Contributions to Zoology, 85 (3) – 2016Rob W. M. van Soest: Sponge-collecting from a drifting ice floe: the Porifera obtained in the Kara Sea by the Dutch Polar Expedition 1882-83

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Material and methods

The specimens described here are a small part of the collections made in situ by J.M. Ruijs. A total of 30 specimens survived until today, from an estimated amount of at least 200 specimens obtained at 55 of the 83 stations (Table 1). Whether the loss of specimens was intentional or not is unclear from the reports of the expedition. However, due to the difficulty of transporting the soft, easily damaged material from the drifting ice floe to the Zoological Museum of Amsterdam, it is a small miracle any sponge specimen arrived there. Also for that reason, the surviving specimens are poorly documented: of the 30 specimens only 10 had sufficient information on the label to deduce the exact locality (coordinates, date, depth, bottom conditions, collecting gear), the remaining specimens lacked this label information. They are assumed to have been collected at one of the stations indicated in Ruijs (1887: 15-26) as having one or more sponges in the catch (see Table 1). Depth for those specimens is summarized below as between 75 and 170 m, based on the information in the station list. The position and dates of all stations sampled inside the Kara Sea are depicted in Fig. 1.

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Table 1. Stations of the Dutch Polar (‘Varna’) Expedition which yielded sponges, as noted by J.M. Ruijs (from Ruijs, 1887). Collecting gear indicated by the French ‘faubertage’ involved the use of so called swabs made of hemp in which spiny or wiry bottom organisms become tangled (see Tendal, 2002). The ‘large dredge’ was rectangular and measured 40 × 70 cm. Bold printed rows indicate stations that were mentioned on one or more of the labels of the 30 specimens that survived from the collecting activities of the Dutch Polar Expedition.

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Fig. 1. Map showing course and stations of the Dutch Polar (‘Varna’) Expedition 1882-83 in the southwest Kara Sea (from Snellen and Ekama, 1910). Inset map of the Kara Sea and environs, made by Norman Einstein, November 2005, taken from Wikipedia (http://commons.wikimedia.org/wiki/File:Kara_Sea_map.png) under the GNU Free Documentation License.

The collecting methods varied along with the events that occurred during the expedition. Specimens that survived were all obtained by collecting from the ice floe, all from the southern and western parts of the Kara Sea (only a few samples were obtained west of Yugor Strait and the sponges did not survive). The ice conditions were such that even when the ‘Varna’ was still afloat no movements of the ship were possible. This meant that holes or squares had to be sawn in the thinner parts of the surrounding ice in order to be able to lower the collecting gear into the water. The gear consisted to begin with of larger and smaller rectangular and semi-circular dredges, drifting nets and collecting swabs (‘faubertage’) (see Tendal, 2002). During most of the winter period, when the overwintering accommodation had been erected (Fig. 2), all collected material had to be quickly brought inside as the catch became frozen solid more or less immediately after it was brought up. After several ice crushes, which caused loss of dredge nets, the only remaining gear was the large 40 × 70 cm rectangular dredge (Fig. 2 left), and a number of swabs. Most of the material was collected using these two types of gear.

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Fig. 2. The prefabricated house in which the participants of the Dutch Polar Expedition 1882-83 spent most of their overwintering period on the ice floe drifting around in the Kara Sea. Photo taken by H. Ekama on 13 July 1883 (from Snellen, 1887).

Dredging from drifting ice needed its own improvised methodology. Where normal dredging from a ship means a bottom time of 10-30 minutes, the rate of movement of the ice was so slow, that for the dredge or the swabs to be effective periods of more than 20 hours were no exception. At times, drift was minimal and the dredge so heavy that it ploughed deeply into the soft bottom, with the result that it arrived at the surface filled with ‘grey loam’ that had to be sieved patiently (and inside the living quarters!).

Material was sorted at the locality on the ice, preserved in 60-70% ethanol, and stored in tins, glass tubes and glass bottles, the latter probably a.o. containing the sponges. Delivered in Amsterdam, the sponges remained unidentified, until the Norwegian spongologist E. Arnesen (1867-1928) arrived for a four months’ work visit to what later became the Zoological Museum of the University of Amsterdam (ZMA) in 1903 by invitation of the director Professor Max Weber. She provisionally identified most specimens, except for ZMA Por. 01012 and 02382, which according to the label were identified by O. Schmidt (1823-1886). However, this cannot be concluded with certainty, because his characteristic handwriting is not on the labels, and Schmidt’s biography (Desqueyroux-Faúndez and Stone, 1992) makes no mention of any visit to Amsterdam, so briefly before his death in 1886. It is perhaps surprising that the Dutch contemporary spongologist G.C.J. Vosmaer (1854-1916), author of two publications on the sponges of the Barents Sea (adjacent to the Kara Sea) (Vosmaer, 1882, 1885), was apparently not involved in the identification of the Varna sponges, but this is understandable because at that time he was working in Naples (1882-1889).

All specimens are registered in the ZMA collection, now housed in Leiden, and labelled ‘Kara Zee Varna-Exp. 1882/83’, with E. Arnesen’s unpublished names. The specimens were re-identified by the present author and provided with additional new labels bearing the names mentioned below. To make the descriptions and illustrations, below and in the Appendix, thick sections, dissociated spicule slides and SEM preparations were made in the way described in Van Soest et al., (2014). Measurements of spicules are based on 15 spicules of each distinguished type, randomly chosen.