COMMENTS & OBSERVATIONS

Despite the great forecast for boating we opted for a shore dive at Horseshoe Bay as we have not been here since June. It is also the site of our first dive when we moved her approximately 12 months ago.

A very slight swell made for some surge in the shallows at around 2m depth. This made photography challenging as we kept finding small Elysia spp. that burrowed in the turf algae on the rocks at this shallow depth. We continued on north-easterly over the beautiful corals and headed into slightly deeper water and rounded the corner. The water clarity was still milky but we had enough visibility to see each other and hunt slugs. We recorded several species that we have not recorded in this area to date, including 2 specimens that we are calling Goniobranchus cf. splendidus, as the specimens have very dark gill and rhinophore colour. This specimen is similar to that recorded as a rare, temperate species by Coleman, 2008. We were also excited to find another specimen of Cerberilla sp.3, which we first recorded at this site in June. Considering this specimen on both occasions was around 3 mm in length, we consider this to be extremely good luck.

Taxonomic Diversity:
Eight of the eleven species sighted were nudibranchs, with 4 being dorids comprising 1 x phanerobranch (non-retractile gill), 1 x porostome (suctorial feeder),  2 x cryptobranchs (retractable gill) and 4 were cladobranchs comprising 3 x aeolid, 1 x dendronotinid, 0 x arminid. Three x sacoglossans complete the species count. If diet is considered only 3 of the 11 species sighted were spongivores.

Our Historical data:
– We have now completed 9 surveys at this site since we commenced fully recording data here 12/06/2018.
– We have recorded 18 species at this site.
– Although too early to draw any conclusions regarding relative abundance or prevalence of species at this site, the changes over time as we complete more surveys may be interesting. The most regularly recorded species at this site are: Samla bicolor (44%), Gymnodoris citrina (44%), Jorunna funebris (33%) and Gymnodoris sp. 10 (22%) none of which were recorded on this survey.
– All but two of the species (Cerberilla sp. 3 and Tritoniopsis elegans) recorded in this survey have not been recorded by us at this site previously.
– Bulbaeolidia alba, Elysia sp. 30, Elysia sp. 31, Elysia thompsoni, Goniobranchus cf. splendidus and Gymnodoris sp. 28 have not been previously recorded by us in the Whitsundays.
– We have also not recorded either Elysia thompsoni or Goniobranchus cf. splendidus in Australia previously.
– This site last surveyed on 29/06/2023.
(Historical data courtesy of Terry Farr, who extracts it from his comprehensive database.)

Note about Elysia thompsoni: Originally described from Western Australia, where most sightings are recorded, it has also been recorded from the Gulf of Thailand and Milne Bay PNG. Our sighting considerably extends its known range. This find brings to light the fact that the specimen we have been calling Elysia thompsoni on this site up until now is not that species and will now been renamed Elysia sp. 35.

Note about Goniobranchus cf. splendidus: This specimen differs from Goniobranchus splendidus in that the rhinophores and gills are both deep black. It is most similar to an image of a specimen recorded from Byron Bay, and labelled Chromodoris sp., in Nudibranch Encyclopedia, Coleman, 2008, P.143. It is also different from the “tropical specimen” Goniobranchus splendidus, from the Percy Isles, in: Tropical Range Extension for the Temperate, Endemic South-Eastern Australian Nudibranch Goniobranchus splendidus (Angas, 1864), Wilson, Winters & Cheney, 2016.

Guide to Symbols:
+++ New Species
+ First time sighted in Whitsundays
# Most commonly sighted at this site with %

TOTAL SPECIES SIGHTED: 11

DIVE IMAGES GALLERY

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