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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Results

Sponges collected by the Dutch Polar Expedition 1882-83

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The following 11 species were identified in the Varna collection:

LIST: TYPE 5

One new species was detected in the material, which is described below. The other species are treated in the Appendix. Since most of the species were already described by Levinsen (1887) on the basis of the Dijmphna material that was collected in the same area in the same period, I provide summarized descriptions and measurements in the Appendix, including SEM images of the spicules of all the collected species of the Dutch Polar Expedition as a contribution to the morphological information on Kara Sea sponges.

Systematic description of a species new to science

Class Demospongiae

Order Poecilosclerida

Family Cladorhizidae

Genus Lycopodina Lundbeck, 1905

Lycopodina ruijsi sp. nov. (Figs 3a-g)
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Fig. 3. Lycopodina ruijsi sp. nov., holotype ZMA Por. 01012, a habitus (scale bar 1 cm); b-g SEM images of spicules; b longest style, b1 details of apices of longest style; c shorter style, c1 details of apices of shorter style; d microstyle; e large anisochela; f small anisochela; g forceps.

Holotype. ZMA Por. 01012, Russia, Kara Sea, Varna Expedition, locality not noted on the available labels, depth between 75 and 170 m, coll. J.M. Ruijs, 1882-1883; label text: ‘Esperia spec. Varna-Exp. 1882/83, O. Schmidt det.’.

Additional material (not type material). ZMA Por. 15404, Russia, Kara Sea, Varna Expedition, locality not noted on the available labels, depth between 75 and 170 m, coll. J.M. Ruijs, 1882-1883; label text: ‘Clador­hiza spec.’, but there is no further text and no identifier mentioned.

Description. The specimens, dark brown in alcohol, consist of a narrow fleshy stalk-like lower part and a broader blade-like upper part. The holotype (Fig. 3a) is 50 mm long, with the stalk 38 × 5 mm and the main body 12 × 8 mm. The second sample is now broken into three tiny fragments of undetermined shape.

Skeleton. The thinner lower part has a skeleton of loosely packed aligned spicules, the main body has a largely confused skeleton of intercrossing spicule tracts.

Spicules. (Figs 3b-g) Styles, microstyles/strongyles, anisochelae and forcipes.

Styles in a large size range, with overlapping larger (Figs 3b, b1) and smaller (Figs 3c, c1) styles, but not divisible in size categories, overall range 390-875 × 9-11 µm.

Microstyles (Fig. 3d) or microstrongyles, usually with one end with a slight tyle, curved more or less strongly, 63-145 × 2.5­7 µm.

Anisochelae, shaped like the usual Lycopodina chelae, with the shaft uncovered by the upper alae for a shorter or larger stretch, usually the naked shaft is less than 20% of the length of the alae, in two clear non-overlapping size categories, larger (Fig. 3e) with lengths 23-29 µm (average 26.4) and smaller (Fig. 3f) with lengths 11-21 µm (average 15.9).

Forcipes (Fig. 3g), common, with straight legs that are only slightly expanding, with swollen tips, legs 24-45 µm.

Etymology. Named after J.M. Ruijs in recognition of his tireless efforts to collect bottom fauna from a drifting ice floe under extreme polar conditions.

Remarks. The new species belongs to the newly revived genus Lycopodina Lundbeck, 1905 because of its possession of forceps microscleres in combination with the spiculation and architecture of the genus Asbestopluma. Hestetun et al. (2015) established on morphological and molecular evidence that Lundbeck’s subgenus Asbestopluma (Lycopodina) deserves recognition at the genus level.

The two specimens differ somewhat in sizes of the spicules, with the holotype having generally slightly longer styles, forcipes, and both categories of anisochelae. The microstyles of ZMA Por. 15404 are more often strongyles and are frequently much more strongly curved than those of the holotype. The anisochelae of 15404 have a longer stretch of shaft visible (resembling those of L. infundibulum), than those of the holotype. For the time being, this is interpreted as variability, but in view of the scanty material and the observed differences I refrain from assigning paratype status to ZMA Por. 15404. Future studies might demonstrate that the two specimens belong to closely related but different species.

The spicule complement is generally similar to that of Lycopodina robusta (Levinsen, 1887) (described below in Appendix), but that species has a different habitus with ‘grooved’ side-branches, and there are no microstyles and only a single category of anisochelae. The latter have their shafts covered entirely by the lateral alae in L. robusta, in contrast with those of the present species.

Two related cladorhizid species occurring in the Arctic region possess two sizes of anisochelae, viz. Asbestopluma (A.) pennatula (Schmidt, 1875) [(with junior synonym Asbestopluma bihamatifera (Carter, 1876) (originally as Esperia cupressiformis var. biha­matifera, see also description in Lundbeck, 1905, p. 51)] and Asbestopluma (A.) furcata Lundbeck, 1905 (p. 54). Both differ clearly from the new species in having sigmancistras, and the larger category of anisochelae in the two species is twice as large (respectively 48-63 µm and 44-54 µm) as that of the present species. The habitus of A. (A.) pennatula is pennate, that of A. (A.) furcata is dichotomously arborescent, unlike the new species.

For further information on Kara Sea cladorhizids collected by the Dutch Polar Expediton 1882-1883 see Appendix.

Comparison with previous studies on sponges of the Kara Sea

The Dijmphna sponges of the Kara Sea, collected at the same time and in the same area by Th. Holm (cf. Bergh et al. 1887), were studied by Levinsen (1887). The results of his study are presented in Table 2, left hand column, with currently accepted names given in the right hand column (from the World Porifera Database (WPD), cf. Van Soest et al., 2015). Also in the latter, asterisks indicate whether the species was also collected by the Dutch Polar Expedition. The collection consisted of specimens of 20 sponge species, several of which were collected outside the Kara Sea (deduced from the shallow depth they were collected). Next to collections made by the ‘Dijmphna’ from the drifting ice floe, there were also some shallow-water sponges collected along the way travelling to and leaving from the Kara Sea. Unfortunately, Levinsen (1887) provided only depth data, so the validity of their Kara Sea occurrence is somewhat in doubt because the precise localities are not given. As could be expected, there is a great resemblance in the sponges collected by the Dutch and Danish expeditions, with 9 out of 11 species of the Dutch collection also represented in the Danish collection. The two species not reported by Levinsen, Tetilla sandalina and Lycopodina ruijsi sp. nov. might easily be hiding in the Danish collection under the 13 reported specimens of Tetilla polyura and among the Esperella cupressiformis ‘varieties’ (respectively 27 and 20 specimens of both varieties).

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Table 2. Porifera obtained by the ‘Dijmphna’ Expedition to the Kara Sea, collected by Th. Holm, reported and described by G.M.R. Levinsen (1887) (left hand column) with the names corrected on the basis of the present study, and the World Porifera Database (Van Soest et al., 2015, consulted on May 30, 2015) (right hand column). The order of the names follows the treatment in Levinsen’s study. Names with an asterisk were also identified in the present collection.

Further reports on sponges from the Kara Sea are those of Fristedt (1887, 4 species), Hentschel (1929, 3 species), Rezvoi (1924, 12 species), Rezvoi (1931, 6 species), and especially Koltun (1959, 1966, 49 species). The latter author also partially included the results of the previous authors. Lundbeck (1905) renamed Esperella picea sensu Levinsen as Iophon frigidus, and this name is so far retained in the WPD awaiting reexamination. It is assumed here that Iophon frigidus is a junior synonym of Iophon piceum. The reported Kara Sea sponge fauna is here assembled in Table: in the left part the currently accepted names, which number 60 species and in the right part the original combinations and synonyms found in the original studies.

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Table 3. Sponges reported from the Kara Sea. The first four columns provide the identities of 60 species under the currently accepted systematics with as references either the World Porifera Database (Van Soest et al., 2015, consulted on May 30, 2015) or the present study. The next three columns provide one or more original genus and species names for the Kara Sea species and their original references.

Almost all of the records of sponges were obtained from more eastern and northern parts of the Kara Sea, which are deeper and/or from inshore localities or from the mouth of the Yenisei. The sponges of the southwestern Kara Sea, where the Dutch Polar Expedition and the ‘Dijmphna’ collected their specimens, are known almost exclusively from these 19th century research activities.