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Arenicolidae Family Arenicolidae (arenicolid/lug-worm)
Scolecida (Annelida: Polychaeta)
About Family Arenicolidae polychaetes in New Zealand.  
How to recognise the family: Very large, plump polychaetes that burrow deep in the sand and cycle large quantities of it through their bodies. The prostomium is inconspicuous. A balloon-like proboscis may protrude from the mouth. Segments are multi-annulated and warty. The mid-body has red branching gills behind the notopodia, and there is an unsegmented thinner posterior region, which may be sacrificed to attacks by wading birds and fish. Notochaetae are capillaries, and neurochaetae are hooks without hoods. Adult size: To 350 mm long and 30 mm diameter.
How to recognise the New Zealand genera: Abarenicola is the only New Zealand genus. It is separated in part from Arenicola by having more than one pair of oesophageal sacs.
Quick pick shore species: The two New Zealand Abarenicola species always have 19 chaetigers, with branched gills beginning as a small pair on chaetiger seven. The larger, darker Abarenicola affinis (Ashworth, 1903) has the parapodial annuli on the first three chaetigers enlarged and conspicuous compared to the adjoining annuli. The smaller Abarenicola deviaWells, 1963 has annuli of the first three chaetigers all similar sized. In life it is an attractive green-yellow colour with bright red gills and a yellow tail section. Both Abarenicola species were formerly treated as geographic subspecies, here treated as full species. There are no rocky shore species.
Possible misidentifications: None. However, the surface sign faecal coils can be confusable with that of the hemichordate Balanoglossus australiensis.
Distributions, lifestyle, and habitat: Lower shore, burrowing in medium to fine, sheltered sands and discharging a pile of sandy coils on the surface. Abarenicola affinis thrives in organically enriched sediments, whereas Abarenicola devia prefers the cleaner, slightly coarser sand of partly sheltered beaches, including sand pockets on otherwise rocky shores. The once well-known Abarenicola affinis population of Wellington's Petone Beach has dwindled greatly in number since the closure of an abattoir outfall, and now Otago Harbour may have New Zealand's biggest population of lugworms. Abarenicola affinis is the large endemic species on the three main islands and Chatham Island. The smaller Abarenicola devia also occurs in Australia, but here is not yet known outside of the southern North Island, and a further species Abarenicola insularum Wells, 1963 occurs on the Auckland and Campbell Islands. The famous and much researched European lugworm, Arenicola marina (Linnaeus, 1758), is sufficiently numerous on vast North Sea coast mudflats that it supports an annual commercial harvest of tens of million individuals for fish bait. In New Zealand Abarenicola colonies are relatively infrequent.
Abundance: Uncommon but may be locally abundant in small colonies.
Taxonomic note: Here the subspecies of Wells are treated as full species - Abarenicola affinis (formerly as Abarenicola affinis affinis) and Abarenicola devia (formerly as Abarenicola assimilis devia). Subantarctic Abarenicola insularum was formerly Abarenicola assimilis insularum. Wells' text is somewhat wordy, with long comparisons not conveniently separated into species, though he does give very brief diagnoses.
References: (Wear 1962: p116-128, f1-3), (Wells 1963: p121-159, f1-10, Pl-5).
(Full citations at Family pages literature cited list.)

Species in the guide: Rock Species: None for this family.
Sand Species: Abarenicola affinis | Abarenicola devia
Shell Species: None for this family.

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Last modified by G. Read, 25/07/2004    (dd/mm/yy)