perú. In an independent way they were characterized significant periods and the biological behavior was analyzed, and the hydrographic local variability close to the food availability phytoplankton, respectively for every period. It was possible to determine ultimately that the occurrence of the event El Niño 1997-98, altered the seasionality, intensity and frequency in the pulses settlement of three species, whereas the years of occurrence of the event La Niña 1999-00 the densities of settlement of Aulacomya ater and Semimytilus algosus, proved to be very similar between yes, not finding in any of the cases relation with the physical local variability.

Durante los años 1996 y 2003 el sistema marino costero se caracterizó por la ocurrencia de eventos importantes y extremos como El Niño 1997-1998(EN 1997-98) y La Niña 1999-2000(LN 1999-00), que unidos al sistema de afloramiento constituyen los principales factores determinantes de la variabilidad oceanográfica y condicionantes de la vida, en nuestro mar. En este marco de variabilidad local se realizó la investigación, referente al proceso de asentamiento larval del macrobentos marino, se trabajó con tres especies de la familia Mitylidae: Aulacomya ater, Semimytilus algosus y Brachidontes granulata, elegida por ser una familia representativa del subsistema bentónico costero. La investigación constó de dos etapas: la primera fue el seguimiento temporal de las densidades de asentamiento larval de cada especie; y la segunda en la relación del asentamiento con la variabilidad física local, empleando para esto sustrato artificial y ubicándonos en una estación fija dentro de Bahía Independencia, Pisco- Perú. De manera independiente se caracterizaron periodos significativos y se analizó el comportamiento biológico, y la variabilidad hidrográfica local junto a la disponibilidad de alimento fitoplanctónico, respectivo para cada periodo. Se pudo determinar al final, que la ocurrencia del evento El Niño 1997-98, alteró la estacionalidad, intensidad y frecuencia en los pulsos de asentamiento de las tres especies, mientras que en los años de ocurrencia del evento La Niña 1999-00 las densidades de asentamiento de Aulacomya ater y Semimytilus algosus, se mostraron muy similares entre sí, no encontrando en ninguno de los casos relación con la variabilidad física local. / During the period between 1996-2003, our coastal marine system was characterized for the ocurrence of the importants and extreme events as El Niño 1997-1998 (EN 1997-98) and La Niña 1999-2000 (LN 1999-00), that together with our upweling system, are the principal factors determining the oceanic variability, and conditions of life. Our investigations analyzed the larval settlement of the marine macro benthos about three specimens if the family Mytilidae: Aulacomya ater, Semimytilus algosus and Brachidontes granulata, were choose for do and representative family of the benthonic subsystems. This investigations have two parts, the first is the temporal following of the densities of settlement of three specimens of the mitylidae family, this family was chosen because is a good representantive of the benthic subsystems coast; and the second part is how the physics oceanographic local variability answer; employing artificial substrate in a marine station, into bahía Independencia, Pisco – Perú. In an independent way they were characterized significant periods and the biological behavior was analyzed, and the hydrographic local variability close to the food availability phytoplankton, respectively for every period. It was possible to determine ultimately that the occurrence of the event El Niño 1997-98, altered the seasionality, intensity and frequency in the pulses settlement of three species, whereas the years of occurrence of the event La Niña 1999-00 the densities of settlement of Aulacomya ater and Semimytilus algosus, proved to be very similar between yes, not finding in any of the cases relation with the physical local variability.

Thesis (Ph. D.)--University of Southern California, 1977. / Bibliography: leaves 88-93.

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: [44]-53)

The Mediterranean mussel Mytilus galloprovincialis, was introduced accidentally to South Africa and has since become invasive. One possible explanation for the success of this species is that it has been released from the effects of parasites which affect the indigenous species of mussels. The aim of this work was to examine the parasitic load of different mussel populations along the southern African coast and to assess the effects of parasites on their hosts. A survey was done to quantify the levels of parasitism in indigenous populations of Perna perna from Southern Africa and of Mytilus galloprovincialis from South Africa (where it is exotic) and Spain (where it is indigenous). This survey was carried out at three different geographic scales: small scale (metres), studying the incidence of parasites within a mussel bed; medium scale (kilometres to tens of kilometres), comparing prevalences of infection among different localities; and large scale (hundreds to thousands of kilometres), examining infection rates along the Southern African coast, as well as the coast of the Basque Country (North Spain). During this survey metazoan parasites other than trematodes were rare. Four species of trematodes were commonly found infecting the indigenous mussel Perna perna. These were metacercariae of the genus Proctoeces, bucephalid sporocysts, encysted metacercariae on the labial palps and gelatinous cysts with metacercariae inside. A detailed description of Proctoeces is given; the other parasites are described elsewhere. No parasites were found in M. galloprovincialis either in South Africa or in Spain. This thesis concentrates on the study of prevalences of Proctoeces and bucephalid sporocysts and their effects on Perna perna. Infection rates with Proctoeces are highly dependent on the sex of the host, with more females than males being infected, and are also size dependent, though only for females. Identification of the sex of mussels infected with bucephalid sporocysts is often not possible since the sporocysts spread over the gonad and replace it. Prevalence of infection with this parasite also increases with the size of the host. To study the influence of Proctoeces and bucephalid sporocysts on the ecological fitness of Perna perna, their effects on survival and competitive ability were tested. The results showed significant negative effects. Both parasites significantly depressed condition but only after spawning, when the mussels were already stressed. In order to check for effects on host survival, the effects of both parasites on mortality rates, gaping behaviour and water loss of mussels exposed to air were also examined. Neither parasite affected mortality rate or gaping behaviour of Perna perna. Proctoeces did not affect the amount of water lost by mussels, but the bucephalid sporocysts did. Mussels infected with sporocysts lost significantly more water than non-infected individuals. This increase in water loss was not related to the gaping behaviour, but a test of the strength of the adductor muscles showed that less force was needed to open mussels with bucephalid sporocysts than non-infected mussels. This was not the case for mussels infected by Proctoeces. Weaker mussels will fail to seal the valves properly, resulting in an increase of water loss on exposure to air by evaporation. Another factor that will have an obvious effect on a population is the reproductive output of the animals. Histological sections of the gonad of infected and non-infected females were cut to study the effects of both parasites on reproduction. Statistical tests comparing the numbers and sizes of oocytes in females infected with Proctoeces and non-infected females showed no significant differences. However, bucephalid sporocysts have a dramatic effect on reproduction by castrating the host, leaving no trace of sex products. One of the major factors shaping the composition of a mussel bed is competition for space and food, with smaller mussels being at a competitive disadvantage. Thus, in order to examine effects of both parasites on the competitive ability of Perna perna, summer and winter growth rates were compared for infected and non-infected mussels. Proctoeces reduced growth both in summer and in winter whilst bucephalid sporocysts had no significant effect. Both growth and reproduction are important components of the energy budget of an animal, and each is affected by either Proctoeces or the bucephalid sporocysts. In an attempt to test if Perna perna compensates energetically for these negative effects, filtration rates and oxygen consumption of mussels with and without parasites were measured. Neither parasite had a significant effect on filtration rates or oxygen consumption of the host. All these results indicate that both Proctoeces and the bucephalid sporocysts have a detrimental effect on their host, and that the mussels do not compensate for these negative effects. There is neither an increase in filtration, nor a decrease in respiration to balance the energy lost to the parasite. The two parasites studied affect the host in different but complementary ways. The effects of both parasites are concentrated on those size classes of mussel which channel most energy into the portion of the energy budget affected by the parasite. Proctoeces affects growth only in the smaller individuals, which under normal conditions would put most energy into growth; and the bucephalid sporocysts castrate the bigger mussels, which would expend most energy on reproduction. By reducing growth rates of small mussels or castrating large mussels, these parasites effectively remove them from the breeding population and reduce their competitive abilities. These negative effects, together with the high prevalence of both parasites in Perna perna along the South African coast and their absence in Mytilus galloprovincialis, suggest that parasites may be an important reason for the success of Mytilus.

Orientador: Antonia Cecília Zacagnini Amaral / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-22T03:18:37Z (GMT). No. of bitstreams: 1 Silva_CamilaFernandada_M.pdf: 2054287 bytes, checksum: 3eb2bbba7d82fc1653b87868f315280a (MD5) Previous issue date: 2013 / Resumo: Os bancos de mitilídeos consistem de uma matriz física de indivíduos vivos e mortos e fragmentos de concha, interconectados por um emaranhado de filamentos do bisso. O estudo da caracterização estrutural de dois bancos de mitilídeos (Mytella charruana) foi realizado entre abril de 2006 e fevereiro de 2007, nas praias Camaroeiro e Cidade (costa norte do Estado de São Paulo). Amostras mensais foram obtidas com o auxílio de um delimitador de 0,04 m2 de área, até 20 cm de profundidade, em três níveis do banco (inferior médio e superior). Foi analisada a densidade de M. charruana, bem como os parâmetros perfil praial, salinidade da água intersticial, temperaturas do ar e do sedimento, conteúdo de calcário e matéria orgânica do sedimento e granulometria. A densidade média mensal de M. charruana do banco Camaroeiro variou de 13,66 inds/0,04 m2 (dp = 12,09) a 46 inds/0,04 m2 (dp = 11,53), e a do banco Cidade, de 57,33 inds/0,04 m2 (dp = 54) a 156 inds/0,04 m2 (dp = 43,31). O perfil da Praia do Camaroeiro permitiu classificá-la como dissipativa e, o da Cidade, como intermediária do tipo terraço de baixamar. A salinidade média da água intersticial do Camaroeiro variou de 26,33 (dp = 4,04) a 33,33 (dp = 1,15) e a da Cidade, de 27,5 (dp = 3,53) a 33,33 (dp = 1,15). A temperatura média do ar variou de 17ºC (dp =0) a 30,5ºC (dp =0) e a do sedimento, de 18ºC (dp =0) a 29ºC (dp = 0), em ambos os bancos. O conteúdo médio de calcário e matéria orgânica oscilou entre 6,73% (dp = 2,58) e 10,59% (dp = 1,53) e entre 2,17% (dp = 1,26) e 6,07% (dp = 2,07), respectivamente, no Camaroeiro e entre 8,39% (dp = 2,53) e 12,13% (dp = 1,91) e entre 3,56% (dp = 0,22) e 6,11% (dp = 0,48) na Cidade. A fração do sedimento predominante em ambos os bancos foi a de areia muito fina, com algumas variações ao longo do ano, e classificada principalmente como pobre a moderadamente selecionada. Ao final do período de estudo, os bancos de mitilídeos desapareceram, mas devem surgir novamente ao longo do tempo. Esse fato ocorre devido à dinâmica populacional e/ou reprodutiva de Mytella charruana, organismo estruturador dos bancos, e também à morfodinâmica praial dessa região / Abstract: Mussel beds are aggregations of live and dead mussels, shell fragments and byssus thread. The structural characterization of two soft-bottom mussel beds of Mytella charruana was studied between April 2006 and February 2007 at Camaroeiro and Cidade beaches (northern coast of São Paulo State). Mensal samples were taken with a 0,04 m2 corer, until a depth of 20 cm, in the lower, middle and upper levels of the beds and analyzed the density of M. charruana, beach slope, interstitial salinity, sediment and air temperatures, calcareous and organic matter content of the sediment and granulometry. The mean density of M. charruana ranged between 13,66 inds/0,04 m2 (sd = 12,09) and 46 inds/0,04 m2 (sd = 11,53) at Camaroeiro, and between 57,33 inds/0,04 m2 (sd = 54) and 156 inds/0,04 m2 (sd = 43,31) at Cidade. The Camaroeiro beach slope enabled the classification of the beach as a dissipative state while the Cidade beach slope, as a low-tide terrace. The mean Camaroeiro interstitial salinity ranged between 26,33 (sd = 4,04) and 33,33 (sd = 1,15); and the mean Cidade interstitial salinity ranged between 27,5 (sd = 3,53) and 33,33 (sd = 1,15). Mean air temperature ranged between 17ºC (sd = 0) and 30,5ºC (sd = 0) and mean sediment temperature, between 18ºC (sd = 0) and 29ºC (sd = 0), in both mussel beds. Mean calcareous and organic matter contents ranged, respectively, from 6,73% (sd = 2,58) to 10,59% (sd = 1,53) and from 2,17% (sd = 1,26) to 6,07% (sd = 2,07) at Camaroeiro and ranged, respectively, from 8,39% (sd = 2,53) to 12,13% (sd = 1,91) and from 3,56% (sd = 0,22) to 6,11% (sd = 0,48) at Cidade. The granulometric composition of both mussel beds was very similar, with a predominance of moderate and poorly-sorted fine sand. At the end of the study period, the mussel beds disappeared, but must appear again with time. This can happen due to the population and/or reproductive dynamic of Mytella charruana, the organism who structures the mussel beds, and also due to the beach morphodynamic of the area / Mestrado / Ecologia / Mestra em Ecologia

Orientador: Shirlei Maria Recco Pimentel / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-04T04:12:07Z (GMT). No. of bitstreams: 1 Introini_GiseleOrlandi_M.pdf: 3314388 bytes, checksum: bf79294ca706599f733d1e5bf15dca35 (MD5) Previous issue date: 2005 / Resumo: Numerosos estudos têm demonstrado a relevância da morfologia dos espermatozóides para determinação da filogenia no filo Mollusca. Adicionalmente, o estudo da morfologia e do número de cromossomos tem correspondido a uma eficiente ferramenta para a identificação de espécies, de híbridos e, menos usualmente, de populações. O presente trabalho analisou a ultra-estrutura dos espermatozóides de duas espécies do gênero Brachidontes e uma espécie do gênero Isognomon. As espécies B. darwinianus e I. bicolor foram também estudadas citogeneticamente. Moluscos pertencentes ao gênero Brachidontes vivem na zona entre marés de enseadas e baías e se fixam pelo bisso ao substrato rochoso, formando aglomerados de centenas de indivíduos. Brachidontes solisianus encontra-se distribuído da Costa Atlântica do México até o Uruguai e B. darwinianus é encontrado do Rio de Janeiro a Patagônia. Na costa do Estado de São Paulo, populações dessas duas espécies que exibem caracteres conquiológicos muito semelhantes, compartilham áreas em comum. A utilização da forma da concha como característica para separar mitilídeos é questionável, pois suas conchas, por possuírem grande plasticidade, podem apresentar variações morfológicas devido às influências ambientais. A espécie I. bico/ar é encontrada no litoral brasileiro com distribuição do Rio Grande do Norte até Santa Catarina. O extremo norte da distribuição da espécie é Bermudas, com ocorrência pelo litoral da Flórida, Golfo do México e Caribe. Acredita-se que I. bico/ar tenha sido sistematicamente, e de longa data, confundido com I. a/atus. A grande similaridade nas características externas da concha de I. a/atus e I. bico/ar, a variabilidade intra-específica na forma de ambas espécies, mais o fato de terem hábitos e habitats semelhantes, podem conduzir a equívocos de identificação. Os espécimes ocorrem desde o supralitoral até sete metros de profundidade no infralitoral. Os espermatozóides de B. darwinianus, B. solisianus e I. bic%r, como aqueles produzidos por muitas espécies de bivalves, apresentam uma morfologia típica de animais marinhos que lançam seus gametas fertilizando seus ovos na água do mar. Os gametas masculinos de B. darwinianus, de B. so/isianus e de /. bico/ar contém: acrossomo conspícuo (cônico e alongado em Brachidontes e arredondado em /sognomon); núcleo esferiforme condensado; um par de centríolos e 4-5 mitocôndrias situadas na peça intermediária e um axonema portador de 9 pares de microtúbulos ao redor de um par central. A estrutura geral do espermatozóide de Brachidontes é bastante semelhante a de outras espécies da mesma sub-família e parece agrupar esse gênero adequadamente na classificação atualmente aceita, ou seja, sub-família Modiolinae. A única característica que permite distinguir o espermatozóide destas duas espécies é o comprimento do acrossomo. A presença de um prolongamento acrossomal em B. solisianus pode significar um aumento da eficiência reprodutiva e deste modo contribuir para a maior distribuição geográfica desta espécie. Em relação a ultraestrutura do espermatozóide de /. bico/ar, estudos sobre a biologia da fertilização desta espécie são necessários para melhor compreender o significado biológico da presença de um filamento axial no espaço subacrossomal e de grânulos de glicogênio na peça intermediária. Considerando o fato de que esta espécie apresenta ampla distribuição geográfica e que tem se tomado uma espécie invasora em muitas regiões, especialmente no Brasil, seria interessante, verificar se estas características morfológicas do espermatozóide são capazes de proporcionar aumento na eficiência reprodutiva. A análise citogenética revelou a presença de 2n = 30 cromossomos para B. darwinianus e 2n = 28 cromossomos para J. bico/ar. Os resultados obtidos foram comparados com cariótipos de outros bivalves. Os números encontrados são comuns dentro da família Mytilidae e super-família Pteriacea, respectivamente, deste modo, estas espécies estão adequadamente classificadas, de acordo com os caracteres cromossômicos estudados / Abstract: Although bivalve species are well known anatomically, the taxonomic relationships among many of the species in this class are controversial. Numerous investigations have demonstrated the usefulness of sperm morphology in evaluating molluscan phylogeny. In this work, we used transmission and scanning electron microscopy to study the structure of mature spermatozoa from three bivalves, Brachidontes darwinianus, Brachidontes solisianus and Isognomon bicolor from the southeastern Brazilian coast, and compared them with those of other bivalves, particularly other members of the sub-class Pteriomorphia. The Giemsa-stained karyotypes of B. darwinianus and I. bicolor were also determined and compared with those of other bivalves. The genus Brachidontes has a wide geographic distribution and is particularly abundant in the intertidal zone of many rocky shores along the Brazilian coast, often in areas with strong water currents. Brachidontes darwinianus occurs from the state of Rio de Janeiro, Brazil, to Patagonia, in Argentina, whereas B- solisianus is distributed from Mexico to Uruguay. The spermatozoa of both species were of the primitive or ect-aquasperm type. In both species, the spermatozoan head contained a spheroidal nucleus capped by a conical acrosome with an anterior extension. No actin was detected in the subacrosomal region. However, immunocytochemical staining identified actin throughout the sperm nucleus of both species. The chromatin was highly electrondense, homogenous and compact, and the nuclei contained randomly distributed, electron-Iucent regions formed by invaginations of the nuclear envelope. These invaginations were detected by E-PT A staining for glycoproteins at low pH. The midpiece region consisted of five spherical mitochondria grouped in a ring around a pair of short cylindrical centrioles. The flagellum exhibited the typical 9+2 microtubule structure (nine double outer tubules + two single central tubules). The only marked difference in the morphology of spermatozoa from these two species was the longer anterior extension of the acrosomal vesicle in B. solisianus. This elongated acrosome may facilitate penetration of the jelly coat and cytoplasm of large oocytes and could increase the efficiency of fertilization. The resulting enhanced reproductive success could account for the wider geographic distribution of B. solisianus. Isognomon bicolor is distributed throughout many countries in the Americas. This species has an epifaunal existence and is usually found attached by its byssus to jetty pilings or growing in crevices on rocky shores exposed to strong water currents. The spermatozoa of this species were of the primitive or ectaquasperm type. The sperm head consisted of a round-to-oval, electron-dense nucleus (with an anterior fossa) capped by a small acrosome that contained an outer electron-dense and inner electron-Iucent region. The subacrosomal region had a thin filament that could play an important role in fertilization. Immunocytochemical analysis revealed the presence of actin throughout the nucleus of I. bicolor sperm, but no actin was detected in the subacrosomal area. Hence, the chemical nature of the amorphous material and of the tenuous filament present in the subacrosomal area remains unknown. The midpiece contained four ar five spherical mitochondria surrounding the centriole apparatus. Depasits of electron-dense granules, considered to be perimitochondrial glycogen, were observed around the centrioles and mitochondria. The flagellum had the typical 9+2 microtubular pattern. Ali of the B. darwinianus specimens studied had a diploid number of 2n=30 chromosomes whereas those of I. bico/ar had a diploid number af 2n=28. This chromosomal number is relatively common among closely related species of Brachidontes and Isognomon / Mestrado / Biologia Celular / Mestre em Biologia Celular e Estrutural

La familia Mytilidae Rafinesque, 1815, constituye un grupo de bivalvos que apareció en el Devónico y que incluye numerosos géneros y especies actuales. El registro de la familia es continuo, si bien aparecen en el mismo como abundantes solo a escala local. La familia está claramente delimitada, y se caracteriza por sus branquias de tipo filibranquias, su conchilla elongada, con umbones anteriores terminales o subterminales, sus músculos aductores notablemente desiguales, estando el anterior incluso ausente, y el desarrollo notable del biso, en relación a su modo de vida epibisado o endobisado. En rocas cenozoicas de Argentina aparecen con frecuencia representantes de esta familia, lo que se refleja en las numerosas menciones de la misma en la literatura. Sin embargo las referencias a material de mytílidos en la literatura es frecuentemente difícil de confirmar, ya que la identificación del mismo es incierta debido a que las conchillas de este grupo presentan un conjunto de caracteres relativamente poco informativos desde el punto de vista taxonómico. Además, son en general frágiles, por lo que su preservación muchas veces es deficiente. Adicionalmente, muchas veces los datos de procedencia exacta no están disponibles Es por ello que las referencias a material de mytilidos en la literatura es frecuentemente difícil de confirmar, ya que la identificación del mismo es incierta. Adicionalmente, muchas veces los datos de procedencia exacta no están disponibles. Siendo este grupo tan importante a lo largo de la costa atlántica actual y teniendo una potencial utilidad desde el punto de vista paleoecológico, ya que en general las especies que lo integran están ligadas a ambiente costeros, el conocimiento de la historia del mismo a lo largo del Cenozoico en esta región es indispensable para comprender los patrones de distribución actuales y la posible relación entre su distribución en el pasado y los eventos paleoceanogáficos que tuvieron lugar entonces. Es por ello que el objetivo general de esta tesis es contribuir al conocimiento de la historia de este grupo en el sur de América del Sur. Para ello se contó con material proveniente de las formaciones Roca (Daniano), Río Turbio (Eoceno), San Julián (Oligoceno), Monte León (Mioceno), Estancia 25 de Mayo (Mioceno) y Puerto Madryn (Mioceno). Este material había sido identificado previamente como alguno del total de 23 taxones de rango específico o subespecífico que habían sido descriptos previamente para estas unidades. Para ellos se habían utilizado los siguientes nombres: Mytilus trigonus Borchert, 1901; Mytilus wehrlii Ljungner, 1932; Mytilus brandmayri Feruglio, 1937; Aulacomya aff. A. atra (Molina ,1782); Brachidontes lepidus (Philippi, 1893); “Brachidontes magellanicus” Lam.; Brachidontes purpuratus (Lamarck, 1819); Brachidontes andinus (Ortmann, 1900); Crenella camaronesia Ihering, 1907; Gregariella amara Griffin, Parras y Casadío.,2008; Lithophaga exilis (Feruglio, 1935); Lithophaga platzi (Feruglio, 1935); Lithophaga cf. L. exilis (Feruglio, 1935); Lithophaga platensis (Philippi, 1893); Lithophaga dalli (Ihering, 1907); Modiolus ameghinoi (Ihering, 1897); Modiolus arctus (Feruglio, 1937); Modiolus aprilis (Feruglio, 1937); Modiolus cf. M. thomsoni Zinsmeister, 1984; Modiolus rionegrensis (Ihering, 1903); Modiomytilus argentinensis Griffin, 1990; Modiomytilus mercerati Griffin, 1990; Modiomytilus? pseudochorus (Doello-Jurado, 1922); Modiomytilus? hauthali (Ihering, 1907). Para cada uno de estos taxones se intentó identificar el material original y las localidades en donde hubiera sido registrado. Además, cuando fuera posible, se precisó la localidad tipo y la procedencia estratigráfica, coleccionándose material adicional en el campo. Como resultado, se describen 26 especies agrupadas en 9 géneros: Mytilus? wehrlii, Ljungner, 1932; Mytilus? brandmayri Feruglio, 1937; Aulacomya aff. A. atra (Molina ,1782); Aulacomya minuta n. sp.; Perna patagonica n. sp.; Perna sp.; Brachidontes cf. B. rodriguezii d'Orbigny, 1842; Crenella camaronesia Ihering, 1907; Gregariella amara Griffin, Parras y Casadío, 2008; Gregariella andina (Ortmann, 1900); Lithophaga cf. L. platensis (Philippi, 1893); Lithophaga exilis (Feruglio, 1935); Lithophaga cf. L. exilis (Feruglio, 1935); Lithophaga dalli (Ihering, 1907); Modiolus camachoi n. sp.; Modiolus bruneti n. sp.; Modiolus cf. M. platensis (Philippi, 1893); Modiolus ameghinoi Ihering, (1897); Modiolus arctus (Feruglio, 1937); Modiolus rionegrensis (Ihering, 1903); Modiolus cf. M. thomsoni Zinsmeister, 1984; Modiolus aprilis (Feruglio, 1937); Modiomytilus argentinensis Griffin, 1990; Modiomytilus mercerati Griffin, 1990; Modiomytilus? pseudochorus (Doello-Jurado, 1922) y Modiomytilus? hauthali (Ihering, 1907). Los patrones de distribución de los taxones descriptos reflejan las preferencias de este grupo por zonas costeras, ya sea de ambiente rocoso o de fondo blando en mares someros, muchas veces restringidos, tal como ocurre con los representantes actuales. Los géneros actualmente vivientes a lo largo de la costa ya se encontraban representados en las faunas cenozoicas (con excepción de Mytilus probablemente), si bien el establecimiento de los patrones de diversificación de los mismos y la exacta relación entre las especies fósiles y actuales es difícil de precisar por el momento.

The principal aim of this study was to establish the biological and environmental parameters governing the successful and sustainable cultivation of mussels in Saldanha Bay. The environmental study investigated seston, chlorophyll-a and particulate organic matter (POM) levels, water temperature dissolved oxygen and salinity levels in the bay and water flow in and around the rafts. The biological part of the study investigated the efficiency of food extraction, growth rates, mussel condition, fouling and production and yield on a rope, raft and farm scale. Saldanha Bay is well suited for the culture of mussels, particularly Mytilus galloprovincialis and Choromytilus meridionalis. Water temperature and salinity in Saldanha Bay were found to be near optimal for mussel culture. POM and chlorophyll-a levels were found to be high due to primary production resulting from the nutrient rich upwelled water outside Saldanha Bay. The mean levels of chlorophyll-a (8,6μg/l) represent 6%, by mass, of the total POM. On a bay scale the POM remained above the mussels maximum requirements (pseudofaeces threshold) during the study period. Mussels showed a preference for the phytoplankton portion of the POM. Approximately 40% of the chlorophyll-a was extracted from the water by the mussel farm. The efficiency of food extraction increased with mussel age. Rafts with seed mussels younger than 2 months, 3 to 4 months, 5 to 6 months and older than 6 months extracted 32%, 55%, 85% and 92% of the available chlorophyll-a respectively. An increase of rope spacing on the rafts resulted in 37% more chlorophyll-a and 30% more particle volume reaching the lee of the raft. Ambient water currents in the bay show flow rates of up to 22cm per second. However, on entering a raft with a rope spacing of 60cm, the water flow is attenuated by 90%. Increasing the rope spacing to 90cm resulted in a water flow attenuation of 72%. The increase in rope spacing ensures that the mussels in the centre of the raft are feeding on food levels close to, or above, the pseudofaeces level. Mussel growth rate at a rope spacing of 90cm is significantly improved as a result of the increased food delivery. There are other factors, however that effect mussel growth. Growth rates were found to be better in summer than in winter. The reduced winter growth rate is possibly due to competition with the maturing fouling organisms which settle in mid to late summer. Fouling by mussel spat and Ciona intestinalis is seasonal, occurring from December to May. C.intestinalis is prevalent in the centre of the farm and rafts as low energy waters are preferred by this species. Mussel spat settles mainly on the periphery of the farm and the rafts. Competition with fouling organisms reduces growth and increases mortality of the cultured mussels. Results indicate that the present spacing of rafts, (1 raft per hectare) is adequate under existing conditions. Any new farms should maintain batches of 50 rafts with channels between them to ensure water current penetration into the furthest reaches of the farm. Rope spacing on the rafts should be increased to between 60cm and 90cm. Mussel density should be regulated according to mussel size and fouling should be controlled to maintain yields.