Encounter with a Sea Flea Ampithoeprolata in Port Melbourne.
When we lift up stranded seaweed or sea-grass, we often see amphipods jumping in all directions. Similarly, if we move the damp leaf litter in the garden we are likely to come across the brown Talitrid amphipods Arcitalitrus sylvaticus (Haswell 1879) lurching to get back into the damp conditions necessary for their gills to absorb oxygen.
When the tide is low and a high pressure cell above makes the sea as smooth as satin, I visit the seashore to sieve for amphipods. Such times are ideal as there is no wind to ruffle the water in the look box', which would make it impossible to see features of amphipods and make photography difficult.
In 2009,1 encountered a large amphipod (Fig. 1) in Greenwich Bay, Newport, Victoria. As I looked at it through the microscope I nicknamed it Mr and Mrs Bigskirts on account of the large, deep coxal plates along the side of the body (Fig. 2). These plates are like shields protecting the proximal/upper parts of the two pairs of claws and five pairs of legs, or, as in amphipodal parlance, gnathopods and pereopods respectively. At that time, available literature provided no match fitting the description of Ampithoe prolata.
Since then, I acquired the scientific description of Ampithoe prolata (Hughes and Peart 2013) which belongs to the family Ampithoidae, and I have encountered an ovigerous female of the species deeply encrusted with 40-odd small brown eggs in seagrass in Hobsons Bay off Williamstown.
On 14 July 2018, a neighbour and I took advantage of ideal weather conditions and visited Port Melbourne. As we examined a clump of blue mussel Mytilus galloprovincialis planulatus stranded at the high tide mark by recent heavy seas, I observed the rear end and leg of a crustacean in the dark murky recess of a dead bivalve, Barbatia pistachio, attached to the mussels by a byssus thread. I dislodged a large amphipod from the bivalve using a soft brush and placed it into a glass look box. The amphipod was about 16 mm long and had a clump of milky brown fuzz adhering to the underside of her thorax. I realised with surprise that this fuzz was about 40 newly hatched juveniles (Fig. 3). Some of them measured about 1 mm in length and swam into the water column where I trapped them for later photography under a compound microscope. The species was readily identifiable as Ampithoe prolata by the characteristic pattern of brown spots and unpigmented blotches (Fig. 4). The species name refers to the elongate carpus of gnathopod 1 in the female (Fig. 5) and the especially long carpus in the male (Fig. 6).
After taking a few pictures, the adult female was returned to the water along with the mussel clump to which she was attached in the hope she and her young would survive.
In my experience so far, Ampithoe prolata is found in Heterozostera nigricaulis in sheltered areas in both muddy and not so muddy places such as Brighton, Williamstown, Newport and Port Melbourne, Victoria.
Hughes LE and Peart RA (2013) New species and records of Ampithoidae (Peracarida: Amphipoda) from Australian Waters. Zootaxa 3719, 1-102.
17 Davey Avenue Oakleigh, Victoria 3166
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|Title Annotation:||Naturalist Note; Port Melbourne, Australia|
|Publication:||The Victorian Naturalist|
|Date:||Feb 1, 2019|
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