Douglas G. Smith

The Rapid Colonization and Emerging Biology of Cordylophora caspia (Pallas, 1771) (Cnidaria: Clavidae) in the Connecticut River

ABSTRACT Five freshwater populations of the otherwise estuarine colonial hydrozoan Cordylophora caspia were observed in the Connecticut River, New England. Histological comparison of the body wall of the freshwater and estuarine populations revealed no differences in cell shape or size in the epidermis and gastrodermis, either of the undifferentiated body wall or in regions of tentacles. One freshwater population examined in 2000 had polyps that were shorter and wider than estuarine animals and contained much fewer and smaller sporosacs. All freshwater populations examined in 2001 had feeding polyp shape and size and sporosac size and number comparable to the estuarine population. We conclude that C. caspia has undergone physiological and ecological adjustments for existence in very soft water with low alkalinity. The species has in only a few years become abundant in certain areas of the Connecticut River and has acquired all the facies exhibited during experimentally determined optimal growth conditions. Ecologically, C. caspia is filling the niche of a benthic colonial predator; the hydroid preys on larval insects, predominately chironomids.

Autumnal reproduction in Cumberlandia monodonta (Unionoidea: Margaritiferidae)

Gill marsupia of Cumberlandia monodonta were observed to contain early developmental stages on 27 October 1982. This occurrence, in conjunction with histological examination of gonads from several specimens, documents the first record for autumnal reproductive behavior in C. monodonta, and lends credence to previous speculation that biannual periodicity occurs in this species. Smith (1976, 1978, 1988) systematically examined gametogenesis and reviewed brooding periodicity within the North American Margaritiferidae. However, information concerning margaritiferid reproductive biology remains sparse. Howard (1915) reported a single vernal brooding female of Cumberlandia monodonta (Say, 1829) and briefly described that individuals glochidia (also see Surber, 1915). These data are augmented by the discovery of an autumnal brooding female C. monodonta and histological examination of gonadal tissues from several preserved specimens collected at different localities. MATERIALS AND METHODS Several individuals of Cumberlandia monodonta (obtained from Meramec River, Times Beach access, 3 km east of Eureka, St. Louis County, Missouri, 27 October 1982) were maintained for several days in aquaria. During this period, one individual discharged large quantities of a mucus-like substance from its excurrent siphon. This material was collected immediately and examined microscopically. Forty additional specimens in collections of the University of Massachusetts at Amherst (UMA), Thomas M. Freitag (TMF), and one of the authors (MEG) were available for histological analysis of gonad activity (Table I). Mussels had been preserved either by fixation in 10% formalin, followed by 70% ethanol, or in alcohol without previous fixation. A portion of the viscera of each specimen was embedded in paraffin and sectioned at 8 ,m. Five sections from each specimen were hydrated to water, stained with Ehrlichs hematoxylin and eosin, dehydrated, and mounted. 1 The Tennessee Cooperative Fishery Research Unit is supported jointly by the U.S. Fish and Wildlife Service, Tennessee Wildlife Resources Agency, and Tennessee Technological University. Additional funding was provided by the Center for the Management, Utilization, and Protection of Water Resources, Tennessee Technological University. TRANS. AM. MICROSC. Soc., 109(4): 407-411. 1990. ? Copyright, 1990, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.189 on Fri, 09 Dec 2016 05:30:12 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC.

On the So‐called Mantle Muscle Scars on Shells of the Margaritiferidae (Mollusca, Pelecypoda), with Observations on Mantle‐Shell Attachment in the Unionoida and Trigonioida

Mantle attachment scars on the inner surface of shells of the Margaritiferidae have been traditionally regarded as sites of mantle muscle attachment; however, the actual occurrence of muscle tissue at points of attachment has never been verified. Mantle attachment scars occur on shells of seven examined species of margaritiferids. Gross and histological investigation of the mantle of five species reveals that mantle attachment involves modification of mantle epithelial cells and associated connective fibers within the mantle. The connective fibers within the mantle do not appear to have contractile properties, but along with the attachment cells probably provide support for the mantle. Mantle‐shell attachment scars similar to those of margaritiferids also occur in shells of recent trigonids, thus strengthening arguments for a phylogentic link between the Unionoida and Trigonioida.

GAMETOGENETIC CYCLE, REPRODUCTIVE ANATOMY, AND LARVAL MORPHOLOGY OF POPENAIAS POPEII (UNIONOIDA) FROM THE BLACK RIVER, NEW MEXICO

Abstract The freshwater unionoid mussel Popenaias popeii is restricted to river drainages of the Gulf of Mexico in southwestern North America. Previously, this species has been classified as both a short-term and long-term larval brooder based on limited data. Histological analysis of gonadal tissue from specimens collected in New Mexico indicated gonochoric individuals; hermaphroditism was not observed in any specimens. Although male and female gametes were present for almost the entire year, gonadal activity appeared lowest in October and November, when tissue recovery and reorganization were more evident than gametogenesis. Gravid females were observed from March through August, with all stages of embryos and larvae present on every sampling date during this period. Non-gravid females always were present, even if they contained active gonads. Contrary to previous reports, P. popeii is considered an asynchronous short-term brooder with an extended period (late winter to mid-summer) of oviposition. A small percentage of gravid females used posterior portions of inner demibranchs as marsupia. This character suggests that inner demibranchs might function in a facultative capacity as an overflow reservoir for larvae unable to fit into full marsupia of the specialized outer demibranchs.

The anatomy and brooding biology of Pottsiella erecta (Potts, 1884) (Ectoprocta: Gymnolaemata: Ctenostomata), with an expanded diagnosis of the Pottsiellidae

Pottsiella erecta (Potts, 1884) is a freshwater benthic colonial species of the Ectoprocta, Class Gymnolaemata. Despite a number of published observations on P. erecta, the species has remained poorly understood and its relationships to other freshwater gymnolaemates unclear. The present study provides anatomical and brooding characteristics pertinent to resolving the relationship of P. erecta with other freshwater gymnolaemates. Among several features, P. erecta contains a collar, lacks any manifestation of the wall of the cardia, has a continuous funiculus, a simple communication plate, lacks a dorso-ventral muscle, and is an external brooder. The combination of characters precludes placing P. erecta with any freshwater or marine group and the monotypic family Pottsiellidae is reinstated for this species. An expanded diagnosis of the Pottsiellidae is provided.

Life in Crumbling Clay: The Biology of Axarus Species (Diptera: Chironomidae) in the Connecticut River

Abstract Larval midges in the genus Axarus are common macroinvertebrates in areas of the Connecticut River where varved clay substrates are found. Using SCUBA to make collections, we investigated the habitat use, species composition, and life history of the two Axarus species found in the river. Larvae were only found in clay or decaying wood, with a population density of 13,345 (± 4881) larvae/meter2 at one site. Two species were found co-existing in clays in northern sites, while only one species was found in southern collections. The species are temporally isolated, with adult emergence for the southern species preceding that of the northern species. Life history data are presented for the southern species, an undescribed taxon designated Axarus species varvestris. This species is univoltine with adult emergence taking place in late June in southern locations. The sex ratio at emergence was 1:1, and protandry was evident.

THE DISCOVERY OF CAENESTHERIELLA GYNECIA Mattox 1950 (BRANCHIOPODA, CYZICIDAE) IN NEW ENGLAND, WITH ECOLOGICAL AND SYSTEMATIC NOTES

Abstract Caenestheriella gynecia, a poorly known species of the clam shrimp family Cyzicidae, is reported from New England for the first time. Two populations were monitored, along with water chemistry and vegetation features, in wooded ephemeral pools along abandoned roads in Berkshire County, Massachusetts from August through September, 2000. All animals collected alive and over 6 mm in length contained eggs. No male features were detected in any specimens. Field and laboratory observations revealed no copulation among individuals. All specimens conformed to the original description but demonstrated variability that extended across two recognized genera, Cyzicus and Caenestheriella.

AN ATTEMPT TO DETECT PYGANODON FRAGILIS (MOLLUSCA: UNIONIDAE) IN MAINE

Historic information, museum collections, and the shells and stomach anatomy of Pyganodon collected from Maine were compared in order to draw conclusions on the occurrence or absence of P. fragilis (Newfoundland floater) in Maine. Stomach anatomy did not differentiate among the Pyganodon specimens, although a distinction in the rightside sorting area was made be- tween P. cataracta (eastern floater) and Anodonta implicata (alewife floater). Coloration of the periostracum was variable, was determined to be closely associated with environmental conditions, and was not diagnostic among P. cataracta populations. Examination of historic museum specimens, specifically beak sculpture, indicates that Maine P. cataracta was previously misidentified as P. fragilis. This suggests that based on adult morphology, P. fragilis has yet to be found in Maine.

On some larger turbellarian worms (Platyhelminthes) living in temporary fresh waters of Southern New England

During a survey of temporary fresh waters in Hampshire and Franklin Counties, Massachusetts, in 1988, 1989, and 1990, 10 species of larger turbellarian flatworms were collected. Two species of Lecithoepitheliata, Prorhynchus stagnalis and Geocentrophora applanata, are recorded for the first time from southern New England. The triclad species Hymanella retenouva and Phagocata velata are widespread in the region. Bothrioplana semperi, a proseriate poorly known in North America, was recorded and examination of its anatomy revealed no differences from populations found elsewhere. The less well known neorhabdocoel families Dalyellidae and Typhloplanidae are represented by one and four species, respectively. Expanded descriptions of three species of Typhloplanidae, Bothromesostoma macroprostatum, Mesostoma columbianum, and M. curvipenis, all unknown since their original descriptions, are provided.

Macrobdella sestertia (Hirudinea: Hirudinidae) in Maine and a Key to the Hirudiniform Leeches of Maine

Macrobdella sestertia, a large rare leech, is reported from Maine for the first time. Prior to the Maine specimen, the species was known only from four specimens collected in Massachusetts. Currently, a total of four hirudiniform leech species, including the common but previously unreported Haemopis marmorata, are known from the state and are included in a key to hirudiniform species of Maine.