SALTRIO THEROPOD

In the summer of 1996, Angelo Zanella, an avocational fossil collector and active collaborator at the Museo di Storia Naturale di Milano (MSNM) spotted some intriguing fossil bone sticking out of a large block of rock while hunting for ammonites in the Salnova marble quarry.

The quarry is in the Alpine foothills, at the Swiss–Italian border near Saltrio. Saltrio is about 80 km north of Milan in the province of Varese, Lombardy, Italy.

Zanella reported the bones to the MSNM, which arranged a paleontological expedition to the site. The research was difficult because the explosives used for industrial quarrying had blown up the fossil-bearing layer and had broken it into hundreds of pieces.

The Saltrio quarry has been active since the 15th century as one of the finest sites of marble production, and the “Saltrio Stone” provides high-quality building materials for many famous Italian monuments  — the Scala Opera House in Milan and the Mole Antonelliana in Turin. They actively use dynamite to extract the marble. Great for the workers who are not required to manually break-up the massive pieces. Less so for the fossils. The bones from the Saltrio theropod were blown to bits just prior to Zanella's discovery then had to be pieced back together.

Three years later, after 1,800 h of chemical preparation in the Laboratory of the MSNM, 132 remains were extracted from three main blocks. Although fragmentary, jaw fragments, one tooth, rib remains, pectoral and limb bones were analyzed and found to be that of a large theropod dinosaur.

The Saltrio theropod (MSNM V3664) became popular by the name, Saltriosauro, and so it was reported (Dal Sasso, 2001a) and preliminarily described (Dal Sasso, 2001b, 2004).

Pictured above: selected elements used in the diagnosis of Saltriovenator zanellai n. gen. n. sp. Right humerus in medial (A), frontal (B) and distal (C) views; (D) left scapula, medial view; (E) right scapular glenoid and coracoid, lateral view; (F) furcula, ventral view; tooth, labial (G) and apical (H) views; (I) left humerus, medial view; right second metacarpal in dorsal (J), lateral (L) and distal (N) views; first phalanx of the right second digit in dorsal (K), lateral (M) and proximal (O) views; (P–T) right third digit in proximal, dorsal and lateral views; (U) right distal tarsal IV, proximal view; third right metatarsal in proximal (V) and frontal (X) views; second right metatarsal, proximal (W) and frontal (Y) views; (Z) reconstructed skeleton showing identified elements (red). Abbreviations as in text, asterisks mark autapomorphic traits. Scale bars: 10 cm in (A)–(E), (I), and (U)–(Y); two cm in (F), and (J)–(T); one cm in (G).

Photos by G. Bindellini, C. Dal Sasso and M. Zilioli; drawing by M. Auditore. - https://peerj.com/articles/5976/

ANEMONEFISH NURSERY

Anemonefish colonies usually consist of the reproductive male and female and a few male juveniles, which help tend the colony.

Although multiple males cohabit an environment with a single female, polygamy does not occur and only the adult pair exhibits reproductive behaviour. If the female dies, the social hierarchy shifts with the breeding male exhibiting protandrous sex reversal to become the breeding female.

The largest juvenile then becomes the new breeding male after a period of rapid growth. The existence of protandry in anemonefish may rest on the case that nonbreeders modulate their phenotype in a way that causes breeders to tolerate them. This strategy prevents conflict by reducing competition between males for one female. For example, by purposefully modifying their growth rate to remain small and submissive, the juveniles in a colony present no threat to the fitness of the adult male, thereby protecting themselves from being evicted by the dominant fish.

The reproductive cycle of anemonefish is often correlated with the lunar cycle. Rates of spawning for anemonefish peak around the first and third quarters of the moon. The timing of this spawn means that the eggs hatch around the full moon or new moon periods. One explanation for this lunar clock is that spring tides produce the highest tides during full or new moons. Nocturnal hatching during high tide may reduce predation by allowing for a greater capacity for escape. Namely, the stronger currents and greater water volume during high tide protect the hatchlings by effectively sweeping them to safety. Before spawning, anemonefish exhibit increased rates of anemone and substrate biting, which help prepare and clean the nest for the spawn.

In terms of parental care, male anemonefish are often the caretakers of eggs. Before making the clutch, the parents often clear an oval-shaped clutch varying in diameter for the spawn. Fecundity, or reproductive rate, of the females, usually ranges from 600 to 1500 eggs depending on her size. In contrast to most animal species, the female-only occasionally takes responsibility for the eggs, with males expending most of the time and effort. Male anemonefish care for their eggs by fanning and guarding them for 6 to 10 days until they hatch. In general, eggs develop more rapidly in a clutch when males fan properly, and fanning represents a crucial mechanism of successfully developing eggs.

This suggests that males can control the success of hatching an egg clutch by investing different amounts of time and energy towards the eggs. For example, a male could choose to fan less in times of scarcity or fan more in times of abundance. Furthermore, males display increased alertness when guarding more valuable broods, or eggs in which paternity was guaranteed. Females, though, display generally less preference for parental behavior than males. All these suggest that males have increased parental investment towards the eggs compared to females.

CLOWN FISH: SYMBIOSIS

The colourful wee fellows you see here are Clown Fish. They have an unusual relationship with sea anemones. Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species are recognized: one in the genus Premnas, while the remaining are in the genus Amphiprion.

In the wild, they all form symbiotic mutualisms with sea anemones, each providing benefits to the other.

The individual species are generally highly host-specific, and especially the genera Heteractis and Stichodactyla, and the species Entacmaea quadricolor are frequent anemonefish partners.

The sea anemone protects the anemonefish from predators, as well as providing food through the scraps left from the anemone's meals and occasional dead anemone tentacles, and functions as a safe nest site. In return, the anemonefish defends the anemone from its predators and parasites.

The anemone also picks up nutrients from the anemonefish's excrement. The nitrogen excreted from anemonefish increases the number of algae incorporated into the tissue of their hosts, which aids the anemone in tissue growth and regeneration.

The activity of the anemonefish results in greater water circulation around the sea anemone, and it has been suggested that their bright colouring might lure small fish to the anemone, which then catches them. Studies on anemonefish have found that they alter the flow of water around sea anemone tentacles by certain behaviours and movements such as "wedging" and "switching". Aeration of the host anemone tentacles allows for benefits to the metabolism of both partners, mainly by increasing anemone body size and both anemonefish and anemone respiration.

SEA ANEMONE NURSERY

Sea anemones are familiar inhabitants of rocky shores and coral reefs around the world; other species can be found at very low depths indeed. Most of the soft-bodied anthozoans known as "sea anemones" are classified in the Actinaria.

Most actinarians are sessile; that is, they live attached to rocks or other substrates and do not move, or move only very slowly by contractions of the pedal disk. A number of anemones burrow into sand, and a few can even swim short distances, by bending the column back and forth or by "flapping" their tentacles. In all, there are about 1000 species of sea anemone in the world's oceans.

Sea anemones breed by liberating sperm and eggs through their mouth into the sea. The fertilized eggs develop into planula larvae which, after being planktonic for a while, settle on the seabed and develop directly into juvenile polyps. Sea anemones can also breed asexually, by breaking in half or into smaller pieces which regenerate into polyps.

They are sometimes kept in reef aquariums; the global trade in marine ornamentals is expanding and threatens sea anemone populations in some localities, as the trade depends on collection from the wild. Most Actiniaria do not form hard parts that can be recognized as fossils, but a few fossils of sea anemones do exist; Mackenzia, from the Stephen Formation, Middle Cambrian Burgess Shale of Canada, is the oldest fossil identified as a sea anemone.

Some fossil sea anemones have also been found from the Lower Cambrian of China. The new find lends support to genetic data that suggests anthozoans — anemones, corals, octocorals and their kin — were one the first Cnidarian groups to diversify.

Reference:  Conway Morris, S. (1993). "Ediacaran-like fossils in Cambrian Burgess Shale–type faunas of North America". Palaeontology. 36 (31–0239): 593–635.