Drake's Island Research Articles

Development and Decline of a Silurian Stromatolite Reef Complex, Glacier Bay National Park, Alaska

Abstract In Glacier Bay, Alaska, Silurian limestones record the development and demise of a stromatolite reef complex in the Alexander terrane. These microbial deposits are of regional and paleontological significance because they contain paleogeographically distinctive biotas and yield important insights into Phanerozoic stromatolites that inhabited normal-marine subtidal environments. Willoughby limestones exposed on Drake Island reveal that stromatolite growth at the platform margin influenced platform dynamics with the protection of peritidal and lagoonal habitats behind a reef-fringed rim, which experienced early lithification by the precipitation of synsedimentary marine cements. Relatively low-energy subtidal conditions in a restricted, shallow-marine lagoon are implied by the peloidal and mollusk-rich wackestones, packstones, and grainstones. At the platform margin, stromatolite boundstones and cementstones capped a reef-like mound by forming a thick microbial-cement crust on a core of outer lagoo...

Notes On molluscan meiofauna from Plymouth

Preliminary examination of marine meiofauna from the Plymouth area, especially on mesopsammic representatives, resulted in the finding of several typically interstitial Mollusca. Among them, Caecum glabrum, Hedylopsis spiculifera, and Philinoglossa praelongata were recorded live for the first time in the area. This is also the first record of Ph. praelongata outside the Mediterranean Sea.During a short stay at the Marine Biological Association Laboratory some preliminary studies on meiofauna were made. To obtain information especially about the interstitial fauna of marine sand, three typical samples of coarse sediment from different positions were examined.Sample A: Plymouth Sound, Outer Cawsand Bay, Queens Ground, 50°20' 03“ N, 4° 10' 27” W; ca. 6 fathoms (=11 m); coarse sand, about 6 1 examined (14 September 1982).Sample B: Plymouth Sound, southwest of Drake Island, 50° 21' 06“ N, 4° 09' 50” W; ca. 7 fathoms (= 13 m); coarse shell-sand, about 1 1 examined (15 September 1982).Sample C: outer Plymouth Sound, 50° 18' 51“ N, 4° 10' 30” W; ca. 12 fathoms (– 22 m); fine gravel, about 1 1 examined (15 September 1982).In this contribution only the gastropods are dealt with; other meiofauna will be treated ina later communication. The sole previous report of mesopsammic fauna from the Plymouth area is that of Spooner (1959). He examined two samples, one of which (Plymouth Sound) was taken fairlyclose to the above sample A, about 18“ more to the West at 4–5–5–5 fathoms (8–10 m; G. R. Forster, personal communication).

Drake's Island of Thieves. Ethnological Sleuthing.

Drake's Island of Thieves. Ethnological Sleuthing.

Cryptic polymorphism in the cirratulid polychaete,Cirriformia tentaculata

Investigations showed that populations ofCirriformia tentaculata(Montagu) at Plymouth, Coverack and Salcombe produce both free-swimming and demersal larvae from single egg batches. The proportion of free-swimming to demersal larvae varies from one brood to another but is constant in different cultures from a single brood. Control of the proportion in which the two behavioural types are produced appears to be genotypic and not phenotypic. The larval types could not be separated morphologically but additional evidence for the existence of polymorphism in the species was provided by the variation of esterase pattern between adults. The population that existed in Southampton water previous to the winter of 1962/63 and which produced only demersal larvae was probably genetically isolated from other populations of the worm and showed behaviour atypical of the species as a whole.IntroductionSince the publication of a note reporting behavioural differences existing between the larval stages ofCirriformia tentaculata(Montagu) from Southampton Water and from Plymouth Sound (George, 1963), continuing investigations have shed more light on the problem. Observation of the Southampton population from 1959 to 1962 showed that demersal larvae were produced throughout the breeding season, from May to September (George, 1964a), whereas Wilson (1936) found that a population from Drake's Island, Plymouth Sound, produced a free-swimming larval stage in July of 1928 and 1933. It is known that some species of polychaete produce pelagic and non-pelagic forms according to the time of year (Mesnil & Caullery, 1917; Thorson, 1946). The Plymouth population was therefore re-examined to determine whether free-swimming larvae were produced during the entire breeding season.

Behavioural Differences between the Larval Stages of Cirriformia tentaculata (Montagu) from Drake's Island (Plymouth Sound) and from Southampton Water

A THREE-YEAR investigation into the ecology of the cirratulid worm, Cirriformia tentaculata (Montagu), occurring on an inter-tidal mud-flat in Southampton Water, failed to reveal any trace of pelagic larval stages. These free-swimming stages have been shown by Wilson1 to exist in a population of worms from Drake's Island.

Styela mammiculata n.sp., a new species of ascidian from the Plymouth area

Styela mammiculata n.sp. is based on four specimens collected in the Plymouth area during the summer of 1953. The most noticeable external feature is the extensive mammillation of the test. The mammillae are much smaller than those of Phallusia mammillata and deserve to be called rather ‘mammiculae’.Of the four specimens, two were taken from Drake's Island buoy (National Grid Reference, 20/4753)m Plymouth Sound, growing about half a metre below the water line, and two from the oyster bed of the Lynher river estuary, near Antony Ferry (National Grid Reference, 20/4257), growing about 12 m. below low-tide mark attached to oyster shells. The largest specimen was from the latter locality and measured III mm. long in the contracted, fixed condi- tion. The smallest, from Drake's Island buoy, was 54 mm. long.

Cercaria Reesi N.Sp., A New Furcocercous Larva From Plymouth

A new longifurcous, pharyngeate, distome cercaria has been found to develop in the marine bivalves Hiatella arctica (L.) and H. striata Fleuriau. This larva was present in 12 of 200 specimens of H. arctica collected from Drake's Island during the summer months (May-August) of 1952,.while the same parasite was found in 15 of 100 specimens of the limestone borer, H. striata, dredged from Plymouth Sound during June and July of the same year.

The Larval Stages of Portumnus (Crustacea Brachyura) with Notes On Some Other Genera

Two species of Portumnus occur in the Plymouth area, P. biguttatus (Risso) and P. latipes (Pennant). P. biguttatus was the only species recorded when the old fauna list of Plymouth was published (1904), but since then it is known that P. latipes is very common in certain sandy areas (see Plymouth Marine Fauna, 1931), far commoner than P. biguttatus.P. biguttatus is rare and has not been seen since 1906. It was first found by W. Garstang and R. Todd on Drake's Island in Plymouth Sound, burrowing in fine gravel (1905), and two specimens, and are recorded from a sandy patch from the north-east corner of Drake's Island. A female in berry was recorded from the same locality by R. Todd, and L. R. Crawshay dredged one in Cawsand Bay in 1906. Apparently the eggs were not hatched out and the zoea of this species is unknown. In August 1902 R. Gurney obtained a megalopa in the plankton and from it secured the first crab stage. He describes the megalopa as being intensely blue. The cast skin of the megalopa and the crab obtained from it (Fig. 3a-c), which he kindly handed to me, are described in my paper of 1928 (Lebour, 1928c, p. 518, pl. viii, figs. 1–3). There is no reason to doubt the accuracy of the determination, especially because, as shown below, corresponding stages of P. latipes as well as the zoeae are now known and are very distinct, differing considerably from those of P. biguttatus.

Studies onPolystomellaLamarck (Foraminifera)

Part I. After a brief statement of the present unsatisfactory position regarding the life history ofPolystomella crispa, an account is given of experiments with various fixatives onP. crispa, collected near Drake's Island, Plymouth. A method is described for the cultivation ofPolystomellain diatom cultures, especially withNavicula muticavar., with which a flagellate (Bodosp.) was constantly present. The identification of individual Foraminifera, and determination of growth, were often possible by some irregularity in the shell, or by noting the attachment of one or more stalked egg cocoons of an unknown turbellarian worm. The feeding ofPolystomellaon diatoms seized by the pseudopodia outside the shell is described; the structures previously taken for ingested algal cells inside the shell are shown to be foraminal plugs (‘bouchons’ of le Calvez) which are discarded from time to time and thrown out of the shell along with the excretory granules (xanthosomes), mostly via the canal system.Part II. Notes are given on the microspheric form and its reproduction, through the spring and summer, by schizogony. The rearing of two broods in laboratory cultures is described, with an account of the formation of a new chamber to the shell. It is concluded that a complete life cycle consisting of one microspheric and one megalospheric phase occupies a period of about two years.Part III. Sporulation of the megalospheric form is described as seen during life; and various factors are discussed which might affect the process. The relatively small size of the reproducingPolystomellawith which Lister worked is ascribed to their having lived under less favourable conditions. From a study of stained preparations, certain details are added concerning the opening up of the shell, presumably to facilitate the eventual escape of the flagellate swarm spores; also concerning the accompanying cytoplasmic and nuclear changes. Some account is given of the form and structure of the swarm spores, both alive and in permanent preparations. Experiments are described which constitute an attempt to carry the life cycle beyond the stage of sporulation. They are so far unsuccessful, with one possible exception, under all the various experimental conditions which are briefly discussed in their turn.

Further Observations on Marine Ciliates Living in the Laboratory Tanks at Plymouth.

Alwaysto be found in Drake's Island Tank.* Very abundant during the summer, but diminishing innumber during the winter months. It has been described by O. MÜller (22), Ehrenberg (6), Stein (31), Dujardin (5), Claparede and Lachmann (3), under various names, but their descriptions may be regarded as only of historic interest. The later observations of Gruber (13), Cohn (4), and Entz (8) aremore detailed, and Lebedew (17) has given the fullest account of the animal. Kent (16), Biitschli (1), and SchewiakofE (27) have only short notices.

Some Marine Ciliates Living in the Laboratory Tanks at Plymouth, with a description of a New Species,Holophrya coronata.

The Ciliates described in this paper were mostly found living in the tanks at the Plymouth Laboratory, which are supplied with a constant circulation of sea-water from two large storage reservoirs. Most of them came from a large shallow tank standing in front of a south window, which is referred to in the paper as “Drake's Island Tank.”

IV.—Drake's Island, Plymouth

The main feature of the geology of Drake's Island is the association of volcanic rocks with marine limestone of Mid-Devonian age. The Geological Survey memoir by Mr. W. A. E. Ussher attributes the discovery of the volcanic rocks to Mr. R. N. Worth. Mr. Ussher leaves their precise nature, “whether lavas or tuffs,” somewhat in doubt, but states that they are “most certainly contemporaneous”. As a matter of fact both lava and tuff occur, and are definitely distinguishable.

Contributions to Marine Bionomics: III. The Systematic Features, Habits, and Respiratory Phenomena of Portumnus nasutus (Latreille)

The crab whose habits I now describe has not previously been recorded as an inhabitant of British seas. I found two specimens, both male, imbedded in a patch of coarse shell sand on the south side of Drake's Island at low water, spring tides: one on August 11th, 1896, and the other on the following day.

Notes and Memoranda

On the Occurrence of the Nudibranch Hancockia at Plymouth.—I am glad to be able to record a second English specimen of this interesting form. It was dredged, apparently on Delesseria, in Plymouth Sound, about halfway between Drake's Island and the west end of the Breakwater, on August 20th, 1891.