Studies on the Biology, Distribution and Ecology of New Zealand Teredinidae

Abstract

SECTION 1. Published works concerning teredinids in New Zealand are reviewed and briefly discussed. Early identifications of Bankia australis were checked and in some cases were found to have been incorrect identifications of Bankia tanzensis. The presence of five species of teredinids, namely Bankia australis, Bankia tanzensis Lyrodus pedicellatus, Lyrodus medilobata and Nototeredo edax has been reported in New Zealand. The taxonomy of these five species is briefly reviewed, and a key to their identification in New Zealand is presented together with a discussion of the main diagnostic features of each species. The identification of juvenile specimens is discussed, particularly from the point of view of early pallet development. The early pallets of each species are described. SECTION 2. Reports of the occurrence of fossil teredinids in New Zealand are reviewed, and most of the described species are shown to be nomina dubia, with the exception of Bankia turneri Powell and Bartrum, which is redescribed. An unnamed fossil species of Bankia from the Upper Cretaceous of the Wairarapa is described. This species is very similar to the Recent Bankia tanzensis. The occurrence of fossil species of Bankia throuqhout the world is reviewed. SECTION 3. Previous studies and reports on the general distribution of teredinids in New Zealand waters were complemented with test-block studies and collections from other sources such as mangroves. The general geographical distribution of each species seems to be correlated primarily with water temperatures. Bankia australis was recorded from around the North Island and the northern parts of the south Island. B. tanzensis was recorded from around the South Island and the southern half of the North Island. Lyrodus pedicellatus was recorded from approximately the same range as B. australis, and L. medilobata was found only in the north west of the North Island between Tauranga and Whangaroa. Nototeredo edax was recorded from scattered harbours around the North Island. The local distribution of teredinids in Pelorus and Kenepuru Sounds, Marlborough, in Wellington Harbour, and in the northern Kaipara Harbour is described, and the distribution of the species in relation to temperature and salinity variations in these areas is discussed. Records of Bankia tanzensis from deep water (more than 50 metres deep) around New Zealand are reported and discussed. The dispersal of teredinids in relation to the observed distribution patterns around New Zealand, and the presence of Teredora princesae in driftwood in New Zealand are reviewed. The absence of Teredo navalis from collections around New Zealand is noted. SECTION 4. The sexual phases of Bankia tanzensis in Wellington Harbour are described The seasonal occurrence of the various phases was studied in an unsuccessful attempt to determine spawning times. B. tanzensis appears to be a protandrous hermaphrodite like all of the other species of Bankia which have been studied elsewhere. SECTION 5. The distinguishing features of teredinid larvae are reviewed, and the early development of the larvae of Bankia tanzensis and B. australis is described, along with the larvae of Lyrodus pedicellatus and L medilobata collected from the gill chambers of the parent animals. Teredinid larvae from the plankton of the Bay of Islands and Wellington, tentatively identified as Bankia australis and B. tanzensis respectively, are described. Some general differences between Bankia and Lyrodus larvae are discussed, but the larvae of the species within these genera within New Zealand cannot be distinguished with any certainty. The seasonal occurrence of teredinid larvae in the plankton of the Bay of Islands and Wellington Harbour is described in relation to Water temperatures and the seasonal settlement on test-brocks, particularly in Wellington. Some preliminary observations on the ecology of the larvae, including vertical distribution and diel and tidal cycles, are reported. SECTION 6. The seasonal settlement of teredinids in Tauranga End Wellington Harbours is described and discussed. Settlement seasons seem to be defined primarily by water temperatures, although salinity may be of some importance in Tauranga Harbour. Bankia australis, Lyrodus pedicellatus, L. medilobata and Nototeredo edax all settled most abundantly in the summer months in Tauranqa Harbour. B. tanzensis was abundant in both winter and summer in Tauranga Harbour (at least in 1971 - 72), but in Wellington it settled predominantly in winter. Annual variations in the pattern of seasonal settlement are discussed and found to depend only partly on temperature variations. The settlement of teredinids in the intertidal zone at three localities in the North Island is described. Most of the species studied are found to be capable of settling and surviving at levels up to Mean Sea Level. The occurrence of teredinids in mangroves is reported, and soma interesting differences in the species settling on intertidal test-blocks and on mangroves in Tauranga Harbour are noted. Subtidal vertical settlement at Mt. Maunganui and at Evans Bay, Wellington Harbour is fund to be, in general, greatest near the mudline. Deviations from this pattern, particularly by Bankia spp. in Tauranga Harbour, can probably be explained in terms of the time of settlement of the teredinids in relation to each other and to the development of fouling communities on the test-blocks. Simple experiments to determine the significance of "conditioning" of wood surfaces prior to successful settlement of teredinids, and the significance of surface texture in settlement are described. Bankia tanzensis larvae were found to be able to settle successfully on wood which had been immersed for only six days, although, in general, longer periods of immersion seem to be required for most of the larvae. Rough textured wood was more suitable for settlement of teredinids than which had been planed smooth. SECTION 7. General studies on growth rate of teredinids are reviewed, and some of the factors which are known to influence growth rate are discussed. The rate of growth of B. tanzensis in test blocks in Wellington Harbour is described, and compared with that determined by Ralph and Hurley (1952) in Wellington Harbour during 1949-50. Mean daily increases in tunnel length of the order of 2 - 3 mm per day were recorded. A loqarithmic relationship between tunnel length and maximum tunnel diameter of B. tanzensis in Wellington Harbour is described.